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Locating shapes in two-dimensional space curves

  • US 5,751,853 A
  • Filed: 01/02/1996
  • Issued: 05/12/1998
  • Est. Priority Date: 01/02/1996
  • Status: Expired due to Term
First Claim
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1. A method for finding a feature of an object by finding at least one instance of a model two-dimensional space curve that represents the feature within a target two-dimensional space curve in an image that represents at least a portion of the object, the method comprising the steps of:

  • at train-time;

    acquiring said model two-dimensional space curve, said model two-dimensional space curve including a plurality of points, each point being characterized by a position in two dimensions, said position being a function of distance S along said model two-dimensional space curve;

    for each of said plurality of points of said model two-dimensional space curve, converting said position in two dimensions as a function of distance S into an angle as a function of distance S to provide an angle-based model space curve; and

    at run-time;

    acquiring said target two-dimensional space curve, said target two-dimensional space curve including a plurality of points, each point being characterized by a position in two dimensions, said position being a function of distance S along said target two-dimensional space curve;

    for each of said plurality of points of said target two-dimensional space curve, converting said position in two dimensions as a function of distance S into an angle as a function of distance S to provide an angle-based target space curve; and

    using said angle-based model space curve to find at least one position along said angle-based target space curve that results in a match metric value that exceeds a match threshold.

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