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III
密集光斑型 Herriott 气室的研制与应用
摘要
本论文选题来源于国家重点研发计划课题—多气体交叉干扰抑制与高灵敏
气体检测技术(课题编号:2021YFB3201903)。
气体传感器在环境、工业、医学、农业和畜牧业等领域都有着广泛的应用。
常用的气体检测技术中,可调谐二极管激光吸收光谱技术(Tunable Diode Laser
Absorption Spectroscopy,TDLAS)具有选择性强、灵敏度高和稳定性好等优点。
对于 TDLAS 传感器来说,作为关键光学模块的气室决定着传感器的性能。为了
提高气室的光程容积比,提高传感性能,本论文针对密集光斑型赫里奥特
(Herriott)气室研究了以下内容:
根据红外吸收光谱原理,实现单位体积内的长吸收光程是提高气体检测系
统性能的重要手段。本论文使用 Tracepro 软件与 MATLAB 软件仿真 Herriott 气
室光路,通过优化镜面间距、入射位置和入射光角度等光学参数,得到了多种
密集光斑分布和光路结构,详细分析了光路的变化规律,量化对比了气室的光
程、光程容积比、表面积等参数。
基于仿真的密集光斑型光路结构,研制了长光程气室和新型小体积密集光
斑型气室。长光程气室的光路仿真实现了 432 次的反射次数与 85 的光程容积比。
利用设计的气室结构,进行了光路调试实验。对气室进行光程标定,测定光程
为 8.57 m,与理论吻合。新型小体积密集光斑型气室的长、宽、高分别为 7.4
cm、4.2 cm 和 3.8 cm,体积为 119 cm
3
,内容积为 38 mL。对小体积气室进行光
程标定,测定光程为 6.2 m。
结合波长调制光谱(Wavelength Modulation Spectroscopy,WMS)技术,采
用所研制的两种气室分别建立了乙炔(C
2
H
2
)气体传感器系统并测试了传感性
能。基于长光程气室的 C
2
H
2
传感器采用中心波长为 1533 nm 的分布反馈
(Distributed Feedback,DFB)激光器。根据艾伦偏差的计算结果,当积分时间
为 0.2 s 时,C
2
H
2
检测下限为 0.02 ppm(part per million,百万分之一),当积分
时间为 63.8 s 时,C
2
H
2
检测下限降低到 1.4 ppb(part per billon,十亿分之一)。
IV
传感器的响应时间为 94.7 s。基于小体积密集光斑型气室的 C
2
H
2
传感器采用中
心波长为 1534 nm 的 DFB 激光器。根据艾伦偏差的计算结果,当积分时间为 0.2
s 时,C
2
H
2
检测下限为 7.8 ppm,当积分时间为 50.2 s 时,C
2
H
2
的检测下限降低
到 0.32 ppm。传感器的响应时间为 3.8 s。
创新点如下:
建立了密集光斑型 Herriott 多通池的仿真模型,研制了光程容积比达 85、
容积仅为 38 mL 的两种气室,通过乙炔检测实验,验证了气室的功能。
关键词:
红外光谱,TDLAS,Herriott 气室,密集光斑型多通池,乙炔气体检测
V
Development and application of dense-spot pattern
Herriott gas cell
Abstract
The subject of this thesis comes from the National Key Research and Development
Plan : Multi-gas Cross Interference Suppression and Highly Sensitive Gas Detection
Technology (project number: 2021YFB3201903).
Gas sensor is widely used in the fields of environment, industry, medicine,
agriculture, and animal husbandry. Among commonly used gas detection technologies,
Tunable Diode Laser Absorption Spectroscopy (TDLAS) has outstanding advantages
of strong selectivity, high sensitivity, and good stability. The gas cell is the key optical
module of the TDLAS system, which determines the performance of the sensor. In order
to improve the optical path volume ratio of the gas cell and optimize the performance
of the gas sensor, the following studies on dense-spot pattern Herriott gas cell were
carried out in this thesis:
According to the principle of infrared absorption spectrum, improving the
absorption path per unit volume of gas cell is an important way to optimize the
performance of the gas sensor. In this thesis, Tracepro and MATLAB were used to
simulate Herriott gas cell. Optical parameters such as mirror spacing and incident
position were optimized, and a variety of dense spot distributions and light path
structures were obtained. The change rule of optical path structure was analyzed in
detail. The optical path, optical path volume ratio, surface area and other parameters of
the gas cell are quantified and compared.
