绕光轴旋转拍摄LCD上平面靶标实现相机标定  

Calibrating camera using planar pattern on LCD with a rotating camera

作　　者：张维忠[1] 赵志刚[1] 油世明[1] 袁翠梅[1] 

机构地区：[1]青岛大学信息工程学院,青岛266071

出　　处：《仪器仪表学报》2011年第1期120-125,共6页Chinese Journal of Scientific Instrument

基　　金：国家自然科学基金(50475041);国家863高科技研究发展计划(2006AA04Z110);青岛市科技发展计划(08-1-3-5-jch)资助项目

摘　　要：针对在相机标定过程中传统的图像拍摄方法需要拍摄很多幅图像的问题,本文采用绕相机光轴旋转拍摄LCD屏幕上的平面靶标的方法,以利用少量图像获取较高的标定精度。通过对显示在LCD屏幕上的一个具有不同大小圆形特征点的标定表绕相机光轴旋转拍摄几幅图像,利用亚像素边缘轮廓检测算法检测图像中的轮廓,采用最小二乘椭圆拟合方法得到亚像素椭圆中心坐标,在Zhang的算法的基础上考虑切向畸变系数进行相机参数的计算,计算过程中对所求参数进行非线性优化。本方法利用LCD屏幕存在可视角度这一特性以及极高的几何精度和纯平面性的优点,与以往的拍摄标定方法相比较,本方法所需要图像幅数少,仅需3幅图像就可实现标定并得到较高的标定精度。实验表明,重投影平均误差在0.04个像素左右。证明了该标定方法的可行性和高的标定精度。Traditional image capture methods need taking many images in camera calibration process.In response to this problem,a new technique is proposed,which shoots a planar pattern on LCD with a rotating camera around its optic axis,and uses a few images to get high calibration accuracy.This camera calibration method is based on Liquid Crystal Display（LCD） and works as follows.Firstly,a calibration table that has some circular feature points of different sizes is designed and displayed on the screen of the LCD.And then several images of the calibration table are shot through rotating the camera around its optical axis.A sub-pixel edge detection algorithm is used to extract the contours of the images.Then least-squares ellipse fitting method is used to get the sub-pixel ellipse center coordinates.Finally the camera parameters are calculated based on Zhang＇s calibration algorithm and considering the tangential distortion parameters;and in the calculation process,the camera parameters are non-linearly optimized.The proposed method utilizes the property of viewing angle of LCD screen,and the advantages of high geometric accuracy and pure flatness of LCD.Compared with traditional image shooting method,the proposed calibration method needs only a small number of images.The calibration method can be carried out only using three images and obtains higher calibration accuracy.Experiments show that the mean re-projection error is about 0.04 pixels,which proves that the calibration method is feasible and has high calibration accuracy.

关 键 词：相机标定 圆形特征点 LCD 可视角度 旋转拍摄方法 

分 类 号：TP391.41[自动化与计算机技术—计算机应用技术]