Share Email Print
cover

Proceedings Paper

Empirical measurement of MEMS stroke saturation, with implications for woofer-tweeter architectures
Format Member Price Non-Member Price
PDF $14.40 $18.00
cover GOOD NEWS! Your organization subscribes to the SPIE Digital Library. You may be able to download this paper for free. Check Access

Paper Abstract

The Gemini Planet Imager (GPI) is currently in production for the Gemini Telescope in Chile. This instrument will directly image young jovian exoplanets, aided by a micro-electrical mechanical systems (MEMS) deformable mirror (DM). Boston Micromachines MEMS mirrors operate thousands of actuators to provide a well-sampled correction at high spatial frequencies. However, because MEMS stroke alone is insufficient to fully correct the atmosphere in the near-IR on an 8-meter telescope, a dual-mirror system is planned for GPI: The MEMS is used as a 'tweeter' to correct the higher spatial frequencies while a separate 'woofer' DM will be used to correct the lower frequencies. During operation at GPI, any saturated actuators would scatter starlight into the dark hole instead of allowing it to be removed coronagraphically; thus, stroke saturation on the MEMS is tolerated only at the 5-sigma level. In the Laboratory for Adaptive Optics, we test the ability of the MEMS to counter atmospheric turbulence. The MEMS shape is set to random iterations of woofer-corrected Kolmogorov phase screens with varying woofer sizes. We find that, for r0 = 10 cm, saturation decreases from several percent to a few tenths of a percent (∼3-sigma) when using a 100cm-pitch woofer. The MEMS we tested has 0.2 &mgr;m inter-actuator stroke for a 200V-range. Nonetheless, saturation (when it occurs) appears to be due to low-order peak-to-valley stroke even in the woofer-corrected case. Gemini characteristically has r0 = 15 cm, so future work includes extrapolating to find where the 5-sigma saturation level occurs.

Paper Details

Date Published: 16 July 2008
PDF: 12 pages
Proc. SPIE 7015, Adaptive Optics Systems, 70153N (16 July 2008); doi: 10.1117/12.788091
Show Author Affiliations
Katie M. Morzinski, National Science Foundation Ctr. for Adaptive Optics (United States)
UCO/Lick Observatory, Univ. of California/Santa Cruz (United States)
Bruce A. Macintosh, National Science Foundation Ctr. for Adaptive Optics (United States)
UCO/Lick Observatory, Univ. of California/Santa Cruz (United States)
Lawrence Livermore National Lab. (United States)
Daren Dillon, National Science Foundation Ctr. for Adaptive Optics (United States)
UCO/Lick Observatory, Univ. of California/Santa Cruz (United States)
Don Gavel, National Science Foundation Ctr. for Adaptive Optics (United States)
UCO/Lick Observatory, Univ. of California/Santa Cruz (United States)
Dave Palmer, National Science Foundation Ctr. for Adaptive Optics (United States)
Lawrence Livermore National Lab. (United States)
Andrew Norton, National Science Foundation Ctr. for Adaptive Optics (United States)
UCO/Lick Observatory, Univ. of California/Santa Cruz (United States)


Published in SPIE Proceedings Vol. 7015:
Adaptive Optics Systems
Norbert Hubin; Claire E. Max; Peter L. Wizinowich, Editor(s)

© SPIE. Terms of Use
Back to Top