Browse Prior Art Database

Encoded Fingerprint File Indexing Method

IP.com Disclosure Number: IPCOM000081816D
Original Publication Date: 1974-Aug-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Gaffney, JE: AUTHOR

Abstract

This method provides a solution to the problem of providing an index to a file of encoded fingerprints, where the indices are developed from measures of the encoded fingerprints without references to any other characteristics of the persons who made them, e.g., sex, etc.

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Encoded Fingerprint File Indexing Method

This method provides a solution to the problem of providing an index to a file of encoded fingerprints, where the indices are developed from measures of the encoded fingerprints without references to any other characteristics of the persons who made them, e.g., sex, etc.

A subset of Fourier amplitude or power spectrum coefficients of the "theta array" of an encoded fingerprint, modeled as a binary waveform, is the basis for indices for the file. (See IBM Technical Disclosure Bulletin, Vol. 17, No. 3, 1974, pp 773-774.)

The aforementioned "theta array" may be thought of as being periodic in N, the number of intervals it occupies, e.g., 60 for a 6 degree per element array. Accordingly, the said array can be represented as a Fourier series, whose n/th/ harmonic amplitudes (the coefficient of the sine and cosine terms) are "a(n)" and "b(n)". The functions a(n)/2/ + b(n)/2/, square root a(n)/2/ + b(n)/2/, are the constants regardless of the original waveform, and hence are invariant with respect to the rotation of the fingerprint from which they are derived. The first step in the method is to "normalize" the values of square root a(n)/2/ + b(n)/2/ by the number of "1's" in the array. Let this value be designated, C(n), where C(n) is = a(n)/2/ + b(n)/2/ over No. of 1's. Accordingly, the C(n)/'/'s for minutiae arrays from different impressions from the same fingerprint will tend to be about the same values, even if they have different numbers of "1;s" or occupy different i...