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Proceedings Paper

Automatic visual inspection of centering marks engraved on ophthalmic lenses
Author(s): Xavier Fernandez; Salvador Bosch
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Paper Abstract

We present a complete procedure for automated inspection of engraved marks and ink marks placed on ophthalmic lenses. The engraved marks are small and weak, and are partially occluded by ink marks. The whole sense is noisy and has low contrast. A preprocessing for image enhancement is first performed. Then, a simplified numerical correlation algorithm is applied, resulting in a fast and accurate positioning of the marks. The procedure includes designing a model for the target, in a way that greatly reduces the volume of computed data. Three figures of merit are defined to ensure the robustness of the whole procedure: the contrast of the target on the background, the uniqueness of the correlation peak, and the similarity between target and model. By comparison of these figures against suitable threshold levels, decisions based on existence, multiplicity and completeness of the marks can be taken.

Paper Details

Date Published: 23 November 1994
PDF: 9 pages
Proc. SPIE 2249, Automated 3D and 2D Vision, (23 November 1994); doi: 10.1117/12.196113
Show Author Affiliations
Xavier Fernandez, Industrias de Optica, SA (Spain)
Salvador Bosch, Univ. de Barcelona (Spain)

Published in SPIE Proceedings Vol. 2249:
Automated 3D and 2D Vision
Rolf-Juergen Ahlers; Donald W. Braggins; Gary W. Kamerman, Editor(s)

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