Note: Descriptions are shown in the official language in which they were submitted.
2117435
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METHOD AND APPARATUS FOR SCANNING BANK NOTES
Background of the Invention
The present invention relates to a method and apparatus for scanning bank
notes, and
in particular to a method and apparatus which utilizes light transmission
optical bank note
scanning.
The invention has application, for example, to an optical scanner for use in
an
automated currency loading module used to load currency storage cassettes, in
which bank
notes are stored in an automated teller machine (ATM) prior to being dispensed
to customers,
l~( or in a currency condition screening module in a financial transaction
terminal, such as an
ATM.
Bank notes intended for use in an ATM may require to be scanned to determine
their
condition. A damaged bank note may not be suitable for use in an ATM as tears
or holes in
the note may cause the note to become jammed in the transport means utilized
to transport
notes within the ATM. Therefore, damaged bank notes need to be screened out by
automated
currency loading modules before currency storage cassettes are filled and
loaded into an
ATM. Also, ATMs which are adapted to enable users to deposit individual bank
notes, and
to re-issue these notes to other users of the ATM, must also be adapted to
screen out damaged
notes so that an attempt is not made to dispense these notes to other users.
20 The detection of notes containing pinholes or other holes is particularly
important if
the notes are intended for use in an ATM which utilizes suction pick means to
pick notes
from a currency storage cassette. If a pinhole in such a bank note is located
in an area of the
note at which the pick means contacts the note, then the pinhole may result in
the pick means
mispicking. For example, if a note to be picked from a currency storage
cassette contains a
2_~ pinhole, the pick means may fail to pick that note or may pick both the
note intended to be
picked and the adjacent note. If a double feed is detected, by sensors within
the ATM, the
picked notes are diverted to a purge bin, and it is necessary to pick an
additional note to
ensure that the correct number of notes is always dispensed to the user of the
ATM.
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2
A known bank note scanner, disclosed in US Patent
4,984,280, utilizes transport means for transporting bank
notes along a transport path throughout the scanner. A light
source is located on one side of the transport path to
illuminate the bank notes and a photo-electric means is
located on the opposite side of the transport path from said
light source to produce a representation of the scanned bank
note. The photo-electric means produces a predominately black
representation of the bank note, with light patches, corres-
ponding to any damaged areas of the note, caused by the
transmission of light through the damaged areas of the note.
Some damage to bank notes may be tolerated, such as
pinholes in non-sensitive area remote from those sections of
t:?e note which are contacted by suction pick means when the
note is picked from the currency storage cassette of an ATM.
However, the above-mentioned known bank note scanner cannot
distinguish between damage to a bank note which can be
tolerated and damage that cannot be tolerated.
Summarv of the Invention
It is an object of the present invention to provide
an optical bank note scanner and method of scanning bank notes
which allows notes containing an insignificant defect, which
does not affect the mechanized transportation of the note or
the suction picking of the note, to be accepted for use while
ensuring that a note having a significant defect is rejected.
According to a first aspect of the present invention
there is provide a method of optically scanning a bank note
~'~
,,:g
62118-1977
2177435
3
having edges which form boundaries thereof, the method
comprising the steps of: (a) moving the bank note along a
transport path; (b) illuminating the bank note from one side
of the transport path; (c) obtaining a representation of the
boundaries of the bank note based upon illumination of the
bank note in step (b); (d) determining the location of any
predetermined type of defect in the bank note relat ive to the
boundaries of the bank note by using the representation of the
boundaries of the bank note obtained in step (c); and (e)
determining whether or not the bank note is acceptable for use
in an automated teller machine (ATM) depending upon the
location of any defect or defects which have been located in
the bank note as determined in step (d).
According to a second aspect of the present
invention there is provided a method of determining the
fitness of a bank note for a predetermined use in which the
note is scanned to form a digital representation thereof,
characterized by the steps of processing said digital
representation to determine the location and size of any
predetermined type of defect in said note, and determining
said fitness of said note on the basis of the location and
size of any such defect or defects which have been detected.
