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Proceedings Paper

Thermal deformation of reflective optics
Author(s): Martin Huonker; Adolf Giesen; Helmut Huegel
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Paper Abstract

Increasing laser beam power for industrial material processing causes increasing demands on the beam guiding system and the optical components used. Especially the thermally induced deformation of the optics influences the beam propagation at higher power levels. This in particular is true for beam guiding systems which often include a large number of mirrors and/or long beam paths, where the diverging effect upon the beam accumulates with every single mirror. The thermally induced deformation of reflective optics is strongly related to the power and diameter of the incident laser beam. Therefore, the propagation of a beam through a system which is subject to thermally induced deformation is of nonlinear nature. The calculation of the beam propagation as well as the design of beam guiding systems for high laser powers has to take this effect into account. In order to include the diverging effect of a deformed reflective mirror in the calculation of the propagation, it is necessary to develop an analytical description of the relation of the beam parameters and the optical effects upon the beam and the beam-mirror interaction, respectively. Our approach for an analytical description is based on a finite-element analysis of laser mirrors being deformed by various beams with different beam powers, beam diameters and energy distributions. The calculated surface deformations were analyzed using a new method, which allows the calculation of the resulting focal length of a deformed surface in relation to the diameter and energy distribution of the incident beam. The numerical results of this analysis are compared with measurements. For minimizing the effect of the thermally induced deformation, a new cooling concept for metal mirrors has been investigated numerically and experimentally. The results of this optimization are discussed in detail.

Paper Details

Date Published: 25 September 1997
PDF: 13 pages
Proc. SPIE 3102, Rapid Prototyping and Flexible Manufacturing, (25 September 1997); doi: 10.1117/12.281304
Show Author Affiliations
Martin Huonker, Univ. Stuttgart (Germany)
Adolf Giesen, Univ. Stuttgart (Germany)
Helmut Huegel, Univ. Stuttgart (Germany)

Published in SPIE Proceedings Vol. 3102:
Rapid Prototyping and Flexible Manufacturing
Rolf-Juergen Ahlers; Gunther Reinhart, Editor(s)

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