Biometric system for biometric input, comparison, authentication and access control and method therefor

Claim 1

A biometric comparison method comprising the steps of: (a) scanning in a fingerprint to and digitizing scanning signals to produce a matrix of print image data representing pixels; (b) dividing said print image data into cells, each including a number of pixel data for contiguous pixels; (c) calculating a matrix of directional image data DI using gradient statistics applied to said cells wherein said directional image data DI includes for each of said cells a cell position indicator and one of a cell vector indicative of a direction of ridge lines and an undirectional flag indicative of a nondirectional calculation result; (d) skeletonizing said print image data; (e) extracting minutia from said print image data and producing a minutia data set comprised of data triplets for each minutia extracted including minutia position data and minutia direction data; (f) providing reference fingerprint data from a database wherein said reference fingerprint data includes reference directional image data DI and a reference minutia data set; (g) performing successive comparisons of said directional image data DI with said reference directional image data DI and determining a directional difference DifDI for each of said successive comparisons wherein for each of said successive comparisons one of said directional image data DI and said reference directional image data DI is positionally shifted by adding position shift data; (h) determining for which of said successive comparisons said directional difference DifDI is the least and selecting said position shift data thereof as initial minutia shift data; (i) positionally shifting minutia data by applying said initial minutia shift data to one of said minutia data set and said reference minutia data set to initially positionally shift said minutia position data and said minutia orientation data; (j) performing successive comparisons of said minutia data set with said reference minutia data set following said positionally shifting minutia data and determining matching minutia based on a minutia distance criteria, a number of matching minutia, and a similarity measure indicative of correspondence of said matching minutia for each of said successive comparisons wherein, for each of said successive comparisons, one of said minutia data set and said reference minutia data set is positionally shifted within a minutia shift range R by adding minutia position shift data; (k) determining a maximum similarity measure of said similarity measures of said successive comparisons; and (l) determining whether said maximum similarity measure is above a similarity threshold and indicating said reference fingerprint data and said fingerprint data are from the same fingerprint when said maximum similarity measure is above said similarity threshold.