MACHINE VISION n The Networking Game Changer for Industrial Automation The EDS-4000/G4000 Series is the all-new futureproof layer 2 Ethernet switch, featuring IEC 62443-4-2 certified security, advanced user experience with web GUI, as well as high performance with 802.3bt PoE and 2.5G fibre uplinks. The portfolio includes 68 models across 7 series with options ranging from 8 to 14 ports. +44 (0) 1923 853434 | info@pes-group.co.uk | www.pes-group.co.uk How to choose machine vision lighting systems Correct lighting of machine vision applications is crucial if they are to perform reliably and consistently. Earl Yardley, director of Industrial Vision Systems (IVS), outlines some of the factors you need to consider when specifying and installing vision lighting schemes. Lighting is a critical element in automated visual inspection installations. Consistent lighting at the correct angle, of the correct wavelength and with the right lux levels, allows automated inspection to be robust and reliable. But how do you choose the best light for your machine vision applications? Lighting is critical because it enables the camera to see necessary details. Poor lighting is a major cause of failure in machine vision systems. For any application, there are three common lighting goals: n maximising the feature contrast of the part or object being inspected; n minimising contrast on features not of interest; and n removing distractions and variations to achieve consistency. The positioning and type of lighting is key to maximising contrast of the features being inspected and minimising everything else. The diagram (Fig 1) shows the positioning matrix of machine vision lighting. Where inspection takes place on production lines depends on the quality checking requirements. This part of the process may include what is referred to as “staging”. This is the equivalent of putting an actor centre stage in a theatre in the best possible place for the audience to see. Staging in machine vision is often mechanical and is required to: n ensure that the correct part surface is facing the camera – it may need to be rotated if several surfaces need inspecting; n hold the part still for the moment that the camera or lens captures the image; n put the part consistently in the same place within the overall “scene” to make it easy for the processor to analyse; and n provide fixed machine vision lighting for each inspection process. We also need to consider the inspection environment. The choice of lighting can be compromised by access to the object being inspected. Ambient lighting such as factory lights or sunlight can also affect the quality and reliability of inspection and must be factored into the lighting system design. Finally, you need to consider the interaction between the lighting and the object being inspected. The object’s shape, composition, geometry, reflectivity, topography and colour will all determine how light is reflected to the camera and the subsequent impact on image acquisition, processing and measurement. To improve the yield, robustness and long-term effectiveness of automated inspection systems, it is imperative to have the best lightingin place. There is often no substitute to testing alternative schemes. n Correct lighting is critical to the performance of machine vision systems Fig 1: There are a variety of ways to light a machine vision application
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