CJIS Electronic Fingerprint Transmission Specification

Electronic Fingerprint Transmission Specification

IAFIS

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APPENDIX G

INTERIM IAFIS IMAGE QUALITY SPECIFICATIONS FOR SCANNERS

These specifications are for the purpose of accrediting current live- and card-scan equipment integrated into automated booking stations. The complete Interim IAFIS Image Quality Specification consists of all requirements given in this document, plus all non-conflicting requirements given in the full IAFIS Image Quality Specification, Appendix F, of the "Electronic Fingerprint Transmission Specification."

IQS 2.1 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 = Y - X

The requirement corresponds to a positional accuracy of ± 1.5% for distances between 0.07 and 1.5 inches, and a constant ± 0.001 inches (½ pixel) for distances less than or equal to 0.07 inches.

IQS 2.2 Modulation Transfer Function

cyc/mm	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 test chart number M-13-60-1X manufactured by Sine Patterns, Inc., or by using any other suitable sine wave or square wave target. If using the M-13-60-1X target, the calibration curve is constructed by performing a least squares linear regression curve fit between the image gray levels of the useful density patches in the test target and the corresponding density patch values on the target.

IQS 2.3 Signal-to-Noise Ratio - no change.

CJIS-RS-0010 (V7)

112

January 29, 1999

IQS 2.4 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 requirements section, '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.

IQS 2.5 Gray-scale Linearity - no change.