像素刻划偏振相机的高精度像素级偏振非均匀性矫正

High Precision Pixel Level Non-Uniformity Calibration of Pixelated Polarization Camera

金属纳米线栅是像素刻划偏振相机的核心器件,线栅上刻划了与光电探测器像元一一对应的微偏振片阵列,该阵列具有较大的非均匀性,对成像质量有较大影响。基于此,根据纳米线栅的结构与偏振传输理论,建立纳米线栅像素级矢量传输矩阵的测量数学模型,并结合矩阵最小二乘法,推导出多次测量以拟合最优传输矩阵的方法,为偏振相机像素级非均匀性矫正提供了核心的矫正参数。然后,兼顾纳米线栅刻划方式,提出了高空间分辨率的矫正算法。通过矫正后,偏振相机非均匀性由原来的2.00%降低至0.26%。外景成像实验中,目标偏振度图像的信息熵由5.34提升至15.15。结果表明,所提算法可以有效矫正纳米线栅的非均匀性,提升了偏振图像质量。

The metalnano wire grating is the core component of pixelated polarizing camera, and the micro-polarizer array engraved on the wire grating is one to one correspondence with the photodetector. This micro-polarizer array has high non-uniformity and large influence on image quality. Aiming at this problem, we improve the mathematic model of pixel-level vector transfer matrix measurement algorithm based on the structure of the nano wire grating and the polarization transfer theory. Combined with the matrix least squares algorithm, a number of measurements are established to fit the optimal transfer matrix algorithm, and then the core calibration parameters are provided for pixel-level non-uniform calibration of the polarization camera. Considering the structure of the nano wire grating, a calibration algorithm with high spatial resolution is proposed. The non-uniformity of polarization camera decreases from 2.00% to 0.26% after calibration. On the outfield experiment, the information entropy of the target polarization image rises from 5.34 to 15.15. The results show that the proposed algorithm can effectively correct the non-uniformity of the nano wire grating and improve the qualitv of polarization image.