提出一种能高准确度测试光电成像系统调制传递函数的改进的倾斜刃边法.利用一种自动确定高低阈值的改进Canny算子提取边缘位置点, 对提取到的边缘位置点进行线性拟合求得刃边倾角, 在利用费米函数拟合边缘扩散函数的过程中, 提出一种邻域平均值和设定误差容限的多重去噪改进方法.通过仿真与物理实验证明了本文方法的有效性, 并分析了刃边倾角、噪声变化对本文方法与传统方法MTF测试准确度的影响.实验结果表明: 本文方法的调制传递函数测试准确度达到0.004 9, 重复准确度达到0.003 1, 皆优于传统方法; 说明其具有较高的测试准确度和良好的测试重复性, 并且具有较强的抗噪性, 基本不受刃边倾角变化的影响.

In this study, an improved slanted edge method was proposed. It had a high accuracy for measuring the Modulation Transfer Function (MTF) of electro-optical imaging system. We put forward an automatic determination of the high and low threshold modified Canny operator to detect the edge points, and the edge slant angle is obtained by linear fitting of the edge points. In the process of fitting the edge spread function (ESF) by Fermi function, we put forward a modified method to reduce the influence of noise. It was composed of averaging in adjacent region and setting the tolerance of error. The method in this paper is proved effectively by the experimental results, and analyzing the influence of the change of the edge slant angle and noise on the MTF measurement accuracy. The experimental results show that the measurement accuracy of the modified slanted edge method is 0.004 9, and the repeat accuracy is 0.003 1, which is higher than the traditional methods. It proves that the modified slanted edge method has high measurement and repeat accuracy, and also has a better immunity to noise and edge angle.