Abstract

A processor employing a specialized halftone screen combined with the high gamma hardclipping of a microchannel spatial light modulator (MSLM) is used to produce logarithmic transformations of image input intensities. A continuous input image is converted into a pulse width modulated binary output. The binary output is processed with a low pass filter to recover the logarithmic intensity image in a coherent optical system. Another low pass filter is used to produce a smoothed or averaged logarithmic image, which is subtracted from the original logarithmic image with an MSLM operated in its subtraction mode. The peak intensities of the resulting normalized output image are greatly enhanced. This process is a 2-D analog to a cell averaging LOG/CFAR receiver, which has been applied to radar temporal signal processing.¹ To date, the observed dynamic range of hardclip threshold of a MSLM is ~100, and the dynamic range of logarithmic transform is ~10.

© 1989 Optical Society of America