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Optical Engineering

Vertex radius measurement of an off-axis parabola with a three-ball spherometer
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Paper Abstract

A spherometer is often used to precisely measure the radius of curvature of a spherical surface. It can also measure the vertex radius of a more complex surface such as an off-axis parabola (OAP). This paper provides a reliable algorithm to find the vertex radius of an OAP by solving a few equations based on the test geometry. This algorithm can also be easily expanded to any conic surface with high-order aspheric coefficients. The algorithm was verified by measuring an 8-inch diameter OAP and comparing the results with its known prescription. Results show good agreement. An example of measuring the vertex radius of a 4-m diameter OAP is also presented. In addition to this, a calculation was done to show that the coma and astigmatism are independent of the clocking of the spherometer on the optic.

Paper Details

Date Published: 23 December 2016
PDF: 8 pages
Opt. Eng. 55(12) 124107 doi: 10.1117/1.OE.55.12.124107
Published in: Optical Engineering Volume 55, Issue 12
Show Author Affiliations
Margaret Z. Dominguez, College of Optical Sciences, The Univ. of Arizona (United States)
Jianxin Li, Nanjing Univ. of Science and Technology (China)
Ping Zhou, College of Optical Sciences, The Univ. of Arizona (United States)
James H. Burge, College of Optical Sciences, The Univ. of Arizona (United States)


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