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Proceedings Paper

Complete sub-aperture pre-polishing and finishing solution to improve speed and determinism in asphere manufacture
Author(s): Paul Dumas; Christopher Hall; Bob Hallock; Marc Tricard
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Paper Abstract

There are four fundamental steps to precision glass aspheric manufacturing: 1) grinding - to generate the rough shape, 2) pre-polishing - to remove subsurface damage and smooth grinding residuals, 3) metrology - to quantify surface figure errors and 4) finishing - to reach final figure and roughness specification. The aspheric pre-polish step is currently the least deterministic process, as conventional sub-aperture tools (e.g. pitch, polyurethane pad) inherently have removal rate variation due to tool misfit, pad wear, or slurry variation over time. This limits the final figure accuracy achievable or at a minimum, leads to significant unpredictability in cycle time. Magnetorheological Finishing (MRF(R)) offers a very deterministic finishing process, but is limited in its ability to smooth certain spatial frequencies. In this paper, we present a complete polishing process (pre-polishing + finishing) that utilizes a novel combination of MRF and conventional small-tool pitch polishing. This combined approach leverages the strengths of both processes, providing a fast, deterministic, scalable aspheric finishing process to compliment existing grinding technology. Results for a 300 mm rectangular aperture, off-axis section will be presented showing final peak-to-valley quality of better than twentieth wave.

Paper Details

Date Published: 14 September 2007
PDF: 11 pages
Proc. SPIE 6671, Optical Manufacturing and Testing VII, 667111 (14 September 2007); doi: 10.1117/12.734684
Show Author Affiliations
Paul Dumas, QED Technologies International (United States)
Christopher Hall, QED Technologies International (United States)
Bob Hallock, QED Technologies International (United States)
Marc Tricard, QED Technologies International (United States)


Published in SPIE Proceedings Vol. 6671:
Optical Manufacturing and Testing VII
James H. Burge; Oliver W. Faehnle; Ray Williamson, Editor(s)

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