Coherent optical processor apparatus with improved fourier transform plane spatial filter

摘要

A line pattern or fingerprint ridge pattern identification apparatus employs coherent optical processing techniques wherein the line or ridge orientations and spacings in a plurality of preselected finite areas of the fingerprint are inspected by means of a rotating spatial filterdisposed in the Fourier transform plane of the optical processor for cyclically selecting distinct components of the Fourier transform for transmission to the image plane of the processor in which is disposed a plurality of photodetectors each corresponding to a discrete sampled area of the print. The time delays between a reference orientation of the spatial filter and the blocking and unblocking of light transmitted therethrough toward each photodetector are noted. These values are processed to provide proportional representations thereof for storage and for subsequent comparison with similarly obtained signals representative of ridge line orientation and separation of a fingerprint presented for identification.