Research On Raman Characteristic Spectrum Measurement Based On Spatial Heterodyne

Spatial Heterodyne Raman Spectroscopy（SHRS）is a hyperspectral detection technology emerged in the 21st century.It favors from home and abroad with the advantages of non-destructive,high-throughput,fast,large field of view,high resolution,and no moving parts,etc.This technique exerts the extremely important research value in national defense security,planets,geology,harsh environment,etc.This technique combines the advantages of Raman Spectroscopy（RS）and Spatial Heterodyne Spectroscopy（SHS）to detect weak Raman signals to compensate for the low resolution of RS technology.In this thesis,the RS characteristic band of theoretical simulated clover,with medicinal research value,is applied to conduct the construction of SHRS experimental platform,and launch relevant research combined with SHS and RS.The main content of the paper are as follows:1.The theoretical calculation section.Firstly,the main pigment molecules of clover,chlorophyll a,chlorophyll b,?-carotene and?-carotene,were modeled via Gauss View,and the RS theoretical simulation for molecular configurations were performed via density functional theory.Subsequently,the peak information of the simulation spectrum is analyzed.The results show that the main pigment of clover has strong excitation,obvious spectral characteristics,and can be used as the identification criteria in band1530～1790 cm^-1.The information of characteristic absorption peaks of this band will provide a guidance for device parameters and optical system design of the experimental platform.2.The experimental research section.Firstly,the measurement platform of Raman experimental was designed by using the SHRS principle.A laser with a center wavelength of 680.28 nm was selected for optical source according to the SHS spectrum range,the characteristic band 1530～1790 cm^-1 of theoretical simulation clover and the matching principle,and the characteristic spectrum of clover is precisely detectable by the SHS system.The real-time data of clover is measured via the designed and built system.Subsequently,the included noise reduction and RS extraction of the clover interferogram are performed according to data processing method of SHRS.The experimental results show that the clover exactly exist the spectral signal in1530～1790cm^-1,which is basically consistent with the clover characteristic spectrum of theoretical simulation.3.Comparative analysis between actual measured results and theoretical simulation results.The measured and simulated RS of the clover are mutually verified.The results show that the absorption peaks of simulated maps are coincided with the measured maps,that the RS of clover is generated by the interaction of various pigments in the leaves which can be concluded that the system is feasible to detect clover RS directly.However,it is found that there are some defects in the system:the Raman signal intensity is generally weak in the actual measurement.Firstly,it is due to the low output power and light intensity of the selected laser.Secondly,it owes to the shorter and nonadjustable maximum integral time of SHS spectrometer.A series of fine pulse signals are superimposed on the waveform of the measured figure,which is principally caused by the thermal noise of the SHS detector and it’s difficult to avoid.In this thesis,the non-contact,rapid detection and identification methods based on SHRS is explored,and realized the direct detection of weak signals of ground targets,which is of positive significance to the development of new spectral detection technology in domestic.