研究了刃边法测试光学系统调制传递函数(MTF)的原理, 提出将改进倾斜刃边法用于红外成像系统MTF的测量。考虑刃边倾斜角度的测量误差和噪声干扰会引起红外系统MTF的测量误差, 采用Canny算子、直线拟合和边缘扩散函数(ESF)重构行数变动等方法来提高MTF的测试精度; 同时针对ESF与线扩散函数(LSF)提出有效的降噪算法来降低噪声对MTF测试精度的影响, 从而系统地降低了MTF的测量误差。搭建了实验平台, 以红外成像系统的理论模型和实测参数得到的MTF曲线为依据, 实验验证了本文方法的有效性, 测试分析了刃边倾角的变化对MTF测试精度的影响。实验结果表明: 通过本文方法测试得到的MTF曲线的测试精度为0.010, 测试重复精度为0.008, 刃边倾角保持在2°~10°。实验结果显示: 本文方法有效地降低了刃边倾角的测量误差和噪声干扰对MTF测试产生的影响, 测试结果具有良好的重复性。

The principles of optical Modulation Transfer Function(MTF) measurement by the edge method for an optical system were researched and an improved inclined edge method for the MTF measurement of an infrared imaging system was proposed. As the edge angle measurement error and noise will cause the MTF measurement error of the infrared system, the Canny operator, line fitting and Edge Spread Function (ESF) reconstruction row number changes were combined to improve the measuring accuracy of the MTF, meanwhile, an effective denoise algorithm for the ESF and the Line Spread Function (LSF)was used to reduce the effect of noise on the MTF measuring accuracy.With the methods mentioned above, the measurement errors of MTF were reduced systematically. An experimental platform was set up. Based on the theoretical model of infrared imaging system and MTF curve obtained by detected parameters, the feasibility of the proposed method was verified and the effect of changed edge angle on the MFT measuring accuracy was analyzed. Experimental results show that the measurement accuracy of MTF curve obtained by the method is 0.010, the measuring repeat accuracy is 0.008, and the edge angle should be kept between 2 °and 10 °. It concludes that the method effectively reduces the influences of the edge angle measurement error and noise on the MTF measurement, and the measuring results show good measurement repeatability.