Sunday, June 2, 2013

Application critique

Including technical details in an application press release lets us all improve our knowledge and advances the machine vision industry. Dalsa,, and end-user Accuma are to be commended for doing just that with “From Pole To Pole” published April 12th 2013.

This describes an assembly verification task performed at Accuma where cylindrical posts are measured to ensure the assembly is correct. The solution consisted of a backlight and a Dalsa Boa smart camera.

Two particular issues are described: the need to locate the post in the image, and the importance of ease-of-use and supportability. The first seems to have been addressed by using some sort of fixturing tool to locate the part in the image. (I know that’s obvious to you grizzled vision Pros but it’s not obvious if you’ve never done it before.)

The second issue was addressed by the choice of the Boa camera itself. I have no personal experience but the quote from the Maintenance Supervisor, “"We learned how to program the vision system using the manual that came with the product and we haven't needed any training,"” I found pretty telling. I found the same when I used the latest Keyence vision sensors. (“Easy setup, thanks to Keyence” May 1st, 2013.)

I would however make a couple of observations on the details of the application.

We’re told an 8mm lens was used. That’s a wide angle of view, so the true diameter of the post isn’t really seen. I would try to go with a longer focal length lens with a narrower viewing angle. Also, given that there’s measurement going on, I would (a) be concerned about the consistency of the working distance from post to lens (if it varies the scale changes,) and (b) want to see some kind of calibration target and process form part of the inspection.

But also, and to show that I can praise as well as criticize, I note that the backlight is some distance away from the post being measured. That’s a good thing because it reduces reflections off the cylindrical post and has the effect of making the lighting “pseudo-collimated”. (Further away would be even better.) Any time you’re backlighting, try to do the same.

So, a good article about a good application, and I’m sure there’s something we can all learn.

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