QMT Features: April 2012
Manufacturing vision
Technological innovation is driving the rapid growth of vision systems. Dr John Haddon takes a look new developments in vision systems for manufacturing.

With a growth of 35% in 2010 and an estimated growth of 20% in 2011, the European Machine Vision Industry is going from strength to strength even when many other sectors are under extreme economic pressure. The prime reasons behind this growth are a combination of improved capabilities and generally decreasing prices within the industry itself, together with an increased demand, fuelled in part by an increased move towards automation in manufacturing industry but also by an even greater emphasis on quality.

Industrial vision systems are used in a wide range of application areas, some of which include:
• Inspection, where they have a multitude of uses such as quality assessment, metrology, error/fault detection, sorting, process control, measurement to determine supplier payment levels etc
• Track and trace, where they are used to read codes, labels and marks to ensure the appropriate part, product etc is in the correct place, be it in the manufacturing process or final packaging process
• Robot vision, where they are used either to guide robots or where robots present components to the vision systems for inspection

In the automotive and aerospace manufacturing industries, vision has a key role to play. Efforts to reduce costs and minimise defects provide opportunities for both inspection and robot vision, while in the aerospace industry part traceability and identification is important. With hundreds of thousands of individual components produced by thousands of suppliers, there has been an increasing use of industrial vision systems for speed and elimination of human transcription errors. High speed imaging means that 100% inspection is a reality for many manufacturing environments, eliminating sampling inspections. In addition, the integration of vision systems into statistical process control systems can allow any changes in the manufacturing process to be identified and rectified before any out-of-tolerance product has been produced, thus minimizing waste.  Technology developments are fast paced in the vision industry and it is worth taking a look at some of the key developments in cameras, illumination, image processing software and image data transmission standards as well as the emergence of smart cameras, and one of the fastest growing technologies – 3D imaging.

Recent advances
Recent key camera developments have result in improved resolution, frame rate and size but there are also improvements in many other areas such as reduced noise, higher dynamic range, improved bit depth and real time changes to camera settings. These enhancements lead to more flexible units that better meet application requirements. Developments in CMOS and CCD image sensor technology means that cameras with multi megapixel resolution are now readily available in very compact housings that can be mounted almost anywhere.

There is generally a trade off between how fast the camera can run at a given resolution. The larger the image size, in general the slower the image sampling rate, so it is essential to get the correct balance between image size and inspection speed. For high speed, high resolution inspection on moving production lines, a high resolution linescan camera may be the solution, where an image is built up line by line as the object moves beneath the camera. High resolution cameras produce a lot of image data, which must be transferred to the processing computer (unless it is a smart camera, as discussed later).

The introduction of the GigE Vision data transmission standard in 2006 allowed image data to be transferred over distances up to 100 metres at speeds up to 1000 Mb/s using Cat5e or better Ethernet cabling and connectors, even allowing multiple cameras to be connected to multiple computers as part of a genuine network in a manufacturing environment. The data transmission rate offered by GigE Vision can be doubled using Link Aggregation technology. Link aggregation, or IEEE 802.3ad, is a networking technology that uses multiple Ethernet ports in parallel to increase the link speed beyond the limits of any one single port. Link aggregation cameras are connected by two cables to the host computer, which see it as one connection at twice the normal speed.  With developments in camera technology bringing ever increasing data volume, new data transmission standards have come along such as CoaXPress offering higher speeds over similar cable lengths using coaxial cable, and USB 3.0 offering high speeds over shorter cable lengths, with others such as CameraLink HS and Ten GigEVision well under development.

Software for highly sophisticated image processing and measurement provide extraordinary versatility for a wide range of measurements. Dedicated programs for 1D and 2D code reading, pattern matching and optical character recognition facilitate tracking and traceability. User interfaces have been simplified to make vision more accessible to non-vision specialists. Smart cameras feature on-board image processing meaning all processing and measurements are carried out in the camera itself and just a result signal transmitted to the control system. The latest smart cameras can be equipped with image processing capabilities previously only available on PC-controlled systems. Developments in LED technology have resulted in the availability of a wide choice of stable, high brightness illumination sources with a long service life at relatively low cost. In addition LEDs can be readily configured for different illumination angles, such as front or back lighting, on axis, diffuse lighting as well as bright field and dark field lighting. Lighting controllers allow LEDs to be strobed to increase light output, prolong lifetime and ‘freeze’ motion. Laser diode technology is a particularly important component of 3D imaging.

3D Imaging
One of the most exciting developments in recent years has been the emergence of real-time 3D production line inspection as an affordable option, thanks to components for industrial 3D imaging, including laser diode line sources, lenses, 3D image processing software and 3D cameras, increasing significantly in performance while decreasing in price. 3D matching tools have recently been introduced that enable 3D models to be compared to a known 3D or ‘golden’ template. Another interesting recent introduction has been a new range of 3D ‘smart’ cameras, which feature an integrated laser source and optics and provide on-board processing of 3D data, allowing the direct output of the measured results. 3D imaging for volumetric comparisons, volume measurements and bin picking of random parts is now a very real and growing part of the industrial vision market. According to a market study of the German automotive industry by the Fraunhofer Allianz-Vision in 2010, 3D measurement techniques (including contact methods) are used by 84.5% of the automotive supply industry.

Applications for enabling technology
These developments in vision capabilities create an enabling technology that can be used in a multitude of applications in the automotive and aerospace industries. Virtually any component, assemble or sub-assembly can be inspected using  fast, accurate vision systems and robot vision and 3D measurements have further enhanced the capabilities that vision has to offer. Just some of the possible applications include:

• Engine and Gearbox inspection, e.g sealing surfaces
• Measurement of the location of components and holes on components
• Positioning of glass (3D) before final push by a robot onto the glue
• Colour inspection
• Code reading (printed and embossed parts) to verify parts for assembly (2D codes and OCR)
• Checking and calibration of dashboard components e.g airbag components
• Picking, depalletisation and 3D bin picking
• Surface inspection, profiles, stamped parts
• Geometrical inspection, e.g piston valves
• Welding guidance
• Gap/flush measurement on car bodies

The list of applications can go on and on and many UKIVA members can offer expert advice about machine vision systems for the automotive and aerospace industries as well as supplying components and complete systems.
While this article has focused on the use of vision in the manufacturing process, there are many other uses of vision in the automotive industry. On vehicles themselves there may be cameras to help with reversing or to eliminate blind spots or cameras for automatic parking systems. There are also many ancillary uses of vision related to the automotive industry, such as automatic number plate recognition, congestion charging, tolling systems where there is lane priority on motorways at busy times for vehicles with more than one occupant and automatic road sign detection systems.

Author: Dr. John Haddon, Technical Consultant to UK Industrial Vision Association and Director, Panther Vision Ltd.
email: jf.haddon@panther-vision.co.uk  

Thanks are due to UKIVA members Alrad Imaging (www.alrad.co.uk), Baumer (www.baumer.com), Panther Vision (www.panther-vision.co.uk) Scorpion Vision (www.scorpionvision.co.uk) and STEMMER IMAGING (www.stemmer-imaging.co.uk) for contributions to this article.
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