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Proceedings Paper

Phase measuring deflectometry: a new approach to measure specular free-form surfaces
Author(s): Markus C. Knauer; Jurgen Kaminski; Gerd Hausler
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Paper Abstract

We present a new method to measure specular free-form surfaces within seconds. We call the measuring principle `Phase Measuring Deflectometry' (PMD). With a stereo based enhancement of PMD we are able to measure both the height and the slope of the surface. The basic principle is to project sinusoidal fringe patterns onto a screen located remotely from the surface under test and to observe the fringe patterns reflected via the surface. Any slope variations of the surface lead to distortions of the patterns. Using well-known phase-shift algorithms, we can precisely measure these distortions and thus calculate the surface normal in each pixel. We will deduce the method's diffraction-theoretical limits and explain how to reach them. A major challenge is the necessary calibration. We solved this task by combining various photogrammetric methods. We reach a repeatability of the local slope down to a few arc seconds and an absolute accuracy of a few arc minutes. One important field of application is the measurement of the local curvature of progressive eyeglass lenses. We will present experimental results and compare these results with the theoretical limits.

Paper Details

Date Published: 10 September 2004
PDF: 11 pages
Proc. SPIE 5457, Optical Metrology in Production Engineering, (10 September 2004); doi: 10.1117/12.545704
Show Author Affiliations
Markus C. Knauer, Friedrich-Alexander-Univ. Erlangen-Nurnberg (Germany)
Jurgen Kaminski, Friedrich-Alexander-Univ. Erlangen-Nurnberg (Germany)
Gerd Hausler, Friedrich-Alexander-Univ. Erlangen-Nurnberg (Germany)


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

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