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

1 Citation (Scopus)


Subaperture polishing technologies have enabled the production of higher precision optics with increasingly difficult figure requirements. Magnetorheological Finishing (MRF®), for example, is a production-proven, deterministic, subaperture finishing technology that has excelled at overcoming the limitations of traditional polishing. However, metrology is a critical piece of the optics fabrication process, and the dependence on interferometry is especially acute for computer-controlled, deterministic finishing. Without accurate full-aperture metrology, figure correction using sub-aperture polishing technologies would not be possible. In addition to sub-aperture polishing technology, QED Technologies® (QED) has developed a Subaperture Stitching Interferometer (SSI®) that extends the effective aperture and dynamic range of a phase measuring interferometer. QED's SSI uses innovations in software and hardware to improve the capacity and accuracy of traditional interferometers, overcoming many of the limitations previously faced. The SSI workstation can perform high-accuracy automated subaperture stitched measurements on spheres, flats, and mild aspheres up to 200 mm in diameter. The workstation combines a six-axis precision stage system, a commercial Fizeau interferometer of 4″ or 6″ aperture, and a specially developed software package that automates measurement design, subaperture data acquisition, and the mathematical construction of the full-aperture phase map. The stitching algorithm incorporates a general framework for compensating several types of errors introduced by the interferometer and stage mechanics. These include positioning errors, viewing system distortion, and the system reference wave error. The SSI has proven to be a precise, accurate, and flexible metrology system vital to precision optics manufacturing. Partnering the SSI with the Q22 MRF systems has allowed QED to offer customers a complete state-of-the-art finishing solution that increases speed and yield, while decreasing costs. This paper will briefly review Magnetorheological Finishing (MRF) capabilities and discuss the Subaperture Stitching Interferometer (SSI) as production-ready metrology that enables cost effective manufacturing of precision optical surfaces.

Original languageEnglish
Title of host publicationLaser Metrology and Machine Performance VII - 7th International Conference and Exhibition on Laser Metrology, Machine Tool, CMM and Robotic Performance, LAMDAMAP 2005
Place of PublicationBellingham, WA
Number of pages11
ISBN (Electronic)1861941188
Publication statusPublished - 2005
Externally publishedYes
Event7th International Conference and Exhibition on Laser Metrology, CMM and Machine Tool Performance, LAMDAMAP 2005 - Cranfield, United Kingdom
Duration: 27 Jun 200530 Jun 2005


Other7th International Conference and Exhibition on Laser Metrology, CMM and Machine Tool Performance, LAMDAMAP 2005
Country/TerritoryUnited Kingdom


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