Open-Loop Woofer-Tweeter Control on the LAO Multi-Conjugate Adaptive Optics Testbed

摘要

Advances in micro deformable mirror (DM) technologies such as MEMs, havestimulated interest in the characteristics of systems that include a highstroke mirror in series with a high actuator count mirror. This arrangement isreferred to as a woofer-tweeter system. In certain situations it may bedesirable or necessary to operate the woofer DM in open-loop. We present asimple method for controlling a woofer DM in open loop provided the devicebehaves in an approximately linear fashion. We have tested a mirror that webelieve meets our criterion, the ALPAO DM52 mirror. Using our open-loop methodwe fit several test Kolmogorov wavefronts with the mirror and have achieved anaccuracy of approximately 25 nm rms surface deviation over the whole clearaperture, and 20 nm rms over 90% of the aperture. We have also flattened themirror in open loop to approximately 11 nm rms residual.