【作者】 顾吉林；

【导师】 许文海；

【作者基本信息】 大连海事大学 ， 通信与信息系统， 2012， 博士

【摘要】 大气辐射传输特性是指电磁波在大气中传输时,大气中的粒子对电磁波吸收和散射作用,作用效果包括两方面：一方面,大气对目标自身辐射能量以及目标对太阳辐射的反射能量经过大气传输路径到达成像系统镜头前的能量衰减；另一方面,大气对太阳辐射能量单次散射和多次散射、对目标场景周围环境热辐射的多次散射、大气中粒子的自身热辐射等致使辐射传输到成像系统镜头前能量增强。辐射在大气中的能量衰减通常用大气透过率来表示,能量增强通常用大气程辐射来表示。本文以实际工程应用为背景,实时计算大气的红外传输衰减和路径辐射,从而得到去除大气干扰的、以及目标真实的辐亮度,主要开展了以下研究：1)通过分析大气参数、吸收截面、散射截面、辐射传输距离、频率等计算因子和大气分子消光光学厚度之间的关系,根据大气中气体的成分,研究了水汽和氮气分子连续光谱吸收光学厚度,以及二氧化碳、甲烷、臭氧、一氧化碳和一氧化二氮等分子的带光谱吸收光学厚度的计算方法。最后进行了大气分子散射光学厚度的计算。2)建立典型天气(霾、雾、沙尘以及雨等)条件下气溶胶粒子复折射率数据库,依据气溶胶粒子谱分布实验数据,完善了典型天气气溶胶粒子谱分布模型,结合气溶胶粒子复折射率数据库与大气能见度等大气参数,利用米散射理论计算典型天气条件下气溶胶消光光学厚度,根据光学厚度和大气透过率的关系,完善了在3～5μm波段,针对典型天气,大气传输路径中大气透过率的计算模型。通过对典型天气大气透过率仿真计算的结果表明,本文所建立的模型可以正确有效地进行霾、雾、沙尘以及雨等典型天气条件下大气透过率的计算。3)提出了基于高斯光束空间传输小光斑可调原理实现远距离大气透过率和大气程辐射组合验证的测量方法。通过分别测量激光器出口处的光斑和探测器接收光斑的能量分布,分析了二者光斑的能量差值,计算得到该波长经过传输距离的大气透过率和大气程辐射综合影响的结果。从远距离测量大气透过率和大气程辐射组合验证的角度出发,通过改变失调的卡塞格伦天线的主副镜之间的位置,使传输光斑半径在一定的传输距离、尺寸范围内可调,并且从实验仿真上验证了其可行性。该系统可以解决远距离测量大气透过率和大气程辐射的组合验模问题。本文以He-Ne激光器为例,设计了卡塞格伦天线的主副镜参数,使光斑半径大小在40～60mm、传输距离在10 km内范围可调。4)提出了典型天气大气程辐射的计算模型。以大气辐射传输理论为基础,针对光谱波长3-5微米,综合分析了光学厚度的计算方法以及倾斜路径与太阳参数对大气程辐射模型的影响,对霾、雾、沙尘和雨天建立了大气程辐射计算模型。大气程辐射模型包括大气对太阳辐射的单次和多次散射,大气对地表热辐射传输的多次散射以及传输路径的大气自身热辐射四个子模型。仿真结果验证了大气程辐射模型的正确性。5)本文针对典型天气对大气辐射传输特性模型进行了仿真验证,将本文大气辐射传输特性模型的参数输入和PcModWin软件参数输入保持一致,将二者的输出结果进行比较,计算出不同天气不同波数的大气透过率和大气程辐射的仿真误差,得到典型天气条件下的大气透过率的最大相对误差为3.846%,大气程辐射的最大相对误差为5.011%,能够满足一般红外探测工程上对误差的要求。更多还原

【Abstract】 When electromagnetic waves transmit in atmosphere, the characteristics of atmospheric radiation transmission refer to two aspects based on the effects of absorption and scattering between the particles in the atmosphere and electromagnetic wave:on one hand, the energy of target radiations and solar radiations reflected in front of the camera imaging system is attenuated through atmospheric transmission. On the other hand, the energy in front of the camera imaging system is enhanced because of the energy of solar radiations of single scattering and multiple scattering, the target thermal radiation of multiple scattering and the particles thermal radiation in the atmosphere. Atmospheric transmittance is usually expressed energy attenuation of the radiation in the atmosphere. Atmospheric path radiation is usually expressed energy enhanced. Based on engineering applications in practice and to calculate infrared atmospheric transmission and path radiance real-time without atmospheric interference, the following contents are the major research works of this thesis:1. The relationship between the calculation factors and atmospheric molecular extinction optical depth is analyzed, the calculation factors including atmospheric parameters, absorption cross sections, scattering cross sections, radiative transmission distance, frequency etc. Absorption optical depths of continuous spectral of water vapor and nitrogen and absorption optical depths of band spectral of carbon dioxide, methane, ozone, carbon monoxide and an oxide of nitrogen are calculated according to the composition of gases in the atmosphere. Finally scattering optical depth of atmospheric molecular is calculated.2. The database for complex refractive index of aerosol particle under the conditions of typical weather (haze, fog, dust and rain, etc.) was set up. The model of aerosol size distribution was improved according to the experimental data of aerosol size distribution, and atmospheric parameterswere considered such as atmospheric visibility.the optical depths of aerosol extinction in the typical weather are calculated by Mie scattering theory.According to the relationship between optical depth and atmospheric transmittance, the calculation model of the atmospheric transmittance is improved from3 to 5 micron spectral wavelength. The simulation verifies the model correct by simulation calculation of atmospheric transmittance in typical weather.3. The small spot adjustable system for Gaussian beam in space is presented based on atmospheric transmittance measurement principle and long-distance. The radius of beam can be adjustable within a certain size at a certain distance by changing the position of primary and secondary mirror of the offset Cassegrain antenna. The feasibility verifies through experimental simulation, which can solve the measurements problem of long-distance atmospheric transmittance. The parameters of primary and secondary mirror for Cassegrain antenna of He-Ne laser are designed to achieve the radius of beam adjustable between40 mm and 60mm within 10 km.4. Considering the calculation method of optical depths, the slant path and solar parameters, the calculation model of atmospheric path radiation for the typical weather is proposed based on 3 to 5 micron spectral wavelength of the background and the theory of atmospheric radiation. The model of atmospheric path radiation includes the model of single scattering and multiple scattering of solar radiation, the model of multiple scattering of surface thermal radiation the particles thermal radiation in the atmosphere. The simulation verifies the model correct by simulation calculation of atmospheric path radiation in typical weather.5. The models of atmospheric radiation transmission for the typical weather in this paper are verified by simulation. The simulation results are analyzed under the premise for keeping the inputting parameters the same for the model of this paper and PcModWin software. The errors are calculated compared to the standard value which is calculated by PcModWin software. Based on error simulation calculations of different wave number and different weather,the maximum relative error of the atmospheric transmittance is 3.846%, and The maximum relative error of the atmospheric path radiation is 5.011% for the typical weather.that proves the validity of the model.更多还原