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Proceedings Paper

Optical surface control for adaptive optics
Author(s): M. Bea; Martin Huonker; Adolf Giesen
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Paper Abstract

An optical surface monitoring system is presented which allows us to detect in an on-line modus the actual surface shape of a coolant-driven adaptive mirror. The system consists of a laser diode and a position sensitive diode (PSD) which detects the deflection of a probe beam depending on the actual surface slope of the controlled adaptive optic. Thus, a direct relation between sensor signal and active element (surface) is realized. The differences to indirect sensor signals (coolant pressure, strain gauge) are shown. In particular, the effects of laser induced surface deformation and of mechanical tolerances on the resulting surface shape are discussed. This surface control will be integrated in a system of flexible beam expanders which allows a complete control of the focal diameter and of the focal position of the spot, independent of the distance between laser and work station. Basically two beam expanders have to be used, each of them containing one adaptive copper mirror. The first expander, located close to the laser, allows us to control the beam diameter on the focussing optic. In the focussing optic itself the second adaptive mirror controls the focal position. The interaction of these independent adaptive elements allows a variation of the focus radius up to 1:5 while the focal position can be changed independently in a range up to 10 mm around the geometrical focus position.

Paper Details

Date Published: 4 November 1994
PDF: 15 pages
Proc. SPIE 2246, Laser Materials Processing and Machining, (4 November 1994); doi: 10.1117/12.193114
Show Author Affiliations
M. Bea, Univ. Stuttgart (Germany)
Martin Huonker, Univ. Stuttgart (Germany)
Adolf Giesen, Univ. Stuttgart (Germany)


Published in SPIE Proceedings Vol. 2246:
Laser Materials Processing and Machining
Rolf-Juergen Ahlers; Peter Hoffmann; Hermann Lindl; Ruediger Rothe, Editor(s)

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