OPERATION OF OPTICAL INFORMATION-RETRIEVAL SYSTEM USING SPATIAL LIGHT-MODULATOR

Optical information retrieval systems based on Fourier optics and usin g holographic memories of high-density recording capability, which rai se the possibility of parallel information processing, have been propo sed for a long time. However, the development of spatial light modulat ors which are the key devices in such systems has been delayed conside rably and, so far, there is no report on optical information retrieval systems using spatial light modulators. With this as background, a sp atial light modulator (SLM) based on a large-permittivity crystal is f abricated and its operation in a small-size system is verified. First, based on the function of the spatial modulator, the hologram and the detection sections are designed and specifications of the system are d ecided. Next, the two different schemes of synchronous and direct dete ction methods are applied to the information retrieval of 18 bits cons isting of nine pieces of holograms. As a result, it is understood that retrieval is possible using even the currently available spatial ligh t modulators. The relation between the functions of the SLM and the sy stem also is clarified. However, there are several problems in realiza tion of such systems, a discussion of which is presented in this paper .