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1 January 1987 Strategy For Polishing Several Mirrors To A Common Focal Length
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The Foucault test is a sensitive method of testing a curved mirror surface during the fabrication process. A skilled optician can readily interpret the results of the test and correct the surface accordingly. However, comparisons between different surfaces are more difficult. Fabricating several mirrors to the same focal length can be facilitated by a further quantification of the Foucault test. If h(r) is used to denote the deviation of the mirror surface from a parabola of focal length Fo, then the focal length F at a given radius r from the center of the mirror is given in terms of the derivative h'(r) by- F(r) = Fo 2Fo2 h'(r)/r The Foucault test measures F(r) - Fo and thus can be used to determine h'(r). By fitting a polynomial to hi(r) and integrating term by term, the deviation h(r) from the ideal surface can be determined. Using this knowledge of the surface figure, we have worked four 8-in diameter f/1.8 parabolas so as to bring them to a common focal length. One mirror was chosen as a reference and the focal lengths of the others were worked in the direction of its focal length. Often, the corrections suggested by the requirement that the focal length be changed were different from the corrections that would have been made to obtain the nearest parabola. The focal lengths of the final surfaces were the same to within ± 0.0005 inch (approximately one part in 30,000).
© (1987) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
C. K. Carniglia, D. G . Ewing, G. W. Flint, and J. W. Bender "Strategy For Polishing Several Mirrors To A Common Focal Length", Proc. SPIE 0818, Current Developments in Optical Engineering II, (1 January 1987);

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