I love reading application stories: I’m always fascinated to learn how people have solved the problems presented by a specific machine vision task.
One of the problems that I’ve encountered a few times is how to acquire images of long thin parts. If you fit the whole thing in a single field of view you loose resolution and waste a whole bunch of pixels. Line scan seems the obvious way around, but it does require that the part be moved in its lengthwise direction and sometimes that’s just not possible.
PPT has a way around this. They offer an image stitching tool which is ideal for assembling high resolution images of, say, needles. Why do I pick on needles? Well that’s the product covered in “Machine Vision Protects Pharmaceutical Packaging” (Control Engineering, February 2010.)
The actual needle inspection example is on the PPT web site, so you could read the details there too, but stick with the Control Engineering article because there are some other interesting details of pharma applications. One point I didn’t see, which is perhaps the most important reason for using vision in pharmaceutical environments, is that cameras are 100% attentive for 100% of the time. When you cannot afford to ship a single defective item, technology trumps human eyes every time.
Subscribe to:
Post Comments (Atom)
Posts
3 comments:
Aren't the images still acquired by moving camera, no big difference compared to line scan?
I'd like to hear from someone at PPT regarding the comment above, but here's my take: line scan needs accurate motion tracking, for example, by encoder on the belt. This approach avoids the need to do that.
Depends on what you are looking to inspect along that axis of motion. Image stitching is a cool feature, but if you are snapping in multiple images you could just analyze each picture on it's own. Using your needle example, you might simply be inspecting the shaft for dents or defects and then when you detect the tip you inspect that for sharpness and orientation. Another approach you might use is a lens splitter placing the left half of the part in the top portion of the image and the right half in the bottom. Alternatively you can skip the middle "Don't Care about" area and focus on what you do care about. In the past I have used this approach to inspect the tip of a syringe and then the base of a syringe ignoring everything in between.
Post a Comment