Spectral Signal Processing Method And Software Of Echelle Spectrometer Based On DMD

The echelle spectrometer is a kind of instrument that uses cross-dispersion technology to obtain high-order spectra and achieve full-band blaze.Because of its wide coverage,high spectral resolution,and no moving parts,it is widely used in medical,industrial,agricultural,and food safety fields.At present,echelle spectrometers mainly use charge-coupled devices which have low quantum efficiency in the ultraviolet band as detectors.The short-wavelength can be converted into longwavelength by improving the detector to be back-illuminated or coated with a fluorescent film to detect.These two ways will improve the sensitivity of the ultraviolet band,but will increase the cost of the instrument as well.In addition,the signal-to-noise ratio can be improved by extending the integration time,but the detection time will increase.The echelle spectrometer based on digital micromirror device（DMD）can quickly select any wavelength within the detection range due to the fact that DMD is treated as a spatial light modulator.By using a high-sensitivity photomultiplier tube（PMT）as a detector,it can perform fast and high-sensitivity detection of spectral signals.The spectral signal processing method and software are important parts of the spectrometer.In order to cooperate with the DMD-based echelle spectrometer to work properly,this paper studies the special spectral signal processing method,develops special software,and finally conducts a test experiment.The main research work of the paper is as follows:（1）The spectral signal processing method of echelle spectrometer based on DMDResearch spectral signal preprocessing methods,including spatial domain filtering and background subtraction methods,combined with DMD’s fast and arbitrary flip characteristics and statistical ideas,to quickly and accurately calculate and subtract the background of the measured spectrum.Aiming at the wavelength shift problem caused by the changes of the surrounding environment of the instrument and the deviation of the refractive index of the prism,in order to ensure the accurate drawing of the one-dimensional spectrum,a wavelength calibration method is proposed.Re-fit the refractive index according to the centroid position of the measured characteristic wavelength signal and correct the spectral restoration model.A wavelength extraction method is proposed,which can improve the spectral information processing speed,avoid false peaks caused by the close distance between adjacent orders,and improve the wavelength extraction accuracy.（2）Develop special software for echelle spectrometer based on DMDAccording to the characteristics of the instrument,the software requirements are analyzed.Besides,the communication protocol between the software and the spectrometer hardware is formulated.On this basis,the special software is developed by the joint programming of MATLAB and C#.The software includes UI interactive interface and control components,etc.,and has the functions of online,the control of DMD and PMT,data acquisition,spectral data processing,spectral display and data storage.（3）Test experimentsUse Arsenic（As）,Bismuth（Bi）,Cadmium（Cd）,Lead（Pb）,Tin（Sn）element electrodeless discharge lamps for wavelength calibration,and use Mercury（Hg）element electrodeless discharge lamps to verify the function of wavelength extraction and software.A DMD-based echelle spectrometer combined with an ICP-AES light source was used to measure a standard sample of copper（Cu）elements for field testing.The method and software proposed in this paper have been successfully applied to the DMD-based echelle spectrometer developed by the research group.The experiments show that the wavelength extraction accuracy is less than 0.012 nm.