Camera self-calibration: a new approach for solving the modulus constraint

In this paper, the modulus constraint is used to retrieve the scale factors that are responsible for the nonlinearity of Kruppa´s equations. In the case of constant intrinsic parameters, each pair of images identifies a pair of 3D points at infinity whose coordinates are expressed in terms of the scale factors we are looking for. By enforcing the coplanarity constraint on these points, a set of quintic bivariate equations is obtained for each triplet of images. Once the scale factors are calculated, the problems of retrieving the plane at infinity and solving Kruppa´s equations become straightforward and linear.