Precision mechanisms for optical alignments at cryogenic temperatures

Leonard V. LaCroix; Bonnie S. Smietanowska; James P. Campbell; Robert M. Yoshikawa; Ken M. Morgan

doi:10.1117/12.23057

1 November 1990 Precision mechanisms for optical alignments at cryogenic temperatures

Leonard V. LaCroix, Bonnie S. Smietanowska, James P. Campbell, Robert M. Yoshikawa, Ken M. Morgan

Proceedings Volume 1340, Cryogenic Optical Systems and Instruments IV; (1990) https://doi.org/10.1117/12.23057
Event: 34th Annual International Technical Symposium on Optical and Optoelectronic Applied Science and Engineering, 1990, San Diego, CA, United States

Abstract

The Lockheed Sensor Test Facility, located in Sunnyvale, California, is a state-of-the-art LWIR sensor calibration resource designed to calibrate strategic seekers against a simulated exoatmospheric optical background. Increasingly accurate and sophisticated seeker technology has created a demand for improved performance in test equipment, particularly in the area of cryogenic optical systems. Diffraction-limited optics and sub-arcsecond pointing have become the norm rather than the exception in these systems. This paper chronicles the two-year development of several precision mechanisms for use in cryogenic environments to 20 K at pressures below 1 microtorr. The Lockheed mechanism development is highlighted by the successful adaptation of traditional mechanism design principles to the cryogenic environment through the judicious selection of materials, lubricants and electromechanical devices, and the appropriate use of both open- and closed-loop controls. All of the mechanisms developed are associated with the 500-inch effective focal length, eccentric pupil Ritchey-Chretien collimator which forms the basis of the Lockheed seeker calibration approach. Although fundamentally athermal in design, this collimator has traditionally exhibited unacceptable warm-to-cold alignment variations. This phenomenon has been precluded through the use of a precision, six-degree-of-freedom refocusing mechanism which allows the in situ positioning of the collimator's secondary mirror. Together with two precision scan mirrors and their associated positioning mechanisms, the optical performance of the system at operating temperatures and pressures is assured. A source select mirror and its associated drive mechanism has been completely redesigned to provide the accurate positioning of several LWIR radiometric sources at the collimator prime focus.

Citation Download Citation

Leonard V. LaCroix, Bonnie S. Smietanowska, James P. Campbell, Robert M. Yoshikawa, and Ken M. Morgan "Precision mechanisms for optical alignments at cryogenic temperatures", Proc. SPIE 1340, Cryogenic Optical Systems and Instruments IV, (1 November 1990); https://doi.org/10.1117/12.23057

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