Construction and Control of a Deformable Mirror for Adaptive Optics

Abstract

Adaptive optics has expanded the limits of ground-based astronomy since its inception. A wide breadth of technologies have been developed for AO systems both in telescopes and in other applications, leading to a variety of deformable mirror types. Voice-coil deformable mirrors specifically have been identified as a useful tool in situations that require large stroke, aperture size, and resiliency to actuator failure. These situations are becoming more and more frequent with increasing telescope diameters, as well as larger networked optical needs such as free space communication systems or co-phased arrays. Historically VCDM designs have proven successful, but are often paired with increased complexity and cost due to active sensing. This work aims to mitigate those limitations by operating in an open-loop configuration, and uses exclusively COTS parts during construction. In this dissertation, I show a 7-actuator VCDM we have constructed and characterized in terms of noise, linearity, and hysteresis. I detail the process of computing the reconstruction matrix, and present examples of applied surface modes. Various methods of dealing with the complications arising from open-loop control are given. I also present a new approach to AO control metrics, which can be used in the context of object parameter retrieval. This Fisher Information based optimization process makes use of prior knowledge of the problem to reduce error associated with the measurement. I show the expected level of improvement possible for several problem types, and discuss in what situations it may be useful.