海面油膜的偏振反射特性仿真实验

为了给海面溢油污染识别检测提供理论基础,根据菲涅尔反射公式的偏振反射系数,结合偏振双向反射率因子和粗糙海面的概率密度分布函数,建立了完善的pBRDF模型,仿真在不同太阳入射角度、不同探测器观测角度以及不同海面风速风向等条件下海水和油膜的偏振反射分布函数。结果表明:海水和油膜太阳天顶角为53°和56°时P偏振反射率分别为1.0×10^-5和2.5×10^-5,S偏振反射率随着太阳天顶角的增加而增加;海面风速越大偏振反射率峰值越小;海面风向只改变pBRDF的空间位置;海水和油膜线偏振度空间分布有明显差异。搭建实验平台相机以40°拍摄时,得出海水和油膜的线偏振度分别在0.2~0.4, 0.5~0.7之间,同时表明利用偏振探测获取目标场景的偏振度和偏振角图可提高图像质量。

Simulation experiment of polarization reflection characteristics of the oil slick

To provide a theoretical basis for identification and detection of oil spill pollution on the sea surface,based on the polarization reflection coefficient of Fresnel reflection formula and combined with polarization bidirectional reflectivity factor and probability density distribution function of rough sea surface, a perfect pBRDF model was established. Then the polarization reflection distribution function of sea water and oil film was simulated under different solar incident angles, different detector observation angles and different sea surface wind speed and wind directions. The results show that, firstly, P-polarization reflectance reaches 1.0×10^-5 and 2.5×10^-5 respectively when the solar zenith angle of seawater and oil film is 53° and 56°. S-polarized reflectance increases with the increase of the solar zenith angle. Moreover, the higher sea surface wind speed is, the smaller peak value of polarization reflectance is. Additionally, wind direction only changes spatial position of pBRDF.Finally, the spatial distribution of linear polarization degree between seawater and oil film is obviously different.Experiment platform was set up with the camera working at 40°. The conclusion is obtained that the linear polarization of seawater and oil film is between 0.2-0.4 and 0.5-0.7, respectively. It also shows that using polarization detection to obtain the polarization degree and polarization angle of the target scene can improve the image quality.