Computer Perception of Curved Objects Using a Television Camera
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1974Author
Turner, Kenneth J.
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Abstract
Various techniques are described for the computer perception
of curved objects (cups, mugs, toruses, etc.). Research has been
conducted in the areas of image-processing, object recognition,
3-d analysis, and scene analysis.
A representation of images in terms of lines is argued to be
superior to one in terms of regions. Line-finding is accomplished
by an edge-follower which can track round curved boundaries. A
new method of segmentation coupled to an improved procedure for
fitting conic sections is used to obtain a line-drawing from the
object boundaries. A topological description of the image is built
up in which junctions are classified according to a comprehensive
scheme applicable to pictures with both curved and straight lines.
'The performance of Barrow & Popplestone's program for recognising
irregular objects is evaluated, and it is demonstrated that
considerable improvements in speed. may be obtained by letting
gross features of an object, such as its outline, direct the matching. Objects may also be identified with a new form of Waltz's techniques, based on labelling-constraints derived from topological,
3-d object models. It is shown how the hierarchical synthesis
method for object recognition may be implemented so as to facilitate
flexible interaction. Good tolerance of imperfections and
rapidity of matching are achieved with this technique.
A qualitative measure of the shape of object surfaces is obtained
from examination of the intensity contours created by the
shading of reflected light. 3-d information is also acquired by
matching image descriptions with "procedural" models of a set of
prototype objects.
Scene analysis is performed by generalisations of the methods
devised by Waltz. Description and partition of a scene is carried
out using either models of specific objects or models of object
classes. Procedures are explained for generating labels for the
junctions caused by curved objects; the labels for a variety of
types of surface interactions are tabulated in an appendix.
A complete scene analysis system is described which integrates
the research efforts in these areas. Its performance on
simple scenes containing both curved and polyhedral objects is
assessed.
The thesis concludes with an appraisal of the results
achieved, with particular regard to future lines of development.