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Calibration Panel - left and right inner point

The place for questions, problems, comments and tips regarding the camera calibration.

Re: Calibration Panel - left and right inner point

Postby BoneIndustries » Fri Aug 01, 2014 10:32 pm

Calibration with same settings
2014-08-01_17-24-39.png

Resulting scan
2014-08-01_17-27-15.png

Compared to perfect panel
2014-08-01_17-31-09.png


What are the wrinkles in the corner caused by and how can I fix that?
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Re: Calibration Panel - left and right inner point

Postby BoneIndustries » Fri Aug 01, 2014 10:41 pm

You can see that the scan is bent away from the perfect panel.
2014-08-01_17-39-15.png
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Re: Calibration Panel - left and right inner point

Postby hal » Sun Aug 03, 2014 10:20 am

Hello,
the wrinkes cames from light reflection between panels, in the corner area. You can solve using a piece of black cardboard. A 2 or 3 cm large stripe that runs for all the corner edge's lenght. This will avoid that the projector light on right panels is reflected by the left one and viceversa.

Let us know if you solved this.
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Re: Calibration Panel - left and right inner point

Postby MagWeb » Sun Aug 03, 2014 2:31 pm

...or use a "negative" outer corner - DAVID will detect this automatically.
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Re: Calibration Panel - left and right inner point

Postby BoneIndustries » Mon Aug 04, 2014 9:33 pm

I will give both those ideas a try later.
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Re: Calibration Panel - left and right inner point

Postby micr0 » Tue Aug 05, 2014 5:44 pm

This topis is fortuitous. I too am scaling up a set of calibration panels to try to do some larger objects. I scaled the eps version in illustrator but the circles are no not round. They display round but they aren't plotting round. And scaling in illustrator is not an exact science. I was hoping someone could publish a mathematical description of the layout of the calibration points so that I could draw them in CAD accurately at any size. The panels I just made are 24" x 36" (609.6mm X 914.4mm). These will do as I'm still setting up my system and my copy of the David USB hasn't arrived yet for the VAR so I'm still just learning the system. If someone could give me the dimensional relationships and the critical features I'd be happy to post the CAD files here when I'm done.

Thanks.

µ
Attachments
cal1.jpg
µ
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Re: Calibration Panel - left and right inner point

Postby MagWeb » Tue Aug 05, 2014 7:00 pm

The pattern is pretty simple:

The centers of the markers have the same distance in horizontal as in vertical (four times this distance = Scale). The vertical column towards the corner's edge is half of this distance.
The precise size of the markers isn't that important. Keep an almost ratio of distance/radius as in the ready made printouts.
Left and right patterns are the same (one is rotated 180 degree towards the other)
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Re: Calibration Panel - left and right inner point

Postby micr0 » Thu Aug 07, 2014 3:28 pm

Unfortunately I have yet to find a parametric 2D Cad program (I really want one!) so I made this layout in Solidworks with parametric relation in the original sketch. In the model there is only one driving dimension and that is "Scale". Change the scale and everything should update proportionally including the dot size. I've attached the SW file as well as a .dwg and Illustrator file that are scaled to 24in. If anyone doesn't have SW and wants a different scale I can quickly create one and post it in any common CAD format. There are 2 pages to each file. One shaded and One outline. I will use the outline page in this file to cut the calibration points out on a 24" wide vinyl cutter out of mate black sign vinyl, then apply them to white acrylic panels. the other page is included for people that may have a large format plotter.

µ

EDIT:
it seems I can't attache these files here (not allowed) If someone with permission to do this can help I'll email them to you.

In the meantime hears a pdf of the 24" panel
Attachments
David 3D Laserscanner Calibration Panel Right V2.PDF
(89.16 KiB) Downloaded 222 times
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Re: Calibration Panel - left and right inner point

Postby MagWeb » Thu Aug 07, 2014 7:22 pm

micr0 wrote:it seems I can't attache these files here (not allowed) If someone with permission to do this can help I'll email them to you.


