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UBC Theses and Dissertations
Learning to recognize objects in images : acquiring and using probabilistic models of appearance Pope, Arthur R.
Abstract
We present a method of recognizing three-dimensional objects in intensity images of cluttered scenes, using models learned from training images. By modeling each object with a series of views, representing each view with a large variety of features, and describing each feature probabilistically, our method can learn to recognize objects of unusual complexity. An object is modeled by a probability distribution describing the range of possible variation in the object's appearance. This distribution is organized on two levels. Large variations are handled by partitioning training images into clusters corresponding to distinctly different views of the object. Within each cluster, smaller variations are represented by distributions characterizing uncertainty in the presence, position, and measurements of various discrete features of appearance. Many types of features may be used, ranging in abstraction from segments of intensity edges to perceptual groupings and regions. Our learning method combines two activities: (a) an incremental conceptual clustering algorithm identifies groups of training images corresponding to distinct views of the object; (b) a generalization algorithm consolidates each cluster to produce a summary description characterizing its most prominent features. The method produces models that are both economical and representative, balancing these competing goals through an application of the minimum description length principle. Recognition requires matching features of a model with those of an image. Our matching method is a form of alignment: from hypothesized feature pairings it estimates a viewpoint transformation; from that it finds additional pairings, and so on. The method uses constraints based on features' positions, numeric measurements, and relations, assigning to each an importance commensurate with its uncertainty as recorded by the model. Decisions are ordered so that more certain features are paired sooner, while ambiguous choices are postponed for later resolution, when additional constraints may be known. We also describe a system implemented to test our recognition learning method. Experiments demonstrate the system's performance at tasks including learning to recognize complex objects in cluttered scenes, and learning to discriminate two quite similar objects.
Item Metadata
Title |
Learning to recognize objects in images : acquiring and using probabilistic models of appearance
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
1995
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Description |
We present a method of recognizing three-dimensional objects in intensity images of cluttered
scenes, using models learned from training images. By modeling each object with a series
of views, representing each view with a large variety of features, and describing each feature
probabilistically, our method can learn to recognize objects of unusual complexity.
An object is modeled by a probability distribution describing the range of possible variation
in the object's appearance. This distribution is organized on two levels. Large variations are
handled by partitioning training images into clusters corresponding to distinctly different views
of the object. Within each cluster, smaller variations are represented by distributions characterizing
uncertainty in the presence, position, and measurements of various discrete features
of appearance. Many types of features may be used, ranging in abstraction from segments of
intensity edges to perceptual groupings and regions.
Our learning method combines two activities: (a) an incremental conceptual clustering algorithm
identifies groups of training images corresponding to distinct views of the object; (b)
a generalization algorithm consolidates each cluster to produce a summary description characterizing
its most prominent features. The method produces models that are both economical
and representative, balancing these competing goals through an application of the minimum
description length principle.
Recognition requires matching features of a model with those of an image. Our matching
method is a form of alignment: from hypothesized feature pairings it estimates a viewpoint
transformation; from that it finds additional pairings, and so on. The method uses constraints
based on features' positions, numeric measurements, and relations, assigning to each an importance
commensurate with its uncertainty as recorded by the model. Decisions are ordered so
that more certain features are paired sooner, while ambiguous choices are postponed for later
resolution, when additional constraints may be known.
We also describe a system implemented to test our recognition learning method. Experiments
demonstrate the system's performance at tasks including learning to recognize complex
objects in cluttered scenes, and learning to discriminate two quite similar objects.
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Extent |
22356221 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-02-18
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0051288
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
1996-05
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Media
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Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.