7 July 1997 Sensor system for subpixel geometry and surface inspection of cuboid and ring-shaped objects
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This paper addresses an application installed in quality control where a 100% inspection of geometry (3D) and surface of cuboid (parallelepiped) and ring-shaped magnets is done using a system of 2 CCD matrix cameras, one of which is equipped with on-board processing components and a transmitted-light sensor with microcontroller based data processing for the measurement of the height of the objects. The geometry and surface properties are measured with a diffuse indirect IR-LED flash and a telecentric lens to avoid perspective distortions due to different heights of the measured objects. The surface inspection looks for broken pieces, surface faults and cracks. The second CCD camera uses the same illumination and algorithm to inspect the surface of the other side of the objects after it has been turned around in a return conveyor belt. The main aspect of this paper is the theory of the geometry measurement including sub-pixel accuracy and the surface inspection using a telecentric lens and diffuse illumination. The geometry is measured with an accuracy of 1/3 pixels, independent of the background properties. Using a PentiumTM 100 processor the system is able to inspect up to 5 pieces per second.
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Markus Becker, Markus Becker, Juergen Weber, Juergen Weber, Erhard Schubert, Erhard Schubert, } "Sensor system for subpixel geometry and surface inspection of cuboid and ring-shaped objects", Proc. SPIE 3174, Videometrics V, (7 July 1997); doi: 10.1117/12.279787; https://doi.org/10.1117/12.279787

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