Ultra-Thin Highly Deformable Composite Mirrors

Abstract

Optical quality mirrors are heavy, expensive and difficult to manufacture. This paper presents a novel mirror concept based on an active laminate consisting of an ultra-thin carbon-fiber shell bonded to a piezo-ceramic active layer coated with patterned electrodes. Mirrors based on this concept are less than 1 mm thick and hence are very lightweight and flexible. They also have a large dynamic range of actuation that allows them to take up a wide range of deformed configurations. This concept is compatible with relatively high-volume manufacturing processes and can potentially achieve a significant reduction in cost in comparison to currently available active mirrors. It is also suitable for applications ranging from concentrators for solar power generation to primary mirrors for optical telescopes. The paper presents an overview of the mirror components as well as a simple design relationship for sizing the active layer. The expected performance of a preliminary design for a 1 m diameter mirror with a radius of curvature of 15 m is computed numerically, showing that a set of 96 actuators can remove an edge-to-edge manufacturing-induced cylindrical curvature of 5 mm to an RMS accuracy of 50 μm. The prescription of the mirror can also be adjusted to a radius of curvature of 11 m with an accuracy of 160 μm. The development and characterization of a proof-of-concept prototype mirror is also presented.

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