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Proceedings Paper

Real-time edge extraction by active defocusing
Author(s): Y.Y. Hung; Quiming Zhu; Dahuan Shi; Shouhong Tang
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Paper Abstract

A novel edge extraction method that employs an active defocusing technique is presented. The method is based on the principle that a Laplacian of Gaussian(LOG) operator can be well approximated by a Difference of Gaussian(DOG) operation.. While such operation can be done by digital processing, it is more effective to be conducted in a combination of optical and digital processing techniques. In this edge extraction process, a focused image of object in scene is first acquired. Image of the scene is then slightly defocused by changing the focal length of camera lens. Real time subtraction is applied to the defocused and the previously acquired images. It produces a residual image that emphasizes abrupt intensity variations, which are typical of edges in the image. An objective evaluation called edge index is performed on the resulting image. Amount of defocusing is carefully adjusted according to this measurement so that a desired edge image is generated. Boundaries of objects can then be obtained by further enhancement of the edge image. Since this edge detection method is an optical-based process aided by digital processing, it is rather fast and less expansive.

Paper Details

Date Published: 1 January 1991
PDF: 11 pages
Proc. SPIE 1332, Optical Testing and Metrology III: Recent Advances in Industrial Optical Inspection, (1 January 1991); doi: 10.1117/12.51083
Show Author Affiliations
Y.Y. Hung, Oakland Univ. (United States)
Quiming Zhu, Oakland Univ. (United States)
Dahuan Shi, Oakland Univ. (United States)
Shouhong Tang, Oakland Univ. (United States)


Published in SPIE Proceedings Vol. 1332:
Optical Testing and Metrology III: Recent Advances in Industrial Optical Inspection
Chander Prakash Grover, Editor(s)

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