NBSIR 81-2298

NBS

PUBLICATIONS . . Results of Fingerprint Image

Quality Experiments

R. T. Moore

Institute for Computer Sciences and Technology

U S. Department of Commerce

National Bureau of Standards

Washington, DC 20234

June 1 981

If

Sponsored by:

Federal Bureau of Investigation

Automation and Research Section

Washington, DC 20535

NBSIR 81-2298

RESULTS OF FINGERPRINT IMAGE

QUALITY EXPERIMENTS

VATIOMAJL IVlUUl

or stamdasm

IWUAUT

NOV 2 3 1981

R. T. Moore

Institute for Computer Sciences and Technology

U.S. Department of Commerce

National Bureau of Standards

Washington, DC 20234

June 1981

Sponsored by:

Federal Bureau of Investigation

Automation and Research Section

Washington, DC 20535

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS. Ernest Ambler, Director
J
TABLE OF CONTENTS

Page

INTRODUCTION 2

DATA RECORDING 3

DATA PROCESSING 4

RESULTS 6

SMEARING RESISTANCE 34

SUMMARY OF PERFORMANCE 35

ACCELERATED AGEING EXPERIMENTS 38

CONCLUSIONS 40

BIBLIOGRAPHY 43

-iii-
FIGURES

Page

1. Mean single finger-pair scores vs.

type of inking 9

2. Comparison of score repeatability 12

3. CNO 3 FNO 2 14

4. CNO 3 FNO 3 15

5. Superimposed plot of common minutiae 16

6. CNO 11 FNO 1 17

7. CNO 11 FNO 1 18

8. Common minutiae of CNO 11 19

9. CNO 3 21

10. CNO 11 22

11. CNO 0 , Inkless process on St. Paul

calendered card 23

12. CNO 1, Inkless process on calendered

FBI card 23

13. Inkless process on brush coated FBI

criminal card 24

14. CNO 3, Pre-inked plastic strips,

St. Paul card 24

15. CNO 4, Pre-inked strips, calendered

FBI card 25

16. CNO 4, Pre-inked plastic strips,

FBI criminal card 25

17. CNO 6, Porous pad, St. Paul card 26

18. CNO 7, New porous pad, calendered

FBI card 26

19. CNO 8, New porous pad, FBI criminal

card 27

20. CNO 9, Old porous pad, St. Paul card 27

21. CNO 10, Old porous pad, calendered

FBIcard 28

IV
28

22. CNO 11, Old porous pad, FBI criminal

card

23. CNO 12, Ink on glass, St. Paul card 29

24. CNO 13, Ink on glass, calendered

FBI card 29

25. CNO 14, ink on glass, FBI applicant

card 30

26. CNO 103, Pre-inked plastic, St. Paul

card 30

27. CNO 105, Pre-inked plastic, FBI

criminal card 31

28. CNO 114, Ink on glass, FBI

applicant card 31

29. CNO 115, Ink on glass, FBI

criminal card 32

30. CNO 116, Pre-inked plastic,

FBI applicant card 32

31. CNO 112, ink on glass,

St. Paul card 33

32. CNO 0, Inkless process,

St. Paul card 33

33. Scores of preferred card

stocks and inking processes 42

v

RESULTS OF FINGERPRINT IMAGE QUALITY EXPERIMENTS

R. T. Moore

A series of experiments were conducted to

determine the variation in the scores developed

using a matching algorithm designated as the M-82

for mating fingerprints of different image quality

that had been read by the Automatic Fingerprint

Reader System ( AFRS) of the FBI. The variations

in image quality resulted from the use of a variety of card stocks and recording techniques to

record the print of a single finger. For each image recording process, a sample of 56 finger-pairs

were matched and mean s ingle-f inger score values

were developed. These varied over a factor of

more than 70 to one. The best scores were

developed from images placed on very white, slick

appearing, calendered card stock with the use of

film strips that had been pre-inked and which

could be separated to expose an ink film of

predetermined thickness and uniformity. This combination had less resistance to smearing than

fingerprints produced on the same stock from the

use of a pre-inked porous pad. However, the

latter still produced acceptably high scores.

Key words: Fingerprint cards; fingerprint images;

fingerprint ink; image quality.

- 1 -
INTRODUCTION

In the course of developing material for future use in an

instruction manual that is intended to help improve the

overall quality of fingerprint images that are submitted to

the FBI for processing, it was observed that images produced

using a commercially available, pre-inked, porous pad appeared to yield somewhat lower matching scores than those

produced using a film of ink rolled on a glass plate. This

observation motivated the development of a series of experiments in which a variety of card stock materials and inking

or recording techniques could be examined in order to

develop estimates of their effects on the scores that

resulted from a computerized matching process . This process uses the minutiae that are detected by machine reading

different impressions of the same fingerprint. In these experiments, every effort was made to minimize the influence

of variables other than ink and paper. All images were of a single finger, the author's number seven. Plain prints,

rather than rolled, were taken so as to minimize plastic deformation and the likelihood of smudging or smearing. Care

was taken to center the prints in the fingerboxes of the

fingerprint card using a common orientation in order to

minimize the influences of possible misregistration, and

every effort was made to produce the highest quality image

possible. Images were made using some combination of four

different types of card stock and four different inking

techniques. In addition, three types of card stock were

used with an inkless chemical fingerprint recording process.

