Thursday, May 26, 2011

When the part is in motion

Grabbing images of parts that are moving past the camera requires short exposure times and lots of light. And don’t even think of using a rolling shutter CMOS camera!

The issue is that when the exposure time is relatively long the part you’re looking at will be smeared across several pixels. The solution is therefore to keep the exposure time short enough that the part moves less than the distance imaged by one pixel. (You can do the math!)

An interesting example of this is covered in the May 2011 Assembly magazine. “Assembly In Action: Inspection System Ensures Quality Parts for Binder Assembly” describes a two camera system that measures cylindrical parts on a moving conveyor. There’s nothing particularly unusual about the system, other than that the software is Halcon, which strikes me as perhaps a little overkill (sledgehammer to crack a nut?) but it’s just a good, practical vision application.

The integrator was a Netherlands company by the name of Radine, and as there’s no link given in the article I thought I’d provide one here:

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