The fabrication of a conic surface begins with the grinding of a best-fit sphere. The desired conic surface can then be obtained by further grinding with a subaperture tool. Finally, the surface is polished. Normally the best-fit sphere is chosen so as to minimize the second grinding step. However, this method tends to produce mid-spatial frequency errors near the edge of the surface and can cause errors in the paraxial radius of curvature. This paper presents an alternative method of calculating the initial sphere so as to avoid these errors. It requires more grinding time but far less time for polishing.
© 1999 Optical Society of America
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