Patent US 3,947,128

A method and device for the comparison of patterns, and especially of fingerprints, making possible the identification of a given person. The device comprises means for projecting an incoherent image of the finger to be compared onto a permanent fingerprint record, oscillating same with respect to each other, projecting the resulting image onto a photocell and ascertaining the A.C.-current characteristics of the resulting electrical signal. When the finger is positioned exactly, oscillation in one direction is adequate, if not oscillations in at least two directions are to be resorted to. The image of the finger is advantageously obtained by frustrated total reflection on the totally reflecting face of a prism. The permanent record and the image may be subjected to a predetermined distortion and/or magnification according to a predetermined code, reducing the risk of forgeries.