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Method of scanning dark colored objects.

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

Method of scanning dark colored objects.

Postby INVENT3D » Tue Jan 21, 2014 2:49 am

Hi everyone,

I'll start of with a bit of background in what i'm trying to achieve.
I'm trying to scan various components of some general aviation aircraft, I intend to reverse engineer these components to create a home flight simulator so I can stay relatively current with using the equipment. I don't fly nearly as much as i'd like to be.

Below is a partially reverse engineered component. This was scanned with a NEXTENGINE HD laser scanner. Because these units are so costly I didn't risk treating the surface with any white powder etc. This resulted in broken and almost unusable scans, however I was still able to draw from it.

Image

I've been under the impression that a structured light scanner would provide better results. I've been lurking around the forums researching in an effort to build my own scanner. My time available to build and perfect my own scanner was limited so I ended up taking the plunge by purchasing the SLS-2 kit, which should arrive early to mid march.

Below is a picture of the next item I intend to scan, both fascias around the screens and the long thin bezel located in the middle. Again due to the cost of these items I can't treat the black surface.

Before the scanner arrives i'd like to ask how people have successfully or unsuccessfully scanned untreated, dark colored objects?

Image
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Re: Method of scanning dark colored objects.

Postby MayCrown » Tue Jan 21, 2014 6:43 am

There is a thing called cyclododecane spray.

You can read about and see the images in this post of Master Mattia below.

Check this out:
viewtopic.php?f=2&t=1283&p=12756&hilit=cyclododecane#p12756

Do more research before applying it tough, mattia applies it on a cheap cellphone only. I don't know if there occurs an after effect. Do it on your own risk. Without coating you will have to use a lot of hand work, that indeed you have the talent for, but time consuming. The time is important for human beings.

You don't have to use it all over, you can apply it on the key areas. It may be costly, but again not costly tha. Losing your valuable time.

Best regards,
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Re: Method of scanning dark colored objects.

Postby testae » Tue Jan 21, 2014 9:26 pm

Please correct me if I am wrong everybody, but these surfaces do not look too bad for scanning to me. They are indeed quite dark but they do not appear absolutely black and shiny on the photos. I would give it a try without any coating. Just play around with the settings a little bit and if you brighten up the whole thing enough (after calibration) you might be lucky and able to scan these surfaces. However to my experience you will run into a big problem with these glass displays. Not only will there be no chance to properly scan them without coating. They will also cause bad reflections that might affect all of your scans of the surrounding area, especially if the light is reflected right into the camera. So you might have to cover the displays (probably a sheet of paper cut into the right shape will do the job).
Good luck!
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Re: Method of scanning dark colored objects.

Postby MayCrown » Tue Jan 21, 2014 10:05 pm

I think the surfaces are quite bad for scanning without coating.
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Re: Method of scanning dark colored objects.

Postby INVENT3D » Tue Jan 21, 2014 10:42 pm

MayCrown wrote:There is a thing called cyclododecane spray.

You can read about and see the images in this post of Master Mattia below.

Check this out:
viewtopic.php?f=2&t=1283&p=12756&hilit=cyclododecane#p12756

That definitely looks promising, I still don't know if I would feel comfortable spraying it on $70k worth of avionics.
Simply adjusting the brightness and contrast between the camera and projector wont help a great deal MayCrown?

testae wrote:So you might have to cover the displays (probably a sheet of paper cut into the right shape will do the job).

The reflections from the screen were my first concern. I think i'll just cover it like you stated.
PC Win7 Ult x64 | i7 980x Stock Clock | 6GB DDR3 | 2x AMD5970's in Xfire
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LASER NEXTENGINE HD...
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Re: Method of scanning dark colored objects.

Postby MayCrown » Tue Jan 21, 2014 10:58 pm

Everytime someone posts a reply here, I magnify the picture and inspect it once more :D

INVENT3D wrote:That definitely looks promising, I still don't know if I would feel comfortable spraying it on $70k worth of avionics.
Simply adjusting the brightness and contrast between the camera and projector wont help a great deal MayCrown?


Yes it may help, but if there are those little many glitters on the black shiny plastics, it's one of the worst things.

1)Give it a try with the trial version of David, borrow a projector from a friend, find an HD webcam around (Logitech or Trust).
2) When your SLS Kit arrives, try without coating, if you can't ----> proceed to the next step
3)If available, first ask Mattia his opinion. He's the one who uses cyclododecane. ---> If you're satisfied with what he says, proceed to the next step.
4) Apply the cyclo to a less important electronic gadget, then inspect it after 2 or 3 days, open it and look inside, is there any damage to the circuits, oxidation, whatever.. If no proceed
5) You can try the cyclo on the main object.