According to a third aspect of the present invention
there is provided a optical bank note scanner comprising: a
transport mechanism for transporting a bank note having edges
which form boundaries thereof, along a transport path; a light
source located on one side of the transport path for
62118-1977
2117435
3a
illuminating the bank note; a sensor device located on the
opposite side of the transport path from the light source for
producing a representation of the bank note; and a controller
unit responsive to the sensor device and for (i) determining
the location of any predetermined type of detected defects in
the bank note relative to the boundaries of the bank note, and
(1i) determining whether or not the bank note is acceptable
for use in an automated teller machine (ATM) depending upon
the location of any such defect or defects which have been
det ect ed .
Brief Description of the Drawings
An embodiment of the present invention will now be
described, by way of example, with reference to the
accompanying drawings in which:
Fig lA is a schematic plan view of a portion of an
optical bank note scanner in accordance with the present
invention;
Fig. 1B is a schematic side view of the portion of
the scanner of Fig. lA;
Fig. 2 is a block diagram of an optical bank note
scanner in accordance with the present invention;
Fig. 3 is a schematic representation of a bank note
and an array of charge coupled device (CCD) elements
incorporated in a photo-electric means in accordance with the
present invention;
62118-1977
2117435
4
Fig. 4A is a graphical representation of the output signals from the charge
coupled
device (CCD) elements of Fig. 3;
Fig. 4B is a graphic representation of a scan line through a bank note, for
which the
array of Fig. 3 produces the output represented in Fig. 4A;
Figs SA to SD are graphic representations of a method of determining the
boundaries
of a bank note with an edge defect, in accordance with the present invention;
and
Fig. 6 is a flow diagram of a method of determining the acceptability of a
scanned
bank note in accordance with the present invention.
1_Q Detailed Descri tn ion
Referring particularly to Figs 1 A and 1 B there is illustrated a portion of
an optical
bank note scanner 2, suitable for use in an automated currency loading module
(not shown).
The scanner 2 incorporates transport means in the form of a plurality of belt
means 4 to 11,
and associated pulleys 14 to 21, some of which are driven through gear means
(not shown)
by a motor 22 (Fig. 2) so as to drive the belt means 4 to 11.
The belt means 4 to 7 form a first feed path 26, located adjacent a gate 24.
When the
gate 24 is in a first position 241, the gate 24 directs acceptable bank notes
from the first feed
path 26 to a continuation feed path 27 formed by belt means 8 and 9, for
storage in a currency
storage cassette (not shown). When the gate 24 is in a second position 242,
the gate 24
20 directs rejected bank notes along a second feed path 28 formed by belt
means 10 and 11, to a
purge bin (not shown). The position of the gate 24 is controlled by a control
means 30 (Fig.
2), as will be discussed below.
The scanner 2 also incorporates a light source 32 in the form of a fluorescent
tube
light. The light source 32 is located beneath the first feed path 26, between
the belt means 4
2~ and S. A photo-electric means 34, in the form of a high resolution charge
coupled device
(CCD) line scan camera such as the Fairchild CCD 1100 line scan camera,
produced by
Fairchild Camera & Instrument (UK) Ltd. 230 High Street, Potters Bar,
Hertfordshire,
2177435
England, is located above the light source 32 on the opposite side of the feed
path 26,
between the belt means 6 and 7.
Thus a note 38 which is transported along the first feed path 26 by the belt
means 4
and 6 and the adjacent belt means 5 and 7 will pass between the light source
32 and the
photo-electric means 34. The space between the belt means 4 and 6 and the
adjacent belt
means 5 and 7, in which the light source 32 and photo-electric means 34 are
located, is
arranged so that the belt means 5 and 7 receive the note 38, for continued
transportation, prior
to the belt means 4 and 6 releasing the note 38.
Referring to Fig. 2 the operation of the scanner 2 is controlled by a control
means 30
in the form of a central processor unit. The control means 30 causes the light
source 32, the
photo-electric means 34 and the motor 22 to be switched on once the control
means 30 has
been so instructed by a user of the scanner 2 through a user interface 42.
The scanner 2 is now ready to scan bank notes 38 (Fig. 1) which are fed along
the
first feed path 26, as discussed above.
