结合棋盘格与旋转摄影的多镜头全景摄像机组合标定

Calibration of multi-head panoramic camera using 2D checkerboard under rotation photography

针对多镜头全景摄像机MPC组合标定依赖于高精度3D控制信息的应用限制,本文提出一种结合旋转摄影的MPC棋盘格标定方法,将MPC置于二维转台对棋盘格进行旋转摄影并将标定过程分为两个阶段:(1)侧视摄像机旋转序列影像标定。结合棋盘格与转台坐标系设置建立旋转摄影严格方程并以之为基础给出侧视摄像机外参初值,进而以棋盘格影像角点及相邻侧视摄像机间的连接点为观测值,对侧视摄像机外参及棋盘格外部参数整体进行平差优化求解。(2)中心摄像机多视几何标定。将转台旋转坐标系原点平移至全部侧视摄像机摄影中心几何重心建立MPC空间坐标系,以此为基础利用中心摄像机与侧视摄像机间的多视几何关系及通过旋转摄影获得的大量连接点为观测值,对中心摄像机外参实施光束法平差优化求解。试验结果表明,本文方法仅使用普通二维数控转台和单个棋盘格即可实现MPC摄像机外参的高精度标定,成本低、操作简单且对实时环境要求低,成功摆脱对3D标定场的依赖,具有良好的应用价值。

Multi-head panoramic camera(MPC) with ultra-wide field of view and high resolution is widely used, but its calibration depends on high-precision 3 D control information. In this paper, a MPC calibration method is proposed using one common 2 D checkerboard and rotatable platform. Proposed method is distinctly divided into two stages: firstly, side camera calibration using rotation sequence images. With elaborate consideration of setup of coordinate reference frame of checkerboard and rotatable platform, one strict rotating photography equation is first established for the side-camera of MPC. Based on it, initial external parameter values of the image sequence outputed from any side camera of MPC in rotatable platform are given, and further optimized by taking the corner of the chessboard image and a small number of tie points between the adjacent views of side camera as the observation values. Secondly, center camera calibration based on multi-view geometry. The MPC space coordinate system is first established by moving the origin of the rotatable platform coordinate system to the geometric centroid of center of all side cameras. Based on it, the solid multi-view geometry relationship between the center camera and the side camera are used as the constrain as well as a large number of tie points obtained by rotating photography are used as the observation values to optimize the parameters of the center camera through bundle adjustment. The experimental results show that the proposed method can achieve high-precision calibration of MPC, only using one 2 D checkerboard and a rotatable platform. It has a good application value because of its high-precision, high-degree of automation and low requirements for environment(independence on 3 D control field).