Abstract

A 2-D associative memory of N×N input/output elements require a 4-D memory matrix of N⁴ elements. It is difficult to implement a fully parallel large size electronic associative memory in view of the 1-D interconnection limitations. Optical holographic media provides high resolution, large dynamic range, and 3-D reconstruction capabilities. These properties lead to the design of a large scale holographic associative memory (HAM) for parallel auto- and heteroassociations. A new N⁴ recording scheme has been employed in an automatic recording system that is capable of recording a 4-D memory matrix to a 2-D array of up to 256 × 256 holograms. An interpattem association training model is used to extract special features of the stored patterns and to construct excitatory and inhibitory interconnections in the associative memory. An LCTV based prototype system has been constructed and a 32 × 32 element HAM installed for real-time pattern recognition. Since most spatial domain HAMs cannot perform distortion invariant pattern recognition, a Fourier domain HAM is proposed to store multiple synthetic filters for prompt shift-scale-rotation invariant pattern recognition.

© 1991 Optical Society of America