Should work zipping the files...
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Re: Calibration Panel - left and right inner point

Postby micr0 » Tue Aug 12, 2014 3:02 am

Ok. this .zip contains the SW2014 file and a .dwg. the sloidworks fie is parametric.
Attachments
David 3D.zip
(131.6 KiB) Downloaded 196 times
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Re: Calibration Panel - left and right inner point

Postby Vito » Fri Jan 08, 2016 12:15 pm

Hello,
I have been using the SLS2 for the last year and I am having some problems with bowing as well. There has always been a little bit, and in some cases it drove me crazy, but things got worse recently. In the past, I dropped my calibration pane, and I reattached the two parts at the best of my common sense. Now I have doubts that my offset or whatever David is supposed to correct is wrong.
I tried to verify my panel, but I cannot find anywhere the button to toggle the visibility of the virtual panel in David 4.4. It would be the first step to verify whether there is something wrong with my panel, or I suddenly un-learned how to calibrate...

Also, could someone give me the specifics of how the calibration panel is supposed to align?

(ps: the site tells me that the screenshots acquired from DAVID are the wrong size for attachment :lol: )

(pss, yes, I am scanning dead people)
Attachments
2016-01-08_11-55-51.png
Recent scan, with a lot of bowing
2016-01-08_11-52-22 (1024x686).jpg
Older scan, with minimal bowing
2016-01-08_11-52-18 (1024x686).jpg
Older scan with minimal bowing
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Re: Calibration Panel - left and right inner point

Postby Vito » Fri Jan 08, 2016 12:18 pm

also, some pictures of the calibration corner
Attachments
134ee72e-1509-4ad0-a09c-0854df1cfb30 (768x1024).jpg
b9ef6089-9dd9-4f3f-b00a-9d47d0ed60b3 (768x1024).jpg
75881d95-38b6-4219-968e-841c8e783660 (768x1024).jpg
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Re: Calibration Panel - left and right inner point

Postby micr0 » Fri Jan 08, 2016 2:40 pm

David assumes that the panels are exactly 90° to each other. Get a carpenters square and check your panels if you are not sure. One thing you can try is inverting the corner (so that the markings are on the outside of the panels and the corner is the closest part to the camera). I find this helps because it eliminates reflected light between the panels. Also check that the camera is the right distance and angle to the panels. I have found that most of my scanning problems are due poor calibration. I spent a lot of time improving my calibration equipment and set up.

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Re: Calibration Panel - left and right inner point

Postby Vito » Fri Jan 08, 2016 2:50 pm

micr0 wrote:David assumes that the panels are exactly 90° to each other. Get a carpenters square and check your panels if you are not sure. One thing you can try is inverting the corner (so that the markings are on the outside of the panels and the corner is the closest part to the camera). I find this helps because it eliminates reflected light between the panels. Also check that the camera is the right distance and angle to the panels. I have found that most of my scanning problems are due poor calibration. I spent a lot of time improving my calibration equipment and set up.

µ


Thanks for the answer, but I am not sure you got the problem. The panels will be 90° because they are mounted on the L shaped guides provided in the SLS-2 system. It is a matter of the gap between the panel and offset, not angle.
Furthermore: I understand that the camera should be at the same distance from the panel as the object that should be scanned, but what do you mean by "the right angle" to the panels?
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Re: Calibration Panel - left and right inner point

Postby micr0 » Fri Jan 08, 2016 4:30 pm

I think that should have been "correct" angle. Too acute or obtuse an angle can cause inaccuracies. When you say "offset", are you talking about the gap where the two panel edges meet? The first column of dots on each panel should be a distance from the edge that is exactly one half the distance of the second column of dots to the first (and the second to the third etc). If the panels edges are not together then this first dimension will be disproportional to the dot spacing of the rest of the panel and could throw your calibration off.

Does this answer your question?

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