Phase-only and binary phase-only filters in optical correlators.

摘要

The optimal design of phase-only filters (POFs) (filters with unit magnitude) and binary phase-only filters (BPOFs) (filters with unit magnitude and 2 phase levels) for optical correlators is investigated. Rigorous derivations of the optimal phase function for POFs and the optimal phase assignment for BPOFs are provided. The optimal support function (indicating which spatial frequencies are not blocked) is analytically characterized and a set of very efficient algorithms for support selection is presented. The improvement in performance due to this optimization is illustrated with the help of several analytical examples as well as computer simulations using realistic images. This improvement is seen to be as high as 5 dB in output Signal-to-Noise Ratio (SNR). The effect of detector noise on the optimal design of POFs and BPOFs is studied, and the distortion sensitivity of the various filters is tested. Two novel approaches for designing phase-only and binary phase-only Synthetic Discriminant Functions (SDFs) are presented. The results of our experimental work using the filters in question are presented. The design of a simple real-time pattern recognition system is used to illustrate how our optimized filters can be used in practice.