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Methods and systems for accurately recognizing vehicle license plates

  • US 10,706,330 B2
  • Filed: 09/14/2016
  • Issued: 07/07/2020
  • Est. Priority Date: 10/01/2015
  • Status: Active Grant
First Claim
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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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