Sub-aperture approaches for asphere polishing and metrology

Marc Tricard*, Paul Dumas, Greg Forbes

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference proceeding contributionpeer-review

52 Citations (Scopus)


This paper summarizes some of QED Technologies' latest developments 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. MRF has 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 a wide variety of optical glasses, single crystals, and glass-ceramics. 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 either round or rectangular apertures. 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), our software also accounts for reference-wave error, distortion, and other aberrations in the interferometer's imaging optics. By addressing these matters up front, we avoid limitations encountered in earlier stitching work and significantly boost reproducibility beyond that of the integrated interferometer on its own.

Original languageEnglish
Title of host publicationProc. SPIE 5638 Optical Design and Testing II
EditorsYongtian Wang, Zhicheng Weng, Shenghua Ye, Jose M. sasian
Place of PublicationBellingham, WA
Number of pages16
Publication statusPublished - 2005
Externally publishedYes
EventOptical Design and Testing II - Beijing, China
Duration: 8 Nov 20048 Nov 2004


ConferenceOptical Design and Testing II


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