High-speed hybrid optical/digital correlator system

Abstract. A hybrid optical/digital configuration to implement a high- speed correlator is described. The input data is digitally Fourier trans-formed at video rates utilizing specialized digital signal processing chip sets and the computed spectral phase data passed to an electrically addressed phase modulating spatial light modulator (SLM). Successivetemplates, which are stored as angle multiplexed volume holograms ina photorefractive crystal, are reconstructed and optically correlated with the current input scene during an interval in which the SLM display is held stable. In this way, shift invariance, one of the major advantages of the correlation technique, is preserved. Of critical importance to thespeed of operation are the energy losses of the coherent wavefront through the system and the rate at which correlation plane data can beconverted to an electronic signal; both of these issues are consideredto estimate that at least a 3-kHz search rate is achievable from a 1000template memory with system components currently available.

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