Inspection
Multispectral illumination for glass sidewall inspection Brian Ensinger* discusses how Applied Vision designs multispectral illumination solutions for glass container sidewall inspection to help manufacturers operate with speed and efficiency.
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Defects require different approaches All glass container defects require a different lighting geometry and optical
can lead to more false rejects or defective containers escaping notice. Helping companies avoid compromises and implement effective sidewall inspection on their production lines has been an area of focus for Applied Vision for decades. Today, sidewall inspection is a priority for glass manufacturers intent on ensuring quality and reducing cost amid rising global demand for food and beverage containers. By continuing to develop proprietary tools and approaches, Applied Vision aims to deliver the next generation of ‘no-touch’ solutions for multispectral illumination of glass sidewall surfaces. � Fig 1. Multispectral illumination puts colour to work so that glass container manufacturers can optimise the accuracy, speed, and efficiency of sidewall inspections.
configuration to optimise detection accuracy and precision while minimising false rejects. That is, the illumination source and the illumination geometry must be developed to allow as many defects as possible to be detectable on the surface of the container, within the container, and below the surface (with some defects being highly detectable and others remaining less so). This is also dependent upon where the problem is occurring (Fig 1). In the past, using conventional lighting techniques, cameras, and geometries, it has often been necessary to compromise one type of defect detection for another. Essentially, the user must optimise lighting and settings for a particular defect of interest while working to minimise negative impacts to other inspections being performed. As a consequence, machine setup becomes more complicated and timeconsuming while detection capabilities are diminished for certain defects, which
Ahead of the curve Combining many sidewall defect detections into a single solution that helps to reduce false reject rates is achieved with Applied Vision’s patented approach to machine vision colour inspection. This methodology improves on incumbent approaches whereby defects compete (often unsuccessfully) for optimal lighting geometry, lensing and optics, and camera resolution within the inspection station. By leveraging high-resolution colour cameras and a configurable geometry of multispectral, software-controlled LEDs, the contours of the glass container being imaged cause different colours of light to be reflected back to the camera. Applied Vision designed a system that incorporates 16 equally spaced colour cameras and fully calibrated imaging geometry. This optical configuration also utilises a lensing principle to correct for perspective distortion in photographs. Within the inspection station, optics are positioned to place a horizontal ray of lower cameras at the base of the containers (viewing parallel across the Continued>>
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pplied Vision Corporation has engineered multispectral illumination solutions for all types of containers since 1997. As one of the first companies to utilise programmable, multispectral light-emitting diode (LED) light sources and colour cameras to benefit container inspection, Applied Vision has developed an approach that allows vision systems to acquire and process transparent, opaque, and other categories of defects from a single illumination pattern where each defect has its own optimal filtered light, thereby creating the best defect signature for detection. The use of colour illumination for glass container inspection can provide manufacturing facilities with a customisable solution when faced with process-induced defects and the ever-growing complexity of containers, particularly for foods and beverages. This led Applied Vision to engineer the Volcano inspection station that is fully programmable in terms of intensity, colour selection, and pattern geometry. It also uses the highest-quality colour LEDs available, which improves defect detection and recognition along with improved defect classification for both top-down and sidewall inspection regardless of heavy embossing, the colour of the glass, or even the thickness of the container. In tandem with highresolution color cameras, lensing and optics, powerful software, and selflearning algorithms, plant engineers and QA managers gain the ability to enhance or ‘tune’ images prior to applying inspections, thus supporting greater operational efficiency and consistency.
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