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Proceedings Paper

Self-referencing calibration method for transmission spheres in Fizeau interferometry
Author(s): Jan Burke; David S. Wu
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Paper Abstract

The calibration of reference surfaces becomes important in interferometry whenever the tolerances for the tested component are comparable to the imperfections of the reference surface itself. To achieve measurement accuracy better than the reference surface, its errors must be characterised and subtracted from the measurement result. We propose a rapid and simple technique utilising a flat mirror in the focus of the converging test wavefront and a partial occlusion of the test beam, to implement a double-pass self-calibration of the reference surface. Stitching together three or more measurements, with the beam stop appropriately rotated, yields the full-aperture calibration data. The method cannot detect point-antisymmetric errors, but common errors in reference spheres, such as spherical aberration and astigmatism, are point-symmetric and should still be adequately captured. For calibrating spherical surfaces in Fizeau interferometry, a ball of good sphericity can be measured against the reference surface in a number of random orientations. This averages out the errors of the ball and converges toward the stationary error in the reference sphere. Depending on the quality of the ball and the desired uncertainty, the number of orientations required can be large (50-100), which is laborious and time-consuming. We compare the performance of the new technique with the ball-averaging method and the so-called "cat's eye" method to assess the practical trade-offs involved.

Paper Details

Date Published: 2 August 2010
PDF: 11 pages
Proc. SPIE 7790, Interferometry XV: Techniques and Analysis, 77900F (2 August 2010); doi: 10.1117/12.860911
Show Author Affiliations
Jan Burke, Commonwealth Scientific and Industrial Research Organisation (Australia)
David S. Wu, The Univ. of Sydney (Australia)

Published in SPIE Proceedings Vol. 7790:
Interferometry XV: Techniques and Analysis
Catherine E. Towers; Joanna Schmit; Katherine Creath, Editor(s)

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