Calibrating a video camera pair with a rigid bar

In this paper a new procedure to determine all the geometrical parameters of a stereo-system is presented. It is based on surveying a rigid bar carrying two markers on its extremities moved inside the working volume and it does not require grids or complex calibration structures. The external parameters are estimated through the epipolar geometry up to a scale factor which is determined from the true length of the bar. The focal lengths are determined using the properties of the absolute conic in the projective space. The principal points are computed through a non-linear minimisation carried out through an evolutionary optimisation. The accuracy of the method is assessed on real data and it compares favourably with that obtained through classical approaches based on control points of known 3D coordinates.