Wang Yujie, Hu Xiaoping, Lian Junxiang, Zhang Lilian, Xian Zhiwen, Ma Tao
College of Mechatronics and Automation, National University of Defense Technology, Changsha 410073, Hunan, China.
Sensors (Basel). 2014 Aug 14;14(8):14916-31. doi: 10.3390/s140814916.
Sky polarization patterns can be used both as indicators of atmospheric turbidity and as a sun compass for navigation. The objective of this study is to improve the precision of sky light polarization measurements by optimal design of the device used. The central part of the system is composed of a Charge Coupled Device (CCD) camera; a fish-eye lens and a linear polarizer. Algorithms for estimating parameters of the polarized light based on three images are derived and the optimal alignments of the polarizer are analyzed. The least-squares estimation is introduced for sky light polarization pattern measurement. The polarization patterns of sky light are obtained using the designed system and they follow almost the same patterns of the single-scattering Rayleigh model. Deviations of polarization angles between observation and the theory are analyzed. The largest deviations occur near the sun and anti-sun directions. Ninety percent of the deviations are less than 5° and 40% percent of them are less than 1°. The deviations decrease evidently as the degree of polarization increases. It also shows that the polarization pattern of the cloudy sky is almost identical as in the blue sky.
天空偏振模式既可以用作大气浑浊度的指标，也可以用作导航的太阳罗盘。本研究的目的是通过对所用设备进行优化设计来提高天空光偏振测量的精度。该系统的核心部分由电荷耦合器件（CCD）相机、鱼眼镜头和线性偏振器组成。推导了基于三幅图像估计偏振光参数的算法，并分析了偏振器的最佳对准方式。引入最小二乘法估计来进行天空光偏振模式测量。使用所设计的系统获得了天空光的偏振模式，它们几乎遵循单散射瑞利模型的相同模式。分析了观测值与理论值之间偏振角的偏差。最大偏差出现在太阳和反太阳方向附近。90%的偏差小于5°，其中40%小于1°。随着偏振度的增加，偏差明显减小。这也表明多云天空的偏振模式与蓝天几乎相同。
