Three dimensional real image display with conical holographic stereograms

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Many types of holographic stereograms have been studied due to their ability of reconstructing three dimensional images made by computers. Among then, the conical holographic stereogram is one of the most interesting methods because of the following advantages ; the facility of reconstructing floating images above the hologram surface and the possibility of observing images from the upper inclined direction. The following results are obtained in this research.(1) Since the image blur is in proportion to the distance between the image and the hologram plane, the blur tends to be large in conical holographic stereograms. To compensate this blur, a new illumination optics for reconstruction is proposed. In this method, the hologram is illuminated by the diffracted light of a grating with the same average spatial frequency as the hologram(2) To make the hologram quickly, a liquid crystal spatial light modulator(LC-SLM)is employed to record the hologram, instead of photographic transparencies with different perspectives. It is analyzed that the quality of images displayed by the LC-SLM and by the hologram.(3) As a basic study of making color holograms, it is measured spectral diffraction efficiencies of Bragg gratings made with three wavelengths. In order to make a color holographic stereogram, an optical setup is proposed by using three different laser lights and a color LC-SLM.