【作者】 张郡；

【导师】 张爱红； 范志刚；

【作者基本信息】 哈尔滨工业大学 ， 光学工程， 2007， 硕士

【摘要】 带有光学成像探测系统的飞行器在大气层内高速飞行时,其平面窗口与大气之间发生剧烈的相互作用,产生严重的气动光学效应。处在气动热环境中的窗口由于热传导和热应力等效应导致窗口材料外形和光学性质的变化,使原本光学特性均匀的窗口外形产生畸变,并且在内部形成了折射率梯度分布。此时当平面波入射到畸变窗口时,出射后的等光程波面偏离了理想波面,波面发生畸变,从而使通过窗口的目标光线产生偏移、模糊等,成像质量下降,严重影响了制导精度。本课题主要通过光线追迹法来研究气动热环境下外形、折射率产生不均匀分布的光学窗口对目标成像光束的影响。计算窗口的各项光学评价函数(主要包括PSF、MTF、失真图像、能量集中度图、波前方差、波前倾斜量、Strehl比)。首次将像素匹配理论应用到光学系统评价中,对于研究气动光学图像恢复工作具有一定的参考价值。首先从光线追迹的角度出发,采用计算机3D处理方法与光学设计相结合的方法,追迹光线计算波面上每点经过窗口到达预定平面的光程,并在Visual C++6.0环境下编制了相应的光线追迹程序,对揭示气动光学效应、研究气动光学验证方法提供了参考。然后计算窗口的点扩散函数、传函、能量集中度和Strehl比等系统评价指标;提出了两种解决像素匹配问题的算法,并对这两种算法进行比较,论文选择算法2为优先算法。论文中首次通过对仿真结果进行分析,总结了影响图像失真的若干因素;并且创建了一种系统个例验证方法,通过验证程序的运行结果可以得知:本课题中对气动热环境下建立的光学窗口空间有限元模型以及相应的像质评价算法是可行的,所得结果可用于实际工程中相关实验的研究。更多还原

【Abstract】 When optical imaging guidance air vehicle flies in atmosphere at a high speed, the intensive interaction between the optical plane window and the atmosphere will cause intensive aero-optical effects. In aero-dynamic environment, the shape and optical property of optical window will change because of thermal transmission and thermal stress effects, and then the window whose original optical property is homogeneous distorts, which results in gradient distribution of the refractive index inside the window. When the plane-wave transmits in the distorted window, the aplanatic emergent wave after the window will deviate from the ideal wave front because of the distorted optical window and gradient distribution of refractive index of it. Thus the object ray from the window will distort and cause bore-sight error.The main task of this paper is researching the influences of distorted shape of the optical window and gradient refraction index on the imaging of object lights. In this paper, we have coded the ray-tracing program cross the distorted and non-uniform index window, drew the distorted wave front chart, and calculated the optical evaluation function(include PSF, MTF, Strehl ration).The theory of pixel-matching is applied to image-evaluation for the first time.First of all, from the point view of ray tracing, by the computer 3D processor and optical design, the OPD was calculated from the reference wave to the reconverted wave front, and then a corresponding ray-tracing program was compiled in Visual C++ 6.0 environment, and the program provides reference for disclosure aero-optics effect and the method of validating the aero-optics.Besides, PSF, MTF, Encircled energy, wavefront variance and Strehl ration were calculated for evaluating the image quality. Two methods of solving pixel-matching problems were offered. After comparing them, algorithm 2 was selected as the preferential method.After the analysis of simulation results, some influence factors of image distortion were summarized for the first time. Then, a verification program was compiled. The result of the verification program indicated that the ray-tracing program of optical window and the following image-evaluating program were feasible and the research was useful for practical engineering.更多还原