Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02215853 1999-OS-04
(First Page)
METHOD AND APPARATUS FOR AUTHENTICATING DOCUMENTS
INCLUDING CURRENCY
This application is a division of Canadian Patent Application 2,184,807, with
an
international filing date of March 8, 1995.
The present invention relates, in general, to document authentication. More
specifically, the present invention relates to an apparatus and method for
authenticating
documents such as currency bills of different denominations and/or from
different
countries by illuminating the documents with ultraviolet light.
Machines that are currently available for simultaneous scanning and counting
of
documents such as paper currency are relatively complex and costly, and
relatively large
in size. The complexity of such machines can also lead to excessive service
and
maintenance requirements. These drawbacks have inhibited more widespread use
of
such machines, particularly in banks and other financial institutions where
space is
limited in areas where the machines are most needed, such as teller areas.
The above drawbacks are particularly difficult to overcome in machines which
offer much-needed features such as the ability to scan bills regardless of
their orientation
CA 02215853 1999-OS-04
24
relative to the machine or to each other, and the ability to authenticate
genuineness
and/or denomination of the bills.
A variety of techniques and apparatus have been used to satisfy the
requirements
of automated currency handling systems. At the lower end of sophistication in
this area
of technology are systems capable of handling only a specific type of
currency, such as a
specific dollar denomination, while rejecting all other types. At the upper
end are
complex systems which are capable of identifying and discriminating among and
automatically counting multiple currency denominations.
Currency discrimination systems typically employ either magnetic sensing or
optical sensing for discriminating among different currency denominations.
Magnetic
sensing is based on detecting the presence or absence of magnetic ink in
portions of
the printed indicia on the currency by using magnetic sensors, usually ferrite
core-
based sensors, and using the detected magnetic signals, after undergoing
analog or
digital processing, as the basis for currency discrimination. A variety of
currency
characteristics can be measured using magnetic sensing. These include
detection of
patterns of changes in magnetic flux, patterns of vertical grid lines in the
portrait area
of bills, the presence of a security thread, total amount of magnetizable
material of a
bill, patterns from sensing the strength of magnetic fields along a bill, and
other
patterns and counts from scanning different portions of the bill such as the
area in
which the denomination is written out.
The more commonly used optical sensing techniques, on the other hand, are
based on detecting and analyzing variations in light reflectance or
transmissivity
characteristics occurring when a currency bill is illuminated and scanned by a
strip of
focused light. The subsequent currency discrimination is based on the
comparison of
sensed optical characteristics with prestored parameters for different
currency
denominations, while accounting for adequate tolerances reflecting differences
among
individual bills of a given denomination. A variety of currency
characteristics can be
measured using optical sensing. These include detection of a bill's density,
color,
length and thickness, the presence of a security thread and holes, and other
patterns
of reflectance and transmission. Color detection techniques may employ color
filters,
CA 02215853 1999-OS-04
colored lamps, and/or dichroic beamsplitters.
In addition to magnetic and optical sensing, other techniques of detecting
characteristic information of currency include electrical conductivity
sensing,
capacitive sensing (such as for watermarks, security threads, thickness, and
various
5 dielectric properties) and mechanical sensing (such as for size, limpness,
and
thickness).
A major obstacle in implementing automated currency discrimination systems
is obtaining an optimum compromise between the criteria used to adequately
define
the characteristic pattern for a particular currency denomination, the time
required to
10 analyze test data and compare it to predefined parameters in order to
identify the
currency bill under scrutiny, and the rate at which successive currency bills
may be
mechanically fed through and scanned. Even with the use of microprocessors for
processing the test data resulting from the scanning of a bill, a finite
amount of time
is required for acquiring samples and for the process of comparing the test
data to
15 stored parameters to identify the denomination of the bill.
Some of the currency scanning systems today scan for two or more
characteristics of bills to discriminate among various denominations or to
authenticate
their genuineness. However, these systems do not efficiently utilize the
information
which is obtained. Rather, these systems generally conduct comparison based on
the
20 two or more characteristics independently of each other. As a result; the
time
required to make these comparisons is increased which in turn can reduce the
operating speed of the entire scanning system.
Recent currency discriminating systems rely on comparisons between a
scanned pattern obtained from a subject bill and sets of stored master
patterns for the
25 various denominations among which the system is designed to discriminate.
As a
result, the master patterns which are stored play an important role in a
discrimination
system's ability to discriminate among bills of various denominations as well
as
between genuine bills and'counterfeit bills. These master patterns have been
generated by scanning bills of various denominations known to be genuine and
storing the resulting patterns. However, a pattern generated by scanning a
genuine
bill of a given denomination can vary depending upon a number of factors such
as the
condition of the bill, e.g., whether it is a crisp bill in new condition or a
worn,
CA 02215853 1999-OS-04
26
flimsy bill, as well as year in which the bill was printed, e.g., before or
after security
threads were incorporated into bills of some denominations. Likewise, it has
been
found that bills which have experienced a high degree of usage may shrink,
resulting
in a reduction of the dimensions of such bills. Such shrinkage may likewise
result in
S variations in scanning patterns. As a result, if, for example, a $20 master
pattern is
generated by scanning a crisp, genuine $20 bill, the discrimination system may
reject
an unacceptable number of genuine but worn $20 bills. Likewise, if a $20
master
pattern is generated using a very worn, genuine S20 bill, the discrimination
system
may reject an 'unacceptable number of genuine but crisp $20 bills.
It has been found that scanning U.S. bills of different denominations along a
central portion thereof provides scanning patterns sufficiently divergent to
enable
accurate discrimination between different denominations. Such a discrimination
device is disclosed in U.S. Pat. No. 5,295,196. However, currencies of other
countries can differ from U.S. currency and from each other in a number of
ways.
IS For example, while all denominations of U.S. currencies are the same size,
in many
other countries currencies vary in size by denomination. Furthermore, there is
a
wide variety of bill sizes among different countries. In addition to size, the
color of
currency can vary by country and by denomination. Likewise, many other
characteristics may vary between bills from different countries and of
different
denominations.
As a result of the wide variety of currencies used throughout the world, a
discrimination ,system designed to handle bills of one country generally can
not
handle bills from another country. Likewise, the, method of discriminating
bills of
different denominations of one country may not be appropriate for use in
discriminating bills of different denominations of another country. For
example,
scanning for a given characteristic pattern along a certain portion of bills
of one
country, such as optical reflectance about the central portion of U.S. bills,
may not
provide optimal discrimination properties for bills of another country, such
as
German marks.
Furthermore, there is a distinct need for an identification system which is
capable of accepting bills of a number of currency systems, that is, a system
capable
of accepting a number of bill-types. For example, a bank in Europe may need to
CA 02215853 1999-OS-04
27
process on a regular basis French, British, German, Dutch, etc. currency, each
having a number of different denomination values.
Some of the optical scanning systems available today employ two optical
scanheads disposed on opposite sides of a bill transport path. One of the
optical
S scanheads scans one surface (e.g., green surface) of a currency bill to
obtain a first
set of reflectance data samples, while the other optical scanhead scans the
opposite
surface (e.g., black surface) of the currency bill to obtain a second set of
reflectance
data samples. These two sets of data samples are then processed and compared
to
stored characteristic patterns corresponding to the green surfaces of currency
bills of
different denominations. If degree of correlation between either set of data
samples
and any of the stored characteristic patterns is greater than a predetermined
threshold,
then the denomination of the bill is positively identified.
A drawback of the foregoing technique for scanning both surfaces of a
currency bill is that it is time-consuming to process and compare both sets of
data
samples for the scanned bill to the stored characteristic patterns. The set of
data
samples corresponding to the black surface of the scanned bill are processed
and
compared to the stored characteristic patterns even though no match should be
found.
As previously stated, the stored characteristic patterns correspond to the
green
surfaces of currency bills of different denominations.
Another drawback of the foregoing scanning technique is that the set of data
samples corresponding to the black surface of the scanned bill occasionally
leads to
false positive identification of a scanned bill. The reason for this false
positive
identification is that if a scanned bill is slightly shifted in the lateral
direction relative
to the bill transport path, the set of data samples corresponding to the black
surface
of the scanned bill may sufficiently correlate with one of the stored
characteristic
patterns to cause a false positive identification of the bill. The degree of
correlation
between the set of "black" data samples and the stored "green" characteristic
patterns
should, of course, not be greater than the predetermined threshold for
positively
identifying the denomination of the bill.
Furthermore, in currency discriminating systems that rely on comparisons
between a scanned pattern obtained from a subject bill and sets of stored
master
patterns, the ability of a system to accurately line up the scanned patterns
to the
CA 02215853 1999-OS-04
28
master patterns to which they are being compared is important to the ability
of a
discrimination system to discriminate among bills of various denominations as
well as
between genuine bills and counterfeit bills without rejecting an unacceptable
number
of genuine bills. However, the ability of a system to line up scanned and
master
patterns is often hampered by the improper initiation of the scanning process
which
results in the generation of scanned patterns. If the generation of scanned
patterns is
initiated too early or too late, the resulting pattern will not correlate well
with the
master pattern associated with the identity of the currency; and as a result,
a genuine
bill may be rejected. There are a number of reasons why a discrimination
system
may initiate the generation of a scanned pattern too early or too late, for
example,
stray marks on a bill, the bleeding through of printed indicia from one bill
in a stack
onto an adjacent bill, the misdetection of the beginning of the area of the
printed
indicia which is desired to be scanned, and the reliance on the detection of
the edge
of a bill as the trigger for the scanning process coupled with the variance,
from bill
to bill, of the location of printed indicia relative to the edge of a bill.
Therefore,
there is a need to overcome the problems associated with correlating scanned
and
master patterns.
In some currency discriminators bills are transported, one at a time, passed a
discriminating unit. As the bills pass the discriminating unit, the
denomination of
each bill is determined and a naming total of each particular currency
denomination
and/or of the total value of the bills that are processed is maintained. A
number of
discriminatjmg techniques may be employed by the discriminating unit including
optical or magnetic scanning of bills. A plurality of output bins are provided
and the
discriminator includes means for .sorting bills into the plurality of bins.
For example,
a discriminator may be designed to recognize a number of different
denominations of
U.S. bills and comprise an equal number of output bins, one associated with
each
denomination. These discriminators also include a reject bin for receiving all
bills
which cannot be identified by the discriminating unit. These bills may later
be
examined by an operator and then either re-fed through the discriminator or
set aside
as unacceptable.
Depending on the design of a discriminator, bills may be transported and
scanned either along their long dimension or their narrow dimension. For a
CA 02215853 1999-OS-04
29
discriminator that transport bills in their narrow dimension, it is possible
that a given
bill may be oriented either face up or face down and either top edge first
("forward"
direction) or top edge last ("reverse" direction). For discriminators that
transport
bills in their long dimension, it is possible that a given bill may be
oriented either
face up or face down and either left edge first ("forward" direction) or left
edge last
("reverse" direction). The manner in which a bill must be oriented as it
passes a
discriminating unit depends on the characteristics of the discriminator. Some
discriminators are capable of identifying the denomination of a bill only if
it is fed
with a precise orientation, e.g., face up and top edge first. Other
discriminators are
capable of identifying bills provided they are "faced" (i.e., fed with a
predetermined
face orientation, that is all face up or all face down). For example, such a
discriminator may be able to identify a bill fed face up regardless of whether
the top
edge is fed first or last. Other discriminators are capable of identifying the
denomination fed with any orientation. However, whether a given discriminator
can
discriminate between bills fed with different orientations depends on the
discriminating method used. For example,, a discriminator that discriminates
bills
based on patterns of transmitted light may be able to identify the
denomination of a
forward fed bill regardless of whether the bill is fed face up or face down,
but the
same discriminator would not be able to discriminate between a bill fed face
up and a
bill fed face down.
Currently, discriminators are known which discriminate and/or sort by
denomination when bills are properly faced. In such systems, all reverse-faced
bills
are not identified and are routed to a reject receptacle. Also discriminators
are
known which discriminate and/or sort between all bills facing up and all bills
facing
down. For example, in a multi-output pocket system, all face up bills,
regardless of
denomination, may be routed to a first pocket and all face down bills,
regardless of
denomination, may be routed to a second pocket. Furthermore, there is
currently
known discriminators designed to accept a stack of faced bills and flag the
detection
of a reverse-faced bill, thus allowing the reverse-faced bill to be removed
from the
stack. However, there remains a need for a discriminator that can detect and
flag the
presence of a bill oriented with an incorrect forward/reverse orientation and
a
discriminator that can sort between forward-oriented bills and reverse-
oriented bills.
CA 02215853 1999-OS-04
Furthermore, for a number of reasons, a discriminating unit may be unable to
determine the denomination of a bill. These reasons include a bill being
excessively
soiled, worn, or faded, a bill being torn or folded, a bill being oriented in
a manner
that the discriminating unit cannot handle, and the discriminating unit having
poor
5 discriminating performance. Furthermore, the discriminating unit and/or a
separate
authenticating unit may determine that a bill is not genuine. In current
discriminators, such unidentified or non-genuine bills are deposited in a
reject
receptacle.
A characteristic of the above described discriminators is that the value of
any
10 rejected unidentified bills is not added to the running total of the
aggregate value of
the stack of bills nor do the counters keeping track of the number of each
currency
denomination reflect the rejected unidentified bills. While this is desirable
with
respect to bills which are positively identified as being fake, it may be
undesirable
with respect to bills which were not identified for other reasons even though
they are
15 genuine bills. While the bills in a reject receptacle may be re-fed through
the
discriminator, the operator must then add the totals from the first batch and
the
second batch together. Such a procedure can be inefficient in some situations.
Also,
if a bill was rejected the first time because it was, for example, excessively
soiled or
too worn, then it is likely that the bill will remain unidentified by the
discriminating
20 unit even if re-fed.
A problem with the above described situations where the totals and/or counts
do not reflect all the genuine bills in a stack is that an operator must then
count all
the unidentified genuine bills by. hand and add such bills to separately
generated
totals. As a result the chance for human error increases and operating
efficiency
25 decreases. Take for example a bank setting where a customer hands a teller
a stack
of currency to be deposited. The teller places the stack of bills in a
discriminator,
the display on the discriminator indicates that a total of $730 has been
identified.
However, fourteen genuine bills remain unidentified. As a result, the teller
must
count these fourteen bills by hand or re-fed through the discriminator and
then add
30 their total to the $730 total. An error could result from the teller
miscounting the
unidentified bills, the teller forgetting to add the two totals together, or
the teller
overlooking the unidentified bills entirely and only recording a deposit of
$730.
CA 02215853 1999-OS-04
31
Moreover, even if the teller makes no mistakes, the efficiency of the teller
is reduced
by having to manually calculate additional totals. The decrease in efficiency
is
further aggravated where detailed records must be maintained about the
specific
number of each denomination processed during each transaction.
S Therefore, there is a need for a currency discriminator which is capable of
conveniently and efficiently accommodating genuine bills that, for whatever
reason,
remain unidentified after passing through the discriminating unit of a
discriminator.
A number of methods have been developed for authenticating the genuineness
of security documents. These methods include sensing magnetic, optical,
conductive,
and other characteristics of documents under test. In general, it has been
found that
no single authentication test is capable of detecting all types of counterfeit
documents
while at the same time not rejecting any genuine documents. Therefore, more
than
one test may be employed whereby a first test is used to detect certain types
of
counterfeits and additional tests . are used to detect other types of
counterfeits.
It has been known that the illumination of certain substances with ultraviolet
light causes the substances to fluoresce, that is, to emit visible light. Some
documents employ fluorescent materials as a security feature to inhibit
counterfeiting.
Typically, these fluorescent security features comprise a marking which is
visibly
revealed when the document is illuminated with ultraviolet light. Previous
methods
have been developed to authenticate such documents by sensing the fluorescent
light
emitted by a document illuminated by ultraviolet light and comparing the
sensed
fluorescent light to the fluorescent light emitted by genuine documents.
Conversely, some documents, such as United States currency, are
manufactured from special paper designed not to fluoresce under ultraviolet
light.
Previously known authenticating methods for such documents have sensed for the
emission of fluorescent light under ultraviolet illumination and have rejected
as
counterfeit those documents emitting fluorescent light.
However, it has been found that the presently known ultraviolet authentication
methods do not detect all types of counterfeits. For example, while many
counterfeit
United States bills do emit fluorescent light under ultraviolet illumination,
some
counterfeit United States bills do not.
It is an object of the present invention to provide an improved method and
CA 02215853 1999-OS-04
32
apparatus for identifying, authenticating, and counting currency bills
comprising a
plurality of currency denominations.
It is another object of the present invention to provide an improved method
and apparatus for authenticating documents including currency documents.
It is an object of the present invention to provide an improved method and
apparatus for authenticating documents including currency documents by
illuminating
a document with ultraviolet light.
It is another object of the present invention to provide an improved method
and apparatus for authenticating documents which improves the ability of a
system to
accurately reject improper documents while reducing the likelihood of
rejecting
genuine documents.
Many features and aspects of the overall apparatus and methods are described
in
this specification, while this application is directed to and claims
particular
embodiments of the invention.
According to a preferred embodiment of the present invention, a document to
be authenticated is illuminated with ultraviolet light and the amount of
ultraviolet
light which is reflected off the document is measured. Based on the amount of
ultraviolet light which is detected, the document is either authenticated or
rejected.
In the case of documents being authenticated relative to United States
currency, a bill
is rejected if a high level of reflected ultraviolet light is not detected.
In another preferred embodiment, the above objectives are achieved by
illuminating a document with ultraviolet light and measuring both the amount
of
reflected ultraviolet light and the amount of emitted visible light. Based on
the
amount of ultraviolet light detected and ~ the amount of visible light
detected, a
document is either authenticated or rejected. In the case of documents being
authenticated relative to United States currency, a bill is rejected if either
a high level
of reflected ultraviolet light is not detected or even a low level of visible
light is
detected.
As explained above, it is known that some counterfeit United States bills
fluoresce, or emit visible light, when illuminated by ultraviolet light. As
genuine
United States currency does not fluoresce, the emission of visible light has
been
employed as a means of detecting counterfeit United States currency. However,
it
CA 02215853 1999-OS-04
33
has been found that not all counterfeit United States bills fluoresce; and
hence, such
counterfeits will not be detected by the above described fluorescence test.
It has been found that genuine United States currency reflects a high level of
ultraviolet light when illuminated by an ultraviolet light source. It has also
been
found that some counterfeit United States bills do not reflect a high level of
ultraviolet light. Such counterfeit bills may or may not also fluoresce under
ultraviolet light. The present invention employs an authentication test
wherein the
amount of reflected ultraviolet light is measured and a bill is rejected if it
does not
reflect a high amount of ultraviolet light. By employing such a test,
counterfeit
United States bills which do not reflect a high level of ultraviolet light may
be
properly rejected.
While not all counterfeit United States bills fail to reflect a high level of
ultraviolet light and hence not all counterfeit United States bills will be
detected using
this test, the present invention provides an additional means for detecting
counterfeit
bills which might otherwise go undetected. Furthermore, the likelihood of a
counterfeit United States bill going undetected may be further reduced by
employing
an alternative embodiment of the present invention wherein both the amount of
reflected ultraviolet light and the amount of emitted visible light are
measured. In
such a system, a bill is rejected as counterfeit if either it fails to reflect
a high level
of ultraviolet light or it fluoresces.
The above described embodiments may be adapted to authenticate currencies
from other countries and other types of documents such as food stamps and
checks.
For instance some genuine documents may be designed to reflect ultraviolet
light only
in certain locations and/or in a predetermined pattern. An alternative
embodiment of
the present invention may be designed to accept documents which exhibit
similar
characteristics while rejecting those which do not. Likewise, an alternative
embodiment of the present invention may be employed to authenticate documents
based on both their characteristics with respect to reflected ultraviolet
light and their
characteristics with respect to fluorescent emissions, e.g., detecting the
amount,
location, and/or pattern of fluorescent emissions.
Other objects and advantages of the invention will become apparent upon
reading the following detailed description in conjunction with the
accompanying
drawings.
CA 02215853 1997-11-06
34
Brief Description Of The Drawings
FIG. 1 is a perspective view of a currency scanning and counting machine
embodying the present invention;
FIG. 2a is a functional block diagram of the currency scanning and counting
machine of FIG. 1 illustrating a scanhead arranged on each side of a transport
path;
FIG. 2b is a functional block diagram of the currency scanning and counting
machine illustrating a scanhead arranged on a single side of a transport path;
FIG. 2c is a functional block diagram of the currency scanning and counting
machine similar to that of FIG. 2b but illustrating the feeding and scanning
of bills
along their wide direction;
FIG. 2d is a functional block diagram of the currency scanning and counting
machine similar to that of FIGs. 2a-2d illustrating the employment of a second
characteristic detector;
FIG. 3 is a diagrammatic perspective illustration of the successive areas
scanned during the traversing movement of a single bill across an optical
sensor
according to a preferred embodiment of the present invention;
FIGs. 4a and 4b are perspective views of a bill and a preferred area to be
optically scanned on the bill;
FIGs. Sa and Sb are diagrammatic side elevation views of the scan area to be
optically scanned on a bill according to preferred embodiments of the present
invention;
FIG. 6a is a perspective view of a bill showing the preferred area of a first
surface to be scanned by one of the two scanheads employed in the preferred
embodiment of the present invention;
FIG. 6b is another perspective view of the bill in FIG. 6a showing the
preferred area of a second surface to be scanned by the other of the scanheads
employed in the preferred embodiment of the present invention;
FIG. 6c is a side elevation showing the first surface of a bill scanned by an
upper scanhead and the second surface of the bill scanned by a lower scanhead;
FIG. 6d is a side elevation showing the first surface of a bill scanned by a
lower scanhead and the second surface of the bill scanned by an upper
scanhead;
w CA 02215853 1997-11-06-
FIGS. 7a and 7b form a block diagram illustrating a preferred circuit
arrangement for processing and correlating reflectance data according to the
optical
sensing and counting technique of this invention;
FIGs. 8a and 8b comprise a flowchart illustrating the sequence of operations
5 involved in implementing a discrimination and authentication system
according to a
preferred embodiment of the present invention;
FIG. 9 is a flow chart illustrating the sequential procedure involved in
detecting the presence of a bill adjacent the lower scanhead and the
borderline on the
side of the bill adjacent to the lower scanhead;
10 FIG. 10 is a flow chart illustrating the sequential procedure involved in
detecting the presence of a bill adjacent the upper scanhead and the
borderline on the
side of the bill adjacent to the upper scanhead;
FIG. lla is a flow chart illustrating the sequential procedure involved in the
analog-to-digital conversion routine associated with the lower scanhead;
15 FIG. llb is a flow chart illustrating the sequential procedure involved in
the
analog to-digital conversion routine associated with the upper scanhead;
FIG. 12 is a flow chart illustrating the sequential procedure involved in
determining which scanhead is scanning the green side of a U.S. currency bill;
FIG. 13 is a flow chart illustrating the sequence of operations involved in
20 determining the bill denomination from the correlation results;
FIG. 14 is a flow chart illustrating the sequential procedure involved in
decelerating and stopping the bill transport system in the event of an error;
FIG. 15a is a graphical illustration of representative characteristic patterns
generated by narrow dimension optical scanning of a $1 currency bill in the
forward
25 direction;
FIG. 15b is a graphical illustration of representative characteristic patterns
generated by narrow dimension optical scanning of a $2 currency bill in the
reverse
direction;
FIG. 15c is a graphical illustration of representative characteristic patterns
30 generated by narrow dimension optical scanning of a $100 currency bill in
the
forward direction;
CA 02215853 1997-11-06
36
FIG. 15d is a graph illustrating component patterns generated by scanning old
and new $20 bills according a second method according to a preferred
embodiment of
the present invention;
FIG. 15e is a graph illustrating an pattern for a $20 bill scanned in the
forward direction derived by averaging the patterns of FIG. 15d according a
second
method according to a preferred embodiment of the present invention;
FIGS. 16a-e are graphical illustrations of the effect produced on correlation
pattern by using the progressive shifting technique, according to an
embodiment of
this invention;
FIGs. 17a-17c are a flowchart illustrating a preferred embodiment of a
modified pattern generation method according to the present invention;
FIG. 18a is a flow chart illustrating the sequential procedure involved in the
execution of multiple correiations of the scan data from a single bill;
FIG. 18b is a flow chart illustrating a modified sequential procedure of that
of
FIG.lBa;
FIG. 19a is a flow chart illustrating the sequence of operations involved in
determining the bill denomination from the correlation results using data
retrieved
from the green side of U.S. bills according to one preferred embodiment of the
present invention;
FIGs. 19b and 19c are a flow chart illustrating the sequence of operations
involved in determining the bill denomination from the correlation results
using data
retrieved from the black side of U.S. bills;
FIG. 20a is an enlarged vertical section taken approximately through the
center of the machine, but showing the various transport rolls in side
elevation;
FIG. 20b is a top plan view of the interior mechanism of the machine of FIG.
1 for transporting bills across the optical scanheads, and also showing the
stacking
wheels at the front of the machine;
FIG. 21a is an enlarged perspective view of the bill transport mechanism
which receives bills from the stripping wheels in the machine of FIG. l;
FIG. 21b is a cross-sectional view of the bill transport mechanism depicted in
FIG. 21 along line 21b;
CA 02215853 1997-11-06
37
FIG. 22 is a side elevation of the machine of FIG. l, with the side panel of
the housing removed;
FIG. 23 is an enlarged bottom plan view of the lower support member in the
machine of FIG. 1 and the passive transport roils mounted on that member;
FIG. 24 is a sectional view taken across the center of the bottom support
member of FIG. 23 across the narrow dimension thereof;
FIG. 25 is an end elevation of the upper support member which includes the
upper scanhead in the machine of FIG. 1, and the sectional view of the lower
support
member mounted beneath the upper support member;
FIG. 26 is a section taken through the centers of both the upper and lower
support members, along the long dimension of the Iower support member shown in
FIG. 23;
FIG. 27 is a top plan view of the upper support member which includes the
upper scanhead;
FIG. 28 is a bottom plan view of the upper support member which includes
the upper scanhead;
FIG. 29 is an illustration of the light distribution produced about one of the
optical scanheads;
FIGS. 30a and 30b are diagrammatic illustrations of the location of two
auxiliary photo sensors relative to a bill passed thereover by the transport
and
scanning mechanism shown in FIGs. 20a-28;
FIG. 31 is a flow chart illustrating the sequential procedure involved in a
ramp-up routine for increasing the transport speed of the bill transport
mechanism
from zero to top speed;
FIG. 32 is a flow chart illustrating the sequential procedure involved in a
ramp-to-slow-speed routine for decreasing the transport speed of the bill
transport
mechanism from tog speed to slow speed;
FIG. 33 is a flow chart illustrating the sequential procedure involved in a
ramp-to-zero-speed routine for decreasing the transport speed of the bill
transport
mechanism to zero;
CA 02215853 1997-11-06
38
FIG. 34 is a flow chart illustrating the sequential procedure involved in a
pause-after-ramp routine for delaying the feedback loop while the bill
transport
mechanism changes speeds;
FIG. 35 is a flow chart illustrating the sequential procedure involved in a
feedback loop routine for monitoring and stabilizing the transport speed of
the bill
transport mechanism;
FIG. 36 is a flow chart illustrating the sequential procedure involved in a
doubles detection routine for detecting overlapped bills;
FIG. 37 is a flow chart illustrating the seque~.tial procedure involved in a
routine for detecting sample data representing dark blemishes on a bill;
FIG. 38 is a flow chart illustrating the sequential procedure involved in a
routine for maintaining a desired readhead voltage level;
FIG. 39 is a top view of a bill and size determining sensors according to a
preferred embodiment of the present invention;
FIG. 40 is a top view of a bill illustrating multiple areas to be optically
scanned on a bill according to a preferred embodiment of the present
invention;
FIG. 41a is a graph illustrating a scanned pattern which is offset from a
corresponding master pattern;
FIG. 41b is a graph illustrating the same patterns of FIG. 41a after the
scanned pattern is shifted relative to the master pattern;
FIG. 42 is a side elevation of a multiple scanhead arrangement according to a
preferred embodiment of the present invention;
FIG. 43 is a side elevation of a multiple scanhead arrangement according to
another preferred embodiment of the present invention;
FIG. 44 is a side elevation of a multiple scanhead arrangement according to
another preferred embodiment of the present invention;
FIG. 45 is a side elevation of a multiple scanhead arrangement according to
another preferred embodiment of the present invention; '
FIG. 46 is a top view of a staggered scanhead arrangement according to a
preferred embodiment of the present invention;
FIG. 47a is a top view of a linear array scanhead according to a preferred
embodiment of the present invention illustrating a bill being fed in a
centered fashion;
CA 02215853 1997-11-06
39
FIG. 47b is a side view of a linear array scanhead according to a preferred
embodiment of the present invention illustrating a bill being fed in a
centered fashion;
FIG. 48 is a top view of a linear array scanhead according to another
preferred embodiment of the present invention illustrating a bill being fed in
a non-
centered fashion;
FIG. 49 is a top view of a linear array scanhead according to another
preferred embodiment of the present invention illustrating a bill being fed in
a
skewed fashion;
FIGs. SOa and SOb are a flowchart of the operation of a currency
discrimination system according to a preferred embodiment of the present
invention;
FIG. 51 is a top view of a triple scanhead arrangement utilized in a
discriminating device able to discriminate both Canadian and Gerrrlan bills
according
to a preferred embodiment of the present invention;
FIG. 52 is a top view of Canadian bill illustrating the areas scanned by the
triple scanhead arrangement of FIG. 51 according to a preferred embodiment of
the
present invention;
FIG. 53 is a flowchart of the threshold tests utilized in calling the
denomination of a Canadian bill according to a preferred embodiment of the
present
invention;
FIG. 54a illustrates the general areas scanned in generating master 10 DM
German patterns according to a preferred embodiment of the present invention;
FIG. 54b illustrates the general areas scanned in generating master 20 DM,
SO DM, and 100 DM German patterns according to a preferred embodiment of the
present invention;
FIG. 55 is a flowchart of the threshold tests utilized in calling the
denomination of a German bill according to a preferred embodiment of the
present
invention;
FIG. 56 is a functional block diagram illustrating a preferred embodiment of a
document authenticator and discriminator according to the present invention;
FIG. 57 is a functional block diagram illustrating another preferred
embodiment of a document authenticator and discriminator according to the
present
invention;
CA 02215853 1997-11-06
FIG. 58 is a functional block diagram illustrating another preferred
embodiment of a document authenticator and discriminator according to the
present
invention;
FIG. 59 is an enlarged plan view of the control and display panel in the
5 machine of FIG. 1;
FIG. 60a is a side view of a preferred embodiment of a document
authenticating system according to the present invention;
FIG. 60b is a top view of the preferred embodiment of FIG. 60a along the
direction 60b;
10 FIG. 60c is a top view of the preferred embodiment of FIG. 60a along the
direction 60c; and
FIG. 61 is a functional block diagram illustrating a preferred embodiment of a
document authenticating system according to the present invention.
15 Detailed Description Of The Preferred Embodiments
While the invention is susceptible to various modifications and alternative
forms, specific embodiments thereof have been shown by way o~ example in the
drawings and will herein be described in detail. It should be understood,
however,
that it is not intended to limit the invention to the particular forms
disclosed, but on
20 the contrary, the intention is to cover all modifications, equivalents, and
alternatives
falling within the spirit and scope of the invention as defined by the
appended claims.
According to a preferred embodiment of the present invention, a currency
discrimination system adapted to U.S. currency is described in connection
with, for
example, FIGS. 1-38. Subsequently, modifications to such a discrimination
system
25 will be described in obtaining a currency discrimination system in
accordance with
other preferred embodiments of the present invention, such a currency
discriminator
systems having multiple scanheads per side. Furthermore, while the preferred
embodiments below entail the scanning of currency bills, the system of the
present
invention is applicable to other documents as well. For example, the system of
the
30 present invention may be employed in conjunction with stock certificates,
bonds, and
postage and food stamps.
