Author Topic: More Lasers = A Better Scan  (Read 8450 times)

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Offline gumbyrulesyou

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More Lasers = A Better Scan
« on: September 16, 2008, 03:42:22 PM »
Hello -

So I've yet to hook up the laser scanner just yet, but I have some thoughts and past experience I'd like to share.

Once upon a time I built my own laser scanner. It was awesome, and it used two laser beams.. Well, actually one laser, split in to two beams and then broken out in to lines.  The lines came in from either side of the camera and intersected at zero. Here's why - Any sloping surface greater than whatever the laser angle is will effectively mean an undercut that can't get scanned. This was bad for what I was doing. I didn't need dimensional accuracy as much as I needed an accurate visual representation.  Anyway, I didn't use an XYZ gantry, I used a turntable. It was just better for what I was doing, and anyway, I had one on hand. Here's some pictures. Sorry for the high resolution.

Here's the rig in the flesh.

I had a little layout breadboard table I made out of ply. Good for this sort of thing. All the optics were affixed to the various stands. The laser was a big fat 50mW 650nm red - Plenty of power to go through all those lenses and still be seen by the camera. I photoshopped the beam a little bit to make it show up in the foreground.

Here's an animated GIF of the single line version. gotta start somewhere!

and here's the resulting point cloud, complete with noise.

After some processing in crappy VB programs written a long time ago by me, you get this.

next up shots of the second scan.  I ended up taking the brightness of the laser and assigning it to the brightness of the point (in the cloud) This kind of let me weight them visually - After all, I was just drawing these on sheets of styrofoam to cut with a jig saw.  You can see on the left that there are purple and yellow points. these represented either laser. Both lines were scanned at the same time. Processing was done from center to left for one laser, and center to right for the other laser. This was NOT two scans, as in scan once, set up again, scan again, overlay.

This one is big - Scroll sideways. Sorry - Screen capturing from dual monitors makes messes like this.

For another part of the scan (for the sole of this shoe) you can really see where two lasers comes in handy. Blue and green represent left and right laser beams.

Now you guys can pick apart my lack of signal processing, inattention to detail, mathematical flaws, geometric laws bent and broken, but the results were pretty spectacular. After all, I was only going to render the scans by sharpie and jigsaw, so why blow weeks on software when I had foam to turn to dust?

Anyway, a little food for thought for producing the next generation of video scanner plug in software.

Also, a question - Can the plugin scan multiple strips and knit them in to one cloud? Solidworks 08 seems to be able to make sense of the mechanical probe-generated point clouds fairly well, and I've got an enormous machine, and it would be good to be able to scan big things.


Offline TomHubin

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Re: More Lasers = A Better Scan
« Reply #1 on: September 20, 2008, 03:44:34 PM »
Hello Andy,

No criticism here. The word stunning comes to mind.

I saw your post when it first appeared. I have dialup internet and I guess I got impatient because I don't recall seeing the giant boot at that time. The whole project, from scan to sculpture, is very impressive.

Did you write your own data capture and animation software? If so, please tell more about that. If not, please tell what software.

Were you able to scan the boot with the same setup that you scanned the shoe?

How did you build the giant boot?

How did you embed images in your posting? I would like to get past the 4 attachment limit.

Please post more.

Tom Hubin

Offline cwiliam

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Re: More Lasers = A Better Scan
« Reply #2 on: October 10, 2008, 09:32:43 PM »
Outstanding  gumbyrulesyou 
Im also interested in the software   will you let us try it Please

Offline gumbyrulesyou

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Re: More Lasers = A Better Scan
« Reply #3 on: October 19, 2008, 11:09:57 PM »
Sure I can give you the software - Or at least the source code. It was all done in VB6.

The problem is, it's probably going to be useless for any other purpose besides scanning boots. It was super purpose-built - There's no video interface, no VFW support, nuthin. I ended up frame capturing something like 2000 frames of video and writing them up to sequentially numbered BMP files. The file name, numbers, and location on the disk were all hard coded in to the software, AND I built all the screens to run on a dual monitor setup. Also, it was several programs. All one did was look at the images and do the remedial signal processing on it... It was horribly slow an inefficient, so much so that I actually broke up the data in to two sets and ran the program in two instances so I could utilize both CPUs. It still took all day, but again, it only had to work once. It would have taken me 3 days to write the software better.

Actually... I think I might have trouble finding the source code. Here are the executables. There's something else that goes with it - The data file of the boot. I'll see if I can dig it up. It's on a CD somewhere I know.  I don't remember the format - at all, and there's no documentation. If I can find it, I'll upload it, AND now that I think of it, I don't think that there's much in the way of source code left either. Who knows.... again I'll upload it if I find it, but its mostly useless, I hate to say.