Air-Grid Polarization Splitter for Infrared Imaging Systems

摘要

Polarimetric sensing is adequate for detection of man-made targets, which generally have artificial smooth surfaces. In this paper, we propose an infrared polarization imaging system for detection of man-made targets in natural backgrounds. In order to obtain the polarization properties, images in different polarization states are required. Sequential capturing of polarization images is not suitable for practical systems because the movements of targets and backgrounds cause errors in polarization estimation. The proposed system is capable of capturing simultaneous polarization images. A Brewster angle polarization splitter (BAPS) is used for the polarization imaging system to separate the polarization components of the incident light. We introduce a new type of BAPS structure, called air-grid structure. The air-grid structure is composed of a series of parallel cavity lines on a single plane and shows structural birefringence. As a result, the refractive indices of the air-grid structure satisfy the Brewster angle condition and the total reflection for orthogonal polarization components at the same incident angle. This new structure enhances the field of vie of the BAPS and is ideal for imaging systems.