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Proceedings Paper

Practical aspects of curvature detection for LACS free-form measuring systems
Author(s): Michael Schulz; Joachim Gerhardt; Clemens Elster
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Paper Abstract

For the production of aspheres and free-form surfaces, high-accuracy and flexible measurement techniques are necessary. The Large Area Curvature Scanning (LACS) method can be used to measure the surface form of arbitrary smooth surfaces with high accuracy. The curvature values of the surface elements along a scan line are captured by a curvature sensor and from these values the form is calculated. The curvature sensor typically is a small interferometer with an aperture of some millimeter. From a model fit to the measured interferogram, the local surface patch and the local curvature value are extracted. Determining the curvature values from the captured interferograms with high accuracy is a challenging task and requires some kind of intelligent procedures for defect recognition and for the choice of matched surface models. Several aspects of these problems are discussed. Examples of measured surfaces are shown. Special emphasis is laid on the measuring speed of the LACS system, which is mainly determined by the speed of the curvature evaluation procedure, as this is important for the use as an in-situ measurement system integrated into production systems.

Paper Details

Date Published: 10 September 2004
PDF: 8 pages
Proc. SPIE 5457, Optical Metrology in Production Engineering, (10 September 2004); doi: 10.1117/12.545498
Show Author Affiliations
Michael Schulz, Physikalisch-Technische Bundesanstalt (Germany)
Joachim Gerhardt, Physikalisch-Technische Bundesanstalt (Germany)
Clemens Elster, Physikalisch-Technische Bundesanstalt (Germany)

Published in SPIE Proceedings Vol. 5457:
Optical Metrology in Production Engineering
Wolfgang Osten; Mitsuo Takeda, Editor(s)

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