Patent ID: 6754369
Filing Date: 2004-06-22
Classification: G06K

Abstract:
A license plate reading apparatus comprising:an image pickup unit, provided above a road, to photograph a running vehicle at a predetermined frame period; an image storing unit to successively store two images of a present frame image and a previous frame image photographed by said image pickup unit; a vehicle detecting unit to detect a motion of a license plate in a front portion of said running vehicle on the basis of a difference between the present frame image and the previous frame image stored in said image storing unit; a dictionary in which character images of all characters used for the license plate have been registered; and a character recognizing unit to recognize all of the characters on the license plate from an image in a license plate area detected by said vehicle detecting unit by collating with the character images registered in said character image dictionary, wherein said vehicle detecting unit comprises: a block dividing unit to divide each of said present frame image and said previous frame image into blocks of a predetermined pixel size; a vector calculating unit to calculate a motion vector of the block by obtaining a pixel position, as a block moving position, in which a sum of differences between each pixel in the block of said previous frame image and all pixels in the block of said present frame image becomes the minimum; and a vehicle head detecting unit to scan all of the blocks, to search a group of blocks in which sizes and directions of the motion vectors are almost the same in an area of a rectangular size corresponding to the license plate, to detect the vehicle on the basis of the presence or absence of said group of blocks which satisfy said conditions, and at the same time, to detect a license plate area at the head of the vehicle.