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Proceedings Paper

Deformable Mirror With Combined Piezoelectric And Electrostatic Actuators
Author(s): F. Merkle; K. Freischlad; H. -L. Reischmann
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Paper Abstract

The light propagation through the atmosphere limits the high angular resolution in astronomical imaging. Active optics is a method to overcome this problem. It allows a real-time optimization of the resolving power. An active mirror was developed which consists of, an electrostatically deformable membrane with 5 cm in diameter. The 0.5 micron thick aluminized polymer foil is elongated by an electrode array with 63 hexagonal elements arranged in a ring structure. The sensitivity is in the region of 0,05 microns per volt. It works up to 4 kHz without resonances. The maximum local tilt of the membrane is 3 microns per 5 millimeter. For an atmospheric tilt compensation of the wavefront the mirror housing is in a gimbal-mount. Piezo-electric actuators provide a total mirror angular movement up to 20 Hz and angular sensitivity of 77 arcsecs per kV. With this active mirror device and a multiprocessor-microprocessor control unit the stabilisation of the star-speckle pattern positions and the deconvolution of the speckle patterns are possible. Two control methods are in development and analized in comparison. One of them is working with a modified shearing interferometer as a wave-front sensor and a feedback with cross-talk compensation. The other is sensing the optical information in the image plane by a diode-array and estimating the wave-front by trial and error or different more sophisticated algorithms. The previous system is designed for the 0,75 m RC-telescope with alt-az mount at the Landessternwarte in Heidelberg, FRG.

Paper Details

Date Published: 4 November 1982
PDF: 9 pages
Proc. SPIE 0332, Advanced Technology Optical Telescopes I, (4 November 1982); doi: 10.1117/12.933528
Show Author Affiliations
F. Merkle, University of Heidelberg (Germany)
K. Freischlad, University of Heidelberg (Germany)
H. -L. Reischmann, University of Heidelberg (Germany)

Published in SPIE Proceedings Vol. 0332:
Advanced Technology Optical Telescopes I
Lawrence D. Barr; Geoffrey Burbidge, Editor(s)

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