基于最小二乘法的卫星相机MTF测量

对于对地观察卫星而言，为了定量评定其成像质量，对其MTF进行测量是非常重要的，它为比较不同卫星的性能提供了理论依据。一般的在轨MTF测量主要是对已知目标进行成像，由于天气和图像混叠的影响，这种方法对星载程序带来了很大限制。本文提出使用最小二乘法测量星载相机的MTF．对同一景物两次成像．一次采用高分辨率模式．另一次使用低分辨率模式，当两者分辨率比值足够高时，就可以通过将高分辨率图像与一个点扩散函数卷积和乏采样模拟得到低分辨率图像．并通过迭代使模拟图像与实测低分辨率图像的差在最小二乘意义下达到最小，以此得到点扩散函数。一旦迭代过程收敛，通过对点扩散函数进行傅立叶变换即可得到待测低分辨率图像的MTF。

MTF Assessment of the Satellite camera Based on the Least Square Mehtod

The measurement of the Modulation Transfer Function(MTF)to quantify the quality of an imaging system provesto be very important in the context of Earth observation satellites. Its knowledge also allows to compare the characteristics of different satellites. Classical in flight MTF measurement methods is based upon devoted well known targets. These techniques induce heavy consrtaints upon satellite payload programming taking into account nebulosity conditions and aliasing effects. The least square method introduced to assess the MTF of the satellite camera, which consists in taking two images of the same scene, one in a high resolution mode and the other one in a lower resolution mode. When the resolution ratio is high enough, it is possible to simulate the lower resoltion image through convolution with point spread function(PSF) and undersampling. This method consists in an iterative process, according to which the PSF evolves in order to minimize a least square criterion measuring the difference between the simulation and the low resolution image. Once the process has converged, taking the Fourier Transform of the PSF gives the estination of the low resolution image MTF.