Abstract

Although 2-D optical signal processors inherently have a higher bandwidth than 1-D processors, the postprocessing load is also higher. In particular, nonuniformities and buildup in the background level often must be corrected dynamically before feature extraction processing. A microchannel spatial light modulator (MSLM) operating in its synchronous detection mode can detect features oscillating periodically against a quasistatic background. In this mode of operation the MSLM erase-field is identical to the write-field except that during the erase cycle the intensity of the oscillating feature is near its minimum. Thus, background features are alternately written and erased, while the feature of interest is repeatedly written. Two-dimensional optical output fields are often used in radar and sonar processing, e.g., to display both range and Doppler information. We use a coherent optical processor that displays correlations as blinking lights due to a periodic phase modulation.¹ When synchronized to this signal the MSLM becomes a sensitive 2-D photodetector (0.001 μJ/cm²) that employs lock-in detection on every pixel in parallel. The SNR is proportional to integration time and inversely proportional to effective noise bandwidth.

© 1987 Optical Society of America