Monday, January 02, 2006
Simple 3D Scanner
Steve Baker has put an open-source design on the web for an easy-to-make 3D scanner. You can find details at: http://www.sjbaker.org/projects/scanner/.
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Cool! Now if I can just restrain myself from trying to build one and get some of the other things I've started finished.
Rather than using a lens, which would be difficult to obtain, even using ebay, could one achieve the same effect by scanning the laser dot in a line using a rapidly spinning mirror? I believe one of Baird's mechanical TV cameras used a system a bit like this, with the upshot that the performer had a faceful of intense, spinning light patterns all the time! Perhaps several camera frames could be averaged if the brightness decreased too much.
(3d_geek == Steve Baker)
I considered scanning vertically - but it was mechanically more complex than a lens and there are issues of the rapidly moving dot missing scanlines in the video image. Consider that the laser spot is moving vertically - and so is the camera's scanning action - it's pretty likely that the camera won't always be looking at the pixel where the laser happens to be - then you'll have missing data.
Cameras don't necessarily have 'persistance of vision' like human eyes do.
You could perhaps average several camera frames - but remember that the turntable is spinning inexorably so each frame grabbed would be a slightly different 'slice' of the model.
Having said that, I do already average 100 raw data points (in a 10x10 grid) from the raw scanner data in order to filter out noise that seems to result from the really crude way I search for the laser line in the image. More sophisticated image processing would probably improve precision immensely - but even with this heavy filtering, there are far more data points than I really needed.
I think the idea of using one of those 'laser level' tools (which is just a laser and a line generator lens) is the simplest thing. The only snag is that the really cheap ($10) one I bought locally - and the equally cheap one I borrowed from a neighbour both generated a fairly wide and fuzzy line - much worse than I got with a laser pointer and a holographic lens. HOWEVER, if you spent a bit more and got a more up-market one, you might find it to be better. However, I'm not about to go out and spend $20 to $60 to test a gizmo when I already have a very good solution!
Building the turntable (and the camera and laser mount) out of Lego means that I actually pull the whole contraption apart and rebuild it ever time I want to scan something, that way the size of the machine adapts to best fit the thing I'm scanning!
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I considered scanning vertically - but it was mechanically more complex than a lens and there are issues of the rapidly moving dot missing scanlines in the video image. Consider that the laser spot is moving vertically - and so is the camera's scanning action - it's pretty likely that the camera won't always be looking at the pixel where the laser happens to be - then you'll have missing data.
Cameras don't necessarily have 'persistance of vision' like human eyes do.
You could perhaps average several camera frames - but remember that the turntable is spinning inexorably so each frame grabbed would be a slightly different 'slice' of the model.
Having said that, I do already average 100 raw data points (in a 10x10 grid) from the raw scanner data in order to filter out noise that seems to result from the really crude way I search for the laser line in the image. More sophisticated image processing would probably improve precision immensely - but even with this heavy filtering, there are far more data points than I really needed.
I think the idea of using one of those 'laser level' tools (which is just a laser and a line generator lens) is the simplest thing. The only snag is that the really cheap ($10) one I bought locally - and the equally cheap one I borrowed from a neighbour both generated a fairly wide and fuzzy line - much worse than I got with a laser pointer and a holographic lens. HOWEVER, if you spent a bit more and got a more up-market one, you might find it to be better. However, I'm not about to go out and spend $20 to $60 to test a gizmo when I already have a very good solution!
Building the turntable (and the camera and laser mount) out of Lego means that I actually pull the whole contraption apart and rebuild it ever time I want to scan something, that way the size of the machine adapts to best fit the thing I'm scanning!
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