空间相机系统自准直传函测试方法及应用

Self-collimating MTF test method and application of space camera

  • 摘要: 调制传递函数(传函)测试是空间相机研制过程的重要环节,常规传函测试需要用到平行光管。自准直传函测试方法是一种不依赖于平行光管的系统传函测试方案。首先介绍了自准直传函测试系统的原理和搭建方案。其次对比了平行光管测试的过焦曲线和自准直传函测试的过焦曲线,发现该系统对焦面离焦敏感程度不亚于平行光管,得到该系统可以用于判定焦面位置正确性的结论。再次分析了自准直靶标条纹经过平面镜反射后偏转的现象,该现象将引入测试误差。给出了偏转角的数值计算公式和条纹偏转对传函值影响的计算公式。针对离轴系统对偏转角敏感的问题,给出自准直靶标的设计方法。利用该方法可以将靶标条纹偏转造成的传函测试误差降至可以忽略的量级。然后讨论了采用自准直传函测试方案时相机探测器与测试靶标的拼接,分析了探测器滤光片对焦面位置的影响,提出了探测器与靶标共焦面的设计及拼接方案。最后总结了该测试方法在某型号相机的实际应用,为自准直传函测试方法在后续系统的应用打下基础。

     

    Abstract: MTF test is an important part of the camera manufacture process. General practice of MTF test needs to use the parallel light tube. Self-collimating MTF test method does not rely on the parallel light tube. Firstly, the principle and construction plan of the self-collimating MTF test system were introduced. Secondly, the curve measured by parallel light tube and self-collimating MTF test were compared. It is obtained that the self-collimating MTF test system has high sensitivity to the off-focus, this method can be used to determine the focal plane position. Thirdly, the phenomenon of the deflection of the self-collimating target fringe were analyzed, which will affect the MTF test result. The formula of the deflection angle of target fringe and the formula of the influence of fringe deflection on MTF test result were given. Design method of the self-collimating target of off-axis system were given. With this method, the deviation of MTF caused by the deflection of the target fringe can be reduced to a negligible level. Splicing relationship between the detector and the test target of self-collimating MTF test system were discussed, influence of detector's filter on focal plane position was analyzed, and design and splicing program of the detector and the target were proposed. Finally, the application of self-collimating MTF test on a camera were summarized. The result obtained by this study can be used to other camera in the future.

     

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