随着社会生产力的迅猛发展，人们对能源及其生产原料的需求日益增加。在工业生产和日常生活的各个环节，都会发生有毒有害气体泄漏的情况，严重危害社会公共安全，造成巨量经济损失。因此，快速、准确定位泄漏源，高效检测并修复泄漏源越来越成为被社会关注的热点问题。可调谐半导体激光吸收光谱技术(Tunable Diode Laser Absorption Spectroscopy，TDLAS)因其具有高气体选择性、能够适应复杂环境、检测响应时间短等诸多优势，逐渐成为气体检测方面的先进技术。基于TDLAS技术的气体泄漏检测系统能够可视化泄漏气体羽流，定量分析泄漏气体浓度的二维分布，对于防止气体泄漏事故的发生，保障检测人员的生命安全具有重大现实意义。

在TDLAS气体检测领域，多用采取检测局部气体浓度或路径积分上气体浓度的方式对气体泄漏情况进行分析。但这两种方式的检测区域狭小，检测维度单一，分析泄漏情况的效率较差。对于泄漏气体的可视化，由于气体扩散是迅速变化的动态过程，且要求激光二维扫描，因此缺少利用TDLAS技术实现主动式成像的方法。本文立足于直接吸收光谱法和波长调制光谱法，对经典的测量方式进行讨论和改进，提出了利用TDLAS技术可视化烟羽的一般性方法，并以甲烷为目标气体，设计了TDLAS遥测成像系统。对于不同种类的气体，只需要更换对应吸收波长的激光器即可实现成像。本论文的研究对于化石化工产业气体泄漏监测、城市管网系统泄漏点位的定位和修复、测量有毒有害气体排放率等领域具有重要的研究价值和应用潜力。

全文主要研究工作如下：

1．对直接吸收光谱法进行改进，利用阶跃式波形调谐激光器输出波长，提出了快速分析气体浓度的方式，并利用LabVIEW编程语言编写阶跃信号输出程序。将二维振镜驱动和数据高速采集结合，实现激光扫描点位和浓度信息的时空同步，每2ms即可获得一次浓度信息。在实验室内对100%浓度甲烷气体泄漏完成动态测量，成像像素点个数为500，每秒能够得到一次二维成像情况，并对成像后的结果进行插值处理，提高图像分辨率。模拟不同浓度的甲烷气体泄漏，并在完成成像实验，探究成像系统对气体浓度的响应情况，在甲烷气体浓度为10%以上时具有较好的成像质量。进行室外遥测实验，讨论成像系统的最大遥测距离，当遥测距离小于40.89米时能够保证成像质量。

2．基于“2f/1f”谐波检测理论，采用“非扫描”的方式，只在气体吸收谱线的中心波长处叠加高频正弦信号，调制激光输出波长，提出了波长调制光谱技术的气体浓度快速分析方法，并应用于可视化气体羽流。分析一个像素点的气体浓度时间为10ms，像素点个数为500时，5s可完成一次二维分布成像。在实验室内对甲烷气体泄漏进行动态测量，并完成浓度响应实验。甲烷浓度为5%时依旧可以准确成像。实验室外最远实现了在50.54米的遥测距离下气体成像。

3．对成像系统进行优化，阐述了激光在非合作表面的反射方式，对于不同的反射方式，分别从理论上分析了不同条件下光电探测器接收到的光强信号强度，为成像系统的优化提供了理论支持。选择微棱镜反射表面和玻璃微珠反射表面进行了遥测实验，在直接吸收法下，最大遥测距离分别为45.44米和20.02米。对于波长调制法，最大遥测距离分别为77.18米和30.34米。对比本论文使用的三种非合作表面，并分析优缺点。

