荧光激光雷达技术探测水面油污染系统仿真研究

为实现对水面油污染的探测, 根据荧光激光雷达系统的发展趋势, 采用激光诱导荧光技术, 建立了适用于水面油污染探测荧光激光雷达的系统模型. 提出采用单激光器结合增强电荷耦合器件的小型荧光激光雷达探测系统, 通过分析激光器单脉冲能量与探测浓度之间的关系, 结合荧光激光雷达系统参数, 对系统模型的探测能力与信噪比等进行了数值仿真. 结果表明, 系统选用单脉冲能量50 μJ的355 nm Nd:YAG激光器作为激发光源, 白天在7 m的距离处探测信噪比可以达到10, 满足实验室搭建模拟系统的要求. 针对实际探测水面油污染, 提出采用增大激光器功率的方法, 并通过模拟计算验证了采用50 mJ的单脉冲能量激光器在230 m的探测距离处可得到与实验室相同的结果, 对实际系统的搭建具有指导意义.

Simulation of fluorescence lidar for detecting oil slick

In order to measure the oil pollution on water surface, a fluorescence lidar model system based on laser induced fluorescence is put forward for detecting oil slick. The system model and fluorescence detecting principle are described in detail. According to the properties of detected material, wavelength of laser and filter of receiving system are adopted to ensure that the lidar system is operated at the peak wavelength. Following the development trend of miniaturization in the world, using single laser and intensified charge-coupled devices, a small fluorescence detecting system is designed. FTSS 350-50 laser made by CRYLAS company, with compact dimension, low weight and excellent energy efficiency, and PI-MAX4 intensified charge-couple devices made by Princeton Instruments company, with good time resolution characteristic, are selected to produce laser as a launch device and to inspect fluorescence lifetime and capture image as a receiving device, respectively. The laser excitation wavelength, the energy of laser, the center wavelength and bandwidth of filter, the received echo fluorescence signals, the detected concentration and distance are discussed in detail by means of the instance for oil on water surface. Through analyzing the relationship between the energy of laser single pulse and the detection concentration and by combining with the parameters of fluorescence lidar system and fluorescence lidar equation, the detecting ability of system model, signal-to-noise ratio, etc. are simulated particularly. A numerical simulation of the signal-to-noise ratio of the fluorescence particles is conducted particularly so that the detectable capacity of system designed could be described better. The results show that the signal-noise ratio of system which is operated during the night is superior to in daytime in the same single pulse energy case and that the detected range becomes gradually longer as the energy of laser improves with the same signal-noise ratio case. The required single pulse energy to support system is calculated, and further verifies the feasibility of the lidar system. The test results of the sample show that in the daytime, the design of fluorescence lidar model, with a Nd:YAG laser of 50 μJ single pulse energy and 355 nm wavelength serving as an excitation light source, with a collection device placed at a distance of 7 m, can satisfy the requirements for detecting oil pollution on the water surface in laboratory, and its signal-noise ratio can reach 10. In view of the actual surface fluorescence lidar detection requirements, the method of increasing the laser power is proposed. A real system with 50 mJ single pulse energy at a distance of 230 m has nearly the same performance as the laboratory lidar system, which could provide a valuable guidance for designing a real system.