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Proceedings Paper

Inspection of float glass using a novel retroreflective laser scanning system
Author(s): Jonathan D. Holmes
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Paper Abstract

Since 1988, Image Automation has marketed a float glass inspection system using a novel retro-reflective laser scanning system. The (patented) instrument scans a laser beam by use of a polygon through the glass onto a retro-reflective screen, and collects the retro-reflected light off the polygon, such that a stationary image of the moving spot on the screen is produced. The spot image is then analyzed for optical effects introduced by defects within the glass, which typically distort and attenuate the scanned laser beam, by use of suitable detectors. The inspection system processing provides output of defect size, shape and severity, to the factory network for use in rejection or sorting of glass plates to the end customer. This paper briefly describes the principles of operation, the system architecture, and limitations to sensitivity and measurement repeatability. New instruments based on the retro-reflective scanning method have recently been developed. The principles and implementation are described. They include: (1) Simultaneous detection of defects within the glass and defects in a mirror coating on the glass surface using polarized light. (2) A novel distortion detector for very dark glass. (3) Measurement of optical quality (flatness/refractive homogeneity) of the glass using a position sensitive detector.

Paper Details

Date Published: 7 July 1997
PDF: 11 pages
Proc. SPIE 3131, Optical Scanning Systems: Design and Applications, (7 July 1997); doi: 10.1117/12.277748
Show Author Affiliations
Jonathan D. Holmes, Image Automation Ltd. (United Kingdom)


Published in SPIE Proceedings Vol. 3131:
Optical Scanning Systems: Design and Applications
Leo Beiser; Stephen F. Sagan, Editor(s)

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