Coherent optical processor fingerprint identification apparatus

Claim 1

Fingerprint identification apparatus comprising means for producing an optical Fourier transform pattern representative of the fingerprint to be identified, the transform pattern being characterized by diffraction lobes generally concentrically disposed about the center of the pattern where the lobes lying along any radius of the pattern are produced by fingerprint ridge lines directed normal to the particular radius, a spatial filter having light transmitting and light blocking portions positioned to rotate in the plane of the transform pattern about the center thereof, means positioned to receive light transmitted through the filter for producing an image of the fingerprint, a plurality of photodetectors positioned at the location of the image and each disposed thereat to receive light transmitted through the filter corresponding to a discrete area of the fingerprint, a plurality of peak detectors each coupled to a respective photodeteCtor for sensing a peak value of abrupt change in image light intensity at the related photodetector, a counter responsive to a signal indicative of a reference orientation of the filter for setting the counter to a starting value, means for generating a series of pulses synchronized with the angular rotation of the filter for application to the counter whereby the value in the counter at any instant is representative of the angular rotation of the filter from the reference orientation and a plurality of storage registers each coupled to the counter and to a respective peak detector and responsive to the peak detector output signal indicative of the abrupt change in image light intensity at the related photodetector for gating the instantaneous value of the counter into the associated register whereby at the end of a half revolution of the filter each register contains a digital signal representative of the ridge line orientation in the related discrete area of the fingerprint.