CAMERA CONTROL METHOD FOR VEHICLE NUMBER PLATE RECOGNITION
First Claim
1. A camera control method for vehicle license plate recognition system comprising the steps of;
- building up a lookup table of electronic shutter speed and gain level to generate images of various brightness levels;
archiving the created lookup table on to a memory of a camera;
calculating average value of image brightness;
writing multiple parameters of electronic shutter speed and gain level that match with the calculated average brightness value in the lookup table to a camera control register; and
outputting series of images of various brightness that are captured under various shutter speeds and gain levels by the control from the camera register.
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Abstract
This development is about the camera control method for a vehicle license plate recognition system. In detail, it is about the applying variable shutter speed and gain level per image frames that are captured through a CCTV camera of vehicle license plate recognition system. The entire control is done through 3 steps. The first step is to build up a lookup table of electronic shutter speed and gain level to generate images of various brightness levels and archive the created lookup table on to a memory of a camera. The second step is to calculate the average value of image brightness and write the multiple parameters of electronic shutter speed and gain level that match with the calculated average brightness value in the lookup table to a camera control register. The third step is to output series of images of various brightness that are captured under various shutter speeds and gain levels by the control from the camera register. This development is to get series of images with various brightness instantly by adjusting shutter speed and gain level of each frame to avoid recognition failure due to inadequate (too bright or too dark in recognizing numbers in a plate) image frame in harsh conditions such as strong sun lights or fluctuating brightness, which may confuse camera in controlling shutter speed and gain level for getting proper images to recognize.
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Citations
20 Claims
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1. A camera control method for vehicle license plate recognition system comprising the steps of;
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building up a lookup table of electronic shutter speed and gain level to generate images of various brightness levels; archiving the created lookup table on to a memory of a camera; calculating average value of image brightness; writing multiple parameters of electronic shutter speed and gain level that match with the calculated average brightness value in the lookup table to a camera control register; and outputting series of images of various brightness that are captured under various shutter speeds and gain levels by the control from the camera register. - View Dependent Claims (2, 3, 4, 5)
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6. A method for generating images for a character recognition system, comprising:
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capturing a reference image from a camera, the captured reference image being defined by an average brightness level; deriving a series of stepped shutter speed values and corresponding gain level values from a lookup table based upon the average brightness level of the reference image; and generating a set of the output images to the character recognition system, the output images being captured according to each one of the series of stepped shutter speed values and corresponding gain level values. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14)
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15. An imaging subsystem for a vehicle number plate recognition system, comprising:
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a camera including an image sensor and a signal converter; an image processor in communication with the camera, a brightness value of a reference digital image data captured by the image sensor and digitized by the signal converter being derived by the image processor; a lookup table containing a series of shutter speed values and gain values corresponding to the brightness value of the reference digital image data; and an image output interface receiving a plurality of adjusted images from the camera, each of the adjusted images being correlated to a one of the series of shutter speed values and gain values, the image output interface being in communication with the vehicle number plate recognition system. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification