Abstract: A video camera produces an image of a license plate on a vehicle, and a scanning apparatus finds a license plate number in the image. The identification of the license plate number is verified in a confidence check section by checking for the presence of a state logo. Next, a character extractor identifies individual characters of the number by finding and tracing a contour along interior portions of the character edges, and the contour length, character height, and character width are then checked in a validity checking section to determine whether they are within predetermined acceptable ranges. To correct for obscuring objects on the license plate, a character alignment section determines the top line and baseline of the license plate number and disregards portions of the characters that appear to be outside of these limits, and a license plate frame correction section is utilized to extract the characters when a portion thereof is obscured by a license plate frame.

Abstract: An optical system produces an image of a set of characters on a background. A flash light source directs uniform illumination toward the set of characters for a predetermined flash period having an intensity chosen to exceed the intensity of corrupting light from the environment, such as sun light, street lights or car lights. A first polarizer is positioned to polarize the illumination from the flash light source prior to the light impinging on the set of characters, and a second polarizer is positioned to receive light reflected by the set of characters and the background. The second polarizer is cross-polarized with respect to the first polarizer so that it filters out polarized light from the flash light source that is reflected by the set of characters and background. An optical receiver is positioned to receive light from the second polarizer and produces an image of the set of characters and the background. A shutter is used to control the light received by the optical receiver.