GB1186169A - Device for the Coding of Finger-Prints. - Google Patents

Abstract

1,186,169. Fingerprint recognition. C.I.T.- COMPAGNIE INDUSTRIELLE DES TELECOMMUNICATIONS. 26 April, 1967 [18 May, 1966], No. 19240/67. Heading G4R. A fingerprint-identification device compares data relating to characteristic points (intermp. tions and branches) of the unknown fingerprint with stored data of reference fingerprints. Digitized video signals from a horizontal raster scan of the fingerprint are entered into a 3-bit shift register, the majority value of the contents of which, every 2 bit times, is entered into the first column of a 3-column shift register arranged serially and having 15 bit positions per column. Every 30 bit times the majority value of each of the 15 triples of bit positions in this register (each triple consisting of a correspondinglypositioned bit from each column) is entered into the corresponding position in the first column of an 8-column shift register arranged serially except that there is provision for cyclic shift (returning to the starting position) of the 8 bit positions surrounding a particular position in the second column. Logic circuitry detects characteristic points from the 8-column shift register, their positions being stored, and determines the slopes of the tangents to the print lines at these points. Groups of characteristic points are selected, each group having a predetermined number of points all within a predetermined distance of one of them which are = then arranged in the order of increasing angle between their tangents and the tangent associated with a certain one of them. The groups have as few points as possible in common. In each group, the points are joined by straight lines (notional) in the arranged order and for each such line, its length and the angle it makes with the tangent (to the print line) at each end, are determined and stored for comparison with similar data for reference prints to identify the print.