High-speed closed-loop dual deformable-mirror phase-diversity testbed

摘要

A proof-of-concept phase-diversity (PD) wavefront sensing and control (WFS&C) testbed has been developed that displays 5/1,000 wave RMS accuracy, operates at a sample/estimation rate of 100Hz, uses the extended scene of interest in lieu of a guide star, and is comprised of all low-cost commercial-off-the-shelf (COTS) parts - including the PD processor. This testbed allows closed-loop operation via a dual deformable-mirror (DM) concept where two DMs are optically conjugate to the exit pupil: one acting as an independent disturbance and the other reacting to PD WFS&C commands in order to correct the system wavefront. The use of low-cost, COTS components demonstrated the flexibility of a PD WFS&C approach, and additionally allowed for this system to be conceived, designed, assembled and brought to operation in approximately nine months. Automatic calibration efforts begun on this testbed have allowed for the quick discrimination of prominent PD forward-model parameters and a more rapid verification and validation (V&V) process. Also aiding the V&V process is a novel spatial-heterodyning optical interferometer that collects all information in a single snapshot and may be made synchronous with the fast PD sample rate. This demonstration proves a PD WFS&C subsystem capability suitable for use on a wide variety of adaptive-optics imaging systems.