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Proceedings Paper

Recent advanced in sub-aperture approaches to finishing and metrology
Author(s): Marc Tricard; Paul Dumas; Greg Forbes; Mike DeMarco
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Paper Abstract

This paper summarizes some of latest developments by QED Technologies (QED) in the field of high-precision polishing and metrology. Magneto-Rheological Finishing (MRF) is a deterministic sub-aperture polishing process that overcomes many of the fundamental limitations of traditional finishing. The MR fluid forms a polishing tool that is perfectly conformal and therefore can polish a variety of shapes, including flats, spheres, aspheres, prisms, and cylinders, with round or non-round apertures. Over the past several years, QED's Q22 family of polishing platforms, based on the MRF process, have demonstrated the ability to produce optical surfaces with accuracies better than 30 nm peak-to-valley (PV) and surface micro-roughness less than 0.5 nm rms on an ever-widening variety of optical glass, single crystal, and glass-ceramic materials. The MRF process facilitates the correction of the transmitted wavefront of single elements and/or entire systems, as well as enabling the inducement of specific desired wavefront characteristics (i.e., other than making surfaces perfectly flat or spherical), which is beneficial for applications such as phase correction or other freeform applications. QED's Sub-aperture Stitching Interferometer (SSI) complements MRF by extending the effective aperture, accuracy, resolution, and dynamic range of a phase-shifting interferometer. This workstation performs automated sub-aperture stitching measurements of spheres, flats, and mild aspheres. It combines a six-axis precision stage system, a commercial Fizeau interferometer, and specially developed software that automates measurement design, data acquisition, and the reconstruction of the full-aperture map of figure error. Aside from the correction of sub-aperture placement errors (such as tilts, optical power, and registration effects), the SSI software also accounts for reference-wave error, distortion, and other aberrations in the interferometer's imaging optics. By addressing these matters upfront, we avoid limitations encountered in earlier stitching work and significantly boost reproducibility beyond that of the integrated interferometer on its own.

Paper Details

Date Published: 9 June 2006
PDF: 19 pages
Proc. SPIE 6149, 2nd International Symposium on Advanced Optical Manufacturing and Testing Technologies: Advanced Optical Manufacturing Technologies, 614903 (9 June 2006); doi: 10.1117/12.674189
Show Author Affiliations
Marc Tricard, QED Technologies, Inc. (United States)
Paul Dumas, QED Technologies, Inc. (United States)
Greg Forbes, QED Technologies, Inc. (United States)
Mike DeMarco, QED Technologies, Inc. (United States)


Published in SPIE Proceedings Vol. 6149:
2nd International Symposium on Advanced Optical Manufacturing and Testing Technologies: Advanced Optical Manufacturing Technologies
Li Yang; Shangming Wen; Yaolong Chen; Ernst-Bernhard Kley, Editor(s)

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