The Study Of Rayleigh Brillouin Scattering Lidar System On Gas

With the continuous development and progress of laser technology and scattering spectrum analysis technology,idar based on light scattering technology has been widely applied in field of military,aerospace,marine exploration,geological exploration and meteorological detection,and has made significant breakthroughs and progress.This paper mainly introduces the spontaneous Rayleigh Brillouin scattering?SRBS?spectrum analysis technology,which superposited by Rayleigh scattering and Brillouin scattering,The laser radar device designed by this technology can excite the SRBS signal produced in the gas medium and inverse calculated the temperature,pressure and other related parameters of the target gas.Based on the analysis and simulation of gas SRBS spectrum,a set of SRBS signal generating and receiving system pumped by 532nm laser is designed according to the SRBS characteristic of N₂ under various conditions.The system can stimulate the scattering signal of 90 degrees under different temperature and pressure,then the detection system Consisting of Fabry Perot interferometer,photon detector,delay pulse generator and data acquisition card is responsible for collecting.Controlling of computer and delay pulse generator can realize the Fabry Perot interferometer sweep cycle and data acquisition card scanning cycle match.The collected spectra are fitted and numerically operated by Matlab programming.In this paper,in view of the low scattering signal and the poor signal to noise ratio Using confocal dual concave cavity Fabry Perot interferometer with a reflectivity of94%,reduce the loss caused by the interferometer and improve the intensity of the acquisition signal.On the problem of Mie scattering peaks caused by doped aerosol and diffuse reflection of the inner wall of the scattering cell,we can achieve the optimal matching of the experimental spectrum and the model through the processing of the S6model.Finally,we use the convolution and deconvolution method to fit the experimental results respectively,and use the Levenberg-Marquardt algorithm to optimize the numerical solution.The result of analysis and compared of two fitting methods shows that:data calculated by convolution calculation in high pressure can get high accuracy,however,data in low pressure is difficult to fit because of low signal to noise ratio.The main error comes from system noise;the method of deconvolution can reduce the line type deviation and deformation caused by instability system function of Fabry Perot interferometer,the way of signal restoring is also beneficial to the resolution of the scattering spectrum,but due to the ill-conditioned matrix,it is hard to guarantee stable calculation result.The fitting accuracy of the two methods can be improved through algorithm optimization.Experimental results show that the lidar system based on SRBS has broad prospects and practical significance in practical applications.