Analysis of Non-Uniform Gain for Control of a Deformable Mirror in an Adaptive-Optics System
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING AND MANAGEMENT
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The objective of this research was to develop and experimentally verify the use of spatially varying gain maps on the servo-loop controller of a deformable mirror for improvements in the performance of an adaptive optics system and the mitigation of instabilities that can occur over edge actuators of a deformable mirror. The edge subapertures of a Shack-Hartmann wavefront sensor have lower signal-to-noise ratios and are more susceptible to measurement errors than fully illuminated center subapertures. Spatially varying gain maps were then developed to compensate for edge effects by having lower filter gains beta on the edge actuators. This lowered the bandwidth over the edge actuators which are the most susceptible to the edge effects. A gain map of lower filter gains beta over just the outer actuators was experimentally shown to increase the overall Strehl ratio of the AO system in all of the tested turbulence conditions. Experiments were also conducted in regimes where instabilities formed over the edge actuators of the DM. Gaussian gain maps significantly reduce the overall residual phase variance over the edge actuators reducing the formation of the instabilities.