21 December 1998 Multiwavelength heterodyne array system for large space optics control
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Large, lightweight optical mirrors for space applications will require systems for controlling the gross aspects of the mirror surface figure. We have developed an autonomously operating wavefront measurement system based on dual- wavelength heterodyne distance measurement techniques combined with heterodyne array imaging. A key feature of the technique is variable optical path length measurement sensitivity that allows the system to measure surface figure errors ranging from thousands of wavelengths down to fractions of a wavelength. Automatic sensitivity tuning combined with completely digital phase measurement over the entire surface allows the integration of this device in automated sensing and optical correction schemes. It is particularly suited for the measurement and control of spatially and temporally variable optical surfaces of the kind that would be found in a space- based adaptive optics system. In this paper we demonstrate aspects of the automated super-heterodyne system on an optical surface with surface profile structure height that varies from micron to mm sized features. We describe the hardware and software design of the heterodyne based measurement system that enable it to choose the appropriate synthetic wavelength to measure different areas of the surface profile. Spatial processing methods are discussed that allow the system to merge segments of large scale images that have been measured at different synthetic wavelengths.
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Lenore J. McMackin, David G. Voelz, Matthew P. Fetrow, Harold D. McIntire, Kenneth P. Bishop, Mervyn J. Kellum, "Multiwavelength heterodyne array system for large space optics control", Proc. SPIE 3498, Sensors, Systems, and Next-Generation Satellites II, (21 December 1998); doi: 10.1117/12.333657; https://doi.org/10.1117/12.333657

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