The types of card stock that were used in the experiment are

shown in Table I TABLE I

1. An extremely white, calendered, stock that is used

by the Department of Police, Identification Unit,

Saint Paul, Minnesota.

2. The "standard" FBI criminal fingerprint card (printed in red) .

3. A calendered version of the FBI criminal fingerprint

card

.

4. The "standard" FBI applicant fingerprint card

(printed in blue)

.

The inking techniques that were used in the experiments are

shown in Table II.

-2
TABLE II

1. Pre-inked plastic strips that are separated immediately prior to use so as to expose an ink film that

had been mechanically applied in a smooth, uniform

layer of predetermined thickness.

2. A newly purchased, commercially available, porous,

pre-inked pad such as those available form the usual

suppliers of fingerprinting materials.

3. A pad identical to the one described above, but approximately six years old, although only lightly

used

.

4. Printers ink, rolled to a film, on a glass plate.

5. An inkless pad, treated with a chemical substance

which would react with other chemicals previously

applied to the card stock to leave a visible fingerprint image.

DATA RECORDING

In December 1980, fourteen fingerprint cards of data were

recorded. For each card, the author^s number seven fingerprint, an ulnar loop, was recorded in each of the ten finger

boxes. The following steps were followed in each instance:

1. The finger was washed thoroughly with warm water and soap, rinsed, and dried with a paper

towel; then it was allowed to air dry for two

minutes more.

2. The finger was placed on the ink (or chemical)

source surface and pressed moderately (about 0.1

newton force) with little or no rolling motion;

then it was lifted straight off of that surface.

3. The finger was centered over the fingerbox on

the fingerprint card, and then lowered straight

down to leave a plain impression that was not

rolled. Force used in depositing the impression

was comparable to that used in inking the finger.

4. The finger was lifted straight up off the card

and residual ink was removed by thoroughly wiping

the finger with absorbent paper tissue.

- 3 -
5. Steps 2, 3 and 4 were repeated untill all ten

fingerboxes were filled.

DATA PROCESSING

After all 14 cards of data had been recorded, the fingerprints were matched by a computer using the M82 algorithm.

Since the M-82 algorithm is arranged to match eight of the

ten fingerprints (fingers number five and ten are excluded)

normally recorded on a fingerprint card with their counterparts on a second card, an artifact was introduced to avoid

changing the normal processing routine. The minutiae list

for finger number one of card number one was inserted in

finger positions 1, 2, 3, 4, 6, 7, 8, and 9 so as to form an

artificial fingerprint card having identical minutiae data

in each of the eight finger boxes that are processed by the

M82 matching algorithm. This artificial fingerprint card

was called, "CNO 1 FNO 1" and was matched against each of

the fourteen real fingerprint cards. This process was then

repeated for finger number two of card number one (producing

CNO 1 FNO 2), etc., to create the artificial search deck of

112 fingerprint cards that was matched against all other

cards

.

In each of these 112 card matchings, the fingerprint that

was used to create the artificial card would be matched

against itself in one instance. This would produce an extremely high "identity" score which is meaningless and which

was discarded. In its place a score was substituted that

was the mean of the scores of the other seven fingers that

were different impressions of the same finger, but which

were obtained using the same fingerprint recording process.

The total card score (RST) for this artificial card was the

RST score indicated by the matcher minus the "identity"

finger score, times eight-sevenths. In other words, it is

assumed that the "identity" score could be replaced by a score equal to the mean score of each of the other seven

fingers on the card. The RST value was calculated in this

way for each of the 112 cards in the search deck. Their

mean and standard deviation were then calculated. The

single-finger mean score for each card and ink type was then

taken to be one eighth of the mean of the corrected RST

score for that type.

Although 56 pairs of fingerprints were matched to develop

the single-finger mean score, only 28 of these were unique.

This is because "a" matched against "b" produces the same

score as "b" matched agianst "a".

- 4 -
Identification of the cards is shown in Table III.

TABLE III

CNQ Recording process and type of card stock

1.

Inkless (chemical process) on calendered and machine

coated FBI criminal card.

2. Inkless on brush coated FBI criminal card.

3. Pre-inked plastic strip on St. Paul calendered card.

4. Pre-inked plastic strip on calendered FBI criminal

card

.

5. Pre-inked plastic strip on standard FBI criminal

card

.

6. New pre-inked porous pad on St. Paul calendered

card

.

7. New pre-inked porous pad on calendered FBI criminal

card

.

8. New pre-inked porous pad on standard FBI criminal

card

.

9. Old pre-inked porous pad on St. Paul calendered

card

.

