调制噪声下激光检测气体吸收光谱信号处理研究

Data Processing of Direct Absorption Spectroscopy for Laser Gas Detection under Modulated Noise

为减小调制噪声背景的干扰,提出了直接吸收光谱激光检测气体浓度反演的三级卷积降噪信号处理方法.以谱线6 612.939cm-1附近氨气分子吸收为例,分析了该降噪方法对氨气浓度反演的有效性.实验结果表明,经三级卷积降噪后的氨气原始吸收谱线信号整体均方根误差由初始8.53降至1.01,基线扣除归一化得到的氨气光谱吸收率谱线信噪比提高3.3倍;连续5次测量浓度5%标准氨气,反演浓度值平均偏差为0.0743%,相对标准偏差为1.4%,优于原始吸收谱线信号的小波降噪和不降噪处理反演值.采用三级卷积降噪方法预处理原始吸收谱线信号,提高了气体浓度反演精度,可为工业过程高浓度气体激光在线检测提供参考.

In order to reduce interference of modulation noise, a three stages Savitzky-Golay denoising method was proposed applied to the gas concentration inversion based on direct absorption spectroscopy laser detection. Taking near 6 612.939 cm -1 absorption line of NH 3 molecular as a test object, the experiment results show that the root mean square error of NH 3 original absorption spectrum signal was decreased from 8.53 to 1.01 by three stages Savitzky-Golay denoising method, the SNR of NH 3 absorbance profile was increased by 3.3 times;5% standard NH 3 was measured five times in succession, which the average deviation of inversion value was 0.0743%, and the relative standard deviation was 1.4%. The inversion value was better than that of db6 wavelet denoising and non-denoising. The accuracy of gas concentration inversion can be improved when the original absorption spectrum signal was processed by three stages Savitzky-Golay denoising, which can provide reference for the on-line laser detection of high-concentration industrial gas.