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Proceedings Paper

CGH-LUPI interferometer for aspheric figure metrology
Author(s): Steven M. Arnold; Andrew P. Stuart; Lubomir Koudelka
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Paper Abstract

We have designed a nd built a phase-measuring LUPI interferometer to use pre-aligned custom CGH nulls for high accuracy figure metrology of deep aspherics. The CGH nulls operate in double pass, first producing an aspheric test wavefront and then recollimating the return wavefront. This eliminates any need to locate the CGH at an image of the test pupil THe CGH is common to both test and reference paths, allowing the use of photomask quality substrates. Tho enable the CGH-LUPI to test a wider variety of aspheres, we have designed and built a set of 100 mm aperture accessory optics for use in combination with CGH nulls. These accessory optics consist of five singles, each approximately F/3, which may be kinematically stacked in numerous combinations and permutations to produce test wavefronts ranging from nearly collimated to F/0.75 A CGH null compensates for asphericity of the test optic and design aberrations of the accessory optics. The interferometer and accessory optic designs permit independent verification of all aspects of system accuracy and calibration without the need for disassembly. Designing a custom CGH null involves raytracing the accessory optics but not the interferometer mainframe optics. Depending on the phase measuring algorithm selected, known system aberrations due to manufacturing tolerances may be software compensated in real time.

Paper Details

Date Published: 1 November 1997
PDF: 8 pages
Proc. SPIE 3134, Optical Manufacturing and Testing II, (1 November 1997); doi: 10.1117/12.295152
Show Author Affiliations
Steven M. Arnold, Diffraction International Ltd. (United States)
Andrew P. Stuart, Diffraction International Ltd. (United States)
Lubomir Koudelka, Promet International Inc. (United States)

Published in SPIE Proceedings Vol. 3134:
Optical Manufacturing and Testing II
H. Philip Stahl, Editor(s)

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