Patent ID: 6236741
Filing Date: 2001-05-22
Classification: A61B,G06K,G07C

Abstract:
A method of identifying fingerprints, the method comprising:acquiring a test image comprising a number of test points characterized by a quantity related to a three-dimensional structure of the fingerprints, and defining a test surface;determining significant points among said number of test points;directly verifying a local region similarity between a test region surrounding one of said significant points and a corresponding reference region of a reference image comprising a number of reference points characterized by said quantity so as to define a reference surface, wherein said test and reference regions comprise a plurality of discrete points, wherein said verifying the local region similarity comprises computing an integral norm of portions of said test and reference surfaces by performing a double summation operation; andrepeatedly verifying the local region similarity of a test region and a corresponding reference region for another of the significant points until all or a threshold amount of significant points have been verified;wherein computing the integral norm is followed by:comparing said integral norm with a second threshold value;memorizing pairs of significant test and reference points for which said integral norm is below said second threshold value;determining a rotation-translation such as to match two pairs of significant points;calculating the number of pairs of matching significant points in said test image and said reference image with the rotation-translation determined;comparing said number of pairs of matching significant points with a third threshold value; anddetermining the similarity of intermediate portions of said test and reference images between said pairs of matching significant pointswherein determining the similarity of said intermediate portions comprises:identifying a number of intermediate lines, each located in an intermediate region between a predetermined matching significant point in said test image and another matching significant point in said test image;computing the integral norm of each of said lines;comparing said integral norm of said lines with a fifth threshold value;calculating a first numerical value correlated to the number of times said integral norm of a line is below said fifth threshold value;comparing said first numerical value with a sixth threshold value; andvalidating said predetermined matching significant point if said first numerical value is at least equal to said sixth threshold value.