Sunday, May 29, 2005


Turntable Scanner

I thought I'd better document an idea that I saw in O'Reily's "Make" blog while looking at postings about RepRap - I'm unable to find the original link. The concept was to use a rotating turntable and a moving laser pointer in conjunction with a video camera and some clever software to scan in and digitise an object.

Well, the Meccano turntable would both rotate and lower the object simultaneously so a static laser pointer could be used. As the method was already proved, it would appear that RepRap + laser pointer + video camera = 3D scanner.

Unfortunately I'm a bit busy making the fabricating side of things, but if anyone wishes to make a turntable-based scanner do let me know how you get on!

Vik :v)

Is this the one? DIY 3-D Scanner
No, not that one. This moved a laser pointer dot rather than spreading the laser into a line.

But whatever works is good!

Vik :v)
For Vik's clever software see
Roberto Cipolla's work at Cambridge:

I've been building one of these - instead of using a turntable, I build a big circular Lego railroad track and mounted the camcorder and laser onto a motorized cart!

The problem is to get a clean vertical laser line. The article Make's blog referenced talked about using the stem of a wineglass as a cylindrical lens. We tried a bunch of different glasses from our kitchen and none really worked well.

I tried one of those laser levels you see in DIY stores - it does a passable job but the line is too short to scan objects of a reasonable size.

I also found a laser pointer with a bunch of interchangable lenses that would generate stars, circles, dollar signs, etc. One of the lenses was a straight line - but the cheap holographic lenses they use didn't generate a clean, sharp line.

Finally, I bought a proper optical quality fresnel lens that's designed specifically for the task of making laser lines. It seems to work really well - I found a pair of them on eBay. I also ordered a set of mixed lensed from Meridith ($25) which claims to contain a cylindrical lens that's appropriate for spreading laser spots into lines.

Now I'm tweaking the software and generally making adjustments to get the best results and tweaking the camera mount to use the full resolution of the picture to image the laser line at the full range of possible positions.

Fun, fun, fun!
The Meradith lens set does indeed come with a cylindrical lens - but it has a really small 'spread' - not much better than the lens that you find on laser levels.
I've started to put together a detailed HOW-TO for my variation on the 3D scanner theme:

It still needs some polishing - plus some pictures of the final results - but I though you guys might like a heads-up.
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