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Proceedings Paper

Topography reconstruction of specular surfaces
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Paper Abstract

Specular surfaces are used in a wide variety of industrial and consumer products like varnished or chrome plated parts of car bodies, dies, molds or optical components. Shape deviations of these products usually reduce their quality regarding visual appearance and/or technical performance. One reliable method to inspect such surfaces is deflectometry. It can be employed to obtain highly accurate values representing the local curvature of the surfaces. In a deflectometric measuring system, a series of illumination patterns is reflected at the specular surface and is observed by a camera. The distortions of the patterns in the acquired images contain information about the shape of the surface. This information is suited for the detection and measurement of surface defects like bumps, dents and waviness with depths in the range of a few microns. However, without additional information about the distances between the camera and each observed surface point, a shape reconstruction is only possible in some special cases. Therefore, the reconstruction approach described in this paper uses data observed from at least two different camera positions. The data obtained is used separately to estimate the local surface curvature for each camera position. From the curvature values, the epipolar geometry for the different camera positions is recovered. Matching the curvature values along the epipolar lines yields an estimate of the 3d position of the corresponding surface points. With this additional information, the deflectometric gradient data can be integrated to represent the surface topography.

Paper Details

Date Published: 17 January 2005
PDF: 8 pages
Proc. SPIE 5665, Videometrics VIII, 566507 (17 January 2005); doi: 10.1117/12.587696
Show Author Affiliations
Soren Kammel, Univ. Karlsruhe (Germany)
Jan Horbach, Univ. Karlsruhe (Germany)

Published in SPIE Proceedings Vol. 5665:
Videometrics VIII
J.-Angelo Beraldin; Sabry F. El-Hakim; Armin Gruen; James S. Walton, Editor(s)

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