Patent Document ID: 4685145
Application ID: 06679622
Patent Status: 1

Claim One:
1. The method of providing a fingerprint image represented by a field of binary pixels comprising the steps of: a. optically imaging a finger surface or a continuous fingerprint to provide an input gray scale image of said fingerprint, said input image being a field of gray scale pixels, b. generating a first intermediate binary image using a first elongate mini-field by the method comprising the steps of: for each pixel in said gray scale image, positioning said first elongate mini-field in a predetermined association with said pixel, comparing an average gray scale value of said mini-field with the gray scale value of said pixel, and assigning a binary value to a corresponding pixel of said first intermediate binary image, said binary value being a function of the relative values of said average gray scale value and said pixel gray scale value, c. generating a second intermediate binary image using a second elongate mini-field, the elongate axes of said first and second elongate mini-fields being at substantial angles to one another, by the method comprising the steps of: for each pixel in said gray scale image, positioning said second elongate mini-field in a predetermined association with said pixel, comparing an average gray scale value of said mini-field with the gray scale value of said pixel, and assigning a binary value to a corresponding pixel of said second intermediate binary image, said binary value being a function of the relative values of said average gray scale value and said pixel gray scale value, d. generating a reference intermediate binary image, said reference intermediate binary image having directional acuity in any given locality that is intermediate between the directional acuity of said first and second binary images in said given locality, e. associating each pixel of each of said three intermediate binary images with a predetermined subfield to establish first and second correlation values respectively, said first correlation value indicating correlation between the pixels in said subfield in said first binary image and the pixels in said subfield in said reference binary image, said second correlation value indicating correlation between the pixels in said subfield in said second binary image and said pixels in said subfield in said reference binary image, and f. assigning a binary value to each pixel in a fourth binary image, said binary value in said fourth image being the binary value for the corresponding pixel from the one of said first or second intermediate binary images whose correlation value indicates the greater correlation.