基于弹光调制的甲醛气体浓度检测系统的研究

由于室内甲醛超标造成的环境污染日益增多，为了快速、准确地对室内空气中甲醛气体的浓度进行定量分析，设计了基于弹光调制的甲醛气体浓度检测系统，由红外光源、滤光片、弹光调制器、红外探测器等构成，由弹光调制器控制弹光晶体折射率周期性变化，折射率造成的光程变化提供了反演光谱分布函数的光程差。通过HITRAN光谱数据库推导了系统可获得的光程差函数。实验采用红外光源与窄带滤波片结合，中心波长透过率在90%以上，采用硒化锌晶体作为弹光调制晶体，系统的驱动频率为100 kHz。对三种不同环境下不同位置分别采集十组样气进行分析，同时采用标准光谱仪和本系统进行甲醛气体浓度检测。实验结果显示，当甲醛气体浓度较高时，系统性能良好;当甲醛气体浓度较低时，系统信噪比下降，检测精度略有降低，但仍能满足设计要求。

Research on Formaldehyde Concentration Detection System Based on Photo-Elastic Modulation

There is a growing number of environmental pollution caused by excessive indoor formaldehyde, and in order to quickly and accurately quantify the concentration of formaldehyde gas in indoor air, a system for detecting the concentration of formaldehyde gas based on photo-elastic modulation was designed. It consists of the infrared light source, filters, elastic light modulator, and infrared detectors, and photo-elastic crystal refractive index of cyclical changes was controlled by elastic light modulator. Refractive index caused by the changes in the optical path provided a spectrum distribution function of the optical path difference. Optical path difference function of the system was derived through the HITRAN spectral database. Experiments were carried out using infrared light source combined with narrow band filters, and the transmittance of the center wavelength was more than 90%. Photo-elastic crystal is ZnSe crystal as photo-elastic light modulator, and the drive frequency of the system is 100 kHz. For three different environments at different locations, 10 groups of sample gas were collected for analysis, and the concentration of formaldehyde gas was detected using standard spectrometer and the system for comparing the test data. Experimental results show that when the concentration of formaldehyde gas is high, the system performance is good; When the concentration of formaldehyde gas is low, the signal-to-noise ratio of the system is decreased, and the detection accuracy is slightly reduced, but it still meets the design requirements.