Note: Descriptions are shown in the official language in which they were submitted.
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FIELD OF THE INVENTIONS
This invention relates to a bank note reader
which can also be used to read printed or written
material.
BACKGROUND OF THE INVENTIONS
Bank note readers and readers of material
carrying expected indicia have in the past used
photosensors to detect the density of the print or
markings at base points on a target object such as a
l0 bank note, and have compared the density with stored
density data for the particular base points. This has
served satisfactorily in the past, but with the
increasing sophistication of counterfeiters, such
readers have been found to be limited in their ability
to correctly identify bank notes.
A typical bank note reader, as described :in
Canadian Patent 1,282,171 issued March 26th, 191 to
E.L. Bryenton & Associates Inc., uses 8 photocells which
are located at specific base point positions over an
illuminated symmetrically coded bank note. The print
density is determined by the photocells, which transmit
their signals to individual comparators. The
comparators compare the signals from the photocells with
reference voltages, and the result is applied to an
arbitrator. Correct comparisons of a valid coding on
both ends of the note detected by the arbitrator result
in ''correct bank note°° indication signals output from
the arbitrator. These signals can be sent to a bank
note aCCept relay, or the like, to facilitate the
provision of change, the vending of a product, etc.
With legal bank notes having increased
resolution of print and with the use of other means 'to
alert vendors to the legality of bank notes, such as by
the use of holographic images on bank notes, the bank
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note reader described above has proven to be limited in
its capability and sometimes rejects legal bank notes.
SUN~IARY OF THE INVENTTON:
The present invention overcomes most or all of
the deficiencies of the bank note reader described in
the above-noted patent. Rather than detecting the
density of only 8 locations on a bank note as in the
above-noted patent, in a preferred embodiment specific
calling of 31,680 pixel sensors within a given area are
to used, and the bank note or part of the bank note is
scanned with these sensors in an imager. The result is
a high resolution electronic scanning of the bank mote.
The resulting signal is digitized and is
compared with pattern information signals stored in a
memory. The detection of a match between the scanned
image and the stored image signals results in the output
of a signal which can cause the announcement of the
value of the bank note, 'the provision of a digital
signal to a change maker, a vending machine acceptor, a
video display, a tactile interface, etc.
With the high resolution of the imager, and
the prestorage of desired images with equivalent
resolution in a memory, a bank note reader of high
accuracy for fine printed bank notes, including those
carrying holographic images can be produced.
Indeed due to the high resolution of the
reader, it can be used to read other printed and
signature material including graphics, alphanumeric and
other coded inscriptions. It can also be used as a
reader fox the blind, reading letters or words and after
finding the letters or words in the memory, generating
an acoustic signal such as letter or word sounds for
reproduction in a loudspeaker. However, for ease of
description, in this disclosure the embodiment described
will be restricted ~to the bank note reader application.
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A parson skilled in the art could easily adapt the
design, using the principles described, to such other
applications as noted above.
According to an embodiment of the invention, a
reader is comprised of apparatus for storing signals in
a memory corresponding to at least a portion of a
pattern of pixels defined by indicia expected to be
carried on the face of a correct carrier object,
apparatus for scanning of a carrier object and providing
to output signals, apparatus for comparing groups of said
output signals wuth the stored signals, and apparatus
for indicating the presence of the correct carrier
object in the event a comparison is correct above a
predetermined level of error.
According to another embodiment a method of
reading bank notes is comprised of storing signals in a
memory corresponding to at least a portion of a pattern
of pixels defined by a printed pattern on the face of
bank note, raster scanning 'the face of the bank note
with a charge coupled device (CCD) to obtain a serial
signal representing each of the pixels, searching the
memory for the serial signal, comparing the serial
signal with the stored signals, and indicating the
correct presence of the bank note in the event the
comparison correlates to a predetermined degree.
BRIEF INTRODUCTION TO THE DRAWINGS:
A better understanding of the invention will
be obtained by reference to the detailed description
below of a preferred embodiment, in conjunction with the
following drawings, in which:
Figure 1 is a cross~section of a physical
layout of a bank note reader in accordance withvthe
present invention,
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Figure 2 is a block diagram of a bank note
reader in accordance with an embodiment of the present
invention,
Figure 3 is a more detailed block diagram of a
bank note reader in accordance with an embodiment of the
present invention, and
Figures 4A and ~B together, with Figure 4A
above Figure 4B, form a flow chart describing how the
microprocessor in an embodiment of the present invention
l0 operates to perform the correlation function described.
