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7 November 2005 Liquid crystal grating for profilometry using structured light
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This paper describes a liquid crystal (LC) device for three dimensional profile measurement systems which are based on grating projection method using phase shifting technique. As a key component to these sytems, we propose to apply a liquid crystal (LC) grating instead of a conventional ruled grating because the grating ruled on the glass plate has difficulty in speedy and accurate shifting of the pattern. This LC grating consists of 960 lines of stripe pattern on the substrate of 60x40 mm2 in size and has such features as 8 bits of gray levels in dynamic range for 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 present properties of the LC grating we have developed and demonstrate a few examples obtained by the system which has this LC grating built in.
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Toru Yoshizawa and Hiroo Fujita "Liquid crystal grating for profilometry using structured light", Proc. SPIE 6000, Two- and Three-Dimensional Methods for Inspection and Metrology III, 60000H (7 November 2005);

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