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Proceedings Paper

Phase-shifting digital projection system for surface profile measurement
Author(s): Chi-Shing Chan; Anand Krishna Asundi
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Paper Abstract

In many industrial applications, non-contact and non-destructive surface profile measurements are frequently required. The projection grid method is one of the available methods that fulfills the above needs. It is based on the principle of triangulation, hence simple in computation. It has the advantage of full field measurement without any scanning optics. To increase the sensitivity, phase shifting techniques are incorporated. It improves the sensitivity to 1/100th of a fringe. However an accurate positioning device is required to shift the grating. Traditional systems use mechanical devices, for example a translation stage, to perform the shifting. Due to hysteresis, backlash and wear, inaccurate shift such as unequal or incomplete shift often results leading to undesirable errors. This paper describes a phase shifting digital projection system that solves the above problem. The conventional physical grating is replaced by a computer generated grating. A computer generated grating is projected onto the test object via an LCD projector. Complete shifting of grating is performed by computer software. Besides the system is very flexible. It has the advantage of variable type and pitch of grating. In this paper, the system hardware is described in detail, followed by a performance analysis and experiments.

Paper Details

Date Published: 13 October 1994
PDF: 9 pages
Proc. SPIE 2354, Intelligent Robots and Computer Vision XIII: 3D Vision, Product Inspection, and Active Vision, (13 October 1994); doi: 10.1117/12.189113
Show Author Affiliations
Chi-Shing Chan, Univ. of Hong Kong (Hong Kong China)
Anand Krishna Asundi, Univ. of Hong Kong (Hong Kong China)

Published in SPIE Proceedings Vol. 2354:
Intelligent Robots and Computer Vision XIII: 3D Vision, Product Inspection, and Active Vision
David P. Casasent, Editor(s)

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