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180 DEGREE CALIBRATION PANEL

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

180 DEGREE CALIBRATION PANEL

Postby RAYA » Thu Aug 20, 2009 5:07 pm

Hi Gunter

Did you experinced 180 degree calibration with accuracy checking or comparing to normal calibration panel(90).


Ray
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Re: 180 DEGREE CALIBRATION PANEL

Postby MagWeb » Thu Aug 20, 2009 8:52 pm

Hi,

180°?
means both patterns are on the same plane >>> this does not work!
The patterns have to be on two different planes ( noncoplanar)
(Two years ago I made such things but failed)

120°
This is the flattest, highest angle I used until now ( for it is ideal for the mirror scanning thing). It´s hard to compare the accuracy. I got similar results, no notable loss of quality using 120°. But theory seems to be logical: the lower the angle, the better should be the effect on a precise laserplane calculation .

Gunter
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Re: 180 DEGREE CALIBRATION PANEL

Postby RAYA » Mon Aug 31, 2009 7:12 pm

Hi Gunter

What do you think about negative 90 degree calibration panel (positive 270 degree) ?

It is just to have more space for some special object for scanning (with calibration panel ).

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Re: 180 DEGREE CALIBRATION PANEL

Postby MagWeb » Tue Sep 01, 2009 9:00 am

Hi Ray,

allmost 2 years ago I used a 270° angle (I called it "minuscorner") to calibrate a window setup. See:http://www.david-laserscanner.com/forum/viewtopic.php?f=3&t=133&hilit=Minuscorner#p618 BTW: this was my first post.

I also checked the use of detection planes at 270° some problems: At that time the backgroundfilter wasn´t configureable. So this filter often cut through the meshes. I got negatve meshes too (for the reference was negative..... But that´s the past.
I dropped that for the planes have to be much bigger (for perspectivity). Also the depth of sharpness of the laser makes trouble - the object is much farer from the planes.

Today you have the possibility to define the planes' angle freely. So I would try a negative 120° (means 240°) corner instead of a 270° rightangled one. Means the planes are nearer to the object, >>> less depth, smaller planes....

To do this you´ve to recalculate the markers position in the calibpoints.dat and define the normal vectors of both planes in the advanced settings.

Gunter
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Re: 180 DEGREE CALIBRATION PANEL

Postby RAYA » Fri Sep 18, 2009 11:54 pm

Hi

In reverse engineering field dimension of scanned object act as important rule and in scanning field calibration also.

Making presice rightend calibration panel is difficult and expensive but how about calibrating with only one plane (flat calibration panel) ,is it possible ?

Is it possible to have 3rd dimension (x,y,z) with an angled to cam axis flat plane ?

Is it possible to change plane pattern to give more easiest calibration process ?

Ray
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Re: 180 DEGREE CALIBRATION PANEL

Postby Sven » Mon Sep 21, 2009 3:14 pm

Hi Ray,
Yes, it is possible to calibrate a camera with a flat calibration pattern (one plane only, "coplanar"). However this is not implemented in DAVID.
But during scanning, as you know, we need more that one plane to calibrate the LASER.
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