基于折射率梯度门限的气动光学窗口光传输研究

基于流场界面厚度（Interfacial—Fluid—Thickness，IFT）理论，建立了高折射率梯度门限模型来研究气动光学窗口光传输畸变。首先在光学窗口折射率梯度场基础上，提出高折射率梯度门限，忽略绝对值低于该门限的折射率梯度值，重构折射率场，并对其气动光学传输效应进行仿真。结果表明，当58．37％的梯度值被忽略时，得到的重构折射率场与原折射率场仿真光程差（OPD）最大相对误差不超过1．5％，验证了气动光学窗口高折射率梯度区域是产生光传输畸变的主要原因，也证实了该门限模型对气动光学窗口光传输效应进行仿真的可行性，对气动光学失真的机理、预测及校正有一定的指导意义。

Study on Optical Transmission of Aero-optical Window Based on Refractive Index Gradient Threshold

Based on the interfacial-fluid-thickness theory,a high refractive index gradient threshold model of the aero-optical window is established to study the optical distortion of the aero-optical window.Based on the refractive index gradient field of the aero-optical window,a high gradient threshold of refractive index is proposed.Refractive index gradients whose absolute values are below the threshold are set to zero and the refractive index field is reconstructed.Optical distortions of the original and reconstructed refractive index fields are simulated and analyzed.The comparisons reveal that when about 58.37% of the gradient values are set to zero,the maximum relative error of the optical path difference(OPD) between the original and the reconstructed refractive index fields is less than 1.5%.The results show that the high refractive index gradient regions of the aero-optical window are the main cause of optical distortions of the window,and it also verifies the feasibility of the threshold in the simulation for optical propagation in the aero-optical window.The research is useful for the theory,and the forecast and correction of optical distortions.