Research Of The Denoising Method For The Echo Signal Based On Mie Scattering Lidar

Lidar is a powerful active remote sensing technology.It is widely applied in atmospheric detection due to the advantages of great detection performance,high resolution and strong antiinterference ability.However,lidar echo signals are easily contaminated by noise,particularly strong background light noise and detector noise,which seriously affects the effective detection range and retrieval accuracy of lidar system.In this paper,a coupled whale optimization algorithm(WOA)and variational mode decomposition(VMD)for noise reduction in lidar signals is proposed and successfully used to the noise process of Mie scattering lidar echo signal.The specific research contents of this paper are as follows:1.The working principle and physical basis of laser atmospheric detection are discussed.Then,we introduce the Mie scattering lidar system built by our research group.This lidar device consists of the laser transmitting system,the optical transceiver system and the data acquisition and processing system and the main parameters are described in detail.2.By analyzing the noise sources and characteristics of lidar echo signal,a novel VMD denoising method(VMD-WOA)with a whale optimization algorithm is proposed.The optimal combination of VMD parameters of decomposition mode number and quadratic penalty are obtained by using the WOA.Then,the Bhattacharyya distance is applied to identify the relevant modes,which are reconstructed to achieve noise filtering.The simulation results show that the proposed method has obvious advantages in terms of output SNR and root mean square error compared with other common denoising technologies such as wavelet transform based on db4,EMD direct thresholding,EMD combined with soft thresholding and roughness penalty,and VMD method based on the decomposition level of EMD.3.In order to further verify the effectiveness of VMD-WOA algorithm,it is used to filter the Mie scattering lidar echo signal.Compared with the common denoising technology,the signal-to-noise ratio of the echo signal after VMD-WOA treatment was increased to 23.92 dB,and the detection range was extended from 6 to 10 km.Moreover,the variation characteristics of the retrieved atmospheric extinction coefficient distribution are effectively identified.In addition,the visibility values obtained by the visibility calculation formula are basically consonant with the results of the CJY-1A visibility meter,which confirms the applicability of the WOA-VMD method.