Study On Information Representation And Enhancement Technology Of Infrared Polarization

Infrared polarization technology is a new means of infrared detection just developed recently. By using the infrared polarization characteristics of either target reflection and scattering or radiation as the probe information, infrared polarization technology can be effective in combating against camouflage and stealth means such as infrared camouflage net, infrared smoke and infrared stealth. It can improve the accuracy of target discovery and enhance the efficiency of detection systems, and therefore it has significant applications value.Stokes vector is selected in this paper to describe the polarization properties of the target and an imaging system of infrared polarization is constructed according to the experiment. The infrared scattering and polarization of target, self-radiation polarization and their effecting factors are analyzed in detail. The characters of infrared polarization for typical targets are measured and calculated.Infrared polarization of targets can be comprised of two parts, one from the reflection and scattering of radiation around the target and the other from self-radiation of target. According to the Fresnel formulation, the phase difference of spectral components from the two orthogonal directions after reflection will be changed. In view of self-radiation, the absorption will be equal to the emission for the target in thermal equilibrium, according to the law of energy conservation. Because of the difference of reflection between parallel components and vertical components, the absorption of these two components will also be different, which leads to the polarization in the self-radiation.The factors which affect the polarization characteristic are studied in this paper. The effects of temperature on polarization characteristic of metal plates are studied at first. The differences among the copper plate, aluminum plate and several kinds of painted aluminum polarization characteristics are analyzed. The experimental results show that the metal plates have similar polarization properties. The painted surfaces have no effects on polarization except the one with black painting. According to the changes of both observation angle and azimuth, five targets including cement ground, grass, wood, iron, plastic plates, are measured outside the building. Their infrared polarization characteristics and azimuth’s variations are analyzed. The results show that, for the objects with high homogeneousness of surface character, the variation of polarization characteristics with azimuth is not obvious. But with the increasing of observation angle increases, the polarization will also increase and get its maximum when the observation angle is around 70 degree. Then, the polarization will decrease slowly as the observation angle continues with increase. The above conclusion will be of great significance for applying robust infrared polarization characteristics in target detection and recognition in the future.Then, the polarization theory is integrated with infrared polarization characters, and an image enhancing algorithm based on virtual variable polarization is proposed for the infrared planar object. The algorithm can simulate intensity’s images of infrared polarization with any angle of polarization, thereby it can achieve the optimal receiver and maximum suppression of background based on the infrared characters. In experiments, the enhanced image has significant improvement in gray standard deviation, which provides an accurate data source for the following target feature extraction and image fusion.