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23 October 2003 Three-dimensional imaging using liquid crystal grating projection
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This paper describes a device for 3D profile measurement systems which are based on grating projection method using phase shifting technique. As a key component to these systems, we propose to apply a liquid crystal (LC) grating instead of a conventional ruled grating which has difficulty in speedy and accurate shifting of the projected pattern. This LC grating consists of 960 lines of stripe pattern on the substrate of 60×40 mm2 in size and has such features as 8 bits of gray levels in dynamic range in mono-chromatic usage. A sinusoidal pattern as well as a binary pattern is realized by combining pulse width modulation control (PWMC) and frame ratio control (FRC) technique. The period of the pattern is arbitrarily controlled and, in addition, shifting of the projected pattern is also electrically realized. We demonstrate a few examples measured by the system which has this LC grating built in.
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Toru Yoshizawa, Hiroo Fujita, Yukitoshi Otani, and Masayuki Yamamoto "Three-dimensional imaging using liquid crystal grating projection", Proc. SPIE 5202, Optical Information Systems, (23 October 2003);

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