Apparatus for fingerprint indexing and searching

An apparatus for indexing and searching a plurality of reference fingerprints from a relatively large, selected population of individuals to determine if a sample fingerprint matches one of the reference fingerprints, the reference fingerprints having associated therewith curliness index values based upon aggregates of a rate of change of ridge direction vectors of the fingerprints, the apparatus comprising:

• indexing means for determining a curliness index value for the sample fingerprint based upon an aggregate of a rate of change of ridge direction vectors thereof wherein the index values are both generally evenly distributed and continuous over the relatively large population of individuals;
• sorting means for sorting the reference index values to define a generally continuous and generally monotonically varying function of the aggregate of a rate of change of ridge direction vectors of fingerprints of the selected relatively large population of individuals;
• selecting means for selecting a first subset of the reference fingerprints having curliness index values in a first range relative to the curliness index value of the sample fingerprint;
• and
• comparing means responsive to said selecting means for comparing the sample fingerprint to each fingerprint of the first subset of reference fingerprints to thereby determine if there is a match between the sample fingerprint and one of the reference fingerprints.