Research On Key Technologies Of Active Hyperspectral Detection For Marine Oil Pollution Monitoring

Marine oil pollution is a serious hazard to biodiversity and the ecological environment and is currently monitored mainly by passive detection techniques,including ultraviolet imaging detection and infrared imaging detection technology.However,the passive detection technology is limited to the measurement during daytime with good lighting conditions.Therefore,it is particularly important to study the active detection technology based on hyperspectral lidar,which can achieve all-weather observation of the oil spill area and realtime response to the dynamic information of the oil surface.Conventional lidar technology is limited to single-band applications and cannot accurately acquire spectral information of the maritime oil spills.This dissertation focuses on monitoring technology of marine oil pollution and carries out research on hyperspectral lidar monitoring technology based on the lidar principle.Hyperspectral lidar is an instrument capable of actively acquiring spectral and spatial information,which can mitigate the influence of ambient light on spectral information acquisition.This dissertation describes the development of domestic and international hyperspectral remote sensing technology and the current research status of hyperspectral lidar technology,as well as the relevant research on maritime oil-spills detection technology,further clarifies the technical requirements of hyperspectral lidar applied to maritime oil-spills monitoring,and proposes technical indicators to meet the actual working requirements based on a comprehensive analysis of several factors.According to the specific requirements of the technical indicators for marine oil spill pollution monitoring,the key technologies for the design,manufacture,tuning and calibration of the new full-time multi-spectral lidar are studied in depth.The specific research content is as follows.(1)The optical design and simulation analysis of the front telescope system were carried out by using Code-V design software for the requirements of the new spectral monitoring technology index and the characteristics of the hyperspectral lidar.At the same time,the matching mechanical structure was designed and an optical system was manufactured to meet the requirements of the technical specifications and with excellent performance.The structure of the optical system is greatly simplified by the use of a folded reflection system.To satisfy the tracking and fine structure measurement of the target,a visible light receiving system is added based on the common optical path,so that the hyperspectral lidar can locate and image the target at the same time as the spectral measurement.(2)A comprehensive spectral performance test method for the visible and near-infrared wavelengths was proposed and constructed,and a more comprehensive evaluation of the spectral range,spectral response,dynamic range and other indicators reflecting the spectral performance of the hyperspectral lidar principle prototype was carried out to complete the quantitative study of hyperspectral lidar.(3)A comprehensive evaluation of the spectral irradiance responsiveness and response uniformity of the hyperspectral lidar principle prototype was carried out using an integrator sphere with highly stable output and tunable energy,equipped with the corresponding equipment,and the corresponding correction formulae were given for the specific lidar principle prototype.(4)The formula for calculating the signal-to-noise ratio of this hyperspectral lidar is analysed and derived.Based on the spectral transmission characteristics of the front optical structure of the experimental prototype with known maritime oil-spills remote sensing detection angle and detection distance,and combined with the actual experimental results,the signal-to-noise ratio of this hyperspectral lidar prototype is comprehensively estimated in the actual oil spill monitoring work on the sea surface.(5)The hyperspectral lidar prototype was used to experimentally detect the oil spill in a laboratory simulation.The spectral irradiance measurements and visible camera imaging were carried out at daytime and nighttime for different thicknesses of crude oil spill on the water surface,and the variation of the reflectance spectra at different temperatures and different oil film thicknesses were measured by varying the water surface temperature.The experimental results show that the hyperspectral lidar developed in this dissertation can accurately distinguish between oil-covered and clear water surfaces in the observation of oil spills at sea,especially at night,and that the monitoring method adopted can be applied to the whole sea area of China and can make a more accurate judgement on the pollution level based on the acquired spectral characteristics.In this dissertation,we develop a hyperspectral lidar prototype that can simultaneously acquire target spectral information and two-dimensional images,which covers the wavelength range of 400nm?1100nm and evaluate the overall design and evaluation of the instrument according to the structural characteristics of the whole system,as well as the application in the maritime oil spill.The principle prototype after commissioning meets all the application requirements,providing a new means of monitoring the marine oil spill in China,which is of great significance to the future marine environmental protection and marine resources utilization and development.