Abstract

The halftone screen process for obtaining nonlinear functions with coherent optical systems utilizes a preprocessing step with an ideally hard-clipping binary input recording medium. This paper analyzes in detail the effects of using film or other media with finite gamma and saturation density. A mathematical model to predict the system performance for both one-step and two-step copying procedures is developed, and numerous computer results of parameter variation are given. It is found that nonlinear functions with threshold or jump characteristics are the most sensitive to the nonideal effects. A precompensation technique allowing nonideal copy film to be used with minimum degradation of the transfer characteristic is presented, and an algorithm for calculating compensated halftone cell shapes is given, with examples.

© 1977 Optical Society of America

Nonlinear optical processing: nonmonotonic halftone cells and phase halftones

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