Abstract: An easy method for computing a camera internal parameters based on circular points is proposed. The proposed method only requires the camera to observe a planar calibration pattern which includes a circle and a pencil of its diameters, from at least three different orientations, and either the camera or the planar pattern can be moved freely. The motion need not be known, vanishing points and the vanishing line can be determined using the invariant of tangency, circular points can be computed through the intersection of the vanishing line with the ellipse, and then all the five intrinsic parameters can be determined linearly. The whole process needs to know neither any metric measurement on the model plane, nor the correspondences between points on images. Extensive simulations and experimental results with real images show that the proposed technique is both accurate and robust.

Key words: camera calibration, vanishing point, circular points, absolute conic