Space-variant Fresnel transform optical correlator

Abstract

A space-variant optical correlator whose output depends on both the shape and the position of the input signal is introduced. This positionally sensitive correlator has potential applications in machine vision, cryptography, and optical logic. In this approach the input function undergoes a free-space Fresnel transform (which introduces the positional sensitivity) and is multiplied by an appropriate mask function. The Fourier transform of the product then obtains the desired output. The theoretical basis for the space-variant correlator, computer-simulated outputs, and experimental results for the case in which the mask is written onto a magneto-optic spatial light modulator are discussed.