abstract |
A spatial light modulator imaging system comprises an electrically addressed spatial light modulator (EASLM 4, 30 ) whose optical image output is projected onto different areas of an optically addressed spatial light modulator (OASLM, 6, 8, 31 ) in a sequence. The OASLM carries electrodes which allow separate areas to be selectively addressed by application of a voltage whilst receiving light from the EASLM. The combined output from all areas of the OASLM forms a visible image to an observer ( 11 ). When illuminated by coherent light the OASLM may produce a holographic image, otherwise incoherent light is used to provide a two dimensional image. The OASLM in one example contains a layer of nematic liquid crystal material between two cell walls both treated with an alignment layer providing low tilt surface alignment that is parallel in opposite direction; the product of layer thickness d and material birefringence Δn approximately equals one quarter of the wavelength λ of read light ( 12, 37 ). Other types of nematic devices may also be used, with cell parameters arranged to give enhanced diffraction efficiency. |