| Laser induced fluorescence(LIF) technology is an active optical detecting technology, which can acquire content information of oil, CDOM, and chlorophyll-a by analysing fluorescence induced by laser. It is one of the most effective analytical techniques for monitoring ocean environmental parameters and is developed rapidly. At present, the developed LIF detecting equipments are highly sensitive including fluorescence Li DAR based on airborne, shipborne, shore-based platform and direct in situ instruments. Fluorescent Li DAR can monitor marine aquatic environment remotely and immediately, but the equipment is often expensively, large complex, and professional operated. Shipborne and shore-based in situ equipment is relatively low cost, but it is difficult for rapid measurement of a large area. These limitations make aquatic environment monitoring hard to some extent. To our knowledge, there is no portable LIF instrument which can monitoring water composition remotely. Therefore, a portable and a UAV-based LIF detecting system is investigated.Based on the principle of fluorescent Li DAR, the influence of seawater compositions on inherent optical properties is investgated. The dependence between water composition and bidirectional reflectance distribution function is studied. The bidirectional reflectance distribution function with fluorescence is proposed and the fluorescent Li DAR equation is deduced. A portable LIF monitoring system is designed,which can aquire fluorescence spectra data with high frame rates by adoping a real-time background subtraction algorithm. A UAV-based LIF monitoring system is developed which can be remote operated wirelessly. The main contents are as follows:(1) The principle of fluorescent Li DAR is theoritically studied, and important parameters are introduced.On the basis of Mie scattering theory, the inherent optical properties of seawater with split oil is calculated. According to experimental empirical model, the inherent optical properties of seawater with different chlorophyll concentrations is calculated.(2) The bidirectional reflectance distribution function is introduced, and bidirectional reradiation reflectance distribution function with fluoresence is proposed. According to the inherent optical properties of seawater, the influence of water composition has been simulated using Monte Carlo method. Fluorescence Li DAR equation is deduced, and the receiving fluorescent power under different incident zenith angle is calculated, which will provide theoretical basis for fluorescence Li DAR detection.(3) A portable LIF Li DAR detecting system is developed. The transmittingreceiving system, signal control and processing system is designed. A collimated transmitting optical system and a direct view dispersing system are presented.The software application is developed for LIF Li DAR system, and data processing algorithm is applied for synchronization control system and data acquisition.(4) In order to improve the fluorescent Li DAR system performance, a LIF Li DAR system based on gated ICCD is designed. Three lasers are collimated as excitation to aquire high-energy output for airborne remote sensing. Bidirectional wireless transmission module is designed. LIF monitoring system is improved based on real-time background subtraction algorithm, which can obtain rapid and real-time fluorescence spectrum wih a high SNR. The total weight of designed LIF Li DAR is 5 kg, which can be carried by UAV platform.(5) Fluoresenct spectra of different water and oil samples have been investigated in laboratory and field for category identifying and quantitative analysis. Nearshore experiments has been conducted in Jingzi, Xiaoshidao at Weihai in Shandong province in China. The stability of UAV-based LIF monitoring system is tested using sample pool, which showed good performance. The flight experiment is conducted in Beihai at Weihai in Shandong province, which verified the ability of UAV-based LIF system for monitoring water composition remotely. |
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