10.

Old pre-inked porous pad on calendered FBI criminal

card

.

11 .

12 .

13.

14.

Old

Ink

Ink

Ink

pre-inked

rolled on

rolled on

rolled on

pad on s glass on

glass on

glass on

tandard FBI criminal ca

St. Paul calendered ca

calendered FBI crimina

standard FBI applicant

rd

.

rd

.

1 card,

card

.

-5
RESULTS

The results of the experiment

below

are shown in tabular form

TABLE IV

RST STD. 1 FING.

CNO MEAN DEV. Q.

*6 MEAN DRs DRi PCS

1 3,824 1,203 31 478 .84 .18 .81

2 151 73 49 19 . 81 . 20 .75

3 11,099 3,479 31 1,387 .93 .12 .86

4 6,609 2,253 34 826 .85 .17 .80

5 6,540 1,590 24 817 .88 . 17 .81

6 5,789 2,112 36 723 .93 .12 .87

7 5,300 1,397 26 662 .86 . 15 .83

8 655 137 21 82 . 82 .22 .80

9 7,098 2,189 31 887 .93 .19 .80

10 3,602 1,011 28 450 .86 .20 .77

11 423 160 38 53 .87 . 25 .71

12 2,641 940 36 330 .93 .18 .81

13 1,685 588 35 211 .86 .17 •

CO o 14 612 196 32 76 .86 o

CN

• .77

In the foregoing tabulation , the column labeled ii a ii "o is the

percentage that the Standard Deviation is of the 1Mean RST.

As such , it provides .an indication of the width of the distribution curve.

The " 1 FING. MEAN" column is one-eighth of the RST MEAN

The column labeled "DRs" shows the diffuse reflectivity of

the card stock measured with a commercially available reflectometer using a spot of white light having a diameter of

0.2 mm (0.008 in.)

.

It is interesting to note that the St.

Paul calendered card stock has an indicated reflectivity of

0.93. The white tile that was used to calibrate the reflectometer had a reflectivity of only 0.91.

The column labeled "DRi" shows the diffuse reflectivity of

the ink (or dye) as observed in a 0.2 mm spot selected to be

in the center of one of the darkest ridges on the card. The

reflectivity indicated by the r ef lectometer is reported to

be much less accurate for dye markings than for pigment

markings. Printers ink forms pigment based (carbon black)

markings. The basis for markings produced by the pre-inked

- 6 -
porous pad and by the chemical recording process is not

known.

The column labeled "PCS" shows the Print Contrast Signal as

computed using the relationship

(DRs) - (DRi)

PCS = (DRs)

In general, the value of PCS was higher for those cards that

scored well than for those that scored poorly, but there is

too much variability to support the use of PCS as a valid

predictor of scoring performance. For example, CNO 4 with a mean RST of 6,609 had a PCS of 0.80, while CNO 6 with a mean

RST of 5,789 had a PCS of 0.87.

Much of this variation in PCS is believed to result from the

fact that small changes in the position of the sampling spot

of the ref lectometer can produce large changes in the value

of DRi. One might speculate that use of a larger sampling

spot, or some other means of getting a better representation

of "average" ink reflectance, might provide more useful information.

Also, it is likely that a more meaningful estimate of scoring performance might be developed through the use of diffuse reflectance measurements made using illumination having

wavelengths better matched to the spectral characteristics

of the flying spot scanner that is used in the Automatic

Fingerprint Reading Systems.

Table V shows the identity of the cards when ranked by mean

single-finger scores in the first column. The second column

lists the cards in order of subjective impression of their

image quality.

- 7 -
TABLE V

CNO Ranked

by Score

3

9

4

56

7

1

10

12

13

8

14

CNO Ranked

Subjectively

3

4

6

9

5

7

10

1

12

13

14

8

11 11

2 2

Note that the subjectively ranked cards are surprisingly

close to the order that was established by ranking in accordance with score.

Figure 1 shows the mean single finger-pair scores of these

14 cards grouped by the type of inking that was used. The

highest scores were obtained when the pre-inked plastic film

strips were used. In these examples, the St. Paul calendered card stojck provided the highest scores.

dard FBI card stock gave the lowest scores,

respective inking processes.

and the stanfor each of the

- 8 -
0 500 1000 1400

PRE INKED

FILM

STRIPS

ST. PAUL CALENDERED

FBI (CRIM) CALENDERED

FBI CARD (CRIM)

NEW

POROUS

PAD

ST. PAUL CALENDERED

FBI (CRIM) CALENDERED

FBI CARD (CRIM)

OLD

POROUS

PAD

ST. PAUL CALENDERED

FBI (CRIM) CALENDERED

FBI CARD (CRIM)

INK

ROLLED

ON GLASS

ST. PAUL CALENDERED

FBI (CRIM) CALENDERED

FBI CARD (CIVIL)

INKLESS

CALNDRD & SPRAY COAT

FBI CARD-BRUSH COAT

0 500 1000 1400

1/81

Figure 1. Mean single finger-pair scores vs. type of inking.

