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Proceedings Paper

Real-time optimal sensing strategies for active control of optical systems
Author(s): Suk-Min Moon; Leslie P. Fowler; Robert L. Clark; Eric H. Anderson
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Paper Abstract

The pointing and imaging performance of precision optical systems is degraded by disturbances on the system that create optical jitter. These disturbances can be caused by structural motion of optical components due to vibration sources that (1) originate within the optical system, (2) originate external to the system and are transmitted through the structural path in the environment, and (3) are air-induced vibrations from acoustic noise. Beam control systems can suppress optical jitter, and active control techniques can be used to extend performance by incorporating information from accelerometers, microphones, and other auxiliary sensors. In some applications, offline fixed gain controllers can be used to minimize jitter. However there are many applications in which a real-time adaptive control approach would yield improved optical performance. Often we would like the capability to adapt in real-time to a system which is time-varying or whose disturbances are non-stationary and hard to predict. In the presence of these harsh, ever-changing environments we would like to use every available tool to optimize performance. Improvements in control algorithms are important, but another potentially useful tool is a real-time adaptive control method employing optimal sensing strategies. In this approach, real-time updating of reference sensors is provided to minimize optical jitter. The technique selects an optimal subset of sensors to use as references from an array of possible sensor locations. The optimal, weighted reference sensor set is well correlated with the disturbance and when used with an adaptive control algorithm, results in improved line-of-sight jitter performance with less computational burden compared to a controller which uses multiple reference sensors. The proposed technique is applied to an experimental test bed in which multiple proof-mass actuators generate structural vibrations on a flexible plate. These vibrations are transmitted to an optical mirror mounted on the plate, resulting in optical jitter as measured by a position sensing detector. Accelerometers mounted on the plate are used to form the set of possible optimal reference sensors. Reduction of the structural vibration of optical components is attained using a fast steering mirror which results in a reduction of the corresponding jitter.

Paper Details

Date Published: 10 May 2007
PDF: 10 pages
Proc. SPIE 6569, Acquisition, Tracking, Pointing, and Laser Systems Technologies XXI, 65690R (10 May 2007); doi: 10.1117/12.719372
Show Author Affiliations
Suk-Min Moon, Duke Univ. (United States)
Leslie P. Fowler, CSA Engineering, Inc. (United States)
Robert L. Clark, Duke Univ. (United States)
Eric H. Anderson, CSA Engineering, Inc. (United States)

Published in SPIE Proceedings Vol. 6569:
Acquisition, Tracking, Pointing, and Laser Systems Technologies XXI
Steven L. Chodos; William E. Thompson, Editor(s)

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