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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    International journal of computer vision 27 (1998), S. 127-159 
    ISSN: 1573-1405
    Keywords: model-based vision ; object recognition ; alignment ; noise ; uncertainty ; error propagation ; linear programming ; perspective ; scaled-orthographic ; bounded error ; Gaussian error
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Robust recognition systems require a careful understanding of the effects of error in sensed features. In model-based recognition, matches between model features and sensed image features typically are used to compute a model pose and then project the unmatched model features into the image. The error in the image features results in uncertainty in the projected model features. We first show how error propagates when poses are based on three pairs of 3D model and 2D image points. In particular, we show how to simply and efficiently compute the distributed region in the image where an unmatched model point might appear, for both Gaussian and bounded error in the detection of image points, and for both scaled-orthographic and perspective projection models. Next, we provide geometric and experimental analyses to indicate when this linear approximation will succeed and when it will fail. Then, based on the linear approximation, we show how we can utilize Linear Programming to compute bounded propagated error regions for any number of initial matches. Finally, we use these results to extend, from two-dimensional to three-dimensional objects, robust implementations of alignment, interpretation-tree search, and transformation clustering.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    International journal of computer vision 25 (1997), S. 145-166 
    ISSN: 1573-1405
    Keywords: object recognition ; occlusion ; affine ; perspective ; regions ; pose estimation ; uniqueness ; two-dimensional ; three-dimensional ; model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Recognition systems attempt to recover information about the identity of observed objects and their location in the environment. A fundamental problem in recognition is pose estimation. This is the problem of using a correspondence between some portions of an object model and some portions of an image to determine whether the image contains an instance of the object, and, in case it does, to determine the transformation that relates the model to the image. The current approaches to this problem are divided into methods that use “global” properties of the object (e.g., centroid and moments of inertia) and methods that use “local” properties of the object (e.g., corners and line segments). Global properties are sensitive to occlusion and, specifically, to self occlusion. Local properties are difficult to locate reliably, and their matching involves intensive computation. We present a novel method for recognition that uses region information. In our approach the model and the image are divided into regions. Given a match between subsets of regions (without any explicit correspondence between different pieces of the regions) the alignment transformation is computed. The method applies to planar objects under similarity, affine, and projective transformations and to projections of 3-D objects undergoing affine and projective transformations. The new approach combines many of the advantages of the previous two approaches, while avoiding some of their pitfalls. Like the global methods, our approach makes use of region information that reflects the true shape of the object. But like local methods, our approach can handle occlusion.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    International journal of computer vision 13 (1994), S. 7-32 
    ISSN: 1573-1405
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Affine transformations of the plane have been used in a number of model-based recognition systems. Because the underlying mathematics are based on exact data, in practice various heuristics are used to adapt the methods to real data where there is positional uncertainty. This paper provides a precise analysis of affine point matching under uncertainty. We obtain an expression for the range of affine-invariant values that are consistent with a given set of four points, where each image point lies in an ∈-disc of uncertainty. This range is shown to depend on the actualx-y-positions of the data points. In other words, given uncertainty in the data there are no representations that are invariant with respect to the Cartesian coordinate system of the data. This is problematic for methods, such as geometric hashing, that are based on affine-invariant representations. We also analyze the effect that uncertainty has on the probability that recognition methods using affine transformations will find false positive matches. We find that there is a significant probability of false positives with even moderate levels of sensor error, suggesting the importance of good verification techniques and good grouping techniques.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    International journal of computer vision 21 (1997), S. 123-153 
    ISSN: 1573-1405
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We consider the problem of analytically characterizing the set of all 2-D images that a group of 3-D features may produce, and demonstrate that this is a useful thing to do. Our results apply for simple point features and point features with associated orientation vectors when we model projection as a 3-D to 2-D affine transformation. We show how to represent the set of images that a group of 3-D points produces with two lines (1-D subspaces), one in each of two orthogonal, high-dimensional spaces, where a single image group corresponds to one point in each space. The images of groups of oriented point features can be represented by a 2-D hyperbolic surface in a single high-dimensional space. The problem of matching an image to models is essentially reduced to the problem of matching a point to simple geometric structures. Moreover, we show that these are the simplest and lowest dimensional representations possible for these cases. We demonstrate the value of this way of approaching matching by applying our results to a variety of vision problems. In particular, we use this result to build a space-efficient indexing system that performs 3-D to 2-D matching by table lookup. This system is analytically built and accessed, accounts for the effects of sensing error, and is tested on real images. We also derive new results concerning the existence of invariants and non-accidental properties in this domain. Finally, we show that oriented points present unexpected difficulties: indexing requires fundamentally more space with oriented than with simple points, we must use more images in a motion sequence to determine the affine structure of oriented points, and the linear combinations result does not hold for oriented points.
    Type of Medium: Electronic Resource
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  • 5
    Publication Date: 1998-11-01
    Print ISSN: 0031-3203
    Electronic ISSN: 1873-5142
    Topics: Computer Science
    Published by Elsevier
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  • 6
    Publication Date: 2013-07-17
    Print ISSN: 0932-8092
    Electronic ISSN: 1432-1769
    Topics: Computer Science
    Published by Springer
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  • 7
    Publication Date: 1977-08-01
    Print ISSN: 0008-543X
    Electronic ISSN: 1097-0142
    Topics: Biology , Medicine
    Published by Wiley on behalf of American Cancer Society.
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  • 8
    Publication Date: 1966-11-11
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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