imaging and machine vision europe october/november 2011 www.imveurope.com


Image courtesy of Microscan.


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traceability Code trackers


Rob Coppinger finds that vision systems are now required to track smaller and smaller markings that whizz past on ever-faster conveyors


As with any application of vision technology, resolution is everything. This applies just as much to code reading, for track and trace purposes, as it does to any other, even though a simple barcode or QR code may appear to be much less complex than the target objects in other markets. The trend towards traceability has


provided a rich vein of applications for the vision industry, from individual parts to pharmaceutical bottles, to boxes containing finished product. In each case, the item being tracked will contain an individual, unique, identifying mark. Those markings can be the 1D barcode, to be found on any supermarket product’s packaging, or the 2D square codes, also known as Data Matrix Codes (DMC), that are favoured for mobile phone-related promotions, or human readable markings, – which, as the name suggests, are where people can read the information. While the majority of marking systems can be printed directly on to the subject to be tracked, there is also the markings application technique called data- peening. This causes small indentations in the surface of a metal part and the DMC can be made up of these indentations. The challenge for tracking is that, over


time, as parts and products travel through the production system or wider supply chain, the markings can become degraded either through damage or dirt. If a marking becomes illegible and is misread, traceability is undermined. While lasers have been used to read 1D barcodes the advancement of vision- based readers has made the active solution less competitive, because of the difficulty of damage and degradation to the markings in the industrial environment. Lasers generally require markings in good condition with a contrast level of around 80 per cent between


Speed is of the essence for code reading with ever faster conveyors


foreground and background, but vision-based image interpretation software can cope with a range of conditions. Another advantage vision systems have is that they are more rugged, as they are solid-state technology so they last longer than the more complicated lasers with their many components. And with vision systems now offering 10 Megapixels (and greater than 15 Megapixels expected in a few years) the Gigabit Ethernet interface camera with its CCD or CMOS sensor technology has few rivals. Cognex UK and Ireland district sales manager Leigh Jordan expects CCD and CMOS to be the leading sensor technologies for some time to come. Microscan’s machine vision product manager Jonathan Ludlow agrees. He also expects the distinction between CCD and CMOS to diminish in future. ‘In a few years CMOS could equal CCD in quality,’ he says. CCD has been more expensive than CMOS,


but it provided better-quality images. CMOS however is improving and Ludlow expects that quality and cost difference to fade. Usually, if a marking is degraded or if a


product is not orientated correctly within the field of view of the reader, then no code will be detected. To cope with industrial environments, where many marked products are conveyed, but not sufficiently controlled to be orientated correctly, multiple cameras are a solution. But, like any technology, there is a cost attached to greater capability and more competent vision systems. German company Seidenader Vision, which manufactures optical inspection systems for the pharmaceutical industry, has produced its SV360 vision module with six cameras that reads 2D codes by capturing 360° images of products including bottles. The six cameras have integrated LED flashes that are positioned at an angular distance of 60°. When a product


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