利用标记分水岭法实现夏克-哈特曼波前传感器质心探测

由于光斑质心探测精度直接影响夏克-哈特曼波前传感器的波前探测精度，本文提出基于标记分水岭法来确定阵列光斑质心探测窗口。首先，对采集到的夏克-哈特曼阵列光斑图像进行平滑并求出其梯度图像；然后，利用大津（OTSU）阈值法在求出的梯度图像上进行目标标记，最后在标记过的梯度图像上进行分水岭分割，确定出每个光斑的探测窗口。由于该方法确定的质心探测窗口是对光斑实际大小进行匹配，故有效地抑制了噪声对质心探测的影响。实验结果表明：利用该方法确定光斑探测窗口所计算的质心精确度和稳定性均比传统的在子透镜窗口中计算光斑质心的方法要高。统计多幅图像计算得到的窗口质心标准差的平均值为0.010 9，比传统法计算出的平均值0.073 4提高了6倍，满足哈特曼波前传感器对光斑质心计算稳定性和精确度的要求。

Centroid detection of Shack-Hartmann wave-front sensor by marked watershed method

As the accuracy of wave-front detection of Shack-Hartmann sensors is mainly dependent on the accuracy of centroid detection of a focal spot, this paper proposes a dynamic determination method of array spot centroid detection window based on marked watershed segmentation. This method smoothes the spot image captured by a Shack-Hartmann wave-front sensor based on the marked watershed segmentation and obtains its gradient image, firstly. Then the OTSU method is used to mark the target on the gradient image. Finally, the marked gradient image is segmented by the marked watershed method and the detection window of every spot is determined. Because the detecting window can be matched with the actual size of spot, the affection of the noise on centroid detection is effectively suppressed. The experimental results demonstrate that the precision and stability of centroid detection by this method are higher than that of traditional method. The mean values of standard deviation in every detecting window of statistic multiple images are calculated, which is 0.010 9, 6 times that of the traditional method (0.073 4). It can satisfy the requirement of Shack-Hartmann wave-front sensors for precision and stability of centroid calculation.