SPATIAL LIGHT-MODULATOR USING POLYMER-DISPERSED LIQUID-CRYSTAL - DEPENDENCE OF RESOLUTION ON READING LIGHT-INTENSITY

A spatial light modulator consisting of a polymer-dispersed liquid cry stal (PDLC) film, a dielectric mirror, and a Bi12SiO20 photoconductor is useful for projection-type displays, optical image processing, and optical computing. However, a portion of the reading light scattered b y the PDLC film passes through the dielectric mirror and illuminates t he photoconductor, thus causing deterioration of display-image quality . This article reports on the results of a detailed study on the influ ence of reading light on the resolution and amplification factor, whic h is the ratio of reading light intensity to the maximum intensity of writing light. Angular distributions of light scattered by a PDLC cell were measured and the results were used to calculate the intensity of scattered light absorbed by the photoconductor. We then analyzed the optical input/output characteristics of the spatial light modulator wi th regard to the optical feedback effect caused by the reading light i n order to discover the parameter for evaluating image quality. The re lation between amplification and resolution is derived from this param eter. We have also considered a light absorption layer for preventing the deterioration of image quality and obtained the relation between t he amplification factor and the transmittance of the light absorption layer for high definition images of high brightness. Finally, these th eoretical results were confirmed by an experiment using a spatial ligh t modulator with no dielectric mirror.