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A thin layer of glossy coating presents one of the toughest presence/absence detection problems in packaging and quality inspection. It shows up when you try to inspect clear shrink-wrap safety bands on bottle closures or confirm that clear labels are present on the backing. On the production side, clear sugar coatings on lozenges and pills, and adhesive strips applied to envelopes, boxes and diapers present similar challenges. Luster sensors with easy-to-use teaching functions reliably discriminate between glossy and non-glossy surfaces. Luster sensors such as Omron’s model E3X-NL, shown in the examples above, provide more reliable detection than sensors that use conventional background suppression (BGS) technology. Before the introduction of the beam-splitting technology Omron calls “free angle optics,” only machine vision systems using carefully controlled lighting could provide the repeatability required for today’s high quality standards. Compared to the low-end vision sensors available today that can perform this task, the dedicated luster sensor is still less than one-third the price.

Luster Sensor Accurately Detects a Thin Clear Coating (.pdf) - Inspection Tools and Instruments