Computation for polarizer's optimal rotation angle on airborne optical platform

Abstract

The rotation angle of a mounted polarizer in front of a camera has a direct effect on imaging quality and therefore this paper presents a rapid computation method for a polarizer's optimal rotation angle on an airborne optical platform. The computation contains four steps. First, we construct a world coordinate system and a camera coordinate system that both adopt the center of a code disc as their common origin. Second, we take the origin of the world coordinate system as a start point, intercept a unit segment along the sunlight direction and compute the endpoint coordinates of the unit segment in the world coordinate system. Third, by mapping the relation from the world coordinate system to the camera coordinate system, we compute the above endpoint coordinates in the camera coordinate system. Fourth, we project the above segment towards a disc code plane, compute the angle between the projected line and the reference of the code disc, and take the resultant angle distance as a polarizer's optimal rotation angle of airlight rejection utilizing polarization filtering. Experiment results indicate that our computation method of a polarizer's optimal rotation angle can be applied to airlight rejection on an airborne optical platform.