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Proceedings Paper

Evaluation procedure for imaging in web inspection
Author(s): Jyrki Laitinen
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Paper Abstract

Experience from actual web inspection systems has shown that the quality of the image is crucial for the performance of the whole inspection system. Even the most sophisticated image processing methods or computer hardware cannot compensate for low quality images. In this paper the key characteristics affecting the image formation and test set-ups to measure the numerical values of these characteristics are introduced. The determination of the imaging properties is based on imaging known test targets and subsequent image analysis. Modulation transfer function, vignetting, noise and pixel-to-pixel non-uniformity values for typical image forming systems are given. The sensitivity of these characteristics is estimated by measuring their numerical values as a function of some key imaging parameters like f-number or the spectral range of illumination. The information content of defective surface samples picked from a steel manufacturing process is compared to the results of the test set-up measurements to demonstrate the relation between the quality of the image formation in web inspection and the measured imaging characteristics. As a conclusion, an image formation evaluation procedure is proposed. The possibility to optimize the performance of the image formation using the information from the evaluation procedure is discussed. Key words: visual surface inspection, web inspection, imaging.

Paper Details

Date Published: 6 January 1994
PDF: 12 pages
Proc. SPIE 2348, Imaging and Illumination for Metrology and Inspection, (6 January 1994); doi: 10.1117/12.198842
Show Author Affiliations
Jyrki Laitinen, Technical Research Ctr. of Finland (Finland)


Published in SPIE Proceedings Vol. 2348:
Imaging and Illumination for Metrology and Inspection
Donald J. Svetkoff, Editor(s)

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