In order to provide an estimate of the performance that would result when search and file prints were of different

- 9 -
quality, the scores were evaluated when the three highest

quality cards, CNO 3, 4 and 5, were matched against CNO 14

(rolled ink on a standard FBI criminal card). In each instance, the mean, single finger, matching pair score was an

intermediate value that was greater than the value for CNO

14, but less than the values for CNO 3, 4 or 5. CNO 3 vs.

CNO 14 yielded a value of 203; CNO 4 vs. CNO 14 produced a value of 176; and CNO 5 vs. CNO 14 gave a mean, single

finger, matching pair score of 154.

These results would tend to support the assertion that improved matcher performance would be obtained by using search

fingerprint cards of higher image quality even though the

quality of the file cards might be poorer and not subject to

upgrading

.

Upon reviewing the foregoing data, it was noted that CNO 14

was an applicant (blue printed) card whereas the other standard (non-calendered) FBI cards had all been of the criminal

(red printed) type. Also, the mean scores produced by this

card had been somewhat lower than had been expected. Therefore, on January 22, 1981, six more cards were prepared.

These cards were given a CNO that was 100 greater than the

CNO of their direct counterpart in each case where such a counterpart existed in the first data set.

They are identified in Table VI.

TABLE VI

CNO Recording process and type of card stock

103. Pre-inked plastic strip on St. Paul calendered

card

.

105. Pre-inked plastic strip on FBI criminal card.

112. Ink rolled on glass, St. Paul calendered card.

114. Ink rolled on glass, FBI applicant card.

115. Ink rolled on glass, FBI criminal card.

116. Pre-inked plastic strips, FBI applicant card.

The fingerprints were recorded on these cards using procedures that were, to the greatest extent possible, identical to those used in recording the images on the first set

- 10 -
of cards. The objectives in recording this second set of

cards were to see if there were any differences in the performance of the FBI applicant and criminal cards, and to

develop estimates of the reproducibility of the results when

every effort was made to use identical techniques at different times.

Subsequent to recording fingerprint images on these six

cards, samples of a St. Paul calendered card stock were received that had been coated for recording images with the

inkless chemical process used on CNO 1 and CNO 2. A sample

of this card stock was recorded and assigned the identification CNO 0. It was processed along with the additional six

cards described above.

The results of processing these seven cards are shown in

Table VII.

TABLE VII

MEAN STD 1 FING.

CNO RST DEV. % MEAN

0 1,572 485 31 197

103 5,267 933 18 658

105 4,058 1,360 34 507

112 7,173 1,435 20 897

114 415 206 50 52

115 1,968 860 44 246

116 2,891 578 20 361

Figure 2 shows the comparison of some of the results obtained from the impressions made in December 1980 and those

made in January 1981. There is considerable var iat ion in

the results that were obtained from the same process on the

two different occasions. This occurred even though care had

been exercised in attempting to maintain consistency in

recording the data each time.

- 11 -
CNQ 0 500 1000 1400

PRE-1NKED FILM

ST. PAUL CALENDERED

3

103

PRE-INKED FILM

FBI CRIM. CARO

5

105

INK ON GLASS

ST. PAUL CALENDERED

12

112

INK ON GLASS

FBI CIVIL CARD

14

114

Figure 2. Comparison of score repeatability.

In order to try to determine reasons for some of the wide

differences in mean finger-pair scores that were obtained

- 12 -
from the different processes, two pairs of prints were

selected for detailed analysis. The highest scoring individual pair of fingerprint impressions from CNO 3 was FNO 2

vs. FNO 3. They attained a score of 2500, nearly twice the

mean value for the card. On CNO 11, FNO 1 vs. FNO 7 was the

highest scoring pair at a value of 130. These were the four

images that were selected for detailed examination.

Plots were made at lOx enlargement of the minutiae that were

detected on each of the four fingerprints. These were compared with the fingerprint images using both direct optical

and photographic lOx enlargements. Minutiae that were subjectivly judged to be true minutia were identified. In general, there were about four or five false minutiae detected

on each of the CNO 3 images and about 30 true minutiae and

eight or ten true minutiae were not detected by the automatic reader. On the CNO 11 images, there were approximately

the same numbers of true minutiae detected and missed, but

there were many more false detections; 11 on one image and

26 on the other.

Tracings were made of the lOx scale plots of those true

minutiae that were common to both CNO 3 images (FNO 2 and

FNO 3). There were 27 of these. The tracings were then superimposed on each other in a subjectively determined "best

fit" position and the straight line displacement distance

between each mating pair of minutia was measured. Figures 3

and 4 show these two fingerprints and Figure 5 shows the

plot of superimposed minutiae. The results of the displacement measurements are shown in Table VIII.

