Single modulator joint transform optical correlator: experimental results

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The traditional joint transform correlator (JTC) uses two spatial light modulators (SLMs); one to display an input scene, the other to display a filter. Each SLM requires separate transform lenses and addressing beams, as well as separate cameras to detect the Fourier transform (FT) of the scene it displays. The use of two SLMs can rapidly become expensive in terms of cost and space. The single modulator implementation of the joint transform correlator may alleviate this apparent redundancy in architecture. In the single modulator configuration the input scene and filter are alternately displayed on one SLM and addressed by a single path of light. While the SLM displays the input scene the transform plane camera detects the FT of the input scene. This is the joint transform filter. The input scene is then replaced by the filter on the SLM. While the filter is being addressed, the transform plane camera is detecting the resulting correlation signal. A driver circuit has been constructed which will multiplex the input scene and the filter onto the SLM. In addition, a demultiplexer is provided to route the filter and correlation signal, as detected by the transform plane camera, onto two separate video lines.