Performance analysis of software-based methods to expand the dynamic range of Shack-Hartmann wavefront sensor

The traditional Shack-Hartmann wavefront sensor requires that the focal spot of each microlens must remain in its corresponding sub-aperture range to avoid mistakes in spot-subaperture matching. We present a software-based recognition algorithm that can obtain a much larger dynamic range while maintaining high precision: Iterative extrapolation method. In order to find the corresponding spots of all the subapertures, the method first select a 3x3 spot-array and establishes a polynomial function about the spot position to predict and find the adjacent spots, and then carry on this procedure in successive steps of the iterative algorithm. The performance of the iterative extrapolation method to expand the dynamic range of various wavefront are studied and compared with the sorting method by simulation. Finally, experiments were carried out to further verify the performance of the method. Both simulation and experimental results show that this algorithm can effectively expand the dynamic range of SHWS and the deviation of reconstructed wavefront from ideal one is below 0.08 lambda (PV).