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Proceedings Paper

Study on 400-1500nm reflecting coatings on lightweight mirrors
Author(s): Yao-ping Zhang; Hong Xu
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Paper Abstract

Image-stabilization systems are widely used during astronomical image integration because of their large gain of image quality and relatively simple control system. Probably the simplest system is the one that tilts a mirror to correct angular variations caused by atmospheric fluctuations, vibration tilt of the telescope, or angular errors of internal components. Lightweight (structured) mirrors based on piezoelectric actuators are of important part of these systems. The coating of lightweight (structured) mirrors and the associated support systems involves the prediction of the magnitude and nature of the elastic deformation of mirror surface due to mechanical and thermal residual stress during coating. The clamping ways are firstly analyzed in this paper, and the finite element method of structural analysis makes it possible to include conveniently the deformation and stress of a lightweight mirror in consideration of effects of thermal gradients and mechanical loads during coating. Two models with different clamping ways are set up by using FEA soft. The distribution of deformation and stress of lightweight mirror caused by thermal residual stress is analyzed. The coated lightweight mirror is measured by interferometer and the result shows the calculated and measured results have good compatibility. Based on the results of these studies, we select a better clamping way to coating the lightweight mirror. The lightweight mirror for astronomical telescope intensified with silver has good optical properties, but the silver mirror has the faults of weak adhesion to glass substrate and the mirror is easily corroded by atmospheric pollution. In order to solve this problem, several silver adhesion layers are studied. Due to mutual action of Al2O3 and silver film, the developed Al2O3-based silver intensified mirror has overcome the above faults and achieved good effect. Finally, the coating is measured by making use of spectrometer. The average reflectance of coating is greater than 98% in 400-1500nm range, and the lightweight mirror can satisfy practical requirement.

Paper Details

Date Published: 21 November 2007
PDF: 6 pages
Proc. SPIE 6721, 3rd International Symposium on Advanced Optical Manufacturing and Testing Technologies: Large Mirrors and Telescopes, 67210M (21 November 2007); doi: 10.1117/12.782943
Show Author Affiliations
Yao-ping Zhang, Institute of Optics and Electronics (China)
Hong Xu, Institute of Optics and Electronics (China)


Published in SPIE Proceedings Vol. 6721:
3rd International Symposium on Advanced Optical Manufacturing and Testing Technologies: Large Mirrors and Telescopes

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