f

NBSIR 73-286 Q-)

Evaluation of Methods for Automatically

Determining the Fitness of Currency

D. P. Stokesberry and I. Philmon

Microwave & Mechanical instrumentation Section

Measurement Engineering Division

Institute for Applied Technology

August 20, 1973

Progress Report covering the period

January 1 - June 30, 1973

Prepared for Bureau of Engraving and Printing

U.S. Department of the Treasury

Washington, D. C. 20401

*NBSIR 73-286

EVALUATION OF METHODS FOR AUTOMATICALLY

DETERMINING THE FITNESS OF CURRENCY

D. P. Stokesberry and I. Philmon

Microwave & Mechanical instrumentation Section

Measurement Engineering Division

Institute for Applied Technology

August 20, 1973

Progress Report covering the period

January 1 - June 30, 1973

Note The results contained and the conclusions reached in this progress report are preliminary. Final results and conclusions will be presented in the final report.

Prepared for Bureau of Engraving & Printing

U. S. Department of the Treasury

Washington, D. C. 20401

U. S. DEPARTMENT OF COMMERCE. Frederick B. Dent, Secretary

NATIONAL BUREAU OF STANDARDS. Richard W. Roberts, Director

Table of Contents

Page

1. Summary 1

2. Tape Detection 2

3. Detection of Tears, Holes, and Missing Pieces , . 5

4. Verification of Denomination 9

5. Plans For Future Work 11

6. Biblography. . 12

ii

1 , Sumitiary

This report covers work on three parts of the

methodology of assessing the fitness of currency while it is

in motion through a transport system. These three areas of

activity are: 1) development of a method of detecting the

presence of tape on a bill, 2) development of a method of

assessing the structural integrity of a bill, and 3)

development of a method of verifying the denomination of a

bill.

The work on tape detection is a continuation of

previous work where we found that it is possible to detect

the change in thickness due to the presence of tape on a

bill with a simple contacting, moving-arm device. This

device consisted of a small, narrow roller bearing which was

spring loaded against a driving wheel of a transport

mechanism. An alternative approach is to use a contacting

arm with a lov/ enough inertia that an adequate speed of

response can be obtained without generating frictional

forces which impede the motion of the bill. This approach

to thickness measurement gives very noisy signals due to the

engraving of the printed bills. The sensor is sensitive to

the apparent thickness of the bill because it is not able to

iron out indentations in the paper due to the intaglio

printing process. These apparent variations in thickness

are of the same order of magnitude as the thickness of tape

which would be found on a bill.

Defects in the structural integrity of a bill such as

tears, holes or missing pieces can be sensed optically by

either reflection or transmission measurements. A choice

between the two depends largely upon which type of

measurement is easiest to fit onto a currency handling

transport. The transmission method requires access to both

sides of the path of the bill through the transport. The

reflection method requires access to only one side. The

detection scheme consists of multiple light sensitive

detectors which each scan a small portion of the bill

parallel to the direction of motion of the bill. The

detectors are mounted on a line perpendicular to the

direction of motion so that the entire bill is scanned as

the bill moves through the transport. This report describes

circuitry which combines the outputs from the multiple
detectors into a single indication of whether or not a bill

is structurally intact. Each detector output is converted

into a bi-level signal by comparing its instantaneous analog

value with a threshold value. The bi-level signal is high

if the bill does not interrupt the light beam and it is lov;

if the bill does interrupt the light beam. The combination

of the bi-level signals is described by one of three

possibilities: 1) all the bi-level signals are high, 2) all

the bi-level signals are lov;, or 3) some are high and some

are low. The first case describes the situation v/here no

bill is being scanned. The second case describes the

situation where the portion of the bill being scanned is

structurally intact. The third case is the situation where

the detectors indicate the presence of a defect in the

portion of the bill being scanned. The bi-level signals are

input into logic circuitry which triggers an indicator

v/henever the third case occurs. The circuit also compares

the tirae duration of the second case to insure that the bill

is the correct lengtli and triggers the indicator if it is

not. This trigger signal may be used to direct the

transport to route that bill to tlie appropriate output

pocket.

The verification of denomination is very sirailar in

na.ture to optical cliaracter recognition and pattern

recognition. Entire notes have been scanned with a document

scanner v/hich moves a small spot of light over a stationary

photographic negative of the document. Both the front and

back sides of a one, five, ten and tv/enty dollar bill have

been recorded in a form suitable for entry into a computer

so that different comparison techniques can be analyzed.

