Vehicle license plate imaging and reading system for day and night
First Claim
1. A license plate reader system for all ambient light conditions, comprising a high power infrared illuminator for night and a monochrome camera that:
- a) is enhanced for infrared sensitivity and resolution;
b) has shutter speeds set up to capture clear license plate pictures on vehicles moving at any speed up to a predicted speed limit for the vehicles, even with their headlights on;
c) has optical filtering of light wavelengths outside the range of light wavelength emitted by the high power infrared illuminator, in order to avoid sensor overload from headlights and reflected glare from sunlight;
d) has high resolution and low inter-pixel leakage;
e) has a lens set up with a small aperture formed by an iris to avoid sensor overload, to increase depth of field for focused images of license plates on moving vehicles, and to avoid vertical smearing of images;
in which the high power infrared illuminator provides illumination of over a distance of at least 35 meters from the camera at an intensity to capture clear license plate pictures even with fast moving vehicles and even with their headlights on.
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Accused Products
Abstract
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.
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Citations
20 Claims
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1. A license plate reader system for all ambient light conditions, comprising a high power infrared illuminator for night and a monochrome camera that:
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a) is enhanced for infrared sensitivity and resolution; b) has shutter speeds set up to capture clear license plate pictures on vehicles moving at any speed up to a predicted speed limit for the vehicles, even with their headlights on; c) has optical filtering of light wavelengths outside the range of light wavelength emitted by the high power infrared illuminator, in order to avoid sensor overload from headlights and reflected glare from sunlight; d) has high resolution and low inter-pixel leakage; e) has a lens set up with a small aperture formed by an iris to avoid sensor overload, to increase depth of field for focused images of license plates on moving vehicles, and to avoid vertical smearing of images; in which the high power infrared illuminator provides illumination of over a distance of at least 35 meters from the camera at an intensity to capture clear license plate pictures even with fast moving vehicles and even with their headlights on. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification