Large Surface Measuring Machine

Mark Egdall; Robert S. Breidenthal

doi:10.1117/12.935919

22 September 1983 Large Surface Measuring Machine

Mark Egdall, Robert S. Breidenthal

Proceedings Volume 0416, Applications of Optical Metrology: Techniques and Measurements II; (1983) https://doi.org/10.1117/12.935919
Event: 1983 Technical Symposium East, 1983, Arlington, United States

Abstract

A new surface measuring concept developed under government contract at Itek Optical Systems has been previously reported by Allen Greenleaf. The method uses four steerable distance-measuring interferometers at the corners of a tetrahedron to determine the posi-tions of a retroreflecting target at various locations on the surface being measured. A small wooden breadboard had been built and tested, demonstrating the feasibility of the concept. This paper reports the building of a scaled-up prototype surface measuring machine to allow the measurement of large aspheric surfaces. A major advantage of the device is that, unlike conventional interferometry, it provides surface measurement in absolute coordinates, thus allowing direct determination of radius of curvature. In addition, the device is self-calibrating. Measurements of a 24-inch mirror have been made with the new machine, giving repeatability of 4 µ m peak sag in the curvature and accuracy of 0.7 μm rms in the surface figure at best focus. The device is currently being used in the production grinding of large aspheric mirrors at Itek. The device is potentially scalable to other industries where highly accurate measurement of unusual surfaces is required.

Citation Download Citation

Mark Egdall and Robert S. Breidenthal "Large Surface Measuring Machine", Proc. SPIE 0416, Applications of Optical Metrology: Techniques and Measurements II, (22 September 1983); https://doi.org/10.1117/12.935919

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