Passive compensation of gravity flexure in optical instruments

Edward A. Hileman; Jay Elias; Richard Joyce; Ronald Probst; Ming Liang; Earl Pearson

doi:10.1117/12.550466

29 September 2004 Passive compensation of gravity flexure in optical instruments

Edward A. Hileman, Jay Elias, Richard Joyce, Ronald Probst, Ming Liang, Earl Pearson

Proceedings Volume 5495, Astronomical Structures and Mechanisms Technology; (2004) https://doi.org/10.1117/12.550466
Event: SPIE Astronomical Telescopes + Instrumentation, 2004, Glasgow, United Kingdom

Abstract

We present case studies on the application of passive compensation in two large astronomical instruments: the Gemini Near Infrared Spectrograph (GNIRS), including actual performance, and the NOAO Extremely Wide Field Infrared Mosaic (NEWFIRM) camera. Image motion due to gravity flexure is a problem in large astronomical instruments. We present solutions for two different cases using passive mechanical compensation of the optical train. For the Gemini Near Infrared Spectrograph (GNIRS), articulation of a single sensitive optic is used. Adjustable cantilevered weights, designed to respond to specific gravity components, are employed to drive tilt flexures connected to the collimator mirror. An additional requirement is that cryocooler vibration must not dynamically excite this mirror. Performance testing of the complete instrument shows that image motion has been satisfactorily compensated. Some image blur due to dynamic excitation by the cryocoolers was noted. A successful damping scheme has been developed experimentally. For the NOAO Extremely Wide Field Infrared Mosaic camera (NEWFIRM), the entire optical support structure is mechanically tuned to deflect and rotate precisely as a rigid body relative to the telescope focal plane. This causes the optical train to remain pointed at a fixed position in the focal plane, minimizing image motion on the science detector. This instrument is still in fabrication.

Citation Download Citation

Edward A. Hileman, Jay Elias, Richard Joyce, Ronald Probst, Ming Liang, and Earl Pearson "Passive compensation of gravity flexure in optical instruments", Proc. SPIE 5495, Astronomical Structures and Mechanisms Technology, (29 September 2004); https://doi.org/10.1117/12.550466

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