Target Tracking by a Single Camera Based on Range-Window Algorithm and Pattern Matching

An algorithm, which determines the range of a preceding vehicle by a single image, had been proposed. It uses a “Range-Window Algorithm”. Here in order to realize higher robustness and stability, the pattern matching is incorporated into the algorithm. A single camera system using this algorithm has an advantage over the high cost of stereo cameras, millimeter wave radar and non-robust mechanical scanning in some laser radars. And it also provides lateral position of the vehicle. The algorithm uses several portions of a captured image, namely windows. Each window is corresponding to a predetermined range and has the fixed physical width and height. In each window, the size and position of objects in the image are estimated through the ratio between the widths of the objects and the window, and a score is given to each object. The object having the highest score is determined as the best object. The range of the window corresponding to the best object becomes an estimated range. The pattern matching helps this algorithm when the camera image is influenced by a shadow. Since this matching adopts a warped template, it can estimate the range. This algorithm was applied to more than 4,500 real road images. It showed the range accuracy of about +/- 1 [m] and 94% detection rate for a motorcycle, sedan, minivan, truck and bus on rural, urban and city roads. And the incorporation of the pattern matching has improved the detection rate up to 97%. The present maximum range is 50 [m]. This algorithm is effective for the short range application like “Low speed follower”.