Defense Tech Briefs - Mirror-Steering System Eliminates Vibration in Optical Devices

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Mirror-Steering System Eliminates Vibration in Optical Devices

Dec 01 2007

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For optical systems used in communications and instrumentation applications in space and on the ground, eliminating vibration can be a difficult task. Left Hand Design Corp. (LHDC, Boulder County, CO) received Missile Defense Agency (MDA) funding through a 2002 SBIR Phase II award to develop a suite of optical steering devices designed to improve the vibration immunity of optical systems, allowing them to track moving targets with greater accuracy.

LHDC developed an enhanced fine-steering mirror or fast-steering mirror (FSM). Missile interceptor seekers must rapidly point their optical systems at different targets in a dense cluster, a sufficient challenge without the added problem of vibration caused by other moving components on the vehicle. This task requires a mirror that can be positioned rapidly and precisely. The design improvements LHDC successfully developed for this project can provide benefits for these and a wide variety of commercial and aerospace applications, including image motion compensation for orbiting Earth observation, ground- and space-based astronomy, video cameras, industrial inspection, laser communications, laser surgery, and photolithography

How it Works

LHDC’s system for steering optics such as mirrors could be used in aerospace applications, laser communications, and industrial inspection.

Optics in an orbiting telescope can be pointed using a two-axis gimbal and by adjusting the satellite’s attitude (its orientation in space). These methods are sufficient for coarse and low-speed positioning, but they cannot provide continuous high-speed compensation in the presence of spacecraft platform vibrations. Such vibrations introduce disabling jitter in the optical signal, but FSMs come to the rescue with their capability of rapidly and accurately stabilizing the line of sight.

The mirror “payload” of the FSM system is typically 15 to 300 millimeters in diameter. An optical-tracking detector and/or inertial sensor senses instantaneous deviations from the ideal pointing angle and provides feedback to motors that rapidly adjust the position of the mirror, bringing the optical path back into precise alignment. The system design is critical, requiring materials with the necessary stiffness, lightness, and thermalexpansion properties, further complicated by stresses introduced when the mirror is attached to its mount. For this reason, LHDC offers mirrors fabricated from a variety of materials chosen for the mission. The company’s FSMs are currently flying in a number of military aircraft as well.

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