Performance Analysis of On-Line Camera-Based Web Inspection Sensors: A Pilot-Scale Experimental Study

Camera-based web inspection sensors have been available in the paper industry for many years. However, in recent years because of a market demand for high-quality paper products, the need for realtime flaw-detection systems has increased significantly. In addition to flaw-detection capabilities, these systems should be capable of doing defect classification (e.g., relative to size and type of flaws) as well as defect localization (providing information on location of flaws). The technique employed in flaw detection and measurement principles used in common systems are based on laser, CCD (charge coupled device) camera, or infrared technology. The study was designed to determine the capabilities of commercially available CCD camerabased systems. A CCD camera-based commercial sensor was installed on a pilot paper coater machine with the production speed capability of 1524 m/min (5000 ft/min) that could accept paper rolls with a width of 76.2 cm (30 inches). Various paper grades consisting of newsprint, coated paper, coated board, and linerboard which had typical grade-related defects were provided by various paper mills for testing. The purpose of this manuscript is to describe the operational principle, capabilities, and performance of various sensors used in paper industry in detecting various flaws and defects and to provide a summary of the results obtained using a commercial sensor