DETERMINING THE EGOMOTION OF AN UNCALIBRATED CAMERA FROM INSTANTANEOUS OPTICAL-FLOW

A procedure is described for self-calibration of a moving camera from instantaneous optical flow. Under certain assumptions this procedure a llows the egomotion and some intrinsic parameters of the camera to be determined solely from the instantaneous positions and velocities of a set of image features. The proposed method relies on the use of a dif ferential epipolar equation that relates optical flow to the egomotion and the internal geometry of the camera. A detailed derivation of thi s equation is presented. This aspect of the work may be seen as a reca sting into an analytical framework of the pivotal research of Vieville and Faugeras [Proceedings of the Fifth International Conference on Co mputer Vision (IEEE Computer Society Press, Los Alamitos, Calif., 1995 ), pp. 750-756]. The information about the camera's egomotion and inte rnal geometry enters the differential epipolar equation via two matric es. It emerges that the optical flow determines the composite ratio of some of the entries of the two matrices. It is shown that a camera wi th unknown focal length undergoing arbitrary motion can be self-calibr ated by means of closed-form expressions in the composite ratio. The c orresponding formulas specify five egomotion parameters as well as the focal length and its derivative. A procedure is presented for reconst ructing the viewed scene, up to a scale factor, from the derived self- calibration data and the optical flow data. Experimental results are g iven to demonstrate the correctness of the approach. (C) 1997 Optical Society of America.