Bi-tangent line based approach for multi-camera calibration using spheres

This paper presents a novel approach for multi-camera calibration using spheres. We determine the projection of sphere centers first through bi-tangent lines of projection conics, which provides another solution for camera parameters on the basis of the relationship between the images of spheres and the image of the absolute conic in dual space. All parameters are refined by an optimization with the purpose of minimizing the reprojection error, which is divided into two independent parts associated with the corresponding shape parameters of the conics. Experimental results from the synthetic and real data show the feasibility and the accuracy achieved by our approach.