海面耀光背景下的目标偏振检测

Polarization detection of marine targets covered in glint

海面耀光是海洋目标检测中的强干扰源,必须进行有效抑制。传统的通过单个平行偏振片抑制耀光的方法只能抑制耀光的s偏振分量,且抑制效果取决于太阳、探测器的几何位置,适用性非常有限,难以适应天基海洋观测需求。在分析耀光、海面目标的偏振特性基础上,利用目标与耀光背景的偏振特性差异设计了基于双线偏振片的可见光偏振检测系统,并在实验室内进行了实验验证。实验结果表明:在光源、成像系统天顶角均为65°的非布儒斯特角镜面反射条件下,目标相对耀光背景对比度为0.05,采用单个平行偏振片后对比度为0.45,而采用偏振方向呈45°的双线偏振片后对比度为0.9,偏振方向呈75°的双线偏振片后对比度为0.41。因此合理设计偏振方向的双线偏振片成像系统可有效抑制耀光干扰,提高目标与背景的对比度,有利于提高海面耀光背景下的目标检测效果。

Glint is the strong noise in the marine targets detection and it must be reduced. The traditional method that deploys one parallel line polarizer can only suppress the s-component of the glint. And the effectiveness of suppressing is due to the geometry of the sun and the detector. So the traditional method can only be used in few scenario. A new imaging system mounted two line polarizers was developed on the foundation of the theoretically analyzing the polarization characters of glint and marine targets. The experiment results show that under the condition of the non-Brewster angle specular reflection, while zenith angle of the light source and the imaging system without polarizer are 65°, the contrast of the target image is 0.05. When the imaging system is mounted with only one parallel polarizer the contrast is 0.45, while mounted with two line polarizers which the angle between the two polarization directions is 45° the contrast is 0.9, and which the angle is 75° the contrast is 0.41. So the imaging system with two line polarizers which have reasonable design of polarization direction can effectively suppress glint interference, improve the contrast between the target and the background, which can improve the effect of marine targets detection covered in glint.