新型合成波长干涉术提取尾气成分体积分数的理论与实验研究

当前机动车尾气排放超标检测方法还不能满足非接触式和高准确度的应用要求。多类气体按不同比例混合后会引起等效折射率改变，进而导致激光光程在传播过程中会发生变化；同时我们研究表明，结合激光相干原理和硬件跟踪技术的位移检测方法，可有效解决光测方法中高精度和大量程难以兼顾的问题。因此在本研究中，我们提出基于合成波长干涉实现混合气体体积分数检测的技术方案。首先拟通过多激光器级联的方式实现合成波长，可解决激光相干方法可测范围小的问题；之后拟通过外差干涉技术进行双通道的光路结构设计，可解决多波长测量方法精度低的问题；然后拟基于图像分析技术结合硬件跟踪测量的思想，实现动态相干信号相位变化量的快速检测；最终围绕多物理量开展探索实验，实现光程差与混合气体体积分数的映射关系标定。本项目将结合仿真和实验的方式来探索技术方案的可行性，为城市尾气排放检测提供科学参考。

The current detection methods on vehicle exhaust emissions cannot meet the applicable requirements of non-contact and high-accuracy measurement. In accordance with the physical property that the refractive index changes after the mixture of different kinds of gases with different ratios and thus causes the changes of laser optical path. Additionally, our previous research work showed that a detection method based on the principle of laser coherence and the idea of displacement tracking using hardware devices could effectively solve the optical measurement contradiction between high precision and large range. Therefore, in this research, a technical solution is proposed by the way of detecting volume fraction of mixed gas based on the optical measurement method. First the way of multiple-laser cascading is employed for the synthetic wavelength to solve the problem of laser coherent methods with small measurement range. Afterwards the dual-channel optical path structure is designed using the heterodyne interference technique to solve the problem of multi-wavelength measurement methods with low accuracy. Then based on the idea of image analysis techniques and hardware tracking measurement, the rapid detection on phase change of dynamic coherent signal will be performed. Finally, exploratory experiments considering multiple physical quantities will be carried out to realize the calibration of the relations between the optical path difference and the mixed gas volume fraction. This project aims to provide scientific solutions for urban exhaust emission detection, whose feasibility work of the technical framework will be explored by the ways of simulation and experiment.