Optical correlator performance using a phase-with-constrained-magnitude complex spatial filter.

Certain kinds of spatial light modulators (SLMs) can be used in a mode where the phase transmittance at a given point has the desired value, measured modulo-2pi, and the magnitude transmittance has approximately the desired value. Computer simulations, based on a specific model of a deformable-mirror SLM, show that these phase-with-coupled-magnitude SLMs perform better for the particular cases studied, in terms of discrimination and signal-to-clutter ratio, than phase-only and binary phase-only SLMs in coherent optical pattern-recognition correlators where the input is distorted by variable illumination, rotation, and noise relative to the template pattern.