基于TDLAS的红外湿度检测中的小波去噪实验研究  

Experimental research on wavelet denoising in infrared humidity detection based on TDLAS technique

作　　者：叶玮琳[1] 郑传涛[2] 王一丁[2] 

机构地区：[1]汕头大学工学院,广东汕头515063 [2]吉林大学电子科学与工程学院集成光电子学国家重点联合实验室吉林大学实验区,吉林长春130012

出　　处：《光电子．激光》2013年第1期104-111,共8页Journal of Optoelectronics·Laser

基　　金：国家科技支撑计划(2013BAK06B04);国家自然科学基金(61077074);吉林省科技发展计划(20090422);汕头大学科研启动基金(NTF12022);汕头大学青年科研基金(YR12005)资助项目

摘　　要：为了有效抑制可调谐二极管激光吸收光谱法(TDLAS)进行红外湿度检测中的噪声,采用多阈值小波去噪方法对测量通道和参考通道间的差分信号做降噪处理,然后基于数字锁相放大技术从去噪后的差分信号中提取二次谐波信号,最终根据谐波信号的幅值大小确定湿度数值。给出了多阈值小波去噪算法的流程,并做了实验验证。分析显示,本文方法可有效抑制噪声的影响,在极低湿度条件下仍可较好地提取出二次谐波信号。利用制作的湿度检测系统,结合配备的密闭湿度环境,开展了检测实验。结果表明,采用小波去噪后,检测下限可由0.2%降至0.08%,极低湿度条件下(0.2%)的测量误差可由48%降至7.9%,其它浓度下的测量误差小于5%。同时,由于噪声被很好抑制,检测系统的测量标准差小了1个量级,从而改善了系统稳定性。本文的小波去噪方法也可用于具有类似机理的红外气体检测系统中以改善性能指标。In order to suppress the influence of noise introduced in infrared humidity detection based on tunable diode laser absorption spectrum （TDLAS） technique, multi-threshold wavelet denoising is firstly introduced on the differential signal between detection channel and reference channel, then the second-order harmonic component is extracted from the differential signal through the digital phase lock-in amplifier,and finally the humidity value is determined according to the amplitude of the second-order harmonic component. The filtering procedure of multi-threshold wavelet denoising is proposed, and related experimental verification is carried out on the algorithm. The analysis results indicate that this technique can effectively suppress noises, and the second-order harmonic component can still be well extracted under extremely low humidity. By using the developed detection system and the prepared hermetic environment,the humidity measurement is performed thoroughly. Experimental results show that, by using multi-threshold wavelet denoising, the detection limit can be dropped from 0.2% to 0.08 %, the detec tion error under the humidity of 0.2 %can be decreased from 48 % to 7.9%, and that under other humidity is less than 5%. Because the noise is well suppressed through wavelet denoising,the standard deviation of the system is minimized by one order of magnitude, and the detection stability is therefore improved. The wavelet denoising technique can also be adopted in other infrared detection systems withsimilar principle for enhancing performance.

关 键 词：红外检测 湿度测量 小波去噪 可调谐二极管激光吸收光谱法(TDLAS) 

分 类 号：TH83[机械工程—仪器科学与技术]