Method and device for matching fingerprints with precise minutia pairs selected from coarse pairs
First Claim
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.
1 Assignment
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Accused Products
Abstract
A pair candidate list (73) is formed by selecting minutia pairs with reference to a minutia list (71) showing original position and direction data given for minutiae by principal coordinate systems preliminarily selected on a search and a file fingerprint and those relation data of the minutiae which are substantially independent of the coordinate systems. It is very likely that the pair candidate list shows coarse pairs because the coordinate systems may not yet be optimally matched to each other. One of the coordinate systems is transformed by those optimum amounts to provide transformed position and direction data which are decided by the original position and direction data of the minutia pairs of the pair candidate list. A pair list (86) is formed by precisely selecting minutiae from the pair candidate list with reference to the transformed position and direction data and the original position and direction data given by the other principal coordinate system and to the relation data. On forming the pair list, an additional minutia list (81) is preferably formed which shows the transformed position and direction data and the last-mentioned original position and direction data together with the relation data.
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Citations
10 Claims
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1. A method of deciding a degree of match between a search and a file fingerprint, comprising the steps of:
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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. - View Dependent Claims (2, 3)
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4. A fingerprint matching device for deciding a degree of match between a search and a file fingerprint, comprising:
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minutia list producing means (71, 72,
81) for producing a minutia list showing those original position and direction data of minutiae which are given by preliminarily matched coordinate systems selected on said search and said file fingerprints, respectively, said minutia list furthermore showing those relation data of said minutiae which are substantially independent of said preliminarily matched coordinate systems;fingerprint area memory means (87) for memorizing a search and a file fingerprint area where the minutiae are clear; selecting means (77) coupled to said minutia list producing means for selecting pairs of minutiae from the minutiae of the respective fingerprints, said pairs of minutiae having similar original position and direction data given for the respective fingerprints and furthermore similar relation data given for the respective fingerprints; pair candidate list memory means (73) coupled to said selecting means for memorizing a pair candidate list which shows said pairs of minutiae as pair candidates, respectively; optimum amount deciding means (78,
75) coupled to said minutia list producing means and said pair candidate list memory means for 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;coordinate transforming means (72) coupled to said minutia list producing means, said pair candidate list memory means, and said optimum amount deciding means for transforming a predetermined one of said preliminarily matched coordinate systems into a transformed coordinate system by said optimum amounts, said coordinate transforming means thereby transforming the original position and direction data given by said predetermined one of the preliminarily matched coordinate systems for the minutiae of said pair candidates into transformed position and direction data; pair list memory means (86,
83) coupled to said minutia list producing means, said pair candidate list memory means, and said fingerprint area memory means for memorizing a 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; anddeciding means (89) coupled to said pair list memory means for deciding said degree of match by using the minutiae of said pair list and by referring to said evaluations. - View Dependent Claims (5, 6, 7, 8, 9, 10)
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Specification