在大气相干长度r0的测量中,相同的仪器和数据处理方法,不同的信噪比对实验测得结果有较大影响。通过分析实测中的噪声模型, 利用matlab仿真,保持信号光强度不变,在光斑图像上添加高斯噪声,改变图像的信噪比。以不含背景时的光斑图像求得的r0作真值, 分别求出不同信噪比下r0对真值的相对偏差。发现当信噪比小于5时,相对偏差大幅增加。在相同信噪比下,采用不同的背景 处理方法,发现减去平均背景后,剩下的高斯噪声对质心位置的影响很小。在不同信噪比下,减1倍平均背景及0.6倍背景起伏标准差后相对偏差整体表现最小。

In the field measurement, different signal to noise ratios (SNR) have a great impact on the experimental results with the same instrument and data processing methods. By analyzing the noise model measured in the field, the same noise is added to the spot image simulated to change the SNR while the signal intensity is kept unchanged. When the SNR is less than 5, the relative deviation increased significantly. Then different methods are used to subtract the background noise under the same SNR, and it is found that the Gaussian noise has little effect on the centroid position after subtracting the average background value. The results show that the overall performance of the subtraction of 1 times average background and 0.6 times background fluctuation standard deviation is found to be the best.