Test facility for long-focal-length mirrors

Harold E. Bennett; John J. Shaffer

doi:10.1117/12.147445

24 June 1993 Test facility for long-focal-length mirrors

Harold E. Bennett, John J. Shaffer

Proceedings Volume 1848, 24th Annual Boulder Damage Symposium Proceedings -- Laser-Induced Damage in Optical Materials: 1992; (1993) https://doi.org/10.1117/12.147445
Event: Optical Materials for High Power Lasers, 1992, Boulder, CO, United States

Abstract

Testing the optical figure and focal length of laser mirrors with radii of curvature in the 10 to 100 m range is difficult. If the mirror is concave, a source can be placed at the center of curvature. Air turbulence over these long path lengths makes interferometry difficult, however, and greatly reduces measurement accuracy. Convex mirrors are even more difficult to measure. A solution is to produce a slightly converging or diverging beam from a virtual source. The actual optical path in which turbulence may develop can then be made very short. A three-element test system consisting of a parabola, a transmission sphere, and a folding flat is described. It is capable of measuring both optical flats and convex or concave mirrors up to 40 cm in diameter with radii of curvature from 10 m to infinity. System accuracy is 1/20th wave rms in optical figure and 0.2% in radius of curvature. A discussion is given of the systematic errors introduced when the parabola is used in other than parallel light.

Citation Download Citation

Harold E. Bennett and John J. Shaffer "Test facility for long-focal-length mirrors", Proc. SPIE 1848, 24th Annual Boulder Damage Symposium Proceedings -- Laser-Induced Damage in Optical Materials: 1992, (24 June 1993); https://doi.org/10.1117/12.147445

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