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Proceedings Paper

Three-lambda metrology
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Paper Abstract

The state-of-the-art technique for measuring discontinuous surface profiles, e.g. diffractive optical elements (DOE) is white-light interferometry. Compared to single wavelength phase-shifting interferometry conventional white-light-interferometry is rather slow, because the number of frames to be evaluated is about ten times greater than in phase-shifting-interferometry. Therefore white-light-interferometry needs more memory capacity and computer time. Single wavelength phase-shifting interferometry cannot be used for the mentioned task since the order of the interference fringes cannot be determined. But if three wavelengths, e.g. a red, a green, and a blue one are used which preferably have no common factor it is possible to determine the interference order of the fringes or the absolute optical path difference (OPD) of the interferometer. The interference patterns are simultaneously recorded by a color CCD-camera having 3 separate chips. The OPD is calculated for each pixel from the three phase values mod 2π . The algorithms used and experimental results will be presented.

Paper Details

Date Published: 20 June 2002
PDF: 8 pages
Proc. SPIE 4777, Interferometry XI: Techniques and Analysis, (20 June 2002); doi: 10.1117/12.472219
Show Author Affiliations
Andreas Pfoertner, Friedrich-Alexander Univ. Erlangen-Nuernberg (Germany)
Johannes Schwider, Friedrich-Alexander Univ. Erlangen-Nuernberg (Germany)

Published in SPIE Proceedings Vol. 4777:
Interferometry XI: Techniques and Analysis
Katherine Creath; Joanna Schmit, Editor(s)

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