Study Of Target Enhancement Technique Based On Polarimetric Imaging

With the development of industry,the haze weather becomes more frequent due to the environment pollution and climate change,which causes adverse impact on traffic safety,public surveillance and so on.At the same time,with the territorial issue has become increasingly acute,underwater exploration and marine surveillance has gained great attention.Images obtained in haze environments and underwater environments are usually much limited due to the disturbance of turbid media.These images usually show low contrast,and sacrificial details of targets that are submerged into the noise.How to mitigate such negative effects and enhance the contrast of images acquired in turbid media(such as haze and water)attracts more attentions.With the improvement of imaging technique,polarimetric imaging technique is a novel imaging technique based on detecting the polarization information of the reflected light from target and has its unique advantages compared with the intensity imaging in target detection.Due to the fact that the polarization information of the target is closely related to the characteristics of its own,thus,the polarization information of the target is difficult to be hidden or disguised.Compared with the traditional imaging techniques,polarimetric imaging technique has advantage in target detection with low contrast.Thus,polarimetric imaging technique has widely applications and high value of researches.Theoretical and experiment researches on polarimetric imaging in haze environments and underwater environments have been studied in this dissertation.Based on the analysis of the traditional polarimetric descattering algorithm,a new polarimetric descattering algorithm is proposed.The main research contents can be listed as follow:(1)According to the deep analysis on traditional polarimetric dehazing algorithm shows there are several drawbacks,such as inaccuracy on estimating polarized parameters and poor real-time capability.Focusing on these two drawbacks,a polarimetric dehazing algorithm based on dark channel prior is proposed.In this polarimetric dehazing algorithm,four images with different polarization state are captured,and then estimation accuracy of airlight can be improved by utilizing Stokes vector.Meanwhile,combine the dark channel prior,which can identify the sky region automatically and quickly.(2)Focusing on the drawbacks of underwater descattering algorithm,such as inaccuracy on estimating polarized parameters and the application is limited,we propose a method of visibility enhancement of underwater images based on polarimetric imaging utilizing active unpolarized illumination.The advantage of this method is that unpolarized illumination ensures the different polarization state between direct transmission and veiling light in all cases and AoP is used to estimate the veiling light precisely.Compared with the current underwater polarimetric imaging techniques using polarized illumination,our method is beneficial to inherently enhance image quality,and at the same time to own wider application range and higher real-time characteristic.Experimentally,the visibility and the contrast of underwater images are enhanced effectively.In addition,it is demonstrated that our method is applicable for targets of different imaging distances and different materials in water of different impurities and different turbidity.The contrast of underwater images could be promoted at least 100%,meaning that this kind of technique can be potentially used in many underwater environments.