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Method and device for matching fingerprints with precise minutia pairs selected from coarse pairs

  • US 4,646,352 A
  • Filed: 06/28/1983
  • Issued: 02/24/1987
  • Est. Priority Date: 06/28/1982
  • Status: Expired due to Term
First Claim
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1. A method of deciding a degree of match between a search and a file fingerprint, comprising the steps of:

  • selecting preliminarily matched coordinate systems on the respective fingerprints;

    selecting a search and a file fingerprint area where minutiae are clear;

    forming a minutia list showing those original position and direction data of the minutiae which are given by the respective preliminarily matched coordinate systems, said minutia list furthermore showing those relation data of the minutiae which are substantially independent of said preliminarily matched coordinate systems;

    selecting pairs of minutiae from the minutiae of the respective fingerprints by comparing the original position and direction data given for the respective fingerprints and furthermore comparing the relation data given for the respective fingerprints;

    forming a pair candidate list which shows said pairs of minutiae as pair candidates, respectively;

    deciding optimum amounts of coordinate match by referring to the original position and direction data of the minutiae of said pair candidates, said optimum amounts being for precisely matching said preliminarily matched coordinate systems with each other;

    transforming the original position and direction data given by a predetermined one of said preliminarily matched coordinate systems for the minutiae of said pair candidates into transformed position and direction data given by a transformed coordinate system into which said predetermined one of the preliminarily matched coordinate systems is transformed by said optimum amounts;

    forming a pair list by referring to said minutia list, said pair candidate list, and said search and said file fingerprint areas, said pair list showing precise pairs of minutiae selected from those minutiae of said pair candidates which are present in an area common to said search and said file fingerprint areas, the minutiae of each precise pair having a precise local similarity between the transformed position and direction data and the original position and direction data given by a different one of said preliminarily matched coordinate systems and between the relation data, said different one of the preliminarily matched coordinate systems being different from said predetermined one of the preliminarily matched coordinate systems, said pair list furthermore showing evaluations, each evaluation being representative of said local similarity; and

    deciding said degree of match using the minutiae of said pair list and by referring to said evaluations.

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