Wavefront reconstruction error of Shack-Hartmann wavefront sensors

Abstract

We have evaluated the wavefront reconstruction error for Shack-Hartmann wavefront sensors based on a series of simulations for various numbers of subapertures at various levels of measurement error in determining the Hartmann spot centroids. The optimum number of subapertures is derived for a given magnitude reference star in the cases of photon-noise limited and detector-noise limited sensors. When centroid measuring error is absent, the maximum number of Zernike terms that can be corrected by mans of modal adaptive compensation is about 1/5 of the number of subapertures. The residual phase error in wavefront reconstruction is shown to be sensitive to the measuring erorr of the spot centroids. It is essential to reduce the centroid measuring erorr in wavefront sensors for high level adaptive optics systems with a large number of degrees of freedom.