RIDGE DIRECTION EXTRACTION DEVICE, RIDGE DIRECTION EXTRACTION METHOD, AND RIDGE DIRECTION EXTRACTION PROGRAM

摘要

A ridge direction extraction unit, which analyses the shape of a ridge in a fingerprint image and extracts the ridge direction that indicates the slope of the ridge, includes: a low confidence region density value conversion module that reduces the density values in a low confidence region to generate a density conversion image; a synthesized image generating module for synthesizing a high confidence region and the low confidence region to generate a synthesized image; an auxiliary direction determining function for determining which ridge direction in the synthesized image is to be the auxiliary direction and deriving the degree of confidence in the auxiliary direction; and a high confidence region expanding module for calculating the degree of confidence in the direction, and correcting the ridge direction in the low confidence direction contiguous with the high confidence region so as to increase the degree of confidence in the ridge direction.

主权项

1. A ridge direction extraction device, comprising a ridge direction extraction unit which performs extraction of a ridge direction showing a slope direction of the ridge by analyzing shape of the ridge within a fingerprint image, wherein
the ridge direction extraction unit comprises: a ridge direction determining module which determines the ridge direction as a main direction through evaluating a density difference between a target region set on the ridge and a surrounding region connected thereto, and calculates a degree of confidence in the direction showing accuracy of the main direction; a high confidence region setting module which extracts the target region where the degree of confidence in the direction is equal to or higher than a specific value and, sets a region connected to the region as a high confidence region; a low confidence region density conversion module which generates a density converted image through decreasing a density value within the low confidence region that is the region other than the high confidence region within the fingerprint image along the determined main direction; and a synthesized image generating module which generates a synthesized image in which the high confidence region in the fingerprint image and the low confidence region in the density converted image are synthesized, the ridge direction determining module includes an auxiliary direction determining function which determines a ridge direction in the synthesized image as an auxiliary direction and derives a degree of auxiliary direction confidence that shows accuracy of the auxiliary direction, and the ridge direction extraction unit further comprises a high confidence region expanding module which calculates the degree of confidence in the direction based on the main direction in the fingerprint image and the auxiliary direction in the synthesized image, and corrects the ridge direction in the low confidence region connected to the high confidence region so as to increase the degree of confidence in the direction.