TABLE VIII

Displacement

(mm at lOx )

0

1

2

3

7

Total minutiae = 27 Weighted

Number of

occurrences

7

11

6

2

1

mean displacement = 1.33 mm

- 13 -
Figure 3. CNO 3 FNO 2

- 14 -
Figure 4. CNO 3 FNO 3

- 15 -
Figure 5. Superimposed plot of common minutiae.
The same procedure was followed for FNO 1 and FNO 7 of CNO

11, see Figures 6, 7, and 8.

Figure 6. CNO 11 FNO 1

- 17 -
Figure 7. CNO 11 FNO 7

- 18 -
Figure 8. Common minutiae of CNO 11.

- 19 -
In this CNO 11 example there were only 15 true minutiae that

were common to both images. Their displacement distributions were also much more spread as shown in Table IX.

TABLE IX

Displacement

(mm at lOx )

0

1

2

3

4

5

6

7

Number of

occurrences

0

4

3

3

2

1

1

1

Total minutiae = 15 Weighted mean displacement = 3.0 mm

In comparing the data from these two cards, CNO 3 has matching minutia pairs that are twice as numerous, and a little

more than twice as closely collocated as CNO 11. On the

other hand, CNO 11 had a larger total number of minutia than

CNO 3 because of the many false detections. These increase

the value of the denominator of the equation that is used in

the M 82 matcher to develop the score. Collectively, these

features contribute to the development of scores for the two

sets of fingerpairs that differ by a factor of 19 times.

Study of these card images and their minutia plots reveals a suggestion of a pattern to the displacement distributions

and an indication of a posssible cause. In the case of CNO

3, the edges of the ridges are relatively sharply defined.

There are minor breaks in the inking that appear to be

caused by pores or other features that inhibit perfect contact between the surface of the friction ridges of the

finger and the smooth calendered card stock. When mating

minutiae are detected on different impressions in positions

that are displaced from each other, they are often displaced

in a direction that is normal to the ridge direction. Frequently the amount of the displacement suggests the transition of a minutia from being detected as a ridge ending in

one reading to a bifurcation in the other reading. An example of this is shown in Figure 9, a 20x photomicrograph of a portion of a fingerprint on CNO 3. Depending upon the processing of the digital filter in the fingerprint reader system, this image might result in the detection of either a ridge ending or a bifurcation at the approximate positions

- 20 -
indicated in the figure. The displacement in position that

would result if the feature was detected as a ridge ending

on one reading and a bifurcation on the other reading would

be on the order of 0.4 to 0.5 mm on the unenlarged image.

POSSIBLE

LOCATION OF

RIDGE ENDING

ALTERNATIVE

LOCATION OF

BIFURCATION

Figure 9. CNO 3

On CNO 11/ the displacements appear to occur more often in a direction that is parallel to the ridge direction. On this

card the edges of the ridges are more fuzzy. The ink appears to have been deposited more heavily on those fibers of

the card stock that are farther from the surface, while

depressed regions between these fibers received lesser

amounts of ink. The apparant location of minutiae, particularly bifurcations, can move along the direction of the

ridge as a result of digital filtering in the reader. A

crude analogy is the way that the cutting point of a pair of

scissors moves toward or away from the end of the blades by

an amount that is large compared to the motion of the blades

toward or away from each other. The paper fibers on an uncalendered fingerprint card introduce a measure of fuzziness, or noise, to the image and adds to the uncertainty of

the position at which a minutia is located.

Figure 10 is a 20x photomicrograph of a portion of a print

- 21 -
on CNO 11 showing three alternate positions at which the

reader might detect a minutia. Here, the feature that

bridges between the two ridges is believed to make it unlikely that the minutia would be detected as a ridge ending;

one of the two more widely displaced bifurcation locations

would probably be reported.

UNLIKELY. BUT

POSSIBLE, LOCATION

OF RIDGE ENDING

ALTERNATIVE

LOCATION OF

BIFURCATION

ANOTHER

ALTERNATIVE

LOCATION OF

BIFURCATION

Figure 10. CNO 11

Figures 11 through 32 are copies of photomicrographs of samples of each of the fingerprint cards. In most instances,

finger No. 6 was selected as the subject. This was simply

because that finger was relatively easy to position under

the objective lens of the microscope. These pictures were

made at an enlargement of 20x, and all of them were made using two different exposure settings; the left hand photo was

made using a constant setting and the right hand photo was

taken with one stop lower exposure. This provides a much

more dramatic demonstration of differences in contrast than

do the PCS values from the diffuse reflectance measurements.

- 22 -
Figure 11. CNO 0 Inkless process on St. Paul calendered card.

j

;l

|

Figure 12. CNO 1, Inkless process on Calendered FBI card

- 23 -
Figure 14. CNO 3. Pre-inked plastic strips, St. Paul card.

- 24 -
Figure 15. CNO 4. Pre-inked strips, calendered FBI card.

Figure 16. CNO 5. Pre-inked plastic strips, FBI criminal card.

- 25 -
Figure 17. CNO 6. Porous pad, St. Paul card.

Figure 18. CNO 7. New porous pad, calendered FBI card.

