CCD摄像机标定中角点亚像素定位方法

CCD摄像机的标定是实现光学三维轮廓测量技术的必要步骤,其标定精度在很大程度上取决于标定特征点的定位精度.在分析现有棋盘格角点像素级和亚像素级定位方法不足的基础上,提出了一种基于改进SV方法的棋盘格角点亚像素定位方法.首先,采用SV算子对角点进行像素级检测;其次,选取标定图像中以初定位角点坐标为中心的5×5像素区域,对其灰度值进行双线性插值;最后,计算插值图像的灰度质心,再根据插值放大倍数,将质心转换到亚像素坐标,实现了角点亚像素定位.实验结果表明,该方法可以获得亚像素级角点坐标,实现CCD摄像机的高精度标定,标定平均误差为0.108 mm.

Sub-pixel corner detection method in CCD camera calibration

CCD camera calibration is a necessary procedure to realize optical 3D profile measurement, its accuracy depends on the positioning accuracy of feature points in a great degree. A high accuracy corner detection method based on improved SV algorithm was proposed, through analyzing the deficiency of the existing methods to detecting black and white checkerboard corner points. Firstly, the corner points were detected in pixel level using the operators of symmetry and variance. Secondly, the simple gray bilinear interpolation was used for the area of a 5×5 window, whose center was the initial location corner in the photographed checker calibration image. Finally, centroid algorithm was adopted in the areas of each corner neighborhood after interpolation to obtain gray centroid coordinates. According to the amplification factor, centroid coordinates were located to sub-pixel corner coordinates corresponding to the calibration image. The experiment prove the validity of the proposed method, which locate sub-pixel corner coordinates , also can realize the high CCD calibration accuracy. The experiment results show that the average error of CCD calibration is 0.108 mm.