With the rapid development of social productivity, people's demand for energy and its production raw materials is increasing. In all aspects of industrial production and daily life, leakage of toxic and hazardous gases occurs, seriously jeopardizing social public safety and causing huge economic losses. Therefore, rapid and accurate localization of leakage sources, efficient detection and repair of leakage sources are increasingly becoming challenges that are being focused on by the society. Tunable Diode Laser Absorption Spectroscopy (TDLAS) has become an advanced technology in the field of trace gas detection due to its advantages of high selectivity, good environmental adaptability, high measurement accuracy and fast response. The gas leakage monitoring system based on TDLAS technology can visualize the leaking gas plume and quantitatively analyze the two-dimensional distribution of the leaking gas concentration, which is of great practical significance for preventing gas leakage accidents and safeguarding the life and safety of the inspectors.

In the field of TDLAS gas detection, the gas leakage situation is detected in the way of detecting the local gas concentration or detecting the gas concentration on the path integral. However, the detection area is narrow, the detection dimension is single, and the efficiency of analyzing the leakage situation is poor. For the visualization of leaking gas, since gas diffusion is a rapidly changing dynamic process and requires two-dimensional laser scanning, there is a lack of active imaging methods using TDLAS technology. Based on direct absorption spectroscopy and wavelength modulation spectroscopy, this thesis analyzes and improves the classical measurements, proposes a general method to visualize the plume using TDLAS technology, and designs a TDLAS telemetry imaging system using methane as the target gas. For different kinds of gases, only the lasers with corresponding absorption wavelengths need to be replaced to realize the imaging. The research in this thesis has important research value and application potential in the fields of gas leakage monitoring in the fossil chemical industry, locating and repairing leakage sites in urban pipeline network systems, and measuring the emission rate of toxic and hazardous gases.

The main research work in the full thesis is as follows:

1. Improvement of the direct absorption spectrometry method. Using the step waveform to tune the output wavelength of the laser, a fast way to analyze the gas concentration is proposed, and the step signal output program is written using the LabVIEW programming language. The combination of two-dimensional galvanometer drive and high-speed data acquisition realizes the temporal and spatial synchronization of laser scanning points and concentration information, and the concentration information can be obtained once every 2ms. Dynamic measurement of 100% concentration methane gas leakage was accomplished in the laboratory with the number of imaging pixel points of 500, which can obtain a 2D imaging situation once per second, and interpolation of the result after imaging was performed to improve the image resolution. Imaging measurements of methane gas leaks of different concentrations were performed to investigate the imaging system's response to the gas concentration, and the imaging quality was better when the methane gas concentration was 10% or more. The telemetry distance of the imaging system was analyzed outside the laboratory, and the imaging quality was guaranteed when the telemetry distance was less than 40.89 meters.

2. Based on the "2f/1f" harmonic detection theory, a "non-scanning" method is adopted to superimpose a high-frequency sinusoidal signal at the center wavelength of the gas absorption line to modulate the output wavelength of the laser, and a rapid analysis method of gas concentration by wavelength modulation spectroscopy is proposed and applied to visualize the gas plume. analysis method and applied to visualize the gas plume. The time to analyze the gas concentration of one pixel point is 10ms, and when the number of pixel points is 500, a two-dimensional distribution imaging can be completed in 5s. Dynamic measurements of methane gas leakage were performed in the laboratory and concentration response experiments were completed. The methane concentration of 5% can still be accurately imaged. Outside of the lab, gas imaging was achieved at a telemetry distance of up to 50.54 meters.

3. Optimization of the imaging system. The reflection mode of laser light on non-cooperative surfaces was described, and for different reflection modes, the signal intensity of light intensity received by photodetectors under different conditions was analyzed theoretically, providing theoretical support for the optimization of the imaging system. Microprism reflective surfaces and glass bead reflective surfaces were selected for telemetry experiments, and the maximum telemetry distances were 45.44 m and 20.02 m under the direct absorption method, respectively. For the wavelength modulation method, the maximum telemetry distances were 77.18 m and 30.34 m, respectively. Compare the non-cooperative surfaces used in this thesis and analyze the advantages and disadvantages.