- 26 -
Figure 19. CNO 8. New porous pad, FBI criminal card.

Figure 20. CNO 9. Old porous pad, St. Paul card.

- 27 -
Figure 21. CNQ 10. Old porous pad, calendered FBI card.

Figure 22. CNO 11. Old porous pad, FBI criminal card.

- 28 -
Figure 24. CNO 13. Ink on glass, calendered FBI card.

Figure 23. CNO 12. Ink on glass, St. Paul card.

- 29 -
Figure 26. CNO 103. Pre-inked plastic, St. Paul card.

Figure 25. CNO 14. Ink on glass, FBI applicant card.

‘ Of '*?»'. r v

4 4

i * f '

£ % ,,#?<«• / i* ‘

, f * ¥

'

‘

- 30 -
Figure 27. CNO 105. Pre-inked plastic, FBI criminal card.

Figure 28. CNO 114. ink on glass, FBI applicant card.

- 31 -
Figure 29. CNO 115. Ink on glass, FBI criminal card.

Figure 30. CNO 116. Pre-inked plastic, FBI applicant card.

- 32 -
Figure 31. CNO 112. ink on glass, St. Paul card

Figure 32. CNO 0. Inkless process, St. Paul card.

-33
SMEARING RESISTANCE

Histor ically, fingerprints have been used for identification

in a manual process that involved much physical handling of

the fingerprint cards. The resistance of fingerprint images

to smearing as a result of this handling was an important

consideration, and it is expected to remain so in the future

since a considerable amount of handling and card-to-card

contact will also be involved in an automated system.

A subjective smear test was conducted on the first group of

cards early in March 1981, more than two months after that

first group of cards had been impressed with fingerprints.

This test was intended to provide a rough estimate of the

card^s ability to withstand handling as demonstrated by

resistance to smearing of the fingerprint images. Each

fingerprint card was placed on a flat table and held firmly.

Then a clean uninked finger was dragged firmly across the

image in fingerbox number five or ten using a downward force

of about 1.0 newton (5.0 lbs.). The image was then examined

for evidence of smearing. An ordinary rubber pencil eraser

was also rubbed against the image to assess its permanence

this way. A Subjective Smear Resistance (SSR) value ranging

from zero (poorest performance) to three (best) in accordance with the following descriptive scale:

SSR Description

0. Image badly smeared by finger, and probably unusable except by a latent fingerprint examiner. Image easily and completely erased with pencil

eraser

.

1. Image noticably smeared by finger. Image significantly degraded but possibly still useable. Image

easily erased with pencil eraser but leaves a faintly visible residue.

2. Slight smear observable from finger, but image not

significantly damaged. Image slightly resists ordinary pencil eraser.

3. No evidence of smearing produced by finger. Image

strongly resists ordinary pencil eraser.

Table X shows the SSR values that were assigned to each of

the cards in the first group.

- 34 -
TABLE X

CNO

1

2

3

4

5

6

7

8

9

10

11

12

13

14

SSR

3

3

1

0

2

3

3

3

3

3

3

1

0

1

Then, even though they had not aged the same amount, CNO 115

and 116 were tested for SSR and each assigned a value of

two.

No smearing was observed on any of the cards having images

produced by the inkless chemical process, or images produced

using either of the pre-inked porous pads. Some slight evidence of smearing was observable on images that had been

produced using the pre-inked plastic strips. This limited

smearing was somewhat more noticable on the calendered card

stock than on the uncalendered stocks.

The greatest amount of smearing occurred on those images

that had been produced from ink on glass. The degradation

to the images was judged to be unacceptably great on both

the calendered and on the uncalendered card stock.

SUMMARY OF PERFORMANCE

Table XI shows the summary of the experimental results

grouped by type of inking process and Table XII shows the

results grouped in accordance with the type of card stock.

