We analyze the performance of two optical shadow-casting image correlators that use two-dimensional source arrays to encode the system point-spread function (PSF). The analysis of a standard shadow-casting correlator suggests that the angular divergence of the source array is a critical parameter in the determination of the maximum space–bandwidth product of the image and of the PSF that can be used with such a system. Further, the energy efficiency of a standard shadow-casting correlator is related inversely to the size of the PSF. We show that the constraints on energy efficiency and on the space–bandwidth product of the PSF can be overcome by beam steering the source elements. A modified shadow-casting correlator is proposed that uses phase-only blazed gratings to beam steer the sources. Experimental results generated by a mechanically beam-steered array are presented.
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