Bank notes 38 which are to be fed along the feed path 26 are detected by a
note
present detector 13 located at the input end of the feed path 26. The note
present detector 13
informs the control means 30 of the presence of a bank note 38 and the control
means 30 can
then actuate the photo-electric means 34 at the appropriate time to scan the
bank note 38.
Before discussing the data produced by the photo-electric means 34 and how it
is used
in a processor 40 (Fig. 2) to determine the acceptability of a bank note 38,
it is appropriate to
discuss how CCD devices produce a representation, in general.
With reference to Fig. 3 a CCD device, such as the device mentioned above,
contains
a CCD chip 60. As will be known to a person skilled in the art, such CCD
devices operate by
focusing incident light onto an array of CCD elements 62 on the CCD chip 60,
utilizing an
appropriate optical system 68, thereby building up a charge on individual
elements 62
dependent on the quantity of light incident on each element 62. Data is
produced by
sampling the charge on each of the elements 62, by transferring said charge to
an associated
charge measurement device (not shown), at a predetermined time. This sampling
is
2111435
6
analogous to the opening and closing of the shutter in a conventional camera.
Clearly, a low
charge corresponds to a dark area in the representation and a high charge to a
light area. The
charge on each element 62 can then be compared to a predetermined threshold
level 71, to
provide digital data, i.e. a "0" representing charge on a CCD element below a
predetermined
threshold level 71 (Fig. 4A) corresponding to an undamaged area of the bank
note 38 being
scanned, and a "1" representing charge above the predetermined threshold level
71 and
corresponding to light coming from beyond an edge of the note 38, or from a
damaged area
of the note 38.
In a line scan camera the object to be scanned is drawn along below the camera
at a
predetermined speed and each CCD element 62 is sampled a predetermined number
of times.
Each time the CCD element 62 is sampled it produces a signal representative of
a pixel, that
is a component part of the final representation of the bank note 38. Each time
all of the CCD
elements 62 in the array are sampled, a representation of a line, say line 65
(Fig. 4B), on the
bank note 38 is produced, which is converted from an analog output (Fig. 4A)
into a series of
0's and 1's, dependent on whether or not the charge on individual elements
exceeds the
aforementioned threshold, as discussed above.
Regarding Fig. 4A the extreme left and right edges 61,61' of the line scan
image are
not related to the note 38 being scanned, these edges 61,61' being produced by
spurious
signals from the CCD elements nearest the ends of the array, due to loss of
light caused by
edge effects in the lens system 68 used to focus the light onto the array. The
inner right and
left edges 63,64 correspond to the edges of the bank note 38 for that
particular scan line 65.
Also the peak 66 in the output is caused by a pinhole 67 in the bank note 38
being scanned.
The CCD device mentioned above has 1024 CCD elements 62 arranged in a line
perpendicular to the direction of movement 37 of the note 38 to be scanned
(Fig. 3). In the
25 present embodiment 200 lines are required to provide a representation of
each of the bank
notes comprising the standard currencies with which the scanner 2 is intended
for use. The
size of the smallest defect which can be detected by the scanner 2 is related
to the number of
CCD elements 62 in the array. A 1024 element array can detect a defect as
small as lmm2~
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7
If larger sized defects are acceptable the 1024 element array can be replaced
by an array with
fewer CCD elements, thus reducing the cost of the scanner 2.
The data produced by a CCD camera is conceptually similar to the raster scan
data
used in TV systems, with the exception that TV systems produce both the line
and frame
scans electronically, whereas in the case of a CCD camera the line scan is
electronic and the
frame scan is created by the linear motion of the bank note 38 passing under
the camera due,
in the present embodiment, to the movement of the belt means 4 to 7. Thus a
CCD line scan
camera requires that the bank note 38 is moving whilst the representation is
being produced,
which is ideal for a scanner 2 in accordance with the present invention.
As the representation of the note is produced while the note is moving a
scanner in
accordance with the present invention can scan between 10 and 20 notes per
second.
