Parallel control loops based on spatial subband processing for adaptive optics

Abstract

Adaptive control and filtering algorithms have been proposed previously for correcting turbulence-induced phase distortions in large telescopes and other optical systems operating in atmosphere. The problem is posed as an adaptive disturbance-rejection problem with many channels. The solution given is an adaptive feedforward control loop built around a multichannel adaptive lattice filter. The paper presents a parallel-processing structure that spreads the large real-time computational burden of the adaptive control loop over separate processing blocks for groups of control and filtering channels. The grouping of these channels is based on a parameterization of actuator space that divides the span of the actuator influence functions into sub-bands of spatial frequency. Simulation results presented demonstrate the significant improvement in imaging resolution produced by the parallel adaptive control loop compared to a conventional linear time-invariant control loop.