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为了提取淹没在噪声中的弱吸收信号,对波长调制光谱测量中的相敏检测技术进行研究,提出了一种数字化相敏检测实现方案。采用正交矢量型结构实现相敏检测过程,通过硬件电路设计和上位机程序编写,完成吸收信号谐波分量的获取。对空气中的O2进行检测,针对O2位于764nm附近的一对吸收谱线,成功提取了吸收信号的二次谐波分量。结果显示,系统的检测极限体积分数为0.50%(光程为1m)。
In order to extract the weakly absorbed signals submerged in the noise, the phase sensitive detection technology in wavelength modulation spectroscopy is studied, and a digital phase sensitive detection scheme is proposed. Orthogonal vector type structure is used to realize the phase sensitive detection process. Through the hardware circuit design and PC programming, the acquisition of the harmonic components of the absorption signal is completed. The detection of O2 in the air, for the O2 located in the vicinity of 764nm a pair of absorption lines, the successful extraction of the second harmonic component of the absorption signal. The results show that the detection limit volume fraction of the system is 0.50% (optical path is 1m).