A unified treatment of real-time ULM correlators

Many studies on an optical ULM correlator have been carried out by various workers. Different types of correlation are usually produced, depending not only on the combinations of signals to be processed but also on the optical and electrical filters used in the detecting stage. This paper investigates the effects of these conditions on the performance of the optical ULM correlator in some detail on the basis of a unified analysis. It is also shown, by considering in the course of this analysis the propagation of a spatial coherence function, that the coherence property of light used for the illumination does not affect the correlation-output signal. Some experiments are performed concerned with the effect of spatial coherence, binary or intensity correlation and the linear response for correlation in the ULM correlator.