Interferometric validation of image-based wavefront sensing for NGST

Joseph Jacob Green; David C. Redding; Yuri Beregovski; Andrew E. Lowman; Catherine Mayumi Ohara

doi:10.1117/12.461157

5 March 2003 Interferometric validation of image-based wave front sensing for NGST

Joseph Jacob Green, David C. Redding, Yuri Beregovski, Andrew E. Lowman, Catherine Mayumi Ohara

Proceedings Volume 4850, IR Space Telescopes and Instruments; (2003) https://doi.org/10.1117/12.461157
Event: Astronomical Telescopes and Instrumentation, 2002, Waikoloa, Hawai'i, United States

Abstract

To achieve and maintain excellent imaging performance, the Next Generation Space Telescope (NGST) will employ image-based phase retrieval methods to control its segmented primary mirror. In this paper, we present the experimental validation of a focus-diverse wave front sensing (WFS) algorithm with comparative interferometric measurements of a perturbed test mirror. Using sets of defocused point-spread functions measured with the NGST phase retrieval camera, we estimate the aberrations of the test optic in a perturbed and unperturbed state. Interleaved with the focus-diverse sets, we measure the surface figure of the mirror using a ZYGO interferometer. After briefly reviewing the basic WFS algorithm and describing the experimental setup, we show that we can obtain agreement that is better than 1/100th of a wave rms in the difference of the wave front estimates obtained in the perturbed and unperturbed states. Although this experiment does not establish the errors that are solely attributable to our WFS approach, it nevertheless validates the accuracy of our image-based methods for NGST, demonstrating that they are generally competitive with standard industrial optical metrology instruments.

Citation Download Citation

Joseph Jacob Green, David C. Redding, Yuri Beregovski, Andrew E. Lowman, and Catherine Mayumi Ohara "Interferometric validation of image-based wave front sensing for NGST", Proc. SPIE 4850, IR Space Telescopes and Instruments, (5 March 2003); https://doi.org/10.1117/12.461157

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