Our preliminary results show that the denomination of a

bill, under laboratory conditions, can be determined by

using a masking technique v/here the light reflected from a

bill is shovm through negative masks of the different

denominations. Under ideal conditions of perfect

registration and bill condition, no light will get through

tlie negative mask of Uie correct bill and considerable light

will come through all the other masks. When conditions are

less than ideal, the correct denomination can still be

determined by picking the i.ias]: that allows the minimum

amount of light through.

2. Tape Detection

Vve reported previously (1) that it is possible to

detect the change in thickness due to the presence of tape

2
on a bill with a simple contacting, moving arm device. This

device consists of a small, narrov; roller bearing mounted on

a short shaft which is free to pivot. The bearing is soring

loaded against a drive wheel of a transport mechanism. VJhen

a bill passes between the roller bearing and the driving

wheel, the bearing is deflected an amount equal to the

thickness of the bill. The speed of response of the device

is related to the strength of the spring and the inertia of

the roller bearing. It was found that the inertia of the

bearing is great enough that a strong spring is needed to

obtain the necessary speed of response. At the same time,

the strong spring force makes it mandatory that a roller

bearing be used to contact the bill because the frictional

forces from a non-rolling contact would greatly impede the

passage of the bill through the transport.

An alternative approach is to use a contacting arm v/ith

low enough inertia so that an adequate speed of response can

be obtained without the use of a strong spring. Then the

frictional force impeding the passage of the bill will be

lov7. A phonograph cartridge is ideally suited for this

purpose; it features an extremely high speed of response

even with a spring strength a thousand times less than that

required for the roller bearing device.

There are two basic types of phonograph cartridges,

monaural and stereo. The monaural cartridge is sensitive to

horizontal motion of its stylus and the stereo cartridge is

sensitive to both horizontal and vertical motions of its

stylus. It is much easier to mount the cartridge so that

the bill deflects the stylus vertically. Therefore, the

stereo cartridge is the preferred detector. A stereo

cartridge has two separate outputs which correspond to the

left channel and the right channel in a stereo system. The

signal due to vertical motion of the stylus is present in

both channels and so is the signal due to horizontal motion

of the stylus. The signal in one channel is the sum of the

horizontal and vertical components while the signal in tlie

other channel is the difference of the two components. This

can be expressed algebraically as

e

1

e

h

+ e V (1)

e

2

e^ (2)

where e is

1

the voltage at one output.

e

2

IS the voltage at the other output.

3
e-^ is the voltage generated by horizontal motion

of the stylus,

e is the voltage generated by vertical motion

of the stylus.

The vertical component is found by subtracting equation (2)

from equation (1) and rearranging:

e - e^

V 2

The signal e is proportional to the rnotion of the stylus,

but it is not Sensitive to the position of the stylus. This

is e^iuivalent to saying that the signal is ac coupled and

has no response to dc signals. Figure 1 shov/s the type of

response obtained v;hen a bill deflects the phonograph

stylus, notion of the stylus only occurs when there is a

change in thickness and the voltage e^ is non-zero only at

these points. An electrical signal which is proportional to

the thickness of the bill can be obtained by integrating the

signal e

V

e^ = e dt (4)

t V

v/here e^ is a voltage proportional to the thickness of the

bill, T 13 an integrating period, and A is a constant.

Figure 2 is a schematic of the circuit used to measure

the thickness of a bill while it is in motion. The outputs

e-|_ and ^2 are connected together such that the output,

designated e , is the difference between the two signals.

This signal is fed to an RC filter which integrates the

signal and then the integrated signal is amplified.

The force required to deflect the phonograph stylus is

quite small and the bill must be held doim as it moves

through the measurement area to avoid deflections of the

stylus v;hich are caused by effects other than a true change

in thickness. The signal obtained from a taped piece of

bond paper moving through the m.easurement area is shown in

Figure 3(b). The change in thickness due to the tape is

clearly visible in the middle of the waveform. This

measurement was made at a speed equivalent to a rate of

twenty bills per second. Figure 3(a) shows the signal

obtained from a taped bill under the same conditions. It is

still possible to discern the presence of the tape but the

signal is much noisier; some of the peaks approach the

4
signal level due to the tape. These peaks are caused by

variations in the apparent thickness of the bill because of

the engraving of the paper by the intaglio printing process.

