Parallel Associative Search by use of a Volume Holographic Memory

Volume holographic memory can offer massively parallel associative search capability in addition to high capacity data storage. After holograms have been stored into a photosensitive material, an optical correlation of an input user query against all eo-locationally stored patterns can be made simultaneously, resulting in fast search speed. We describe a correlator based on a 90 degree geometry holographic data storage system using thick (-1 em) storage media, Two important parameters considered are the correlation error rate and minimum size of the search template. A minimum template area less than 0.05% relative to the whole image area has been demonstrated. Due to the strict Bragg selectivity of volume holograms in thick media, the correlator has very small sh$t invariance. Thus it lends itself best to the search of relational databases, where information can have a fixed position on the stored record. We describe a demonstration database application designed to make best use of the volume holographic correlator.