AMETEK Surface Vision’s Color Camera Inspection Systems Enhance Pulp Contaminant Detection in Paper Coating Applications
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AMETEK Surface Vision ¬¬— the leading provider of online surface inspection solutions for the plastics, nonwovens, and paper industries — offers a superior solution for inspection of coating applications in these markets.
AMETEK Surface Vision has a broad product portfolio optimized for web and surface inspection as well as monitoring and process surveillance applications, including the SmartAdvisor® monitoring system for process surveillance and SmartView® online web inspection technology.
SmartView’s modular concept provides the ideal front-end arrangement to ensure reliable data acquisition, combining a suitable light source with the best-fit sensor technology as well as image processing hardware and software.
Expert configuration is key. Typically, many paper inspection systems are set up for the light source to transmit through the product into the sensor, detecting defects such as holes, light and dark spots, and formation errors. However, for many coating applications, a reflection setup – combining brightfield and darkfield views with a sensor detecting reflected light – is more suitable.
AMETEK Surface Vision has developed more advanced configurations for coating processes, providing the contrast needed to detect topographical defects. Once defects are detected, image processing comes to the fore. Special algorithms are used to detect the defect area and classify it to the correct class.
For example, the streak threshold algorithm takes a single-line scan signal and averages it over several lines to generate a so-called averaged signal. This will average out any random background noise. A strong signal ratio from this process allows a background dynamic and a streak defect to be clearly distinguished.
Monochrome cameras make it difficult to distinguish differently colored defects. For instance, a red spot may need to be identified differently from a black spot in quality assessments but will appear the same to a monochrome camera. Monochrome cameras also find it difficult to detect peel-off defects on paper, which are much more easily detected by color cameras.
The best color information is obtained via reflection setups. Based on the product color, the system needs to have the flexibility to white balance the signal.
User-friendly software teaches the system about the product color, while auto calibration will correct the white balance information in the recipe. This allows users to run different product colors in time with the same color identification results.
The SmartView system measures values for hue, saturation, and intensity for each defect, enabling it to be clearly distinguished from surface colors.
Volker Koelmel, Surface Vision’s Global Manager – Plastics, Nonwovens & Paper, said: “Color camera installations provide the best defect identification for pulp applications in the paper industry, delivering the information that image processing and classification systems need to provide automated surface inspection that ensures a high-quality product.”
