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APPENDIX G
INTERIM IAFIS IMAGE QUALITY SPECIFICATIONS FOR SCANNERS

1.0 SCOPE AND PURPOSE

These specifications were originally for the purpose of accrediting 500 ppi live scanners and card scanners integrated into automated booking stations. These Appendix G interim image quality specifications for scanners were decommissioned for IAFIS certifications in July 1999; all fingerprint systems submitted for IAFIS certification after July 1999 must meet the Appendix F requirements.

2.1 Gray-Scale Linearity

No change from Appendix F of Electronic Fingerprint Transmission Specification, dated January 29, 1999, FBI document number CJIS-RS-0010 (V7).

2.2 Geometric Image Accuracy

The absolute value of the difference "D," between the actual distance "X" between any two points on a target and the distance "Y" between those same two points as measured on the output scanned image of that target, shall meet the following requirements for the value D:

D = 0.001, for 0 = X = 0.07 D = 0.015X, for 0.07 = X = 1.50 where: D, X, Y are in inches and D = absolute value of (Y-X)

The requirement corresponds to a positional accuracy of ± 1.5% for distances between 0.07 and

  1. inches, and a constant ± 0.001 inches (1/2 pixel) for distances less than or equal to 0.07 inches.
  2. Modulation Transfer Function
cy/mm sine wave MTF
1 0.889 to 1.40
2 0.778 to 1.40
3 0.667 to 1.40
4 0.556 to 1.40
5 0.444 to 1.40
6 0.333 to 1.00
8 0.111 to 1.00
10 0.000 to 1.00

The MTF shall be measured using a sine wave test target unless scanner characteristics are incompatible with imaging a continuous tone sine wave target, in which case a bar target may be used.

2.4 Signal-to-Noise Ratio

No change from Appendix F of Electronic Fingerprint Transmission Specification, dated January 29, 1999, FBI document number CJIS-RS-0010 (V7).

2.5 Gray-level Uniformity

No change from Appendix F of Electronic Fingerprint Transmission Specification, dated January 29, 1999, FBI document number CJIS-RS-0010 (V7).

2.6 Gray-Scale Range of Image Data

At least 80% of the captured individual fingerprint images shall have a gray-scale dynamic range of at least 150 gray-levels. For this requirement, “dynamic range” is defined as the total number of gray-levels that have signal content from the fingerprint image. Fingerprint card format lines, boxes, and text shall be excluded from the dynamic range computation, and white surround in the immediate vicinity of a given fingerprint shall be included in the dynamic range computation.


 

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