一种扩大夏克-哈特曼波前传感器动态范围的迭代外推法

Iterative Extrapolation Method to Expand Dynamic Range of Shack-Hartm ann Wavefront Sensors

夏克-哈特曼波前传感器(SHWS)通常要求每个子透镜的对应光斑必须在其相应的子孔径范围内,以方便确认光斑与子孔径间的对应关系。提出了一种基于软件的识别方法即迭代外推法,可以在光斑跑出其对应子孔径范围时,仍能确认每一个光斑对应的子孔径,使SHWS具有更大的动态范围。该方法首先找到一个可排序的3×3光斑阵列,并建立关于光斑质心坐标与其行列序号间关系的多项式函数,以预估和搜索相邻光斑;然后利用已搜索光斑区边缘处的3×3光斑阵列,继续向外搜索,直到找到所有光斑,完成所有光斑的行列排序;最后通过调整光斑行列序号的整体偏移,确认光斑与子孔径间的对应关系。仿真研究了该迭代外推法的性能,并通过实验进一步验证了该方法的实用性。

The Shack-Hartmann wavefront sensor(SHWS)generally requires that the focal spot of each microlens must remain in its corresponding sub-aperture area so that it is easy to decide the mapping relationship of spots and subapertures.We present a software-based recognition method,i.e.,an iterative extrapolation method,which can still find the corresponding spot of each subaperture when the spots get out of their subaperture areas,so that the SHWS obtains a much larger dynamic range.First,this method finds a 3×3 sortable spot-array and establishes a polynomial function for the relationship between the centroid coordinate of the spot and its row and column numbers to predict and find the adjacent spots.Then it uses a new 3×3 spot-array on the edge of the already-found spots to continue searching outwards until all the spots are found.Finally,it decides the corresponding spot of each subaperture by adjusting all the row and column numbers by an offset.The performance of this iterative extrapolation method to expand the dynamic range of the SHWS under various types of wavefront aberrations is studied by simulation,and the experiments are carried out to further verify the practicability of this method.