Abstract

The objective of this work is to identify an object out of a given set of objects. Shift invariance is automatically achieved by employing spatial filters in the Fourier transform plane. To relax the strict alignment and stability requirements of the holographic filter, we use bipolar amplitude filters with minimum information content that is still sufficient for the required pattern recognition. For complete rotation invariance one may use filters with rotation symmetry, while for scale invariance, filters that are independent on the radial coordinate may be employed. Partial invariances combined in a single filter are also investigated. Theoretical considerations augmented with computer simulation are used for the determination of acceptable recognition criteria and for the synthesis of practical filters. The feasibility of the method was demonstrated by computer simulations and some preliminary experiments.

© 1986 Optical Society of America