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Logitech Pro 9000: Don't use 640*480!

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Logitech Pro 9000: Don't use 640*480!

Postby Sven » Mon Sep 20, 2010 11:52 am

Hello,
We have often had problems with horizontal stripes/waves in scans made with webcams. These waves appear when the laser is moved too quickly (because of the rolling shutter in CMOS chips), but since some time we have experienced this problem also with very slow motions.
(This is not about Scanning Without Background!)

So I have made a comparison of different resolutions that the Logitech Pro 9000 offers. I used a motorized laser so I could always reproduce the same motion:
9000_resolution_comparison.png
5 scans of the same object (shuttlecock) made with different camera resolutions.

The scans are not smoothed. Please look at the tops of the shuttlecocks. As you can see, the resolutions 640*480 and 960*720 create wave artifacts. The resolutions 800*600 and 1600*1200 don't. (1600*1200 is the native chip resolution, and 800*600 is exactly half, while the other resolution require an "uneven" scale factor. Maybe that's why.)
EDIT: The direction of the waves is horizontal in the camera image, independent of the laser line direction!

So I recommend not to use 640*480. Instead use 800*600 or if you can move the laser really slowly, use 1600*1200 for highest resolution.

Please let me know if you make different experiences concerning this, or if you can confirm the same issue with other camera models.

Thanks
Sven
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Re: Logitech Pro 9000: Don't use 640*480!

Postby Khalid Khattak » Mon Sep 20, 2010 12:02 pm

Sven,
Nice and timely comparision :D
I have observed the vertical strips at 960 x 720 and i could not understand what was the problem but now its clear to me..
I recently did scan with 800 x 600 resolution and it work fine to me:)... 1600 x 1200 resolution in never tested....
PC: Dell Inspiron i3, 2.27GHz,4GB RAM,64 bit windows 7
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3D LED Mini Projector 250lumens, Native 1024x600
[b]http://free3dscans.blogspot.com/
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Re: Logitech Pro 9000: Don't use 640*480!

Postby Bongobat » Tue Sep 21, 2010 1:29 am

Hi,

Here I have done some similar tests with an unmodified Microsoft HD-5000. I used a motorized laser at a pretty quick speed for all the tests but the last one which is 4 times slower. You can see that for this camera the speed and framerate seem to have a lot to do with the horizontal stripes so I think this has to do with the rolling shutter here,but there is a strange vertical stripe pattern that happens at 640 X 480. I do not see any of these problems with the SPC900NC but of course It does not have these higher resolutions.
Attachments
HD-5000 Resolutions1.jpg
HD-5000 resolution patterns
HD-5000 Resolutions2.jpg
HD-5000 resolution patterns
DealExtreme red line laser, Microsoft Lifecam HD-5000
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Re: Logitech Pro 9000: Don't use 640*480!

Postby hunkatibor2 » Tue Sep 21, 2010 3:37 pm

Image
Hi Sven
I was a competitor in badminton until 18 year soots. The examination a competition ball with real feathers . The 640*480 the striped occurs in a resolution at me .
Tibor
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Re: Logitech Pro 9000: Don't use 640*480!

Postby Khalid Khattak » Wed Sep 22, 2010 3:49 pm

Amazingly at 960x720, 15 fps, 24 bit (RGB24), I have got both Repetition and Reference scans without any Horizontal and vertical lines...
The Scale is 150mm, paper is perfectly pasted with Gum stick...Corner is perfect 90 degree ...
Attachments
rep and ref.jpg
PC: Dell Inspiron i3, 2.27GHz,4GB RAM,64 bit windows 7
CAMERA:
David CCD Mono USB
LASER:
David 5mW Green line laser
PROJECTOR:
3D LED Mini Projector 250lumens, Native 1024x600
[b]http://free3dscans.blogspot.com/
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Re: Logitech Pro 9000: Don't use 640*480!

Postby Borg » Tue Jan 04, 2011 3:54 am

Happy New Year!
I have been experimenting with David for the past 6 months and I keep getting the same horizontal stripes/waves that we are talking about on this post. The difference is that I am getting them on all resolution settings. At first I thought it was something I was doing wrong, but after seeing this post I am not sure. I would appreciate any advice I could get.

I do the calibration with the lights on and the scanning in complete darkness. I have a sharp line and my laser is controlled by a motor. I have the motor geared down to the point that it takes 10 minutes for the laser to do 1/2 revolution.

Below is a scan of a split shake shingle for a house roof.

This was 800X600
800X600.jpg


This was 1280X800
1280X800.jpg


And my settings
Attachments
Properties 2.jpg
Last edited by Borg on Tue Jan 04, 2011 4:18 am, edited 1 time in total.
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Re: Logitech Pro 9000: Don't use 640*480!

Postby Borg » Tue Jan 04, 2011 4:01 am

The Advance settings are:
Properties 1.jpg


Picils.jpg


Thank you,
Steve
PC: ThinkPad Lenovo X200 Tablet, Intel Core 2 Duo CPU 1.86GHz,
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LASERS: David 5mW focusable Green line laser
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Re: Logitech Pro 9000: Don't use 640*480!

