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Scanning VERY small objects

Problems, solutions and discussion about scanning with a video projector and stripe patterns.

Scanning VERY small objects

Postby formwurx » Mon Jun 20, 2016 2:08 pm

I'm doing a custom build for a client which requires me to scan very small components - some as small as 5 cubic mm. The scans from the SLS3 are very rough - the basic shape is there, but no detail. I find it a bit odd as it can pick this sort of detail out as part of a larger object no problem, so why is it so tricky when scanning such small objects on their own?
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Re: Scanning VERY small objects

Postby WalterMo » Mon Jun 20, 2016 6:52 pm

It is possible to do perfect micro scans with DAVID, look e.g. here:
viewtopic.php?f=15&t=4491&p=23046#p23046

But you have to modify some components of the DAVID kit:
1. The size of the calibration panels have to be adapted to the size of your object. That means you have to print new ones.
2. You have to attach a second convex lens in front of the projector's lens to be able to project a small high resolution image.
3. You have to put extension adapter rings between the camera and its lens to grab the small projection image from the object.
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Re: Scanning VERY small objects

Postby formwurx » Mon Jun 20, 2016 7:49 pm

Hi Walter

Thanks for that - I have been having a discussion on facebook with milz who has recomended a similar thing, I have oredered a lens ans downloaded a 3d print file to attach the lens to the projector.

So I just make my own grid to calibrate to and stick it to the glass plates, say with gaps between points at 1mm, 2mm or whatever?
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Re: Scanning VERY small objects

Postby formwurx » Mon Jun 20, 2016 7:54 pm

What sort of rings did you attach to your camera?
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Re: Scanning VERY small objects

Postby WalterMo » Mon Jun 20, 2016 8:37 pm

formwurx wrote:What sort of rings did you attach to your camera?

I don't have an original DAVID camera, only some modified web cams.
These rings could help you:
http://www.theimagingsource.com/product ... and-rings/
But these rings (tubes) cannot solve your camera / lens problem completely. It's possible to focus sharp on small close by objects but the main problem is that you need space (distance) between lens and object. The distance is necessary to have free space for the projector's beam from one side onto the object. Dr. Benoy has mentioned (in his first post of my link above) a 50mm focal length lens and a 20mm adapter tube. In so doing he got the necessary space.
Maybe a lens with less focal length than 50mm is sufficient. But sorry, I have never made such micro scans and therefore cannot give 100%-guarantee tips.
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