This invention provides an
infrared illuminator and camera
system for imaging of auto vehicle
license plates. The
system works in ambient light conditions,
ranging from bright
sunlight, to dim light, to dark, to zero ambient light. It yields high-
contrast imaging of the letters and numbers on retro-reflective
license plates. The images of the
license letter and number combinations can be read manually by a remote operator. They can be converted to text format with
optical character recognition computer hardware and
software. The text data can then be compared to data files listing license numbers to provide further data about the owner of a licensed vehicle. A decision can be made quickly about whether to allow a vehicle to proceed through a gate, or whether to take other action. The
system uses a mono camera that is enhanced for
infrared sensitivity and combined with a high power
infrared illuminator to maximize range at night, and with
shutter speeds set up to capture clear license plate pictures even with fast moving vehicles and even with their headlights on and interfering with human observation of the license plates. Optical filtering to pass infrared in the range of the illuminator and to reduce light outside this range, combines with a lens set up, to avoid vertical smear and sensor overload caused by headlights at night and by highlight reflected glare from the sun in
daytime.