Approach to high-accuracy qualification of long-radius spherical       surfaces (Invited Paper)

George C. Hunter; P. L. Pfluke; Lars A. Selberg

doi:10.1117/12.132160

20 October 1992 Approach to high-accuracy qualification of long-radius spherical surfaces (Invited Paper)

George C. Hunter, P. L. Pfluke, Lars A. Selberg

Proceedings Volume 1720, Intl Symp on Optical Fabrication, Testing, and Surface Evaluation; (1992) https://doi.org/10.1117/12.132160
Event: International Symposium on Optical Fabrication, Testing, and Surface Evaluation, 1992, Tokyo, Japan

Abstract

Techniques for absolute interferometric measurement of surface figure are often used for qualification of spherical surfaces specified as (lambda) /20 PV or better. As the radius of curvature increases, these techniques become impractical due to the length of cavity required, and environmental effects. Our approach has been to certify a reference surface with a shorter, i.e., manageable radius of curvature, and then to proceed through a series of measurements with surfaces of increasing radius, while maintaining a manageable cavity length. At each stage, the `reference' data from the previous stage is subtracted from the new measurement in order to better approximate the actual surface. The requirements of spatial registration and image magnification are stringent if one is to use the phase measured data directly. This process can be simplified if one uses a polynomial fit to the surface, e.g., Zernikes. The technique is described for the qualification of a surface with an 8 meter radius of curvature and is examined for sources of error.

Citation Download Citation

George C. Hunter, P. L. Pfluke, and Lars A. Selberg "Approach to high-accuracy qualification of long-radius spherical surfaces (Invited Paper)", Proc. SPIE 1720, Intl Symp on Optical Fabrication, Testing, and Surface Evaluation, (20 October 1992); https://doi.org/10.1117/12.132160

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