The detector is a low force device and it is not able to

iron out the bill. Figure 4(a) and 4(b) show the waveforms

obtained when the phonograph cartridge monitors the

deflection of a roller bearing which is spring loaded

against the bill. It is possible to exert sufficient force

through the roller bearing to iron out the bill and obtain a

good indication of thickness. It should be possible to

devise signal processing techniques which differentiate

between apparent thickness variations and the presence of

tape but the most straightforward approach is to use a

roller bearing and strong spring forces which iron out the

bill. Thus, the engraving of the paper on a bill obviates

the advantages of direct contact with the paper with a low

tracking force device such as a phonograph cartridge.

The phonograph cartridge serves as an adequate device

to sense the deflection of the roller bearing. At present,

this approach to tape detection requires multiple devices to

scan different areas of the bill. We are investigating an

approach based on the same measurement principle, which

requires only a single cylinder which will sense the

presence of tape anywhere on the bill. This cylinder will

be long enough to cover the bill from top to bottom. It

will be spring loaded against the bill at each end and each

end will have a sensor to detect vertical motion. The

output from these two detectors will indicate the presence

of tape anywhere on the bill at low speeds and, if the

inertia of the cylinder is low enough, it will have an

adequate speed of response at twenty bills per second.

3. Detection of Tears, Holes, and Missing Pieces

Measurements of either the optical transmission or

reflection characteristics of a bill are quite sensitive to

the presence of holes, missing pieces, or tears with folded

edges. In the transmission mode, a light source is placed

on one . side of the bill and a light-sensitive detector is

placed on the other side of the bill. The attenuation of

the light is a function of the ink pattern on both sides of

the bill, but a peak value of less than ten percent of the

light incident upon the bill from the light source will pass

through the bill and reach the detector. The presence of a

defect in the paper will allow additional light to pass

through the bill and this will cause a corresponding

increase in the output signal from the detector. The
smallest size defect which is detectable depends upon the

detection method. In general, a defect which is at least

one-tenth of the area of the bill visible to the detector

will cause the detector output to rise to a level higher

than the peak signal if no defect is present. This signal is

sufficient, in theory, to insure detection. In the

reflection mode of operation, the light source and the

detector are mounted on the same side of the bill. The

reflection coefficient depends upon the ink pattern; a peak

value of less than ten percent of the light incident upon a

bill is reflected to the detector. A mirror reflects a high

percentage of the light v/hich strikes it. Therefore if a mirror is used as a reflector, the reflectance mode is very

similar to the transmission mode of operation and the

signals from the light-sensitive detectors are virtually

indistinguishable. An alternative approach is to use a

flat-blacj: reflector v;hich has an extremely lo-.-; reflection

coefficient. In this case, the presence of the bill causes

an increase in detector output signals and a defect in the

bill v^ill cause a reduction in signal strength. This m.ode

of operation is more difficult to implement because it is

hard to distinguish between a defect and the black printing

on the bill and the system is lauch m.ore sensitive to stray

light and electrical noise.

Either reflection or transmission measurements give

equivalent results, A choice between the two depends largely

upon which type of measurement is easiest to fit onto a

currency handling transport. The transmission method

requires access to both sides of the path of the bill

through the transport. The reflection method requires

access to only one side because the reflector can be part of

the transport. For example, if the transport uses a

rotating drum to move the bill, the surface of the drum may

act as a suitable reflector.

The motion of the bill through a transport system

provides a natural scanning of the bill along the direction

parallel to the motion. If a narrow strip of the bill,

perpendicular to its direction of travel, is examined, the

entire bill is scanned. This strip can be examined by one

of three ways : optically focusing the desired image onto a single detector, 2) mounting a line of small detectors to

cover the desired area, or 3) rapidly scanning a small

detector across tlie desired area. The first approach has the

advantage of using only a single light sensitive source and

light-sensitive detector. It is advantageous to need only

one light-sensitive detector because the sensitivity of

detectors is variable from unit to unit; the use of multiple

detectors requires some type of gain equilization to obtain

6
accurate measurement. The smallest perceivable defect,

however, is a function of the area of the bill seen by the

detector. The use of a single stationary detector requires

that the detector see a relatively large area and it will be

more difficult to detect small defects. The choice between

the second and third approach is largely that between using

multiple detectors, which must be calibrated, and

fabricating a suitable scanning mechanism. We have chosen

to use the multiple detector approach to demonstrate a means

of detecting tears, holes, and missing pieces.

The signals from the multiple detectors must be

combined in order to obtain a single indication of whether

or not a bill is structurally intact. Consider the response

of the detectors as a bill moves past them. Initially,

until the bill reaches the detection area, the light beam to

each detector is not interrupted and each detector output

signal is at a high level. When the front edge of the bill

interrupts the beams, the output level at each detector

falls to less than ten percent of its former value. If the

bill has no structural defects, all the output levels will

remain at a low value until the trailing edge of the bill

passes the detection area. Tears, holes, or missing pieces

will allow more light to pass through the bill and this will

cause a momentary increase in the output level of at least

one of the detectors.

