Simultaneous interferometric optical figure characterizations for nominal optical flat and Dewar-window system at cryogenic temperatures

Dz-Hung Gwo

doi:10.1117/12.254143

14 October 1996 Simultaneous interferometric optical figure characterizations for nominal optical flat and Dewar-window system at cryogenic temperatures

Dz-Hung Gwo

Author Affiliations +

Proceedings Volume 2814, Cryogenic Optical Systems and Instruments VII; (1996) https://doi.org/10.1117/12.254143
Event: SPIE's 1996 International Symposium on Optical Science, Engineering, and Instrumentation, 1996, Denver, CO, United States

Abstract

In cryogenic optical-figure measurements for nominal optical flats, we in principle need a dewar-window system with the associated wavefront distortion calibrated for its actual temperature profile. Using traditional approach, this calibration would require a cryogenically calibrated reference flat, whose calibration on the other hand would need a calibrated window system not existing yet. Of course, we cannot reliably calculate the wave-front distortion either because of the following unknown profiles in the glass substrates such as temperature, temperature-dependent non-uniformity of the thermal expansion coefficient, refractive index, mechanical mounting strain, etc. To solve the problem, the author proposes a scheme to characterize and separate the tilt-independent wavefront distortion of the window system from that of the test piece in only one cooldown. The scheme involves interferometric phase map measurements for several lateral locations of the test piece shifted by a cryogenic X-Y translation stage. The data reduction scheme is described in detail.

Citation Download Citation

Dz-Hung Gwo "Simultaneous interferometric optical figure characterizations for nominal optical flat and Dewar-window system at cryogenic temperatures", Proc. SPIE 2814, Cryogenic Optical Systems and Instruments VII, (14 October 1996); https://doi.org/10.1117/12.254143

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