Cumulative wavefront reconstructor for the Shack-Hartmann sensor

Abstract

We present a new direct algorithm aiming at the reconstruction of the opticalwavefront from the Shack-Hartmann sensor measurements in Single ConjugateAdaptive Optics (SCAO) systems. The objective of an adaptive optics systemdesigned for a large telescope can be only achieved if the wavefrontreconstruction is sufficiently fast. Our scheme does not contain any explicitregularization for the reconstruction process but is still able to provide agood quality of reconstruction. The analysis of quality is given for threevarying parameters: the diameter of the telescope, the number of subaperturesand the level of photon noise. It has been shown both analytically andnumerically that the quality of the reconstruciton, measured by the Strehlratio, is reasonable for the small photon noise level and increases with theincreasing number of subapertures for the same telescope size. The impact of thephoton noise on the reconstruction gets higher with the increasing telescopediameter. The computational complexity of the method is linear in the number ofunkowns. Counting all summation and multiplication steps the scaling factor is$14$. Moreover, due to its simple structure, the cumulative reconstructor ispipelinable and parallelizable, which makes the effective computation evenfaster.