Tunable Diode Laser Absorption Spectroscopy (TDLAS) Detection Signal Denoising Based on Gabor Transform
CUI Hai-bin1, YANG Ke1, 2, ZHANG Long1, WU Xiao-song1, LIU Yong1, WANG An1, LI Hui3, JI Min1*
1. Institute of Applied Technology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China 2. University of Science and Technology of China, Hefei 230026, China 3. Beijing Tobacco Quality Supervision & Test Station, Beijing 100029, China
Abstract：Tunable diode laser absorption spectroscopy (TDLAS) technology combined with wavelength modulation spectroscopy (WMS) technology is an important technique for trace gas detection. Detected with the lock-in amplifier, the second harmonic signal obtained after demodulation is analyzed to get the gas absorption information. However, the second harmonic signal is affected by noise which reduces the accuracy and stability of the detection system. To improve the signal to noise ratio (SNR) of the TDLAS detection system, a denoising method based on Gabor transform is proposed for second harmonic signal noise reduction. Taking the CH4 absorption spectrum at 1 653.72 nm as an example, the effectiveness of the noise reduction method is verified through simulation and experiments. The simulation results show that the signal to noise ratio for the second harmonic signal of 0 dB can be improved 15.73 dB with Gabor transform-based denoising method. Experimental results show that with the Gabor transform-based denoising method, the linear correlation coefficient r can be as high as 0.996 59 between the second harmonic peak value and the CH4 concentration in the range of 0.001%~0.02%. At the same time, the detection accuracy and stability of the system have been improved significantly.
[1] Li J, Yu B, Zhao W, et al. Applied Spectroscopy Reviews, 2014, 49(8): 666. [2] Hodgkinson J, Tatam R P. Measurement Science and Technology, 2013, 24(1): 012004. [3] Leleux D P, Claps R, Chen W, et al. Applied Physics B, 2002, 74(1): 85. [4] Kan Ruifeng, Liu Wenqing, Zhang Yujun, et al. Chinese Physics, 2006, 15(6): 1379. [5] ZHANG Zhi-rong, DONG Feng-zhong, TU Guo-jie, et al(张志荣, 董凤忠, 涂郭结, 等). Journal of Optoelectronics·Laser(光电子·激光), 2010, 21(11): 1672. [6] Li J, Parchatka U, Fischer H. Applied Physics B, 2012, 108(4): 951. [7] Tian G, Li J. Optica Applicata, 2013, 43(4): 803. [8] Gabor D. Journal of the Institution of Electrical Engineers-Part Ⅲ: Radio and Communication Engineering, 1946, 93(26): 429. [9] Zhang Y, Zhang H. IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2005, 52(10): 1861. [10] Erelebi E. Applied Acoustics, 2004, 65(8): 739. [11] Lu Y, Joshi S, Morris J M. IEEE Transactions on Biomedical Engineering, 1997, 44(6): 512. [12] Rothman L S, Gordon I E, Barbe A, et al. Journal of Quantitative Spectroscopy and Radiative Transfer, 2009, 110(9): 533. [13] De Rosa M, Ciucci A, Pelliccia D, et al. Optics Communications, 1998, 147(1): 55.
