Extreme adaptive optics system optimization with the high order test bench

Abstract

Extreme adaptive optics systems dedicated to the search for extrasolar planets are currently being developed for most 8-10 meter telescopes. Extensive computer simulations have shown the ability of both Shack-Hartmann and pyramid wave front sensors to deliver high Strehl ratio correction expected from extreme adaptive optics but few experiments have been realized so far. The high order test bench implements extreme adaptive optics on the MACAO test bench with realistic telescope conditions reproduced by star and turbulence generators. A 32×32 actuator micro deformable mirror, one pyramid wave front sensor, one Shack-Hartmann wave front sensor, the ESO SPARTA real time computer and an essentially read-noise free electron multiplying CCD60 (E2V CCD60) provide an ideal cocoon to study the different behavior of the two types of wave front sensors in terms of linearity, sensitivity to calibration errors, noise propagation, specific issues to pyramid or Shack-Hartmann wave front sensors, etc. We will describe the overall design of this test bench and will focus on the characterization of two essential sub-systems: the micro deformable mirror and the phase screens.