DYNAMIC-RANGE EXPANSION OF A SHACK-HARTMANN SENSOR BY USE OF A MODIFIED UNWRAPPING ALGORITHM

An algorithm for expanding the dynamic range of Shack-Hartmann sensors is proposed. The distribution of the spot dislocations is treated wit h a modified unwrapping algorithm that is widely used in interferometr y. The algorithm unwraps the spot dislocations and assigns the spots t o their original subapertures, leading to a huge expansion of the dyna mic range. For the proposed algorithm there remains a limitation on th e maximum wave-front curvature instead of on the maximum wave-front sl ope. Examples are given that show spot fields that were wrapped four t imes; the measured wave front had a peak-to-valley value of 116 lambda . (C) 1998 Optical Society of America.