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Proceedings Paper

Feedback stabilized deformable membrane mirrors for focus control
Author(s): Sarah J. Lukes; Phillip A. Himmer; Eric J. Moog; Steven R. Shaw; David L. Dickensheets
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Paper Abstract

This paper describes a method to extend the range of motion of a deformable, continuous membrane mirror beyond the limit of open-loop electrostatic instability through the use of a feedback control scheme. The feedback scheme is based on capacitive sensing of the mirror. The sensing is achieved by coupling the actuation electrodes to a ring oscillator. We use a differential technique, where the frequency of the coupled oscillator is compared to a reference ring oscillator. Analysis of the system using a simplified parallel-plate model shows that the range of stable deflection depends on the dynamics of the device and control circuitry, and suggests that stable full-gap displacement can be achieved under certain conditions. Experimental results are provided, showing stable closed-loop deflection of our silicon nitride test device to 61% of the air gap, consistent with the predictions of our model.

Paper Details

Date Published: 23 February 2009
PDF: 8 pages
Proc. SPIE 7208, MOEMS and Miniaturized Systems VIII, 72080Q (23 February 2009); doi: 10.1117/12.812338
Show Author Affiliations
Sarah J. Lukes, Montana State Univ. (United States)
Phillip A. Himmer, Montana State Univ. (United States)
Eric J. Moog, Montana State Univ. (United States)
Steven R. Shaw, Montana State Univ. (United States)
David L. Dickensheets, Montana State Univ. (United States)

Published in SPIE Proceedings Vol. 7208:
MOEMS and Miniaturized Systems VIII
David L. Dickensheets; Harald Schenk; Wibool Piyawattanametha, Editor(s)

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