License Plate Recognition (LPR) cameras are cameras which interface with specialized computer software to read license plate numbers. The camera takes a picture of the front and or rear plates of a vehicle, and feeds the picture to the software, which is able to identify the plate in the image and then isolate the number. LPR cameras have a wide number of applications including traffic enforcement, access control, stolen car identification, and vehicle tracking. Most industrialized nations incorporate LPR cameras into their law enforcement techniques.
Usually, LPR cameras are set up in a multiple unit configuration, so that shots can be taken from several angles. In addition to being used to identify a license plate, LPR cameras also take pictures of the car and driver in general, which can provide valuable information later. For example, someone who receives a traffic ticket because he or she ran a red light might claim that the computer software misidentified the plate. The photographic evidence showing a car matching the make, model, and color of the driver's car can be used to help prove the case in court, if necessary.
When an LPR camera needs to take a picture, it illuminates the plate using a light of a low wavelength which will not disrupt the driver. The illumination helps to increase the contrast of the plate, making the characters written on it more identifiable. The camera snaps a picture and sends it to a database for reading. The computer software, in turn, extracts the plate number, which can be used to allow a car into a secured parking area, issue a ticket to someone who has committed a traffic infraction, or to alert law enforcement to a stolen vehicle or a driver exceeding a certain speed, potentially posing a danger to others.
Because different nations use radically different license plates, LPR cameras must be customized for their area of use. The basic technology remains the same, however, making LPR cameras a much cheaper choice than some alternatives, like embedding transponders in cars to track them. The software technology used to back up LPR cameras is also greatly improved from earlier versions, and has a very low error rate. In addition, LPR cameras save law enforcement manpower, because law enforcement officers no longer need to go through every single suspicious picture by hand, or lie in wait at stoplights for traffic law violators.