激光吸收光谱技术中扫描频率的选择

Scanning Frequency Optimization of Laser Absorption Spectroscopy

基于可调谐半导体激光吸收光谱(TDLAS)技术的传感器系统性能受激光器特性、探测器特性、调制参数、激光器控制电路和信号采集电路等的影响。激光器和探测器特性与当前的生产制造水平密切相关,对于直接吸收法,调制参数主要指扫描幅度和扫描频率,而扫描幅度的确定以得到完整吸收信号为准。对扫描频率的选择和优化进行了详细的讨论。在一定的理论基础上通过实验分别观察各扫描频率对直接吸收信号的影响,通过分析检测信号的特征,如幅值、半峰全宽、调整的判定系数、信噪比、积分吸光度及偏差等得出其变化规律,总结出扫描频率的选择依据。该研究为TDLAS直接吸收法中扫描频率的确定提供了实验依据。

The system performance of tunable diode laser absorption spectroscopy （TDLAS） is affected by the characteristics of laser, the characteristics of detector, the modulation parameters, control circuit of laser and acquisition circuit of signal, etc. The characteristics of laser and detector are determined by the level of present production-manufacturing. For direct absorptive method, the modulation parameters contain scanning amplitude and scanning frequency. Scanning amplitude is adjusted to obtain complete absorption signal. The optimization and selection of scanning frequency are discussed in detail. Aiming at this problem, the influence of scanning frequency on direct absorption signals is observed by experiment based on a certain theory in the present paper, and the basis and method of scanning frequency optimization are summarized by analyzing the signal characteristics including amplitude, peak width, adjusted coefficient determination, signal-to-noise ratio and integrated absorbance, etc. The result of the experiment provides a definite basis for the selection of scanning frequency in TDLAS direct absorptive method.