Study On The Key Technology Of Multi-Grating Spatial Heterodyne Spectrometer And Its Application System

Spatial heterodyne spectroscopy(SHS)technology is a new type of static interference spectroscopy analysis technology.It integrates grating technology and Fourier transform spectroscopy technology.The use of diffraction grating ensures that the whole interferogram is created and recorded without moving any components.Based on the high spectral resolution characteristics of grating,the instrument can realize hyperfine resolution of spectrum.In addition,SHS has many advantages,such as high light flux,high signal-to-noise ratio and compact structure.In the practical application,because of the limited number of detector pixels,the SHS will sacrifice the detection spectral range while maintaining the high spectral resolution.However,if the requirement of wide spectral range detection is satisfied,the hyperfine resolution of the spectrum can not be realized,which greatly limits the application and development of this technology.In view of this,a multi-grating spatial heterodyne spectroscopy(MGSHS)technique based on multi-grating modules is proposed in this paper.The technology uses multi-grating modules rather than single diffraction grating that are used to terminate each arm in traditional SHS structure.By increasing the number of sub-gratings with different groove densities in multi-grating module,the detection of wide spectral range and high spectral resolution can be realized simultaneously.MGSHS is equivalent to using multiple,conventional interferometers,stacked on top of each other.While the multiple mosaic sub-gratings result in a compact form of these stacked interferometers.MGSHS not only maintains many advantages of the traditional SHS technology,but also overcomes the limitation of the mutual restriction between the detection spectral range and spectral resolution of the traditional SHS technology.It is of great significance to promote the application and development of the spatial heterodyne spectroscopy technology.In this paper,MGSHS technology is systematically studied.The specific contents are as follows:1.Introduces the research background and significance of SHS,and summarizes the current domestic and foreign research progress of SHS.At the same time,the application research results of SHS in Raman and LIBS spectral detection are summarized.2.Aiming at the shortcomings of traditional SHS,a multi-grating spatial heterodyne spectroscopy technology with high resolution and wide spectral range is proposed.Based on the theory of Fourier transform spectroscopy and traditional SHS,the theory and mathematical model of multi-grating spatial heterodyne spectroscopy are established.The technology is compared with all-reflective reflection tunable and echelle spatial heterodyne spectroscopy,and the technical advantages are highlighted.3.To verify the correctness of the principle of MGSHS,a MGSHS system with the simplest structure(that is,the multi-grating module consists of two sub-gratings with different groove densities)is discussed and studied,along with the proposed design,modeling and simulation,component selection and system construction,acquisition of target interferogram,interferogram data processing and two-dimensional spectral restoration.Sodium lamp and mercury lamp are used as test light source,and the accurate restoration of their spectra verifies the correctness and feasibility of multi-grating spatial heterodyne spectroscopy technology.4.Combining MGSHS with Raman spectroscopy technology.The principle of Raman spectroscopy is briefly described.A multi-grating spatial heterodyne Raman spectroscopy(MGSHRS)system is constructed by using 150 lines/mm and 130 lines/mm grooved density sub-gratings.The system is calibrated by mercury lamp,and the actual system performance parameters are determined.Finally,Raman spectra of various samples were measured and analyzed under different experimental conditions.5.Combining MGSHS with laser-induced breakdown spectroscopy technology.The mechanism of plasma generation and radiation is briefly described.The theory of multi-grating spatial heterodyne laser-induced spectroscopy technology is presented and the experimental system is built.The actual performance parameters of the system are determined by the mercury lamp calibration,and then the detection of laser-induced plasma radiation spectrum is realized by setting the system time sequence reasonably.Laser-induced plasma radiation spectroscopy was used to detect cast iron alloy and eggshell.6.To solve the problem of continuous background interference in the restored spectrum of multi-grating spatial heterodyne Raman/LIBS spectroscopy technology,an automatic background subtraction algorithm based on multi-order minimum points is proposed.The algorithm uses the third-order minimum points to segment the spectrum,and filters the effective points of the second-order minimum points in the segment interval.The background fitted by the effective point set matches the spectral background profile.The validity and correctness of the algorithm are verified by designing(simple and complex)simulated spectra,practical(sparse and congest)LIBS spectra and quantitative analysis of elements.Finally,the continuous background in Raman recovery spectra of methyl salicylate and the continuous background in laser-induced plasma radiation spectra of eggshells are fitted and removed respectively,which shows that the algorithm is suitable for background removal of target recovery spectra in multi-grating spatial heterodyne Raman/LIBS spectroscopy.