Vision technology comes of age
November 1st 2005

Don Braggins of the UK Industrial Vision Association discusses today's vision applications

It is some 25 years since industrial vision began to emerge as an industry in its own right and 13 years since the UK Industrial Vision Association was formed to promote the use of vision in manufacturing industry. The modern vision industry has come a long way from the days when it had to 'borrow' components developed for other applications.

Specialised cameras, camera interfaces, illumination systems and lenses are now available for machine vision applications.

As the technology has improved, the numbers of systems installed have increased more or less steadily year on year, while unit costs have dropped.

Figures published by the US Automated Imaging Association show that in Europe alone, over 40 000 'general purpose' vision systems were sold during 2003, with an average value of less than £6K (a value which is tending to move downwards).

Vision systems typically consist of an illumination system and video camera or set of cameras linked to computers which can automatically and non-destructively inspect, identify and guide without human intervention. A major contributor to the falling average value of a vision system of this 'general purpose' type is the 'Intelligent' or 'Smart' Camera, where all of the signal processing capabilities are housed within the camera itself. Vision is used in three key application areas: robotic and pick and place applications; product traceability inspection and measurement.

All these applications benefit from the speed and repeatability of measurements made by vision systems and the fact that they can be used in environments that would be unpleasant or dangerous for human operators.

Robotic and pick and place applications

The use of machine vision to guide robots for the precise positioning of components extends back to the 1980s when an inspection system was installed on automotive production lines for robotguided application of sealant to body seams and insertion of windscreens into the body shell. Picking and place methods are not restricted to assembly applications. One example is unloading gearbox housings from pallets where the robot arm needs to be guided by the vision system to locate into gearbox housings randomly oriented on a pallet in variable factory lighting conditions.

Product traceability

Tracking a component and all the processes it has gone through, from manufacturing, assembly right through to end-user requirements for spare parts replacement (from the cradle to the grave) is becoming an essential requirement as ERP, MRP and quality assurance systems become more widespread throughout the manufacturing supply chain. An increasingly popular method of product marking is the 2D Datamatrix code, a square array of dots or cells (Figure 2} which has a much higher data density than 1-D barcodes. Items undergoing several different processes during manufacture can have all the details encoded onto the part. The codes can be as small as 1mm square or less, allowing very small parts to be coded where it might be impossible to put a human readable code. Industrial vision systems are used to verify these 2-D datamatrix codes with the highest degree of accuracy and reliability and often at high line speeds. The vision system reads the code and puts the information directly to a database, eliminating manual transfer errors. 2D Datamatrix codes are extremely robust and contain a considerable amount of redundant information, which gives error correction capabilities. This means that even codes with more than 20% missing can still be read. This makes them ideally suited to rugged and dirty environments.

Inspection and measurement

Machine vision can make simple or complex repetitive measurements accurately, at speed and objectively, and is used in a host of on-line quality control applications. Vision systems, unlike their human counterparts, can work 24 hours a day, seven days a week. Inspection remains the biggest single application for vision, ranging from checking for defects on a production line, to being linked directly into the production process to provide statistical data from the measurements being made. The speed of vision systems means that 100% inspection of product is often possible, giving data from each and every component. This allows more or less random defects to be identified, as well as trends in the production process, leading to early detection of faults in the process before 'out of tolerance' items are actually produced. This reduces wastage, increases yield and ultimately cuts costs.

Getting free advice on vision

The UK Industrial Vision Association Limited (UKIVA) is a not-for-profit organisation whose prime objective is promoting the use of vision by manufacturing industry. Members include vision component suppliers, 'full system' suppliers, or system integrators, consultancy services and academic research groups. The UKIVA web site (www.ukiva.org) is an extremely useful source of vision information and the Association also offers free advice via phone (+44 1763 261419) or e-mail (info@ukiva.org) to anyone seeking help in specifying or sourcing vision systems or components.

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