Fingerprint identification system

Abstract

A method for locating minutia in a gray scale image of a fingerprint using a pair of filters, called 'Gabor' and 'Minutia' filters, includes determining direction and spacing of ridges at regularly spaced pixels, aligning filters by ridge direction, determining outputs of filters where Gabor Filter has high level output when in parallel ridge flow and, due to phase discontinuity at a minutia, low level output when in neighborhood of a minutia. The Minutia filter exhibits opposite phenomenon, having low level output in parallel ridge flow and high output in neighborhood of a minutia. A method for creating a state map of a fingerprint includes determining image quality, identifying minutia locations, determining areas of good quality where minutia are present, areas of good quality where no minutia are present and areas where quality is below a predetermined value to reliably determine presence or absence of minutia. A method for determining location of, associating, and determining number of ridges between cores and deltas in digitized gray scale of a fingerprint image by Direct Estimation of Orientated Patterns includes determining ridge angle and frequency at regularly spaced pixels, computing gradients of ridge angles, ordering gradient according to size, creating vector field of image, measuring curling of vector field, locating cores and deltas, tracing path of constant value ridge angle between deltas and cores, calculating line integral of vector frequency along straight line from delta to core.