Optical implementation of associative memory with controlled nonlinearity in the correlation domain

Abstract

A mathematical model for incorporating controllable nonlinearity in the correlation domain of a conventional associative memory is described. Such a mechanism provides the flexibility of rapidly and arbitrarily changing the strengths of the stored states in an associative memory. Such a feature corresponds to shifting of attention in psychological terms. This attentive associative memory can be implemented optically. Results obtained with computer simulation and a design for a compact optical implementation are discussed.

What Is the Significance of Neural Networks for Ai?

“…Fukushima h developed neural network model (selective attention) for character segmentation in \ Neocognitron [Fukushima (1987)]. The attentive associative memory model implement opto-electronically by Athale, Szu & Friedlander (1986) can be augmented by a priori probabili compiled by a character-pair correlation function of connected characters. This is an interesti: area for more research.…”

Higher order associative memories and their optical implementations

“…The second hologram is prepared by a similar procedure except that the associated output vectors are recorded in correspondence to each point in the two dimensional training plane. After the holograms are thus prepared, an input vector is loaded into the onedimcasional input array and the correlations between it and the M m,-.mory vectors are displayed in the OUtput plane (Athale, Szu, & Friedlander, 1986;Owechko, Dunning, Marom, & Softer, 1987;Paek & Psalfis, 1987). An optically addressed SLM can be used to produce an amplitude distribution which is the square of the incident ~ amplitudes.…”

Associative Memory Based on Nonlinear Optical Medium Properties

“…Recently considerable efforts were made to implement neural-network models [2][3][4] in optics . As a result, a number of attempts at designing an optical AM based on these models have been successful [5][6][7][8][9][10][11][12][13] . These two approaches to AM implementation have much in common .…”

“…Then, in a time interval less than the medium relaxation time a third optical pulse 8 3 (x, z, t) is fed to excite the sample . This pulse has a central optical frequency co and is resonant for transition from the ground state In> to the excitation one In,> .…”

“…As we consider the sample being thin as compared with the spatial size of the optical pulses, one can neglect the derivative a/az on the left hand side of equation (8) . Then, for an amplitude of the field being the result of the four wave mixing, it follows that…”