改进型LOG算子在偏振片绝对角度中的应用

Application of Improved LOG Operator in Absolute Angle of Polarizer

光学成像系统自身通常都具有一定的偏振效应,严重影响仪器偏振测量精度,而提高仪器中偏振片绝对角度精度能提高偏振定标精度,对校正光学系统自身的偏振特性具有重要的意义。对偏振片直线透光轴Raw图像高精度边缘定位和直线检测是偏振片绝对角度计算的关键步骤。针对传统LOG算子各向同性及虚假边缘与边缘定位精度相矛盾的缺陷,提出改进型一阶导阈值旋转式椭圆对称LOG算子。该算子不仅保留了经典LOG算子的优点,还具有对不同角度的边缘更加有效地进行检测,在保持边缘定位精度下,减少虚假边缘的特点。在处理得到的边缘二值图像上,进行直线检测求出偏振片绝对角度,通过对比分析最小二乘法线性拟合和霍夫变换的直线检测效果,得出霍夫变换能精确计算出偏振片绝对角度。实验证明改进型LOG算子与霍夫变换相结合提高了偏振片绝对角度测量精度,对偏振定标精度具有很大的提高。

Optical imaging system itself generally exhibits inevitable polarization effects that seriously affect the instrument＆#39;s polarization measurement accuracy. To improve accuracy of the instrument＆#39;s absolute angle of polarizer can improve accuracy of polarization calibra-tion and it has a significance to correct optical polarization characteristics of the system. Precision edge location and line detection of raw image of polarizer＆#39;s linear transmission axis are the key steps in computing the absolute angle of polarizer. For traditional LOG operator, it has defects of isotropic and false edge which is in contradiction with the accuracy of edge positioning. In order to solve these defects, propose an improved LOG operator called as the threshold of first derivative rotary elliptical symmetry LOG operator. The operator not only retains the advantages of classical LOG operator,but also has the advantage to detect edges of different angles more efficiently and reduce the quantity of false edges with maintaining the accuracy of edge＆#39;s positioning. Line detection operation is taken on the binary im-age after edge detection to computing absolute angle of polarizer. By analyzing and comparing results of line detection of least-squares linear fitting and Hough transform,it is known that Hough transform can accurately calculate the absolute angle of polarizer. Experiments show that improved LOG operator combined with Hough transform can enhance the accuracy of absolute angle of polarizer and the cali-bration accuracy of polarization.