Development of a License Plate Number Recognition System Incorporating Low- Resolution Cameras

A multi-lane free flow (MLFF) toll collection system installed on a simplified gantry requires compact cameras for supervising enforcement. Because these compact cameras have low image resolution, it is also necessary to develop vehicle license plate recognition technology that uses dynamic image processing. Mitsubishi Heavy Industries, Ltd. (MHI) has developed three technologies based on the conventional license plate recognition system using still images; these technologies improve image quality, process plural images of a single vehicle, and utilize a reference database. Laboratory evaluation tests have verified that even a lowresolution camera system can successfully recognize license plate numbers at a rate of 95% or better, comparable to results from the conventional still image system. MHI is enhancing system robustness to enable application of these technologies to actual products.