一种用于一次谐波背景消除与基线校正的新型方法

摘要

针对可调谐半导体激光吸收光谱一次谐波信号中具有背景信号及较大的基线信号,提出一种新型的背景消除与基线校正的处理方法.分析了一次谐波背景中的激光器相关强度调制信号,电子学噪声和光学干涉条纹,采用无吸收谱线区域检测谐波方法消除背景信号.给出了激光器不同工作温度时的电流和强度之间的关系曲线,由此设计出消除背景后剩余基线的校正方法.文中给出了背景搜索方法的原理以及LabView软件流程图.设计了检测氟化氢气体的实验系统,根据谱线选取原则确定吸收谱线为1312.59 nm,设置激光器的工作温度为27.0◦C,对应的背景温度为30.2◦C.一次谐波信号经过背景消除和基线校正后,信号的畸变得到明显改善,基线得到校正,验证了该方法在激光器其他工作温度(26.7-27.2)是有效的,并对HF气体浓度精度的改善进行了定量分析,为一次谐波信号的后续处理提供了方便.%A new method of background elimination and baseline correction is proposed, since there are background signal and larger baseline signal in the first harmonic (1f) of the tunable diode laser absorption spectroscopy (TDLAS). The laser-associated intensity modulation signal, electronic noise, and optical interference fringes of the 1f background are analyzed. Harmonic detection in none absorption spectral region (HDINASR) is used to eliminate the background signal. Then the relationship curve between current and intensity is given in different operating temperatures to design a remaining baseline correction method after eliminating the background. The principle of background signal searching and the LabView software flow chart are also given. The TDLAS experimental system is designed to detect hydrogen fluoride (HF) gas. According to spectral line selection principle, the absorption line -1312.59 nm is selected, whose operating temperature is set at 27.0 ◦C and the background temperature is set at 30.2 ◦C. After eliminating the background and correcting the baseline, signal distortion is significantly improved and baseline is corrected. Then it is verified that the method is valid at other operating temperature of the laser (26.7-27.2). And the improvement of HF gas concentration is quantitatively analyzed. It is convenient for the subsequent processing of 1f signal.