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.
Original language | English (US) |
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Article number | 124107 |
Journal | Optical Engineering |
Volume | 55 |
Issue number | 12 |
DOIs | |
State | Published - Dec 1 2016 |
Keywords
- Spherometer
- off-axis paraboloid
- vertex radius
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics
- General Engineering