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Proceedings Paper

Accurate interferometric measurements of mild aspheres without null correction
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Paper Abstract

Traditionally, the most accurate measurements of aspheric surfaces have relied on interferometric null tests. These usually require "null correction" optics, which often take significant time and expense to design and fabricate, and are specific to a particular asphere prescription. Alignment and calibration of the null correction optics can also be quite difficult. Thus there is a significant benefit to a flexible, accurate, "operator-friendly" alternative to the null test. Testing aspheres without null correction (using a spherical wavefront) has been very limited. A typical interferometer can acquire only a few micrometers of fourth-order aspheric departure before the interference fringes become too dense to resolve. Other "non-null" issues include accounting for the part's aspheric shape and optical aberrations of the interferometer. QED's SSI-ATM addresses these limitations, allowing a standard Subaperture Stitching Interferometer (SSI®) to automatically measure mild aspheric surfaces. The basic principles of how subaperture stitching enhances asphere capability are reviewed. Furthermore, SSI-A measurements from real aspheres are presented, along with null test measurements where available.

Paper Details

Date Published: 14 May 2007
PDF: 4 pages
Proc. SPIE TD04, Optifab 2007: Technical Digest, TD040N (14 May 2007); doi: 10.1117/12.719484
Show Author Affiliations
Paul E. Murphy, QED Technologies (United States)
Jon Fleig, QED Technologies (United States)
Stephen O'Donohue, QED Technologies (United States)
Gary DeVries, QED Technologies (United States)


Published in SPIE Proceedings Vol. TD04:
Optifab 2007: Technical Digest
James J. Kumler; Matthias Pfaff, Editor(s)

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