Binary phase-only filter associative memory

Abstract

An associative memory is implemented using a Binary Phase OnlyFilter as the memory element. In the current architecture, if the input contains any part of the set of stored memories, then the entire set is retrieved at the output. In addition, the sharp autocorrelation peak and the high signal to noise ratio allows operation without necessitating a thresholding device. INTRODUCTIONThere are two main approaches to implementing all optical associative mnemnories.17 The first approach relies on optical vector matrix multiplication based on spatial light modulators and Light Emitting Diodes.1 The second approach which operates directly on two-dimensional input images utilizes holograms as the storage media and some kind of saturable gain element or aperture as the threshold iuechanism.27Holograms are used as memory elements because of their high storage capability. Recently Oppenheimn and Limn have shown that the phase information is the important part for reconstructing the information.8Following this, Homer et al showed that the phase or binarized phase could be used for image correlation.911 According to the definition provided by Homer, the signal to noise ratio of the BPOF correlator was 4.5 times higher, while the height of the correlation peak was 40 times higher and the efficiency was 2.5 times higher than found in classical matched filter correlators.1213 This suggests, therefore, that the binarized phase information alone can be used to construct Ithe memory element.Most holographic associative memories share a similar architecture which consists of a correlator with a thresholding device such as a retroreflecting phase conjugate mirror utilizing a photorefractive crystal such as BaTiO3, a pinhole array in the correlation plane with an ordinary mirror, or a optical fiber used as a spatial filter.17 In this paper, we replace the holographic element with a binary phase only filter. O-8194-0692-9/91/$4.OO SPIE Vol. 1564 OpticalInformation Processing Systems andArchitectures 111(1991) / 511 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/16/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx