吸收光谱线二次谐波的频率分解和SG滤波复合降噪  

Denoising of Second Harmonic Signals of the Absorption Spectrum Using the Frequency Decomposition Combined With the Savitzky-Golay Filtering

作　　者：涂兴华[1] 栾小晨 王战 TU Xing-hua;LUAN Xiao-chen;WANG Zhan(College of Electronic and Optical Engineering&College of Flexible Electronics(Future Technology),Nanjing University of Posts and Telecommunications,Nanjing 210023,China)

机构地区：[1]南京邮电大学电子与光学工程学院,柔性电子(未来技术)学院,江苏南京210023

出　　处：《光谱学与光谱分析》2025年第5期1209-1216,共8页Spectroscopy and Spectral Analysis

基　　金：国家自然科学基金项目(62374092)资助。

摘　　要：针对微弱气体吸收光谱线的二次谐波信号检测过程中存在的噪声干扰问题,提出利用频率分解(FD)和Savitzky-Golay滤波(SG滤波)相结合方法(简记为FD-SG滤波)对含噪信号进行降噪。频率分解是一种用于分解复杂信号的数学方法,其优点是能够自主选择分解个数或者采用非递归方式求解。SG滤波能够对成组的数据进行处理,在维持信号变化趋势和宽度的同时提高数据的精准度。首先对含噪信号进行频率分解,再进行SG滤波二次降噪处理,最后将滤波后的有效层分量进行重构,得到降噪后的二次谐波信号。讨论分析了频率分解后各层分量的分布情况,验证有效信号主要分布在第一层分量内,并且仍会含有残余噪声;通过构建调节因子P选取最优的SG滤波框长,使得有效层残留噪声得到有效去除。针对空气中的CO_(2),采用1578.222 nm的吸收光谱线进行实验,结果显示二次谐波信号中存在大量噪声,尤其在扫描周期交界处出现大尖峰噪声。通过拟合曲线扣除处理和频率分解,发现大尖峰噪声未明显减弱。随后结合SG滤波处理并比较了二次谐波与大尖峰峰值的关系,结果表明SG滤波能够有效减弱大尖峰噪声,选择合适滤波框长即可得到较为理想的降噪效果。在对人体呼出CO_(2)的二次谐波信号进行检测时,发现吹气引起的湍流导致信号幅值增大并抖动,通过FD-SG滤波处理成功抑制了噪声,恢复出较为平滑的二次谐波信号。验证了该算法对实际微弱气体检测的二次谐波信号降噪的性能,在实现噪声抑制及大尖峰结构噪声的减弱方面表现出较突出的优势。这对微弱气体检测方面提高信号质量和系统精度有积极意义。To address the issue of noise interference in the detection of second harmonic signals from weak gas absorption spectral lines,this paper proposes a method combining frequency decomposition(FD)and Savitzky-Golay filtering(SG filtering),referred to as FD-SG filtering,to denoise noisy signals.Frequency decomposition is a mathematical method used to decompose complex signals,with the advantage of independently selecting the number of decompositions or solving non-recursively.SG filtering processes groups of data,improving data accuracy while maintaining signal trend and width.The proposed method first applies frequency decomposition to the noisy signal,followed by SG filtering for secondary denoising.Then,it reconstructs the denoised second harmonic signal from the filtered effective components.After frequency decomposition,the distribution of each component is analyzed,confirming that the effective signal mainly resides in the first component but still contains residual noise.By constructing an adjustment factor P to select the optimal SG filter length,the residual noise in the effective component is effectively removed.In experiments with CO_(2) in the air using an absorption spectral line at 1578.222 nm,significant noise was found in the second harmonic signal,especially with large spike noise at scan cycle junctions.Fitting curve subtraction and frequency decomposition showed limited noise reduction for large spikes.The combination of SG filtering and the relationship between the second harmonic and spike peak values demonstrated that SG filtering effectively reduces spike noise,achieving ideal denoising with the appropriate filter length.When detecting the second harmonic signal of exhaled CO_(2),the turbulence caused by exhalation increased and jittered the signal amplitude.FD-SG filtering successfully suppressed the noise,yielding a smoother second harmonic signal.This verifies the algorithm's effectiveness in denoising second harmonic signals for practical weak gas detection,showing significant advantages in

关 键 词：可调谐二极管激光吸收光谱 二次谐波 波形恢复 调节因子 

分 类 号：O433.1[机械工程—光学工程]