SPACE-VARIANT CHARACTERISTICS IN MULTIPLE OBJECT RECOGNITION WITH A COHERENT OPTICAL PROCESSOR

When the input plane of a Van der Lugt correlator contains a composite object, the output plane will in general contain several correlation peaks. When these correlation peaks overlap, the total intensity will be given by the coherent addition of the amplitudes of the individual peaks. It is shown in this paper that the total intensity depends on the phase difference between the correlation signals. The phase differences are dependent both on the displacement of the input object and any aberration in the correlator. A theoretical analysis of the system is given, showing that the interference between the correlation signals causes the total correlation intensity to change with object displacement in an oscillatory fashion rather than in a monotonic way. Some experimental verification of the theoretical predictions is also presented.