Postby WalterMo » Tue Jan 04, 2011 8:31 pm

Hi Steve,
Strange, even at 800 x 600 pixels. I don't know a panacea, perhaps someone else?

So my suggestion is, play about the camera settings. But in general: Adjust Saturation to 0, means no colour. Increase Brightness and change Exposure and Gain.

What kind of motor/gear have you used?

Walter
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Re: Logitech Pro 9000: Don't use 640*480!

Postby Borg » Wed Jan 05, 2011 8:38 pm

Hi Walter,

Currently I am using a 12 v. windshield wiper motor out of a General Motors truck and some small spur gears I had laying around. It is quite an ugly contraption. I wanted to make sure I could get the bugs worked out of everything else before I spent the time to put together a stepper motor to control the laser. (Electronics is not my strong side)

I took your advice of playing with the adjustments for the camera and have had mixed but improved results. Thank you for the advice of where to start on the controls. I will report back when I have been able to get consistent results.

Thank you again,
-Steve
PC: ThinkPad Lenovo X200 Tablet, Intel Core 2 Duo CPU 1.86GHz,
3GB of RAM, 32 bit Windows Vista Ultimate
CAMERA: Logitech Pro 9000
LASERS: David 5mW focusable Green line laser
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Re: Logitech Pro 9000: Don't use 640*480!

Postby orthofoo » Wed Jan 26, 2011 9:20 pm

Hey my name is Christos and I amke a project in biomechanics. i would be most grateful if someone could help me by answering me if i can use the DAVID system for capturing 3D dimensions of the human foot? Any help?Thanks in advance
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Re: Logitech Pro 9000: Don't use 640*480!

Postby WalterMo » Thu Jan 27, 2011 2:05 pm

Hello Christos,
Yes it is possible to scan human feet. Do you intend to scan it if the foot is „free“ or „loaded“? Latter is possible if you scan from below through a stable glass plate.
What is exactly your application?

Walter
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Re: Logitech Pro 9000: Don't use 640*480!

Postby novendhi.reiner » Tue Jun 04, 2013 1:35 pm

Hello all,

Sven said that we should use either 800x600, 15fps or 1600x1200, 5fps, and as long as i used DAVID, i always use 1600x1200, 5 fps. what are the basic difference if i select another resolution like 1280x1024, 5 fps or another option?
Is it true that the bigger resolution make the scanning more accurate and precise?

Thanks

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Re: Logitech Pro 9000: Don't use 640*480!

Postby WalterMo » Tue Jun 04, 2013 3:23 pm

The photo sensor of the Pro9000 has a (maximal) resolution of 1600 x 1200 pixels.
800 x 600 is just the half, more exactly if we look on the area, 1/4. So no mathematical interpolation must be made. It's an integer ratio. And that's good for DAVID.

Yes, a higher resolution will capture more details. But often 800 x 600 is sufficient. Also the frame rate is much higher. And if you have a complex object for which you need a high number of single scans it could happen that the RAM of your pc will overflow if you scan with a very high resolution.
Remedy: DAVID's 64bit version and a lot of memory:
viewtopic.php?f=16&t=5548

Walter
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Re: Logitech Pro 9000: Don't use 640*480!

Postby novendhi.reiner » Tue Jun 04, 2013 8:27 pm

Thanks Walter for your reply, but i have another question,

The photo sensor of the Pro9000 has a (maximal) resolution of 1600 x 1200 pixels.
800 x 600 is just the half, more exactly if we look on the area, 1/4. So no mathematical interpolation must be made. It's an integer ratio. And that's good for DAVID.

What do you mean by 1/4 area? Still don't understand about it. Is it, that DAVID works based on 4:3 aspect ratio? and if i choose another ratio, that the quality of picture that the camera took would be interpolated from 4:3 ratio?

Yes, a higher resolution will capture more details. But often 800 x 600 is sufficient. Also the frame rate is much higher. And if you have a complex object for which you need a high number of single scans it could happen that the RAM of your pc will overflow if you scan with a very high resolution.


I see. But for me, hardware is not a problem. I already prepared for this. And i looking for the detail and accuracy of scanning, also have DAVID 3.7.1 upgraded in my DAVID's USB. I hope it would minimizing the problem i guess. And i was wondering, are the amount of fps would affect scanning quality?

Thanks
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Re: Logitech Pro 9000: Don't use 640*480!

Postby WalterMo » Wed Jun 05, 2013 7:42 am

DAVID is not limited to cameras with a 4:3 sensor like the Pro9000. Other newer formats like 16:9 or 3:2 will also work. And DAVID also does not cut other formats than 4:3 to a 4:3 aspect ratio. But if the cam has 4:3, and we spoke of the Pro9000, then it's better to "scale it down" by an integer ratio. E.g. to 800 x 600. Please read Sven's post at the begin of this thread.
DAVID does not interpolate the camera format, this is done by the camera software.

Regarding the 'area':
The pixels of the camera's sensor are placed in two dimensions, x and y. X = 1600 and y = 1200. So its product is 1,920,000 pixels. (1.92 mega pixels).
For 800 x 600 we have the product of 480,000 pixels. This is 1/4 of 1.92 mega pixels.

The number of the fps doesn't affect the scanning quality. A high value is only of advantage if we scan "living" objects.
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