- 35 -
TABLE XI

PRE- INKED PLASTIC FILM STRIPS

1 FING.

CNO CARD STOCK MEAN SSR

3 St. Paul Calendered 1,387 1

103 658

4 Calendered FBI (Crim.) 826 0

5 Standard FBI (Crim.) 817 2

105 507

116 Standard FBI (Appl.) 361 2

PRE-INKED POROUS PAD

1 FING.

CNO CARD STOCK MEAN SSR

6 St. Paul Calendered 723 3

9 887

7 Calendered FBI (Crim.) 662 3

10 450

8 Standard FBI (Crim.) 82 3

11 53

INK ON[ GLASS

1 FING.

CNO CARD STOCK MEAN SSR

12 St. Paul Calendered 330 1

112 897

13 Calendered FBI (Crim.) 211 0

115 Standard FBI (Crim.) 246 2

14 Standard FBI (Appl.) 76 1

114 52

AVERAGE

759

AVERAGE

476

AVERAGE

302

- 36 -
TABLE XII

ST. PAUL CALENDERED CARD

1 FING.

CNO INK MEAN SSR

3 Pre- inked Plastic Strip 1,387 1

103 II 658

6 Pre-inked Porous Pad 72 3

9

II 887

12 Ink on Glass 330 1

112 II 897

CALENDERED FBI CRIMINAL CARD

1 FING.

CNO INK MEAN SSR

4 Pre-inked Plastic Strip 826 1

7 Pre-inked Porous Pad 662 3

10 II 450

13 Ink on Glass 211 0

STANDARD FBI CRIMINAL CARD

1 FING.

CNO INK MEAN SSR

5 Pre-inked Plastic Strip 8T7 2

105 II 507

115 Ink on Glass 256 2

8 Pre-inked Porous Pad 82 3

11 II 53 3

STANDARD FBI APPLICANT CARD

1 FING.

CNO INK MEAN SSR

116 Pre-inked Plastic Str ip 361 2

14 ink on Glass 76

114 52 1

AVERAGE

914

AVERAGE

531

AVERAGE

AVERAGE

212

The cards using the inkless chemical process have not been

included in these summary tables because of the relatively

poor matching scores that they produced.

- 37 -
ACCELERATED AGEING EXPERIMENTS

Exposure to elevated temperature is often a useful technique

for simulating accelerated ageing. To a first approximation, each ten degrees Celsius that the temperature is

elevated doubles the ageing rate as compared with the ageing

rate of an unheated specimen. Using this rule, for example,

an hour of exposure at a temperature that was 50 degrees C.

above ambient, would be approximately the equivalent of

thirty-two hours of exposure at ambient. The process is not

believed to be linear (at least in tests on paper) as the

ageing process slows with the passage of time at elevated

temperatures

.

An accelerated ageing test using elevated temperature was

conducted on the fingerprint cards which were used in these

experiments. All 21 of the cards from both sets were placed

in a temperature controlled oven. They were stacked with a small air space between each card. This was provided by using thin steel strips as spacers between cards. The strips

were laid along the right and left edges of the cards. A

fan in the oven operated continuously and circulated air

around and between the horizontally stacked cards. The oven

temperature was maintained at 125 degrees C. This was approximately 100 degrees C. above ambient, and using the rule

of thumb described above, should accelerate initial ageing

by a factor of 1024.

After 48 hours at the elevated temperature, the cards were

removed from the oven. Diffuse reflectivity measurements

were made on CNO 1-14 and compared with the values that

were made on these cards before and reported in Table IV.

The diffuse reflectance of the card stock (DRs) was lower on

all specimens. The greatest changes occurred in CNO 1 and 2

(the inkless chemical process) . On these two cards, the

chemical that had been used to treat the card stock showed

very pronounced discoloration, and the values of DRs were

reduced to 53 to 55 percent of their original values. All

of the other cards showed much less discoloration and the

values of DRs were only reduced to about 90 to 92 percent of

their original values.

No recognizable changes in the values of the ink reflectance

(DRi) were observed.

After these reflectance measurements were made, the cards

were returned to the oven and held at 125 degrees C. for an

additional 73 hours. Then they were returned to ambient temperature and the value of DRs was determined. Only a small

further reduction in DRs was observed and nearly all of the

cards showed a final diffuse reflectance of about 87 or 88

- 38 -
percent of their original values. The St. Paul calendered

stock had a final DRs value of 0.82, and the chemically

treated stock (CNO 1 and 2) was unchanged at DRs values of

0.46 and 0.42 respectively. The remaining cards all stabilized out at DRs values of 0.75 to 0.77.

After the measurements of diffuse reflectance had been completed, the cards were read again by the automatic fingerprint reader system. They were again matched and the scores

were compared with the scores developed by the same cards

prior to the accelerated ageing process . The results are

shown in Table XIII.

TABLE XIII

1 FING. STD.

CNO MEAN RS DEV.

0 114 24%

1 427 41%

2 158 34%

3 1,286 24%

4 740 37%

5 975 20%

6 477 32%

7 608 28%

8

c 8 28%

9 563 40%

10 465 45%

11 54 66%

12 168 42%

13 196 39%

14 99 41%

103 344 25%

105 477 28%

112 593 26%

114 39 47%

115 125 36%

116 385 24%

Comparison of these data with those shown in Table IV reveals that the artificial ageing process had reduced the

diffuse reflectivity of the card stock for all specimens.

and as a consequence lowered the print contrast signal. The

- 39 -
matcher socres, however, have not always been reduced by a proportionate amount. In fact, in a few instances, the

matcher scores were actually higher after the artificial

ageing process than they were on the newly inked cards. In

most of these cases where the matcher scores have increased,

the standard deviation of the score has also increased

markedly. For example, the CNO 10 score increased by three

percent, but the standard deviation of the scores went from

28% to 45%, an increase of 62%.

On the whole, the specimens using the St. Paul calendered

card stock developed scores that were reduced by about 40%

as a result of the artificial ageing. The calendered FBI

criminal cards showed a score reduction that was much smaller, typically less than 10%. The standard FBI cards, both

criminal and applicant yielded indeterminate score results.

