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Intersection angle etc..

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

Intersection angle etc..

Postby mootsoo » Sun May 15, 2011 8:25 pm

I'm still trying to scan.
Sometimes I'm having some ugly or some scanned objects which has noise. Object with noise is okay, I'm happy for that.
But sometimes I couldn't get any result and I'm assuming that because of color of object. Is it true?
Because my camera isn't good, only 1.3 mpixel web camera. Mostly I'm reading that word : " Laser line not detected (too short/too weak)
Left and Right laser not on plane and
Intersection angle is too low.

I don't understand what is Intersection angle.

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Postby hal » Sun May 15, 2011 9:50 pm


intersection angle is the angle between the laser plane and camera's horizont plane.
From the David manual: "You must hold the laser rather “high”, i.e. the distance between the laser light plane and the camera must not be too small. Otherwise you will get the error message INTERSECTION ANGLE TOO LOW!"
This angle is foundamental to calculate the triangulation of every 3D point. Probably you need to show better the laser line on the right and left panels and/or coat your object (otherwise the laser line isn't visible enough).
Please post in this discussion a grab-image of your laser line on the panels and on the object (as shown in the images linked above).

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Re: Intersection angle etc..

Postby WalterMo » Sun May 15, 2011 10:32 pm

May I additionally add, for a better understanding, a graphic with the intersection angle.

It is the angle between the laser plane and a lot of imaginary lines between the camera and the place where the laser just illuminates the object and the walls left and right.
During scanning DAVID displays this angle as an average value generated along the laser line. It is averaged because the object isn't normally plane but has its own surface structure. Like here for Ludwig van Beethoven.
Have a look to the expository diagram of Gunter, July 22th 2008:


Intersection angle.jpg
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