Each detector output can be thought of as a bi-level

signal; the output is low when the bill interrupts the path

of the light beam from the light source to the detector and

it is high if tlie bill does not interrupt the beam. The

combination of the outputs of multiple detectors at any

instant is described by one of the follov/ing cases: 1) all

the outputs are high, 2) all the outputs are low, or 3) some

of the outputs are high and some are lov/. The first case

describes the case where no bill is being scanned. The

second case describes the case where the portion of the bill

being scanned is structurally intact. The third case is the

case v/here tiie detectors indicate the presence of a defect

in ti'ie portion of tlie bill being scanned.

Figure 5 is a block ditigran of the electronic circuitry

v/hich combines the signals fron the multiple detectors into

a single indication of the structural integrity of a bill.

The motion of the bill past the light-sensitive detectors

causes a continuously varying voltage to r^pnear at the

outj.>ut of each detector. The instantaneous value of each

output is one input to one of the voltage comparators. The

other input of the comparator is a reference voltage which

acts as a threshold value. If the output of a detector

7
exceeeis the threshold value, tlie sicjnal at the output of

that coiaparator is high. If the output of the detector is

less than the threshold value, the output of that coiaparator

is low. Thus, the comparator acts to convert the analog

signal present at the output of each light-sensitive

detector into a bi-level signal. The comparator signals

form the inputs to two digital circuits which perform the

logical AND and the logical OR functions respectively. The

output of the logical AIJD circuit is high if and only if all

of its inputs are high. Thus, a low signal is obtained

whenever the bill interrupts the beam to any detector. The

lov; signal indicates that a bill is present and the duration

of the low signal is a m.easure of bill length for a Ijill

moving at a constant known speed. The output of the logical

OR circuit is lov; if and only if all of its inputs are low.

A high output from the logical OR circuit occurs whenever

any input is high. This happens v/hen no bill is present at

tlie detectors or when tlie bill present does not sufficiently

cover one of the detectors because of a fold, tear, hole or

missing piece. The three possible states of the combination

of the outputs of the two logic circuits are listed in Table

1.

Table 1

Condition OR output AND output

No bill present Pligh High

No defect being scanned Low Low

in bill present

Defect being scanned in High Low

bill present

The two signals are the input to a circuit which looks for

the third condition and triggers an indicator whenever the

output of the OR circuit is high at the same time that the

output of the AND circuit is low. This function can be

obtained many ways. It is the natural function of an

EXCLUSIVE OR gate and it can also be obtained by inverting

the output of the logical AND and feeding this signal and

the output of the logical OR circuit into a simple NAND

gate. The indicator control circuitry also compares the

time duration of the low level state of the output of the

logical OR circuit with that expected for a fit bill moving

through the transport. If the low level state does not

exist for the correct length of time, the circuit triggers

the indicator. The trigger signal to the indicator may be

8
used to route the bill to the appropriate output pocket of

the transport.

4. Verification of Denomination

Entire notes have been scanned with a document scanner

which moves a small spot of light over a stationary

photographic negative of the ^ document. This instrument

converts the reflectance of each' point on the bill into a

voltage level and records the magnitude of the voltage at

each point on the bill onto magnetic tape in a form which is

suitable for entry into a computer. We have programmed the

computer to convert the recorded voltage magnitude into gray

levels by associating heavy printing characters with low

reflectance values and progressively lighter printing

characters with progressively higher reflectance values.

The computer printout from this program is a crude picture

of the bill.

The front and back sides of a one, five, ten and twenty

dollar bill have been scanned. The computer printout for

these scans is reproduced in Figures 6 through 9. The

document scanner digitized each scan into 160 points along

the long dimension of the bill and 64 points across the

short dimension of the bill, recording 10,240 points for

each side of each bill. This is equivalent to a spot

diameter of approximately 1 mm. Each recorded point was a

number between 0 and 15, representing sixteen possible

reflectance values. The computer program restricts the

possible number of gray levels on the printout to seven

because that was the best character set that we found. The

correlation between the sixteen voltage levels and the seven

gray levels on the printout v/as chosen to optimize the

visual quality of the pictures in Figures 6 through 9. The

picture quality clearly demonstrates that the electrical

signals generated by the scanner contain the desired

information on the denomination of a bill.

