29 October 1999 Finite element analysis of low-cost membrane deformable mirrors for high-order adaptive optics
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Abstract
We demonstrate the feasibility of glass membrane deformable mirror (DM) support structures intended for very high order low-stroke adaptive optics systems. We investigated commercially available piezoelectric ceramics. Piezoelectric tubes were determined to offer the largest amount of stroke for a given amount of space on the mirror surface that each actuator controls. We estimated the minimum spacing and the maximum expected stroke of such actuators. We developed a quantitative understanding of the response of a membrane mirror surface by performing a Finite Element Analysis (FEA) study. The results of the FEA analysis were used to develop a design and fabrication process for membrane deformable mirrors of 200 - 500 micron thicknesses. Several different values for glass thickness and actuator spacing were analyzed to determine the best combination of actuator stoke and surface deformation quality. We considered two deformable mirror configurations. The first configuration uses a vacuum membrane attachment system where the actuator tubes' central holes connect to an evacuated plenum, and atmospheric pressure holds the membrane against the actuators. This configuration allows the membrane to be removed from the actuators, facilitating easy replacement of the glass. The other configuration uses precision bearing balls epoxied to the ends of the actuator tubes, with the glass membrane epoxied to the ends of the ball bearings. While this kind of DM is not serviceable, it allows actuator spacings of 4 mm, in addition to large stroke. Fabrication of a prototype of the latter kind of DM was started.
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Robert S. Winsor, Anand Sivaramakrishnan, Russell B. Makidon, "Finite element analysis of low-cost membrane deformable mirrors for high-order adaptive optics", Proc. SPIE 3785, Advanced Telescope Design, Fabrication, and Control, (29 October 1999); doi: 10.1117/12.367614; https://doi.org/10.1117/12.367614
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