调谐二极管激光吸收光谱中的若干关键技术研究

发布时间：2018-04-24 13:14

本文选题：光谱学 + 调谐二极管激光吸收光谱　；参考：《天津大学》2012年博士论文

【摘要】：调谐二极管激光吸收光谱(Tunable Diode Laser Absorption Spectroscopy, TDLAS)是通过对二极管激光器施加调谐信号实现波长扫描,获得气态物质吸收谱线从而推算其成分和状态信息的检测技术,广泛应用于工业及环境领域的气体检测中。本论文以对TDLAS技术检测性能的提高和检测范围的扩展提供技术支撑为研究目的,针对TDLAS技术系统优化和信号处理开展关键技术研究,包括系统参数优化、数据处理流程、波长对应过程以及应用技术中的计算方法。主要的工作内容包括以下四个方面: 1、系统参数优化:基于TDLAS的调制理论,对调制参数和锁相参数在系统运行中的功能和影响信号的机理进行研究。根据检测需求提取信号特征值,通过实验观察各参数变化对信号特征值的影响,总结影响规律,以此为基础给出系统在浓度和压强检测中各参数优化的依据和方法。对锁相放大器时间常数与调制参数联合影响信号进行实验观察及分析,给出在不同情况下参数选择依据和应注意的问题。 2、数据处理流程:讨论并验证TDLAS数据处理流程中各步骤的作用,针对不同信号观察处理效果。将温度调谐数据与电流调谐数据进行比较,采用数值计算方法和信号处理手段对不利于后期处理的特征加以改进,使其在形式构成和波长对应过程上与电流调谐方法一致。在特征值提取过程中,采用相邻极值点求差分柱的算法简化提取流程,评价处理结果,论证其在数据处理和读取过程中的优点以及与其他匹配检索技术结合的可能性。在吸收峰临近或重叠的情况下,以线型公式二阶导数叠加的形式拟合曲线,得到各吸收峰的数值信息。 3、波长对应过程:分析波长对应过程在压强检测中的重要性,结合激光器的静态调谐特性,研究了信号采样点在对应波长过程中的误差来源。在波长计算方式上,根据激光器工作原理,用查找对应二次拟合曲线的方法得到采样点对应的波长值,消除了调谐非线性对线形检测造成的影响。分别研究调制幅度和扫描频率对实际发射波长的影响机理,此为基础对检测信号进行了调制幅度校正和扫描频率校正,消除了不同调制参数下检测信号波长序列之间的差异,保证了信号的线形检测精度。 4、应用技术中的计算方法:在之前工作的基础上,对TDLAS系统的实际应用进行探索,针对不同需求,应用不同调谐方式和处理流程分别进行单一组分浓度检测、多组分气体检测、压强测量和长光程大气监测等实验。选择适当的分析手段和拟合方法对待测值进行计算,得到一套TDLAS系统实际应用的计算方式和优化过程,对此技术今后的应用发展起到指导作用。
[Abstract]:Tunable Diode Laser Absorption spectroscopy (TDLAS) is a technique for detecting the composition and state information of gaseous matter by applying tuning signal to the diode laser to realize wavelength scanning and to obtain the absorption line of gaseous substance. It is widely used in gas detection in industrial and environmental fields. The purpose of this thesis is to provide technical support for the improvement of TDLAS detection performance and the expansion of detection range. The key technologies of TDLAS system optimization and signal processing are studied, including system parameter optimization, data processing flow. Wavelength correspondence process and calculation method in application technology. The main areas of work include the following four areas: 1. System parameter optimization: based on the modulation theory of TDLAS, the function of modulation parameter and phase-locked parameter in system operation and the mechanism of affecting signal are studied. The characteristic value of signal is extracted according to the demand of detection. The influence of the change of parameters on the characteristic value of signal is observed experimentally, and the influence law is summarized. Based on this, the basis and method of optimizing the parameters of the system in the detection of concentration and pressure are given. The experimental observation and analysis of the combined effects of the time constant and modulation parameters of the phase-locked amplifier are carried out, and the basis for the selection of the parameters under different conditions and the problems to be paid attention to are given. 2, data processing flow: discuss and verify the function of each step in TDLAS data processing process, observe the effect of different signal processing. Comparing the temperature tuning data with the current tuning data, the numerical calculation method and the signal processing method are used to improve the characteristics which are not conducive to the later processing, so that the temperature tuning data are consistent with the current tuning method in the form composition and the wavelength correspondence process. In the process of feature extraction, the extraction process is simplified by using the algorithm of finding difference columns with adjacent extremum points, the processing results are evaluated, and its advantages in the process of data processing and reading are demonstrated, as well as the possibility of combining with other matching retrieval techniques. When the absorption peak is near or overlapping, the curve is fitted in the form of superposition of the second derivative of linear formula, and the numerical information of each absorption peak is obtained. 3, wavelength correspondence process: the importance of wavelength correspondence process in pressure detection is analyzed, and the error source of signal sampling point in the corresponding wavelength process is studied according to the static tuning characteristics of laser. In terms of wavelength calculation, according to the working principle of the laser, the corresponding wavelength values of the sampling points are obtained by searching the corresponding quadratic fitting curve, which eliminates the influence of tuning nonlinearity on the linear shape detection. The influence mechanism of modulation amplitude and scanning frequency on the actual emission wavelength is studied respectively. Based on this, the modulation amplitude correction and scanning frequency correction are carried out to eliminate the difference between the detection signal wavelength sequences under different modulation parameters. The linear detection accuracy of the signal is guaranteed. 4. Calculation methods in application technology: on the basis of previous work, the practical application of TDLAS system is explored. According to different requirements, single component concentration detection and multicomponent gas detection are carried out according to different tuning methods and processing flow. Pressure measurement and long-path atmospheric monitoring experiments. A set of calculation method and optimization process for practical application of TDLAS system are obtained by selecting appropriate analytical means and fitting method to calculate the measured values, which will play a guiding role in the development of this technology in the future.
【学位授予单位】：天津大学
【学位级别】：博士
【学位授予年份】：2012
【分类号】：R318.51

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