用于高精度微弱信号探测激光雷达的光机系统设计及优化

发布时间：2018-05-08 12:22

本文选题：激光雷达 + 相干测风系统　；参考：《北京理工大学》2014年博士论文

【摘要】：激光雷达是一种通过对目标反射或者散射的回波信号进行分析来反演目标特性的光学遥感技术，从激光回波中反演可以得到的信息包括光强、频率、相位、偏振及目标距离等多种。随着超短脉冲激光技术、高灵敏度的信号探测和高速数据采集技术的发展和应用，激光雷达以它较高的时空分辨率、较大的探测范围和较快的测量速度而逐渐成为一种重要的探测工具，目前已在很多领域得到应用。论文主要针对用于微弱信号探测激光雷达的光机系统设计及优化而开展研究。论文的主要内容可分为两个部分：一是针对星载的相干测风激光雷达，给出了系统光学参数的优化方案，以信噪比为基础分析计算了一套400km轨道星载相干测风激光雷达所需要的光学参数，完成了光学设计和仿真，并给出了一种机械设计方案；二是通过开展基于ICCD选通的激光诱导荧光雷达的新技术研究论证，课题组开发了一套综合技术指标在国内外具有先进性的激光诱导荧光雷达系统，在本论文中主要完成了荧光光谱仪的设计和开发，在290nm-650nm荧光光谱范围内解决了双波长探测模式下的弹性散射太强而无法探测荧光及多级衍射光谱相重合的问题。论文完成的主要创新性的工作如下： 1)在星载相干测风激光雷达系统中，提出了采用双望远镜的探测模式。针对用于单望远镜探测的大口径扫描光楔材料难以获取且价格昂贵、光学精度不高且扫描要求功率大的缺陷，提出采用双望远镜的探测模式，并在该探测模式下，以高斯模型为基础推导了系统效率、外差效率及信噪比等重要指标的表达式，得到了适用于不同轨道高度的望远镜口径、发散角、截断比等重要的光学参数。 2)在星载相干测风激光雷达系统设计中，提出采用单模光纤作为中继部件对本振光及信号进行传输。针对自由空间的光学系统对准困难及基于星载平台的测风系统难于后续维护等难题，在系统设计中采用单模光纤作为中继部件对本振光及信号进行传输，实现了基于自由空间和基于光纤的相干测风雷达系统外差效率理论的统一，并对光纤耦合的F数进行了优化计算。除此之外，在论文中还针对星载系统特有的光波往返探测系统及地表导致的滞后角问题，提出了滞后角补偿器的设计方案。 3)在满足1/10λ@2μm波前差的要求下，设计了用于400km轨道星载相干测风雷达系统的500mm口径离轴望远镜及其他的光学部件。根据优化得到的光学参数，在满足1/10λ@2μm波前差的要求下，对用于400km轨道星载相干测风雷达系统的光学系统进行了研究，设计了500mm口径离轴且无内部焦点的望远镜、对应的扩束器及耦合镜，给出了轻量化的机械设计方案，并对系统的体积、重量、总的系统效率等参数进行了仿真和计算。 4)针对激光诱导荧光雷达微弱信号采集，设计并实现了中心分辨率1.6nm，边缘分辨率2.5nm，，能够消除弹性后向散射光的的荧光光谱仪。根据荧光具有的寿命短、强度低、对探测波长敏感等特点，提出了采用ICCD进行选通探测的技术方案；而为了能够得到更多的荧光信息，设计采用266nm和355nm双波长激光进行荧光激发，并开发出了针对特定ICCD形状、特定光谱波段(290nm-650nm)并能够消除弹性后向散射光的荧光光谱仪。根据实际的组装测试结果，该荧光光谱仪中心分辨率能够达到1.6nm，边缘能够达到2.5nm，该光谱分辨率优于现有多数同类型荧光激光雷达的分辨率，最后，还利用系统对几种油质的荧光光谱进行了采集和处理，验证了此激光诱导荧光雷达系统采集物质荧光光谱的能力。
[Abstract]:The laser radar is a kind of optical remote sensing technology for inverting the target characteristic by analyzing the echo signal reflected or scattered by the target . The information obtained from the inversion of the laser echo includes many kinds of light intensity , frequency , phase , polarization and target distance . With the development and application of ultra - short pulse laser technology , high sensitivity signal detection and high - speed data acquisition technology , the laser radar becomes an important detection tool with its high space - time resolution , larger detection range and faster measurement speed , and has been used in many fields .

The paper mainly focuses on the research on the design and optimization of the optical system of laser radar for weak signal detection . The main contents of this paper can be divided into two parts : First , the optimization scheme of the system ' s optical parameters is given , based on the signal - to - noise ratio , the optical parameters needed by a set of 400km orbit satellite - borne coherent wind lidar are calculated , and a mechanical design scheme is given .
Second , by carrying out the new technical research and demonstration of laser - induced fluorescence radar based on ICCD / COP ( ICCD ) gating , a comprehensive set of laser - induced fluorescence radar systems with advanced properties at home and abroad have been developed . In this paper , the design and development of the fluorescence spectrometer are mainly completed , and the problem that the elastic scattering in the dual - wavelength detection mode is too strong to detect the coincidence of the fluorescence and the multi - stage diffraction spectrum is solved in the range of 290nm - 650 nm .

The main innovative work accomplished in this paper is as follows :

1 ) In the satellite - borne coherent wind lidar system , a detection mode is proposed , which is difficult to acquire and expensive , low in optical precision and large in scanning requirement . The detection mode is proposed . The important indexes such as system efficiency , heterodyne efficiency and signal - to - noise ratio are derived based on Gaussian model .

2 ) In the design of the satellite - borne coherent wind lidar system , this paper proposes the use of single mode fiber as the relay component to transmit the local oscillator light and signal . In the system design , a single mode fiber is used as the relay component to transmit the local oscillation light and signal , and the F number of optical fiber coupling is optimized .

3 ) Under the requirement of 1 / 10 位 @ 2渭m wave front difference , a 500mm aperture off - axis telescope and other optical components for 400km orbit satellite - borne coherent wind - measuring radar system are designed . According to the optimized optical parameters , the optical system for 400km orbit satellite - borne coherent wind - measuring radar system is studied . A 500 mm diameter off - axis telescope with no internal focal point is designed , the corresponding beam expander and coupling mirror are designed , a light - weight mechanical design scheme is given , and the parameters such as volume , weight and total system efficiency of the system are simulated and calculated .

4 ) Aiming at the weak signal acquisition of laser - induced fluorescence radar , a fluorescence spectrometer with a center resolution of 1.6 nm and an edge resolution of 2.5 nm is designed and realized .
In order to obtain more fluorescence information , the fluorescence excitation is carried out with 266 nm and 355 nm double wavelength laser . According to the actual assembly test results , the center resolution of the fluorescence spectrometer can reach 1.6 nm , the edge can reach 2.5 nm , the spectral resolution is better than the resolution of the existing majority of the same type of fluorescent laser radar , and finally , the fluorescence spectrum of the several oils is collected and processed , and the capability of the laser - induced fluorescence spectrum of the fluorescent radar system is verified .

【学位授予单位】：北京理工大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TN958.98

【引证文献】