CA 02215853 1997-11-06
41
Referring now to FIGS. 1 and 2a, there is shown a preferred embodiment of a
currency scanning and counting machine 10 according to the present invention.
The
machine 10 includes an input receptacle or bill accepting station 12 where
stacks of
currency bills that need to be identified and counted are positioned. Bills in
the input
receptacle are acted upon by a bill separating station 14 which functions to
pick out
or separate one bill at a time for being sequentially relayed by a bill
transport
mechanism 16 (FIG. 2a), according to a precisely predetermined transport path,
between a pair of scanheads 18a, 18b where the currency denomination of the
bill is
scanned and identified. In the preferred embodiment, bills are scanned and
identified
at a rate in excess of 800 bills per minute. In the preferred embodiment
depicted,
each scanhead 18a, 18b is an optical scanhead that scans for characteristic
information from a scanned bill 17 which is used to identify the .denomination
of the
bill. The scanned bill 17 is then transported to an output receptacle or bill
stacking
station 20 where bills so processed are stacked for subsequent removal.
Each optical scanhead 18a, 18b preferably comprises a pair of light sources 22
directing light onto the bill transport path so as to illuminate a
substantially
rectangular light strip 24 upon a currency bill 17 positioned on the transport
path
adjacent the scanhead 18. Light reflected off the illuminated strip 24 is
sensed by a
photodetector 26 positioned between the two light sources. The analog output
of the
photodetector 26 is converted into a digital signal by means of an analog-to-
digital
(ADC) convertor unit 28 whose output is fed as a digital input to a central
processing
unit (CPU) 30.
While scanheads 18a, 18b of FIG. 2a are optical scanheads, it should be
understood that it may be designed to detect a variety of characteristic
information
from currency bills. Additionally, the scanhead may employ a variety of
detection
means such as magnetic, optical, electrical conductivity, and capacitive
sensors. Use
of such sensors is discussed in more detail below (see e.g., FIG. 2d).
Referring again to FIG. 2a, the bill transport path is defined in such a way
that the transport mechanism 16 moves currency bills with the narrow dimension
of
the bills being parallel to the transport path and the scan direction.
Alternatively, the
system 10 may be designed to scan bills along their long dimension or along a
skewed dimension. As a bill 17 traverses the scanheads 18a, 18b, the coherent
light
CA 02215853 1997-11-06
42
strip 24 effectively scans the bill across the narrow dimension of the bill.
In the
preferred embodiment depicted, the transport path is so arranged that a
currency bill
17 is scanned across a central section of the bill along its narrow dimension,
as
shown in FIG. 2a. Each scanhead functions to detect light reflected from the
bill as
it moves across the illuminated light strip 24 and to provide an analog
representation
of the variation in reflected light, which, in turn, represents the variation
in the dark
and light content of the printed pattern or indicia on the surface of the
bill. This
variation in light reflected from the narrow dimension scanning of the bills
serves as
a measure for distinguishing, with a high degree of confidence, among a
plurality of
currency denominations which the system is programmed to handle.
A series of such detected reflectance signals are obtained across the narrow
dimension of the bill, or across a selected segment thereof, and the resulting
analog
signals are digitized under control of the CPU 30 to yield a fixed number of
digital
reflectance data samples. The data samples are then subjected to a normalizing
routine for processing the sampled data for improved correlation and for
smoothing
out variations due to "contrast" fluctuations in the printed pattern existing
on the bill
surface. The normalized reflectance data represents a characteristic pattern
that is
unique for a given bill denomination and provides su~cient distinguishing
features
among characteristic patterns for different currency denominations.
In order to ensure strict correspondence between reflectance samples obtained
by narrow dimension scanning of successive bills, the reflectance sampling
process is
preferably controlled through the CPU 30 by means of an optical encoder 32
which is
linked to the bill transport mechanism 16 and precisely tracks the physical
movement
of the bill 17 between the scanheads 18a, 18b. More specifically, the optical
encoder
32 is linked to the rotary motion of the drive motor which generates the
movement
imparted to the bill along the transport path. In addition, the mechanics of
the feed
mechanism ensure that positive contact is maintained between the bill and the
transport path, particularly when the bill is being scanned by the scanheads.
Under
these conditions, the optical encoder 32 is capable of precisely tracking the
movement
of the bill 17 relative to the light strips 24 generated by the scanheads 18a,
18b by
monitoring the rotary motion of the drive motor.
CA 02215853 1997-11-06
43
The outputs of the photodetectors 26 are monitored by the CPU 30 to initially
detect the presence of the bill adjacent the scanheads and, subsequently, to
detect the
starting point of the printed pattern on the bill, as represented by the thin
borderline
17a which typically encloses the printed indicia on currency bills. Once the
S borderline 17a has been detected, the optical encoder 32 is used to control
the timing
and number of reflectance samples that are obtained from the outputs of the
photodetectors 26 as the bill 17 moves across the scanheads.
FIG. 2b illustrates a preferred embodiment of a currency scanning and
counting machine 10 similar to that of FIG. 2a but having a scanhead on only a
single side of the transport path.
FIG. 2c illustrates a preferred embodiment of a currency scanning and
counting machine 10 similar to that of FIG. 2b but illustrating feeding and
scanning
of bills along their wide direction.
As illustrated in FIGS. 2b-2c, the transport mechanism 16 moves currency
bills with a preselected one of their two dimensions (narrow or wide) being
parallel
to the transport path and the scan direction. FIGs. 2b and 4a illustrate bills
oriented
with their narrow dimension "W" parallel to the direction of movement and
scanning
while FIGS. 2c and 4b illustrate bills oriented with their wide dimension "L"
parallel
to the direction of movement and scanning.
Referring now to FIG. 2d, there is shown a functional block diagram
illustrating a preferred embodiment of a currency discriminating and
authenticating
system according to the present invention. The operation of the system of FIG.
2d is
the same as that of FIG. Za except as modified below. The system 10 includes a
bill
accepting station 12 where stacks of currency bills that need to be
identified,
authenticated, and counted are positioned. Accepted bills are acted upon by a
bill
separating station 14 which functions to pick out or separate one bill at a
time for
being sequentially relayed by a bill transport mechanism 16, according to a
precisely
predetermined transport path, across two scanheads 18 and 39 where the
currency
denomination of the bill is identified and the genuineness of the bill is
authenticated.
In the preferred embodiment depicted, scanhead 18 is an optical scanhead that
scans
for a first type of characteristic information from a scanned bill 17 which is
used to
identify the bill's denomination. A second scanhead 39 scans for a second type
of
CA 02215853 1999-OS-04
44
characteristic information from the scanned bill 17. While in the illustrated
preferred
embodiment scanheads 18 and 39 are separate and distinct, it is understood
that these
may be incorporated into a single scanhead. For example, where the first
characteristic sensed is intensity of reflected light and the second
characteristic sensed
S is color, a single optical scanhead having a plurality of detectors, one or
more
without filters and one or more with colored filters, may be employed (U.S.
Pat. No.
4,992, 860 ). The scanned bill is then transported to a bill stacking station
20
where bills so processed are stacked for subsequent removal.
The optical scanhead 18 of the preferred embodiment depicted in FIG. 2d
comprises at least one light source 22 directing a beam of coherent light
downwardly
onto the bill transport path so as to illuminate a substantially rectangular
light strip 24
upon a currency bill 17 positioned on the transport path below the scanhead
18.
Light reflected off the illuminated strip 24 is sensed by a photodetector 26
positioned
directly above the strip. The analog output of photodetector 26 is converted
into a
digital signal by means of an analog-to-digital (ADC) convertor unit 28 whose
output
is fed as a digital input to a central processing unit (CPU) 30.
The second scanhead 39 comprises at least one detector 41 for sensing a
second type of characteristic information from a bill. The analog output of
the
detector 41 is converted into a digital signal by means of a second analog to
digital
converter 43 whose output is also fed as a digital input to the central
processing unit
(CPU) 30.
While scanhead 18 in the preferred embodiment of FIG. 2d is an optical
scanhead, it should be understood that the first and second scanheads 18 and
39 may
be designed to detect a variety of characteristic information from currency
bills.
Additionally these scanheads may employ a variety of detection means such as
magnetic or optical sensors. For example, a variety of currency
characteristics can
be measured using magnetic sensing. These include detection of patterns of
changes
in magnetic flux (U.S. Pat. No. 3,280,974), patterns of vertical grid lines in
the
portrait area of bills (U.S. Pat. No. 3,870,629), the presence of a security
thread
(U.S. Pat. No. 5,151,607), total amount of magnetizable material of a bill
(U.S. Pat.
No. 4,617,458), patterns from sensing the strength of magnetic fields along a
bill
CA 02215853 1997-11-06
(U.S. Pat. No. 4,593,184), and other patterns and counts from scanning
different
portions of the bill such as the area in which the denomination is written out
(U.S.
Pat. No. 4,356,473).
With regards to optical sensing, a variety of currency characteristics can be
measured such as detection of density (U.S. Pat. No. 4,381,447), color (U.S.
Pat.
Nos. 4,490,846; 3,496,370; 3,480,785), length and thickness (U.S. Pat. No.
4,255,651), the presence of a security thread (U.S. Pat. No. 5,151,607) and
holes
(U.S. Pat. No. 4,381,447), and other patterns of reflectance and transmission
{U.S.
Pat. No. 3,496,370; 3,679,314; 3,870,629; 4,179,685). Color detection
techniques
10 may employ color filters, colored lamps, and/or dichroic beamsplitters
{U.S. Pat.
Nos. 4,841,358; 4,658,289; 4,716,456; 4,825,246, 4,992,860 and EP 325,364).
In addition to magnetic and optical sensing, other techniques of detecting
characteristic information of currency include electrical conductivity
sensing,
capacitive sensing {U.S. Pat. No. 5;122,754 [watermark, security thread];
3,764,899
15 [thickness]; 3,815,021 [dielectric properties]; 5,151,607 [security
thread]), and
mechanical sensing (U.S. Pat. No. 4,381,447 [limpness]; 4,255,651
[thickness]).
According to one preferred embodiment, the detection of the borderline 17a
constitutes an important step and realizes improved discrimination efficiency
in
systems designed to accommodate U.S. currency since the borderline 17a serves
as
20 an absolute reference point for initiation of sampling. If the edge of a
bill were to be
used as a reference point, relative displacement of sampling points can occur
because
of the random manner in which the distance from the edge to the borderline 17a
varies from bill to bill due to the relatively large range of tolerances
permitted during
printing and cutting of currency bills. As a result, it becomes difficult to
establish
25 direct correspondence between sample points in successive bill scans and
the
discrimination efficiency is adversely affected. Accordingly, the modified
pattern
generation method of the present invention (to be discussed below) is
especially
important in discrimination systems designed to accommodate bills other than
U.S.
currency because many non-U.S. bills lack a borderline around the printed
indicia on
30 their bills. Likewise, the modified pattern generation method of the
present invention
is especially important in discrimination systems designed to accommodate
bills other
than U.S. currency because the printed indicia of many non-U.S. bills lack
sharply
CA 02215853 1997-11-06
46
defined edges which in turns inhibits using the edge of the printed indicia of
a bill as
a trigger for the initiation of the scanning process and instead promotes
reliance on
using the edge of the bill itself as the trigger for the initiation of the
scanning
process.
The use of the optical encoder 32 for controlling the sampling process
relative
to the physical movement of a bill 17 across the scanheads 18a, 18b is also
advantageous in that the encoder 32 can be used to provide a predetermined
delay
following detection of the borderline 17a prior to initiation of samples. The
encoder
delay can be adjusted in such a way that the bill 17 is scanned only across
those
segments which contain the most distinguishable printed indicia relative to
the
different currency denominations.
In the case of U.S. currency, for instance, it has been determined that the
central, approximately two-inch (approximately 5 cm) portion of currency
bills, as
scanned across the central section of the narrow dimension of the bill,
provides
sufficient data for distinguishing among the various U.S. currency
denominations.
Accordingly, the optical encoder can be used to control the scanning process
so that
reflectance samples are taken for a set period of time and only after a
certain period
of time has elapsed after the borderline 17a is detected, thereby restricting
the
scanning to the desired central portion of the narrow dimension of the bill.
FIGs. 3-Sb illustrate the scanning process in more detail. Referring to FIG.
4a, as a bill 17 is advanced in a direction parallel to the narrow edges of
the bill,
scanning via a slit in the scanhead 18a or 18b is effected along a segment S
of the
central portion of the bill 17. This segment S begins a fixed distance D
inboard of
the borderline 17a. As the bill 17 traverses the scanhead; a strip s of the
segment S
is always illuminated, and the photodetector 26 produces a continuous output
signal
which is proportional to the intensity of the light reflected from the
illuminated strip s
at any given instant. This output is sampled at intervals controlled by the
encoder, so
that the sampling intervals are precisely synchronized with the movement of
the bill
across the scanhead. FIG. 4b is similar to FIG. 4a but illustrating scanning
along the
wide dimension of the bill 17.
As illustrated in FIGS. 3, Sa, and Sb, it is preferred that the sampling
intervals
be selected so that the strips s that are illuminated for successive samples
overlap one
CA 02215853 1997-11-06
47
another. The odd-numbered and even-numbered sample strips have been separated
in
FIGS. 3, 5a, and 5b to more clearly illustrate this overlap. For example, the
first
and second strips s 1 and s2 overlap each other, the second and third strips
s2 and s3
overlap each other, and so on. Each adjacent pair of strips overlap each
other. In
the illustrative example, this is accomplished by sampling strips that are
0.050 inch
(0.127 cm) wide at 0.029 inch (0.074 cm) intervals, along a segment S that is
1.83
inch (4.65 cm) long (64 samples).
FIGS. 6a and 6b illustrate two opposing surfaces of U.S. bills. The printed
pattern on the black and green surfaces of the bill are each enclosed by
respective
thin borderlines B1 and BZ. As a bill is advanced in a direction parallel to
the narrow
edges of the bill, scanning via the wide slit of one of the scanheads is
effected along
a segment SA of the central portion of the black surface of the bill (FIG.
6a). As
previously stated, the orientation of the bill along the transport path
determines
whether the upper or lower scanhead scans the black surface of the bill. This
segment SA begins a fixed distance D, inboard of the borderline Bl, which is
located
a distance W1 from the edge of the bill. The scanning along segment SA is as
describe in connection with FIGS. 3, 4a, and 5a. .
Similarly, the other of the two scanheads scans a segment SB of the central
portion of the green surface of the bill (FIG. 6b). The orientation of the
bill along
the transport path determines whether the upper or lower scanhead scans the
green
surface of the bill. This segment SB begins a fixed distance DZ inboard of the
border
line B2, which is located a distance W2 from the edge of the bill. For U.S.
currency,
the distance WZ on the green surface is greater than the distance Wl on the
black
surface. It is this feature of U.S. currency which permits one to determine
the
orientation of the bill relative to the upper and lower scanheads 18, thereby
permitting one to select only the data samples corresponding to the green
surface for
correlation to the master characteristic patterns in the EPROM 34. The
scanning
along segment SB is as describe in connection with FIGS. 3, 4a, and 5a.
FIGs. 6c and 6d are side elevations of FIG. 2a according to a preferred
embodiment of the present invention. FIG. 6c shows the first surface of a bill
scanned by an upper scanhead and the second surface of the bill scanned by a
lower
scanhead while FIG. 6d shows the first surface of a bill scanned by a lower
scanhead
CA 02215853 1997-11-06
48
and the second surface of the bill scanned by an upper scanhead. FIGS. 6c and
6d
illustrate the pair of optical scanheads 18a, 18b are disposed on opposite
sides of the
transport path to permit optical scanning of both opposing surfaces of a bill.
With
respect to United States currency, these opposing surfaces correspond to the
black
and green surfaces of a bill. One of the optical scanheads 18 (the "upper"
scanhead
18a in FIGS. 6c-6d) is positioned above the transport path and illuminates a
light strip
upon a first surface of the bill, while the other of the optical scanheads 18
(the
"lower" scanhead 18b in FIGs. 6c-6d) is positioned below the transport path
and
illuminates a light strip upon the second surface of the bill. The surface of
the bill
scanned by each scanhead 18 is determined by the orientation of the bill
relative to
the scanheads 18. The upper scanhead 18a is located slightly upstream relative
to the
lower scanhead 18b.
The photodetector of the upper scanhead 18a produces a first analog output
corresponding to the first surface of the bill, while the photodetector of the
lower
scanhead 18b produces a second analog output corresponding to the second
surface of
the bill. The first and second analog outputs are converted into respective
first and
second digital outputs by means of respective analog-to-digital (ADC)
convertor units
28 whose outputs are fed as digital inputs to a central processing unit (CPU)
30. As
described in detail below, the CPU 30 uses the sequence of operations
illustrated in
FIG. 12 to determine which of the first and second digital outputs corresponds
to the
green surface of the bill, and then selects the "green" digital output for
subsequent
correlation to a series of master characteristic patterns stored in EPROM 34.
As
explained below, the master characteristic patterns are preferably generated
by
performing scans on the green surfaces, not black surfaces, of bills of
different
denominations. According to a preferred embodiment, the analog output
corresponding to the black surface of the bill is not used for subsequent
correlation.
The optical sensing and correlation technique is based upon using the above
process to generate a series of stored intensity signal patterns using genuine
bills for '
each denomination of currency that is to be detected. According to a preferred
embodiment, two or four sets of master intensity signal samples are generated
and
stored within the system memory, preferably in the form of an EPROM 34 (see
FIG.
2a), for each detectable currency denomination. According to one preferred
CA 02215853 1997-11-06
49
embodiment these are sets of master green-surface intensity signal samples. In
the
case of U.S. currency, the sets of master intensity signal samples for each
bill are
generated from optical scans, performed on the green surface of the bill and
taken
along both the "forward" and "reverse" directions relative to the pattern
printed on
the bill. Alternatively, the optical scanning may be performed on the black
side of
U.S. currency bills or on either surface of foreign bills. Additionally, the
optical
scanning may be performed on both sides of a bill.
In adapting this technique to U.S. currency, for example, sets of stored
intensity signal samples are generated and stored for seven different
denominations of
U.S. currency, i.e., $1, $2, $5, $10, $20, $50 and $100. For bills which
produce
significant pattern changes when shifted slightly to the left or right, such
as the $2,
the $10 and/or the $100 bills in U.S. currency, it is preferred to store two
green-side
patterns for each of the "forward" and "reverse" directions, each pair of
patterns for
the same direction represent two scan areas that are slightly displaced from
each
other along the long dimension of the bill. Accordingly, a set of 16 [or 18]
different
green-side master characteristic patterns are stored within the EPROM for
subsequent
correlation purposes (four master patterns for the $10 bill [or four master
patterns for
the $10 bill and the $2 bill and/or the $100 bill] and two master patterns for
each of
the other denominations). The generation of the master patterns is discussed
in more
below. Once the master patterns have been stored, the pattern generated by
scanning
a bill under test is compared by the CPU 30 with each of the 16 [or 18] master
patterns of stored intensity signal samples to generate, for each comparison,
a
correlation number representing the extent of correlation, i.e., similarity
between
corresponding ones of the plurality of data samples, for the sets of data
being
compared.
According to a preferred embodiment, in addition to the above set of 18
original green-side master patterns, five more sets of green-side master
patterns are
stored in memory. These sets are explained more fully in conjunction with
FIGs.
18a and 18b below.
The CPU 30 is programmed to identify the denomination of the scanned bill
as corresponding to the set of stared intensity signal samples for which the
correlation
number resulting from pattern comparison is found to be the highest. In order
to
CA 02215853 1997-11-06
preclude the possibility of mischaracterizing the denomination of a scanned
bill, as
well as to reduce the possibility of spurious notes being identified as
belonging to a
valid denomination, a bi-level threshold of correlation is used as the basis
for making
a "positive" call. If a "positive" call can not be made for a scanned bill, an
error
5 signal is generated.
According to a preferred embodiment, master patterns are also stored for
selected denominations corresponding to scans along the black side of U.S.
bills.
More particularly, according to a preferred embodiment, multiple black-side
master
patterns are stored for $20, $50 and $100 bills. For each of these
denominations,
10 three master patterns are stored for scans in the forward and reverse
directions for a
total of six patterns for each denomination. For a given scan direction, black-
side
master patterns are generated by scanning a corresponding denominated bill
along a
segment located about the center of the narrow dimension of the bill, a
segment
slightly displaced (0.2 inches) to the left of center, and a segment slightly
displaced
15 (0.2 inches) to the right of center. When the scanned pattern generated
from the
green side of a test bill fails to sufficiently correlate with one of the
green-side master
patterns, the scanned pattern generated from the black side of a. test bill is
then
compared to black-side master patterns in some situations as described in more
detail
below in conjunction with FIGS. 19a-19c.
20 Using the above sensing and correlation approach, the CPU 30 is programmed
to count the number of bills belonging to a particular currency denomination
as part
of a given set of bills that have been scanned for a given scan batch, and to
determine the aggregate total of the currency amount represented by the bills
scanned
during a scan batch: The CPU 30 is also linked to an output unit 36 (Fits. 2a
and
25 FIG. 2b) which is adapted to provide a display of the number of bills
counted, the
breakdown of the bills in terms of currency denomination, and the aggregate
total of
the currency value represented by counted bills. The output unit 36 can also
be
adapted to provide a print-out of the displayed information in a desired
format.
Referring again to the preferred embodiment depicted in FIG. 2d, as a result
30 of the first comparison described above based on the reflected light
intensity
information retrieved by scanhead 18, the CPU 30 will have either determined
the
denomination of the scanned bill 17 or determined that the first scanned
signal
-- CA 02215853 1997-11-06 -
~1
samples fail to sufficiently correlate with any of the sets of stored
intensity signal
samples in which case an error is generated, Provided that an error has not
been
generated as a result of this first comparison based on reflected light
intensity
characteristics, a second comparison is performed. This second comparison is
performed based on a second type of characteristic information, such as
alternate
reflected light properties, similar reflected light properties at alternate
locations of a
bill, light transmissivity properties, various magnetic properties of a bill,
the presence
of a security thread embedded within a bill, the color of a bill, the
thickness or other
dimension of a bill, etc. The second type of characteristic information is
retrieved
from a scanned bill by the second scanhead 39. The scanning and processing by
scanhead 39 may be controlled in a manner similar to that described above with
regard to scanhead 18.
In addition to the sets of stored first characteristic information, in this
example
stored intensity signal samples, the EPROM 34 stores sets of stored second
characteristic information for genuine bills of the different denominations
which the
system 10 is capable of handling. Based on the denomination indicated by the
first
comparison, the CPU 30 retrieves the set or sets of stored second
characteristic data
for a genuine bill of the denomination so indicated and compares the retrieved
information with the scanned second characteristic information. If sufficient
correlation exists between the retrieved information and the scanned
information, the
CPU 30 verifies the genuineness of the scanned bill 17. Otherwise, the CPU
generates an error. While the preferred embodiment illustrated in FIG. 2d
depicts a
single CPU 30 for making comparisons of first and second characteristic
information
and a single EPROM 34 for storing first and second characteristic information,
it is
understood that two or more CPUs and/or EPROMs could be used, including one
CPU for making first characteristic information comparisons and a second CPU
for
making second characteristic information comparisons. Using the above sensing
and
correlation approach, the CPU 30 is programmed to count the number of bills
belonging to a particular currency denomination whose genuineness has been
verified
as part of a given set of bills that have been scanned for a given scan batch,
and to
determine the aggregate total of the currency amount represented by the bills
scanned
during a scan batch.
CA 02215853 1997-11-06
-~ , _ _
52
Referring now to FIGs. 7a and 7b, there is shown a representation, in block
diagram form, of a preferred circuit arrangement for processing and
correlating
reflectance data according to the system of this invention. The CPU 30 accepts
and
processes a variety of input signals including those from the optical encoder
32, the
sensor 26 and the erasable programmable read only memory (EPROM) 60. The
EPROM 60 has stored within it the correlation program on the basis of which
patterns are generated and test patterns compared with stored master programs
in
order to identify the denomination of test currency. A crystal 40 serves as
the time
base for the CPU 30, which is also provided with an external reference voltage
VHF
42 on the basis of which peak detection of sensed reflectance data is
performed.
According to one embodiment, the CPU 30 also accepts a timer reset signal
from a reset unit 44 which, as shown in FIG. 7b, accepts the output voltage
from the
photodetector 26 and compares it, by means of a threshold detector 44a,
relative to a
pre-set voltage threshold, typically 5.0 volts, to provide a reset signal
which goes
"high" when a reflectance value corresponding to the presence of paper is
sensed.
More specifically, reflectance sampling is based on the premise that no
portion of the
illuminated light strip (24 in FIG. 2a) is reflected to the photodetector in
the absence
of a bill positioned below the scanhead. Under these conditions, the output of
the
photodetector represents a "dark" or "zero" level reading. The photodetector
output
changes to a "white" reading, typically set to have a value of about 5.0
volts, when
the edge of a bill first becomes positioned below the scanhead and falls under
the
light strip 24. When this occurs, the reset unit 44 provides a "high" signal
to the
CPU 30 and marks the initiation of the scanning procedure.
The machine-direction dimension, that is, the dimension parallel to the
direction of bill movement, of the illuminated strip of light produced by the
light
sources within the scanhead is set to be relatively small for the initial
stage of the
scan when the thin borderline is being detected, according to a preferred
embodiment. The use of the narrow slit increases the sensitivity with which
the
reflected light is detected and allows minute variations in the "gray" level
reflected
off the bill surface to be sensed. This is important in ensuring that the thin
borderline of the pattern, i:e., the starting point of the printed pattern on
the bill, is
accurately detected. Once the borderline has been detected, subsequent
reflectance
CA 02215853 1997-11-06
53
sampling is performed on the basis of a relatively wider light strip in order
to
completely scan across the narrow dimension of the bill and obtain the desired
number of samples, at a rapid rate. The use of a wider slit for the actual
sampling
also smooths out the output characteristics of the photodetector and realizes
the
relatively large magnitude of analog voltage which is essential for accurate
representation and processing of the detected reflectance values.
The CPU 30 processes the output of the sensor 26 through a peak detector 50
which essentially functions to sample the sensor output voltage and hold the
highest,
i.e., peak, voltage value encountered after the detector has been enabled. For
U.S.
currency, the peak detector is also adapted to define a scaled voltage on the
basis of
which the printed borderline on the currency bills is detected. The output of
the peak
detector 50 is fed to a voltage divider 54 which lowers the peak voltage down
to a
scaled voltage VS representing a predefined percentage of this peak value. The
voltage VS is based upon the percentage drop in output voltage of the peak
detector as
it reflects the transition from the "high" reflectance value resulting from
the scanning
of the unprinted edge portions of a currency bill to the relatively lower
"gray"
reflectance value resulting when the thin borderline is encountered..
Preferably, the
scaled voltage VS is set to be about 70 - 80 percent of the peak voltage.
The scaled voltage VS is supplied to a line detector 56 which is also provided
with the incoming instantaneous output of the sensor 26. The line detector 56
compares the two voltages at its input side and generates a signal LDE.,.
which
normally stays "iow" and goes "high" when the edge of the bill is scanned. The
signal L,DET goes "low" when the incoming sensor output reaches the pre-
defined
percentage of the peak output up to that point, as represented by the voltage
VS.
Thus, when the signal LDE.r. goes "low", it is an indication that the
borderline of the
bill pattern has been detected. At this point, the CPU 30 initiates the actual
reflectance sampling under control of the encoder 32 and the desired fixed
number of
reflectance samples are obtained as the currency bill moves across the
illuminated
light strip and is scanned along the central section of its narrow dimension.
When master characteristic patterns are being generated, the reflectance
samples resulting from the scanning of one or more genuine bills for each
denomination are loaded into corresponding designated sections within a system
CA 02215853 1997-11-06
54
memory 60, which is preferably an EPROM. During currency discrimination, the
reflectance values resulting from the scanning of a test bill are sequentially
compared,
under control of the correlation program stored within the EPROM 60, with the
corresponding master characteristic patterns stored within the EPROM 60. A
pattern
averaging procedure for scanning bills and generating characteristic patterns
is
described below in connection with FIGs. 15a-15e.
In addition to the optical scanheads, the bill-scanning system (e.g., FIGs. 2a-
2d) preferably includes a magnetic scanhead. A variety of currency
characteristics
can be measured using magnetic scanning. These include detection of patterns
of
changes in magnetic flux (U.S. Pat. No. 3,280,974), patterns of vertical grid
lines in
the portrait area of bills (U.S. Pat. No. 3,870,629), the presence of a
security thread
(U.S. Pat. No. 5,151,607), total amount of magnetizable material of a bill
(U.S. Pat.
No. 4,617,458), patterns from sensing the strength of magnetic fields along a
bill
{U.S. Pat. No. 4,593,184), and other patterns and counts from scanning
different
portions of the bill such as the area in which the denomination is written out
(U.S.
Pat. No. 4,356,473).
The interrelation between the use of the first and second . type of
characteristic
information can be seen by considering FIGs. 8a and 8b which comprise a
flowchart
illustrating the sequence of operations involved in implementing a
discrimination and
authentication system according to a preferred embodiment of the present
invention.
Upon the initiation of the sequence of operations (step 1748), reflected light
intensity
information is retrieved from a bill being scanned (step 1750). Similarly,
second
characteristic information is also retrieved from the bill being scanned (step
1752).
Denomination error and second characteristic error flags are cleared (steps
1753 and
1754).
Next the scanned intensity information is compared to each set of stored
intensity information corresponding to genuine bills of all denominations the
system is
programmed to accommodate (step 1758). For each denomination, a correlation
number is calculated. The system then, based on the correlation numbers
calculated,
determines either the denomination of the scanned bill or generates a
denomination
error by setting the denomination error flag steps 1760 and 1762). In the case
where
the denomination error flag is set (step 1762), the process is ended (step
1772).
CA 02215853 1997-11-06
'_ _____._._-_. _ _.. _ ___.. __ . _..
JS
Alternatively, if based on this first comparison, the system is able to
determine the
denomination of the scanned bill, the system proceeds to compare the scanned
second
characteristic information with the stored second characteristic information
corresponding to the denomination determined by the first comparison (step
1764).
For example, if as a result of the first comparison the scanned bill is
determined to be a $20 bill, the scanned second characteristic information is
compared to the stored second characteristic information corresponding to a
genuine
$20 bill. In this manner, the system need not make comparisons with stored
second
characteristic information for the other denominations the system is
programmed to
accommodate. If based on this second comparison (step 1764) it is determined
that
the scanned second characteristic information does not sufficiently match that
of the
stored second characteristic information (step 1766), then a second
characteristic
error is generated by setting the second characteristic error flag (step 1768)
and the
process is ended (step 1772). If the second comparison results in a sufficient
match
between the scanned and stored second characteristic information (step 1766),
then
the denomination of the scanned bill is indicated (step 1770) and the process
is ended
(step 1772).
An example of an interrelationship between authentication based on a first and
second characteristic can be seen by considering Table 1. The denomination
determined by optical scanning of a bill is preferably used to facilitate
authentication
of the bill by magnetic scanning, using the relationship set forth in Table 1.
Table 1
Sensitivity 1 2 3 4 5
Denomination
$1 200 250 300 375 450
$2 100 125 150 225 300
$5 200 250 300 350 400
$10 100 125 150 200 250
$20 120 150 180 270 360
CA 02215853 1997-11-06
56
$50 200 250 300 375 450
$100 100 125 150 250 350
Table 1 depicts relative total magnetic content thresholds for various
denominations of genuine bills. Columns 1-5 represent varying degrees of
sensitivity
selectable by a user of a device employing the present invention. The values
in Table
1 are set based on the scanning of genuine bills of varying denominations for
total
magnetic content and setting required thresholds based on the degree of
sensitivity
selected. The information in Table 1 is based on the total magnetic content of
a
genuine $1 being 1000. The following discussion is based on a sensitivity
setting of
4. In this example it is assumed that magnetic content represents the second
characteristic tested. If the comparison of first characteristic information,
such as
reflected light intensity, from a scanned billed and stored information
corresponding
to genuine bills results in an indication that the scanned bill is a $10
denomination,
then the total magnetic content of the scanned bill is compared to the total
magnetic
content threshold of a genuine $10 bill, i.e., 200. If the magnetic content of
the
scanned bill is less than 200, the bill is rejected. Otherwise it is accepted
as a $10
bill.