On some specimiens the score was higher and on others it was

lower. CNO 5 and CNO 105 from this group are particularly

interesting. The score for CNO 5 showed an increase of 19%

after ageing, and the standard deviation decreased from 24%

to 20%. The CNO 115 score only dropped 6%, and here again,

the standard deviation was less after ageing.

CONCLUSIONS

I. Significant improvements in matching scores can be

obtained through the use of calendered card stock

for taking impressions of fingerprints. The St.

Paul stock is superior to any other tested, however,

it is only smear resistant when used with the porous

pre-inked pads. The scores developed from specimens

using this card stock were significantly reduced by

the accelerated ageing process, but even after this

reduction they were still high enough to yield excellent performance.

II. Pre-inked film strips provide much better image

quality (as indicated by higher matching scores)

than any of the other inking processes that were

tested. They were the only inking process that provided consistently good results with the standard

FBI criminal card stock. They demonstrated poor

resistance to smearing on calendered card stocks.

- 40 -
III. Pre-inked porous pads yield reasonable scores on

calendered card stocks, but are considered to be

quite inferior when used with the standard FBI card

stock. Their resistance to smearing was excellent,

however, and if they are used with a calendered

stock, they probably are the best all round compromise for cost, availability, score and smear resistance .

IV. Ink on glass provides the lowest scores of any of

the inking processes. In addition, the results are

highly variable and do not provide the best smear

resistance

.

V. The standard FBI applicant card stock that was used

in these experiments developed average scores only

two-thirds as high as the criminal card stock.

Figure 33 shows a summary of the score performance of the

preferred combinations of card stock and inking process.

The original scores are shown as a solid line, and the

scores after artificial ageing are shown by a dotted line.

CNO 6 and CNO 9 are pre-inked porous pad on St. Paul calendered stock, and CNO 7 and CNO 10 are on calendered FBI

criminal card stock. CNO 5, 105 and 116 are scores produced

by the use of pre-inked film strips on standard FBI card

stocks

.

- 41 -
CNO 300 400 500 600 700 800 900 1000

1 1 1 1

1

1 PRE-INKED

6 rUnUUo rAU

ON

9

CALENDERED

STOCKS

7

10

ddc n fu w c n r n t

-

\ vi l\ t U FILM STRIPS

5

ON 10b STANDARD

116 FBI CARDS

Figure 33. Scores of preferred card stocks and inking processes.

- 42 -
BIBLIOGRAPHY

1. Moore, Raymond T. , The Influence of Ink on the Quality of Fingerprint Impressions, NBS Report NBSIR

74-627, December 12, 1974. Available from NTIS,

Springfield, Virginia 22151. Order No.

COM- 75-10134.

2. Wegstein, J. H. , "An Automated Fingerprint Identification System (The M-82)," to be published by NBS in

the near future.

- 43 -

NBS-114A (REV. 2-8C) U.S. DEPT. OF COMM. 1. PUBLICATION OR 2. Performing Organ. Report No. 3. Publication Date BIBLIOGRAPHIC DATA

SHEET (See instructions)

REPORT NO. NBSIR 81-2298 June 1981

4. TITLE AND SUBTITLE

Results of Fingerprint Image Quality Experiments

5. AUTHOR(S)

R. T. Moore

6. PERFORMING ORGANIZATION (If joint or other than N BS, see instructions) 7. Contract/Grant No. national bureau of standards

DEPARTMENT OF COMMERCE 8. Type of Report & Period Covered

WASHINGTON, D.C. 20234

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street, City. State, ZIP)

Federal Bureau of Investigation

Automation and Research Section

Washington, D.C. 20535

10.

SUPPLEMENTARY NOTES

Document describes a computer program; SF-185, FlPS Software Summary, is attached.

11.

ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a si gn i fi cant bibliography or literature survey, mention it here) A series of experiments were conducted to determine the variation in the scores developed using a matching algorithm designated as the M-82 for mating fingerprints of different image quality that had been read by the Automatic Fingerprint

Reader System (AFRS) of the FBI. The variations in image quality resulted from

the use of a variety of card stocks and recording techniques to record the print

of a single finger. For each image recording process, a sample of 56 finger-pairs

were matched and mean single-finger score values were developed. These varied over a factor of more than 70 to one. The best scores were developed from images

placed on very white, slick appearing, calendered card stock with the use of film

strips that had been pre-inked and which could be separated to expose an ink film

of predetermined thickness and uniformity. This combination had less resistance

to smearing than fingerprints produced on the same stock from the use of a preinked porous pad. However, the latter still produced acceptably high scores.

12.

KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolons)

fingerprint cards; fingerprint images; fingerprint ink; image quality

CBILITY

'j Unl imited For Official Distribution. Do Not Release to NTIS

"] Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402.

14. NO. OF

PRINTED PAGES

15. Price

] Order From National Technical Information Service (NTIS), Springfield, VA. 22161

USCOMM-DC 6043-P 80

I