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Proceedings Paper

Edge Detection To Subpixel Accuracy
Author(s): R. Manmatha
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Paper Abstract

The accurate location of edges and boundaries in images is desirable for a number of reasons. Among the advantages include greater precision in the measurements of object sizes and locations and improved matching in stereo and rigid body motion studies. Here, a method to locate edges to subpixel accuracies is proposed. The imaging device is assumed to consist of an array of rectangular sensors. Edges are modelled as linear step functions of brightness over a window two pixels wide. Pixels are first marked as edge/non-edge using a conventional edge detector. The edge contrast is also obtained. It is shown that there exists a one to one mapping from the set of all possible intensities of pairs of adjacent "edge" pixels to the set of all edges passing through those pixels. A functional relation for the position and slope of the edges is thus obtained in terms of the pixel intensities.A two way ambiguity is resolved using a third pixel. The performance of the algorithm under noise was investigated using synthetic images. It is found that the edge location error is less than 0.05 pixel for signal to noise ratios greater than 15db. The method has been used to measure the width of a rectangular metal strip to within 0.05 pixel.

Paper Details

Date Published: 11 May 1987
PDF: 7 pages
Proc. SPIE 0786, Applications of Artificial Intelligence V, (11 May 1987); doi: 10.1117/12.940627
Show Author Affiliations
R. Manmatha, University of Hawaii (United States)

Published in SPIE Proceedings Vol. 0786:
Applications of Artificial Intelligence V
John F. Gilmore, Editor(s)

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