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SYSTEM AND METHOD FOR DEFORMABLE OBJECT RECOGNITION

  • US 20090185715A1
  • Filed: 05/05/2008
  • Published: 07/23/2009
  • Est. Priority Date: 01/18/2008
  • Status: Active Grant
First Claim
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1. A method for recognizing a model object in images, under general nonlinear deformations, comprising the steps of:

  • (a) acquiring in electronic memory an image of the model object;

    (b) transforming the image of the model object into a multi-level representation consistent with a recursive subdivision of a search space, said multi-level representation including at least the image of the object;

    (c) generating at least one precomputed model of the model object for each level of discretization of the search space, said precomputed model consisting of a plurality of model points with corresponding direction vectors, said model points and direction vectors being generated by an image processing operation that returns a direction vector for each model point;

    (d) generating a subdivision of said plurality of model points into a plurality of parts, where a deformed instance of the model is represented by transforming the parts;

    (e) acquiring in electronic memory a search image;

    (f) transforming the search image into a multi-level representation consistent with the recursive subdivision of the search space, said multi-level representation including at least the search image;

    (g) performing an image processing operation on each transformed image of the multi-level representation that returns a direction vector for a subset of model points within said search image that corresponds to the range of transformations for which the at least one precomputed model should be searched;

    (h) computing a global match metric that combines the results of a local metric, where for the local metric the parts of the model are searched in a restricted range of transformations close to the precomputed model and the maximal fit of each part is taken as the contribution of said part to the global match metric;

    (i) determining those model poses whose match metric exceeds a user-selectable threshold and whose match metric is locally maximal, and generating a list of instances of the at least one precomputed model in the coarsest discretization level of the search space from the model poses;

    (j) computing a deformation transformation that describes the local displacements of the parts;

    (k) tracking said instances of the at least one precomputed model in the coarsest discretization level of the search space through the recursive subdivision of the search space until a finest level of discretization is reached;

    (l) computing at each level the respective deformation transformation and propagating said deformation transformation to the next level; and

    (m) providing the model pose and the deformation transformation of the instances of the model object on the finest level of discretization.

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