一种分析气动光学传输效应的等效透镜方法

摘要

针对2.5Ma 条件下气动光学传输效应对红外成像的影响进行机理分析。利用有限元仿真得到头罩外流场的温度、压力、空间分布形态的参数。在此数值仿真基础上，提出将头罩外流场等效为气体透镜的方法，计算透镜的折射率和焦距及其对原红外成像系统焦点位置的改变量约为49.66µm，此改变量小于焦深，则外流场对红外光线传输的影响基本可以忽略，成像不会产生模糊。测量风洞实验拍摄到退化图像的调制传递函数（MTF）与红外探测系统的 MTF 相差很小，验证了对气动光学传输效应机理分析的正确性。%Mechanism analysis of aero-optical transmission effects on infrared imaging at 2.5Ma is carried out. Parameters of external flow field of head guard, which consist of temperature, pressure and spatial distribution, are got by finite element simulation. On the basis of the numerical simulation, a method of which external flow field is equivalent to gas lens is proposed. The refractive index and focal length of the lens are calculated. The location change of focus of original infrared detection system is 49.66 µm. The effect on transmission of infrared lines can be neglected because the change is smaller than the focal depth. The difference between the MTF of degraded images got in wind tunnel test and infrared detection system is small, which verifies the validity of mechanism analysis of aero-optical transmission effects.