Development of ranging method for inter-vehicle distance using visible light communication and image processing

Simple and low-cost method for the measurement of inter-vehicle distance has been developed. Proposed method is based on geometric similarity between an object on the rear surface of a vehicle and its image on image sensor. Size of the object should be well-known or be informed using visible light communication. This time, a license plate was used as the object during the day, and a distance between tail lamps was used during the night. After image processing, the size or length of the objects on the image sensor was computed. Thus, inter-vehicle distance was expressed as a product of similitude ratio and focal length of a digital imaging device. Distance measurements were performed from 2 to 15 m at day and night. Using this method, less than ±5% error ratios have been obtained at almost all of measurement points. Results indicate that the method would be an alternative of established ranging methods for driving safety support systems.