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Proceedings Paper

Measurement of steep aspheres: a step forward to nanometer accuracy
Author(s): Ingolf Weingaertner; Michael Schulz; Peter Thomsen-Schmidt; Clemens Elster
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Paper Abstract

It is a promising method for measuring steep aspheres and complex surfaces with nanometer and sub-nanometer accuracy to measure the curvature and to calculate the topography from it, since unlike slope and distance, the curvature is an intrinsic property of a surface and less insensitive to error influences. For the development of a measuring instrument based on the physical property of curvature, various topics have been investigated. The method described does not rely on external form references, and the errors of the scanning stages and the whole-body movement of the artifact have only little influence on the accuracy. In comparison to other measuring techniques, it is an advantageous feature of the curvature measuring technique that distance and angle between sensor and surface element can be controlled and kept constant during scanning as it is the curvature and not the distance or the slope which is the measurand. This leads to the result that, apart from the calibration of the curvature sensor, the whole system no longer suffers from first-and second-order errors. The uncertainty budget shows that nanometer accuracy is achievable.

Paper Details

Date Published: 10 December 2001
PDF: 10 pages
Proc. SPIE 4449, Optical Metrology Roadmap for the Semiconductor, Optical, and Data Storage Industries II, (10 December 2001); doi: 10.1117/12.450095
Show Author Affiliations
Ingolf Weingaertner, Physikalisch-Technische Bundesanstalt (Germany)
Michael Schulz, Physikalisch-Technische Bundesanstalt (Germany)
Peter Thomsen-Schmidt, Physikalisch-Technische Bundesanstalt (Germany)
Clemens Elster, Physikalisch-Technische Bundesanstalt (Germany)

Published in SPIE Proceedings Vol. 4449:
Optical Metrology Roadmap for the Semiconductor, Optical, and Data Storage Industries II
Angela Duparre; Bhanwar Singh, Editor(s)

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