Research On Optical Detection Techniques For Ocean Weak Moving Targets

The research on optical detection techniques of ocean weak moving targets has important research significance in the field of ocean remote sensing.The effective optical detection of ocean weak moving targets has important application value in the fields of ocean monitoring and target tracking.Aiming at the problems of optical detection of weak moving targets in the ocean,this dissertation carries out the systematic research from theoretical modeling,index analysis,system design,data preprocessing and target detection,airborne testing,etc,and the research has important practical significance.The main work and research results of the dissertation are as follows:1.This dissertation completes the optical characteristics analysis of the ocean weak moving target.Firstly,the wave spectrum theory and the common wave spectrum model are introduced.The sea surface geometry simulation is carried out based on the typical P-M(Pierson-Moscowitz)wave spectrum model,and the influence of TDI(Time Delay and Integration)imaging mode on sea surface imaging is analyzed.Secondly,the main information of the detection of the weak ocean target,the wake,is analyzed,at the same time,the effects of ship speed,size and other factors on the wake model are explored,and the modeling and simulation of both wake and wake in TDI imaging mode are completed.Finally,the study of the optical scattering characteristics of the sea surface for the sun and atmospheric background is carried out.Based on the analysis of solar radiation characteristics and atmospheric transmission characteristics,and combined with the Cox-Munk model,a sea surface scattering model considering the shadowing is established,which provides theoretical guidance for the index analysis and system design.2.This dissertation completes the index analysis and system design of the spaceborne optical system for the ocean weak moving target detection.According to the characteristics analysis of the optical detection system for the wake scale,target-background contrast and reflectivity resolution involved in the detection of weak ocean targets,selections of several key indicators of the ocean weak target optical detection system---geometric resolution,spectral segments,optical parameters,imaging parameters---are completed by the full-link simulation of the imaging system.At the same time,this dissertation completes the design of the overallscheme,the optomechanical system scheme,and the electronics system scheme combining with the actual engineering requirements.3.This dissertation completes the research work on optical image preprocessing and detection techniques for ocean weak moving targets.The ocean optical image is analyzed and its typical characteristics in illumination,non-uniformity and noise are proposed.These three characteristics are also the three main factors affecting the image quality of ocean optical image.For the non-uniformity correction of ocean optical image,the dissertation follows a three-step correction method based on calibration data,based on measured data and based on image data,and completes the full-link non-uniformity correction of the detector response from the laboratory calibration to the actual scene calibration,then to the image calibration.For the noise characteristics,the dissertation proposes a mixed heavy noise model for sea surface image.At the same time,a denoising model based on total variation and split Bregman for uniform illumination sea surface image is proposed.For the illumination characteristics,the dissertation combines the bit plane decomposition analysis of the sea surface image and proposes a solar-scattering halo model based on Gaussian function fitting for the sea surface image with non-uniform illumination.At the same time,considering the influence of illumination,noise and non-uniformity,a new sea surface image denoising and enhancement model suitable for non-uniform illumination conditions based on Retinex model and total variation theory is proposed.This model also suitable for the denoising and enhancement of uniformly illuminated sea surface images when the parameters are properly selected.Considering the application requirements of optical detection of weak moving targets in the ocean,the dissertation completes the research on the ocean weak moving targets detection.For the ocean weak ship target and the ship wake target,the ocean weak ship target detection method based on the saliency theory and the ship wake target detection method based on directional Gabor transform are proposed respectively.Two methods can effectively realize the detection of ocean weak moving targets.4.This dissertation completes the optical detection test of ocean weak moving targets.The test system is constructed,the airborne flight test is carried out.The data processing and analysis work is completed using a series of data collected by the test.The optical image non-uniformity correction effect,the denoising and enhancement effect and the targets detection effect of the ocean weak moving target are obtained.The results show that for the image non-uniformity,the three-step correction methodused in the dissertation can significantly improve the uniformity of image data.For the image noise and illumination problems,the proposed method can effectively achieve the removal of halo and noise.The overall gray scale range after denoising and enhancement is moderately stable and the background wave information of the image is clear.For the detection of weak moving targets,the proposed method can achieve effective detection of weak ship targets,and has strong anti-noise ability.The performance is superior to the similar comparison methods.The method of detecting the weak ship wake information by using the directional Gabor transform can also effectively realize the discovery of the wake information.