Focal-plane wavefront sensing with high-order adaptive optics systems
  We investigate methods to calibrate the non-common path aberrations at an adaptive optics system having a wavefront-correcting device working at an extremely high resolution (larger than 150x150). We use focal-plane images collected successively, the corresponding phase-diversity information and numerically efficient algorithms to calculate the required wavefront updates. The wavefront correction is applied iteratively until the algorithms converge. Different approaches are studied. In addition of the standard Gerchberg-Saxton algorithm, we test the extension of the Fast & Furious algorithm that uses three images and creates an estimate of the pupil amplitudes. We also test recently proposed phase-retrieval methods based on convex optimisation. The results indicate that in the framework we consider, the calibration task is easiest with algorithms similar to the Fast & Furious. 
Visa Korkiakoski, Christoph U. Keller, Niek Doelman, Matthew   Kenworthy, Gilles Otten, Michel Verhaegen
astro-ph.IM physics.optics