Wavefront reconstruction error of Shack-Hartmann wavefront sensors

Abstract

We have evaluated the wavefront reconstruction error for Shack-Hartmannwavefront sensors based on a series of simulations for various numbersof subapertures at various levels of measurement error in determiningthe Hartmann spot centroids. The optimum number of subapertures isderived for a given magnitude reference star in the cases ofphoton-noise-limited and detector-noise-limited sensors. When thecentroid measuring error is absent, the maximum number of Zernike termsthat can be corrected by means of modal adaptive compensation is about1/5 of the number of subapertures. The residual phase error in wavefrontreconstruction is shown to be sensitive to the measuring error of thespot centroids. It is essential to reduce the centroid measuring errorin wavefront sensors for high-level adaptive optics systems with a largenumber of degrees of freedom.