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Study on Application of Wavelet Denoising in Terahertz Time-Domain Specstroscopy

Author: CaiNa
Tutor: LangLiYing
School: Hebei University of Engineering
Course: Applied Computer Technology
Keywords: THz time-domain spectroscopy system Denoising Spatial Correlation Threshold Wavelet Transform
CLC: O441.4
Type: Master's thesis
Year: 2010
Downloads: 53
Quote: 0
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Abstract


THz wave frequency in the electromagnetic radiation of from 0.1 to 30 THz (1THz = 1012Hz = 300μm), is the photon energy to only a few milliamps electron volts , it is the unique advantage of the ratio of the X - ray imaging techniques can be used as a lossless cast like . Because the vibrational and rotational levels of many biological macromolecules , and molecular interaction between the energy levels are in the meV range , in this case , the the THz wave spectrum technology as a new research tool , than the Fourier transform infrared spectroscopy techniques more applicable . Ultrashort coherent THz electromagnetic radiation pulses generated by a femtosecond laser pulse excitation combined with optical detection techniques to form a unique electromagnetic radiation detection technology called ultrafast THz wave time domain spectroscopy ( THz -TDS ) , THz domain spectroscopy THz spectroscopy . Spectral measurements , noise interference measurement effect is obvious , if the noise intensity is too large , can easily lead to the absorption peak can not be identified terahertz time-domain spectroscopy . Therefore, there is a need to eliminate or reduce the interference noise in the system , in order to maximize the extraction of useful signal . THz time-domain spectroscopy detection system signal - to - noise ratio is high , the two classic methods : spatial correlation denoising threshold denoising wavelet denoising method . About their traditional denoising principle and mathematical foundation , and on this basis , these two approaches to improve its simulation experiments show that the new algorithm to make up for the deficiencies of the traditional denoising method in a certain degree , on the go The effect of noise improvement . Actual THz time-domain spectroscopy system measurements of water vapor absorption lines in the process , the paper first uses traditional wavelet denoising spatial correlation denoising threshold denoising method and then using the improved two methods for noise removal , simulation results show that the denoised not only the original water vapor absorption lines more obvious , but also be able to get more spectral information .

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CLC: > Mathematical sciences and chemical > Physics > Electromagnetics,electrodynamics > Electricity and Magnetism > Electromagnetic waves and electromagnetic fields
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