基于归一化互相关因子的波前测量研究

为实现对光束近场强度分布不均匀或低信噪比场景中的高精度波前测量，分析了低信噪比情况下，在基于夏克-哈特曼波前传感器的自适应光学系统中，分别使用基于归一化互相关因子的相关算法与目前常用的自适应阈值灰度质心法时，信噪比对质心探测精度及后续波前复原精度的影响。通过数值仿真与实验对比，证明了基于归一化互相关因子的相关算法在不同光强条件下的波前测量结果一致性与准确性都高于自适应阈值的灰度质心法，其可为自适应光学系统在像差探测能力上提供更高的准确性与鲁棒性。针对基于归一化互相关因子的相关算法计算量较大，软件计算实时性较差，难以满足工程实用需要的问题，提出了一种基于算法实现优化与多级并行计算的加速方法，对448单元子孔径的夏克-哈特曼波前传感器可实现每秒上千赫兹的计算速度，可满足大部分自适应光学系统波前探测实时性的工程需要。

Research of wavefront sensing based on normalized correlation factor

In order to achieve high accuracy wavefront sensing in scenarios where the near field intensity of the beam is not uniformly distributed or in low signal to noise ratio scenarios,the influence of signal to noise ratio on the detection accuracy of the plasmas and the subsequent wavefront reconstruction accuracy is analyzed in an adaptive optics system based on a Shack Hartmann wavefront sensor using a correlation algorithm based on normalized mutual correlation factor and the currently used adaptive threshold grayscale plasmas,respectively,under low signal to noise ratio conditions.Through numerical simulation and experiment comparison,it is indicated that the correlation algorithm based on normalized correlation factor get higher uniformity and accuracy under various intensities of the incident beam than the grayscale mass center method with adaptive thresholding,which provides accuracy and robustness in the aberration detection capability of adaptive optics systems.In response to the problem that the correlation algorithm based on the normalized correlation factor is large and the software computation is poor in real time,which is difficult to meet the practical needs of engineering,an acceleration method based on the algorithm to achieve optimization and parallel computation is proposed.The Shack Hartmann wavefront sensor with 448 sub apertures can achieve calculation speeds in the thousands of hertz per second,meeting the engineering needs for real time wavefront detection in most adaptive optics systems.