Subaperture metrology technologies extend capabilities in optics manufacturing

Marc Tricard*, Greg Forbes, Paul Murphy

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)


Subaperture polishing technologies have radically changed the landscape of precision optics manufacturing and enabled the production of higher precision optics with increasingly difficult figure requirements. 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 subaperture polishing technologies would not be possible. QED Technologies® has developed the Subaperture Stitching Interferometer (SSI®) that extends the effective aperture and dynamic range of a phase measuring interferometer. The SSI's novel developments in software and hardware improve the capacity and accuracy of traditional interferometers, overcoming many of the limitations previously faced. The SSI performs high-accuracy automated measurements of spheres, flats, and mild aspheres up to 200 mm in diameter by stitching subaperture data. The system combines a six-axis precision workstation, a commercial Fizeau interferometer of 4" or 6" aperture, and dedicated software. QED's software automates the measurement design, data acquisition, and mathematical reconstruction 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, the system reference wave error, etc. The SSI has been proven to deliver the accurate and flexible metrology that is vital to precision optics fabrication. This paper will briefly review the capabilities of the SSI as a production-ready, metrology system that enables cost-effective manufacturing of precision optical surfaces.

Original languageEnglish
Article number59650B
Pages (from-to)1-11
Number of pages11
JournalProceedings of SPIE - The International Society for Optical Engineering
Publication statusPublished - 2005
Externally publishedYes


  • Aspheric optics
  • Domes
  • Interferometry
  • Metrology
  • SSI
  • Subaperture stitching


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