Hierarchical component based object recognition
First Claim
1. A method for constructing a hierarchical model consisting of the following steps:
- a) constructing an initial object decomposition into components based on a model image;
b) determining the relative poses of the components in a plurality of example images with respect to the model image;
c) determining whether a plurality of components moves in an identical or similar manner over the sequence of example images and, if so, grouping such components, resulting together with the ungrouped components in the object parts;
d) determining the relative poses of said grouped components in each example image;
e) forming a hierarchical model, consisting of a root object part at the top of the hierarchy and a plurality of object parts at lower levels of the hierarchy, from the object parts using an optimization criterion that takes into account the relative poses of the object parts; and
f) determining relative search spaces of the object parts to be used in the object recognition phase.
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Abstract
The present invention provides a method for the recognition of objects in an image, where the objects may consist of an arbitrary number of parts that are allowed to move with respect to each other. In the offline phase the invention automatically learns the relative movements of the single object parts from a sequence of example images and builds a hierarchical model that incorporates a description of the single object parts, the relations between the parts, and an efficient search strategy. This is done by analyzing the pose variations (e.g., variations in position, orientation, and scale) of the single object parts in the example images. The poses can be obtained by an arbitrary similarity measure for object recognition, e.g., normalized cross correlation, Hausdorff distance, generalized Hough transform, the modification of the generalized Hough transform, or the similarity measure. In the online phase the invention uses the hierarchical model to efficiently find the entire object in the search image. During the online phase only valid instances of the object are found, i.e., the object parts are not searched for in the entire image but only in a restricted portion of parameter space that is defined by the relations between the object parts within the hierarchical model, what facilitates an efficient search and makes a subsequent validation step unnecessary.
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Citations
46 Claims
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1. A method for constructing a hierarchical model consisting of the following steps:
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a) constructing an initial object decomposition into components based on a model image;
b) determining the relative poses of the components in a plurality of example images with respect to the model image;
c) determining whether a plurality of components moves in an identical or similar manner over the sequence of example images and, if so, grouping such components, resulting together with the ungrouped components in the object parts;
d) determining the relative poses of said grouped components in each example image;
e) forming a hierarchical model, consisting of a root object part at the top of the hierarchy and a plurality of object parts at lower levels of the hierarchy, from the object parts using an optimization criterion that takes into account the relative poses of the object parts; and
f) determining relative search spaces of the object parts to be used in the object recognition phase. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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27. A method for object recognition using a hierarchical model consisting of the following steps:
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a) finding the root object part of the hierarchical model in the search image;
b) using the found pose of the previous object parts to construct search spaces for the object parts in the next lower level of the object hierarchy;
c) searching the object parts in said search spaces;
d) iterating steps b) and c) until all object parts of the model hierarchy have been searched; and
e) providing the poses of all object parts. - View Dependent Claims (28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46)
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Specification