HOLOGRAPHIC ASSOCIATIVE MEMORIES WITH A TRUE BRIGHTNESS TONE RENDERING

We consider the problem of a holographic associative memory (HAM) whic h must reconstruct a 2-D optical signal with corrected amplitude error s. The experimental conditions for an associative reconstruction with true brightness tone rendering by a regular HAM based on the ghost-ima ge hologram are determined, More universal all-optical error-correctin g (EC) HAMs are also presented and demonstrated. These HAMs perform a reconstruction of the second image of a stored memory that is angularl y separated from the readout beam of its partial version. We describe the scheme solution of an ECHAM problem using Denisyuk's hologram, whi ch reconstructs an error-corrected associative response in reflection. Then the original all-optical ECHAM using the so-called quadric holog ram (QH) is presented, This term here refers to a thin off-axis nonlin early recorded hologram used as the matched filter of a regular cohere nt correlator. When a QH is read out by the partial or distorted versi on of the stored memory, the complex conjugated associative response i s reconstructed at the output plane with an original brightness distri bution. A OH-based ECHAM is equivalent in efficiency to nonlinear HAMs based on the resonator architectures using phase-conjugation techniqu es and external nonlinearities, but it differs from these in arrangeme nt simplicity and implementation flexibility as an EC associative modu le of the more general neural network architectures.