Methods and systems for accurately recognizing vehicle license plates
First Claim
Patent Images
1. A license plate detection and recognition system with temporal validation, said system comprising:
- a license plate detection unit;
a character detection unit;
a character recognition unit;
a post-processor;
a processor, a memory element coupled to the processor, and encoded instructions, when implemented by the processor, cause the system to;
detect one or more regions within one and/or a plurality of captured or stored image frames comprising a license plate within a detected vehicle by the license plate detection unit;
detect one or more clusters of characters in each of a filtered binarized image of the detected regions and send the one or more detected clusters to the character recognition unit for recognition of characters;
send the recognized characters to the post-processor for temporal validation, wherein the post-processor considers placement of the recognized characters across a plurality of image frames and a set of characters that denote a different alignment or placement in a minority of frames are flagged as outliers and discarded; and
compute a weighted probability for each of any remaining recognized characters with an ambiguity (at least two character possibilities) by multiplying a number of frames that recognized the character/total number of frames by a confidence value in percentage for each of the at least two character possibilities and validate the character with the higher weighted probability, thereby resolving the ambiguity.
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Abstract
The present invention discloses methods, systems and computer programmable products for detecting license plates and recognizing characters in the license plates. The system receives an image and identifies one or more regions including a license plate. The one or more regions are converted into a plurality of binarized images, which are then filtered to remove noise. Next, one or more clusters of characters are identified in the plurality of binarized images. The one or more clusters of characters are analyzed to recognize a set of characters, wherein each character in the set includes a confidence value.
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Citations
20 Claims
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1. A license plate detection and recognition system with temporal validation, said system comprising:
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a license plate detection unit; a character detection unit; a character recognition unit; a post-processor; a processor, a memory element coupled to the processor, and encoded instructions, when implemented by the processor, cause the system to; detect one or more regions within one and/or a plurality of captured or stored image frames comprising a license plate within a detected vehicle by the license plate detection unit; detect one or more clusters of characters in each of a filtered binarized image of the detected regions and send the one or more detected clusters to the character recognition unit for recognition of characters; send the recognized characters to the post-processor for temporal validation, wherein the post-processor considers placement of the recognized characters across a plurality of image frames and a set of characters that denote a different alignment or placement in a minority of frames are flagged as outliers and discarded; and compute a weighted probability for each of any remaining recognized characters with an ambiguity (at least two character possibilities) by multiplying a number of frames that recognized the character/total number of frames by a confidence value in percentage for each of the at least two character possibilities and validate the character with the higher weighted probability, thereby resolving the ambiguity. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A license plate detection and recognition system using temporal validation to resolve any ambiguity of a recognized character, said system comprising:
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a post-processor; a processor, a memory element coupled to the processor, and encoded instructions, when implemented by the processor, cause the system to; send recognized characters from a detected one or more clusters of characters in each of a filtered binarized image of detected regions within one and/or a plurality of captured or stored images frames comprising at least a portion of a license plate to the post-processor for temporal validation, wherein the post-processor considers placement of the recognized characters across a plurality of image frames and a set of characters that denote a different alignment or placement in a minority of frames are flagged as outliers and discarded; and compute a weighted probability for each of any remaining recognized characters with an ambiguity (at least two character possibilities) by multiplying a number of frames that recognized the character/total number of frames by a confidence value in percentage for each of the at least two character possibilities and validate the character with the higher weighted probability, thereby resolving the ambiguity. - View Dependent Claims (14, 15, 16, 17, 18, 19)
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20. A license plate detection and recognition method using temporal validation to resolve any ambiguity of a recognized character, said method comprising the steps of:
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detecting one or more regions within one and/or a plurality of captured or stored image frames comprising a license plate within a detected vehicle by the license plate detection unit; detecting one or more clusters of characters in each of a filtered binarized image of the detected regions and send the one or more detected clusters to the character recognition unit for recognition of characters; sending the recognized characters to the post-processor for temporal validation, wherein the post-processor considers placement of the recognized characters across a plurality of image frames and a set of characters that denote a different alignment or placement in a minority of frames are flagged as outliers and discarded; and computing a weighted probability for each of any remaining recognized characters with an ambiguity (at least two character possibilities) by multiplying a number of frames that recognized the character/total number of frames by a confidence value in percentage for each of the at least two character possibilities and validating the character with the higher weighted probability, thereby resolving the ambiguity.
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Specification