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1 March 1991 Computer vision system for automated inspection of molded plastic print wheels
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This research describes a robust, efficient, and real-time computer vision system that can automatically inspect defects of protruded print characters on injection molded plastic, typewriter print wheels. Possible defect types include insufficient fill, voids, and cracks. These defects can be described as poor edge sharpness, large edge position deviation from an established standard, and irregularities of the inside surface. Template matching is used for character detection and extraction. Matching performance measurements are used to evaluate closeness with respect to a reference print character of accepted quality. A hierarchical structure is used to improve the robustness of position detection and acceptable performance measures in knowledge rules are incorporated to increase the speed of the search. Characters are extracted from the image by a logical 'AND' operation in which a filled, slightly enlarged, uniform gray scale pattern of the print character is used as a template. Feature extraction and matching is done by using a distance image template matching technique which makes the system more robust and effective. Finally, a set of matching measurements is extracted to determine edge sharpness, edge deviation, and smoothness of the inside surface and local matching measurements are used for determining the detail of defects.
© (1991) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Yong-Lin Hu, William G. Wee, William A. Gruver, and Chia Yung Han "Computer vision system for automated inspection of molded plastic print wheels", Proc. SPIE 1468, Applications of Artificial Intelligence IX, (1 March 1991);

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