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Explaining the benefits of 3D machine vision

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This article from Sick looks at the benefits that 3D machine vision offers over 2D - but it also emphasises that 2D vision still has its place.

We take our stereoscopic vision capability for granted but, as with all things, it is only when you lose this ability that you realise just how useful it was. We must also consider those who have been given their sight back - imagine the revelation of being able to see clearly in 3D again! The industrial world can experience similar levels of enlightenment by considering the benefits available through the use of 3D vision instead of the more traditional 2D alternative.

The appreciation of depth or height is something not lost in the engineering, manufacturing and process industries, as well as logistics. What is not appreciated is that 3D vision technology exists to turn this appreciation into cost savings and improved quality.

There are many companies still rooted in a 2D world - not realising the potential that another dimension can give them. David Hannaby, a vision systems specialist at Sick (UK) Ltd, explains: "The excuse 'we have always used 2D' is no longer relevant, as parts become more complex, customers become more demanding, and machine technology accelerates at an incredible rate.

"There are so many benefits to be had from 3D vision systems, and it is only by experiencing these that users can get a real appreciation of what they have been missing."

Improving quality, saving cost

In general, all vision systems can save money by improving product quality and production yield, reducing - and even eliminating - the cost of manual inspection and removing the need for complex sensor arrangements.

Hannaby adds: "All vision systems are designed to measure, locate, inspect and identify, but 3D vision systems offer a new dimension not considered by many companies. In many cases it enables a company to carry out an inspection or location task not previously thought feasible. In others it actually makes the process easier because you do not need complex lighting."

Whereas 2D vision relies on contrast to differentiate between features or to spot anomalies, 3D vision systems use height measurements to find out far more about an object. Hannaby says: "A case in point, where 3D really shows its capabilities, is if you were to look straight down into a multi-pin computer connector. A 2D image could tell you if all the pins were present and in the correct position, but a 3D image would also tell you if the pins were all the same length, which is an important measurement not available in the 2D world.

"Metrology is another area where 3D vision systems are setting new benchmarks. 2D systems can identify a number of features such as length, width, area, X and Y location and rotation angle, but 3D will offer all these feature plus height, volume, Z location, and roll, pitch and yaw angles. Indeed, as soon as we see part variation in the Z direction, 3D comes into its own.

"Another area where 3D will see a big growth is robot pick-and-place where a 3D system not only sends the positional co-ordinates of an object to a robot but also its height, allowing a robot to go to the correct depth to pick up a component or product."

Simple set-up

"It is also important to let people know that a new dimension in vision does not necessarily mean a new dimension in complexity. There is certainly an option to go for systems that offer a multitude of configurations for more flexible manufacturing operations, but there are also many continuous-production applications that just need an initial set-up and then the camera is left to 'do its thing.'

"Sick is able to offer both styles - it just depends on the application as to which one is most suitable. In both cases, with what Sick can supply, they come with advanced software that makes the actual configuration routines much simpler than people think."

2D still has its place and will always be a very important tool, used by companies to ensure quality and save money. For example, it is not possible to use a 3D system to inspect date and lot codes printed on food or pharmaceutical products, as there is no measurable height change to detect. Indeed there are many applications where 3D will not work at all because the image processing relies on height changes in a product to be able to detect a feature or defect. However, there exists an equal number where 3D vision systems offer advantages not yet exploited by companies simply because they are unaware of the huge benefits offered by this technology. It may be that a combination of both 2D and 3D technology is the best option in some cases.

 
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