If the 1024 CCD elements 62 are considered as an X axis and the 200 scan lines
produced during the scanning of a bank note 38 are considered as a Y axis
(Fig. 3), the data
from each specific sample of each individual CCD element can be given an X and
a Y co-
ordinate, i.e. the 10th sample from the SOOth CCD element would have co-
ordinates (500,10).
The processor 40 is arranged to note the co-ordinates of each sample having a
"0"
value, adjacent a sample having a "1" value, as these signals correspond to
either an edge of
the note 38 or an edge of a damaged area of the note 38. These co-ordinates
are then
processed in the processor 40 to determine the co-ordinates with: the lowest X
and Y value;
2_Q the highest X and Y vale; the lowest X and highest Y value; and the
highest X and lowest Y
value, which will correspond to the four corners 78,80,72 and 74 respectively
(Fig. 3) of the
bank note 38 being scanned. The processor 40 then draws lines between adjacent
corners 72-
80,80-74,74-78,78-72, thus producing a two dimensional representation of the
bank note 38,
as illustrated in Fig. 3.
2_~ Furthermore, the device can also detect a skewed note, as the long axis of
the note,
between corners 74 and 78 in Fig. 4, would not lie parallel to the X axis.
Such skewed notes
can then be diverted by the gate 24 (Fig. 1 ) under the control of the control
means 30 (Fig. 2).
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This process for obtaining a representation of the bank note 38 is sufficient
if all four
corners of the bank note are present. However, if one of the corners is
damaged an erroneous
result may be produced, as illustrated by the dashed line 73 between corners
70 and 72 in Fig.
SA. In order to compensate for any such errors the processor 40 scans the data
with co-
5_ ordinates adjacent those of the line 73 between corners 72 and 70, looking
for samples with a
"0" value adjacent samples with a "1" value, as the co-ordinates of these "0"
value samples
will represent the true edge of the bank note 38. The processor 40 then
determines which of
these samples on the true edge of the bank note 38 is furthest from the line
73, along a line
perpendicular to this line 73, as illustrated in Fig. SB. A second
approximation of the outline
of the bank note 38 is then drawn, comprising a line 75 (which lies along the
true edge of the
bank note 38) between corner 72 and the most remote point 76, and a line 77
between the
point 76 and the corner 70. As the line 75 lies along the true edge of the
bank note 38, if the
process is repeated again for line 75 no points are found which are remote
from the line 75.
However, if the process is repeated for the line 77 between point 76 and
corner 70 another
point 79 is determined, which is the most remote point from the line 77, along
a line
perpendicular to the line 77, as illustrated in Fig. SC. A third approximation
to the boundary
of the bank note 38 is then produced by drawing a line between the point 76
and the point 79
and a line between the point 79 and the corner 70. This process can be
repeated as often as
necessary until a representation of the bank note 38 is produces which lies
within
predetermined error margins.
This process is also undertaken for line 81, between corners 70 and 74, line
83,
between corners 74 and 78 and line 85, between corners 78 and 72. However, as
these lines
81,83,85 lie along the actual boundaries of the bank note 38, within
predetermined error
limits, no points remote from these lines 81,83,85 are located.
Once this accurate representation of the bank note 38 is produced an
approximation of
the outline of the bank note 38, in which the damage corner 80 is reinstated,
is produced by
projecting the lines 75 and 81 until they meet at the corner 80 of the
"undamaged" bank note,
as illustrated in Fig. SD.
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9
As the boundaries 75,81,83,85 of the bank note 38 are now known, a weighting
matrix can be overlaid onto the representation of the bank note 38 (Fig. 3),
detailing areas
88,89 with a high weighting factor in which the bank note 38 is sensitive to
damage and areas
90 with a low weighting factor in which the bank note 38 is not sensitive to
damage. For
5_ example, as discussed above, if the bank note 38 is to be used with an ATM
incorporating
suction pick means, areas 88 of the bank note 38 which are contacted by
suction pick means
during picking constitute areas of high weighting factor, whereas areas 90
remote from the
aforementioned areas 88 may constitute areas of a low weighting factor. Also
areas 89
adjacent the left and right boundaries 81,85 of the bank note 38 will
constitute areas of high
weighting factor, because these areas 89 of the bank note 38 are used by the
belt means 4 to
11, and by transport means in an ATM (not shown), to transport the bank note
38. Therefore,
as discussed above, damage to these areas 89 of the bank note 38 may cause the
bank note 38
to become jammed in the belt means 4 to 11 within the scanner 2 or the
transport means in an
ATM.