Based on simulation results of the optical path structure, a long optical path gas
cell and a new small volume dense spot gas cell was designed. The long optical path
gas cell has realized 432 reflections and 85.0 optical path volume ratio. Using the
designed gas cell structure, optical path debugging experiments were carried out. The
optical path of the gas cell was calibrated, and the optical path is 8.57m, which is
VI
consistent with the theory. The length, width and height of the new small volume dense
spot pattern gas cell are 7.4cm, 4.2cm, and 3.8 cm, the volume is 119 cm
3
and the
content volume is 38 mL. The optical path of the small volume gas cell was calibrated,
and the measured optical path is 6.2 m.
Combined with the wavelength modulation spectroscopy (WMS) technology,
acetylene (C
2
H
2
) gas sensor system was built using two developed gas cells and their
sensing performance was tested. The C
2
H
2
sensor based on a long optical path gas cell
used a distributed feedback (DFB) laser with a central wavelength of 1533 nm.
According to the calculation results of Allan deviation, when the averaging time is 0.2
s, the limit of detection of C
2
H
2
is 0.02 ppm (part per million), and when the averaging
time is 63.8 s, the limit of detection of C
2
H
2
is reduced to 1.4 ppb (part per billion). The
response time of the sensor is 94.7 s. The C
2
H
2
sensor based on a small volume dense
spot type gas cell used a DFB laser with a central wavelength of 1534 nm. According
to the calculation results of Allan deviation, when the averaging time is 0.2 s, the limit
of detection of C
2
H
2
is 7.8 ppm, and when the averaging time is 94.7 s, the limit of
detection of C
2
H
2
is reduced to 0.32 ppm. The response time of the sensor is 3.8 s.
The innovative points are as follows:
A simulation model of a dense spot type Herriott multi-pass cell was bulit, and two
types of gas cell with an optical path volume ratio of 85 and a volume of only 38 mL
were developed. The function of the gas cell was verified through acetylene detection
experiments.
Keywords:
TDLAS, Herriot gas cell, Dense spot type multi-pass cell, Acetylene gas detection
目 录
第一章 绪论............................................................................................... 1
1.1 研究的背景与意义 ........................................................................... 1
1.2 气体检测技术概述 ........................................................................... 2
1.2.1 催化燃烧法 ................................................................................. 2
1.2.2 气相色谱法 ................................................................................. 2
1.2.3 气敏法 ......................................................................................... 3
1.2.4 声波法 ......................................................................................... 3
1.2.5 光谱法 ......................................................................................... 3
1.3 多通池研究现状 ............................................................................... 4
1.4 论文的主要研究内容及创新点 ...................................................... 8
1.4.1 主要研究内容 ............................................................................. 8
1.4.2 创新点 ......................................................................................... 9
第二章 红外激光吸收光谱技术原理 .................................................... 10
2.1 分子吸收光谱技术 ......................................................................... 10
2.2 Lambert-Beer 定律 ......................................................................... 12
2.3 直接吸收光谱技术的原理与仿真 ................................................ 12
2.3.1 直接吸收光谱技术的原理 ....................................................... 12
2.3.2 直接吸收光谱技术的仿真 ....................................................... 12
2.4 波长调制光谱技术的原理与仿真 ................................................ 14
2.4.1 二次谐波检测的原理 ............................................................... 15
2.4.2 正交锁相放大器的原理 ........................................................... 16
2.4.3 波长调制光谱技术的仿真 ....................................................... 17
2.5 Herriott 气室光线传输矩阵 ........................................................... 19
2.6 本章小结 ......................................................................................... 24
第三章 密集光斑型 Herriott 气室设计 ................................................ 26
3.1 Herriott 气室设计与仿真 ............................................................... 26
3.1.1 基于 Tracepro 的光路设计与分析 ........................................ 26
3.1.2 基于 MATLAB 软件的光路设计与分析 .............................. 30
3.2 Herriott 气室光路搭建与调试 ....................................................... 32
3.3 Herriott 气室性能对比 ................................................................... 33
3.4 章末小结 ......................................................................................... 35
第四章 密集光斑型 Herriott 气室研制 ................................................ 36
4.1 长光程 Herriott 气室研制与调试 ................................................ 36
4.1.1 光路设计 ................................................................................... 36
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