Abstract

Linear optical spatial filtering cannot be effectively applied to multiplied and convolved signals. One approach is to first perform a logarithmic transformation to produce a signal in additive form suitable for linear filtering processes [ A. V. Oppenheim, et al., Proc. IEEE 56, 1264 ( 1968)]. It was first suggested that a half-tone screen be used to perform such a transformation [ H. Kato and J. W. Goodman, Appl. Opt. 14, 1813 ( 1975)]. However, the maximum spatial resolution of this halftone screen technique is limited by the resolution of the screen. In this paper, we shall propose a different technique using the inherent film nonlinearity for the logarithmic transformation. Such a technique would enable the transformation of signals of very high spatial resolution, limited only by the resolution limit of the photographic film. This technique is applied to the spatial filtering and detection of signals in multiplicative noise. Experimental comparisons between linear and logarithmic filtering are presented.

© 1977 Optical Society of America

Nonlinear optical processing: analysis and synthesis

S. R. Dashiell and A. A. Sawchuk
Appl. Opt. 16(4) 1009-1025 (1977)

Nonlinear filtering in coherent optical systems through halftone screen processes

Hisatoyo Kato and J. W. Goodman
Appl. Opt. 14(8) 1813-1824 (1975)

Production of color coded equidensities using nonlinear filtering

G. Indebetouw
Appl. Opt. 16(7) 1951-1954 (1977)

Nonlinear optical processing: nonmonotonic halftone cells and phase halftones

S. R. Dashiell and A. A. Sawchuk
Appl. Opt. 16(7) 1936-1943 (1977)

Nonlinear coherent optical image processing using logarithmic transmittance of bacteriorhodopsin films

John D. Downie
Appl. Opt. 34(23) 5210-5217 (1995)