Design of systems involving easily measurable aspheres

Paul E. Murphy*, Dave Stephenson, Andrew E W Jones, Greg W. Forbes

*Corresponding author for this work

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

6 Citations (Scopus)


Aspheric surfaces provide significant benefits to an optical design. Unfortunately, aspheres are usually more difficult to fabricate than spherical surfaces, making the choice of whether and when to use aspheres in a design less obvious. Much of the difficulty comes from obtaining aspheric measurements with comparable quality and simplicity to spherical measurements. Subaperture stitching can provide a flexible and effective test for many aspheric shapes, enabling more cost-effective manufacture of high-precision aspheres. To take full advantage of this flexible testing capability, however, the designer must know what the limitations of the measurement are, so that the asphere designs can be optimized for both performance and manufacturability. In practice, this can be quite difficult, as instrument capabilities are difficult to quantify absolutely, and standard asphere polynomial coefficients are difficult to interpret. The slope-orthogonal 'Q polynomial representation for an aspheric surface is ideal for constraining the slope departure of aspheres. We present a method of estimating whether an asphere described by Q polynomials is measurable by QED Technologies' SSI-A system. This estimation function quickly computes the testability from the asphere's prescription (Q polynomial coefficients, radius of curvature, and aperture size), and is thus suitable for employing in lens design merit functions. We compare the estimates against actual SSI-A lattices. Finally, we explore the speed and utility of the method in a lens design study.

Original languageEnglish
Title of host publicationOptifab 2013
EditorsJulie L. Bentley, Matthias Pfaff
Place of PublicationBellingham, Washington
Number of pages10
ISBN (Print)9780819497475
Publication statusPublished - 2013
Externally publishedYes
EventOptifab 2013 - Rochester, NY, United States
Duration: 14 Oct 201317 Oct 2013

Publication series

NameProceedings of SPIE
ISSN (Print)0277-786X


OtherOptifab 2013
CountryUnited States
CityRochester, NY


  • Asphere
  • Design for manufacturing
  • Optical design
  • Orthogonal polynomials
  • SSI-A
  • Subaperture stitching interferometry


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