The denomination of a bill can be verified by machine

by making a point by point comparison betv/een measured

values of reflectance and those expected for a bill of a

given denomination. One powerful method of doing this is

the masking technique used in the optical character

recognition and pattern recognition fields. We have

simulated on the computer a negative mask which is placed

betv;een a bill and a light-sensitive detector. The negative

mask allows light to pass through it only at those points

9
where the image of a bill of the correct denoraination has

low reflectance values and it prevents the passage of light

at those points where tlie image of a bill of the correct

denomination has high reflectance values. If the mask is

the correct size, and if tlie image of the bill is well

registered on the mask, very little light will reach the

detector when the mask is the negative of the bill being

examined. A considerable amount of light v/ill shine through

that mask from the image of a bill of any other

denomination. Thus, the denomination of a bill can be

determined by imaging the bill through negative masks of

each possible denomination and comparing the detector

outputs to ascertain the best match. The computer printouts

obtained from the simulation program are reproduced in

Figures 10 through 25. Since only one scan of each side of

each denomination was recorded, the image of a bill through

a negative mask of itself is, by definition, completely

blank. This is the case in Figures 10(a), 12(a), 14(b),

16(b), 19(a), 21(a), 23(b) and 25(b). The rest of the

figures shov/ the result when a bill is image d through a

negative msk of a bill of a different denomination. The

light printing character indicates those points where light

reaches the detector. A summation of tlie number of these

characters indicates the magnitude of the signal output that

would be obtained from the detector. These figures indicate

that the denomination of a bill is clearly identifiable

under ideal conditions. In fact, only a few points would

need to be checked to verify denomination and the rest of

the information could be ignored.

When conditions are less than ideal, the results ^re

not as clear. A bill in motion through a transport will not

register perfectly with the mask and if the bill is not in

perfect condition the image of the bill will not correspond

exactly with its mask. For example, white paint on a bill

may give a high reflectance value to a region which should

have a low reflectance value and this light will pass

through the mask of that denomination. In this case, no

detector will have a null output and it will be more

difficult to ascertain denomination. Misregistration of the

image of the bill on the mask will also permit light to pass

through the mask of the correct denomination and, again, no

detector will have a null output. If enough light reaches

the detector because of these problems it is not possible to

verify the denomination of a bill.

Two different methods of implementing the masking

technique are under consideration. One approach is entirely

optical, where multiple images of a bill are formed. Each

image is shown through a mask onto a light-sensitive

lb
detector. The masks are each a photographic negative of one

of the different denomination bills. Additional masks of

each denomination are provided for each possible

misregistration position. As the bill moves through the

transport, its image will register on one of the masks of

the corresponding denomination and that detector will, at

that instant, have a low output signal. Continuous

comparison of the detector outputs will indicate which mask

best matches the bill and thus the denomination of the bill

is identified. This approach is particularly attractive if

it is necessary to attain high resolution, i.e., if it takes

many points to determine denomination. It requires,

however, the forming of multiple images of the bill. The

number of images and masks required depends upon the number

of denominations which must be verified and upon the number

of misregistration positions which must be covered. For

example, if there are four different denominations and three

different registration positions for each denomination,

twelve images of the bill must be formed. In addition, this

approach would probably require a clear viev; of the entire

bill. This may be difficult to obtain on some transport

systems.

The second approach is to immediately convert the image

of the bill into electrical signals and to then mask these

signals electrically. The electrical signals are loaded

into an array where the position of each signal in the array

corresponds to the reflectance value of a point on the bill.

The denonination of a bill is determined by circuits v;hich

compare the sivj-nals at each position of the array with that

expected for a bill of a given denomination and identifying

Vi/hich comparison yields the highest correlation,

nisrcicjistration can be Jianuled by shifting the position of

the signals in the array. This approach does not require

laultiplc ii.tuijes and, in fact, uogs not require a cloar view

of tliQ entire bill. If higli resolution is required,

however, the size and comple:-ity of the circuitry tends to

become uniuana'^jeablc;. A choice between these tv;o approaches

depends upon uiie number cind si:^e of the points necessary to

verify the uenomination of a bill, the effect of

misregistration on the techniques, and the availability of

an appropriate area in the transport mechanism to mount the

necessary hardv/are.

5. Plans For Future VJork

1. Develop a method of verifying the denomination of a bill

while it is in motion through a transport system.

Attention will be given to the signal degradation due to

11
misregistration of the bill in the transport raechanism.

