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Proceedings Paper

Interferometric measurement of highly accurate flat surfaces
Author(s): J. Liebl; H. Linthe; S. Sitzberger; R. Rascher
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Paper Abstract

The most important part in manufacturing precision optics is a reliable measurement procedure which provides results a few times more accurate than the quality to be produced. In general two specific values are important, the repeatability of several measurements which are done in a row and the absolute accuracy which is mostly defined by the systematical error of the measurement device. The repeatability can be improved relatively simple, by increasing the number of measurements and a following averaging step. To increase the absolute accuracy of a measurement device in the field of precision optics is far more challenging.

In this paper several interferometer absolute testing methods to measure flat surfaces are compared. The main objective was to name a value for the achievable accuracy. Therefor four different methods were analyzed:
    1. The three flat test, a method which is already used several decades to determine the quality of a flat surface. As a result, two absolute measured profiles, horizontal and vertical, can be calculated.
    2. The multi rotation test, an extension of the classical three flat test. The big advantage of this method is a fully three dimensional map of the systematical error.
    3. The systematical error calculated by the SSI-A. Hereby several subapertures are measured over the whole surface. The redundant information’s of the overlapping regions can be used to calculate the systematical error of the system.
    4. The rotation of the transmission flat relatively to the interferometer. Thereby the rotation unsymmetrical errors can be calculated and subtracted.

Paper Details

Date Published: 30 June 2016
PDF: 6 pages
Proc. SPIE 10009, Third European Seminar on Precision Optics Manufacturing, 100090X (30 June 2016); doi: 10.1117/12.2235525
Show Author Affiliations
J. Liebl, Deggendorf Institute of Technology (Germany)
H. Linthe, Deggendorf Institute of Technology (Germany)
S. Sitzberger, Deggendorf Institute of Technology (Germany)
R. Rascher, Deggendorf Institute of Technology (Germany)

Published in SPIE Proceedings Vol. 10009:
Third European Seminar on Precision Optics Manufacturing
Rolf Rascher; Oliver Fähnle; Christine Wünsche; Christian Schopf, Editor(s)

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