Abstract

Matched filters used for optical pattern recognition are based on holographic recordings that have to be prepared in advance either optically (by using the target itself) or by synthetic computer generation. The use of a single harmonic (circular or Mellin radial) in the recognition process, allows the addition of one invariant parameter, rotation or scale, respectively. Unfortunately, these harmonic filters have to be derived by digital computation for each object, not in real time and with a limited resolution capability. In this paper we present a novel approach for real time optical generation of universal circular or Mellin radial harmonic matched filters. The realization of this approach is based on: (a) Preparation of universal filters enabling us to perform the so-called Mellin [ln(r), h] transform and its inverse, both generated by invoking the method of saddle point integration in conjunction with Lee's computer-generated interferograms. (b) Utilization of those filters in conjunction with any input, in a 10-f optical processing setup, to generate in real time the formation of a circular or radial harmonic matched filter.

© 1989 Optical Society of America