0.2～1.8THz波段豆油光谱特性的快速检测
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摘要
针对液体样品在太赫兹光谱检测中遇到的比色皿吸收及频谱振荡问题,以豆油检测为例,在传统计算模型基础上,考虑石英比色皿对THz电磁波吸收,建立THz-TDS技术提取液体材料吸收系数和折射率的计算模型,并对得到的光谱数据利用小波变换进行时-频分析,找出频谱、吸收谱振荡的原因,采用主脉冲截取法,有效去除发射器、探测器以及石英比色皿等光学元件Etalon效应引起的频谱干涉,最后,结合实验得到的0.2~1.8THz波段豆油频谱对采用的主脉冲截取法的优缺点进行分析,并深入探讨1.0~1.8THz频段样品吸收谱、频谱残余振荡存在的原因.该测量分析方法对THz光谱技术在食用油品质检测应用方面进行了有益探索.
In order to solve the problems encountered in Terahertz(THz)spectroscopy detection of liquid samples,THz electromagnetic wave signal attenuation caused by the quartz cuvette and oscillation spectrum produced by Etalon effect,a study was made taking soybean oil detection as an example.On the basis of traditional algorithm for extracting solid material parameters from measured THz waveforms,the influence of quartz was considered,and a new model for calculating the optical parameters of the liquid material was established.By wavelet transform the spectral data obtained was transformed into time-frequency plane and the reason of the spectrum oscillation was analyzed.Then,for reducing these oscillations arising from the Etalon effect in optical elements,a simple algorithm,the main pulse interception,was introduced into signal processing;some improvement on the traditional computing model was made.The results showed that this algorithm can successfully remove Etalon oscillations from the frequency-domain data.Finally,combined experimental spectrum data in 0.2-1.8THz,the strengths and weaknesses of this algorithm were discussed in depth and the reasons for the occurrence of residual oscillation in 1.0-1.8THz band were explored.The measurement and analysis method employed herein should be helpful for the improvement of THz spectroscopy applications in edible oil quality testing.
In order to solve the problems encountered in Terahertz(THz)spectroscopy detection of liquid samples,THz electromagnetic wave signal attenuation caused by the quartz cuvette and oscillation spectrum produced by Etalon effect,a study was made taking soybean oil detection as an example.On the basis of traditional algorithm for extracting solid material parameters from measured THz waveforms,the influence of quartz was considered,and a new model for calculating the optical parameters of the liquid material was established.By wavelet transform the spectral data obtained was transformed into time-frequency plane and the reason of the spectrum oscillation was analyzed.Then,for reducing these oscillations arising from the Etalon effect in optical elements,a simple algorithm,the main pulse interception,was introduced into signal processing;some improvement on the traditional computing model was made.The results showed that this algorithm can successfully remove Etalon oscillations from the frequency-domain data.Finally,combined experimental spectrum data in 0.2-1.8THz,the strengths and weaknesses of this algorithm were discussed in depth and the reasons for the occurrence of residual oscillation in 1.0-1.8THz band were explored.The measurement and analysis method employed herein should be helpful for the improvement of THz spectroscopy applications in edible oil quality testing.
引文
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[2]郭澜涛,牧凯军,邓朝,等.太赫兹波谱与成像技术[J].红外与激光工程,2013,42(1):51-56.
[3]谢丽娟,徐文道,应义斌,等.太赫兹波谱无损检测技术研究进展[J].农业机械学报,2013,44(7):246-255.
[4]LEE Y S.Principles of Terahertz Science and Technolog[M].New York:Springer,2008:232-234.
[5]杨晓杰,李向军,刘建军.石英玻璃太赫兹光学参数测量的误差分析[J].红外与激光工程,2015,44(6):1827-1831.
[6]LI J S.Optical Parameters of Vegetable Oil Studied by Terahertz Time-Domain Spectroscopy[J].Applied Spectroscopy,2010,64(2):231-234.
[7]HIRSCH O,ALEXANDER P,Gladden L F.Techniques for Cancellation of Interfering Multiple Reflections in Terahertz Time-Domain Measurements[J].Microelectron J,2008,39(5):841-848.
[8]NAFTALY M,MILES R E.A Method for Removing Etalon Oscillations from Thz Time-Domain Spectra[J].Optics Communications,2007,280(2):291-295.
[9]王凌辉,王迎新,赵自然.太赫兹时域光谱分析中的回波滤除方法[J].红外与毫米波学报,2013,32(3):265-270.
[10]GUILLET J P,RECUR B,FREDERIQUE L,et al.Review of Terahertz Tomography Techniques[J].J Infrared Millim Te,2014,35(4):382-411.
[11]DORNEY T D,BARANIUK R G,MITTLEMAN D M.Material Parameter Estimation with Terahertz Time-Domain Spectroscopy[J].J Opt Soc Am A,2001,18(7):1562-1571.
[12]GRISCHKOWSKY D,KEIDING S,VANEXTER M,et al.Far-Infrared Time-Domain Spectroscopy with Terahertz Beams of Dielectrics and Semiconductors[J].J Opt Soc Am B,1990,7(10):2006-2015.
[13]邓玉强,郎利影,邢岐荣,等.Gabor小波分析太赫兹波时间-频率特性的研究[J].物理学报,2008,57(12):7747-7752.