In order to avoid problems associated with re-feeding bills, counting bills by
hand, and adding together separate totals, according to a preferred embodiment
of the
present invention a number of selection elements associated with individual
denominations are provided. In FIG. 1, these selection elements are in the
form of
keys or buttons of a keypad. Other types of selection elements such as
switches or
displayed keys in a touch-screen environment may be employed. The operation of
the selection elements and several of the operating modes of the discriminator
10 are
described below in conjunction with FIGs. 56 and 59.
Referring now to FIGs. 9-l lb, there are shown flow charts illustrating the
sequence of operations involved in implementing the above-described optical
sensing
and correlation technique. FIGs. 9 and 10, in particular, illustrate the
sequences
involved in detecting the presence of a bill adjacent the scanheads and the
borderlines
on each side of the bill. Turning to FIG. 9, at step 70, the lower scanhead
fine line
CA 02215853 1997-11-06
57
interrupt is initiated upon the detection of the fine line by the lower
scanhead. An
encoder counter is maintained that is incremented for each encoder pulse. The
encoder counter scrolls from 0 - 65,535 and then starts at 0 again. At step 71
the
value of the encoder counter is stored in memory upon the detection of the
fine line
by the lower scanhead. At step 72 the lower scanhead fine line interrupt is
disabled
so that it will not be triggered again during the interrupt period. At step
73, it is
determined whether the magnetic sampling has been completed for the previous
bill.
If it has not, the magnetic total for the previous bill is stored in memory at
step 74
and the magnetic sampling done flag is set at step 75 so that magnetic
sampling of
the present bill may thereafter be performed. Steps 74 and 75 are skipped if
it is
determined at step 73 that the magnetic sampling has been completed for the
previous
bill. At step 76, a lower scanhead bit in the trigger flag is set. ~ This bit
is used to
indicate that the lower scanhead has detected the fine line. The magnetic
sampler is
initialized at step 77 and the magnetic sampling interrupt is enabled at step
78. A
density sampler is initialized at step 79 and a density sampling interrupt is
enabled at
step 80. The lower read data sampler is initialized at step 81 and a lower
scanhead
data sampling interrupt is enabled at step 82. At step 83, the lower scanhead
fme
line interrupt flag is reset and at step 84 the program returns from the
interrupt.
Turning to FIG. 10, at step 85, the upper scanhead fine line interrupt is
initiated upon the detection of the fine line by the upper scanhead. At step
86 the
value of the encoder counter is stored in memory upon the detection of the
fine line
by the upper scanhead. This information in connection with the encoder counter
value associated with the detection of the fine line by the lower scanhead may
then be
used to determine the face orientation of a bill, that is whether a bill is
fed green side
up or green side down in the case of U.S. bills as is described in more detail
below
in connection with FIG. 12. At step 87 the upper scanhead fine line interrupt
is
disabled so that it will not be triggered again during the interrupt period.
At step 88,
the upper scanhead bit in the trigger flag is set. This bit is used to
indicate that the
upper scanhead has detected the fine line. By checking the lower and upper
scanhead
bits in the trigger flag it can be determined whether each side has detected a
respective fine line. Next, the upper scanhead data sampler is initialized at
step 89
and the upper scanhead data sampling interrupt is enabled at step 90. At step
91, the
CA 02215853 1997-11-06
58
upper scanhead fine line interrupt flag is reset and at step 92 the program
returns
from the interrupt.
Referring now to FIGs. lla and llb there are shown, respectively, the
digitizing routines associated with the lower and upper scanheads. FIG. l la
is a flow
chart illustrating the sequential procedure involved in the analog-to-digital
conversion
routine associated with the lower scanhead. The routine is started at step
93a. Next,
the sample pointer is decremented at step 94a so as to maintain an indication
of the
number of samples remaining to be obtained. The sample pointer provides an
indication of the sample being obtained and digitized at a given time. At step
95a,
the digital data corresponding to the output of the photodetector associated
with the
lower scanhead for the current sample is read. The data is convened to its
final form
at step 96a and stored within a pre-defined memory segment as XIN_~, at step
97a.
Next, at step 98a, a check is made to see if the desired fixed number of
samples "N" has been taken. if the answer is found to be negative, step 99a is
accessed where the interrupt authorizing the digitization of the succeeding
sample is
enabled and the program returns from interrupt at step 100a for completing the
rest
of the digitizing process. However, if the answer at step 98a is.found to be
positive,
i.e. , the desired number of samples have already been obtained, a flag,
namely the
lower scanhead done flag bit, indicating the same is set at step lOla and the
program
returns from interrupt at step 102a.
FIG. l lb is a flow chart illustrating the sequential procedure involved in
the
analog-to-digital conversion routine associated with the upper scanhead. The
routine
is started at step 93b. Next, the sample pointer is decremented at step 94b so
as to
maintain an indication of the number of samples remaining to be obtained. The
sample pointer provides an indication of the sample being obtained and
digitized at a
given time. At step 95b, the digital data corresponding to the output of the
photodetector associated with the upper scanhead for the current sample is
read. The
data is converted to its final form at step 96b and stored within a pre-
defined memory
segment as Xirr-U at step 97b.
Next, at step 98b, a check is made to see if the desired fixed number of
samples "N" has been taken. If the answer is found to be negative, step 99b is
accessed where the interrupt authorizing the digitization of the succeeding
sample is
CA 02215853 1997-11-06
59
enabled and the program returns from interrupt at step 100b for completing the
rest
of the digitizing process. However, if the answer at step 98b is found to be
positive,
i.e., the desired number of samples have already been obtained, a flag, namely
the
upper scanhead done flag bit, indicating the same is set at step lOlb and the
program
returns from interrupt at step 102b.
The CPU 30 is programmed with the sequence of operations in FIG. 12 to
correlate at least initially only the test pattern corresponding to the green
surface of a
scanned bill. As shown in FIGs. 6c-6d, the upper scanhead 18a is located
slightly
upstream adjacent the bill transport path relative to the lower scanhead i8b.
The
distance between the scanheads IBa, 18b in a direction parallel to the
transport path
corresponds to a predetermined number of encoder counts. It should be
understood
that the encoder 32 produces a repetitive tracking signal synchronized with
incremental movements of the bill transport mechanism, and this repetitive
tracking
signal has a repetitive sequence of counts (e.g., 65,535 counts) associated
therewith.
As a bill is scanned by the upper and lower scanheads 18a, 18b, the CPU 30
monitors the output of the upper scanhead 18a to detect the borderline of a
first bill
surface facing the upper scanhead 18a. Once this borderline of .the first
surface is
detected, the CPU 30 retrieves and stores a first encoder count in memory.
Similarly, the CPU 30 monitors the output of the lower scanhead 18b to detect
the
borderline of a second bill surface facing the lower scanhead 18b. Once the
borderline of the second surface is detected, the CPU 30 retrieves and stores
a second
encoder count in memory.
Referring to FIG. 12, the CPU 30 is programmed to calculate the difference
between the first and second encoder counts (step lOSa). If this difference is
greater
than the predetermined number of encoder counts corresponding to the distance
between the scanheads 18a, 18b plus some safety factor number "X", e.g., 20
(step
106), the bill is oriented with its black surface facing the upper scanhead
18a and its
green surface facing the lower scanhead 18b. This can best be understood by
reference to FIG. 6c which shows a bill with the foregoing orientation. In
this
situation, once the borderline B, of the black surface passes beneath the
upper
scanhead 18a and the first encoder count is stored, the borderline BZ still
must travel
for a distance greater than the distance between the upper and lower scanheads
18a,
CA 02215853 1997-11-06
18b in order to pass over the lower scanhead 18b. As a result, the difference
between the second encoder count associated with the borderline BZ and the
first
encoder count associated with the borderline BI will be greater than the
predetermined number of encoder counts corresponding to the distance between
the
5 scanheads 18a, 18b. With the bill oriented with its green surface facing the
lower
scanhead, the CPU 30 sets a flag to indicate that the test pattern produced by
the
lower scanhead 18b should be correlated (step 107). Next, this test pattern is
correlated with the green-side master characteristic patterns stored in memory
(step
109).
10 if at step 106 the difference between the first and second encoder counts
is
less than the predetermined number of encoder counts corresponding to the
distance
between the scanheads 18a, 18b, the CPU 30 is programmed to determine whether
the difference between the first and second encoder counts is less than the
predetermined number minus some safety number "X", e.g., 20 (step 108). If the
15 answer is negative, the orientation of the bill relative to the scanheads
i8a, 18b is
uncertain so the CPU 30 is programmed to correlate the test patterns produced
by
both the upper and lower scanheads 18a, 18b with the green-side master
characteristic
patterns stored in memory (steps 109, 110, and 111).
If the answer is affirmative, the bill is oriented with its green surface
facing
20 the upper scanhead 18a and its black surface facing the lower scanhead 18b.
This
can best be understood by reference to FIG. 6d, which shows a bill with the
foregoing orientation. In this situation, once the borderline BZ of the green
surface
passes beneath the upper scanhead 18a and the first encoder count is stored,
the
borderline B1 must travel for a distance less than the distance between the
upper and
25 lower scanheads 18a, 18b in order to pass over the lower scanhead 18b. As a
result,
the difference between the second encoder count associated with the borderline
B1 and
the first encoder count associated with the borderline BZ should be less than
the
predetermined number of encoder counts corresponding to the distance between
the
scanheads 18a, 18b. To be on the safe side, it is required that the difference
between
30 first and second encoder counts be less than the predetermined number minus
the
safety number "X". Therefore, the CPU 30 is programmed to correlate the test
CA 02215853 1997-11-06
61
pattern produced by the upper scanhead 18a with the green-side master
characteristic
patterns stored in memory (step 111).
After correlating the test pattern associated with either the upper scanhead
18a, the lower scanhead 18b, or both scanheads 18a, 18b, the CPU 30 is
programmed to perform the bi-level threshold check (step 112).
A simple correlation procedure is utilized for processing digitized
reflectance
values into a form which is conveniently and accurately compared to
corresponding
values pre-stored in an identical format. More specifically, as a first step,
the mean
value X for the set of digitized reflectance samples (comparing "n" samples)
obtained
for a bill scan run is first obtained as below:
X. (1)
X= ~ -'
i=0 n
Subsequently, a normalizing factor Sigma ("a") is determined as being
equivalent to the sum of the square of the difference between each sample and
the
mean, as normalized by the total number n of samples. More specifically, the
normalizing factor is calculated as below:
n IXa_XIz l2)
a = E
i=0 n .
In the final step, each reflectance sample is normalized by obtaining the
difference between the sample and the above-calculated mean value and dividing
it by
the square root of the normalizing factor v as defined by the following
equation: '
X1 X (3)
Xn ( Q )'/z
CA 02215853 1997-11-06
62
The result of using the above correlation equations is that, subsequent to the
normalizing process, a relationship of correlation exists between a test
pattern and a
master pattern such that the aggregate sum of the products of corresponding
samples
in a test pattern and any master pattern, when divided by the total number of
S samples, equals unity if the patterns are identical. Otherwise, a value less
than unity
is obtained. Accordingly, the correlation number or factor resulting from the
comparison of normalized samples within a test pattern to those of a stored
master
pattern provides a clear indication of the degree of similarity or correlation
between
the two patterns.
According to a preferred embodiment of this invention, the fixed number of
reflectance samples which are digitized and normalized for a bill scan is
selected to
be 64. It has experimentally been found that the use of higher binary orders
of
samples (such as 128, 256, etc.) does not provide a correspondingly increased
discrimination efficiency relative to the increased processing time involved
in
implementing the above-described correlation procedure. It has also been found
that
the use of a binary order of samples lower than 64, such as 32, produces a
substantial
drop in discrimination efficiency.
The correlation factor can be represented conveniently in binary terms for
ease of correlation. In a preferred embodiment, for instance, the factor of
unity
which results when a hundred percent correlation exists is represented in
terms of the
binary number 2'°, which is equal to a decimal value of 1024. Using the
above
procedure, the normalized samples within a test pattern are compared to the
master
characteristic patterns stored within the system memory in order to determine
the
particular stored pattern to which the test pattern corresponds most closely
by
identifying the comparison which yields a correlation number closest to 1024.
A bi-level threshold of correlation is required to be satisfied before a
particular call is made, for at least certain denominations of bills. More
specifically,
the correlation procedure is adapted to identify the two highest correlation
numbers
resulting from the comparison of the test pattern to one of the stored
patterns. At
that point, a minimum threshold of correlation is required to be satisfied by
these two
correlation numbers. It has experimentally been found that a correlation
number of
about 850 serves as a good cut-off threshold above which positive calls may be
made
CA 02215853 1997-11-06
63
with a high degree of confidence and below which the designation of a test
pattern as
corresponding to any of the stored patterns is uncertain. As a second
threshold level,
a minimum separation is prescribed between the two highest correlation numbers
before making a call. This ensures that a positive call is made only when a
test
pattern does not correspond, within a given range of correlation, to more than
one
stored master pattern. Preferably, the minimum separation between correlation
numbers is set to be 150 when the highest correlation number is between 800
and
850. When the highest correlation number is below 800, no call is made.
The procedure involved in comparing test patterns to master patterns is
discussed below in connection with FIG. 18a.
Next a routine designated as "CORRES" is initiated. The procedure involved
in executing the routine CORRES is illustrated at FIG. 13 which shows the
routine as
starting at step 114. Step 115 determines whether the bill has been identified
as a $2
bill, and, if the answer is negative, step i 16 determines whether the best
correlation
number ("call #1 ") is greater than 799. If the answer is negative, the
correlation
number is too low to identify the denomination of the bill with certainty, and
thus
step 117 generates a "no call" code. A "no call previous bill" flag is then
set at step
118, and the routine returns to the main program at step 119.
An affirmative answer at step 116 advances the system to step 120, which
determines whether the sample data passes an ink stain test (described below).
If the
answer is negative, a "no call" code is generated at step 117. If the answer
is
affirmative, the system advances to step 121 which determines whether the best
correlation number is greater than 849. An affirmative answer at step 121
indicates
that the correlation number is sufficiently high that the denomination of the
scanned
bill can be identified with certainty without any further checking.
Consequently, a
"denomination" code identifying the denomination represented by the stored
pattern
resulting in the highest correlation number is generated at step 122, and the
system
returns to the main program at step 119.
A negative answer at step 121 indicates that the correlation number is between
800 and 850. It has been found that correlation numbers within this range are
sufficient to identify all bills except the $2 bill. Accordingly, a negative
response at
step 121 advances the system to step 123 which determines whether the
difference
CA 02215853 1997-11-06
between the two highest correlation numbers ("call #1" and "call #2") is
greater than
149. If the answer is affirmative, the denomination identified by the highest
correlation number is acceptable, and thus the "denomination" code is
generated at
step 122. If the difference between the two highest correlation numbers is
less than
150, step 123 produces a negative response which advances the system to step
117 to
generate a "no call" code.
Returning to step 115, an affirmative response at this step indicates that the
initial call is a $2 bill. This affirmative response initiates a series of
steps 124-127
which are identical to steps 116, 120, 121 and 123 described above, except
that the
numbers 799 and 849 used in steps 116 and 121 are changed to 849 and 899,
respectively, in steps 124 and 126. The result is either the generation of a
"no call"
code at step 117 or the generation of a $2 "denomination" code at step 122.
One problem encountered in currency recognition and counting systems is the
difficulty involved in interrupting {for a variety of reasons) and resuming
the
scanning and counting procedure as a stack of bills is being scanned. If a
particular
currency recognition unit (CRU) has to be halted in operation due to a "major"
system error, such as a bill being jammed along the transport path, there is
generally
no concern about the outstanding transitional status of the overall
recognition and
counting process. However, where the CRU has to be halted due to a "minor"
error,
such as the identification of a scanned bill as being a counterfeit (based on
a variety
of monitored parameters) or a "no call" (a bill which is not identifiable as
belonging
to a specific currency denomination based on the plurality of stored master
patterns
and/or other criteria), it is desirable that the transitional status of the
overall
recognition and counting process be retained so that the CRU may be restarted
without any effective disruptions of the recognition/counting process.
More specifically, once a scanned bill has been identified as a "no call" bill
(B,) based on some set of predefined criteria, it is desirable that this bill
B, be
transported directly to the system stacker and the CRU brought to a halt with
bill Bl
being the last bill deposited in the output receptacle, while at the same time
ensuring
that the following bills are maintained in positions along the bill transport
path
whereby CRU operation can be conveniently resumed without any disruption of
the
recognition/counting process.
CA 02215853 1997-11-06
Since the bill processing speeds at which currency recognition systems must
operate are substantially high (speeds of the order of 800 to 1500 bills per
minute), it
is practically impossible to totally halt the system following a "no call"
without the
following bill BZ already overlapping the optical scanhead and being partially
5 scanned. As a result, it is virtually impossible for the CRU system to
retain the
transitional status of the recognitionlcounting process (particularly with
respect to bill
BZ) in order that the process may be resumed once the bad bill B1 has been
transported to the stacker, conveniently removed therefrom, and the system
restarted.
The basic problem is that if the CRU is halted with bill BZ only partially
scanned, it
10 is difficult to reference the data reflectance samples extracted therefrom
in such a
way that the scanning may be later continued (when the CRU is restarted) from
exactly the same point where the sample extraction process was interrupted
when the
CRU was stopped.
Even if an attempt were made at immediately halting the CRU system
15 following a "no call, " any subsequent scanning of bills would be totally
unreliable
because of mechanical backlash effects and the resultant disruption of the
optical
encoder routine used for bill scanning. Consequently, when the CRU is
restarted, the
call for the following bill is also likely to be bad and the overall
recognition/counting
process is totally disrupted as a result of an endless loop of "no calls. "
20 The above problems are solved by the use of a currency detecting and
counting technique whereby a scanned bill identified as a "no call" is
transported
directly to the top of the system stacker and the CRU is halted without
adversely
affecting the data collection and processing steps for a succeeding bill.
Accordingly,
when the CRU is restarted, the overall bill recognition and counting procedure
can be
25 resumed without any disruption as if the CRU had never been halted at all.
According to a preferred technique, if the bill is identified as a "no call"
based on any of a variety of conventionally defined bill criteria, the CRU is
subjected
to a controlled deceleration process whereby the speed at which bills are
moved
across the scanhead is reduced from the normal operating speed. During this
30 deceleration process the "no call" bill (B1) is transported to the top of
the stacker and,
at the same time, the following bill B2 is subjected to the standard scanning
procedure in order to identify the denomination.
CA 02215853 1997-11-06
fib
The rate of deceleration is such that optical scanning of bill BZ is completed
by the time the CRU operating speed is reduced to a .predefined operating
speed.
While the exact operating speed at the end of the scanning of bill BZ is not
critical,
the objective is to permit complete scanning of bill B~ without subjecting it
to
backlash effects that would result if the ramping were too fast, while at the
same time
ensuring that bill B, has in fact been transported to the stacker.
It has been experimentally determined that at nominal operating speeds of the
order of 1000 bills per minute, the deceleration is preferably such that the
CRU
operating speed is reduced to about one-fifth of its normal operating speed at
the end
of the deceleration phase, i.e., by the time optical scanning of bill BZ has
been
completed. It has been determined that at these speed levels, positive calls
can be
made as to the denomination of bill B2 based on reflectance samples gathered
during
the deceleration phase with a relatively high degree of certainty (i.e., with
a
correlation number exceeding about 850).
Once the optical scanning of bill B, has been completed, the speed is reduced
to an even slower speed until the bill BZ has passed bill-edge sensors S1 and
S2
described below, and the bill B2 is then brought to a complete stop. At the
same
time, the results of the processing of scanned data corresponding to bill Bz
are stored
in system memory. The ultimate result of this stopping procedure is that the
CRU is
brought to a complete halt following the point where the scanning of bill B2
has been
reliably completed, and the scan procedure is not subjected to the disruptive
effects
(backlash, etc.) which would result if a complete halt were attempted
immediately
after bill B1 is identified as a "no call."
The reduced operating speed of the machine at the end of the deceleration
phase is such that the CRU can be brought to a total halt before the next
following
bill B3 has been transported over the optical scanhead. Thus, when the CRU is
in
fact halted, bill B1 is positioned at the top of the system stacker, bill BZ
is maintained
in transit between the optical scanhead and the stacker after it has been
subjected to
scanning, and the following bill B3 is stopped short of the optical scanhead.
When the CRU is restarted, presumably after corrective action has been taken
in response to the "minor" error which led to the CRU being stopped (such as
the
removal of the "no call" bill from the output receptacle), the overall
scanning
CA 02215853 1997-11-06
67
operation can be resumed in an uninterrupted fashion by using the stored call
results
for bill BZ as the basis for updating the system count appropriately, moving
bill B2
from its earlier transitional position along the transport path into the
stacker, and
moving bill B3 along the transport path into the optical scanhead area where
it can be
subjected to normal scanning and processing. A routine for executing the
deceleration/stopping procedure described aoove is illustrated by the flow
chart in
FIG. 14. This routine is initiated at step 170 with the CRU in its normal
operating
mode. At step 171, a test bill B1 is scanned and the data reflectance samples
resulting therefrom are processed. Next, at step 172, a determination is made
as to
whether or not test bill B, is a "no call" using predefined criteria in
combination with
the overall bill recognition procedure, such as the routine of FIG. 13. If the
answer
at step 172 is negative, i.e., the test bill B, can be identified, step 173 is
accessed
where normal bill processing is continued in accordance with the procedures
described above. If, however, the test bill B1 is found to be a "no call" at
step 172,
step 174 is accessed where CRU deceleration is initiated, e.g., the transport
drive
motor speed is reduced to about one-fifth its normal speed.
Subsequently, the "no call" bill B1 is guided to the stacker while, at the
same
time, the following test bill B2 is brought under the optical scanhead and
subjected to
the scanning and processing steps. The call resulting from the scanning and
processing of bill BZ is stored in system memory at this point. Step 175
determines
whether the scanning of bill BZ is complete. When the answer is negative, step
176
determines whether a preselected "bill timeout" period has expired so that the
system
does not wait for the scanning of a bill that is not present. An affirmative
answer at
step 176 results in the transport drive motor being stopped at step 179 while
a
negative answer at step 176 causes steps 175 and 176 to be reiterated until
one of
them produces an affirmative response.
After the scanning of bill Bz is complete and before stopping the transport
drive motor, step 178 determines whether either of the sensors S 1 or S2
(described
below) is covered by a bill. A negative answer at step 178 indicates that the
bill has
cleared both sensors S 1 and S2, and thus the transport drive motor is stopped
at step
179. This signifies the end of the deceleration/stopping process. At this
point in
CA 02215853 1997-11-06
68
time, bill B~ remains in transit while the following bill B3 is stopped on the
transport
path just short of the optical scanhead.
Following step 179, corrective action responsive to the identification of a
"no
call" bill is conveniently undertaken; the top-most bill in the slacker is
easily
removed therefrom and the CRU is then in condition for resuming the scanning
process. Accordingly, the CRU can be restarted and the stored results
corresponding
to bill B2, are used to appropriately update the system count. Next, the
identified bill
BZ is guided along the transport path to the slacker, and the CRU continues
with its
normal processing routine. While the above deceleration process has been
described
in a context of a "no call" error, ether minor errors (e.g., suspect bills,
stranger bills
in stranger mode, etc.) are handled in the same manner.
In currency discrimination systems in which discrimination is based on the
comparison of a pattern obtained from scanning a subject bill to stored master
patterns corresponding to various denominations, the patterns which are
designated as
master patterns significantly influence the performance characteristics of a
discrimination system. For example, in the system described in United States
Patent
No. 5,295,196, the correlation procedure and the accuracy with. which a
denomination is identified directly relates to the degree of correspondence
between
reflectance samples on the test pattern and corresponding samples on the
stored
master patterns. in other systems, master patterns have been produced by
scanning a
genuine bill for a given denomination and storing the resulting pattern as the
master
pattern for that denomination. However, due to variations among genuine bills,
this
method is likely to result in poor performance of the discrimination system by
rejecting an unacceptable number of genuine bills. It has been found that the
relative
crispness,. age, shrinkage, usage, and other characteristics of a genuine bill
can effect
the resulting pattern generated by scanning. These factors are often
interrelated. For
example, it has been found that currency bills which have experienced a high
degree
of usage exhibit a reduction in both the narrow and wide dimensions of the
bills.
This shrinkage of "used" bills which, in turn, causes corresponding reductions
in
their narrow dimensions, can possibly produce a drop in the degree of
correlation
between such used bills of a given denomination and the corresponding master
patterns.
CA 02215853 1997-11-06
69
As a result, a discrimination system which generates a master pattern based on
a single scan of a genuine bill is not likely to perform satisfactorily. For
example, if
the $20 master pattern is generated by scanning a crisp, genuine $20 bill, the
discrimination system may reject an unacceptable number of genuine but worn
$20
bills. Likewise, if the $20 master pattern is generated using a very worn,
genuine
$20 bill, the discrimination system may reject an unacceptable number of
genuine but
crisp $20 bills,
According to a preferred embodiment of the present invention, a master
pattern for a given denomination is generated by averaging a plurality of
component
patterns. Each component pattern is generated by scanning a genuine bill of
the
given denomination.
According to a first method, master patterns are generated by scanning a
standard bill a plurality of times, typically three (3) times, and obtaining
the average
of corresponding data samples before storing the average as representing a
master
pattern. In other words, a master pattern for a given denomination is
generated by
averaging a plurality of component patterns, wherein all of the component
patterns
are generated by scanning a single genuine bill of "standard" quality of the
given
denomination. The "standard" bill is a slightly used bill, as opposed to a
crisp new
bill or one which has been subject to a high degree of usage. Rather, the
standard
bill is a bill of good to average quality. Component patterns generated
according to
this first methods are illustrated in FIGS. 15a-15c. More specifically, FIGS.
15a-15c
show three test patterns generated, respectively, for the forward scanning of
a $1 bill
along its green side, the reverse scanning of a $2 bill on its green side, and
the
forward scanning of a $100 bill on its green side. It should be noted that,
for
purposes of clarity the test patterns in FIGS. 15a-15c were generated by using
128
reflectance samples per bill scan, as opposed to the preferred use of only 64
samples.
The marked difference existing among corresponding samples for these three
test
patterns is indicative of the high degree of confidence with which currency
denominations may be called using the foregoing optical sensing and
correlation
procedure.
According to a second method, a master pattern for a given denomination is
generated by scanning two yr more standard bills of standard quality and
obtaining a
CA 02215853 1997-11-06
plurality of component patterns. These component patterns are then averaged in
deriving a master pattern. For example, it has been found that some genuine $5
bills
have dark stairs on the Lincoln Memorial while other genuine $5 bills have
light
stairs. To compensate for this variation, standard bills for which component
patterns
are derived may be chosen with at least one standard bill scanned having dark
stairs
and with at least one standard bill having light stairs.
It has been found that an alternate method can lead to improved performance
in a discrimination systems, especially with regards to certain denominations.
For
example, it has been found that the printed indicia on a $10 bill has changed
slightly
with 1990 series bills incorporating security threads. More specifically, 1990
series
$10 bills have a borderline-to-borderline dimension which is slightly greater
than
previous series $10 bills. Likewise it has been found that the scanned pattern
of an
old, semi-shrunken $5 bill can differ significantly from the scanned pattern
of a new
$5 bill.
According to a third method, a master pattern for a given denomination is
generated by averaging a plurality of component patterns, wherein some of the
component patterns are generated by scanning one or more new bills of the
given
denomination and some of the component patterns are generated by scanning one
or
more old bills of the given denomination. New bills are bills of good quality
which
have been printed in recent years and have a security thread incorporated
therein (for
those denominations in which security threads are placed). New bills are
preferably
relatively crisp. A new $10 bill is preferably a 1990 series or later bill of
very high
quality, meaning that the bill is in near mint condition. Old bills are bills
exhibiting
some shrinkage and often some discoloration. Shrinkage may result from a bill
having been subjected to a relatively high degree of use. A new bill utilized
in this
third method is of higher quality than a standard bill of the previous
methods, while
an old bill in this third method is of lower quality than a standard bill.
The third method can be understood by considering Table 2 which summarizes
the manner in which component patterns are generated for a variety of
denominations.
CA 02215853 1997-11-06
71
Table 2. Component Scans by Denomination
Denomination Scan DirectionCPl CP2 CP3
$1 Forward -0.2 std 0.0 std +0.2 std
$1 Reverse -0.2 std 0.0 std +0.2 std
$2, left Forward -0.2 std -0.15 std -0.1 std
$2, left Reverse -0.2 std -0.15 std -0.1 std
$2, right Forward 0.0 std +0.1 std +0.2 std
$2, right Reverse 0.0 std +0.1 std +0.2 std
$5 Forward -0.2 old 0.0 new +0.2 old
(It str) (dk str) (lt str)
$5 Reverse -0.2 old 0.0 new +0.2 old
(It str) (dk str) (lt str)
$10, left Forward -0.2 old -0.1 new 0.0 old
$I0, left Reverse 0.0 old +0.1 new +0.2 old
$10, right Forward +0.1 old +0.2 new +0.3 old
$10, right Reverse -0.2 old -0.15 new -0.1 old
$20 Forward -0.2 old 0.0 new +0.2 old
$20 Reverse -0.2 old 0.0 new +0.2 old
$SO Forward -0.2 std 0.0 std +0.2 std
$50 Reverse ~ -0.2 std 0.0 std +0.2 std
$100 Forward -0.2 std 0.0 std +0.2 std
$100 Reverse -0.2 std 0.0 std +0.2 std
Table 2 summarizes the position of the scanhead relative to the center of the
green surface of United States currency as well as the type of bill to be
scanned for .
generating component patterns for various denominations. The three component
patterns ("CP") for a given denomination and for a given scan direction are
averaged
to yield a corresponding master pattern. The eighteen (18) rows correspond to
the
preferred method of storing eighteen ( 18) master patterns. The scanhead
position is
CA 02215853 1997-11-06
indicated relative to the center of the borderlined area of the bill. Thus a
position of
"0.0" indicates that the scanhead is centered over the center of the
borderlined area
of the bill. Displacements to the left of center are indicated by negative
numbers,
while displacements to the right are indicated by positive numbers. Thus a
position
of "-0.2" indicates a displacement of 2/l0ths of an inch to the left of the
center of a
bill, while a position of "+0.1" indicates a displacement of l/lOths of an
inch to the
right of the center of a bill.
Accordingly, Table 2 indicates that component patterns for a $20 bill scanned
in the forward direction are obtained by scanning an old $20 bill 2/lOths of a
inch to
the right and to the left of the center of the bill and by scanning a new $20
bill
directly down the center of the bill. FIG. 15d is a graph illustrating these
three
patterns. These three patterns are then averaged to obtain the master pattern
for a
$20 bill scanned in the forward direction. FIG. 15e is a graph illustrating an
pattern
for a $20 bill scanned in the forward direction derived by averaging the
patterns of
FIG. 15d. This pattern becomes the corresponding $20 master pattern after
undergoing normalization. In generating the master patterns, one may use a
scanning
device in which a bill to be scanned is held stationary and a scanhead is
moved over
the bill. Such a device permits the scanhead to be moved laterally, left and
right,
over a bill to be scanned and thus permits the scanhead to be positioned over
the area
of the bill which one wishes to scan, for example, 2/lOths of inch to the left
of the
center of the borderlined area.
