点源信标相关哈特曼-夏克波前传感器光斑偏移测量误差分析

在基于哈特曼-夏克波前传感器(SH-WFS)的自适应光学系统中,通常采用质心算法探测点源信标的子孔径光斑偏移量.然而质心算法探测精度受到诸如减阈值等因素的影响,在低信噪比(SNR )时不能准确估计光斑质心位置,而相关哈特曼算法不需要减阈值,具有更好的鲁棒性.本文在介绍相关SH-WFS基本原理的基础上,通过建立基于点源信标探测的相关SH-WFS算法的随机噪声模型,推导了光斑偏移测量误差表达式,系统分析了光子噪声、CCD读出噪声、背景光子噪声等因素对相关SH-WFS测量误差的影响.并进行了数值仿真及实验,仿真 关键词： 相关哈特曼-夏克波前传感器 相关哈特曼算法 质心算法 测量误差

Error analysis of correlating Shack-Hartmann wave-front sensor for a point source

In Shack-Hartmann wavefront sensor(SH-WFS) based adaptive optics system, the centroiding algorithm is usually used to estimate the centroid of a point source spot. But the detecting accuracy of the centroiding algorithm is affected by many factors such as threshold selection, so that the centroid position of the spot cannot be evaluated accurataly under the condition of low signal-to-noise ratio(SNR) . Comparatively the correlating algorithm for Shack-Hartmann wave front-sensing is more robust because it need not reduce the thresholding. In this paper, based on the the principle of the correlating SH-WFS, the measurement error of the correlating SH-WFS is derived by building up the noise model of the correlating SH-WFS. The influences of spot size, photon noise, read out noise and background light noise on the measurement of the correlating SH-WFS are analyzed systematically. The numerically simulation results and the experimental results are consistent well with the theoretical analyses.