Masks which delineate various portions of the bill will

be investigated and both electronic and optical methods

of imaging tlie bill through a mas]; will be considered,

2. Integrate the optical methods of detecting tears, holes,

and missing pieces v/ith the thickness measurement to

obtain electrical signals which specifically indicate

the presence of tape, tears, holes, missing pieces or

folds.

6 . Biblography

(1) Stokesberry, D, P. and Philmon, I., Evaluation of Methods of

Automatically Determining the Fitness of Currency, MCS Report

IIBSIR 73-143, February 1, 1973.

12
LEADING

EDGE

OF BILL

TAPE TRAILING

EDGE

OF BILL

TINE

(a) DEFLECTION OF THE SENSOR BY THE BILL

i i

TIME

T

(b) OUTPUT SIGNAL .ey , FROM THE PHONOGRAPH CARTRIDGE

TIME

(0 SIGNAL 6j OBTAINED BY INTEGRATING OUTPUT SIGNAL

Figure 1. Idealized response obtained when a bill with tape on

it is scanned by a phonograph cartridge.
CD

0)

CO fclfi % •H o P>

•p ?H

COo

(P

:3 CU

CO >^ P O

•HO CO X3 M +^ p

CmO

r-l 6 • H

aJ X3

!^

bfl CO CO

•r-l CmO

a m

•H m

-P 0)

CO6 -«

<L> o

•H ow P-

^"4
TIME

(a) SIGNAL OBTAINED FROM A TAPED BILL WITH THE DETECTOR

DIRECTLY CONTACTING THE BILL

(b) SIGNAL OBTAINED FROM A TAPED PIECE OF BOND PAPER WITH

DETECTOR DIRECTLY CONTACTING THE PAPER

Figure 3. Integrated output signal from a phonograph cartridge

directly contacting the bill.
(a) SIGNAL OBTAINED FROM A TAPED PIECE OF BOND PAPER WITH THE

DETECTOR CONTACTING THE ROLLER BEARING

(b) SIGNAL OBTAINED FROM A TAPED BILL WITH THE DETECTOR

CONTACTING THE ROLLER BEARING

Figure 4. Integrated output signal from a phonograph cartridge detector mounted on a spring loaded roller hearing.
0.04 seconds
r— CO f I

Cm

cu o

+^ >i e -H O fn Cu (U -P

CO c;

cd

tU) CO •H

CO -p

0) o

-p ^

-p 2e -p oa CmO O

-PCG

fn +^ CO •H O 0 -H O

f^

C • H —1 O

0) •H fafl a c O -H

SLh rj) -PO CO

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O

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CO •H CD T- 1—i

ft 1 1 rH o -p •H O rH

rH

d

CO 0U

•H

(in
Figure 6. Cfomputer printout of scans of the front and back of a one dollar bill.
Figure 7. Computer printout of the front and back sides of a five dollar bil]

.
Figure 8. Computer printout of the front and back sides of a ten dollar bill.
Figure 9. Computer printout of the front and back sides of a twenty dollar bill.
(A) MASK: ONE BILL: ONE

Manaw

HMMMMMWMMSUM

(B) MASK: ONE BILL: FIVE MWMMMMMMMHMMMMMMWMMMtMMWMMMMMMONWMWieaWCeMMaaMMMiMMMM^^

Figure 10. Computer printout showing where ] ight from the imges of the front sides

of a one and a five dollar bill shine through a negative mask of the front

side of a one dollar bill.
(A) MASK: ONE BILL: TEN

(B) MASK: ONE BILL: TWENTY

Figure 31. Computer printout showing where light from the images of the front sides

of a ten and twenty dollar bill shine through a negative mask of the front

side of a one dollar bin.
(A) mask: back I BILL: backi MMMMMMMMMMtHMMMMOaMttUiijaMMMMI

_ ^ MSiMttnWitMMtMMMMMnMnMt'MMittMMiMitiMMfMl6l«(^i^.i£^'^^li:

mmmmmmmmmimmmmim^

MMMMMIMMMMMMMMMMMMMMMMtMMMMMMMMMaMmM^ ^^U.

MMMMMMMMMMMMtMSCOOMMMMMaaseu.

