高分辨相机传函测试误差分析

Testing error analysis of high resolution camera modulation transfer function

文中通过对高分辨相机静态传函测试中误差产生的机理进行分析,提出了相应的测试策略,有效抑制条纹靶标周期偏差、环境振动及图像噪声对MTF的影响。TDI CCD相机的MTF测试值受到条纹靶标周期偏差、环境振动和图像噪声的影响,通过分析上述因素对MTF测量值的影响机理,建立了条纹靶标周期偏差、环境振动和图像噪声对传函的影响模型,并分别提出了针对条纹靶标周期偏差引入的MTF测量值修正方法,以及针对噪声影响提出了MTF计算模板的最优化选取算法,通过最优化模板计算得到的MTF测量值可以有效抑制图像噪声的影响,同时抑制环境振动以及条纹靶标周期偏差引起的摩尔条纹对MTF测量值的影响。根据对某空间相机实测图像的分析结果,横向模板尺度应不大于摩尔条纹横向周期的4%,纵向模板的尺度应不大于摩尔条纹纵向周期的2%,分析表明模板越大,MTF受噪声影响越小,但受环境振动和条纹靶标周期偏差影响越大,实际工程中应结合相机本身的噪声水平,在最优区间选取MTF计算模板,使得测量值更准确。

The Methods was proposed based on the analysis of Modulation Transfer Function（MTF） test error of spaceborne TDI CCD camera, the influence from grating period error, environment vibration and imaging noise was retained from MTF testing. The MTF testing is affected by grating period error,environment vibration and imaging noise. Through analyzing the influence mechanism, a mathematic module was established to describe the influence of grating period error, environment vibration and imaging noise. The correcting algorithm of the testing MTF error from grating period error was proposed, and the optimization mask of MTF testing was also proposed to reduce the influence from image noise. Based on the testing images, the horizontal scale of MTF mask should not exceed 4% of the Morie fringe horizontal period, the vertical scale of MTF mask should not exceed 2% of the Morie fringe vertical period. The analysis shows that if the mask is larger, the influence from noise is reduced, but the influences from the environment vibration and grating period error will increase. In the real project, the mask scale should be selected based on the imaging system noise level, and ensure the accuracy of the MTF testing.