Share Email Print

Proceedings Paper

Optical Bidirectional Associative Memories
Author(s): Bart Kosko; Clark Guest
Format Member Price Non-Member Price
PDF $14.40 $18.00
cover GOOD NEWS! Your organization subscribes to the SPIE Digital Library. You may be able to download this paper for free. Check Access

Paper Abstract

Four optical implementations of bidirectional associative memories (BAMs) are presented. BAMs are heteroassociative content addressable memories (CAMs). A BAM stores the m binary associations (A1, B1), ..., (Am, Bm) , where A is a point in the Boolean n-cube and B is a point in the Boolean p-cube. A is a neural network of n bivalent or continuous neurons ai; B is a network of p bivalent or continuous neurons bi. The fixed synaptic connections between the A and B networks are represented by some n-by-p real matrix M. Bidirectionality, forward and backward information flow, in neural nets produces two-way associative search for the nearest stored pair (Ai, Bi) to an input key. Every matrix is a bidirectionally stable hetero-associative CAM for boh bivalent and continuous networks. This generalizes the well-known unidirectional stability for autoassociative networks with square symmetric M. When the BAM neurons are activated, the network quickly evolves to a stable state of two-pattern reverberation, or pseudo-adaptive resonance. The stable reverberation corresponds to a system energy local minimum. Heteroassociative pairs (Ai, Bi) are encoded in a BAM M by summing bipolar correlation matrices, M = X1T Y1 + ... + XmT Ym , where Xi (Yi) is the bipolar version of Ai (Bi), with -1s replacing Os. the BAM storage capacity for reliable recall is roughly m < min(n, p)--pattern number is bounded by pattern dimensionality. BAM optical implementations are divided into two approaches: matrix vector multipliers and holographic correlators. The four optical BAMs described respectively emphasize a spatial light modulator, laser diodes and high-speed detectors, a reflection hologram, and a transmission hologram.

Paper Details

Date Published: 6 June 1987
PDF: 8 pages
Proc. SPIE 0758, Image Understanding and the Man-Machine Interface, (6 June 1987); doi: 10.1117/12.940062
Show Author Affiliations
Bart Kosko, VERAC, Incorporated (United States)
Clark Guest, University of California (United States)

Published in SPIE Proceedings Vol. 0758:
Image Understanding and the Man-Machine Interface
Eamon B. Barrett; James J. Pearson, Editor(s)

© SPIE. Terms of Use
Back to Top