遥感相机静态调制传递函数的地面测试原理

为了在地面研制阶段精确地测试空间遥感相机在各种空间频率处的调制传递函数,对测试原理进行了理论推导和分析,并基于此开展了整机在各种空间频率处的传函测试实验。在给出了遥感相机调制传递函数的测试实验链路的基础上,推导了各种空间频率的正弦波和方波靶标在整个链路中的光能传递过程,从而得到了遥感相机在各种频率下的调制传递函数和对比度传递函数的理论形式,并证明了在任何频率处二者之间的转换系数均为π/4。最后,在真空环境下进行了相机在1、1/2和1/3乃奎斯特频率下的调制传递函数测试。实验结果表明:某空间遥感相机在实验室条件下测得的1、1/2和1/3乃奎斯特频率下调制传递函数分别为0.21、0.40和0.59。经计算光学系统反推传函与设计传函衰减系数接近1,证明了方法的正确性。

Principle of static modulation transfer function measurement for remote sensing cameras

In order to precisely measure the modulation transfer function of the space camera at any frequency before launching, the measuring method is elaborated and some experiments are carried out. On the basis of giving the schematic diagram of modulation transfer function measurement, the transfer process of a sinusoidal and a square wave at any frequency are investigated. Consequently, the modulation transfer function and the contrast transfer function are derived, based on which the conversion coefficient of them is obtained as π/4 at any frequency. Finally, an experiment is implemented and the modulation transfer functions at 1, 1/2 and 1/3 Nyquist frequency are measured based on a certain remote sensing camera. The experiment result indicates that the modulation transfer functions at 1, 1/2 and 1/3 Nyquist frequency of the remote sensing camera used are 0.21, 0.40 and 0.59 at lab condition. Moreover, the reduction between the optical system modulation transfer function calculated on account of test results and the design value is near 1, which proves our derivation in this paper.