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Proceedings Paper

Sensitivity analysis of tilted-wave interferometer asphere measurements using virtual experiments
Author(s): Ines Fortmeier; Manuel Stavridis; Axel Wiegmann; Michael Schulz; Goran Baer; Christof Pruss; Wolfgang Osten; Clemens Elster
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Paper Abstract

The tilted-wave interferometer (TWI) was recently developed by the University of Stuttgart for the high-accuracy measurement of aspheres and freeform surfaces. The system works in a non-null measurement fashion and si­ multaneously uses several test beams with different tilts. Reconstruction of the specimen under test from TWI measurements is challenging and in order to correctly separate the real surface topography from systematic aberrations, the employed interferometer needs to be characterized. This characterization, as well as the recon­ struction of the specimen from TWI measurements, requires sophisticated data analysis procedures including ray tracing and the solution of an inverse problem. A simulation environment was developed at the Physikalisch-Technische Bundesanstalt (PTB) in order to inves­ tigate the accuracy and stability of TWI systems, and to explore possibilities and limitations of this promising measurement technique. Virtual experiments were carried out to quantify the sensitivity of the results with respect to the assumed linearity in the reconstruction procedure, positioning errors, and measurement noise. Our first results suggest that the mathematical TWI reconstruction technique basically allows highly accurate measurements with uncertainties down to a few nanometers, provided that calibration errors of the optical sys­ tems are kept small. The stability of the results and their accuracy can, however, depend significantly on the particular surface of the specimen and on the choice of experimental settings.

Paper Details

Date Published: 13 May 2013
PDF: 12 pages
Proc. SPIE 8789, Modeling Aspects in Optical Metrology IV, 878907 (13 May 2013); doi: 10.1117/12.2019986
Show Author Affiliations
Ines Fortmeier, Physikalisch-Technische Bundesanstalt (Germany)
Manuel Stavridis, Physikalisch-Technische Bundesanstalt (Germany)
Axel Wiegmann, Physikalisch-Technische Bundesanstalt (Germany)
Michael Schulz, Physikalisch-Technische Bundesanstalt (Germany)
Goran Baer, Univ. Stuttgart (Germany)
Christof Pruss, Univ. Stuttgart (Germany)
Wolfgang Osten, Univ. Stuttgart (Germany)
Clemens Elster, Physikalisch-Technische Bundesanstalt (Germany)


Published in SPIE Proceedings Vol. 8789:
Modeling Aspects in Optical Metrology IV
Bernd Bodermann; Karsten Frenner; Richard M. Silver, Editor(s)

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