Biometrics and Usability

Influence of Height and Angle on Fingerprint Collections

Charles Sheppard

Biometrics and Usability

22

Given current surface heights, what is the “best” angle?

Question by US-VISIT

Biometrics and Usability

33

Heights

3033353637.5

38394346474849

0

20

40

60

80

100

Reported Height Frequencies less 6”

3033353637.5

38394346474849

0

20

40

60

80

100

Biometrics and Usability

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Choose three heights◦ 39”◦ 45” Practical Midpoint◦ 49”

Heights

39”45”

49”

Biometrics and Usability

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Selected Range of Angles◦ Flat◦ 10 °◦ 20 °◦ 30 °

Angles

Flat 10° 20° 30°

Adjustable Table Angle Adjustment

Equipment

Biometrics and Usability

77

Data

× 4 angles = 48 prints/height

12 prints/angle

× 20 people = 960 prints per height

× 3 heights = 2,880 prints/scanner

× 2 scanners = 5,760 total prints

(120 people total)

Biometrics and Usability

88

Given current surface heights, what is the “best” angle?

Best = ◦ Efficient —Timing — Time to complete task◦ Effective — Quality — How good were the prints◦ Satisfaction — Comfort — Questionnaire

Question

Demographics

Biometrics and Usability

1010

• Age• Height• Gender• Handedness

Test population was representative of the user population with respect to:

EfficiencyTiming

Biometrics and Usability

1212

Timing

12

Opportunity (“please place your hand on the scanner”)

System starts capture

Capture

System ends capture (“Please remove hand from scanner”)

Capture thresholding

Time

System

Participant presentsAttempt starts

Attempt

Attempt ends

Next attempt(acceptable

attempt)

Participant

Scanner A

Biometrics and Usability

1313

Timing

13

Opportunity (“please place your hand on the scanner”)

Capture

System ends Attempt (“Please remove hand from scanner”)

Capture thresholding

Time

System

Participant presentsAttempt starts

Attempt

Attempt ends

Next attempt(acceptable

attempt)

Participant

Scanner B

Timing — Median Times per Slap

0 10 20 309.00

9.50

10.00

10.50

11.00

Median Time Per Task vs. Angle

(across all heights and tasks)

Angle

Tim

e

39 45 499.00

9.50

10.00

10.50

11.00

Median Time Per Task by Counter Height

(across all angles and tasks)

Table Height

Tim

e

Scanner A

Neither height nor angle is significant

Timing — Median Times per Slap

Scanner B

39 45 4916.0016.1016.2016.3016.4016.5016.6016.7016.8016.9017.00

Median Time Per Task by Counter Height

(across all angles and tasks)

Counter Height

Tim

e

Flat 10 20 3016.00

16.20

16.40

16.60

16.80

17.00

Median Time Per Task vs. Angle(across all heights and table

heights

Angle

Tim

e

Neither height nor angle is significant

Biometrics and Usability

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No significant affect due to angle or height

Timing

EffectivenessQuality

Biometrics and Usability

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NIST Fingerprint Imaging Software◦ Segmentation◦ Image Quality

Quality Measures

Biometrics and Usability

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Two levels of analysis1. Individual finger NFIQ — Medians2. Individual finger NFIQ frequencies

Quality Analysis - Angle

No significant affect due to angle

Biometrics and Usability

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Two levels of analysis1. Individual finger NFIQ — Medians2. Individual finger NFIQ frequencies

Quality Analysis - Height

Significant differences were found across different counter heights, the effect of which appears to be scanner dependent

Finger #

Task #

Table Height

2 1 39”>45”. 45”<49”3 1 39”>454 1 39”>45”5 1 39”>45”7 3 39”>45”8 3 39”>49”9 3 39”>45”

10 3 +. 39”>451 2 39”>45”. 45”<49”6 4 -

11 5 -12 5 -

1

2345

6

7 8 910

1112

Quality Analysis – Median NFIQ per Finger

Finger #

Task #

Table height

2 1 -3 1 *39”>45”4 1 39”<45”. 45”<49”5 1 -7 3 -8 3 -9 3 -10 3 39”<45”. 45”<49”1 2 39”>45”. 45”<49”6 4 -11 5 -12 5 _

Scanner A Scanner B

Biometrics and Usability

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US visit quality scoring.

NFIQ 1 or 2

NFIQ 1 or 2 or 3

Biometrics and Usability

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US visit quality scoring.

Right Slap Right Thumb Left Slap Left Thumb Both Thumbs

57.58%

82.20%

54.92%

71.21% 70.83%

63.23%

80.35%

59.83%

79.39%

60.17%

Scanner A Scanner B

satisfactionMost and Least Comfortable

Angle

Biometrics and Usability

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0 deg 10 deg 20 deg 30 deg None0

2

4

6

8

10

12Scanner B

39

45

49

Parti

cipa

nt C

ount

Scanner A39

45

49

Most Comfortable Angle

Biometrics and Usability

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0 deg 10 deg 20 deg 30 deg02468

10121416

Scanner B

39

45

49.

0 deg 10 deg 20 deg 30 deg none02468

10121416

Scanner A39

45

49

Parti

cipa

nt C

ount

Least Comfortable Angle

satisfactionThumb Preference

Biometrics and Usability

3030

Both Single

No Answer

0

2

4

6

8

10

12Scanner B

39

45

49

Coun

t of P

artic

ipan

ts

02468

1012141618 Scanner A

39

45

49

Parti

cipa

nt C

ount

Thumb Preferences

Observations

6’6” Individual having to bend knees to position hand comfortably.

39” 30°

5’2” individual having to stand on toes to reach scanner.

49” 0°

5’2” individual not having to stand on toes to reach scanner.

49” 30°

Biometrics and Usability

3535

ConclusionsAngles have no impact on performance Height does affect qualityParticipants when given a choice start with

their right hand

Participants preferred 20° and 30° angles as counter height increased

Shorter participants struggled less at the taller counter heights when scanner was angled