MMMNMMMMMMMMMMMMMMMMMMMWMnsi^

MMMMMKA

•MMMMMMMMMMMMMMIMMMMMM*MMMMMMMMMMMMMatMMWtMM^

...... jf^'^'tseeMMMHMMMMnMMIMMMM*

iawwiiapBiiiMMtiiiiiuiwl

liMllllMMMWItll i^^iwL^-;^ ••••••M>«>BtttM>M>W«>MWtM>>tWMl*»aMil01«WlMW»i M!l»MB ^^_M

•»*«>«*>»t«>*t»«>M<t««>>>tW>W><tMI»»i»»l«>>MMM«M«>IIWMiMOII«lliaitrit»MlllW

(B) MASK: backi bill: back 5

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•••••••••••••••••••••••••••••••••• •••••••••••••••••••••••••••*«*e*ecfti>o«stt««««»s»oe*a***««««*««««c«««ee«o«**e«a«»»««e»* — ........— ^ |

Figure 12. Computer printout showing where light from the images of the back sides of

a one and a five dollar bill shine through a negative mask of the back side

of a one dollar bill.
(A) MASK: BACK I BILL: BACK 10

MMMMMMMMMMMMMMMMMMMMMMMM

(6) MASK: BACK I BILL: BACK 20

Figure 13. Computer printout showing where light from the images of the back sides

of a twn and twenty dollar bill shine through a negative mask of the back

side of a one dollar bill.
(A) MASK: FIVE BILL: ONE

>••••!

^••« ft«» ^a*** ( Z _ _

(B) MASK: FIVE BILL: FIVE

Figure 14. Computer printout showing where light from the images of the front sides

of a one and a five dollar bil 1 shine through a negative mask of the front

side of a five dollar bill.
(B) MASK: FIVE BILL: TWENTY

Figure 15. Computer printout showing where light from the images of the-'froht sides

of a ten and a twenty dollar bill shine through a negative mask of the front

side of a five dolBar bill.
(A) MASK: BACK 5 BILL: BACK I

• • ••• ••••••••I MMMMMMMMMMMMMMM* •••••• »

(B) MASK: BACKS BILL: BACKS

sMMMWaMGMaEit:-^ ^ ^/.seatm

Figure 16, Ccmputer printout showing where light from the images of the back sides

of a one and a five dollar bill shine through a negative mask 6t the back

side of a five dollar bill.
(A) MASK: BACK i BILL: BACK 10

(•••••I

• ••4

(B) MASK: BACK 5 BILL! BACK 20

••• • •••• M» • •••• M«» •» » *

>•»•••••• •» «* «»• •» Mft >••••• ••••»•• M» » •

b •••••••

• Mk «e9aMMM*MMMMM»«* «Mft MMMMMMMSM

> »• aft mmiiiooi * •» * •••• ••• ••• •« i »•«>*•**•••• MM** • I

I »*••••» 4

»««ft««ft**«ft««tft*ttft*«eft«* ft««ft*«

• ft ftMMft MMMaft «»• <»••

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• Aft** ft* •a ftftt

Figure 17. Computer printout showing where light from the images of the back sides of a ten

and a twenty dollar bil] shine through a negative mask of the back side of a five dollar bill.
(A) MASK: TEN BILL: ONE

(B) MASK: TEN BILL: FIVE

Figure 18. Computer printout showing where light from the images of the front sides

of a one and a five dollar bill shine through a negative madk of the front side of a ten dollar bill.
(A) MASK: TEN BILL: TEH

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uaui^

MMtMMwtMtM—timwimeiMiuiiiwwittiiimiiiMiWBW ttWtWtW—iM—M*!——iMWH lail »lWIUIH«I MIIIIll 3H9 mmmmmmmmmmmmmmmmmmtamunumimMmmi

(B) MASK: TEN BILL: TWENTY

aeaa8feii3aiaal»iMM mMWWW—WWMWMIHMI IWIl DMi llt ii«llilWIII>

•MMMMMMMMMMtWMMMMHMMMHMeewe

Figure 19. Computer printout showing where light from the images of the front

side of a ten and a twenty dollar bill shine through a negative mask

of the front side of a ten dollar bill.
I (A) MASK: BACKIO BILL: BACK I

~ ftft

ft MMtft ft «• ft •»

••••••• I ••••••• ft** i ••*•**• ft«*«** 9t ••••••• ft***** ft

ft ft ft iift ft*~Mft eft* ft ft •••••***** ft** Mft 4 ft tft** ft •••*••*•** Mttft «•••§••*•*• tft**** ft*** ft i * aft** ft  ft Mft tft Mft** ***«ft**** ft* Mft

«••••••*••••#••• MM*** •••••*•••* MM

•••••*•*•••***•

»••* 4 ^*** I

IfMt* • |» • •» •••• «f*f*

(B) MASK: BACKIO BILL: BACK 5

^Figure 20. Computer printout showing where light from the images of the back sides of a one and a five dollar bill shine through a negative mask of the back side of a ten dollar bill.
(A) MASK: BACK 10 BILL: BACK 10

