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I need help with panel-less setup

Questions, problems, comments and tips regarding the 3d scanning process.

I need help with panel-less setup

Postby dennik » Thu Apr 04, 2013 12:03 am

Hi everyone.

I bought one of the david laserscanner kits and I want to move into panel-less automated scanning setup cause I have a lot of things to scan, and I'm trying to make things easier for me.
I have an old servo as well as an arduino so what I'm looking for right now is a basic automated tilt setup that I can do, if possible with the hardware I've got.
The thing I noticed with the servo is that it has a minimum stepping of 1 degree which probably won't do if the scanning pass needs to be smoother. Any way to smoothly slow down a servo externally or electronically?
If anyone can point me to the right direction on how to set this whole thing up, I'd much appreciate it.

Thanks
dennik
 
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Re: I need help with panel-less setup

Postby WalterMo » Thu Apr 04, 2013 7:07 am

A „normal“ servo which is often used in model boats or aeroplanes is easy to control by an Arduino but its resolution is much too coarse for laser scanning.

So my advice: Tilt your laser by a stepping motor which has an attached gear. Gear ratio about 50:1......100:1. Like this one:
http://www.phidgets.com/products.php?ca ... _id=3319_1

Here you can find the controller and the Arduino code. It's well suited for plane-less scanning:
viewtopic.php?f=6&t=2421

Walter
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Re: I need help with panel-less setup

Postby dennik » Sat Apr 06, 2013 2:49 pm

Hey Walter. Thanks again for the help.
I will look into that setup, although it would be more advanced than anything I've done with electronics so far!
dennik
 
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Re: I need help with panel-less setup

Postby WalterMo » Sat Apr 06, 2013 5:42 pm

An alternative is to use structured light for scanning.
It's not more expensive. The camera can be the same and a used projector can be bought at an eBay auction. Often people offer their low light power device because they are frustrated due to its low brightness when they are looking a movie. For SL it's mainly sufficient. 200 lumens is a good value up to 1m (or more).
And, SL is much faster!!!!
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Re: I need help with panel-less setup

Postby dennik » Mon Apr 15, 2013 12:31 pm

The only thing I was wondering about SL scanning is how accurate it is for little sub mm details. I would be picky about that.
If Laser scanning is more detailed in small scale, I'd rather stick with that. Would you say there is a difference for small scale details?
dennik
 
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Re: I need help with panel-less setup

Postby VDX » Mon Apr 15, 2013 12:41 pm

... with reducing lens you can go as small as you want - I've reduced the output of a Casio-DLP-beamer to a sharp image of maybe 40x30mm and can go even smaller, if needed :wink:

The laserline setup in my dental-scanner has a minimal accuracy/resoultion of maybe 20 microns - with a SL setup with comparable dimensions I'll receive something around 5 microns accuracy

With smaller dimensions you'll get problems to focus the laserline finer than 30 microns, but with the 16microns(?) wide DMD-micromirrors I'll estimate pixel dimensions in the beamed (reduced) image of around 3 microns best ... and could be even better/smaller with special opics :mrgreen:

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Re: I need help with panel-less setup

Postby WalterMo » Mon Apr 15, 2013 5:25 pm

The resolution of laser scanning isn't higher as of SL.

If you go through the User Gallery you find e.g. this site:
viewtopic.php?f=15&t=4491&p=23046#p23046

And here you can see the direct comparison of coin scans, made by laser and later on by SL:
viewtopic.php?p=23790#p23790
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