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Newbies Beamer vertical angle

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

Newbies Beamer vertical angle

Postby onap » Wed Jul 27, 2016 10:14 am

Hello All,

For a month now I'm playing with David scanner trial version with first a laser and a webcam and in a second time with a beamer (acer K135) and a C920 modified for CS-mount (Kurokesu case)

Before buying David 5 software and another camera, I'm designing a support to put the beamer and the camera on a rail.
As I could see on SLS-3 picture is a vertical angle between the K132 beamer and the camera. What is the value of this angle and why there is this angle.

Thanks in advance

Olivier
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Re: Newbies Beamer vertical angle

Postby hal » Wed Jul 27, 2016 10:43 am

Hello dear Olivier,

The angle between projection's axis of projection and camera axis of view should be at least 20° in order to get good results. With two cameras in "stereo mode" you can set each one at lower value, till 10°. That don't means that higher values in both cases can works better (less risks to have distortions - take in mind that the triangulation principle works better with "stronger" angles).
I've tried with 2 cameras both on a rail, at the sides of the projector. Approx 20° each one. Working fine. Still not tested the "extended mode".

Regards,
Mattia
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Re: Newbies Beamer vertical angle

Postby onap » Wed Jul 27, 2016 11:32 am

hal wrote:Hello dear Olivier,

The angle between projection's axis of projection and camera axis of view should be at least 20° in order to get good results. With two cameras in "stereo mode" you can set each one at lower value, till 10°. That don't means that higher values in both cases can works better (less risks to have distortions - take in mind that the triangulation principle works better with "stronger" angles).
I've tried with 2 cameras both on a rail, at the sides of the projector. Approx 20° each one. Working fine. Still not tested the "extended mode".

Regards,
Mattia


Thanks Mattia,

Are you talking about horizontal axis or vertical axis. When looking on SL-3 system picture ( http://www.growshapes.com/store/p40/DAV ... AVID4.html ), the beamer is tilted downwards. What is this angle value

Thanks in advance

Olivier
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Re: Newbies Beamer vertical angle

Postby hal » Wed Jul 27, 2016 11:40 am

Hi, well don't care about that rotation.
You need to focus only on the horizontal one. If your projector and camera are looking at the same point in front of them, you no need takeing care about other angles. Obviously you can move also the vertical position of hardware, but I don't suggest to do that.
So, put the calibration angle in position, move the focus pattern (the one with the grid and cross) centered and adjust the camera position and rotation. Set both the optics and have good focus on the corner. Done, you ready to calibrate and scan.
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Re: Newbies Beamer vertical angle

Postby avogra » Wed Jul 27, 2016 4:08 pm

i think the tilt is there because the beamer is projecting upwards. to have the cameras look at the center of the projection, the cameras have to look up or the beamer has to be tilted down. No idea, what the correct angle is. You could make it adjustable, like in SLS-1.
Projector: Acer K11 with Achromat f=400mm | Cameras: 2x Logitech 9000 Pro with custom C-Mount body | Lenses: 1x Computar M1214-MP, 1x Computar M5018-MP, 1x Schneider-Kreuznach Cinegon CNG 1.4/12
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Re: Newbies Beamer vertical angle

Postby gkrywusha » Thu Jul 28, 2016 5:05 am

The angle of the projector is somewhere between 10-15 degrees. I create a wedge for the rail that the projector sits on to be project straight at the scanning target.
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