分时偏振成像系统中光束偏离的补偿方法研究

分时偏振成像系统需要通过旋转检偏器获取场景的偏振信息(I, Q, U), 检偏器的前后表面间不平行(也称为楔角)将导致成像光束发生偏离且随检偏器旋转而旋转, 这将降低偏振成像系统的空间分辨率和偏振测量精度. 本文提出调整检偏器相对于入射主光轴倾斜角的方法来补偿上述光束偏离. 以格兰棱镜作为检偏器, 根据几何光学理论, 推导了分时偏振成像系统光束偏离的一阶近似补偿模型, 获得倾斜角与格兰棱镜楔角之间的函数关系, 并通过仿真模拟验证了该补偿方法的可行性和有效性. 研究结果表明, 将格兰棱镜置于汇聚光路中, 光束偏离的一阶误差可以通过调节格兰棱镜的倾斜角有效补偿; 倾斜角大小与棱镜折射率、楔角及棱镜距电荷耦合元件靶面的距离成正比, 与棱镜厚度成反比. 该结果为研制高精度分时偏振成像系统提供了切实可行的理论依据.

Study on compensation method of beam deviation in division of time imaging polarimetry

In the division of time imaging polarimetry, polarization information of field under measurement (I, Q, U), is obtained by rotating the analyzer. In the process of measurement, the beam deviation caused by the wedge of the analyzer reduces the spatial resolution and polarization accuracy of imaging polarimetry. In this paper we present that the beam deviation above can be reduced or even compensated for by adjusting the tilt angle of analyzer with respect to the incident optical axis. Taking Glan prism as the analyzer, we establish the first-order approximate compensation model of beam deviation based on the theory of geometric optics, acquiring the function relation between the tilt angle and wedge of Glan prism, and verify the feasibility and effectiveness of the compensation method by simulation. The study shows that the first-order approximation error of beam deviation can be compensated for by adjusting the tilt angle of Glan prism if only Glan prism is placed in a convergent beam; the tilt angle is proportional to Glan prism wedge angle, refractive index, and distance to CCD, but inversely proportional to Glan prism thickness. The results provide a theoretical basis for developing the time division imaging polarimetry with high spatial resolution and polarization accuracy.