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Proceedings Paper

Broadband interferometer for measuring transmitted wavefronts of optical band pass filters for Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS)
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Paper Abstract

The transmitted wavefronts of optical filters for he Hubble Space Telescope (HST) advanced camera for surveys (ACS) are characterized using the Wildly and Openly Modified Broadband Achromatic Twyman Green (WOMBAT) Interferometer developed in the NASA/GSFC Optics Branch's Diffraction Grating Evaluation Facility. Because only four of thirty-three of ACS's optical bandpass filters transmit the 633 nm light of most commercial interferometers, a broadband interferometer is required to verify specified transmitted wavefront of ACS filters. WOMBAT's design is a hybrid of the BAT2 interferometer developed for JPL used for HST wide field and planetary camera II filters and a WYKO 400 phase shifting interferometer. It includes a broadband light source, monochromator, off-axis, parabolic collimating and camera mirrors, an aluminum-coated fused silica beamsplitter, flat retroreflecting mirrors for the test and reference arms, and a UV-sensitive CCD camera. An outboarded, piezo-electric phase shifter holds the flat mirror in the interferometer's reference arm. The interferometer is calibrated through interaction between the WYKO system's software and WOMBAT hardware for the test wavelength of light entering the beamsplitter. Phase-shifted interferograms of the filter mounted in the tests arm are analyzed using WYKO's vision for optical testing software. Filters as large as 90 mm in diameter have been measured over a wavelength range from 200 to 1100 nm with a ACS fixed bandpass and spatially-variable bandpass filters for a variety of wavelengths.

Paper Details

Date Published: 28 August 1998
PDF: 12 pages
Proc. SPIE 3356, Space Telescopes and Instruments V, (28 August 1998); doi: 10.1117/12.324539
Show Author Affiliations
Rene A. Boucarut, NASA Goddard Space Flight Ctr. (United States)
Douglas B. Leviton, NASA Goddard Space Flight Ctr. (United States)

Published in SPIE Proceedings Vol. 3356:
Space Telescopes and Instruments V
Pierre Y. Bely; James B. Breckinridge, Editor(s)

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