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Proceedings Paper

Stereovision-based close-up dimensional inspection
Author(s): J. Phillip Mitchell; Allan D. Spence; David W. Capson; Harley Chan; Marc Goldstein
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Paper Abstract

Sheet metal strain analysis is an important tool to ensure products are manufactured within necessary tolerances. A common technique involves electrochemically etching a dark grid pattern of known size onto the flat sheet metal surface and then deforming the sheet. The change in the grid pattern after deformation can be used to calculate surface strain. The computer vision problem is to accurately detect the intersections of the grid pattern. To investigate this problem, a stereo camera system was designed and attached to a bridge style coordinate measurement machine. The stereo head consists of two high resolution monochrome CCD cameras mounted on a Renishaw PH10 motorized probe head that can be articulated into numerous, repeatable, preset positions. Stereo head calibration was achieved using Zhang’s technique with a planar target. Each probe position was calibrated using a global point set registration method to link coordinate systems. A novel approach to segmenting the grid pattern into squares involving region merging and watersheds is described. Grid intersections are determined to sub pixel accuracy and matched between images using a correlation based scheme. The accuracy of the system and experimental results are provided.

Paper Details

Date Published: 24 February 2005
PDF: 12 pages
Proc. SPIE 5679, Machine Vision Applications in Industrial Inspection XIII, (24 February 2005); doi: 10.1117/12.585918
Show Author Affiliations
J. Phillip Mitchell, McMaster Univ. (Canada)
Allan D. Spence, McMaster Univ. (Canada)
David W. Capson, McMaster Univ. (Canada)
Harley Chan, McMaster Univ. (Canada)
Marc Goldstein, McMaster Univ. (Canada)

Published in SPIE Proceedings Vol. 5679:
Machine Vision Applications in Industrial Inspection XIII
Jeffery R. Price; Fabrice Meriaudeau, Editor(s)

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