As discussed above, for $i0 bills two patterns are obtained in each scan
direction with one pattern being scanned slightly to the left of the center
and one
pattern being scanned slightly to the right of the center. For $5 bills, it
has been
found that some $5 bills are printed with darker stairs ("dk str") on the
picture of the
Lincoln Memorial while others are printed with lighter stairs ("lt str"). The
effect of
this variance is averaged out by using an old bill having light stairs and a
new bill
having dark stairs.
As can be seen from Table 2, for some bills, the third method of using oid
and new bills is not used; rather, a standard ("std") bill is used for
generating all
three component patterns as with the first method. Thus, the master pattern
for a $1
bill scanned in the forward direction is obtained by averaging three component
CA 02215853 1997-11-06
73
patterns generated by scanning a standard bill three times, once 2/l0ths of an
inch to
the left, once down the center, and once 2/ lOths of an inch to the right.
As illustrated by Table 2, a discrimination system may employ a combination
of the developed methods of this invention wherein, for example, some master
patterns are generated according the first method and some master patterns are
generated according to the third method. Likewise, a discrimination system may
combine the scanning of new, standard, and old bills to generate component
patterns
to be averaged in obtaining a master pattern. Additionally, a discrimination
system
may generate master patterns by scanning bills of various qualities and/or
having
various characteristics and then averaging the resultant patterns.
Alternatively, a
discrimination system may scan multiple bills of a given quality for a given
denomination, e.g., three new $50 bills, while scanning one or more bills of a
different quality for a different denomination, e.g., three old and worn $1
bills, to
generate component patterns to be averaged in obtaining master patterns.
The optical sensing and correlation technique described above permits
identification of pre-programmed currency denominations with a high degree of
accuracy and is based upon a relatively low processing time for digitizing
sampled
reflectance values and comparing them to the master characteristic patterns.
The
approach is used to scan currency bills, normalize the scanned data and
generate
master patterns in such a way that bill scans during operation have a direct
correspondence between compared sample points in portions of the bills which
possess the most distinguishable printed indicia. A relatively low number of
reflectance samples is required in order to be able to adequately distinguish
among
several currency denominations.
An advantage with this approach is that it is not required that currency bills
be
scanned along their wide dimensions. Further, the reduction in the number of
samples reduces the processing time to such an extent that additional
comparisons can
be made during the time available between the scanning of successive bills.
More
specifically, as described above, it becomes possible to compare a test
pattern with
multiple stored master characteristic patterns so that the system is made
capable of
identifying currency which is scanned in the "forward" or "reverse" directions
along
the green surface of the bill.
CA 02215853 1997-11-06
74
Another advantage accruing from the reduction in processing time realized by
the preferred sensing and correlation scheme is that the response time
involved in
either stopping the transport of a bill that has been identified as
"spurious", i.e., not
corresponding to any of the stored master characteristic patterns, or
diverting such a
bill to a separate stacker bin, is correspondingly shortened. Accordingly, the
system
can conveniently be programmed to set a flag when a scanned pattern does not
correspond to any of the master patterns. The identification of such a
condition can
be used to stop the bill transport drive motor for the mechanism. Since the
optical
encoder is tied to the rotational movement of the drive motor, synchronism can
be
maintained between pre- and post-stop conditions.
The correlation procedure and the accuracy with which a denomination is
identified directly relates to the degree of correspondence between
reflectance
samples on the test pattern and corresponding samples on the stored master
patterns.
Thus, shrinkage of "used" bills which, in turn, causes corresponding
reductions in
both their narrow and wide dimensions, can possibly produce a drop in the
degree of
correlation between such used bills of a given denomination and the
corresponding
master patterns. Currency bills which have experienced a high degree of usage
exhibit such a reduction in both the narrow and wide dimensions of the bills.
While
the illustrated sensing and correlation technique remains relatively
independent of any
changes in the non-preselected dimension of bills, reduction along the
preselected
dimension can affect correlation factors by realizing a relative displacement
of
reflectance samples obtained as the "shrunk" bills are transported across the
scanhead. Thus, if the bills are transported and scanned along their wide
dimension,
the sensing and correlation technique will remain relatively independent of
any
changes in the narrow dimension of bills and reduction along the wide
dimension can
affect correlation factors. Similarly, if the bills are transported and
scanned along
their narrow dimension, the sensing and correlation technique will remain
relatively
independent of any changes in the wide dimension of bills and reduction along
the
narrow dimension can affect correlation factors.
In order to accommodate or nullify the effect of such bill shrinking, the
above-described correlation technique can be modified by use of a progressive
shifting approach whereby a test pattern which does not correspond to any of
the
CA 02215853 1997-11-06
master patterns is partitioned into predefined sections, and samples in
successive
sections are progressively shifted and compared again to the stored patterns
in order
to identify the denomination. It has experimentally been determined that such
progressive shifting effectively counteracts any sample displacement resulting
from
5 shrinkage of a bill along the preselected dimension.
The progressive shifting effect is best illustrated by the correlation
patterns
shown in FIGs. 16a-e. For purposes of clarity, the illustrated patterns were
generated using 128 samples for each bill scan as compared to the preferred
use of 64
samples. FIG. 16a shows the correlation between a test pattern (represented by
a
10 heavy line) and a corresponding master pattern (represented by a thin
line). It is
clear from FIG. 16a that the degree of correlation between the two patterns is
relatively low and exhibits a correlation factor of 606.
The manner in which the correlation between these patterns is increased by
employing progressive shifting is best illustrated by considering the
correlation at the
15 reference points designated as A-E along the axis defining the number of
samples.
The effect on correlation produced by "single" progressive shifting is shown
in FIG.
16b which shows "single" shifting of the test pattern of FIG. 16a. This is
effected by
dividing the test pattern into two equal segments each comprising 64 samples.
The
first segment is retained without any shift, whereas the second segment is
shifted by a
20 factor of one data sample. Under these conditions, it is found that the
correlation
factor at the reference points located in the shifted section, particularly at
point E, is
improved.
FIG. 16c shows the effect produced by "double" progressive shifting whereby
sections of the test pattern are shifted in three stages. This is.
accomplished by
25 dividing the overall pattern into three approximately equal sized sections.
Section
one is not shifted, section two is shifted by one data sample (as in FIG.
16b), and
section three is shifted by a factor of two data samples. With "double"
shifting, it
can be seen that the correlation factor at point E is further increased.
On a similar basis, FIG. 16d shows the effect on correlation produced by
30 "triple" progressive shifting where the overall pattern is first divided
into four (4)
approximately equal sized sections. Subsequently, section one is retained
without any
shift, section two is shifted by one data sample, section three is shifted by
two data
CA 02215853 1997-11-06
76
samples, and section four is shifted by three data samples. Under these
conditions,
the correlation factor at point E is seen to have increased again.
FIG. 16e shows the effect on correlation produced by "quadruple" shifting,
where the pattern is first divided into five (5) approximately equal sized
sections.
The first four (4) sections are shifted in accordance with the "triple"
shifting
approach of FIG. 16d, whereas the fifth section is shifted by a factor of four
(4) data
samples. From FIG. 16e it is clear that the correlation at point E is
increased almost
to the point of superimposition of the compared data samples.
In an alternative progressive shifting approach, the degree of shrinkage of a
scanned bill is determined by comparing the length of the scanned bill, as
measured
by the scanhead, with the length of an "unshrunk" bill. This "unshrunk" length
is
pre-stored in the system memory. The type of progressive shifting, e.g.,
"single",
"double", "triple", etc., applied to the test pattern is then directly based
upon the
measured degree of shrinkage. The greater the degree of shrinkage, the greater
the
number of sections into which the test pattern is divided. An advantage of
this
approach is that only one correlation factor is calculated, as opposed to
potentially
calculating several correlation factors for different types of progressive
shifting.
In yet another progressive shifting approach, instead of applying progressive
shifting to the test pattern, progressive shifting is applied to each of the
master
patterns. The master patterns in the system memory are partitioned into
predefined
sections, and samples in successive sections are progressively shifted and
compared
again to the scanned test pattern in order to identify the denomination. To
reduce the
amount of processing time, the degree of progressive shifting which should be
applied to the master patterns may be determined by first measuring the degree
of
shrinkage of the scanned bill. By first measuring the degree of shrinkage,
only one
type of progressive shifting is applied to the stored master patterns.
Instead of rearranging the scanned test pattern or the stored master patterns,
the system memory may contain pre-stored patterns corresponding to various
types of .
progressive shifting. The scanned test pattern is then compared to all of
these stored
patterns in the system memory. However, to reduce the time required for
processing
the data, this approach may be modified to first measure the degree of
shrinkage and
CA 02215853 1997-11-06
77
to then select only those stored patterns from the system memory which
correspond
to the measure degree of shrinkage for comparison with the scanned test
pattern.
The advantage of using the progressive shifting approach, as opposed to
merely shifting by a set amount of data samples across the overall test
pattern, is that
the improvement in correlation achieved in the initial sections of the pattern
as a
result of shifting is not neutralized or offset by any subsequent shifts in
the test
pattern. It is apparent from the above figures that the degree of correlation
for
sample points falling within the progressively shifted sections increases
correspondingly.
More importantly, the progressive shifting realizes substantial increases in
the
overall correlation factor resulting from pattern comparison. For instance,
the
original correlation factor of 606 (FIG. 16a) is increased to 681 by the
"single"
shifting shown in FIG. 16b. The "double" shifting shown in FIG. 16c increases
the
correlation number to 793, the "triple" shifting of FIG. 16d increases the
correlation
number to 906, and, finally, the "quadruple" shifting shown in FIG. 16e
increases
the overall correlation number to 960. Using the above approach, it has been
determined that used currency bills which exhibit a high degree _of shrinkage
and
which cannot be accurately identified as belonging to the correct currency
denomination when the correlation is performed without any shifting, can be
identified with a high degree of certainty by using progressive shifting
approach,
preferably by adopting "triple" or "quadruple" shifting.
In currency discrimination systems in which discrimination is based on the
comparison of a pattern obtained from scanning a subject bill to stored master
patterns corresponding to various denominations, the patterns .which are
compared to
each other significantly influence the performance characteristics of a
discrimination
system. For example, in the system described in United States Patent No.
5,295,196, the correlation procedure and the accuracy with which a
denomination is
identified directly relates to the degree of correspondence between
reflectance
samples on the test pattern and corresponding samples on the stored master
patterns.
In accordance with method described above, the identity of a bill under test
is
determined by comparing a scanned pattern generated by scanning the bill under
test
with one or more master patterns associated with genuine bills. If the scanned
CA 02215853 1997-11-06
7$
pattern sufficiently correlates to one of the master pattern, the identity of
the bill may
be called. The process of identifying a bill under test may be subjected;ro a
bi-level
threshold test as described above.
However, the degree of correlation between a scanned and a master pattern
may be negatively impacted if the two patterns are not properly aligned with
each
other. Such misalignment between patterns may in turn negatively impact upon
the
performance of a currency identification system. Misalignment between patterns
may
result from a number of factors. For example, if a system is designed so that
the
scanning process is initiated in response to the detection of the thin
borderline
surrounding U.S. currency or the detection of some other printed indicia such
as the
edge of printed indicia on a bill, stray marks may cause initiation of the
scanning
process at an improper time. This is especially true for stray marks in the
area
between the edge of a bill and the edge of the printed indicia on the bill.
Such stray
marks may cause the scanning process to be initiated too soon, resulting in a
scanned
pattern which leads a corresponding master pattern. Alternatively, where the
detection of the edge of a bill is used to trigger the scanning process,
misalignment
between patterns may result from variances between the location of printed
indicia on
a bill relative to the edges of a bill. Such variances may result from
tolerances
permitted during the printing and/or cutting processes in the manufacture of
currency.
For example, it has been found that location of the leading edge of printed
indicia on
Canadian currency relative to the edge of Canadian currency may vary up to
approximately 0.2 inches (approximately 0.5 cm).
According to a preferred embodiment of the present invention, the problems
associated with misaligned patterns are overcome by employing an improved
method
of generating multiple scanned and/or master patterns and comparing the
multiple
scanned and master patterns with each other. Briefly, a preferred embodiment
of the
improved pattern generation method involves removing data samples from one end
of
a pattern to be modified and adding data values on the opposite end equal to
the data
values contained in the corresponding sequence positions of the pattern to
which the
modified pattern is to be compared. This process may be repeated, up to a
predetermined number of times, until a sufficiently high correlation is
obtained
between the two patterns so as to permit the identity of a bill under test to
be called.
CA 02215853 1997-11-06
79
A preferred embodiment of the present invention can be further understood by
considering Table 3. Table 3 contains data samples generated by scanning the
narrow dimension of Canadian $2 bills along a segment positioned about the
center of
the bill on the side opposite the portrait side. More specifically, the second
column
of Table 3 represents a scanned pattern generated by scanning a test Canadian
$2 bill.
The scanned pattern comprises 64 data samples arranged in a sequence. Each
data
sample has a sequence position, 1-64, associated therewith. The f fth column
represents a master pattern associated with a Canadian $2 bill. The master
pattern
likewise comprises a sequence of 64 data samples. The third and fourth columns
represent the scanned pattern after it has been modified in the forward
direction one
and two times, respectively. In the embodiment depicted in Table 3, one data
sample
is removed from the beginning of the preceding pattern during each
modification.
Table 3
Sequence Scanned Scanned PatternScanned PatternMaster '
Position Pattern Modified Once Modified TwicePattern
1 93 50 ~ -21 161
2 50 -21 SO 100
3 -21 50 93 171
4 50 93 65 191
5 93 65 22 252
6 b5 22 79 403
7 22 79 136 312
8 79 136 193 434
9 136 193 278 90
10 193 278 164 0
11 278 164 136 20
12 164 136 278 444
I.
CA 02215853 1997-11-06
Sequence Scanned Scanned PatternScanned PatternMaster
Position Pattern Modified Once Modified TwicePattern
52 -490 -518 -447 -1090
53 -518 -447 -646 -767
54 -447 -646 -348 -575
55 -646 -348 -92 -5 i4
56 -348 -92 -63 -545
57 -92 -63 -205 -40
58 -63 -205 605 1665
59 -205 605 1756 1705
60 605 1756 1401 1685
6I 1756 1401 1671 2160
62 1401 1671 2154 2271
63 1671 2154 *2240 2240
64 2154 *2210 *2210 2210
The modified pattern represented in the third column is generated by adding an
additional data value to the end of the original scanned pattern sequence
which
effectively removes the first data sample of the original pattern, e.g., 93,
from the
modified pattern. The added data value in the last sequence position, 64, is
set equal
5 to the data value contained in the 64th sequence position of the master
pattern, e.g.,
2210. This copying of the 64th data sample is indicated by an asterisk in the
third
column. The second modified pattern represented in the fourth column is
generated
by adding two additional data values to the end of the original scanned
pattern which
effectively removes the first two data samples of the original scanned, e.g.,
93 and
10 50, from the second modified pattern. The last two sequence positions, 63
and 64,
are filled with the data value contained in the 63rd and 64th sequence
positions of the
master pattern, e.g., 2240 and 2210, respectively. The copying of the 63rd and
64th
data samples is indicated by asterisks in the fourth column.
In the example of Table 3, the printed area of the bill under test from which
15 the scanned pattern was generated was farther away from the leading edge of
the bill
CA 02215853 1997-11-06
81
than was the printed area of the bill from which the master pattern was
generated.
As a result, the scanned pattern trailed the master pattern. The preferred
embodiment of the pattern generation method described in conjunction with
Table 3
compensates for the variance of the distance between the edge of the bill and
the edge
of the printed indicia by modifying the scanned pattern in the forward
direction. As
a result of the modification method employed, the correlation between the
original
and modified versions of the scanned pattern and the master pattern increased
from
705 for the original, unmodified scanned pattern to 855 for the first modified
pattern
and to 988 for the second modified pattern. Accordingly; the bill under test
which
would otherwise have been rejected may now be properly called as a genuine $2
Canadian bill through the employment of the pattern generation method
discussed
above.
Another preferred embodiment of the present invention can be understood
with reference to the flowchart of FIGs. 17a-17c. The process of FIGs. 17a-17c
involves a method of identifying a bill under test by comparing a scanned
pattern
retrieved from a bill under test with one or more master patterns associated
with one
or more genuine bills. After the process begins at step 128a, the scanned
pattern is
compared with one or more master patterns associated with genuine bills (step
128b).
At step 129 it is determined whether the bill under test can be identified
based on the
comparison at step 128b. This may be accomplished by evaluating the
correlation
between the scanned pattern and each of the master patterns. If the bill can
be
identified, the process is ended at step 130. Otherwise, one or more of the
master
patterns are designated for further processing at step 131. For example, all
of the
master patterns may be designated for further processing. Alternatively, less
than all
of the master patterns may be designated based on a preliminary assessment
about the
identity of the bill under test. For example, only the master patterns which
had the
four highest correlation values with respect to the scanned pattern at step
128b might
be chosen for further processing. In any case, the number of master patterns
designated for further processing is M1.
At step 132, either the scanned pattern is designated for modification or the
M1 master patterns designated at step 131 are designated for modification. In
a
preferred embodiment of the present invention, the scanned pattern is
designated for
CA 02215853 1997-11-06
82
modification and the master patterns remain unmodified. At step 133, it is
designated
whether forward modification or reverse modification is to be performed. This
determination may be made, for example, by analyzing the beginning or ending
data
samples of the scanned pattern to determine whether the scanned pattern trails
or
leads the master patterns.
At step 134, the iteration counter, I, is set equal to one. The iteration
counter
is used to keep track of how many times the working patterns have been
modified.
Then at step 135, the number of incremental data samples, R, to be removed
during
each iteration is set. For example, in a preferred embodiment of the present
invention, only one additional data sample is removed from each working
pattern
during each iteration in which case R is set equal to one.
At step 136, it is determined whether the scanned pattern has been designated
for modification. If it has, then the scanned pattern is replicated Ml times
and the
M1 replicated patterns; one for each of the M1 master patterns, are designated
as
working patterns at step 137. If the scanned pattern has not been designated
for
modification, then the Ml master patterns have been so designated, and the M1
master patterns are replicated and designated as working patterns at step 138.
Regardless of which pattern or patterns were designated for modification, at
step 139,
it is determined whether forward or reverse modification is to be performed on
the
working patterns.
If forward modification is to be performed, the first R x I data samples from
each working pattern are removed at step 140. The first R x I data samples may
either be explicitly removed from the working patterns or be removed as a
result of
adding additional data samples (step 141) to the end of the pattern and
designating the
beginning of the modified pattern to be the R x I + 1 sequence position of the
original pattern. As a result of the modification, the data sample which was
in the
64th sequence position in the original working pattern will be in the 64 - (R
x I)
sequence position. The added data values in the last R x I sequence positions
of a
working pattern are copied from the data samples in the last R x I sequence
positions
of a corresponding non-designated pattern at step 141. After the above
described
modification, the working patterns are compared with either respective ones of
the
non-designated patterns (scanned pattern modified/M1 master patterns not
designated
CA 02215853 1997-11-06
g3
for modification) or the non-designated pattern (M 1 master patterns
designated for
modification/scanned pattern not designated for modification) at step 142.
Alternatively, if reverse modification is to be performed, the last R x I data
samples from each working pattern are removed at step 143. The last R x I data
samples may either be explicitly removed from the working patterns or be
removed
as a result of adding additional data samples (step 144) to the beginning of
the pattern
and designating the beginning of the modified pattern to start with the added
data
samples. As a result of the modification, the data sample which was in the 1st
sequence position in the original working pattern will be in the (R x I) + 1
sequence
position. The added data samples in fast R x I sequence positions of a working
pattern are copied from the data samples in the first R x I sequence positions
of a
corresponding non-designated pattern at step 144. After the above described
modification, the working patterns are compared with either respective ones of
the
non-designated patterns (scanned pattern modified/Ml master patterns not
designated
for modification) or the non-designated pattern (M1 master patterns designated
for
modification/scanned pattern not designated for modification) at step 142.
For example, if the scanned pattern is designated for forward modification and
four master patterns are designated for further processing, four working
patterns are
generated from the scanned pattern at step 137, one for each of the four
master
patterns: If R is set to two at step 135, during the first iteration the last
two data
samples from each of the M1 master patterns are copied and added to the end of
the
Ml working patterns so as to become the last two sequence positions of the
1VI1
working patterns, one working pattern being associated with each of the M1
master
patterns. As a result, after the first iteration, four different working
patterns are
generated with each working pattern corresponding to a modified version of the
scanned pattern but with each having data values in its last two sequence
positions
copied from the last two sequence positions of a respective one of the M1
master
patterns. After a second iteration, the last four sequence positions of each
of the Ml
master patterns are copied and added to the end of the M1 working patterns so
as to
become the last four sequence positions of a respective one of the Ml working
patterns .
CA 02215853 1997-11-06
84
As another example, if four master patterns are designated for further
processing and the four designated master patterns are designated for forward
modification, four working patterns are generated at step 138, one from each
of the
four designated master patterns. If R is set to two at step 135, during the
first
iteration the last two data samples of the scanned pattern are copied and
added to the
end of the M1 working patterns so as to become the last two sequence positions
of
the M1 working patterns, one working pattern being associated with each of the
M1
master patterns. As a result, after the first iteration, four different
working patterns
are generated with each working pattern corresponding to a modified version of
a
corresponding master pattern but with each having data values in its last two
sequence position copied from the last two sequence positions of the scanned
pattern.
After a second iteration, the last four sequence positions of the scanned
pattern are
copied and added to the end of the Ml working patterns so as to become the
last four
sequence positions of the M1 working patterns.
After the comparison at step 142, it is determined whether the bill under test
can be identified at step 145. If the bill can be identified the process is
ended at step
146. Otherwise, the iteration counter, I, is incremented by one.{step 147) and
the
incremented iteration counter is compared to a maximum iteration number, T
(step
148). If the iteration counter, I, is greater than the maximum iteration
number, T,
then a no call is issued (step 149a), meaning that a match su~cient to
identify the
bill under test was not obtained, and the process is ended (step 149b).
Otherwise, if
the iteration is not greater than the maximum iteration number, the
modification
process is repeated beginning with step 136.
The flowchart of FIGS. 17a-17c is intended to illustrate one preferred
embodiment of the present invention. However, it is recognized that there are
numerous ways in which the steps of the flowchart of FIGs. 17a-17c may be
rearranged or altered and yet still result in the comparison of the same
patterns as
would be compared if the steps of FIGs. 17a-17c were followed exactly. For
example, instead of generating multiple working patterns, a single working
pattern
may be generated and the leading or trailing sequence positions successively
altered
before comparisons to corresponding non-designated patterns. Likewise, instead
of
generating multiple modified patterns directly from unmodified patterns,
multiple
CA 02215853 1997-11-06
$$
modified patterns may be generated from the preceding modified patterns. For
example, instead of generating a twice forward modified scanned pattern by
removing
the first two data samples from the original scanned pattern and copying the
last 2R
sequence positions of a corresponding master pattern and adding these data
values to
the end of the original scanned pattern, the first data sample of the single
forward
modified scanned pattern may be removed and one data sample added to the end
of
the single modified scanned pattern and then the data samples in the last two
sequence positions may be set equal to the data samples in the last 2R
sequence
positions of a corresponding master pattern.
In an alternate preferred embodiment of the present invention, instead of
copying data values from a scanned pattern into corresponding sequence
positions of
modified master patterns, leading or trailing sequence positions of modified
master
patterns are filled with zeros.
In an alternate preferred embodiment of the present invention, modified
master patterns are stored, for example in EPROM 60 of FIG. 7a, before a bill
under
test is scanned. In such an embodiment, a scanned pattern retrieved from a
bill
under test is compared to the modified master patterns stored in memory.
Modified
master patterns are generated by modifying a corresponding master pattern in
either
the forward or backward direction, or both, and filling in any trailing or
leading
sequence positions with zeros. An advantage of such a preferred embodiment is
that
no modification needs to be performed during the normal operation of an
identification device incorporating such an embodiment.
An example of a procedure involved in comparing test patterns to master
patterns is illustrated at FIG. 18a which shows the routine as starting at
step 150a.
At step 151a, the best and second best correlation results (referred to in
FiG. 18a as
the "#1 and #2 answers") are initialized to zero and, at step 152a, the test
pattern is
compared with each of the sixteen or eighteen original master patterns stored
in the
memory. At step 153a, the calls corresponding to the two highest correlation
numbers obtained up to that point are determined and saved. At step 154a, a
post-
processing flag is set. At step 155a the test pattern is compared with each of
a
second set of 16 or 18 master patterns stored in the memory. This second set
of
master patterns is the same as the 16 or 18 original master patterns except
that the
CA 02215853 1997-11-06
86
last sample is dropped and a zero is inserted in front of the first sample. If
any of
the resulting correlation numbers is higher than the two highest numbers
previously
saved, the #1 and #2 answers are updated at step 156.
Steps 155a and 156a are repeated at steps 157a and 158a, using a third set of
master patterns formed by dropping the last two samples from each of the 16
original
master patterns and inserting two zeros in front of the first sample. At steps
159a
and 160a the same steps are repeated again, but using only $50 and $100 master
patterns formed by dropping the last three samples from the original master
patterns
and adding three zeros in front of the fast sample. Steps 161a and 162a repeat
the
procedure once again, using only $1, $5, $10 and $20 master patterns formed by
dropping the 33rd sample whereby original samples 34-64 become samples 33-63
and
inserting a 0 as the new last sample. Finally, steps 163a and 164a repeat the
same
procedure, using master patterns for $10 and $50 bills printed in 1950, which
differ
significantly from bills of the same denominations printed in later years.
This routine
then returns to the main program at step 165a. The above multiple sets of
master
patterns may be pre-stored in EPROM 60.
A modified procedure involved in comparing test patterns to green-side master
patterns is illustrated at FIG. 18b which shows the routine as starting at
step 150b.
At step 151b, the best and second best correlation results (referred to in
FIG. 18b as
the "#1 and #2 answers") are initialized to zero and, at step 152b, the test
pattern is
compared with each of the eighteen original green-side master patterns stored
in the
memory. At step 153b, the calls corresponding to the two highest correlation
numbers obtained up to that point are determined and saved. At step 154b, a
post-
processing flag is set. At step 155b the test pattern is compared with each of
a
second set of 18 green-side master patterns stored in the memory. This second
set of
master patterns is the same as the 18 original green-side master patterns
except that
the last sample is dropped and a zero is inserted in front of the first
sample. If any
of the resulting correlation numbers is higher than the two highest numbers
previously saved, the #1 and #2 answers are updated at step 156b.
Steps 155b and 156b are repeated at steps 157b and 158b, using a third set of
green-side master patterns formed by dropping the last two samples from each
of the
18 original master patterns and inserting two zeros in front of the first
sample. At
CA 02215853 1997-11-06
87
steps 159b and 160b the same steps are repeated again, but using only $50 and
$100
master patterns (two patterns for the $50 and four patterns for the $100)
formed by
dropping the last three samples from the original master patterns and adding
three
zeros in front of the first sample. Steps 161b and 162b repeat the procedure
once
again, using only .$1, $5, $10, $20 and $50 master patterns (four patterns for
the $10
and two patterns for the other denominations) formed by dropping the 33rd
sample
whereby original samples 34-64 become samples 33-63 and inserting a 0 as the
new
last sample. Finally, steps 163b and 164b repeat the same procedure, using
master
patterns for $10 and $50 bills printed in 1950 (two patterns scanned along a
center
segment for each denomination), which differ significantly from bills of the
same
denominations printed in later years. This routine then returns to the main
program
at step 165b. The above multiple sets of master patterns may be pre-stored in
EPROM 60.
In a preferred embodiment where conditional black-side correlation is to be
performed a modified version of the routine designated as "CORRES" is
initiated.
The procedure involved in executing the modified version of CORRES is
illustrated
at FIG. 19a which shows the routine as starting at step 180. Step 181
determines
whether the bill has been identified as a $2 bill, and, if the answer is
negative, step
182 determines whether the best correlation number ("call #1 ") is greater
than 799.
If the answer is negative, the correlation number is too low to identify the
denomination of the bill with certainty, and at step 183b a black side
correlation
routine is called (described in more detail below in conjunction with FIGS.
19b-19c).
An affirmative answer at step 182 advances the system to step 186, which
determines whether the sample data passes an ink stain test (described below).
If the
answer is negative, a "no call" bit is set in a correlation result flag at
step 183a. A
"no call previous bill" flag is then set at step 184, and the routine returns
to the main
program at step 185. If the answer at step 186 is affirmative, the system
advances to
step 187 which determines whether the best correlation number is greater than
849.
An affirmative answer at step 187 indicates that the correlation number is
suff ciently
high that the denomination of the scanned bill can be identified with
certainty without
any further checking. Consequently, a "good call" bit is set in the
correlation result
flag at step 188. A separate register associated with the best correlation
number (#1)
CA 02215853 1997-11-06
88
may then be used to identify the denomination represented by the stored
pattern
resulting in the highest correlation number. The system returns to the main
program
at step 185.
A negative answer at step 187 indicates that the correlation number is between
800 and 850. It has been found that correlation numbers within this range are
sufficient to identify all bills except the $2 bill. Accordingly, a negative
response at
step 187 advances the system to step 189 which determines whether the
difference
between the two highest correlation numbers ("call #1 " and "call #2 ") is
greater than
149. If the answer is affirmative, the denomination identified by the highest
correlation number is acceptable, and thus the "good call" bit is set in the
correlation
result flag at step 188. if the difference between the two highest correlation
numbers
is less than 150, step 189 produces a negative response which advances the
system to
step 183b where the black side correlation routine is called.
Returning to step 181, an affirmative response at this step indicates that the
initial call is a $2 bill. This affirmative response initiates a series of
steps 190-193
which are similar to steps 182, 186, 187 and 189 described above, except that
the
numbers 799 and 849 used in steps 182 and 187 are changed to, 849 and 899,
respectively, in steps 190 and 192. The result is either the setting of a "no
call" bit
in a correlation result flag at step 183a, the setting of the "good call" bit
in the
correlation result flag at step 188, or the calling of the black side
correlation routine
at step 183b.
Turning now to FIGs. 19b and 19c there is shown a flowchart illustrating the
steps of the black side correlation routine called at step 183b of FIG. 19a.
After the
black side correlation routine is initiated at step 600, it is determined at
step 602
whether the lower read head was the read head that scanned the black side of
the test
bill. If it was, the lower read head data is normalized at step 604.
Otherwise, it is
determined at step 606 whether the upper read head was the read head that
scanned
the black side of the test bill. If it was, the upper read head data is
normalized at
step 608. If it cannot be determined which read head scanned the black side of
the
bill, then the patterns generated from both sides of the test bill were
correlated
against the green-side master patterns (see e.g., step 110 of FIG. 12). Under
such a
circumstance, the no call bit in the correlation result flag is set at step
610, the no
CA 02215853 1997-11-06
89
call previous bill flag is set at step 611, and the program returns to the
calling point
at step 612.
After the lower read head data is normalized at step 604, or the upper read
head data is normalized at step 608, it is determined whether the best green-
side
correlation number is greater than 700 at step 614. A negative response at
step 614
results in the no call bit in the correlation result flag being set at step
610, the no call
previous bill flag being set at step 611, and the program returning to the
calling point
at step 612. An affirmative response at step 614 results in a determination
being
made as to whether the best call from the green side correlation corresponds
to a
$20, $50, or $100 bill at step 616. A negative response at step 616 results in
the no
call bit in the correlation result flag being set at step 610, the no call
previous bill
flag being set at step 611, and thee program returning to the calling point at
step 612.
If it determined at step 616 that the best call from the green side
correlation
corresponds to a $20, $50, or $100 bill, the scanned pattern from the black
side is
correlated against the black-side master patterns associated with the specific
denomination and scan direction associated the best call from the green side.
