Research On Restoration Method Of Spatial Heterodyne Raman Spectroscopy

Spatial heterodyne Raman spectroscopy(SHRS)technology is a hyperspectral detection technology that has been heated in recent years.It has many characteristics:Spatial Heterodyne Raman Spectrosopy can present the results of tests in a short time while the operator only needs to use simple method to manipulate the machine.This technology is also going on without the joint of sample,so the operator has no need to get in contact with samples.The advantages of super-spectral resolution,high-throughput,no moving parts,etc.It can detect in the center range of the characteristic wavelength of the measured substance,and realize the direct measurement of weak Raman optical signals.This technology has extremely important scientific research value in national defense security,planetary exploration,geological survey,etc.Based on the principle of SHRS technology and clover with medicinal research value,this paper designs a spatial heterodyne Raman spectroscopy detection system,and uses the same system to calibrate and detect potassium.This paper launches Discussion on the error characteristics according to the results of the experimental data,and uses four different spectral restoration methods to process the experimental data.The specific content is made up with three parts as follows:Firstly,the spectral range of the spatial heterodyne Raman spectrometer and the theoretical characteristic band of the measured clover are determined according to the principle of excitation matching,while a laser with a center wavelength of 680.28 nm is taken as the excitation light source.Then,the SHRS detection system experimental platform is designed and built according to the principle of SHRS technology.The experimental system consists of two parts: Raman signal detection unit and spectral data extraction unit.At the same time,the test tube and integrating sphere are used to test the experimental system,and it is confirmed that the system could work normally.After adjusting the appropriate software parameters,the experimental system is used to detect clover and obtain its interferogram.And through the same system to calibrate the burning potassium salt to obtain its interferogram.Secondly,the error characteristics of the interferogram obtained by the experimental system will be discussed,then two common spectral restoration methods are used to process the interferogram line average summation and the interferogram line-by-line Fourier transform.However,the restored spectral effect is not ideal.Therefore,combining the error characteristics of the interferogram,two methods of using the strongest signal in the center of the two-dimensional spectrogram and resampling of the two-dimensional spectrogram are proposed to process the experimental data.The two methods proposed in this paper are to apply the two-dimensional Fourier transform to the spectral restoration of the SHRS interferogram.Among them,the method of the strongest signal in the center is to directly select the spectrum corresponding to the strongest signal in the two-dimensional spectrogram,and the method of resampling in the two-dimensional spectrogram is to establish a rectangular coordinate system,fit a straight line equation and resampling in three steps,and realize the acquisition of spectrum.Finally,the direct comparison method and the main peak signal half-width method are used to be compared with the Raman spectra recovered by the above-mentioned methods.The results show that the two-dimensional spectrogram resampling method proposed in this paper are more conducive to recovering the Raman signal,mainly reflected in:Compared with the one-dimensional line average spectroscopy method,the spectrum obtained by this method has more obvious signal intensity in the center area of the detection band,and at the same time eliminates the influence of the thermal noise of the detector;compared with the direct extraction method of the center line of the two-dimensional spectrum.The method is the improved version,and the results of them are relatively close.However,due to the influence of the y component of the interference fringe,the final spectrum obtained by resampling along the strongest direction of the two-dimensional spectrum signal has a narrower half-width of the main peak and a smaller side frequency noise intensity.As the y component increases,the restoration effect and advantages will become more obvious.Therefore,the spectral restoration method proposed in this paper is a useful supplement and attempts to the data processing of spatial heterodyne Raman spectroscopy.