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The opportunity to process signals in domains other than the time or frequency domains arises naturally in coherently illuminated optical systems that produce Fourier transforms. It is well known that N samples are sufficient to represent the information content in the object, image, and Fourier planes. We extend these results to show that we can accurately represent the intensity signal in any Fresnel plane of a coherently illuminated optical system with exactly N samples, provided that we use a specified nonuniform sampling technique.

We develop the general scanning relationships of an acousto-optic system by using both a purely geometric-optics and a physical-optics approach; each approach provides useful insights into the scanning relationships. The diffraction approach reveals that there are four basic scanning configurations: a long or short chirp scanner, either aperture or repetition-rate limited. The throughput rate for a scanner is always maximized if we use the short-chirp-scanning, repetition-rate-limited mode of operation. The maximum rate may be achieved with other configurations, but at the expense of a decrease in some of the other performance parameters. Examples are given of how these design relationships are used.

Optical signal processing applications place demands on photodetector arrays beyond those encountered in image sensing applications. We review the basic requirements and show that increased dynamic range and nonlinear decision operations that lead to reduced output data rates are the key improvements needed for both 1-and 2-D arrays. Arrays of high-speed photodetector elements with integrated postdetection circuitry are also needed. Although we suggest some possible methods for achieving these goals, our main objective is to stimulate the photodetector community to design and fabricate more useful devices.

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