Holographic associative memory employing phase conjugation

The principle of information retrieval by association has been suggested as a basis for parallel computing and as the process by which human memory functions.¹ Various associative processors have been proposed that use electronic or optical means. Optical schemes^2-7 in particular, those based on holographic principles^{3, 6, 7} are well suited to associative processing because of their high parallelism and information throughput. Previous workers⁸ demonstrated that holographically stored images can be recalled by using relatively complicated reference images but did not utilize nonlinear feedback to reduce the large cross talk that results when multiple objects are stored and a partial or distorted input is used for retrieval. These earlier approaches were limited in their ability to reconstruct the output object faithfully from a partial input.