Heading direction of a mobile robot from the optical flow

If a camera, mounted on a mobile robot, moves on a straight line, the optic flow field is a diverging vector field, of which the singularity is called "focus of expansion" (FOE). An object that is seen in this FOE is located on the future path of the camera. However, a mobile robot usually moves on a curved path such that the future path is no longer a point in the image d omain, but a line. All objects which are on the future path (and thus will cause collisions) are projected on this line. Not necessarily the reverse i s true: not all points on the line result in collisions. In this paper we d erive how the optic flow can be used to compute which objects in the image are projections of future collisions. Experiments under controlled conditio ns are carried out to test the theory. (C) 2000 Elsevier Science B.V. All r ights reserved.