为了消除激光吸收光谱信号中噪声对分析结果的影响, 提出了基于小波变换的阈值去噪方法。利用气体分子的直接吸收光谱信号,结合MATLAB软件进行仿真实验, 深入对比分析了阈值方法、分解层数和小波基函数类型对降噪效果的影响,最后将获得的最佳滤波参数用于人体呼出气体的光谱信号分析中。结果表明, 小波变换去噪算法模型对呼出气体吸收光谱信号的去噪效果良好。通过选择其他波段的可调谐激光光源,即可实现对其他呼出气体成分的实时分析;量子级联激光光谱系统可广泛应用于呼出气体诊断等领域。

In order to eliminate the influence of noise in laser absorption spectral signal on analysis result, we propose a threshold denoising method based on wavelet transform. The simulation experiment is implemented with the utilization of direct absorption spectroscopy signal of gas molecules combined with MATLAB software, and the effects of threshold methods, decomposition level and wavelet function type on denoising effect are analyzed in details. Finally, the optimized filtering parameters are used to analyse the spectral signal of human expired gas in experiment. The results show that the wavelet transform algorithm developed in this study has a good denoising effect for the spectral signal. In addition, real-time analysis of the other component of expired gas can be realized by selecting different tunable laser light sources at other wavelength. The quantum cascade laser (QCL) spectroscopy system can be widely used in the field of expired gas diagnosis and other fields.