Research On Short-wave-infrared High Dynamic Range Automatic Imaging Technology For Maritime Scenes

In recent years,with the proposal of "The Belt and Road" and the construction of the Maritime Silk Road,the maritime trade activities between China and other countries in the world have become more frequent.The number of vessels operating in the sea areas around China has increased significantly which posing a great challenge to the navigational safety of China’s territorial waters and maritime governance.In order to maintain the sovereignty of our territorial waters and guarantee the safety of navigation in the surrounding waters,it is imperative to identify and monitor the ships at sea.Due to the short-wave-infrared imaging technology has the advantages of strong fog penetration,long effective detection distance,strong camouflage identification ability,shortwave-infrared imaging system has become the most suitable system for real-time tracking and monitoring of maritime targets.In practical application,influenced by factors such as shortwave-infrared detector material and complex environment at sea,the contrast of images obtained by maritime short-wave-infrared imaging system is low and the target area is not detailed enough,which brings serious impact to the identification and monitoring of maritime targets.To solve this problem,this thesis introduces high dynamic range imaging technique based on the architecture of the maritime short-wave-infrared imaging system.This technology can simultaneously record the detailed information of overexposed and underexposed areas in the maritime scene,restore the realistic view of the scene,and effectively retain the texture details of the maritime targets.In order to further improve the target tracking and monitoring capability of the maritime shortwave infrared imaging system,the following researches are mainly carried out in this thesis for the technical problems related to the short-wave-infrared high dynamic range imaging of the marine scene:1.A systematic analysis of the background characteristics,noise characteristics and target characteristics of maritime short-wave-infrared images at different times and in different scenes,which provides a theoretical basis for the design of exposure control and multi-exposure fusion algorithms;2.For the problem of automatic exposure instability in the process of acquiring multiexposure image sequences in the maritime short-wave-infrared imaging system,this thesis proposes an improved adaptive exposure control algorithm on the basis of the existing architecture.By introducing PID control and double reference value interval,the effect of strong light irradiation is overcome and fast stable automatic exposure adjustment without oscillation is achieved.3.In order to better acquire short-wave-infrared images with different exposure levels in the scene,so that it can effectively cover all luminance range of target regions in the scene and retain the details of the target regions,this thesis proposes an exposure sampling algorithm based on threshold segmentation in combination with the adaptive exposure control algorithm.The calculation of long and short exposure times is achieved by threshold segmentation of the baseline exposure image,and the algorithm has better adaptability to the complex lighting environments at sea.4.In order to enhance the contrast of short-wave-infrared images of maritime scenes and retain the details of underexposed and overexposed regions,this thesis proposes a multiscale multi-exposure image fusion algorithm for detail enhancement of target regions which based on the existing multi-scale exposure fusion algorithms.The algorithm achieves detail supplementation of the overexposed and underexposed regions of the image while retaining the image contrast and exposure,obtaining better visual effects and effectively enhancing the detail of the target region of the maritime scene.