NASA TN D-6626
John M. Jerke, Robert J. Platt (Jr.), United States. National Aeronautics and Space Administration, Langley Research Center
National Aeronautics and Space Administration, 1972 - Optical instruments - 23 pages
The effects of aging, vacuum exposure, and thermal cycling on the dimensional stability of mirror-substrate materials, fused silica, Cer-Vit, Kanigen-coated beryllium, polycrystalline silicon, and U.L.E. fused silica were investigated. A multiple-beam interferometer was used to determine nonrecoverable surface-shape changes of the 12.7-cm-diameter mirrors with substrates of these materials. Thermal cycling and aging in vacuum produced the largest changes, but only a few were as large as 1/30 wavelength, where the wavelength was 632.8 nm.
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1/40 wavelength Aging in vacuum automated analysis technique beryllium-Kanigen mirror candidate mirror-substrate materials Changes shown comparison of interferograms contour map cooling cycles Corning Glass determined from interferograms dry ice effects of aging environmental test ferograms figure changes Fused silica X/40 G G G H V H heat cycles horizontal interferograms indicated interfero interferogram changes intermediate aging periods Kanigen coating Kanigen-coated beryllium Langley Research Center less than X/40 magnesium fluoride map of figure Maximum fringe changes mirror and reference mirror edge mirror figure mirror interferograms mirror surface mirror-figure changes multiple-beam interferometer nonrecoverable changes optical-path difference polycrystalline silicon reference flat room temperature root-mean-square set of heat set of mirrors set of thermal shown in figures shown were determined silicon mirror silicon oxide substrate materials test mirrors Test-mirror substrate thermal cycling thermal-cycling tests Thermocouples U.L.E. fused silica U.L.E. fused-silica mirror units of wavelength vacuum exposure vertical and horizontal vertical interferograms X/40 Cycles