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Proceedings Paper

Using linear variable differential transformers and ultrasonic transducers to measure flatness and parallelism for NIF optics
Author(s): Richard J. Boland
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Paper Abstract

Measuring surface figure of large ground surfaces has been done with infrared interferometers or by means of local measurements with a spherometer to obtain a general shape of an optical surface. This paper describes a straightforward technique to obtain surface figure of plano parallel optics with an array of transducers referenced to an optical flat. The instrument utilizes 16 linear variable differential transformers (LVDT) and 16 ultrasonic transducers (UT) to measure surface figure of side 1, side 2 and the wedge in one measurement setup. The transducers are setup in a 4 X 4 array, for a total of 32 in one fixture. The data is acquired via a PC acquiring data through serial ports and an A/D card. The two 4 X 4 data sets are fit to the first ten Zernikes using the method of least squares. The data is displayed with 3D graphics to obtain a view of the optical surfaces. By using 14 bit digital LVDT's and employing the cross correlation technique for acoustic signal processing a system accuracy of plus or minus 1.0 micrometer for the LVDT array and plus or minus 2.75 micrometer for the UT array has been achieved.

Paper Details

Date Published: 11 November 1999
PDF: 9 pages
Proc. SPIE 3782, Optical Manufacturing and Testing III, (11 November 1999); doi: 10.1117/12.369197
Show Author Affiliations
Richard J. Boland, Zygo Corp. (United States)

Published in SPIE Proceedings Vol. 3782:
Optical Manufacturing and Testing III
H. Philip Stahl, Editor(s)

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