Instrumentation, Techniques, and Measurement

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

[+] Author Affiliations
Margaret Z. Dominguez, Ping Zhou, James H. Burge

University of Arizona, College of Optical Sciences, 1630 East University Boulevard, Tucson, Arizona 85721, United States

Jianxin Li

Nanjing University of Science and Technology, School of Electronics and Optical Engineering, Nanjing Shi, Jiangsu Sheng 210014, China

Opt. Eng. 55(12), 124107 (Dec 23, 2016). doi:10.1117/1.OE.55.12.124107
History: Received October 22, 2016; Accepted November 29, 2016
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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.

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© 2016 Society of Photo-Optical Instrumentation Engineers

Citation

Margaret Z. Dominguez ; Jianxin Li ; Ping Zhou and James H. Burge
"Vertex radius measurement of an off-axis parabola with a three-ball spherometer", Opt. Eng. 55(12), 124107 (Dec 23, 2016). ; http://dx.doi.org/10.1117/1.OE.55.12.124107


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