3 June 2002 Computer-generated holograms for multilevel 3D images with complex amplitude modulation
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In this report, a method of producing computer-generated holograms (CGHs) that are capable of reconstructing 3D images with higher luminosity than our previously manufactured ones is proposed. This method involves controlling etching depth and width of each cell in order to record both phase and amplitude information of the object wave. In the previous method, presented in Practical Holography XIII, interferogram data of the CGHs are computed by simulating a recording process of conventional optical holograms. This method, however, has a disadvantage in diffraction efficiency, due to the fact that only the first order diffraction of incident light contributes to reconstructing images, leaving the other orders of diffraction wasted. In order to improve the diffraction efficiency, it is desirable to modulate incident light directly to the wavefront that reconstructs the images. In this report, the cell structure that modulates both the phase and the amplitude of an incident light is proposed. The etching depth of a cell encodes phase information, and the etching width of the cell encodes amplitude information. A CGH was fabricated by forming each cell corresponding to the complex amplitude of the object wave at each sampling point of the CGH. With this method, we have succeeded in fabricating the image-type CGH that can reconstruct multilevel 3D images with about twice as high luminosity as the previous type ones.
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Mitsuru Kitamura, Mitsuru Kitamura, Tomohisa Hamano, Tomohisa Hamano, } "Computer-generated holograms for multilevel 3D images with complex amplitude modulation", Proc. SPIE 4659, Practical Holography XVI and Holographic Materials VIII, (3 June 2002); doi: 10.1117/12.469268; https://doi.org/10.1117/12.469268

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