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哈尔滨工业大学2. 哈尔滨工业大学自动化测试与控制系
收稿日期:2009-01-19,
修回日期:2009-04-27,
网络出版日期:2009-08-20,
纸质出版日期:2009-08-20
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张灵飞,陈刚,叶东,车仁生. 基于自由运动的刚性球棒的像机内外参数标定[J]. 光学精密工程, 2009,17(8):1942-1952
Camera intrinsic and extrinsic parameters calibration based on rigid ball bar with free motion[J]. Optics and precision engineering, 2009, 17(8): 1942-1952.
制作一种两端及中间各安装一个红外反光标志球的刚性球棒,不需要其它复杂标定装置,只要将这种特制的刚性球棒在测量空间内多次随意移动并摄取其图像,即可实现双像机标定。标定算法首先假定主点位于像面中心附近的某个位置,通过Hartley改进八点法求出基本矩阵,继而求出半标定矩阵并对其奇异值分解,再线性地求出焦距。接着求出本质矩阵,奇异值分解后得到旋转矩阵和比例因子意义下的平移向量。利用三角法确定刚性球棒两端点的重建坐标和距离,与标准距离对比确定比例因子。通过评价函数将像机标定转换成寻找两像机最佳主点配对的非线性最小化问题。运用改进的模拟退火进化策略算法迭代优化求解出最佳主点配对,继而求解出像机其它内外参数。与传统方法相比,本文方法不需要对球棒的运动做任何限制,并且能够同时求解出像机内、外参数,改进的模拟退火进化策略算法改善了全局收敛性能并加快了收敛速度。
In this paper a novel approach of calibrating the intrinsic and extrinsic parameters of binocular is proposed. It is based on surveying a rigid ball bar carrying three markers on its middle and extremities moved inside the working volume and it does not require other complex calibration equipment. Firstly
the principal point is assumed at a certain location around the image plane center. the fundamental matrix is found out by Hartley’s eight-point-algorithm. the semi-calibrated fundamental matrix is solved and decomposed by singular-value-decomposition method
and then the focal length is obtained linearly. Secondly
the essential matrix is educed and decomposed by singular-value-decomposition method
then the rotation matrix and translation vector with scale factor are obtained. Thirdly
the coordinates and the distance of the ball bar are solved by triangulation method
and then the scale factor is found out through the true distance of the ball bar. Finally
the estimation of intrinsic and extrinsic parameters of binocular is formulated as a nonlinear minimization problem of a cost function. By using the improved simulated annealing evolutionary strategy algorithm the optimal principal points of two cameras are found out iteratively
and then all parameters of cameras are optimized. In comparison with traditional methods
the novel approach can find out the intrinsic and extrinsic parameters all together
and need not constrain the movement of the one-dimensional object--ball bar. The improved simulated annealing evolutionary strategy algorithm mends and accelerates the global convergence performance.
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