Adaptive optics: wavefront reconstruction by adaptive filtering and control

Abstract

In the class of adaptive optics problems considered, phase distortions due to atmospheric turbulence are corrected by adaptive wavefront reconstruction with a deformable mirror, i.e., the control loop that drives the mirror adapts in real time to time-varying atmospheric conditions, as opposed to the linear time-invariant control loops used in conventional "adaptive optics". 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. Simulation results are presented for a one-meter telescope and a two-layer atmospheric turbulence profile. These results demonstrate the significant improvement in imaging resolution produced by the adaptive control loop compared to a conventional linear time-invariant control loop.