Projective calibration of a laser-stripe range finder

We discuss the calibration of a laser triangulation range system mounted on a robot vehicle. Range sensing in general is briefly reviewed, followed by a description of the Oxford/NEL range finder, a sensor mounted on the Oxford AGV for use in object recognition and acquisition tasks. Calibration of the range sensor is achieved by modelling it as a projectivity between two planes: the plane of the light stripe and the plane of the camera's detector array. The vehicle is driven to a known location where there exists an arrangement of orthogonal planes whose equations expressed in world coordinates have been premeasured accurately. Known vehicle position relative to world coordinates, known sensor position relative to vehicle coordinates, and a set of world plane to image point correspondences lead to an overdetermined set of linear equations which can be solved to give the required eight unknown parameters of the projectivity.