【作者】 常虹；

【导师】 范志刚；

【作者基本信息】 哈尔滨工业大学 ， 光学工程， 2011， 博士

【摘要】 随着空间和军事技术的发展,透射式红外光学系统的使用越来越广泛,苛刻的工作环境对光学系统的性能提出了更高的要求。由于红外材料对温度变化的敏感性,热环境是影响透射式红外光学系统性能的主要因素,特别是对于弹载红外光学系统,气动加热的影响使得系统中存在较大的温差。提高红外光学系统在热环境中的稳定性,对于军事技术的发展具有积极重要的意义。本文重点研究了透射式红外光学系统热效应相关理论、提高红外系统热光学稳定性的关键技术以及系统热光学稳定性仿真和实验方法,主要包括以下几个部分:(1)均匀温度变化下光学系统的无热化设计方法研究。研究了光学系统的热效应以及热差产生的机理。基于热差互补原理,设计了中波红外(3.7~4.8μm)无热光学系统,该系统在-40℃~60℃温度范围内,均匀温度分布热环境中像质稳定,在17lp/mm空间频率处调制传递函数达到0.5以上。(2)轴向温度梯度下光学系统热光特性研究。研究了轴向温度梯度下透镜的形变及折射率分布。在此基础上,首先针对忽略透镜内部温度梯度的情况,研究了光学系统无热化设计原理及方法,提出了轴向温度梯度下光学系统广义消热差条件;通过在静态无热T-C图中引入轴向温度梯度Δt坐标,建立了轴向温度梯度下的无热T-C-Δt图;设计了轴向温度梯度下的无热光学系统,系统在-20℃~60℃温度范围内,无论是否存在轴向温度梯度,均能保持稳定良好的像质。其次讨论了透镜内部轴向温度梯度的影响,从光线追迹角度出发,研究了光线轨迹随系统结构参数变化的趋势,在此基础上提出了改善光学系统像质的结构参数修改原则,并对原设计系统进行了修改,使其在考虑透镜内部轴向温度梯度的情况下亦能保持良好的像质。(3)径向温度梯度下光学系统热光特性研究。建立了径向温度梯度下透镜形变以及折射率分布的热效应模型,利用此模型研究径向温度梯度下光学系统性能随系统结构参数变化的趋势,提出了径向温度梯度下的光学系统无热化设计方法。运用此方法设计了在径向温度梯度下无热的光学系统,系统在-20℃~60℃温度范围内,无论是否存在径向温度梯度,均能保持稳定良好的像质。(4)透镜无热装配技术研究。针对完全圆周粘结固定的透镜,对粘结层约束提出了一种新的假设,在此假设的基础上推导了无热粘结厚度方程,建立了无热粘结厚度的简化模型和改进模型。通过有限元分析方法,对一系列胶粘透镜装配体的无热厚度进行了仿真求解,并将仿真的结果与无热粘结厚度方程计算的解析结果进行比较,指出了方程的适用范围。(5)系统热光学稳定性仿真与实验。由于梯度温度分布热环境在实验中难以复现,轴向温度梯度和径向温度梯度下光学系统的性能通过仿真方法来分析,而均匀温度热环境下的光学系统性能通过实验进行了分析。仿真和实验的结果表明,通过无热化设计得到的光学系统在各种热环境中具有稳定的光学性能,本文提出的无热化设计方法能够有效提高光学系统在热环境中的稳定性。更多还原

【Abstract】 With the development of space and military technology, the refractive infrared (IR) optical systems are widely applied, the tough working conditions put forward higher requirement to the capability of optical system. As the infrared materials are sensitive to the temperature variation, thermal environment is the major factor which impacts the performance of refractive infrared optical system. Particularly, for missile borne infrared optical system, aerodynamic heating may result larger temperature difference in optical system. It has great significance on the development of military technology to improve the stability of IR optical system under thermal environment.In this dissertation, the correlation theories of the thermal effects of refractive infrared optical system, key techniques in developing the thermo-optical stability of infrared system, simulation and test methods of thermal stability are mainly discussed. The dissertation includes the following several parts:(1)Athermalization of optical system under uniform temperature.The thermal effects of optical system and the mechanism of thermal aberration are studied. Based on the thermal aberration complementary principle, a mid-wave (3.7μm~4.8μm) infrared athermalized optical system is designed, which has stable image quality in the uniform temperature environment during -40℃~60℃range, the modulation transfer function (MTF) value of optical system reaches to 0.5 at the spatial frenqucy of 17lp/mm.(2)The characteristics of optical system under axial temperature gradient. Lens surface deformation and variation of refractive index under axial temperature gradient are studied. Firstly, by ignoring the lens interior axial temperature gradient, the athermalization principle and design method for optical system are studied, the generalized athermalization equations of optical system under axial temperature gradient are proposed An athermalization chart (T-C-Δt chart) is built by introducing axial temperature gradientΔt to the stastic athermalization chart (T-C chart). An athermalized optical system under axial temperature gradient is designed, which can keep the image quality stable and good in the temperature range of -20℃~60℃, regardless of whether the axial temperature gradient exists or not. Secondly, based on ray tracing, the impact of lens internal axial temperature gradient is discussed, and the variation tendencies of ray tracing with the structure parameters are studied. Then the modification principles of structure parameters are put forward to improve the image quality of optical system under aixal temperature gradient, by which the original system is optimized to keep good image quality when lens internal axial temperature gradient is considered.(3)The characteristics of optical system under radial temperature gradient. The thermal effect models of lens deformation and refractive index distribution are built, which are used to research the variation tendencies of optical system performance with the structure parameters. An athermalization method of optical system under radial temperature gradient is proposed based on the models. Using this method, an athermalized optical system under radial temperature gradient is designed, which can keep the image quality stable and good, in the temperature range of -20℃~60℃, regardless of whether the radial temperature gradient exists or not.(4)Lens athermal mounting technique. A new assumption of bond layer constrain is put forward for full circle bond lens. Based on this assumption, the athermal bond thickness equation is derived; a simplified model and a modified model of athermal bond thickness are built. Through finite element analysis, the simulation results of athermal bond thicknesses are solved for a series of bond lens. Through comparing the simulation solutions and the analytic solutions calculated with athermal bond thickness equations, the application range of the analytic equations are derived.(5)Thermo-optical stability simulation and experiment. As the thermal environments of gradient temperature distribution are difficult to realize in the experiment, the performance of optical system under axial and radial temperature gradient is analyzed by simulation method, the performance of optical system under uniform temperature analyzed by experiment. The results of simulation and experiment indicated that, the optical system designed by athermalization have stable optical performace under thermal environment, the athermalization methods put forward in this dissertation can improve the stability of optical system effectively.更多还原