【摘要】 基于可调谐二极管激光吸收光谱（Tunable Diode Laser Absorption Spectroscopy,TDLAS）技术的气体浓度测量系统通常以吸收光谱的归一化二次谐波信号反演气体浓度。然而以常用的数字锁相技术提取归一化二次谐波信号的方法消耗资源多、计算量大。为简化计算量,一种基于广义级数展开快速拟合的方法被提出,首先测量激光器的入射平均光强,结合光强调制系数计算线型函数及其平方项的傅里叶展开系数,即可拟合出归一化二次谐波信号。构建了CO₂气体吸收光谱检测实验,实验测试及仿真计算结果表明:采用本文方法拟合的结果与通过数字锁相技术实测的信号之间最大相对误差仅为2‰,计算消耗的时间却远小于后者,简化了系统资源,有利于TDLAS技术气体浓度测量系统的小型化、数字化。更多还原

【Abstract】 In gas concentration measurement system based on TDLAS technology,gas concentration is usually obtained by the inversion of the normalized second harmonic signal of absorption spectrum.This normalized second harmonic signal is commonly extracted using digital phase-locking technique which has problems including high requirement of memory and calculation.For simplification,a fast fitting method based on generalized series expansion was proposed.By measuring the average incident intensity and then calculating the Fourier expansion coefficient of the linear function and its square term by considering the modulation coefficient of optical intensity,the normalized second harmonic signal can be optained quickly.By the demonstration of CO₂ gas absorption spectrum experimental measurement and its relative numerical simulation based on our method,we showed that the maximum relative error between the normalized second harmonic signal fitted by the generalized series expansion method and the measured signal by the digital phase lock technology is 2%c,and the consumption of its computation time is much less than the digital phase locking method.This method may be advantageous to the miniaturization and digitization of gas concentration measurement system based on TDLAS.更多还原