DESCRIPTION OF THE PREFERRED EMBODIMENT:
Figure 1 illustrates in vertical section a
preferred physical layout of the present invention. The
face of an object such as a bank note 1 is illuminated
by means of an array of light emitting diodes or other
source of light 2 through the rear of an inclined half
silvered mirror 3. The resulting image reflected from
the front of the mirror is passed 'through an optical
lens 4 which focuses the image of the face of the object
on a charge coupled device (CCD) 5. Alternatively a
different lighting arrangement can be made.
The CCD is connected to an electronic circuit
mounted on a printed circuit board 6 or other suitable
support. The entire apparatus is contained within a
housing within which a speaker 8, if used, is connected
to the electronic circuit.
A block diagram of the circuit is shown in
Figure 2. The CCD is connected in a raster scanning
subsystem 15. The signal output of the CCD in a
subsystem 15 is connected to the input of a digitizer 17
which has its output connected to the bus of a
microprocessor 19. Also connected to 'the microprocessor
is a memory subsystem 21 in one successful prototype
formed of an 8 Kbyte scratch pad memory and a 128 Kbyte
erasable programmable read only memory (EPROM).
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Also connected to the processor by means of a
bus is a user interface 23, which can be comprised of
one or more of a bank note receiver, a voice synthesizer
and speaker, a display etc.
Data signals corresponding ~:o patterns on the
faces of legitimate bank notes or parka of bank notes
are stored in the EPROM of the memory subsystem. When a
bank note is moved into the slot of a bank note receiver
in the user interface, it triggers a microswitch (not
shown) or interrupts a light beam received by a
photocell when it assumes a reading position as shown in
Figure 1. It should be noted that in contrast to the
bank note reader of the prior art, this position need
not be accurate. In the past, inaccurate positioning
would result in reading of points on the bank note which
were incorrect and off the intended base points, which
would result in the rejection of a legal bank note.
This does not occur or at least is minimized in the
present invention.
Operation of the microswitch upon the entry of
a bank note to the reading position causes the
microprocessor to be triggered, starting a reading
cycle. The processor, by a link to the scanning
subsystem, causes the illumination of the object. The
reflected light from the bank note is focussed on the
CCD. At the same time the CCD is rapidly electronically
read to provide a raster scanned electronic signal
output. As a typical CCD preferred to be used has
31,680 pixels, the raster scanned serial outpwt signal
from the CCD results having a horizontal resolution of
about 200 pixels, with as many shades of grey as the CCD
and driving circuity is capable of.
The output signal is applied to the
digitizer/com~arator l7. The digitized signal is also
received by the microprocessor 19, which stores at least w
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portions of the received signal, resulting from a
portion of the image of the face of the object in the
scratch pad memory in memory subsystem 21, and performs
best fit search attempts to locate the portions of the
image from the EPROM, as will be described below.
Pattern recognition algorithms such as were
developed by the Department of Communications of the
Government of Canada and Copyright registered in 1990,
were used in a successful prototype of this invention,
l0 although other algorithms which can perform the method
described herein may be used.
When a match of the signals in the scratch pad
memory has been found to a stored pattern signals, the
microprocessor operates the user interface to provide a
synthesized voice indication of the denomination of the
bank note or of a resection and/or a signal to a vending
machine acceptor mechanism, etc.
Figure 3 is a more detailed block diagram of
tYbe electronic partian of the invention. The CCD and
lens mechanical movement scanning subsystem 15 (which
can be referred to as an imagery is connected to the
microprocessor 19 through a signal conditioner 30. A
microprocessor that can be used to implement the
invention is type 80C31. Also connected to the
microprocessor 19 is the 128 K EPROM and 8 K RAM, in
memory subsystem 2~..
Connected to the microprocessor is a digital
to analog converter 32, having its output connected to
one input of a comparator 34. The other input of the
comparator 34 is connected to the output of 'the CCD.
The output of the comparator is connected to an input of
microprocessor 19.
The output of the digital to analog converter
is also connected through an electronic switch 36 to the
input of an audio filter and amplifier 38, which has its
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output connected to a loudspeaker 40. Of course in the
application of a reader for the blind or for others, the
speakers can be replaced by a tactile device or other
suitable owtput device.
