Abstract

Key elements of the Northrop neurooptic processor¹ include an array of nonlinear processing elements (neurons) and means for effecting space-variant interconnections (synapses) between any two of these processing elements. The latter take the form of holographic phase gratings distributed within a volume of LiNbO₃. Phase encoding of processor outputs must be used to avoid Bragg cone coupling effects² and, hence, undesired interconnect degeneracies within the LiNbO₃. Phase encoding may be accomplished by using non-Gaussian optical diffusers with tunable Wiener spectra and adjustable correlation lengths within the image plane of the processor array. Diffuser design criteria include the minimization of processor output cross-correlation functions and the attainment of processor output autocorrelation functions which most closely resemble delta functions. In this paper, the analysis of an appropriate diffuser is described, and several fabrication techniques are presented. Specifically, computer-generated and optically synthesized binary diffusers derived from bandlimited Gaussian noise are discussed. Finally, an experimental setup for examining diffuser autocorrelation functions is described.

© 1986 Optical Society of America