Biometrics and Usability

Influence of Height and Angle on Fingerprint Collections

Charles Sheppard

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

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Reported Height Frequencies less 6”

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

39”45” 49”

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

Flat 10° 20° 30°

Adjustable Table

Angle Adjustment

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× 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)

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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

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• Age• Height• Gender• Handedness

Timing

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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

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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

Scanner A

Neither height nor angle is significant

Scanner B

Neither height nor angle is significant

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No significant affect due to angle or height

Quality

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NIST Fingerprint Imaging Software◦ Segmentation◦ Image Quality

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

No significant affect due to angle

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

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 Quality Analysis – Median NFIQ per FingerFinger

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

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NFIQ 1 or 2

NFIQ 1 or 2 or 3

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Most and Least Comfortable Angle

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Thumb Preference

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

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

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

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Angles 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