I think.
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Re: Method of scanning dark colored objects.

Postby MagWeb » Tue Jan 21, 2014 11:22 pm

Not that easy.

Coating (means an equal reflecting surfaces) will improve its scanning results - no doubt.

I had to scan a nearly black model some time ago without touching it in any way:
Open the iris as much as possible (I removed it finally) - you'll lose depth of sharpnes.
Calibrate on a target not being black and white but on a printout being grey/black - while trying to keep the grey surface as white as possible for DAVID with the means of cam parameters and projector contrast - this needs some experiments.
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Re: Method of scanning dark colored objects.

Postby Christian_Mendez » Wed Jan 22, 2014 9:39 am

Good morning,

I agree with Gunter - coating is not always that simple.
I think it´s very irresponsible to use something if you do not have the knowledge and experience to ensure the object´s safety.

I work in a museum with art conservators and priceless artwork. I know from my colleagues that Cyclododecan is not always
harmless. I can recall a report on damage caused by cyclododecan. While it is said that it´s harmless and it will evaporate entirely
after a few days, one cannot know what reactions it may cause to different materials in the long tern. Our art conservators will
always avoid using it unless safe use has been confirmed by our laboratory.

So unless you know that it´s perfectly safe to use cyclododecan I would suggest to avoid using it. I don´t think it´s a good Idea.

Reducing the camera´s contrast and increasing the exposure time will definately help. My last scan was a burnt match. Coating the
match was not necessary at all.

regards,
christian
www.greyscale3di.com "if it ain´t movin´, we can scan it!"
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Re: Method of scanning dark colored objects.

Postby Sven » Wed Jan 22, 2014 11:16 am

I'm not sure what you mean by "contrast". Usually you should NOT use the "contrast" settings of the camera, set them to default. This may depend on the camera drivers.

With the SLS-1/SLS-2 hardware, there is no "contrast" setting. Do not use the one in the projector menu!

I would recommend this:
1. Set the Projector Brightness slider to maximum.
2. Set camera Exposure to 1/60s or 1/30s.
3. Place the dark object in front of the scanner, and set the camera lens aperture dial so that the red sine waves are correct on the dark object.
4. For calibration, the image is now much too bright because the calibration panels are white.
a) Use darker calibration panels (black markers on dark gray ground)
or
b) reduce "Projector Brightness" slider temporarily for calibration

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Re: Method of scanning dark colored objects.

Postby Christian_Mendez » Wed Jan 22, 2014 4:27 pm

My bad, :oops:

I over read the fact that a SL2 Kit is on the way. I thought a webcam is in use.

In this case I agree , adjusting the camera contrast setting is not possible and you´d have to stick to opening the aperture, increasing the exposure time and/or increasing the projector brightness.
But I disagree that one should not touch the contrast setting of a camera to widen the tone range of an image by decreasing the contrast. You´re right, Usually it´s not necessary to operate the camera outside the standard settings and you can just get around by increasing exposure times and projector brightness, but unusual situations occur from time to time and this has been a good and safe method for me to scan dark surfaces which I thought I´d share.
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Re: Method of scanning dark colored objects.

Postby INVENT3D » Thu Jan 23, 2014 1:50 am

Christian_Mendez wrote:My last scan was a burnt match. Coating the match was not necessary at all.

Thanks for sharing Christian, you got some amazing results. Did you happen to snap any photos during the scanning?

Sven wrote:I would recommend this:
1. Set the Projector Brightness slider to maximum.
2. Set camera Exposure to 1/60s or 1/30s.
3. Place the dark object in front of the scanner, and set the camera lens aperture dial so that the red sine waves are correct on the dark object.
4. For calibration, the image is now much too bright because the calibration panels are white.
a) Use darker calibration panels (black markers on dark gray ground)
or
b) reduce "Projector Brightness" slider temporarily for calibration

Thanks Sven, this is valuable information, this is going straight into my "How To" notes.

I'll apply these methods and post my results once the scanner arrives.

Cheers.
PC Win7 Ult x64 | i7 980x Stock Clock | 6GB DDR3 | 2x AMD5970's in Xfire
SLS SLS-2 Kit
LASER NEXTENGINE HD...
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Location: Australia

Re: Method of scanning dark colored objects.

Postby billyd » Sat Oct 01, 2016 6:49 pm

What if the projector projected the patterns in a bright color instead of black for scanning dark objects?
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