基于Stokes矢量差分法的背景光偏振特性研究

Research on polarization characteristics of background light by modified polarization difference imaging method

水体介质对光线产生的随机散射事件是水下图像发生退化的主要原因,水下偏振成像技术利用背景散射光和目标信息光的偏振信息差异可有效提升成像信噪比.然而随着水体中散射事件增多,光的偏振特性难以保持,这使得基于偏振特性去除散射的效果也随之降低.目前水体中背景散射光的偏振规律尚不明晰,同时缺少对散射光偏振特性定量描述的数据,因此研究水下散射光的偏振传输特性对水下偏振成像的去散射工作具有重要意义.为了明确水下背景散射光的偏振特性,尤其是偏振角信息,本文提出一种基于Stokes矢量差分法的背景光偏振方向研究方法.本方法基于Stokes矢量差分法分析了最优权重系数和Stokes矢量差分结果的图像增强测度(EME)值的耦合关系,基于最优权重系数计算背景光偏振角度;结合实验确定不同浊度水体中最优权重系数与Stokes矢量差分法结果的EME分布趋势,探究散射抑制极限,分析背景散射光偏振方向随水体浊度变化的趋势.研究结果表明,所提方法可得到不同水体环境中背景散射光的确切偏振角度,揭示了背景散射光的偏振方向随水体浊度的上升呈现与入射光偏振方向正交的趋势.本文研究为确定水下成像背景散射光的偏振方向提供了方法依据.

The random scattering event of light by water medium is the primary reason for the degradation in underwater imaging.Underwater polarization imaging technology can enhance the signal-to-noise ratio of imaging effectively by utilizing the polarization information difference between background scattered light and target light.However,as scattering events increase in the water body,it is difficult to maintain the polarization characteristics of light,which reduces the effect of removing scattering based on polarization characteristics.In addition,the polarization rule of background scattered light in water is unclear,and there is a lack of quantitative description of the polarization characteristics of scattered light.Therefore,the study of polarization transmission characteristics of underwater scattered light is of great significance in reducing the scattering light of underwater polarization imaging.In order to clarify the polarization characteristics of underwater background scattered light,especially the polarization angle information,this paper proposes a method for ascertaining polarization angle of background light based on modified polarization difference imaging method.In this method,the coupling relationship between optimal weight coefficient and enhancement measure evaluation(EME)value of the Stokes vector difference result is analyzed,and the background light polarization angle is calculated based on the optimal weight coefficient.Combined with the experimental results,the EME distribution trend of the optimal weight coefficient and the modified polarization difference imaging method results in different turbidity water bodies are determined,the scattering suppression limit is explored,and the trend of background scattered light polarization direction with turbidity of water is analyzed.The results show that the proposed method can obtain the exact polarization angle of background scattered light in different water environments,revealing a trend that the polarization direction of background scattered light becomes orthogonal to the incident light direction as the turbidity of the water increases.This research provides a methodological basis for determining the polarization direction of the background scattered light in underwater imaging.