Holographic Moving Map Display

Abstract

A high brightness display is achieved using tungsten sources to read out phase image-plane holograms. Full color is provided by using three superimposed component holograms derived from three primary color separation object transparencies of the original subject. The holograms are contained on transparent plastic tape which is surface modulated by embossing from electroplated masters. Any frame on the tape can be retrieved rapidly by means of the superimposed frame address Fraunhofer binary holograms which use a gallium arsenide laser to reconstruct the image on a silicon diode array. The system lends itself to post-embossing annotation. Reference Fresnel holograms recorded on each frame-enable the frame to be positioned in X and Y so as to allow the map image to be driven in response to navigational tracking requirements. Because incident readout light is modulated by diffraction rather than absorption, the holograms do not rise in temperature as a result of the conversion of light to heat. This feature enables considerably more light flux to be gated by the holograms than could be gated by any other medium of the same area. The resulting image brightness is adequate for viewing in the high ambient light environments. Since the production of color involves diffraction rather than absorption by dyed emulsion, bleaching with consequent color degradation cannot occur.