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.