According to a preferred embodiment, multiple black-side master patterns are
stored
for $20, $50 and $100 bills. For each of these denominations, three master
patterns
are stored for scans in the forward and three master patterns are stored for
scans in
the reverse direction for a total of six patterns for each denomination. For a
given
scan direction, black-side master patterns are generated by scanning a
corresponding
denominated bill along a segment located about the center of the narrow
dimension of
the bill, a segment slightly displaced (0.2 inches) to the left of center, and
a segment
slightly displaced (0.2 inches) to the right of center.
For example, at step 618, it is determined whether the best call from the
green side is associated with a forward scan of a $20 bill and, if it is, the
normalized
data from the black side of the test bill is correlated against the black-side
master
patterns associated with a forward scan of a $20 bill at step 620. Next it is
determined whether the black-side correlation number is greater than 900 at
step 622.
If it is, the good call bit in the correlation result flag is set at step 648
and the
program returns to the calling point at step 646. If the black-side
correlation number
is not greater than 900, then the no call bit in the correlation result flag
is set at step
CA 02215853 1997-11-06
642, the no call previous bill flag is set at step 644, and the program
returns to the
calling point at step 646. If it is determined that the best call from the
green side is
not associated with a forward scan of $20 bill at step 618, the program
branches
accordingly at steps 624 - 640 so that the normalized data from the black side
of the
5 test bill is correlated against the appropriate black-side master patterns.
Referring now to FIGs. 20a-22, the mechanical portions of the preferred
currency discrimination and counting machine include a rigid frame formed by a
pair
of side plates 201 and 202, a pair of top plates 203a and 203b, and a lower
front
plate 204. The input receptacle for receiving a stack of bills to be processed
is
10 formed by downwardly sloping and converging walls 205 and 206 formed by a
pair
of removable covers 207 and 208 which snap onto the frame. The rear wall 206
supports a removable hopper 209 which includes a pair of vertically disposed
side
walls 210a and 210b which complete the receptacle for the stack of currency
bills to
be processed.
15 From the input receptacle, the currency bills are moved in seriatim from
the
bottom of the stack along a curved guideway 211 which receives bills moving
downwardly and rearwardly and changes the direction of travel to a forward
direction. The curvature of the guideway 211 corresponds substantially to the
curved
periphery of the drive roll 223 so as to form a narrow passageway for the
bills along
20 the rear side of the drive roll. The exit end of the guideway 2i1 directs
the bills
onto a linear path where the bills are scanned and stacked. The bills are
transported
and stacked with the narrow dimension of the bills maintained parallel to the
transport path and the direction of movement at all times.
Stacking of the bills is effected at the forward end of the linear path, where
25 the bills are fed into a pair of driven stacking wheels 212 and 213. These
wheels
project upwardly through a pair of openings in a stacker plate 214 to receive
the bills
as they are advanced across the downwardly sloping upper surface of the plate.
The
stacker wheels 212 and 213 are supported for rotational movement about a shaft
215
journalled on the rigid frame and driven by a motor 216. The flexible blades
of the
30 stacker wheels deliver the bills into an output receptacle 217 at the
forward end of
the stacker plate 214. During operation, a currency bill which is delivered to
the
stacker plate 214 is picked up by the flexible blades and becomes lodged
between a
CA 02215853 1997-11-06
91
pair of adjacent blades which, in combination, define a curved enclosure which
decelerates a bill entering therein and serves as a means for supporting and
transferring the bill into the output receptacle 217 as the slacker wheels
212, 213
rotate. The mechanical configuration of the slacker wheels, as well as the
manner in
which they cooperate with the slacker plate, is conventional and, accordingly,
is not
described in detail herein.
Returning now to the input region of the machine as shown in FIGs. 20a-22,
bills that are stacked on the bottom wall 205 of the input receptacle are
stripped, one
at a time, from the bottom of the stack. The bills are stripped by a pair of
stripping
wheels 220 mounted on a drive shaft 221 which, in turn, is supported across
the side
walls 201, 202. The stripping wheels 220 project through a pair of slots
formed in
the cover 207. Part of the periphery of each wheel 220 is provided with a
raised
high-friction, serrated surface 222 which engages the bottom bill of the input
stack as
the wheels 220 rotate, to initiate feeding movement of the bottom bill from
the stack.
The serrated surfaces 222 project radially beyond the rest of the wheel
peripheries so
that the wheels "jog" the bill stack during each revolution so as to agitate
and loosen
the bottom currency bill within the stack, thereby facilitating the stripping
of the
bottom bill from the stack.
The stripping wheels 220 feed each stripped bill B (FIG. 21a) onto a drive
roll
223 mounted on a driven shaft 224 supported across the side walls 201 and 202.
As
can be seen most clearly in FIGs. 21a and 21b, the drive roll 223 includes a
central
smooth friction surface 225 formed of a material such as rubber or hard
plastic. This
smooth friction surface 225 is sandwiched between a pair of grooved surfaces
226
and 227 having serrated portions 228 and 229 formed from a high-friction
material.
The serrated surfaces 22$, 229 engage each bill after it is fed onto the drive
roll 223 by the stripping wheels 220, to frictionally advance the bill into
the narrow
arcuate passageway formed by the curved guideway 211 adjacent the rear side of
the
drive roll 223. The rotational movement of the drive roll 223 and the
stripping
wheels 220 is synchronized so that the serrated surfaces on the drive roll and
the
stripping wheels maintain a constant relationship to each other. Moreover, the
drive
roll 223 is dimensioned so that the circumference of the outermost portions of
the
grooved surfaces is greater than the width W of a bill, so that the bills
advanced by
CA 02215853 1997-11-06
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the drive roll 223 are spaced apart from each other, for the reasons discussed
above.
That is, each bill fed to the drive roll 223 is advanced by that roll only
when the
serrated surfaces 228, 229 come into engagement with the bill, so that the
circumference of the drive roll 223 determines the spacing between the leading
edges
of successive bills.
To avoid the simultaneous removal of multiple bills from the stack in the
input
receptacle, particularly when small stacks of bills are loaded into the
machine, the
stripping wheels 220 are always stopped with the raised, serrated portions 222
positioned below the bottom wall 205 of the input receptacle. This is
accomplished
by continuously monitoring the angular position of the serrated portions of
the
stripping wheels 220 via the encoder 32, and then controlling the stopping
time of the
drive motor so that the motor always stops the stripping wheels in a position
where
the serrated portions 222 are located beneath the bottom wall 205 of the input
receptacle. Thus, each time a new stack of bills is loaded into the machine,
those
bills will rest on the smooth portions of the stripping wheels. This has been
found to
significantly reduce the simultaneous feeding of double or triple bills,
particularly
when small stacks of bills are involved.
In order to ensure firm engagement between the drive roll 223 and the
currency bill being fed, an idler roll 230 urges each incoming bill against
the smooth
central surface 225 of the drive roll 223. The idler roll 230 is journalled on
a pair of
arms 231 which are pivotally mounted on a support shaft 232. Also mounted on
the
shaft 232, on opposite sides of the idler roll 230, are a pair of grooved
guide wheels
233 and 234. The grooves in these two wheels 233, 234 are registered with the
central ribs in the two grooved surfaces 226, 227 of the drive roll 223. The
wheels
233, 234 are locked to the shaft 232, which in turn is locked against movement
in the
direction of the bill movement (clockwise as view in FIG. 20a) by a one-way
spring
clutch 235. Each time a bill is fed into the nip between the guide wheels 233,
234
and the drive roll 223, the clutch 235 is energized to turn the shaft 232 just
a few
degrees in a direction opposite the direction of bill movement. These repeated
incremental movements distribute the wear uniformly around the circumferences
of
the guide wheels 233, 234. Although the idler roll 230 and the guide wheels
233,
234 are mounted behind the guideway 211, the guideway is apertured to allow
the
CA 02215853 1997-11-06
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roll 230 and the wheels ?33, 234 to engage the bills on the front side of the
guideway.
Beneath the idler roll 230, a spring-loaded pressure roll 236 (FIGS. 20a and
21b) presses the bills into firm engagement with the smooth friction surface
225 of
the drive roll as the bills curve downwardly along the guideway 211. This
pressure
roll 236 is journalled on a pair of arms 237 pivoted on a stationary shaft
238. A
spring 239 attached to the lower ends of the arms 237 urges the roll 236
against the
drive roll 233, through an aperture in the curved guideway 211.
At the lower end of the curved guideway 211, the bill being transported by
the drive roll 223 engages a flat guide plate 240 which carries a lower scan
head 18.
Currency bills are positively driven along the flat plate 240 by means of a
transport
roll arrangement which includes the drive roll 223 at one end of the plate and
a
smaller driven roll 241 at the other end of the plate. Both the driver roll
223 and the
smaller roll 241 include pairs of smooth raised cylindrical surfaces 242 and
243
which hold the bill flat against the plate 240. A pair of 0 rings 244 and 245
fit into
grooves formed in both the roll 241 and the roll 223 to engage the bill
continuously
between the two rolls 223 and 241 to transport the bill while helping to hold
the bill
flat against the guide plate 240.
The flat guide plate 240 is provided with openings through which the raised
surfaces 242 and 243 of both the drive roll 223 and the smaller driven roll
24i are
subjected to counter-rotating contact with corresponding pairs of passive
transport
rolls 250 and 251 having high-friction rubber surfaces. The passive rolls 250,
251
are mounted on the underside of the flat plate 240 in such a manner as tb be
freewheeling about their axes 254 and 255 and biased into counter-rotating
contact
with the corresponding upper rolls 223 and 241. The passive rolls 250 and 251
are
biased into contact with the driven rolls 223 and 241 by means of a pair of H-
shaped
leaf springs 252 and 253 (see FIGs. 23 and 24). Each of the four rolls 250,
251 is
cradled between a pair of parallel arms of one of the H-shaped leaf springs
252 and
253. The central portion of each leaf spring is fastened to the plate 240,
which is
fastened rigidly to the machine frame, so that the relatively stiff arms of
the H-
shaped springs exert a constant biasing pressure against the rolls and push
them
against the upper rolls 223 and 241.
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The points of contact between the driven and passive transport rolls are
preferably coplanar with the flat upper surface of the plate 240 so that
currency bills
can be positively driven along the top surface of the plate in a flat manner.
The
distance between the axes of the two driven transport rolls, and the
corresponding
counter-rotating passive rolls, is selected to be just short of the length of
the narrow
dimension of the currency bills. Accordingly, the bills are firmly gripped
under
uniform pressure between the upper and lower transport rolls within the
scanhead
area. thereby minimizing the possibility of bill skew and enhancing the
reliability of
the overall scanning and recognition process.
The positive guiding arrangement described above is advantageous in that
uniform guiding pressure is maintained on the bills as they are transported
through
the optical scanhead area, and twisting or skewing of the bills is
substantially
reduced. This positive action is supplemented by the use of the H-springs 252,
253
for uniformly biasing the passive rollers into contact with the active rollers
so that
bill twisting or skew resulting from differential pressure applied to the
bills along the
transport path is avoided. The O-rings 244, 245 function as simple, yet
extremely
effective means for ensuring that the central portions of the bills are held
flat.
The location of a magnetic head 256 and a magnetic head adjustment screw
257 are illustrated in FIG. 23. The adjustment screw 257 adjusts the proximity
of
the magnetic head 256 relative to a passing bill and thereby adjusts the
strength of the
magnetic field in the vicinity of the bill.
FIG. 22 shows the mechanical arrangement for driving the various means for
transporting currency bills through the machine. A motor 260 drives a shaft
261
carrying a pair of pulleys 262 and 263. The pulley 262 drives the roll 241
through a
belt 264 and pulley 265, and the pulley 263 drives the roll 223 through a belt
266
and pulley 267. Both pulleys 265 and 267 are larger than pulleys 262 and 263
in
order to achieve the desired speed reduction from the typically high speed at
which
the motor 260 operates.
The shaft 221 of the stripping wheels 220 is driven by means of a pulley 268
provided thereon and linked to a corresponding pulley 269 on the shaft 224
through a
belt 270. The pulleys 268 and 269 are of the same diameter so that the shafts
221
and 224 rotate in unison.
CA 02215853 1997-11-06
As shown in FIG. 20b, the optical encoder 32 is mounted on the shaft of the
roller 241 for precisely tracking the position of each bill as it is
transported through
the machine, as discussed in detail above in connection with the optical
sensing and
correlation technique.
5 The upper and lower scanhead assemblies are shown most clearly in FIGS. 25-
28. It can be seen that the housing for each scanhead is formed as an integral
part of
a unitary molded plastic support member 280 or 281 that also forms the
housings for
the light sources and photodetectors of the photosensors PS1 and PS2. The
lower
member 281 also forms the fiat guide plate 240 that receives the bills from
the drive
10 roll 223 and supports the bills as they are driven past the scanheads 18a
and 18b.
The two support members 280 and 281 are mounted facing each other so that
the lenses 282 and 283 of the two scanheads 18a, 18b define a narrow gap
through
which each bill is transported. Similar, but slightly larger, gaps are formed
by the
opposed lenses of the light sources and photodetectors of the photosensors PS
1 and
15 PS2. The upper support member 280 includes a tapered entry guide 280a which
guides an incoming bill into the gaps between the various pairs of opposed
lenses.
The lower support member 281 is attached rigidly to the,machine frame. The
upper support member 280, however, is mounted for limited vertical movement
when
it is lifted manually by a handle 284, to facilitate the clearing of any paper
jams that
20 occur beneath the member 280. To allow for such vertical movement, the
member
280 is slidably mounted on a pair of posts 285 and 286 on the machine frame,
with a
pair of springs 287 and 288 biasing the member 280 to its lowermost position.
Each of the two optical scanheads 18a and 18b housed in the support members
280, 281 includes a pair of light sources acting in combination to uniformly
25 illuminate light strips of the desired dimension on opposite sides of a
bill as it is
transported across the plate 240. Thus, the upper scanhead 18a includes a pair
of
LEDs 22a, directing light downwardly through an optical mask on top of the
lens 282
onto a bill traversing the flat guide plate 240 beneath the scanhead. The LEDs
22a
are angularly disposed relative to the vertical axis of the scanhead so that
their
30 respective light beams combine to illuminate the desired light strip
defined by an
aperture in the mask. The scanhead 18a also includes a photodetector 26a
mounted
directly over the center of the illuminated strip for sensing the light
reflected off the
CA 02215853 1997-11-06
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strip. The photodetector 26a is linked to the CPU 30 through the ADC 28 for
processing the sensed data as described above.
When the photodetector 26a is positioned on an axis passing through the
center of the illuminated strip, the illumination by the LED's as a function
of the
distance from the central point "0" along the X axis, should optimally
approximate a
step function as illustrated by the curve A in FIG. 29. With the use of a
single light
source angularly displaced relative to a vertical axis through the center of
the
illuminated strip, the variation in illumination by an LED typically
approximates a
Gaussian function, as illustrated by the curve B in FIG. 29.
The two LEDs 22a are angularly disposed relative to the vertical axis by
angles a and (3, respectively. The angles a and (3 are selected to be such
that the
resultant strip illumination by the LED's is as close as possible to the
optimum
distribution curve A in FIG. 29. The LED illumination distribution realized by
this
arrangement is illustrated by the curve designated as "C" in FIG. 29 which
effectively merges the individual Gaussian distributions of each light source
to yield a
composite distribution which sufficiently approximates the optimum curve A.
In the particular embodiment of the scanheads 18a and 18b illustrated in the
drawings, each scanhead includes two pairs of LEDs and two photodetectors for
illuminating, and detecting light reflected from, strips of two different
sizes. Thus,
each mask also includes two slits which are formed to allow light from the
LEDs to
pass through and illuminate light strips of the desired dimensions. More
specifically,
one slit illuminates a relatively wide strip used for obtaining the
reflectance samples
which correspond to the characteristic pattern for a test bill. In a preferred
embodiment, the wide slit has a length of about 0.500" and a width of about
0.050".
The second slit forms a relatively narrow illuminated strip used for detecting
the thin
borderline surrounding the printed indicia on currency bills, as described
above in
detail. In a preferred embodiment, the narrow slit 283 has a length of about
0.300"
and a width of about 0.010" .
In order to prevent dust from fouling the operation of the scanheads, each
scanhead includes three resilient seals or gaskets 290, 291, and 292. The two
side
seals 290 and 29 i seal the outer ends of the LEDs 22, while the center seal
292 seals
the outer end of the photodetector 26. Thus, dust cannot collect on either the
light
CA 02215853 1997-11-06
97
sources or the photodetectors, and cannot accumulate and block the slits
through
which light is transmitted from the sources to the bill, and from the bill to
the
photodetectors.
Doubling or overlapping of bills in the illustrative transport system is
detected
by two photosensors PS 1 and PS2 which are located on a common transverse axis
that is perpendicular to the direction of bill flow (see e.g., FIGs. 30a and
30b). The
photosensors PS 1 and PS2 include photodetectors 293 and 294 mounted within
the
lower support member 281 in immediate opposition to corresponding light
sources
295 and 296 mounted in the upper support member 280. The photodetectors 293 ,
294 detect beams of light directed downwardly onto the bill transport path
from the
light sources 295, 296 and generate analog outputs which correspond to the
sensed
light passing through the bill. Each such output is convened into a digital
signal by a
conventional ADC convertor unit (not shown) whose output is fed as a digital
input to
and processed by the system CPU.
The presence of a bill adjacent the photosensors PS1 and PS2 causes a change
in the intensity of the detected light, and the corresponding changes in the
analog
outputs of the photodetectors 293 and 294 serve as a convenient means for
density-
based measurements for detecting the presence of "doubles" (two or more
overlaid or
overlapped bills) during the currency scanning process. For instance, the
photosensors may be used to collect a predefined number of density
measurements on
a test bill, and the average density value for a bill may be compared to
predetermined
density thresholds (based, for instance, on standardized density readings for
master
bills) to determine the presence of overlaid bills or doubles.
In order to prevent the accumulation of dirt on the light sources 295 and 296
and/or the photodetectors 293, 294 of the photosensors PS1 and PS2, both the
light
sources and the photodetectors are enclosed by lenses mounted so close to the
bill
path that they are continually wiped by the bills. This provides a self
cleaning action
which reduces maintenance problems and improves the reliability of the outputs
from
the photosensors over long periods of operation.
The CPU 30, under control of software stored in the EPROM 34, monitors
and controls the speed at which the bill transport mechanism 16 transports
bills from
the bill separating station 14 to the bill stacking unit. Flowcharts of the
speed control
CA 02215853 1997-11-06
98
routines stored in the EPROM 34 are depicted in FIGS. 31-35. To execute more
than
the first step in any given routine, the currency discriminating system 10
must be
operating in a mode requiring the execution of the routine.
Referring first to FIG. 31, when a user places a stack of bills in the bill
accepting station 12 for counting, the transport speed of the bill transport
mechanism
16 must accelerate or "ramp up" from zero to top speed. Therefore, in response
to
receiving the stack of bills in the bill accepting station 12, the CPU 30 sets
a ramp-up
bit in a motor flag stored in the memory unit 38. Setting the ramp-up bit
causes the
CPU 30 to proceed beyond step 300b of the ramp-up routine. If the ramp-up bit
is
set, the CPU 30 utilizes a ramp-up counter and a fixed parameter "ramp-up
step" to
incrementally increase the transport speed of the bill transport mechanism 16
until the
bill transport mechanism 16 reaches its top speed. The "ramp-up step" is equal
to
the incremental increase in the transport speed of the bill transport
mechanism 16,
and the ramp-up counter determines the amount of time between incremental
increases in the bill transport speed. The greater the value of the "ramp-up
step", the
greater the increase in the transport speed of the bill transport mechanism 16
at each
increment. The greater the maximum value of the ramp-up counter, the greater
the
amount of time between increments. Thus, the greater the value of the "ramp-up
step" and the lesser the maximum value of the ramp-up counter, the lesser the
time it
takes the bill transport mechanism 16 to reach its top speed.
The ramp-up routine in FIG. 31 employs a variable parameter "new speed", a
fixed parameter "full speed", and the variable parameter "transport speed".
The "full
speed" represents the top speed of the bill transport mechanism 16, while the
"new
speed" and "transport speed" represent the desired current speed of the bill
transport
mechanism 16. To account for operating offsets of the bill transport mechanism
16,
the "transport speed" of the bill transport mechanism 16 actually differs from
the
"new speed" by a "speed offset value". Outputting the "transport speed" to the
bill
transport mechanism 16 causes the bill transport mechanism i6 to operate at
the
transport speed.
To incrementally increase the speed of the bill transport mechanism 16, the
CPU 30 first decrements the ramp-up counter from its maximum value (step 301).
If
the maximum value of the ramp-up counter is greater than one at step 302, the
CPU
CA 02215853 1997-11-06
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30 exits the speed control software in FIGS. 31-35 and repeats steps 300b,
301, and
302 during subsequent iterations of the ramp-up routine until the ramp-up
counter is
equal to zero. When the ramp-up counter is equal to zero, the CPU 30 resets
the
ramp-up counter to its maximum value (step 303). Next, the CPU 30 increases
the
"new speed" by the "ramp-up step" (step 30-t). If the "new speed" is not yet
equal to
the "full speed" at step 305, the "transport speed" is set equal to the "new
speed"
plus the "speed offset value" (step 306). The "transport speed" is output to
the bill
transport mechanism 16 at step 307 of the routine in FIG. 31 to change the
speed of
the bill transport mechanism 16 to the "transport speed" . During subsequent
iterations of the ramp-up routine, the CPU 30 repeats steps 300b-306 until the
"new
speed" is greater than or equal to the "full speed".
Once the "new speed" is greater than or equal to the "full speed" at step 305,
the ramp-up bit in the motor flag is cleared (step 308), a pause-afrer-ramp
bit in the
motor flag is set (step 309), a pause-after-ramp counter is set to its maximum
value
(step 310), and the parameter "new speed" is set equal to the "full speed"
(step 311).
Finally, the "transport speed" is set equal to the "new speed" plus the "speed
offset
value" (step 306). Since the "new speed" is equal to the "full speed",
outputting the
"transport speed" to the bill transport mechanism 16 causes the bill transport
mechanism 16 to operate at its top speed. The ramp-up routine in FIG. 31
smoothly
increases the speed of the bill transport mechanism without causing jerking or
motor
spikes. Motor spikes could cause false triggering of the optical scanhead 18
such that
the scanhead 18 scans non-existent bills.
During normal counting, the bill transport mechanism 16 transports bills from
the bill separating station 14 to the bill stacking unit at its top speed. In
response to
the optical scanhead 18 detecting a stranger, suspect or no call bill,
however, the
CPU 30 sets a ramp-to-slow-speed bit in the motor flag. Setting the ramp-to-
slow-
speed bit causes the CPU 30 to proceed beyond step 312 of the ramp-to-slow-
speed
routine in FIG. 32 on the next iteration of the software in FIGS. 31-35. Using
the
ramp-to-slow-speed routine in FIG. 32, the CPU 30 causes the bill transport
mechanism 16 to controllably decelerate or "ramp down" from its top speed to a
slow
speed. As the ramp-to-slow speed routine in FIG. 32 is similar to the ramp-up
routine in FIG. 31, it is not described in detail herein.
CA 02215853 1997-11-06
1 ~()
It suffices to state that if the ramp-to-slow-speed bit is set in the motor
flag,
the CPU 30 decrements a ramp-down counter (step 313) and determines whether or
not the ramp-down counter is equal to zero (step 314). If the ramp-down
counter is
not equal to zero, the CPU 30 exits the speed control software in FIGs. 31-35
and
repeats steps 312, 313, and 314 of the ramp-to-slow-speed routine in FIG. 32
during
subsequent iterations of the speed control software until the ramp-down
counter is
equal to zero. Once the ramp-down counter is equal to zero, the CPU 30 resets
the
ramp-down counter to its maximum value {step 31~) and subtracts a "ramp-down
step" from the variable parameter "new speed" (step 316). The "new speed" is
equal
to the fixed parameter "full speed" prior to initiating the ramp-to-slow-speed
routine
in FIG. 32.
After subtracting the "ramp-down step" from the "new speed", the "new
speed" is compared to a fixed parameter "slow speed" (step 317). If the "new
speed"
is greater than the "slow speed", the "transport speed" is set equal to the
"new
speed" plus the "speed offset value" (step 318) and this "transport speed" is
output to
the bill transport mechanism 16 (step 307 of FIG. 31). During subsequent
iterations
of the ramp-to-slow-speed routine, the CPU 30 continues to decrement the "new
speed" by the "ramp-down step" until the "new speed" is less than or equal to
the
"slow speed" . Once the "new speed" is less than or equal to the "slow speed"
at step
317, the CPU 30 clears the ramp-to-slow-speed bit in the motor flag (step
319), sets
the pause-after-ramp bit in the motor flag (step 320), sets the pause-after-
ramp
counter (step 321), and sets the "new speed" equal to the "slow speed" (step
322).
Finally, the "transport speed" is set equal to the "new speed" plus the "speed
offset
value" (step 318). Since the "new speed" is equal to the "slow speed",
outputting the
"transport speed" to the bill transport mechanism 16 causes the bill transport
mechanism 16 to operate at its slow speed. The ramp-to-slow-speed routine in
FIG.
32 smoothly decreases the speed of the bill transport mechanism 16 without
causing
jerking or motor spikes.
FIG. 33 depicts a ramp-to-zero-speed routine in which the CPU 30 ramps
down the transport speed of the bill transport mechanism 16 to zero either
from its
top speed or its slow speed. In response to completion of counting of a stack
of
bills, the CPU 30 enters this routine to ramp down the transport speed of the
bill
CA 02215853 1997-11-06
101
transport mechanism 16 from its top speed to zero. Similarly, in response to
the
optical scanhead 18 detecting a stranger, suspect, or no call bill and the
ramp-to-
slow-speed routine in FIG. 32 causing the transport speed to be equal to a
slow
speed, the CPU 30 enters the ramp-to-zero-speed routine to ramp down the
transport
speed from the slow speed to zero.
With the ramp-to-zero-speed bit set at step 323, the CPU 30 determines
whether or not an initial-braking bit is set in the motor flag (step 324).
Prior to
ramping down the transport speed of the bill transport mechanism 16, the
initial-
braking bit is clear. Therefore, flow proceeds to the left branch of the ramp-
to-zero-
speed routine in FIG. 33. In this Ieft branch, the CPU 30 sets the initial-
braking bit
in the motor flag (step 325), resets the ramp-down counter to its maximum
value
(step 326), and subtracts an "initial-braking step" from the variable
parameter "new
speed" (step 327). Next, the CPU 30 determines whether or not the "new speed"
is
greater than zero (step 328). If the "new speed" is greater than zero at step
328, the
variable parameter "transport speed" is set equal to the "new speed" plus the
"speed
offset value" (step 329) and this "transport speed" is output to the bill
transport
mechanism 16 at step 307 in FIG. 31.
During the next iteration of the ramp-to-zero-speed routine in FIG. 33, the
CPU 30 enters the right branch of the routine at step 324 because the initial-
braking
bit was set during the previous iteration of the ramp-to-zero-speed routine.
With the
initial-braking bit set, the CPU 30 decrements the ramp-down counter from its
maximum value (step 330) and determines whether or not the ramp-down counter
is
equal to zero (step 331). If the ramp-down counter is not equal to zero, the
CPU 30
immediately exits the speed control software in FIGs. 31-35 and repeats steps
323,
324, 330, and 331 of the ramp-to-slow-speed routine during subsequent
iterations of
the speed control software until the ramp-down counter is equal to zero. Once
the
ramp-down counter is equal to zero, the CPU 30 resets the ramp-down counter to
its
maximum value (step 332) and subtracts a "ramp-down step" from the variable
parameter "new speed" (step 333). This "ramp-down step" is smaller than the
"initial-braking step" so that the "initial-braking step" causes a larger
decremental
change in the transport speed of the bill transport mechanism 16 than that
caused by
the "ramp-down step".
CA 02215853 1997-11-06
102
Next, the CPU 30 determines whether or not the "new speed" is greater than
zero (step 328). If the "new speed" is greater than zero, the "transport
speed" is set
equal to the "new speed" plus the "speed offset value" (step 329) and this
"transport
speed" is outputted to the bill transport mechanism 16 (step 307 in FIG. 31).
During
subsequent iterations of the speed control software, the CPU 30 continues to
decrement the "new speed" by the "ramp-down step" at step 333 until the "new
speed" is less than or equal to zero at step 328. Once the "new speed" is less
than or
equal to the zero at step 328, the CPU 30 clears the ramp-to-zero-speed bit
and the
initial-braking bit in the motor flag (step 334), sets a motor-at-rest bit in
the motor
flag (step 335), and sets the "new speed" equal to zero (step 336). Finally,
the
"transport speed" is set equal to the "new speed" plus the "speed offset
value" (step
329). Since the "new speed" is equal to zero, outputting the "transport speed"
to the
bill transport mechanism 16 at step 307 in FIG. 31 halts the bill transport
mechanism
16.
Using the feedback loop routine in FIG. 35, the CPU 30 monitors and
stabilizes the transport speed of the bill transport mechanism 16 when the
bill
transport mechanism 16 is operating at its top speed or at slow speed. To
measure
the transport speed of the bill transport mechanism 16, the CPU 30 monitors
the
optical encoder 32. While monitoring the optical encoder 32, it is important
to
synchronize the feedback loop routine with any transport speed changes of the
bill
transport mechanism 16. To account for the time lag between execution of the
ramp-
up or ramp-to-slow-speed routines in FIGS. 31-32 and the actual change in the
transport speed of the bill transport mechanism 16, the CPU 30 enters a pause-
after-
ramp routine in FIG. 34 prior to entering the feedback loop routine in FIG. 35
if the
bill transport mechanism 16 completed ramping up to its top speed or ramping
down
to slow speed during the previous iteration of the speed control software in
FIGs. 31-
35.
The pause-after-ramp routine in FIG. 34 allows the bill transport mechanism
16 to "catch up" to the CPU 30 so that the CPU 30 does not enter the feedback
loop
routine in FIG. 35 prior to the bill transport~mechanism 16 changing speeds.
As
stated previously, the CPU 30 sets a pause-after-ramp bit during step 309 of
the
ramp-up routine in FIG. 31 or step 320 of the ramp-to-slow-speed routine in
FIG.
CA 02215853 1997-11-06
1_~;
32. With the pause-after-ramp bit set, flow proceeds from step 337 of the
pause-
after=ramp routine to step 338, where the CPU 30 decrements a pause-after-ramp
counter from its maximum value. If the pause-after-ramp counter is not equal
to zero
at step 339, the CPU 30 exits the pause-after-ramp routine in FIG. 34 and
repeats
steps 337, 338, and 339 of the pause-after-ramp routine during subsequent
iterations
of the speed control software until the pause-after-ramp counter is equal to
zero.
Once the pause-after-ramp counter decrements to zero, the CPU 30 clears the
pause-
after-ramp bit in the motor flag (step 340) and sets the feedback loop counter
to its
maximum value (step 341). The maximum value of the pause-after-ramp counter is
selected to delay the CPU 30 by an amount of time sufficient to permit the
bill
transport mechanism i6 to adjust to a new transport speed prior to the CPU 30
monitoring the new transport speed with the feedback loop routine in FIG. 35.
Referring now to the feedback loop routine in FIG. 35, if the motor-at-rest
bit
in the motor flag is not set at step 342, the CPU 30 decrements a feedback
loop
counter from its maximum value (step 343). If the feedback loop counter is not
equal
to zero at step 344, the CPU 30 immediately exits the feedback loop routine in
FIG.
35 and repeats steps 342, 343, and 344 of the feedback loop routine during
subsequent iterations of the speed control software in FIGs. 31-36 until the
feedback
loop counter is equal to zero. Once the feedback loop counter is decremented
to
zero, the CPU 30 resets the feedback loop counter to its maximum value (step
345),
stores the present count of the optical encoder 32 (step 346), and calculates
a variable
parameter "actual difference" between the present count and a previous count
of the
optical encoder 32 (step 347). The "actual difference" between the present and
previous encoder counts represents the transport speed of the bill transport
mechanism 16. The larger the "actual difference" between the present and
previous
encoder counts, the greater the transport speed of the bill transport
mechanism. The
CPU 30 subtracts the "actual difference" from a fixed parameter "requested
difference" to obtain a variable parameter "speed difference" (step 348).
