Focal length self-calibration based on degenerated Kruppa´s equations: method and evaluation

In this paper, a linear self-calibration approach for camera focal length estimation is proposed. No priori information of camera motion is needed for the method. The unknown focal length of camera is conveniently obtained in closed form from degenerated Kruppa´s equations. These degenerated equations (one quadratic and two linear) provide the essential constraints on calibration of camera intrinsic parameters. Real images of indoor and outdoor generic scenes and 3D metric reconstruction are used to analyze the accuracy of the estimated focal length. Experiments results show that the method is both robust and efficient.