Liquid crystal real-time correlator with arbitrary bipolar real-valued input scenes

We present a real-time correlator that uses two liquid crystal spatial light modulators (SLM) to introduce the input scene and the matched filter. These liquid crystal SLMs are two twisted nematic panels that, under proper conditions, can produce amplitude-mostly or phase-mostly modulation. We propose different techniques for the implementation of bipolar real-valued scenes (with positive and negative values) in SLMs that produce amplitude-only and phase-only modulation. We apply these techniques to the implementation of bipolar real-valued scenes in a colour patten recognition problem.