If the "speed difference" is greater than zero at step 349, the bill transport
speed of the bill transport mechanism 16 is too slow. To counteract slower
than ideal
bill transport speeds, the CPU 30 multiplies the "speed difference" by a "gain
constant" (step 354) and sets the variable parameter "transport speed" equal
to the
CA 02215853 1997-11-06
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multiplied difference from step 354 plus the "speed offset value" plus a fixed
parameter "target speed" (step 355). The "target speed" is a value that, when
added
to the "speed offset value", produces the ideal transport speed. The
calculated
"transport speed" is greater than this ideal transport speed by the amount of
the
multiplied difference. If the calculated "transport speed" is nonetheless less
than or
equal to a fixed parameter "maximum allowable speed" at step 356, the
calculated
"transport speed" is output to the bill transport mechanism 16 at step 307 so
that the
bill transport mechanism 16 operates at the calculated "transport speed". If,
however, the calculated "transport speed" is greater than the "maximum
allowable
speed" at step 356, the parameter "transport speed" is set equal to the
"maximum
allowable speed" (step 357) and is output to the bill transport mechanism 16
(step
307).
If the "speed difference" is less than or equal to zero at step 349, the bill
transport speed of the bill transport mechanism 16 is too fast or is ideal. To
counteract faster than ideal bill transport speeds, the CPU 30 multiplies the
"speed
difference" by a "gain constant" (step 350) and sets the variable parameter
"transport
speed" equal to the multiplied difference from step 350 plus the "speed offset
value"
plus a fixed parameter "target speed" (step 351). The calculated "transport
speed" is
less than this ideal transport speed by the amount of the multiplied
difference. If the
calculated "transport speed" is nonetheless greater than or equal to a fixed
parameter
"minimum allowable speed" at step 352, the calculated "transport speed" is
output to
the bill transport mechanism 16 at step 307 so that the bill transport
mechanism 16
operates at the calculated "transport speed" . If, however, the calculated
"transport
speed" is less than the "minimum allowable speed" at step 352, the parameter
"transport speed" is set equal to the "minimum allowable speed" (step 353) and
is
output to the bill transport mechanism 16 (step 307).
It should be apparent that the smaller the value of the "gain constant", the
smaller the variations of the bill transport speed between successive
iterations of the
feedback control routine in FIG. 35 and, accordingly, the less quickly the
bill
transport speed is adjusted toward the ideal transport speed. Despite these
slower
adjustments in the bill transport speed, it is generally preferred to use a
relatively
CA 02215853 1997-11-06
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small "gain constant" to prevent abrupt fluctuations in the bill transport
speed and to
prevent overshooting the ideal bill transport speed.
A routine for using the outputs of the two photosensors PS 1 and PSZ to detect
any doubling or overlapping of bills is illustrated in FIG. 36 by sensing the
optical
density of each bill as it is scanned. This routine starts at step 401 and
retrieves the
denomination determined for the previously scanned bill at step 402. This
previously
determined denomination is used for detecting doubles in the event that the
newly
scanned bill is a "no call", as described below. Step 403 determines whether
the
current bill is a "no call," and if the answer is negative, the denomination
determined
for the new bill is retrieved at step 404.
If the answer at step 403 is affirmative, the system jumps to step 405, so
that
the previous denomination retrieved at step 402 is used in subsequent steps.
To
permit variations in the sensitivity of the density measurement, a "density
setting" is
retrieved from memory at step 405. The operator makes this choice manually,
according to whether the bills being scanned are new bills, requiring a high
degree of
sensitivity, or used bills, requiring a lower level of sensitivity. If the
"density
setting" has been turned off, this condition is sensed at step 406, and the
system
returns to the main program at step 413. If the "density setting" is not
turned off, a
denominational density comparison value is retrieved from memory at step 407.
The memory preferably contains five different density values (for five
different density settings, i.e., degrees of sensitivity) for each
denomination. Thus,
for a currency set containing seven different denominations, the memory
contains 35
different values. The denomination retrieved at step 404 (or step 402 in the
event of
a "no call"), and the density setting retrieved st step 405, determine which
of the 35
stored values is retrieved at step 407 for use in the comparison steps
described below.
At step 408, the density comparison value retrieved at step 407 is compared to
the average density represented by the output of the photosensor PS 1. The
result of
this comparison is evaluated at step 409 to determine whether the output of
sensor S 1
identifies a doubling of bills for the particular denomination of bill
determined at step
402 or 404. If the answer is negative, the system returns to the main program
at step
413. If the answer is affirmative, step 410 then compares the retrieved
density
comparison value to the average density represented by the output of the
second
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sensor PS2. The result of this comparison is evaluated at step 411 to
determine
whether the output of the photosensor PS2 identifies a doubling of bills.
Affirmative
answers at both step 409 and step 411 result in the setting of a "doubles
error" flag at
step 412, and the system then returns to the main program at step 413. The
"doubles error" flag can, of course, be used to stop the bill transport motor.
FIG. 37 illustrates a routine that enables the system to detect bills which
have
been badly defaced by dark marks such as ink blotches, felt-tip pen marks and
the
like. Such severe defacing of a bill can result in such distorted scan data
that the
data can be interpreted to indicate the wrong denomination for the bill.
Consequently, it is desirable to detect such severely defaced bills and then
stop the
bill transport mechanism so that the bill in question can be examined by the
operator.
The routine of FIG. 37 retrieves each successive data sample at step 450b and
then advances to step 451 to determine whether that sample is too dark. As
described above, the output voltage from the photodetector 26 decreases as the
darkness of the scanned area increases. Thus, the lower the output voltage
from the
photodetector, the darker the scanned area. For the evaluation carned out at
step
451, a preselected threshold level for the photodetector output voltage, such
as a
threshold level of about 1 volt, is used to designate a sample that is "too
dark. "
An affirmative answer at step 451 advances the system to step 452 where a
"bad sample" count is incremented by one. A single sample that is too dark is
not
enough to designate the bill as seriously defaced. Thus, the "bad sample"
count is
used to determine when a preselected number of consecutive samples, e.g., ten
consecutive samples, are determined to be too dark. From step 452, the system
advances to step 453 to determine whether ten consecutive bad samples have
been
received. If the answer is affirmative, the system advances to step 454 where
an
error flag is set. This represents a "no call" condition, which causes the
bill
transport system to be stopped in the same manner discussed above.
When a negative response is obtained at step 451, the system advances to step
455 where the "bad sample" count is reset to zero, so that this count always
represents the number of consecutive bad samples received. From step 455 the
system advances to step 456 which determines when all the samples for a given
bill
have been checked. As long as step 456 yields a negative answer, the system
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continues to retrieve successive samples at step 450b. When an affirmative
answer is
produced at step 456, the system returns to the main program at step 457.
A routine for-automatically monitoring and making any necessary corrections
in various line voltages is illustrated in FIG. 38. This routine is useful in
automatically compensating for voltage drifts due to temperature changes,
aging of
components and the like. The routine starts at step 550 and reads the output
of a line
sensor which is monitoring a selected voltage at step 550b. Step 551
determines
whether the reading is below 0.60, and if the answer is affirmative, step 552
determines whether the reading is above 0.40. If step 552 also produces an
affirmative response, the voltage is within the required range and thus the
system
returns to the main program step 553. If step 551 produces a negative
response, an
incremental correction is made at step 554 to reduce the voltage in an attempt
to
return it to the desired range. Similarly, if a negative response is obtained
at step
552, an incremental correction is made at step 555 to increase the voltage
toward the
desired range.
Now that a currency scanner has been described in connection with scanning
U.S. currency, an additional currency discrimination system of the present
invention
will be described.
First of all, because currencies come in a variety of sizes, sensors are added
to determine the size of a bill to be scanned. These sensors are placed
upstream of
the scanheads to be described below. A preferred embodiment of size
determining
sensors is illustrated in FIG. 39. Two leading/trailing edge sensors 1062
detect the
leading and trailing edges of a bill 1064 as it passing along the transport
path. These
sensors in conjunction with the encoder 32 (FIG. 2a-2b) may be used to
determine
the dimension of the bill along a direction parallel to the scan direction
which in FIG.
39 is the narrow dimension (or width) of the bill 1064. Additionally, two side
edge
sensors 1066 are used to detect the dimension of a bill 1064 transverse to the
scan
direction which in FIG. 39 is the wide dimension (or length) of the bill 1064.
While
the sensors 1062 and 1066 of FIG. 39 are optical sensors, other means of
determining the size of a bill may be employed.
Once the size of a bill is determined, the potential identity of the bill is
limited
to those bills having the same size. Accordingly, the area to be scanned can
be
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tailored to the area or areas best suited for identifying the denomination and
country
of origin of a bill having the measured dimensions.
Secondly, while the printed indicia on U.S. currency is enclosed within a thin
borderline, the sensing of which may serve as a trigger to begin scanning
using a
wider slit, most currencies of other currency systems such as those from other
countries do not have such a borderline. Thus the system described above may
be
modified to begin scanning relative to the edge of a bill for currencies
lacking such a
borderline. Referring to FIG. 40, two leading edge detectors 1068 are shown.
The
detection of the leading edge 1069 of a bill 1070 by leading edge sensors 1068
triggers scanning in an area a given distance away from the leading edge of
the bill
1070, e.g., D1 or Dz, which may vary depending upon the preliminary indication
of
the identity of a bill based on the dimensions of a bill. Alternatively, the
leading
edge 1069 of a bill may be detected by one or more of the scanheads (to be
described
below) in a similar manner as that described with respect to FIGS. 7a and 7b.
Alternatively, the beginning of scanning may be triggered by positional
information
provided by the encoder 32 of FIG. 2a-2b, for example, in conjunction with the
signals provided by sensors 1062 of FIG. 39, thus eliminating the need for
leading
edge sensors 1068.
However, when the initiation of scanning is triggered by the detection of the
leading edge of a bill, the chance that a scanned pattern will be offset
relative to a
corresponding master pattern increases. Offsets can result from the existence
of
manufacturing tolerances which permit the location of printed indicia of a
document
to vary relative to the edges of the document. For example, the printed
indicia on
U.S. bills may vary relative to the leading edge of a bill by as much as 50
mils
which is 0.05 inches (1.27 mm). Thus when scanning is triggered relative to
the
edge of a bill (rather than the detection of a certain part of the printed
indicia itself,
such as the printed borderline of U.S. bills), a scanned pattern can be offset
from a
corresponding master pattern by one or more samples. Such offsets can lead to
erroneous rejections of genuine bills due to poor correlation between scanned
and
master patterns. To compensate, overall scanned patterns and master patterns
can be
shifted relative to each other as illustrated in FIGs. 41a and 41b. More
particularly,
FIG. 41a illustrates a scanned pattern which is offset from a corresponding
master
CA 02215853 1997-11-06
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pattern. FIG. 41b illustrates the same patterns after the scanned pattern is
shifted
relative to the master pattern, thereby increasing the correlation between the
two
patterns. Alternatively, instead of shifting either scanned patterns or master
patterns,
master patterns may be stored in memory corresponding to different offset
amounts.
Thirdly, while it has been determined that the scanning of the central area on
the green side of a U.S. bill (see segment S of FIG. 4) provides sufficiently
distinct
patterns to enable discrimination among the plurality of U.S. denominations,
the
central area may not be suitable for bills originating in other countries. For
example,
for bills originating from Country 1, it may be determined that segment SI
(FIG. 40)
provides a more preferable area to be scanned, while segment S~ (FIG. 40) is
more
preferable for bills originating from Country 2. Alternatively, in order to
sufficiently
discriminate among a given set of bills, it may be necessary to scan bills
which are
potentially from such set along more than one segment, e.g., scanning a single
bill
along both S1 and SZ. To accommodate scanning in areas other than the central
portion of a bill, multiple scanheads may be positioned next to each other. A
preferred embodiment of such a multiple scanhead system is depicted in FIG.
42.
Multiple scanheads 1072a-c and 1072d-f are positioned next to each other along
a
direction lateral to the direction of bill movement. Such a system permits a
bill 1074
to be scanned along different segments. Multiple scanheads 1072a-f are
arranged on
each side of the transport path, thus permitting both sides of a bill 1074 to
be
scanned.
Two-sided scanning may be used to permit bills to be fed into a currency
discrimination system according to the present invention with either side face
up. An
example of a two-sided scanhead arrangement is described above in connection
with
FIGs. 2a, 6c, and 6d. Master patterns generated by scanning genuine bills may
be
stored for segments on one or both sides. In the case where master patterns
are
stored from the scanning of only one side of a genuine bill, the patterns
retrieved by
scanning both sides of a bill under test may be compared to a master set of
single-
sided master patterns. In such a case, a pattern retrieved from one side of a
bill
under test should match one of the stored master patterns, while a pattern
retrieved
from the other side of the bill under test should not match one of the master
patterns.
Alternatively, master patterns may be stored for both sides of genuine bills.
In such
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a two-sided system, a pattern retrieved by scanning one side of a bill under
test
should match with one of the master patterns of one side (Match 1) and a
pattern
retrieved from scanning the opposite side of a bill under test should match
the master
pattern associated with the opposite side of a genuine bill identified by
Match 1.
Alternatively, in situations where the face orientation of a bill (i.e.,
whether a
bill is "face up" or "face down") may be determined prior to or during
characteristic
pattern scanning, the number of comparisons may be reduced by limiting
comparisons
to patterns corresponding to the same side of a bill. That is, for example,
when it is
known that a bill is "face up", scanned patterns associated with scanheads
above the
transport path need only be compared to master patterns generated by scanning
the
"face" of genuine bills. By "face" of a bill it is meant a side which is
designated as
the front surface of the bill. For example, the front or "face" of a U.S. bill
may be
designated as the "black" surface while the back of a U.S. bill may be
designated as
the "green" surface. The face orientation may be determinable in some
situations by
sensing the color of the surfaces of a bill. An alternative method of
determining the
face orientation of U.S. bills by detecting the borderline on each side of a
bill is
described above in connection with FIGS. bc, 6d, and 12. The implementation of
color sensing is discussed in more detailed below.
According to the embodiment of FIG. 42, the bill transport mechanism
operates in such a fashion that the central area C of a bill 1074 is
transported
between central scanheads 1072b and 1072e. Scanheads 1072a and 1072c and
likewise scanheads 1072d and 1072f are displaced the same distance from
central
scanheads 1072b and 1072e, respectively. By symmetrically arranging the
scanheads
about the central region of a bill, a bill may be scanned in either direction,
e.g., top
edge first (forward direction) or bottom edge first (reverse direction). As
described
above with respect to FIGS. 1-7b, master patterns are stored from the scanning
of
genuine bills in both the forward and reverse directions. While a symmetrical
arrangement is preferred, it is not essential provided appropriate master
patterns are
stored for a non-symmetrical system.
While FIG. 42 illustrates a system having three scanheads per side, any
number of scanheads per side may be utilized. Likewise, it is not necessary
that
there be a scanhead positioned over the central region of a bill. For example,
FIG.
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43 illustrates another preferred embodiment of the present invention capable
of
scanning the segments Si and S2 of FIG. 40. Scanheads 1076a, 1076d, 1076e, and
1076h scan a bill 1078 along segment S, while scanheads 1076b, 1076c, 1076f,
and
10768 scan segment S,.
FIG. 44 depicts another preferred embodiment of a scanning system according
to the present invention having laterally moveable scanheads 1080a-b. Similar
scanheads may be positioned on the opposite side of the transport path.
Moveable
scanheads 1080a-b may provide more flexibility that may be desirable in
certain
scanning situations. Upon the determination of the dimensions of a bill as
described
in connection with FIG. 39, a preliminary determination of the identity of a
bill may
be made. Based on this preliminary determination, the moveable scanheads 1080a-
b
may be positioned over the area of the bill which is most appropriate for
retrieving
discrimination information. For example, if based on the size of a scanned
bill, it is
preliminarily determined that the bill is a Japanese 5000 Yen bill-type, and
if it has
IS been determined that a suitable characteristic pattern for a 5000 Yen bill-
type is
obtained by scanning a segment 2.0 cm to the left of center of the bill fed in
the
forward direction, scanheads i080a and 1080b may be appropriately positioned
for
scanning such a segment, e.g., scanhead 1O80a positioned 2.0 cm left of center
and
scanhead 1080b positioned 2.0 cm right of center. Such positioning permits
proper
discrimination regardless of the whether the scanned bill is being fed in the
forward
or reverse direction. Likewise scanheads on the opposite side of the transport
path
(not shown) could be appropriately positioned. Alternatively, a single
moveable
scanhead may be used on one or both sides of the transport path. In such a
system,
size and color information (to be described in more detail below) may be used
to
properly position a single laterally moveable scanhead, especially where the
orientation of a bill may be determined before scanning.
FIG. 44 depicts a system in which the transport mechanism is designed to
deliver a bill 1082 to be scanned centered within the area in which scanheads
1080a-b
are located. Accordingly, scanheads 1080a-b are designed to move relative to
the
center of the transport path with scanhead 1080a being moveable within the
range R,
and scanhead 1080b being moveable within range Rz.
CA 02215853 1997-11-06
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FIG. 45 depicts another preferred embodiment of a scanning system according
to the present invention wherein bills to be scanned are transported in a left
justified
manner along the transport path, that is wherein the left edge L of a bill
1084 is
positioned in the same lateral location relative to the transport path. Based
on the
dimensions of the bill, the position of the center of the bill may be
determined and
the scanheads 1086a-b may in turn be positioned accordingly. As depicted in
FIG.
45, scanhead 1086a has a range of motion R3 and scanhead 1086b has a range of
motion R4. The ranges of motion of scanheads 1086a-b may be influenced by the
range of dimensions of bills which the discrimination system is designed to
accommodate. Similar scanheads may be positioned on the opposite side of the
transport path.
Alternatively, the transport mechanism may be designed such that scanned
bills are not necessarily centered or justified along the lateral dimension of
the
transport path. Rather the design of the transport mechanism may permit the
position
of bills to vary left and right within the lateral dimension of the transport
path. In
such a case, the edge sensors 1066 of FIG. 39 may be used to locate the edges
and
center of a bill, and thus provide positional information in a moveable
scanhead
system and selection criteria in a stationary scanhead system.
In addition to the stationary scanhead and moveable scanhead systems
described above, a hybrid system having both stationary and moveable scanheads
may
be used. Likewise, it should be noted that the laterally displaced scanheads
described
above need not lie along the same lateral axis. That is, the scanheads may be,
for
example, staggered upstream and downstream from each other. FIG. 46 is a top
view of a staggered scanhead arrangement according to a preferred embodiment
of
the present invention. As illustrated in FIG. 46, a bill 1130 is transported
in a
centered manner along the transport path 1132 so that the center 1134 of the
bill 1130
is aligned with the center 1136 of the transport path 1132. Scanheads 1140a-h
are
arranged in a staggered manner so as to permit scanning of the entire width of
the
transport path 1132. The areas illuminated by each scanhead are illustrated by
strips
1142a, 1142b, 1142e, and 1142f for scanheads 1140a, 1140b, 1140e, and 1140f,
respectively. Based on size determination sensors, scanheads 1140a and 1140h
may
either not be activated or their output ignored.
CA 02215853 1997-11-06
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In general, if prior to scanning a document, preliminary information about a
document can be obtained, such as its size or color, appropriately positioned
stationary scanheads may be activated or laterally moveable scanheads may be
appropriately positioned provided the preliminary information provides some
indication as to the potential identity of the document. Alternatively,
especially in
systems having scanheads positioned over a significant portion of the
transport path,
many or all of the scanheads of a system may be activated to scan a document.
Then
subsequently, after some preliminary determination as to a document's identity
has
been made, only the output or derivations thereof of appropriately located
scanheads
may be used to generate scanned patterns. Derivations of output signals
include, for
example, data samples stored in memory generated by sampling output signals.
Under such an alternative embodiment, information enabling a preliminary
determination as to a document's identity may be obtained by analyzing
information
either from sensors separate from the scanheads or from one or more of the
scanheads themselves. An advantage of such preliminary determinations is that
the
number of scanned patterns which have to be generated or compared to a set of
master patterns is reduced. Likewise the number of master patterns to which
scanned
patterns must be compared may also be reduced.
While the scanheads 1140a-h of FIG. 46 are arranged in a non-overlapping
manner, they may alternatively be arranged in an overlapping manner. By
providing
additional lateral positions, an overlapping scanhead arrangement may provide
greater
selectivity in the segments to be scanned. This increase in scanable segments
may be
beneficial in compensating for currency manufacturing tolerances which result
in
positional variances of the printed indicia on bills relative to their edges.
Additionally, in a preferred embodiment, scanheads positioned above the
transport
path are positioned upstream relative to their corresponding scanheads
positioned
below the transport path.
FIGS. 47a and 47b illustrate another preferred embodiment of the present in
invention wherein a plurality of analog sensors 1150 such as photodetectors
are
laterally displaced from each other and are arranged in a linear array within
a single
scanhead 1152. FIG. 47a is a top view while FIG. 47b is a side elevation view
of
such a linear array embodiment. The output of individual sensors 1150 are
connected
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to analog-to-digital converters (not shown) through the use of graded index
fibers,
such as a "lens array" manufactured by MSG America, Inc.,, pan number
SLA20A1675702A3, and subsequently to a CPU (not shown) in a manner similar to
that depicted in FIGS. 1 and 6a. As depicted in FIGS. 47a and 47b, a bill 1154
is
transported past the linear array scanhead 1152 in a centered fashion. A
preferred
length for the linear array scanhead is about 6-7 inches (15 cm - 17 cm).
In a manner similar to that described above, based on the determination of the
size of a bill, appropriate sensors may be activated and their output used to
generate
scanned patterns. Alternatively many or all of the sensors may be activated
with only
the output or derivations thereof of appropriately located sensors being used
to
generate scanned patterns. Derivations of output signals include, for example,
data
samples stored in memory generated by sampling output signals. As a result, a
discriminating system incorporating a linear array scanhead according the
present
invention would be capable of accommodating a wide variety of bill-types.
Additionally, a linear array scanhead provides a great deal of flexibility in
how
information may be read and processed with respect to various bills. In
addition to
the ability to generate scanned patterns along segments in a direction
parallel to the
direction of bill movement, by appropriately processing scanned samples,
scanned
patterns may be "generated" or approximated in a direction perpendicular to
the
direction of bill movement. For example, if the linear array scanhead 1152
comprises one hundred and sixty (160) sensors 1150 over a length of 7 inches
(17.78
cm) instead of taking samples for 64 encoder pulses from say 30 sensors,
samples
may be taken for 5 encoder pulses from all 160 cells (or all those positioned
over the
bill 1154). Alternatively, 160 scanned patterns (or selected ones thereof) of
5 data
samples each may be used for pattern comparisons. Accordingly, it can be seen
that
the data acquisition time is significantly reduced from 64 encoder pulses to
only 5
encoder pulses. The time saved in acquiring data can be used to permit more
time to
be spent processing data and/or to reduce the total scanning time per bill
thus
enabling increased throughput of the identification system. Additionally, the
linear
array scanhead permits a great deal of flexibility in tailoring the areas to
be scanned.
For example, it has been found that the leading edge of Canadian bills contain
valuable graphic information. Accordingly, when it is determined that a test
bill may
CA 02215853 1997-11-06
115
be a Canadian bill (or when the identification system is set to a Canadian
currency
setting), the scanning area can be limited to the leading edge area of bills,
for
example, by activating many laterally displaced sensors for a relatively few
number
of encoder pulses.
FIG. 48 is a top view of another preferred embodiment of a linear array
scanhead 1170 having a plurality of analog sensors 1172 such as photodetectors
wherein a bill 1174 is transported past the scanhead 1170 in a non-centered
manner.
As discussed above, positional information from size determining sensors may
be
used to select appropriate sensors. Alternatively, the linear array scanhead
itself may
be employed to determine the size of a bill, thus eliminating the need for
separate
size determining sensors. For example, all sensors may be activated, data
samples
derived from sensors located on the ends of the linear array scanhead may be
preliminarily processed to determine the lateral position and the length of a
bill. The
width of a bill may be determined either by employing separate
leading/trailing edge
sensors or pre-processing data samples derived from initial and ending cycle
encoder
pulses. Once size information is obtained about a bill under test, only the
data
samples retrieved from appropriate areas of a bill need be further processed.
FIG. 49 is a top view of another preferred embodiment of a linear scanhead
1180 according to the present invention illustrating the ability to compensate
for
skewing of bills. Scanhead 1180 has a plurality of analog sensors 1182 and a
bill
1184 is transported past scanhead 1180 in a skewed manner. Once the skew of a
bill has been determined, for example through the use of leading edge sensors,
readings from sensors 1182 along the scanhead 1180 may be appropriately
delayed.
For example, suppose it is determined that a bill is being fed past scanhead
1180 so
that the left front corner of the bill reaches the scanhead five encoder
pulses before
the right front corner of the bill. In such a case, sensor readings along the
right edge
of the bill can be delayed for 5 encoder pulses to compensate for the skew.
Where
scanned patterns are to be generated over only a few encoder pulses, the bill
may be
treated as being fed in a non-skewed manner since the amount of lateral
deviation
between a scan along a skewed angle and a scan along a non-skewed angle is
minimal
for a scan of only a few encoder pulses. However, where it is desired to
obtain a
scan over a large number of encoder pulses, a single scanned pattern may be
CA 02215853 1997-11-06
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generated from the outputs of more than one sensor. For example, a scanned
pattern
may be generated by taking data samples from sensor 1186a for a given number
of
encoder pulses, then taking data samples from sensor 1186b for a next given
number
of encoder pulses, and then taking data samples from sensor 1186c for a next
given
number of encoder pulses. The number of given encoder pulses for which data
samples may be taken from the same sensor is influenced by the degree of skew,
the
greater the degree of skew of the bill, the fewer the number of data samples
which
may be obtained before switching to the next sensor. Alternatively, master
patterns
may be generated and stored for various degrees of skew, thus permitting a
single
sensor to generate a scanned pattern from a bill under test.
With regards to FIGs. 47-49, while only a single linear array scanhead is
shown, another linear array scanhead may be positioned on the opposite side of
the
transport path to permit scanning of either or both sides of a bill. Likewise,
the
benefits of using a linear array scanhead may also be obtainable using a
multiple
scanhead arrangement which is configured appropriately, for example such as
depicted in FIG. 46 or a linear arrangement of multiple scanheads.
In addition to size and scanned characteristic patterns, color may also be
used
to discriminate bills. For example, while all U.S. bills are printed in the
same
colors, e.g., a green side and a black side, bills from other countries often
vary in
color with the denomination of the bill. For example, a German 50 deutsche
mark
bill-type is brown in color while a German 100 deutsche mark bill-type is blue
in
color. Alternatively, color detection may be used to determine the face
orientation of
a bill, such as where the color of each side of a bill varies. For example,
color
detection may be used to determine the face orientation of U.S. bills by
detecting
whether or not the "green" side of a U.S. bill is facing upwards. Separate
color
sensors may be added upstream of the scanheads described above. According to
such
an embodiment, color information may be used in addition to size information
to
preliminarily identify a bill. Likewise, color information may be used to
determine
the face orientation of a bill which determination may be used to select upper
or
lower scanheads for scanning a bill accordingly or compare scanned patterns
retrieved
from upper scanheads with a set of master patterns generated by scanning a
corresponding face while the scanned patterns retrieved from the lower
scanheads are
CA 02215853 1999-OS-04
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compared with a set of master patterns generated by scanning an opposing face.
Alternatively, color sensing may be incorporated into the scanheads described
above.
Such color sensing may be achieved by, for example, incorporating color
filters,
colored light sources, and/or dichroic beamsplitters into the currency
discrimination
system of the present invention. Various color information acquisition
techniques are described in U.S. Patent Nos. 4,841,358; 4,658,289; 4,716,456;
4,825,246; and 4,992,860.
The operation of a currency discriminator according to a preferred
embodiment of the present invention may be further understood by referring to
the
flowchart of FIGs. SOa and SOb. In the process beginning at step 1100, a bill
is fed
along a transport path (step 1102) past sensors which measure the length and
width of
the bill (step 1104). These size determining sensors may be, for example,
those
illustrated in FIG. 39. Next at step 1106, it is determined whether the
measured
dimensions of the bill match the dimensions of at least one bill stored in
memory,
such as EPROM 60 of FIG. 7a. If no match is found, an appropriate error is
generated at step 1108. If a match is found, the color of the bill is scanned
for at
step 1110. At step 1112, it is determined whether the color of the bill
matches a
color associated with a genuine bill having the dimensions measured at step
1104.
An error is generated at step 1114 if no such match is found. However, if a
match is
found, a preliminary set of potentially matching bills is generated' at step
1116.
Often, only one possible identity will exist for a bill having a given color
and
dimensions. However, the preliminary set of step 1116 is not limited to the
identification of a single bill-type, that is, a specific denomination of a
specific
currency system; but rather, the preliminary set may comprise a number of
potential
bill-types. For example, all U.S. bills have the same size and color.
Therefore, the
preliminary set generated by scanning a U.S. $S bill would include U.S. bills
of all
denominations .
Based on the preliminary set (step 1116), selected scanheads in a stationary
scanhead system may be activated (step 1118). For example, if the preliminary
identification indicates that a bill being scanned has the color and
dimensions of a
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German 100 deutsche mark, the scanheads over regions associated with the
scanning
of an appropriate segment for a German 100 deutsche mark may be activated.
Then
upon detection of the leading edge of the bill by sensors 1068 of FIG. 40, the
appropriate segment may be scanned. Alternatively, all scanheads may be active
with
only the scanning information from selected scanheads being processed.
Alternatively, based on the preliminary identification of a bill (step 1116),
moveable
scanheads may be appropriately positioned (step 1118).
Subsequently, the bill is scanned for a characteristic pattern (step 1120). At
step 1122, the scanned patterns produced by the scanheads are compared with
the
stored master patterns associated with genuine bills as dictated by the
preliminary set.
By only making comparisons with master patterns of bills within the
preliminary set,
processing time may be reduced. Thus for example, if the preliminary set
indicated
that the scanned bill could only possibly be a German I00 deutsche mark, then
only
the master pattern or patterns associated with a German 100 deutsche mark need
be
compared to the scanned patterns. If no match is found, an appropriate error
is
generated (step 1124). If a scanned pattern does match an appropriate master
pattern,
the identity of the bill is accordingly indicated (step 1126) and the process
is ended
(step 1128).
While some of the preferred embodiments discussed above entailed a system
capable of identifying a plurality of bill-types, the system may be adapted to
identify
a bill under test as either belonging to a specific bill-type or not. For
example, the
system may be adapted to store master information associated with only a
single bill-
type such as a United Kingdom 5 pound bill. Such a system would identify bills
under test which were United Kingdom 5 pound bills and would reject all other
bill-
types.
The scanheads of the present invention may be incorporated into a document
identification system capable of identifying a variety of documents. For
example, the
system may be designed to accommodate a number of currencies from different
countries. Such a system may be designed to permit operation in a number of
modes. For example, the system may be designed to permit an operator to select
one
or more of a plurality of bill-types which the system is designed to
accommodate.
Such a selection may be used to limit the number of master patterns with which
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scanned patterns are to be compared. Likewise, the operator may be permitted
to
select the manner in which bills will be fed, such as all bills face up, all
bills top
edge first, random face orientation, and/or random top edge orientation.
Additionally, the system may be designed to permit output information to be
displayed in a variety of formats to a variety of peripherals, such as a
monitor, LCD
display, or printer. For example, the system may be designed to count the
number of
each specific bill-types identified and to tabulate the total amount of
currency counted
for each of a plurality of currency systems. For example, a stack of bills
could be
placed in the bill accepting station 12 of FIG. 2a-2b, and the output unit 36
of FIG.
