【作者】 马春林；

【导师】 杨瑞科；

【作者基本信息】 西安电子科技大学 ， 无线电物理， 2008， 硕士

【摘要】 激光具有高相干度、高亮度、方向性好等普通光源无法比拟的优点使它在各个学科与技术领域的应用无所不在、与日俱增。但当激光在大气中长距离传输时,大气严重限制了各种激光工程(如激光通信、激光雷达、激光测距等)系统的使用性能。激光大气传输对激光雷达探测目标的能力具有重要的影响。因此,在对激光雷达系统进行设计、研制和定标时,必须考虑到大气传输的影响。本论文对1. 06μm激光大气传输特性进行了理论研究,主要讨论了影响激光雷达探测性能的两个大气效应:衰减效应和由湍流引起的闪烁效应。分析了对流层中影响激光传输的各种因素;阐述了大气对激光传输的各种衰减效应,包括大气中气体分子和气溶胶粒子对激光信号的吸收和散射;在晴朗、云、雾、霾、雨等各种天气情况下,利用一些经验公式计算了1 .06μm激光在大气传输中的衰减。结果表明,在近红外波段对于对流层大气中霾粒子的衰减预测应用Mie理论计算更合理;云雾引起的衰减一般较大,并且随着能见度的减小,衰减增加较快。因此,当Vb < 15km时,霾引起的衰减就需要考虑;当V b较小时,云、雾的激光衰减是限制系统性能的主要因素。以激光雷达距离方程为基础,根据具体要求,选定系统参数,在一定能见度条件下,研究单基地激光雷达的最小接收功率、正常检测时接收机的输入端所需的最小信噪比随最大探测距离之间的关系。叙述了湍流对激光传输的影响,重点研究了大气弱湍流效应中的闪烁效应对直接探测激光雷达系统的影响,这些研究对激光雷达系统的设计具有一定的参考价值。更多还原

【Abstract】 The applications of laser are increasing and omnipresent because of its high coherent, brightness, directivity, which general light sources can’t compare to it. Performances of various laser engineering systems (such as laser communication, laser radar, laser detecting) are restricted seriously by the atmosphere for long span laser transmission. The transmission of laser plays an important role in the ability of laser radar when it detecting target. Therefore, atmospheric transmission must be taken into account when in the designing, development and calibration of laser radar system.In this paper, the atmospheric propagation characteristic of 1.06μm laser is theoreticly investigated, the two effects: attenuation and scintillation induced by turbulence, are discussed which influence the performance of the laser radar’s detection. The influence of atmospheric attenuation upon laser radar, including the absorption and scattering induced by gas molecule and aerosol are discussed. Various factors which influence the transmission of laser are analyzed. In different weathers, such as clearness, fog, haze, rain and snow etc, the attenuation and atmospheric transmission at 1.06μm are calculated with several experiential formulas. The results show that Mie theory is more reasonable than experiential model for atmospheric hazes attenuation prediction in the troposphere. The attenuation induced by clouds and fog increase quickly with the visibility decrease. Therefore, for Vb < 15km, the haze attenuation must be considered. For lower V b, the performance of laser system is limited by the attenuation of clouds and fog.On the base of range equation of laser radar and parameters of laser radar system desired,on some visibility, the minimal receiver power and the minimal input SNR of general detection as a function of the maximal detection range are researched.In addition, the influence of weakly turbulence on laser transmission is depicted, the scintillation of the turbulence influence on the direct detect system for laser radar is studied. These researches are helpful for designing laser systems for laser radar.更多还原