Wavefront reconstruction and mirror surface optimization for adaptive optics
Axtell, Travis W.
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The problem of wavefront reconstruction is important in high precision optical systems, such as astronomical telescopes, where it is used to estimate the distortion of the collected light caused by the atmosphere and corrected by adaptive optics. A generalized orthogonal wavelet wavefront reconstruction algorithm is presented in this research for use with gradient measurements from a Shack- Hartmann wavefront sensor. This algorithm can be implemented using a number of different wavelets for improved performance in the presence of noise. An extension of this algorithm is also presented to provide wavefront estimation in the presence of isolated branch points where the phase is undetermined. The wavefront is obtained by augmenting the wrapped observations with a filtered curl of the vector field. The wavefront estimation can then be used for surface control of a deformable mirror. A third contribution is in deformable mirror surface control. The control signals to a deformable mirror are computed that minimize the wavefront error using constrained optimization to ensure that the hardware actuator voltage limits are satisfied. A sequence of optimal solutions is used to verify the linear model of a deformable mirror. A multigrid approach to the optimization problem is shown to improve computation efficiency.
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