Meltz G, Maloney W T
Appl Opt. 1968 Oct 1;7(10):2091-9. doi: 10.1364/AO.7.002091.
A real-time optical correlator is described that uses an ultrasonic light modulator (ULM) in conjunction with an amplitude mask or replica of the signal to achieve linear, phase-coherent detection, without need for high quality optics. When the mask is placed in a Fresnel image plane of the ULM, optimum correlation and collinear heterodyning are achieved. Correlator response has been calculated and measured as a function of mask-ULM separation for a pulse modulated cw signal and a square wave modulated fm waveform. For essentially band-limited signals, the output is a pair of symmetrically time-shifted, matched filter responses, possessing negligible quadratic phase distortion.