In operation, after being triggered to start a
cycle, the microprocessor 19 applies ;signals to the lens
scanning motor or other scanning mechanism and clock
signals to the CCD 15, which signals are conditioned in
signal conditioner 30 to shapes which will drive the CCD
and scanning motor error free. In addition, the LED
driving power is applied to the LED array 12. As a
result a raster scan output signal from the CCD
corresponding to the image printed on the face of the
bank note appears at an input of comparator 34. The
other input of the comparator 34 is supplied with d.c.
from the digital to analog converter 32. The output
signal of comparator 34 is thus a pixel by pixel
sequence representation of the face of the bank note,
which output signal is provided to miaroprocess~or 19.
When the compara~tor is to be inhibited, an
opposite polarity d.c. signal is presented to 'the input
of the comparator 34 from digital to analog converter
32, under control of microprocessor 19.
The microprocessor l9 stores seria3 sequences
of the pixel by pixel representation in the RAM portion
of memory 21, and accesses such portions, comparing them
with patterns of data signals corresponding to correct
pixel pattern representations stored in the EPROM. When --
it has found such a match, finding successive serial
pixel sequences that correlate in the correct locations
(in the correct sequence) with what is stored in the
EPROM, the microprocessor can signal a correct
comparison. Since there are normally several different
denominations of bank note pixel sequsncs
representations stored in the EPROM, the processor can
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signal the one that correlates most closely. The
microprocessor then outputs a signal via digital to
analog converter 32 indicating the denomination, or, if
a time out or predetermined number of vertical scans
have resulted in no correct bank note correlation
findings, a signal is generated which rejects the bank
note.
In order to provide a voiced indication to the
user as to the denomination or rejection, the processor
locates a signal to synthesize a preds~termined word or
ser~uence of words in the EPROM corresponding to the
aforenoted result of the memory search, enables the
closing of switch 36, and outputs the synthesized
digital signal to digital to analog converter 32. This
signal is converted to analog form in converter 32, is
passed through filter and amplifier 32, and is
reproduced as an audio signal in speaker 9:0, thus
informing the user of the acceptance and/or its
denomination or rejection of the bank note.
Figures 4A and 4B placed together with Figure
4A above Figure 4B, form a flow chart describing
operation of the microprocessor l9 processing the date
from the CCD. Once the cycle has been enabled by
triggering by the bank note sensing microswitch, the
microprocessor clears the CCD imager. It then causes
illumination of the image by the LEDs, and waits for the
CCD image integration time. The image is then read into
the array.
It should be noted that while mechanical
driving of the lens system with the CCD to pr~vide a
vertical scan has been described above, instead a row of
LEDs for illuminating the object face can be moved to
pravide the scanning, as is done in some phatocopiers.
The output of the CCD is received by the
microprocessor after digitisation, the row and column
data is calculated and the result smoothed by means of a
digital algorithmic filter, the result stored in the
RAM. The start of the rows and columns are then
digitally located to lOCate a Garner position of the
scanned image. Row and column errors are then
calculated, for example 24 scans of the image.
The EPROM is then accessed to find the best
row and beat column match. If one is found, the number
of errors of the read CCD data from the memory row and
l0 column data is determined, and if the number of errors
is smaller than a predetermined arbitrary maximum, the
voice synthesizing signal for generating a denomination
accept announcement is retrieved from 'the EPROM and sent
to the loudspeaker as described above.
If there is no match found, or if the error
rate described above is too high, a comparison is made
of the pixel sequence data with special feature data
stared in the EPROM, such as defining a holographic
image. The best match is determined and if the feature
error rate is below a predetermined maximum, the
denomination accept step is followed, as described
above. If there is no match of the special feature, or
if the error rate is too large; a synthesized
announcement signal is retrieved from the EPROM to
announce acoustically in a manner as described above of
the type such as "Bill Rejected°°, or °°Turn >3i11
Over".
Once the above sequence has been concluded
with an acoustic signal (and/or a signal to a vending
machine, change maker, etc. to accept the bill), the
cycle is concluded and the microprocessor waits for the
next trigger signal to repeat the cycle.
A person understanding this invention may
now conceive of alternative structures and embodiments
or variations of the above. All of those which fall
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within the scope of the claims appended hereto ere
considered to be part of the present invention.
