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Proceedings Paper

Automated optimization of measurement setups for the inspection of specular surfaces
Author(s): Soeren Kammel
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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 or molds. Defects of these parts reduce the quality regarding their visual appearance and/or their technical performance. Even defects that are only about 1 micrometer deep can lead to a rejection during quality control. Deflectometric techniques are an adequate approach to recognize and measure defects on specular surfaces, because the principle of measurement of these methods mimics the behavior of a human observer inspecting the surface. With these methods, the specular object is considered as a part of the optical system. Not the object itself but the surrounding that is reflected by the specular surface is observed in order to obtain information about the object. This technique has proven sensitive for slope and topography measurement. Inherited from the principle of measurement, especially surface parts with high curvature need a special illumination which surrounds the object under inspection to guarantee that light from any direction is reflected onto the sensor. Thus the design of a specific measurement setup requires a substantial engineering effort. To avoid the time consuming process of building, testing and redesigning the measurement setup, a system to simulate and automatically optimize the setup has been developed. Based on CAD data of the object under inspection and a model of the optical system, favorable realizations of the shape, the position and the pattern of the lighting device are determined. In addition, optimization of other system parameters, such as object position and distance relative to the camera, is performed. Finally, constraints are imposed to ascertain the feasibility of illumination system construction.

Paper Details

Date Published: 11 February 2002
PDF: 8 pages
Proc. SPIE 4567, Machine Vision and Three-Dimensional Imaging Systems for Inspection and Metrology II, (11 February 2002); doi: 10.1117/12.455257
Show Author Affiliations
Soeren Kammel, Univ. Karlsruhe Technische Hochschule (Germany)

Published in SPIE Proceedings Vol. 4567:
Machine Vision and Three-Dimensional Imaging Systems for Inspection and Metrology II
Kevin G. Harding; John W. V. Miller, Editor(s)

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