As discussed above, the location and size of a defect can be obtained in terms
of XY
co-ordinates from the representation of the scanned note in Fig. 3. The
location of the defect
is taken to be the XY co-ordinate approximately at the center of the defect,
such as a pinhole.
The area of the defect can be calculated by counting the number of CCD element
samples
with adjacent XY co-ordinates which have a value "1 ", as these samples each
correspond to a
20 pixel in the representation of the defect in the bank note 38.
Therefore, scanning a bank note 38 provides the processor 40 with a
determination of
both the size of any predetermined type of defects in the bank note 38 and
their location in
relation to the boundaries 75,81,83,85 of the bank note 38 and thus in
relation to the
weighting matrix overlaid onto the representation of the bank note 38, as
illustrated in Fig. 3.
It should be understood that in this embodiment reference to predetermined
type of defect
means any defect, such as a hole, tear or fold at the edge of a bank note,
which gives rise to
detected passage of light.
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to
Once the processor 40 has determined the boundaries 75,81,83,85 of a bank note
38
and the size and location of any defects detected by the scanner 2, the
processor 40
determines whether or not the bank note 38 is acceptable, utilizing the method
illustrated in
Fig. 6.
With regard to Fig. 6 the process starts (box 100) and the processor 40 asks
the
question "is the defect in a high or low weighting factor area" (box 102). The
processor 40
then multiplies the appropriate weighting factor corresponding to the location
of the defect by
the area of the defect (that is the number of samples covered by the defect),
box 104. The
product of this multiplication is called the "reject number". The processor 40
then asks the
question (box 106) " is the product larger than a predetermined maximum". If
the answer to
this question is no, the processor 40 proceeds to box 108 and asks the
question "are there any
un-checked defects" in the bank note 38. If the answer to this question is
again no, then the
processor 40 proceeds to box 110 and the note is accepted, the control means
30 maintains
the gate 24 in the first position 241 and the bank note 38 is transported
along the continuation
feed path 27, as discussed above. The process is then ended, box 112, and the
scanner 2 may
scan the next bank note to be scanned. If the answer to the question asked in
box 108 is yes
and there is one or more un-checked defects in the bank note 38, then the
processor 40 will
move from box 108 back to box 102 and repeat the process for the next defect.
If the answer
to the question asked in box 106 is yes and the reject number is greater than
the
predetermined maximum, for any defect in the bank note 38, then the processor
40 will move
from box 106 to box 116 and the bank note 38 will be rejected. Once the bank
note 38 has
been rejected the processor 40 will move to box 118 and transmit a signal to
this effect to the
control means 30 and the control means 30 will cause the gate 24 to be moved
from its first
position 241 to its second position 242 so as to divert the rejected bank note
38 into the
second feed path 28 for transportation to the purge bin (not shown) as
discussed above.
Thereafter, the processor 40 will move to box 120 and the process will be
stopped. As with
the accepted bank note 38, the scanner 2 may now scan another bank note.
2177435
In order to alter the size of defect which will be considered to be acceptable
in a
particular area 88,89,90 of the bank note 38 the weighting factor in that area
88,89,90 may be
altered. If the weighting factor is increased the size of an acceptable defect
is
correspondingly decreased as the reject number must still fall below the
aforementioned
acceptable value for the note 38 to be accepted.
In the case of a scanner incorporated into the currency condition screening
module in
an ATM, the scanner will be activated on receipt of a signal for the control
means (not
shown) in the ATM, once a user of the ATM has inserted a bank note into a
deposit slot in
the ATM. Also, a scanner incorporated in an ATM will not include a gate to
divert
unacceptable notes to a purge bin; instead, a bi-directional motor will be
incorporated to
drive the belt means 4 to 7, so that unacceptable notes may be returned to the
user of the
ATM, through the deposit slot.
