IMPLEMENTATION OF REAL FILTERS IN A JOINT TRANSFORM CORRELATOR USING A POSITIVE-ONLY DISPLAY

An optical recognition process using real functions in a joint transform correlation is presented. We propose a new method to implement real filters in object space by using positive-only displays. Two alternatives have been tested : the filters have been recorded by means of holographic methods based on detour phase techniques, and we also propose a simple method to obtain a non-negative filter, based on the addition of a constant in order to simplify the encoding procedure. In this case, to improve discrimination in correlation, non-linear saturation effects on joint power spectrum are used. Finally, as an example, optical detection and digital simulation results are compared using composite filters as references.