对数变换—波长调制光谱在气体检测中的应用

发布时间：2018-05-13 21:04

本文选题：红外吸收光谱 + 波长调制　；参考：《红外与激光工程》2017年02期

【摘要】：为了提高痕量气体检测的稳定性并扩大动态范围,引入对数变换方法和差分检测电路,对常规波长调制光谱技术进行了改良。在使用锁相放大器提取与气体吸收相关的谐波信号之前,由自制的接收器完成对数变换和差分检测功能。通过对数变换,使激光强度调制与气体吸收引起的光功率衰减量实现了分离,再利用差分检测消除前者。受益于此双管齐下的策略,理论上可以捕捉吸收光谱的任意阶谐波分量,并且免受剩余幅度调制和谐波畸变的影响。为了验证理论,对NH3的P(6)吸收谱线的二次谐波进行了采集。在296 K的环境温度、1.01×105 Pa的总压力和24.5 cm的有效光程下,假设信噪比降低为1时推导得到的理论检测下限为0.7 ppm(1 ppm=10-6)。以上结果表明该方案是痕量气体检测应用的一种理想选择。
[Abstract]:In order to improve the stability of trace gas detection and expand the dynamic range, the logarithmic transformation method and differential detection circuit were introduced to improve the conventional wavelength modulation spectroscopy. Before the phase-locked amplifier is used to extract the harmonic signal associated with gas absorption, the logarithmic transformation and differential detection are performed by the self-made receiver. By logarithmic transformation, the optical power attenuation caused by laser intensity modulation and gas absorption is separated, and the former is eliminated by differential detection. With this two-pronged approach, we can theoretically capture any harmonic component of the absorption spectrum and avoid the residual amplitude modulation and harmonic distortion. In order to verify the theory, the second harmonic of the absorption line of NH3 is collected. At 296K ambient temperature of 1.01 脳 105Pa and effective light path of 24.5cm, the theoretical detection limit of 0.7 ppm(1 ppmg 10-6m is deduced if the SNR is reduced to 1. The results show that this scheme is an ideal choice for trace gas detection.
【作者单位】：内蒙古民族大学物理与电子学院;吉林大学集成光电子国家重点联合实验室;
【基金】：科技部支撑计划(2013BAK06B04)
【分类号】：O433

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