Mobile range finder

Claim 1

A mobile range finder for use on a first vehicle to detect the distance to a second vehicle at a desired position in a monitoring direction irrespective of the moving state of the first vehicle comprising: optical picture information generator means installed at a predetermined position on said first vehicle to provide an image of at least a part of a scene in said monitoring direction and generate corresponding picture information on an image plane; edge extracting means for extracting a region where the picture information generated by said optical picture information generating means shows a distinct change; component extracting means for extracting a distinct component comprised of lane marking lines on a road in each region extracted by said edge extracting means; vanishing point determining means including selecting means for selecting from the lines extracted by said component extracting means at least one line included in a preset positive slope region and at least one line included in a preset negative slope region and means for calculating spatial information concerning said vanishing point from a theoretical point or intersection of respective line extensions of said lines and the location of an image of said vanishing point on said image plane; inclination angle detecting means for determining an angle of elevation between the optical axis of said optical picture information generating means and a reference line extending towards said vanishing point on the basis of the spatial information concerning said vanishing point and the location of said image of said vanishing point on said image plane; designating means for designating a desired position in said scene in which said second vehicle would first appear; designated spatial information generating means for generating spatial information corresponding to the desired position designated by said designating means; and distance detecting means for detecting the distance from the first vehicle to the position designated by said designating means to determine the distance from said first vehicle to said second vehicle in said desired position on the basis of said spatial information generated by said designated spatial information generating means, information concerning the level of the position at which said optical picture information generating means is installed and said inclination angle information determined by said inclination angle detecting means.