Thursday, June 17, 2010

Alternatives to machine vision

While my main interest is in using machine vision to help achieve business goals, it’s worth noting that it isn’t the best tool in every situation. Take crack detection for example.

It can be very difficult to find a crack in an image: lighting is hard enough, but the biggest problem, in my experience, is that while a crack might be quite long it has almost no width. This means it may be less than a pixel wide, which means it can’t be detected reliably.

When you’re looking for cracks in metal parts you’re often better off using eddy current. It can be slow and does need relative motion between part and sensor, but on the other hand, it’s a well-proven technology.

There was an informative eddy current application story published on the Quality Digest web site back on June 8th, “Crack Testing of Hypodermic Needles.” Could machine vision have done the job? Perhaps, but I’m pretty sure the error rate would have been much higher than with eddy current.

Just be aware, we might love machine vision but that doesn’t make it right for every problem.

And finally, an apology to those who clicked the link I provided yesterday to "hottestdigitalcameras" blog. Apparently the blog has been suspended so the link no longer takes you to the article. Sorry about that. Perhaps I should concentrate on providing more original material and fewer links. What do you think?

1 comment:

azmscan said...

I have experience with eddy current sensing and agree that for specific materials it is a much better technology. That being said, machine vision has an advantage over almost every other type of testing: results are inherently 'visible'. With eddy current for example, it requires a trained specialist to interpret results and this is often the case for almost every other technology (like X-ray and ultrasonics). This is also why Machine Vision companies should continue to make certain that results can be viewed easily.