(6) MASK: BACK 10 BILL: BACK 20

> • •••• *•• «»• «>« • <

• • •••••••• •••• • • •«••&•••«••••••••••••• # *» MM MMMM I • I • ••••••••••9 •••0 4

Figure 21. Computer printout showing where light from the images of the back side of a ten and a twenty dollar bill shine through a negative mask of the back

side of a ten dollar bill.
(A) MASK: TWENTY BILL: ONE

(B) MASK: TWENTY BILL: FIVE

Figure 22. Computer printout shsjwing where light from the images of the front side

of a one and a five dollar bill shine through a negative mask of the front

side of a twenty dollar bill.
(A) MASK: TWENTY BILL: TEN

(B) MASK: TWENTY BILL: TWENTY

Figure 23. Computer printout showing where light from the images of the front sides

of a ten and a twenty dollar bill shine through a negative mask of the front

side of a twenty dollar bill.
(A) MASK: BACH 20 BILL: BACK I

• M* ••••• MMM •••

>•••• #•••••••••• •••••••• fl^* tft

NM9***«* M9* ^••••t«« •••••• MM* M •••••

(B) MASK: BACK 20 BILL: BACK 5

••••• I # •••• t

Figure 24.. Computer printout showing where light from the images of the back sides

of a one and a five dollar bill shine through a negative mask of the back

side of a twenty dollar bill.
(A) MASK: BACK 20 BILL: BACK 10

>••••«

>••••«

>••*•)

(B) MASK: BACK 20 BILL: BACK 20

MMMMMMMMMMtMtMMMMMMMMMMMMMMMMn

Figure 25. Computer printout showing where light from the images of the back sides

of a ten and a twenty dollar bill shine through a negative mask of the back side of a twenty dollar bill

.
FORM NBS-M4A (1-71)

• U.S. DEPT. OF COMM. 1. PUBLICATION OR REPORT NO. 2. Gov't Accession

BIBLIOGRAPHIC DATA nBSIR 73-286

3. Recipient's Accession No.

4. TITLE AND SUBTITLE

Evaluation of Methods For Automatically

Determining the Fitness of Currency

5. Publication Date August 20,1973

6. Performing Organization Code

7. AUTHOR{S)

D. P. Stoke sherry & I. Philmon

8. PerforiTving Organization

NBSIR 73-286

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20254

10. Project/Taslc/Work Unit No.

Z.Z.60Z.A3 i-^ ww fc-^ ^

11. Contract/Grant No.

12. Sponsoring Organization Name and Address

Bureau of Engraving and Printing

Department of the TreasuryWashington, D. C. 20401

13. Type of Report & Period

Covered

Interim

January 1 - Jiinp. 30,1^7

14, Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

I- ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.)

This report summarizes the progress on developing measurement methods

necessary for the automatic handling of currency. It covers three areas- of activity: l) development of a method of detecting the presence of

tape on a bill via thickness measurements, 2) development of a method of

detecting the presence of tears, holes, or missing pieces and 3) work

towards the development of a method of verifying the denomination of a bill. All these techniques are designed to assess bills while they are

in motion through a transport system at rates up to twenty bills per

second.

17. KEY WORDS (Alphabetical order, separated by semicolons)

Defect detection; fitness of currency; pattern recognition; thickness measurement

18. AVAILABILITY STATEMENT 19. SECURITY CLASS

(THIS REPORT)

21. NO. OF PAGES

1 1 UNLIMITED.

UNCLASSIFIED

38

Q FOR OFFICIAL DISTRIBUTION. DO NOT RELEASE

to NTIS.

20, SECURITY CLASS

(THIS PAGE)

UNCLASSIFIED

22, Price

USCOMM-DC 66244-P71

(A) MASK: FIVE BILL: ONE

(B) MASK: FIVE BILL: FIVE

Figxjre 14. Computer printout showing where light from the images of the front sides

of a one and a five dollar bi]l shine through a negative mask of the front

" side of a five dollar bi!H.
(A) MASK: FIVE BILL: TEN

»•••»•«

>••• • ••••••••

(B) MASK: FIVE BILL: TWENTY

» • Mft *• • • » *•••• * 4

> OntMMMMMMMMMMMaMMMMMMM

MMMMMMMMMWa^'MM'MMMMMMMMMMMMMMM

Figure 15. Computer printout showing where light from the images of the 'frotit sides

of a ten and a twenty dollar bill shine through a negative mask of the front

side of a five dollar bill.