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 AmericaFull Article | PDF Article
Cho Jui Tay, Madhuri Thakur, and Chenggen Quan
Appl. Opt. 44(8) 1393-1400 (2005)
Cho Jui Tay, Chenggen Quan, and Lujie Chen
Appl. Opt. 44(8) 1401-1409 (2005)
Madhuri Thakur, Cho Jui Tay, and Chenggen Quan
Appl. Opt. 44(13) 2541-2545 (2005)