1. A method for detecting obstacles in the path of a moving vehicle, comprising the steps of: imaging a view from the moving vehicle as at least two image frames, a first frame of the two image frames being taken at a first time and a second frame of the two image frames being taken at a succeeding time; targeting a point in the first frame; defining a location in the first frame for a long and narrow window encompassing the targeted point in a predetermined relationship and extending in a radial direction relative to a focus of expansion in the first frame; establishing a location in the second frame for the long and narrow window by (i) stepwise moving the window in the radial direction while calculating a sum of absolute values of differences in luminance between the window in the first frame and the window in the second frame, and (ii) determining where the calculated sum attains a minimum value; ascertaining a point in the second frame corresponding to the targeted point based on the location of the window in the second frame by utilizing the predetermined relationship; defining an optical flow vector as a displacement measured from the targeted point to the corresponding point; and utilizing a magnitude and a positioning of the optical flow vector relative to the focus of expansion to determine a degree of danger for the moving vehicle.