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Geometric pre-correction for automatic license plate recognition

  • US 9,020,200 B2
  • Filed: 06/12/2012
  • Issued: 04/28/2015
  • Est. Priority Date: 06/12/2012
  • Status: Active Grant
First Claim
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1. A method for adjusting a license plate detected in a captured image, the method comprising:

  • providing at least one set of correction parameters, the providing the at least one correction matrix including;

    determining a feature set by calculating differences between the x,y coordinates of the four corners;

    determining an original plate geometry matrix V;

    of the feature set;

    determining an ideal plate geometry D, wherein vectors of the D matrix are defined by a height and width of an ideal rectangular plate;

    determining a corrected plate geometry CV.sub.i;

    determining a distance between the corrected plate geometry and the ideal plate geometry by subtracting the ideal plate geometry from the corrected plate geometry (CV.sub.i−

    D); and

    ,determining the at least one set of correction parameters by squaring a sum of all matrix entries for the license plates;

    receiving an input image representing a detected license plate;

    in response to receiving the input image, automatically adjusting the input image to obtain a corrected image using the at least one correction matrix.

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