2a-2b may indicate that a total of 370 British pounds and 650 German marks
were
counted. Alternatively, the output from scanning the same batch of bills may
prow ide
more detailed information about the specific denominations counted, for
example one
100 pound bill, five 50 pound bills, and one 20 pound bill and thirteen 50
deutsche
mark bills. Such a device would be useful in a bank teller environment. A bank
customer could hand the teller the above stack of bills. The teller could then
place
the stack of bills in the device. The device quickly scans the bills and
indicates that a
total of 370 British pounds and 650 German marks were counted. The teller
could
then issue the customer a receipt. At some point after the above transaction,
the
teller could separate the bills either by hand andlor by using an automatic
sorter
device located, for example, in a back room. The above transaction could then
be
performed rapidly without the customer being detained while the bills are
being
sorted.
In a document identification system capable of identifying a variety of bills
from a number of countries, a manual selection device, such as a switch or a
scrolling selection display, may be provided so that the operator may
designate what
type of currency is to be discriminated. For example, in a system designed to
accommodate both Canadian and German currency, the operator could turn a dial
to
the Canadian bill setting or scroll through a displayed menu and designate
Canadian
bills. By pre-declaring what type of currency is to be discriminated, scanned
patterns
need only be compared to master patterns corresponding to the indicated type
of
currency, e.g., Canadian bills. By reducing the number of master patterns
which
have to be compared to scanned patterns, the processing time can be reduced.
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Alternatively, a system may be designed to compare scanned patterns to all
stored master patterns. In such a system, the operator need not pre-declare
what type
of currency is to be scanned. This reduces the demands on the operator of the
device. Furthermore, such a system would permit the inputting of a mixture of
bills
from a number of countries. The system would scan each bill and automatically
determine the issuing country and the denomination.
In addition to the manual and automatic bill-type discriminating systems, an
alternate system employs a semi-automatic bill-type discriminating method.
Such a
system would work in a manner similar to the stranger mode described above. In
such a system, a stack of bills is placed in the input hopper. The first bill
is scanned
and the generated scanned pattern is compared with the master patterns
associated
with bills from a number of different countries. The discriminator identifies
the
country-type and the denomination of the bill. Then the discriminator compares
all
subsequent bills in the stack to the master patterns associated with bills
only from the
same country as the first bill. For example, if a stack of U.S. bills were
placed in
the input hopper and the first bill was a $5 bill, the first bill would be
scanned. The
scanned pattern would be compared to master patterns associated with bills
from a
number of countries, e.g., U.S., Canadian, and German bills. Upon determining
that
the first bill is a U.S. $5 bill, scanned patterns from the remaining bills in
the stack
are compared only to master patterns associated with U.S. bills, e.g., $1, $2,
$5,
$10, $20, $50, and $100 bills. When a bill fails to sufficiently match one of
the
compared patterns, the bill may be flagged as described above such as by
stopping
the transport mechanism with the flagged bill being the last bill deposited in
the
output receptacle.
A currency discriminating device designed to accommodate both Canadian and
German currency bills will now be described. According to this preferred
embodiment, a currency discriminating device similar to that described above
in
connection with scanning U.S. currency (see, e.g., FIGs. 1-38 and accompanying
description) is modified so as to be able to accept both Canadian and German
currency bills. According to a preferred embodiment when Canadian bills are
being
discriminated, no magnetic sampling or authentication is performed.
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Canadian bills have one side with a portrait (the portrait side) and a reverse
side with a picture (the picture side). Likewise, German bills also have one
side with
a portrait (the portrait side) and a reverse side with a picture (the picture
side). In a
preferred embodiment, the discriminator is designed to accept either stacks of
Canadian bills or stacks of German bills, the bills in the stacks being faced
so that the
picture side of all the bills will be scanned by a triple scanhead arrangement
to be
described in connection with FIG. S 1. In a preferred embodiment, this triple
scanhead replaces the single scanhead arrangement housed in the unitary molded
plastic support member 280 (see, e.g., FIGs. 25 and 26).
FIG. 51 is a top view of a triple scanhead arrangement 1200. The triple
scanhead arrangement 1200 comprises a center scanhead 1202, a left scanhead
1204,
and a right scanhead 1206 housed in a unitary molded plastic support member
1208.
A bill 1210 passes under the arrangement 1200 in the direction shown. O-rings
are
positioned near each scanhead, preferably two 0-rings per scanhead, one on
each side
of a respective scanhead, to engage the bill continuously while transporting
the bill
between rolls 223 and 241 (FIG. 20a) and to help hold the bill flat against
the guide
plate 240 (FIG. 20a). The left 1204 and right 1206 scanhead are placed
slightly
upstream of the center scanhead 1202 by a distance D3. In a preferred
embodiment,
D3 is 0.083 inches (0.21 cm). The center scanhead 1202 is centered over the
center
C of the transport path 1216. The center L.c of the left scanhead 1204 and the
center
R~ of the right scanhead 1206 are displaced laterally from center C of the
transport
path in a symmetrical fashion by a distance D~. In a preferred embodiment D4
is
1.625 inches (4.128 cm).
The scanheads 1202, 1204, and 1206 are each similar to the scanheads
describe above connection with FIGS. 1-38, except only a wide slit having a
length of
about 0.500" and a width of about 0.050" is utilized. The wide slit of each
scanhead
is used both to detect the leading edge of a bill and to scan a bill after the
leading
edge has been detected.
Two photosensors 1212 and 1214 are located along the lateral axis of the left
and right scanheads 1204 and 1206, one on either side of the center scanhead
1202.
Photosensors 1212 and 1214 are same as the photosensors PS1 and PS2 describe
above (see, e.g., FIGs. 26 and 30). Photosensors 1212 and 1214 are used to
detect
CA 02215853 1997-11-06
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doubles and also to measure the dimension of bills in the direction of bill
movement
which in the preferred embodiment depicted in FIG. 51 is the narrow dimension
of
bills. Photosensors 1212 and 1214 are used to measure the narrow dimension of
a
bill by indicating when the leading and trailing edges of a bill passes by the
photosensors 1212 and 1214. This information in combination with the encoder
information permits the narrow dimension of a bill to be measured.
All Canadian bills are 6" (15.24 cm) in their long dimension and 2.75" (6.985
cm) in their narrow dimension. German bills vary in size according to
denomination.
In a preferred embodiment of the currency discriminating system, the
discriminating
device is designed to accept and discriminate $2, $5, $10, $20, $50, and $100
Canadian bills and 10 DM, 20 DM, 50 DM, and 100 DM German bills. These
German bills vary in size from 13.0 cm (5.12") in the long dimension by 6.0 cm
(2.36") in the narrow dimension for 10 DM bills to 16.0 cm (6.30") in the long
dimension by 8.0 cm (3.15") in the narrow dimension for 100 DM bills. The
input
hopper of the discriminating device is made sufficiently wide to accommodate
all the
above listed Canadian and German bills, e.g., 6.3" (16.0 cm) wide.
FIG. 52 is a top view of a Canadian bill illustrating the areas scanned by the
triple scanhead arrangement of FIG. 51. In generating scanned patterns from a
Canadian bill 1300 traveling along a transport path 1301, segments SL,, SC,,
and SRl
are scanned by the left 1204, center 1202, and right 1206 scanheads,
respectively, on
the picture side of the bill 1300. These segments are similar to segment S in
FIG. 4.
Each segment begins a predetermined distance DS inboard of the leading edge of
the
bill. In a preferred embodiment DS is 0.5" (1.27 cm). Segments SLI, SC1, and
SRl
each comprise 64 samples as shown in FIGs. 3 and S. In a preferred embodiment
Canadian bills are scanned at a rate of 1000 bills per minute. The lateral
location of
segments SL,, SC1, and SRl is fixed relative to the transport path 1301 but
may vary
left to right relative to bill 1300 since the lateral position of bill 1300
may vary left to
right within the transport path 1301.
A set of eighteen (18) master Canadian patterns are stored for each type of
Canadian bill that the system is designed to discriminate, three (3) for each
scanhead
in both the forward and reverse directions. For example, three patterns are
generated
by scanning a given genuine Canadian bill in the forward direction with the
center
CA 02215853 1997-11-06
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scanhead. One pattern is generated by scanning down the center of the bill
along
segment SC,, a second is generated by scanning along a segment SCE initiated
1.5
samples before the beginning of SCl, and a third is generated by scanning
along a
segment SC3 initiated i.5 samples after the beginning of SC,. The second and
third
patterns are generated to compensate for the problems associated with
triggering off
the edge of a bill as discussed above.
To compensate for possible lateral displacement of bills to be scanned along a
direction transverse to the direction of bill movement, the exact lateral
location along
which each of the above master patterns is generated is chosen after
considering the
correlation results achieved when a bill is displaced slightly to the left or
to the right
of the center of each scanhead, i.e., lines Lc, Sc, and R~. For example, in
generating a master pattern associated with segment SC,, a scan of a genuine
bill may
be taken down the center of a bill, a second scan may be taken along a segment
0.15" to the right of center (+0.15"), and a third scan may be taken along a
segment
0.15" to the left of center (-0.15"). Based on the correlation result
achieved, the
actual scan location may be adjusted slightly to the right or left so the
effect of the
lateral displacement of a bill on the correlation results is minimized. Thus,
for
example, the master pattern associated with a forward scan of a Canadian $2
bill
using the center scanhead 1202 may be taken along a line 0.05" to the right of
the
center of the bill.
Furthermore, the above stored master patterns are generated either by
scanning both a relatively new crisp genuine bill and an older yellowed
genuine bill
and averaging the patterns generated from each or, alternatively, by scanning
an
average looking bill.
Master patterns are stored for nine (9) types of Canadian bills, namely, the
newer series $2, $5, $10, $20, $50, and $100 bills and the older series $20,
$50, and
$100 bills. Accordingly, a total of 162 Canadian master patterns are stored (9
types
x 18 per type) .
FIG. 53 is a flowchart of the threshold test utilized in calling the
denomination
of a Canadian bill. When Canadian bills are being discriminated the flowchart
of
FIG. 53 replaces the flowchart of FIG. 13. The correlation results associated
with
correlating a scanned pattern to a master pattern of a given type of Canadian
bill in a
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Qiven scan direction and a given offset in the direction of bill movement from
each of
the three scanheads are summed. The highest of the resulting 54 summations is
designated the #1 correlation and the second highest is preliminarily
designated the #2
correlation. The #1 and #2 correlations each have a given bill type associated
with
them. If the bill type associated with the #2 correlation is merely a
different series
from, but the same denomination as, the bill type associated with the #1
denomination, the preliminarily designated #2 correlation is substituted with
the next
highest correlation where the bill denomination is different from the
denomination of
the bill type associated with the #1 correlation.
The threshold test of FIG. 53 begins at step 1302. Step 1304 checks the
denomination associated with the #1 correlation. If the denomination
associated with
the #1 correlation is not a $50 or $100, the #1 correlation is compared to a
threshold
of 1900 at step 1306. If the #1 correlation is less than or equal to 1900, the
correlation number is too low to identify the denomination of the bill with
certainty.
Therefore, step 1308 sets a "no call" bit in a correlation result flag and the
system
returns to the main program at step 1310. If, however, the #1 correlation is
greater
than 1900 at step 1306, the system advances to step 1312 which determines
whether
the #1 correlation is greater than 2000. If the #1 correlation is greater than
2000, the
correlation number is sufficiently high that the denomination of the scanned
bill can
be identified with certainty without any further checking. Consequently, a
"good
call" bit is set in the correlation result flag at step 1314 and the system
returns to the
main program at step 1310.
If the #1 correlation is not greater than 2000 at step 1312, step 1316 checks
the denomination associated with the #2 correlation. If the denomination
associated
with the #2 correlation is not a $50 or $100, the #2 correlation is compared
to a
threshold of 1900 at step 1318. If the #2 correlation is less than or equal to
1900,
the denomination identified by the #1 correlation is acceptable, and thus the
"good
call" bit is set in the correlation result flag at step 1314 and the system
returns to the
main program at step 1310. If, however, the #2 correlation is greater than
1900 at
step 1318, the denomination of the scanned bill cannot be identified with
certainty
because the #1 and #2 correlations are both above 1900 and, yet, are
associated with
CA 02215853 1997-11-06
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different denominations. Accordingly, the "no call" bit is set in the
correlation result
flag at step 1308.
If the denomination associated with the #2 correlation is a $$0 or $100 at
step
1316, the #2 correlation is compared to a threshold of 1$00 at step 1320. If
the #2
$ correlation is less than or equal to 1$00, the denomination identified by
the #1
correlation is acceptable, and thus the "good call" bit is set in the
correlation result
flag at step 1314 and the system returns to the main program at step 1310. If,
however, the #2 correlation is greater than 1$Ofl at step 1320, the
denomination of
the scanned bill cannot be identified with certainty. As a result, the "no
call" bit is
set in the correlation result flag at step 1308.
If the denomination associated with the #1 correlation is a $$0 or $100 at
step
1304, the #1 correlation is compared to a threshold of 1500 at step 1322. If
the #1
correlation is less than or equal to 1$00, the denomination of the scanned
bill cannot
be identified with certainty and; therefore, the "no call" bit is set in the
correlation
result flag at step 1308. If, however, the #1 correlation at step 1322 is
greater than
1$00, the system advances to step 1312 which determines whether the #1
correlation
is greater than 2000. If the #1 correlation is greater than 2000,.the
correlation
number is sufficiently high that the denomination of the scanned bill can be
identified
with certainty without any further checking. Consequently, a "good call" bit
is set in
the correlation result flag at step 1314 and the system returns to the main
program at
step 1310.
If the #1 correlation is not greater than 2000 at step 1312, step 1316 checks
the denomination associated with the #2 correlation. If the denomination
associated
with the #2 correlation is not a $$0 or $100, the #2 correlation is compared
to a
2$ threshold of 1900 at step 1318. If the #2 correlation is less than or equal
to 1900,
the denomination identified by the #1 correlation is acceptable, and thus the
"good
call" bit is set in the correlation result flag at step 1314 and the system
returns to the
main program at step 1310. If, however, the #2 correlation is greater than
1900 at
step 1318, the denomination of the scanned bill cannot be identified with
certainty.
Accordingly, the "no call" bit is set in the correlation result flag at step
1308.
If the denomination associated with the #2 correlation is a $$0 or $100 at
step
1316, the #2 correlation is compared to a threshold of 1$00 at step 1320. If
the #2
CA 02215853 1997-11-06
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correlation is less than or equal to 1500, the denomination identified by the
# 1
correlation is acceptable, and thus the "good call" bit is set in the
correlation result
flag at step 1314 and the system returns to the main program at step 1310. If,
however, the #2 correlation is greater than 1500 at step 1320, the
denomination of
the scanned bill cannot be identified with certainty. As a result, the "no
call" bit is
set in the correlation result flag at step 1308 and the system returns to the
main
program at step 1310.
Now the use of the triple scanhead arrangement 1200 in scanning and
discriminating German currency will be described. When scanning German bills,
only the output of the center scanhead 1202 is utilized to generate scanned
patterns.
A segment similar to segment S of FIG. 4 is scanned over the center of the
transport
path at a predetermined distance D6 inboard after the leading edge of a bill
is
detected. In a preferred embodiment D6 is 0.25" (0.635 cm). The scanned
segment
comprises 64 samples as shown in FIGs. 3 and 5. In a preferred embodiment
German bills are scanned at a rate of 1000 bills per minute. The lateral
location of
the scanned segment is fixed relative to the transport path 1216 but may vary
left to
right relative to bill 1210 since the lateral position of bill 1210 may vary
left to right
within the transport path 1216.
FIG. 54a illustrates the general areas scanned in generating master 10 DM
German patterns. Due to the short length of 10 DM bills in their long
dimension
relative to the width of the transport path, thirty (30) 10 DM master patterns
are
stored. A first set of five patterns are generated by scanning a genuine 10 DM
bill
1400 in the forward direction along laterally displaced segments all beginning
a
predetermined distance D6 inboard of the leading edge of the bill 1400. Each
of
these five laterally displaced segments is centered about a respective one of
lines Ll-
L5. One such segment S 101 centered about line L, is illustrated in FIG. 54a.
Line L,
is disposed down the center C of the bill 1400. In a preferred embodiment
lines L,-
LS are disposed in a symmetrical fashion about the center C of the bill 1400.
In a
preferred embodiment lines L2 and L~ are laterally displaced from L, by a
distance D~
where D, is 0.24" (0.6 i cm) and lines L4 and LS are laterally displaced from
Ll by a
distance D$ where D$ is 0.48" (1.22 cm).
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127
A second set of five patterns are generated by scanning a genuine 10 DM bill
1400 in the forward direction along laterally displaced segments along lines
Ll-LS all
beginning at a second predetermined distance inboard of the leading edge of
the bill
1400, the second predetermined distance being less than the predetermined
distance
D6. One such segment S 10, centered about line L, is illustrated in FIG. 54a.
In a
preferred embodiment the second predetermined distance is such that scanning
begins
one sample earlier than D6, that is about 30 mils before the initiation of the
patterns
in the first set of five patterns.
A third set of five patterns are generated by scanning a genuine 10 DM bill
1400 in the forward direction along laterally displaced segments along lines
L,-LS all
beginning at a third predetermined distance inboard of the leading edge of the
bill
1400, the third predetermined distance being greater than the predetermined
distance
D6. One such segment S 103 centered about line L, is illustrated in FIG: 54a.
In a
preferred embodiment the third predetermined distance is such that scanning
begins
one sample later than D6, that is about 30 mils after the initiation of the
patterns in
the first set of five patterns.
The above three sets of five patterns yield fifteen patterns in the forward
direction. Fifteen additional IO DM master patterns taken in the manner
described
above but in the reverse direction are also stored.
FIG. 54b illustrates the general areas scanned in generating master 20 DM, 50
DM, and 100 DM German patterns. Due to the lengths of 20 DM, 50 DM, and 100
DM bills in their long dimension being shorter than the width of the transport
path,
eighteen (18) 20 DM master patterns, eighteen (18) 50 DM master patterns, and
eighteen (18) 100~DM master patterns are stored. The 50 DM master patterns and
the 100 DM master patterns are taken in the same manner as the 20 DM master
patterns except that the 50 DM master patterns and 100 DM master patterns are
generated from respective genuine 50 DM bills and 100 DM bills while the 20 DM
master patterns are generated from genuine 20 DM bills. Therefore, only the
generation of the 20 DM master patterns will be described in detail.
A first set of three patterns are generated by scanning a genuine 20 DM bill
1402 in the forward direction along laterally displaced segments all beginning
a
predetermined distance D6 inboard of the leading edge of the bill 1402. Each
of
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these three laterally displaced segments is centered about a respective one of
lines L6
L8. One such segment S20, centered about line L.6 is illustrated in FIG. 54b.
Line
L6 is disposed down the center C of the bill 1402. In a preferred embodiment
lines
L,-Lg are disposed in a symmetrical fashion about the center C of the bill
1402. In a
preferred embodiment lines L, and Ls are laterally displaced from L6 by a
distance D9
where D9 is 0.30" (0.76 cm) for the 20 DM bill. The value of D9 is 0.20" (0.51
cm)
for the 50 DM bill and 0.10" (0.25 cm) for the 100 DM bill.
A second set of three patterns are generated by scanning a genuine 20 DM bill
1402 in the forward direction aivng laterally displaced segments along lines
L6 Lg all
beginning at a second predetermined distance inboard of the leading edge of
the bill
1402, the second predetermined distance being less than the predetermined
distance
D6. One such segment 520 centered about line L6 is illustrated -in FIG. 54b:
In a
preferred embodiment the second predetermined distance is such that scanning
begins
one sample earlier than D6, that is about 30 mils before the initiation of the
patterns
in the first set of three patterns.
A third set of three patterns are generated by scanning a genuine 20 DM bill
1402 in the forward direction along laterally displaced segments along lines
L6-Lg all
beginning at a third predetermined distance inboard of the leading edge of the
bill
1402, the third predetermined distance being greater than the predetermined
distance
D6. One such segment 5203 centered about line L6 is illustrated il FIG. 54b.
In a
preferred embodiment the third predetermined distance is such that scanning
begins
one sample later than D6, that is about 30 mils after the initiation of the
patterns in
the first set of three patterns.
The above three sets of three patterns yield nine patterns in the forward
direction. Nine additional 20 DM master patterns taken in the manner described
above but in the reverse direction are also stored. Furthermore, the above
stored
master patterns are generated either by scanning both a relatively new crisp
genuine
bill and an older yellowed genuine bill and averaging the patterns generated
from
each or, alternatively, by scanning an average looking bill.
This yields a total of 84 German master patterns (30 for 10 DM bills, 18 for
20 DM bills, 18 for 50 DM bills, and 18 for 100 DM bills). To reduce the
number
of master patterns that must compared to a given scanned pattern, the narrow
CA 02215853 1997-11-06
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dimension of a scanned bill is measured using photosensors 1212 and 1214.
After a
given bill has been scanned by the center scanhead 1202, the generated scanned
pattern is correlated only against certain ones of above described 84 master
patterns
based on the size of the narrow dimension of the bill as determined by the
photosensors 1212 and 1214. The narrow dimension of each bill is measured
independently by photosensors 1212 and 1214 and then averaged to indicate the
length of the narrow dimension of a bill. In particular, a first number of
encoder
pulses occur between the detection of the leading and trailing edges of a bill
by the
photosensor 1212. Likewise, a second number of encoder pulses occur between
the
detection of the leading and trailing edges of the bill by the photosensor
1214. These
first and second numbers of encoder pulses are averaged to indicate the length
of the
narrow dimension of the bill in terms of encoder pulses.
The photosensors 1212 and 1214 can also determine the degree of skew of a
bill as it passes by the triple scanhead arrangement 1200. By counting the
number of
encoder pulses between the time when photosensors 1212 and 1214 detect the
leading
edge of a bill, the degree of skew can be determined in terms of encoder
pulses. If
no or little skew is measured, a generated scanned pattern is only compared to
master
patterns associated with genuine bills having the same narrow dimension
length. If a
relatively large degree of skew is detected, a scanned pattern will be
compared with
master patterns associated with genuine bills having the next smaller
denominational
amount than would be indicated by the measured narrow dimension length.
Table 4 indicates which denominational set of master patterns are chosen for
comparison to the scanned pattern based on the measured narrow dimension
length in
terms of encoder pulses and the measured degree of skew in terms of encoder
pulses:
TABLE 4
Narrow Dimension Degree of Skew in Selected Set of Master
Length in Encoder Encoder Pulses Patterns
Pulses
< 1515 Not applicable 10 DM
>_ 1515 and < 1550 >_ 175 10 DM
>_ 1515 and < 1550 < 175 20 DM
_> 1550 and < 1585 ~ 300 10 DM
CA 02215853 1997-11-06
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>_ 1550and< 1585 < 300 20 DM
>_ 1585and< 1620 >_200 20 DM
>_ 1585and< 1620 < 200 50 DM
>_ 1620and< 1b55 >_300 20 DM
>_ 1620and< 1655 < 300 50 DM
>_ 1655and< 1690 >_150 SO DM
>_ 1655and< 1690 < 150 100 DM
>_ 1690and< 1725 >_300 50 DM
>_ 1690 < 1725 < 300 100 DM
and
>_ 1725 Not 100 DM
applicable
FIG. 55 is a flowchart of the threshold test utilized in calling the
denomination
of a German bill. It should be understood that this threshold test compares
the
scanned bill pattern only to the set of master patterns selected in accordance
with
Table 4. Therefore, the selection made in accordance with Table 4 provides a
preliminary indication as to the denomination of the scanned bill. The
threshold test
in FIG. 55, in effect, serves to confirm or overturn the preliminary
indication given
by Table 4.
The threshold test of FIG. 55 begins at step 1324. Step 1326 checks the ,
narrow dimension length of the scanned bill in terms of encoder pulses. If the
narrow dimension length is less than 1515 at step 1326, the preliminary
indication is
that the denomination of the scanned bill is a 10 DM bill. In order to confirm
this
preliminary indication, the #1 correlation is compared to 550 at step 1328. If
the #1
correlation is greater than 550, the correlation number is sufficiently high
to identify
the denomination of the bill as a 10 DM bill. Accordingly, a "good call" bit
is set in
a correlation result flag at step 1330, and the system returns to the main
program at
step 1332. If, however, the #1 correlation is less than or equal to 550 at
step 1328,
the preliminary indication that the scanned bill is a 10 DM bill is
effectively
overturned. The system advances to step 1334 which sets a "no call" bit in the
correlation result flag.
CA 02215853 1997-11-06
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If step 1326 determines that the narrow dimension length is greater than or
equal to 1515, a correlation threshold of 800 is required to confirm the
preliminary
denominational indication provided by Table 4. Therefore, if the #1
correlation is
greater than 800 at step 1336, the preliminary indication provided by Table 4
is
confirmed. To confirm the preliminary indication, the "good call" bit is set
in the
correlation result flag. If, however, the #1 correlation is less than or equal
to 800 at
step 1336, the preliminary indication is rejected and the "no call" bit in the
correlation result flag is set at step 1334. The system then returns to the
main
program at step 1332.
According to a preferred embodiment, the operator of the above described
currency discriminating device designed to accommodate both Canadian and
German
currency bills pre-declares whether Canadian or German bills are to be
discriminated.
By depressing an appropriate key on the keypad 62 (FiG. 59), the display 63
will
scroll through five different modes: a count mode, a Canadian stranger mode, a
l~ Canadian mixed mode, a German stranger mode, and a German mixed mode. In
the
count mode, the device acts like a simply bill counter (counting the number of
bills in
a stack but not discriminating them by denomination). Canadian stranger mode
is
similar to the stranger mode described below in connection with FIG. 59 but
bills are
scanned as described above in connection with FIG. 52 and scanned patterns are
correlated against Canadian master patterns. Likewise, Canadian mixed mode is
similar to the mixed mode described below in connection with FIG. 59 but bills
are
scanned as described above in connection with FIG. 52 and scanned patterns are
correlated against Canadian master patterns. Likewise German stranger and
German
mixed mode are similar to the stranger and mixed modes described below in
2~ connection with FIG. 59 but bills are scanned as described above in
connection with
the scanning of German bills and scanned patterns are correlated against
German
master patterns.
FIG. 56 is a functional block diagram illustrating another preferred
embodiment of a currency discriminator system 1662 according to the present
invention. The discriminator system 1662 comprises an input receptacle 1664
for
receiving a stack of currency bills. A transport mechanism (as represented by
arrows
A and B) transports the bills in the input receptacle passed an authenticating
and
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132
discriminating unit 1666 to an output receptacle 1668 where the bills are re-
stacked
such that each bill is stacked on top of or behind the previous bill so that
the most
recent bill is the top-most or rear-most bill. The authenticating and
discriminating
unit scans and determines the denomination of each passing bill. Any variety
of
discriminating techniques may be used. For example, the discriminating method
disclosed in U.S. Pat. No. 5,295,196 may be
employed to optically scan each bill. Depending on the characteristics of the
discriminating unit employed, the discriminator may be able to recognize bills
only if
fed face up or face down, regardless of whether fed face up or face down, only
if fed
in a forward orientation or reverse orientation, regardless of whether fed in
a forward
or reverse orientation, or some combination thereof. Additionally, the
discriminating
unit may be able to scan only one side or both sides of a bill. In addition to
determining the denomination of each scanned bill, the authenticating and
discriminating unit 1666 may additionally include various authenticating tests
such as
an ultraviolet authentication test as disclosed in U.S. Patent No. 5,640,463
issued June
17, 1997 for a "Method and Apparatus for Authenticating Documents Including
Currency."
Signals from the authenticating and discriminating unit 1666 are sent to a
signal processor such as a central processor unit ("CPU") 1670. The CPU 1670
records of results of the authenticating and discriminating tests in a memory
1672.
When the authenticating and discriminating unit 1666 is able to confirm the
genuineness and denomination of a bill, the value of the bill is added to a
total value
counter in memory 1672 that keeps track of the total value of the stack of
bills that
were inserted in the input receptacle 1664 and scanned by the authenticating
and
discriminating unit 1666. Additionally, depending on the mode of operation of
the
discriminator system 1662, counters associated with one or more denominations
are
maintained in the memory 1672. For example, a $1 counter may be maintained to
record how many $1 bills were scanned by the authenticating and discriminating
unit
1666. Likewise, a $5 counter may be maintained to record how many $S bills
were
scanned, and so on. In an operating mode where individual denomination
counters
are maintained, the total value of the scanned bills may be determined without
maintaining a separate total value counter. The total value of the scanned
bills and/or
CA 02215853 1997-11-06
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the number of each individual denomination may be displayed on a display 1674
such
as a monitor or LCD display.
As discussed above, a discriminating unit such as the authenticating and
discriminating unit 1666 may not be able to identify the denomination of one
or more
bills in the stack of bills loaded into the input receptacle 1664. For
example, if a bill
is excessively worn or soiled or if the bill is torn a discriminating unit may
not be
able to identify the bill. Furthermore, some known discrimination methods do
not
have a high discrimination efficiency and thus are unable to identify bills
which vary
even somewhat from an "ideal" bill condition or which are even somewhat
displaced
by the transport mechanism relative to the scanning mechanism used to
discriminate
bills. Accordingly, such poorer performing discriminating units may yield a
relatively large number of bills which are not identified. Alternatively, some
discriminating units may be capable of identifying bills only when they are
fed in a
predetermined manner. For example, some discriminators may require a bill to
be
faced in a predetermined manner. Accordingly, when a bill is fed face down
passed
a discriminating unit which can only identify bills fed face up, the
discriminating unit
can not identify the bill. Likewise, other discriminators require a specific
edge of a
bill to be fed first, for example, the top edge of a bill. Accordingly, bills
which are
not fed in the forward direction, that is, those that are fed in the reverse
direction,
are not identified by such a discriminating unit.
According to a preferred embodiment, the discriminator system 1662 is
designed so that when the authenticating and discriminating unit is unable to
identify
a bill, the transport mechanism is stopped so that the unidentified bill is
the last bill
transported to the output receptacle. After the transport mechanism stops, the
unidentified bill is then, for example, positioned at the top of or at the
rear of the
stack of bills in the output receptacle 1668. The output receptacle 1668 is
preferably
positioned within the discriminator system 1662 so that the operator may
conveniently
see the flagged bill and/or remove it for closer inspection. Accordingly, the
operator
is able to easily see the bill which has not been identified by the
authenticating and
discriminating unit 1666. The operator may then either visually inspect the
flagged
bill while it is resting on the top of or at the rear of the stack, or
alternatively, the
operator may chose to remove the bill from the output receptacle in order to
examine
CA 02215853 1997-11-06
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the flagged bill more closely. The discriminator system 1662 may be designed
to
continue operation automatically when a flagged bill is removed from the
output
receptacle or, according to a preferred embodiment of the present invention,
may be
designed to require a selection element to be depressed. Upon examination of a
flagged bill by the operator, it may be found that the flagged bill is genuine
even
though is was not identified by the discriminating unit. However, because the
bill
was not identif ed, the total value and/or denomination counters in the memory
1672
will not reflect its value. According to one embodiment, such an unidentified
bill is
removed from the output stack and either re-fed through the discriminator or
set
aside. In the latter case, any genuine set aside bills are counted by hand.
In prior discriminators, unidentified discriminators were routed to a separate
reject receptacle. In such systems, an unidentified genuine bill would have to
be
removed from a reject receptacle and re-fed through the discriminator or the
stack of
rejected bills would have to be counted by hand and the results separately
recorded.
1 S Furthermore, because re-fed bills have gone unidentified once, they are
more likely
to go unidentified again and ultimately may have to be counted by hand.
However,
as discussed above, such procedures may increase the chance for human error or
at
least lower the efficiency of the discriminator and the operator.
