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Title: Shape measurement by use of liquid-crystal display fringe projection with two-step phase shifting
Authors: Quan, C. 
Tay, C.J. 
Kang, X. 
He, X.Y.
Shang, H.M. 
Issue Date: 1-May-2003
Citation: Quan, C.,Tay, C.J.,Kang, X.,He, X.Y.,Shang, H.M. (2003-05-01). Shape measurement by use of liquid-crystal display fringe projection with two-step phase shifting. Applied Optics 42 (13) : 2329-2335. ScholarBank@NUS Repository.
Abstract: The use of an optical fringe projection method with two-step phase shifting for three-dimensional (3-D) shape measurement of small objects is described. In this method, sinusoidal linear fringes are projected onto an object's surface by a programmable liquid-crystal display (LCD) projector and a long-working-distance microscope (LWDM). The image of the fringe pattern is captured by another LWDM and a CCD camera and processed by a phase-shifting technique. Usually a minimum of three phase-shifted fringe patterns is necessary for extraction of the object shape. In this method, a new algorithm based on a two-step phase-shifting technique produces the 3-D object shape. Unlike in the conventional method, phase unwrapping is performed directly by use of an arccosine function without the need for a wrapped phase map. Hence, shape measurement can be speeded up greatly with this approach. A small coin is evaluated to demonstrate the validity of the proposed measurement method, and the experimental results are compared with those of the four-step phase-shifting method and the conventional mechanical stylus method. © 2003 Optical Society of America.
Source Title: Applied Optics
ISSN: 00036935
Appears in Collections:Staff Publications

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