遥感相机动态调制传递函数与时间延迟积分CCD行周期误差的关系

Relation of line transfer period error and dynamic MTF of TDICCD in remote sensing camera

考虑推扫式遥感相机中的时间延迟积分(TDI)CCD行周期误差对成像动态调制传递函数(MTF)影响较大,且积分级数越高影响越大,本文分析并推导了存在行周期误差时TDICCD推扫成像的动态MTF数学模型并进行了仿真验证。首先,介绍了典型的TDICCD的电荷行转移时序,分析并推导了该时序下单级和多级积分级数时的采样窗口函数以及该时序下TDICCD的行周期误差率与动态MTF之间的精确函数关系,并指出本文推导的精确函数比传统函数多一个非线性参量。然后,进行了仿真实验。结果表明:行周期误差率ΔT/T=0时,该时序下的TDICCD在Nyquist频率下的动态MTF为静态MTF的0.632 5倍(TDICCD相数b=4),显示得到的动态MTF与行周期误差率关系曲线较传统方法得到的曲线有明显差异且动态MTF值要高于后者。最后,给出了在不同积分级数下、5%动态MTF下降率指标要求时的行周期误差率最大容许值。

The error of line transfer frequency from Time Delay Integration（TDI）CCD has strong in- fluence on dynamic Modulation Transform Function（MTF） and it is stronger when the integral grade is higher. Therefore, this paper develops an accurate mathematical model for dynamic MTF and line transfer period error rate was developed. Firstly, a typical line transfer timing of TDICCD was intro- duced and the window functions of one integral grade and multiple integral grade were derived. On these bases, the relationship between line transfer period error rate and dynamic MTF for this timing was established by Fourier transform of the window functions and a nonlinear parameter was derived in the function which is none in the traditional one. Then, simulations and experiments were per- formed, which indicate that when AT/T=O, the dynamic MTF value for this timing is 0. 632 5 times of static MTF with the number of phases b^4. It also indicates that there are obvious differences be- tween dynamic MTF curves from proposed method and traditional method. Finally according to the requirement of the index, the maximum line transfer period error rates with different integral grades are given, which ensures that the decline of the dynamic MTF is less than 5%.