In order to avoid problems associated with re-feeding bills, counting bills by
hand. and adding together separate totals, according to a preferred embodiment
of the
present invention a number of selection elements associated with individual
denominations are provided. In FIG. 56, these selection elements are in the
form of
keys or buttons of a keypad 1676 or 62. Other types of selection elements such
as
switches or displayed keys in a touch-screen environment may be employed. The
2~ operation of the selection elements will be described in more detail in
connection with
FIG. 59 but briefly when an operator determines that a flanged bill is
acceptable, the
operator may simply depress the selection element associated with the
denomination
of the flagged bill and the corresponding denomination counter and/or the
total value
counter are appropriately incremented and the discriminator system 1662 or 10
resumes operating again. As discussed above, a bill may be flagged for any
number
of reasons including the bill being a no call or suspect bill. In non-
automatic restart
discriminators, where an operator has removed a genuine flagged bill from the
output
CA 02215853 1997-11-06
135
receptacle for closer examination, the bill is first replaced into the output
receptacle
before a corresponding selection element is chosen. When an operator
determines
that a flagged bill is not acceptable, the operator may remove the
unacceptable
flagged bill from the output receptacle without replacement and depress a
continuation key on the keypad 1676 or 62. When the continuation key is
selected
the denomination counters and the total value counter are not affected and the
discriminator system 1662 or 10 will resume operating again. In automatic
restart
discriminators, the removal of a bill from the output receptacle is treated as
an
indication that the bill is unacceptable and the discriminator automatically
resumes
operation without affecting the denomination counters and/or total value
counters.
An advantage of the above described procedure is that appropriate counters are
incremented and the discriminator is restarted with the touch of a single key,
greatly
simplifying the operation of the discriminator system 1662 or 10 while
reducing the
opportunities for human error.
Turning now to FIG. 57, there is shown a functional block diagram
illustrating another preferred embodiment of a document authenticator and
discriminator according to the present invention. The discriminator system
1680
comprises an input receptacle 1682 for receiving a stack of currency bills. A
transport mechanism (as represented by arrow C) transports the bills in the
input
receptacle, one at a time, passed an authenticating and discriminating unit
1684.
Based on the results of the authenticating and discriminating unit 1684, a
bill is either
transported to one of a plurality of output receptacles 1686 (arrow D), to a
reject
receptacle 1688 (arrow E), or to an operator inspection station 1690 (arrow
F).
When is bill is determined to be genuine and its denomination has been
identified, the
2~ bill is transported to an output receptacle associated with its
denomination: For
example, the discriminator system 1680 may comprise seven output receptacles
1686,
one associated with each of seven U.S. denominations, i.e., $1, $2, $5, $10,
$20,
$50, and $100. The transport mechanism directs (arrow D) the identified bill
to the
corresponding output receptacle. Alternatively, where the authenticating and
discriminating unit determines that a bill is a fake, the bill is immediately
routed
(arrow E) to the reject receptacle 1688. Finally, if a bill is not determined
to be fake
but for some reason the authenticating and discriminating unit 1684 is not
able to
CA 02215853 1997-11-06
136
identify the denomination of the bill, the flagged bill is routed (arrow F) to
an
inspection station and the discriminator system 1680 stops operating. The
inspection
station is preferably positioned within the discriminator system 1680 so that
the
operator may conveniently see the flagged bill and/or remove it for closer
inspection.
If the operator determines that the bill is acceptable, the operator returns
the bill to
the inspection station if it was removed and selects a. selection element (not
shown)
corresponding to the denomination of the flagged bill. Appropriate counters
(not
shown) are incremented, the discriminator system 1680 resumes operation, and
the
flagged bill is routed (arrow G) to the output receptacle associated with the
chosen
selection element. On the other hand, if the operator determines that the
flagged bill
is unacceptable, the operator returns the bill to the inspection station if it
was
removed and selects a continuation element (not shown). The discriminator
system
1680 resumes operation, and the flagged bill is routed (arrow H) to the reject
receptacle 1688 without incrementing the counters associated with the various
denomination and/or the total value counters. Alternatively, the discriminator
system
1680 may permit the operator to place any unacceptable unidentified bills
aside or
into the reject receptacle by hand. While transport paths D and G and paths E
and H
are illustrated as separate paths, paths D and G and paths E and H,
respectively, may
be the same path so that all bills proceeding to either one of the output
receptacles
1686 or the reject receptacle 1688, respectively, are routed through the
inspection
station 1690.
. Turning now to FIG. 58, there is shown a functional block diagram
illustrating another preferred embodiment of a document authenticator and
discriminator according to the present invention.. The discriminator system
1692
comprises an input receptacle 1694 for receiving a stack of currency bills. A
transport mechanism (as represented by arrow I) transports the bills in the
input
receptacle, one at a time, passed an authenticating and discriminating unit
1696.
Based on the results of the authenticating and discriminating unit 1684, a
bill is either
transported to a single output receptacle 1698 (arrow J) or to an operator
inspection
station 1699 (arrow K). When is bill is determined to be genuine and its
denomination has been identified, the bill is transported to the single output
receptacle. Alternatively, where the authenticating and discriminating unit
determines
CA 02215853 1997-11-06 ,
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137
that a bill is a fake or for some reason the authenticating and discriminating
unit 16$4
is not able to identify the denomination of the bill, the flagged bill is
routed (arrow
K) to an inspection station and the discriminator system 1692 stops operating.
The
inspection station is preferably positioned within the discriminator system
1692 so
that the operator may conveniently see the flagged bill and/or remove it for
closer
inspection. Where a bill has been positively determined to be a fake by the
authenticating and discriminating unit 1696, an appropriate indication, for
example,
via a message in a display or the illumination of a light, can be given to the
operator
as to the lack of genuineness of the bill. The operator may then remove the
bill
without replacement from the inspection station 1699 and select a continuation
element. Where a bill has not been positively identified as a fake nor has had
its
denomination identified and where the operator determines that the bill is
acceptable,
the operator returns the bill to the inspection station if it was removed and
selects a
selection element (not shown) corresponding to the denomination of the flanged
bill.
Appropriate counters (not shown) are incremented, the discriminator system
1680
resumes operation, and the flagged bill is routed (arrow L) to the single
output
receptacle 1698. On the other hand, if the operator determines that the
flagged bill is
unacceptable, the operator removes the bill without replacement form the
inspection
station and selects a continuation element (not shown). The discriminator
system
1692 resumes operation without incrementing the counters associated with the
various
denomination and/or the total value counters. While transport paths J and L
are
illustrated as separate paths, they may be the same path so that all bills
proceeding to
the single output receptacle 1698 are routed through the inspection station
1699.
The operation of the selection elements will now be described in more detail
2~ in conjunction with FIG. 59 which is a front view of a control panel 61 of
a
preferred embodiment of the present invention. The control panel 61 comprises
a
keypad 62 and a display section 63. The keypad 62 comprises a plurality of
keys
including seven denomination selection elements 64a-64g, each associated with
one of
seven U.S. currency denominations, i.e., $1, $2, $5, $10, $20, $50, and $100.
The
$1 denomination selection key 64a also serves as a mode selection key. The
keypad
62 also comprises a "Continuation" selection element 65. Various information
such
as instructions, mode selection information, authentication and discrimination
CA 02215853 1997-11-06
138
information, individual denomination counter values, and total batch counter
value
are communicated to the operator via an LCD 66 in the display section 63. A
discriminator according to a preferred embodiment of the present invention has
a
number of operating modes including a mixed mode, a stranger mode, a sort
mode, a
face mode, and a folward/reverse orientation mode. The operation of a
discriminator
having the denomination selection elements 64a-64g and the continuation
element 65
will now be discussed in connection with several operating modes.
~A) Mixed Mode
Mixed mode is designed to accept a stack of bills of mixed denomination,
total the aggregate value of all the bills in the stack and display the
aggregate value in
the display 63. Information regarding the number of bills of each individual
denomination in a stack may also be stored in denomination counters. When an
otherwise acceptable bill remains unidentified after passing through the
authenticating
and discriminating unit, operation of the discriminator may be resumed and the
corresponding denomination counter and/or the aggregate value counter may be
appropriately incremented by selecting the denomination selection key 64a-64g
associated with the denomination of the unidentified bill. For example, if the
discriminator system 62 of FIG. 56 or 10 of FIG. 1 stops operation with an
otherwise
acceptable $5 bill being the last bill deposited in the output receptacle, the
operator
may simply select key 64b. When key 64b is depressed, the operation of the
discriminator is resumed and the $5 denomination counter is incremented and/or
the
aggregate value counter is incremented by $5. .Furthermore, in the
discriminator
systems 1680 of FIG. 57 and 1692 of FIG. 58, the flagged bill may be routed
from
the inspection station to an appropriate output receptacle. Otherwise, if the
operator
determines the flagged bill is unacceptable, the bill may be removed from the
output
receptacle of FIGs. 1 or 56 or the inspection station of FIGS. 8 and 9 (or in
the
system 1680 of FIG. 57, the flagged bill may be routed to the reject
receptacle
1688). The continuation key 65 is depressed after the unacceptable bill is
removed,
and the discriminator resumes operation without affecting the total value
counter
and/or the individual denomination counters.
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139
(B) Stranger Mode
Stranger mode is designed to accommodate a stack of bills all having the same
denomination, such as a stack of $10 bills. In such a mode, when a stack of
bills is
processed by the discriminator the denomination of the first bill in the stack
is
determined and subsequent bills are flagged if they are not of the same
denomination.
Alternatively, the discriminator may be designed to permit the operator to
designate
the denomination against which bills will be evaluated with those of a
different
denomination being flagged. Assuming the first bill in a stack determines the
relevant denomination and assuming the first bill is a $10 bill, then provided
all the
bills in the stack are $10 bills, the display 63 will indicate the aggregate
value of the
bills in the stack and/or the number of $10 bills in the stack. However, if a
bill
having a denomination other than $10 is included in the stack, the
discriminator will
stop operating with the non-$10 bill or "stranger bill" being the last bill
deposited in
the output receptacle in the case of the discriminator system 62 of FIG. 56 or
10 of
1~ FIG. 1 (or the inspection station of FIGS. 8 and 9). The stranger bill may
then be
removed from the output receptacle and the discriminator is started again
either
automatically or by depression of the "Continuation" key 6~ depending on the
set up
of the discriminator system. An unidentified but otherwise acceptable $10 bill
may
be handled in a manner similar to that described above in connection with the
mixed
mode, e.g., by depressing the $10 denomination selection element 64c, or
alternatively, the unidentified but otherwise acceptable $10 bill may be
removed from
the output receptacle and placed into the input hopper to be re-scanned. Upon
the
completion of processing the entire stack, the display 63 will indicate the
aggregate
value of the $10 bills in the stack and/or the number of $10 bills in the
stack. All
2~ bills having a denomination other than $10 will have been set aside and
will not be
included in the totals. Alternatively, these stranger bills can be included in
the totals
via operator selection choices. For example, if a $~ stranger bill is detected
and
flagged in a stack of $10 bills, the operator may be prompted via the display
as to
whether the $~ bill should be incorporated into the running totals. If the
operator
responds positively, the $5 bill is incorporated into appropriate running
totals,
otherwise it is not. Alternatively, a set-up selection may be chosen whereby
all
stranger bills are automatically incorporated into appropriate running totals.
CA 02215853 1997-11-06
140
(C) Sort Mode
Sort mode is designed to accommodate a stack of bills wherein the bills are
separated by denomination. For example, all the $1 bills may be placed at the
beginning of the stack, followed by all the $5 bills, followed by all the $10
bills, etc.
The operation of the sort mode is similar to that of the stranger mode except
that
after stopping upon the detection of a different denomination bill, the
discriminator is
designed to resume operation upon removal of all bills from the output
receptacle.
Returning to the above example, assuming the first bill in a stack determines
the
relevant denomination and assuming the first bill is a $1 bill, then the
discriminator
processes the bills in the stack until the first non-$1 bill is detected,
which in this
example is the first $5 bill. At that point, the discriminator will stop
operating with
the fast $5 being the last bill deposited in the output receptacle. The
display 63 may
be designed to indicate the aggregate value of the preceding $1 bills
processed and/or
the number of preceding $1 bills. The scanned $1 bills and the first $5 bill
are
removed from the output receptacle and placed in separate $1 and $5 bill
stacks. The
discriminator will start again automatically and subsequent bills will be
assessed
relative to being $5 bills. The discriminator continues processing bills until
the first
$10 bill is encountered. The above procedure is repeated and the discriminator
resumes operation until encountering the first bill which is not a $10 bill,
and so on.
Upon the completion of processing the entire stack, the display 63 will
indicate the
aggregate value of all the bills in the stack andJor the number of bills of
each
denomination in the stack. This mode permits the operator to separate a stack
of bills
having multiple denominations into separate stacks according to denomination.
(D) Face Mode
Face mode is designed to accommodate a stack of bills all faced in the same
direction, e.g., all placed in the input hopper face up (that is the portrait
or black
side up for U.S. bills) and to detect any bills facing the opposite direction.
In such a
mode, when a stack of bills is processed by the discriminator, the face
orientation of
the first bill in the stack is determined and subsequent bills are flagged if
they do not
have the same face orientation. Alternatively, the discriminator may be
designed to
permit designation of the face orientation to which bills will be evaluated
with those
CA 02215853 1997-11-06
141
having a different face orientation being flagged. Assuming the first bill in
a stack
determines the relevant face orientation and assuming the first bill is face
up, then
provided all the bills in the stack are face up, the display 63 will indicate
the
aggregate value of the bills in the stack and/or the number of bills of each
denomination in the stack. However, if a bill faced in the opposite direction
(i.e.,
face down in this example) is included in the stack, the discriminator will
stop
operating with the reverse-faced bill being the last bill deposited in the
output
receptacle. The reverse-faced bill then may be removed from the output
receptacle.
In automatic re-start embodiments, the removal of the reverse-faced bill
causes the
discriminator to continue operating. The removed bill may then be placed into
the
input receptacle with the proper face orientation. Alternatively, in non-
automatic re-
start embodiments, the reverse-faced bill may be either placed into the input
receptacle with the proper face orientation and the continuation key 65
depressed, or
placed back into the output receptacle with the proper face orientation.
Depending on
l~ the set up of the discriminator when a bill is placed back into the output
receptacle
with the proper face orientation, the denomination selection key associated
with the
reverse-faced bill may be selected, whereby the associated denomination
counter
and/or aggregate value counter are appropriately incremented and the
discriminator
resumes operation. Alternatively, in embodiments wherein the discriminator is
capable of determining denomination regardless of face orientation, the
continuation
key 6~ or a third key may be depressed whereby the discriminator resumes
operation
and the appropriate denomination counter and/or total value counter is
incremented in
accordance with the denomination identified by the discriminating unit. In
discriminators that require a specific face orientation, any reverse-faced
bills will be
unidentified bills. In discriminators that can accept a bill regardless of
face
orientation, reverse-faced bills may be properly identified. The later type of
discriminator may have a discriminating unit with a scanhead on each side of
the
transport path. Examples of such dual-sided discriminators are disclosed above
(see
e.g., FIGs. 2a, 6c, ZOa, 26, and 42. The ability to detect and correct for
reverse-
faced bills is important as the Federal Reserve requires currency it receives
to be
faced in the same direction.
CA 02215853 1997-11-06
142
In a mufti-output receptacle discriminator, the face mode may be used to route
all bills facing upward to one output receptacle and all bills facing downward
to
another output receptacle. In single-sided discriminators, reverse-faced bills
may be
routed to an inspection station such as 1690 of FIG. 57 far manual turnover by
the
operator and the unidentified reverse-faced bills may then be passed by the
discriminator again. In dual-sided discriminators, identified reverse-faced
bills may
be routed directly to an appropriate output receptacle. For example, in dual-
sided
discriminators bills may be sorted both by face orientation and by
denomination, e.g.,
face up $1 bills into pocket #l, face down $1 bills into pocket #2, face up $S
bills
into pocket #3, and so on or simply by denomination, regardless of face
orientation,
e.g., all $i bills into pocket #1 regardless of face orientation, all $2 bills
into pocket
#2, etc.
(E) Forward/Reverse Orientation Mode
Forward/Reverse Orientation mode ("Orientation" mode) is designed to
1~ accommodate a stack of bills all oriented in a predetermined forward or
reverse
orientation direction. For example in a discriminator that feeds bills along
their
narrow dimension, the forward direction may be defined as the fed direction
whereby
the top edge of a bill is fed first and conversely for the reverse direction.
In a
discriminator that feeds bills along their long dimension, the forward
direction may
be defined as the fed direction whereby the left edge of a bill is fed first
and
conversely for the reverse direction. In such a mode, when a stack of bills is
processed by the discriminator, the fonvard/reverse orientation of the first
bill in the
stack is determined and subsequent bills are flagged if they do not have the
same
forwardlreverse orientation. Alternatively, the discriminator may be designed
to
permit the operator to designate the forward/reverse orientation against which
bills
will be evaluated with those having a different forward/reverse orientation
being
flagged. Assuming the first bill in a stack determines the relevant
forward/reverse
orientation and assuming the first bill is fed in the forward direction, then
provided
all the bills in the stack are also fed in the forward direction, the display
63 will
indicate the aggregate value of the bills in the stack andlor the number of
bills of
each denomination in the stack. However, if a bill having the opposite
CA 02215853 1997-11-06
143
forward/reverse orientation is included in the stack, the discriminator will
stop
operating with the opposite forward/reverse oriented bill being the last bill
deposited
in the output receptacle. The opposite forward/reverse oriented bill then may
be
removed from the output receptacle. In automatic re-start embodiments, the
removal
of the opposite forward/reverse oriented bill causes the discriminator to
continue
operating. The removed bill may then be placed into the input receptacle with
the
proper face orientation. Alternatively, in non-automatic re-start embodiments,
the
opposite forward/reverse oriented bill may be either placed into the input
receptacle
with the proper forward/reverse orientation and the continuation key 65
depressed, or
placed back into the output receptacle with the proper forward/reverse
orientation.
Depending on the set up of the discriminator when a bill is placed back into
the
output receptacle with the proper forward/reverse orientation, the
denomination
selection key associated with the opposite forward/reverse oriented bill may
be
selected, whereby the associated denomination counter and/or aggregate value
counter
are appropriately incremented and the discriminator resumes operation.
Alternatively, in embodiments wherein the discriminator is capable of
determining
denomination regardless of forward/reverse orientation, the continuation key
65 or a
the third key may be depressed whereby the discriminator resumes operation and
the
appropriate denomination counter and/or total value counter is incremented in
accordance with the denomination identified by the discriminating unit. In
single-
direction discriminators, any reverse-oriented bills will be unidentified
bills. In dual-
direction discriminators, reverse-oriented bills may be properly identified by
the
discriminating unit. An example of a dual-direction discriminating system is
described above connection with FIGS. 1-7b and in United States Pat. No.
5,295,196.
The ability to detect and correct for reverse-oriented bills is important as
the Federal
Reserve may soon require currency it receives to be oriented in the same
forward/reverse direction.
In a mufti-output receptacle discriminator, the orientation mode may be used
to route all bills oriented in the forward direction to one output receptacle
and all
bills oriented in the reverse direction to another output receptacle. In
single-direction
discriminators, reverse-oriented bills may be routed to an inspection station
such as
1690 of FIG. 57 for manual turnover by the operator and the unidentified
reverse-
CA 02215853 1997-11-06
1~
oriented bills may then be passed by the discriminator again. In
discriminators
capable of identifying bills fed in both forward and reverse directions ("dual-
direction
discriminators"), identified reverse-oriented bills may be routed directly to
an
appropriate output receptacle. For example, in dual-direction discriminators
bills
may be sorted both by forward/reverse orientation and by denomination, e.g.,
forward $1 bills into pocket #1, reverse $1 bills into pocket #2, forward $5
bills into
pocket #3, and so on or simply by denomination, regardless of forward/reverse
orientation, e.g., all $1 bills into pocket #1 regardless of forward/reverse
orientation,
all $2 bills into pocket #2, etc.
Suspect Mode
In addition to the above modes, a suspect mode may be activated in
connection with these modes whereby one or more authentication tests may be
performed on the bills in a stack. When a bill fails an authentication test,
the
discriminator will stop with the failing or suspect bill being the last bill
transported to
l~ the output receptacle. The suspect bill then may be removed from the output
receptacle and set aside.
Likewise, one or more of the above described modes may be activated at the
same time. For example, the face mode and the forward/reverse orientation mode
may be activated at the same time. In such a case, bills that are either
reverse-faced
or opposite forward/reverse oriented will be flagged.
According to a preferred embodiment, when a bill is flagged, for example, by
stopping the transport motor with the flagged bill being the last bill
deposited in the
output receptacle, the discriminating device indicates to the operator when
the bill
was flagged. This indication may be accomplished by, for example, lighting an
appropriate light, generating an appropriate sound, and/or displaying an
appropriate
message in the display section 63 (FIG. 59). Such indication might include,
for
example, "no call", "stranger", "failed magnetic test", "failed UV test", "no
security
thread", etc.
Referring now to FIGS. 60a-60c, there is shown a side view of a preferred
embodiment of a document authenticating system according to the present
invention,
a top view of the preferred embodiment of FIG. 60a along the direction 60b,
and a
CA 02215853 1997-11-06
145
top view of the preferred embodiment of FiG. 60a along the direction 60c,
respectively. An ultraviolet ("UV") light source 2102 illuminates a document
2104.
Depending upon the characteristics of the document, ultraviolet light may be
reflected
off the document and/or fluorescent light may be emitted from the document. A
detection system 2106 is positioned so as to receive any light reflected or
emitted
toward it but not to receive any UV light directly from the light source 2102.
The
detection system 2106 comprises a UV sensor 2108, a fluorescence sensor 2110,
filters, and a plastic housing. The light source 2102 and the detection system
2106
are both mounted to a printed circuit board 2112. The document 2104 is
transported
in the direction indicated by arrow A by a transport system (not shown). The
document is transported over a transpor t plate 2114 which has a rectangular
opening
2116 in it to permit passage of light to and from the document. In a preferred
embodiment of the present invention, the rectangular opening 2116 is 1.375
inches
(3.493 cm) by 0.375 inches (0.953 cm). To minimize dust accumulation onto the
1~ light source 2102 and the detection system 2106 and to prevent document
jams, the
opening 2116 is covered with a transparent UV transmitting acrylic window
2118.
To further reduce dust accumulation, the UV light source 2102 and the
detection
system 2106 are completely enclosed within a housing (not shown) comprising
the
transport plate 2114.
Referring now to FiG. 61, there is shown a functional block diagram
illustrating a preferred embodiment of a document authenticating system
according to
the present invention. FIG. 61 shows an UV sensor 2202, a fluorescence sensor
2204, and filters 2206, 2208 of a detection system such as the detection
system 2106
of FIG. 60. Light from the document passes through the filters 2206, 2208
before
striking the sensors 2202, 2204, respectively. An ultraviolet filter 2206
filters out
visible light and permits UV light to be transmitted and hence to strike UV
sensor
2202. Similarly, a visible light filter 2208 filters out UV light and permits
visible
light to be transmitted and hence to strike fluorescence sensor 2204.
Accordingly,
UV light, which has a wavelength below 400 nm, is prevented from striking the
fluorescence sensor 2204 and visible light, which has a wavelength greater
than 400
nm, is prevented from striking the UV sensor 2202. In a preferred embodiment
the
UV filter 2206 transmits light having a wavelength between about 260 nm and
about
CA 02215853 1997-11-06
i46
380 nm and has a peak transmittance at 360 nm. In a preferred embodiment, the
visible light filter 2208 is a blue filter and preferably transmits light
having a
wavelength between about 415 nm and about 620 nm and has a peak transmittance
at
450 nm. The above preferred blue filter comprises a combination of a blue
component filter and a yellow component filter. The blue component filter
transmits
light having a wavelength between about 320 nm and about 620 nm and has a peak
transmittance at 450 nm. The yellow component filter transmits light having a
wavelength between about 4I5 nm and about 2800 nm. Examples of suitable
filters
are UGl (UV filter), BG23 (blue bandpass filter), and GG420 (yellow longpass
filter), all manufactured by Schott. In a preferred embodiment the filters are
about 8
mm in diameter and about 1.5 mm thick.
The UV sensor 2202 outputs an analog signal proportional to the amount of
light incident thereon and this signal is amplified by amplifier 2210 and fed
to a
microcontroller 2212. Similarly, the fluorescence sensor 2204 outputs an
analog
signal proportional to the amount of light incident thereon and this signal is
amplified
by amplifier 2214 and fed to a microcontrolier 2212. Analog-to-digital
converters
2216 within the microcontroller 2212 convert the signals from the amplifiers
2210,
2214 to digital and these digital signals are processed by the software of the
microcontroller 2212. The UV sensor 2202 may be, for example, an ultraviolet
enhanced photodiode sensitive to light having a wavelength of about 360 nm and
the
fluorescence sensor 2204 may be a blue enhanced photodiode sensitive to light
having
a wavelength of about 450 nm. Such photodiodes are available from, for
example,
Advanced Photonix, Inc., Massachusetts. The microcontroller 2212 may be, for
example, a Motorola 68HC16.
The exact characteristics of the sensors 2202, 2204 and the filters 2206, 2208
including the wavelength transmittance ranges of the above filters are not as
critical
to the present invention as the prevention of the fluorescence sensor from
generating
an output signal in response to ultraviolet light and the ultraviolet sensor
from
generating an output signal in response to visible light. For example, instead
of, or
in addition to, filters, a authentication system according to the present
invention may
employ an ultraviolet sensor which is not responsive to light having a
wavelength
CA 02215853 1997-11-06
147
longer than 400 nm and/or a fluorescence sensor which is not responsive to
light
having a wavelength shorter than 400 nm.
Calibration potentiometers 2218, 2220 permit the gains of amplifiers 2210,
2214 to be adjusted to appropriate levels. Calibration may be performed by
positioning a piece of white fluorescent paper on the transport plate 2114 so
that it
completely covers the rectangular opening 2116 of FIG. 60. The potentiometers
2218, 2220 may then be adjusted so that the output of the amplifiers 2210,
2214 is 5
volts.
The implementation of the preferred embodiment of a document authenticating
system according to the present invention as illustrated in FIG. 61 with
respect to the
authentication of U.S. currency will now be described. As discussed above, it
has
been determined that genuine United States currency reflects a high level of
ultraviolet light and does not fluoresce under ultraviolet illumination. It
has also been
determined that under ultraviolet illumination counterfeit United States
currency
exhibits one of the four sets of characteristics listed below:
1) Reflects a low level of ultraviolet light and fluoresces;
2) Reflects a low level of ultraviolet light and does not fluoresce;
3) Reflects a high level of ultraviolet light and fluoresces;
4) Reflects a high level of ultraviolet light and does not fluoresce.
Counterfeit bills in categories (1) and (2) may be detected by a currency
authenticator
employing an ultraviolet light reflection test according to a preferred
embodiment of
the present invention. Counterfeit bills in category (3) may be detected by a
currency
authenticator employing both an ultraviolet reflection test and a fluorescence
test
according to another preferred embodiment of the present invention. Only
counterfeits in category (4) are not detected by the authenticating methods of
the
present invention.
According to a preferred embodiment of the present invention, fluorescence is
determined by any signal that is above the noise floor. Thus, the amplified
fluorescent sensor signal 2222 will be approximately 0 volts for genuine U.S.
currency and will vary between approximately 0 and S volts for counterfeit
bills
depending upon their fluorescent characteristics. Accordingly, an
authenticating
CA 02215853 1997-11-06
148
system according to a preferred embodiment of the present invention will
reject bills
when signal 2222 exceeds approximately 0 volts.
According to a preferred embodiment of the present invention, a high level of
reflected UV light ("high UV") is indicated when the amplified UV sensor
signal
S 2224 is above a predetermined threshold. The high/low UV threshold is a
function
of lamp intensity and reflectance. Lamp intensity can degrade by as much as
50%
over the life of the lamp and can be further attenuated by dust accumulation
on the
lamp and the sensors. The problem of dust accumulation is mitigated by
enclosing
the lamp and sensors in a housing as discussed above. An authenticating system
according to a preferred embodiment of the present invention tracks the
intensity of
the L'V light source and readjusts the high/low threshold accordingly. The
degradation of the UV light source may be compensated for by periodically
feeding a
genuine bill into the system, sampling the output of the UV sensor, and
adjusting the
threshold accordingly. Alternatively, degradation may be compensated for by
IS periodically sampling the output of the UV sensor when no bill is present
in the
rectangular opening 2 i 16 of the transport plate 2114. It is noted that a
certain
amount of UV li4ht is always reflected off the acrylic window 2118. By
periodically
sampling the output of the UV sensor when no bill is present, the system can
compensate for light source degradation. Furthermore, such sampling could also
be
used to indicate to the operator of the system when the ultraviolet light
source has
burned out or otherwise requires replacement. This may be accomplished, for
example, by means of a display reading or an illuminated light emitting diode
("LED"). The amplified ultraviolet sensor signal 2224 will initially vary
between 1.0
and 5.0 volts depending upon the UV reflectance characteristics of the
document
being scanned and will slowly drift downward as the light source degrades. In
an
alternative preferred embodiment to a preferred embodiment wherein the
threshold
level is adjusted as the light source degrades, the sampling of the UV sensor
output
may be used to adjust the gain of the amplifier 2210 thereby maintaining the
output'
of the amplifier 2210 at its initial levels.
It has been found that the voltage ratio between counterfeit and genuine U.S.
bills varies from a discernable 2-to-1 ratio to a non-discernable ratio.
According to a
preferred embodiment of the present invention a 2-to-1 ratio is used to
discriminate
CA 02215853 1999-OS-04
149
between genuine and counterfeit bills. For example, if a genuine U.S. bill
generates
an amplified UV output sensor signal 2224 of 4.0 volts, documents generating
an
amplified UV output sensor signal 2224 of 2.0 volts or less will be rejected
as
counterfeit. As described above, this threshold of 2.0 volts may either be
lowered as
S the light source, degrades or the gain of the amplifier 2210 may be adjusted
so that
2.0 volts remains an appropriate threshold value.
According to a preferred embodiment of the present invention, the
determination of whether the level of UV reflected off a document is high or
low is
made by sampling the output of the UV sensor at a number of intervals,
averaging
the readings, and comparing the average level with the predetermined high/low
threshold. Alternatively, a comparison may be made by measuring the amount of
UV light reflected at a number of locations on the bill and comparing these
measurements with those obtained from genuine bills. Alternatively, the output
of
one or more UV sensors may be processed to generate one or more patterns of
reflected UV light and these patterns may be compared to the patterns
generated by
genuine bills. Such a pattern generation and comparison technique may be
performed
by modifying an optical pattern technique such as that disclosed in United
States Pat.
No. 5,295,196 or in the United States Patent No. 5,652,802 issued July 29,
1997 for a
"Method and Apparatus for Document Identif cation."
In a similar manner, the presence of fluorescence may ber.performed by
sampling the output of the fluorescence sensor at a number of intervals.
However, in
a preferred embodiment, a bill is rejected as counterfeit U.S. currency if any
of the
sampled outputs rise above the noise floor. However, the alternative methods
discussed above with respect to processing the signal or signals of a UV
sensor or
sensors may also be employed, especially with respect to currencies of other
countries or other types of documents which may employ as security features
certain
locations or patterns of fluorescent materials.
A currency authenticating system according to the present invention may be
provided with means, such as a display, to indicate to the operator the
reasons why a
document has been rejected, e.g., messages such as "UV FAILURE" or
CA 02215853 1997-11-06
1$~
"FLUORESCENCE FAILURE." A currency authenticating system according to the
present invention may also permit the operator to selectively choose to
activate or
deactivate either the UV reflection test or the fluorescence test or both. A
currency
authenticating system according to the present invention may also be provided
with
$ means for adjusting the sensitivities of the UV reflection and/or
fluorescence test, for
example, by adjusting the respective thresholds. For example, in the case of
U.S.
currency, a system according to the present invention may permit the high/low
threshold to be adjusted, for example, either in absolute voltage terms or in
genuine/suspect ratio terms.
