What are Vision Systems?

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Vision systems have been used in industry for over thirty years and with an active research community, the potential applications are always increasing. Anything from reading text to checking dimensions, colour or orientation can be performed with vision systems.

Vision Systems Hardware

Vision systems are computer-based programmes that analyse images of 'products'. The images are taken using a type of video camera which is usually about the size of two matchboxes. Most vision systems work in 'grey-scale' (black and white) and this is usually more than adequate. Where colour is necessary it can add to the cost considerably. A specialised type of camera is a 'linescan camera'. These work in a similar way to photocopiers or scanners: they take a thin line image and then use the movement of the production line to create a scanning effect. This is often used by vision systems in the printing industry.

The processing may be carried out by an ordinary PC or a proprietary unit such as a 'smart camera' (some vision systems are 'all-in-one', others offer a modular approach). In the case of PC-based vision systems the necessary additions are input and output capabilities (this may be a digital I/O card, RS232 or ethernet) and the ability to capture an image. Image capture usually requires a 'framegrabber' board which digitises the camera image so that it can be processed.

Finally, and most importantly, is lighting. The lighting for vision systems may have to be highly specialised to highlight or minimise the effect of certain features. There are numerous lighting solutions to any one application, some to reduce reflections, others to create shadows and some that use a combination of techniques to give the ideal solution.

A customer's requirements will usually dictate the vision systems hardware required.

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The images are taken using a type of video camera which is usually about the size of two matchboxes.

Vision Systems Software

There must also be some kind of vision system software for PC-based vision systems. Some companies offer modular solutions, others provide a software suite with many built-in features. Some of the modular solutions are not sold in a production-ready format and require programming to produce a graphical user interface and the necessary analysis. The choice here is between a wide capability (which often helps to solve unforeseen variations in the production environment) and a narrowly-focussed but highly-able system. Typical tools include dimensional verification (non-contact gauging), text reading (OCR), print quality checks (OCV), presence/absence of components, position checks and colour analysis.

In the pharmaceutical sector, FDA 21 CFR part 11 rules requires that software and electronic records are validated, MVT can provide FDA 21 CFR part 11 compliant solutions.

MVT's experience means that we are able to choose from a number of software suppliers in order to best meet the specification from a customer. This may be a standard package or a customised solution.

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Installations can consist of one or more cameras and may communicate with a PLC to activate a reject mechanism or signal pass/fail outputs to an operator.

Vision Systems Installation

Vision systems are typically installed on a production line with the camera above or to the side with the processing part of the system usually stored to one side or underneath the line. Vision systems are usually specified so as not to reduce the speed of the line. They can consist of one or more cameras and may communicate with a PLC to activate a reject mechanism or signal pass/fail outputs to an operator.

In general terms vision systems are more reliable if variations can either be minimised or accounted for. So, for example, a vision system installed near a window or skylight will often benefit from shielding to minimise the effect of changes in outside brightness. A vision system installation is a 'dumb machine' that must either be told of the expected variations in products and its environment or be shielded from them.

MVT has experience on a large number of different applications and industries. Contact us and see how we can help you.

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