Pattern detection using a modified composite filter with nonlinear joint transform correlator

Abstract

A simple method for optical implementation of a composite filter in a joint transform correlator is presented. A composite filter in object space is a real function, but by adding an appropriate constant value, only positive values are obtained. As a drawback, the bias introduced decreases the relative height of the correlation peaks in the recognition process. Non-linear effects in a joint transform correlator are used to increase discrimination by using positive composite filters. Digital simulation and optical implementation of the process has been carried out, achieving the non-linearities by means of saturation effects on the intensity detection process.