Wave in point cloud

[jakobwilm]

Wave in point cloud

[DuanMH]

Hello, same problems exist in my experience, such as lightcrafter 4500 cannot project the designed patterns.

[nikkadim]

If you project patterns from seconds screen - adjust gamma correction.

[jakobwilm]

This is most probably the same problem as in most issue requests: your projector-camera pair does not have a linear gray-value response. This can have many causes, but you would start by measuring the response to start finding the bug.

[DotZ1]

Thanks for the feedback. As a test I embedded the patterns straight onto the 4500 and captured them through the camera but I am still getting the waves in my point clouds. Does that mean to might point to a gamma problem in the camera setup as from what I understand the 4500 does not apply any gamma correction to the patterns (it would do this only in video mode on the 4500)?

[jakobwilm]

Yes, something non-linear in the camera or a trigger timing issue. As I said before: you have to do measurements.

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On 4 Mar 2019, at 10.30, DotZ1 ***@***.***> wrote: Thanks for the feedback. As a test I embedded the patterns straight onto the 4500 and captured them through the camera but I am still getting the waves in my point clouds. Does that mean to might point to a gamma problem in the camera setup as from what I understand the 4500 does not apply any gamma correction to the patterns (it would do this only in video mode on the 4500)? — You are receiving this because you modified the open/close state. Reply to this email directly, view it on GitHub <#35 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AEQSmNV6ey9nWKqFZowEo_bebU-ouGsYks5vTOecgaJpZM4bOqCY>.

[DotZ1]

Many thanks for the quick response.

[DotZ1]

Sorry one last question on the theory of figuring out the gamma response. I understand you have a matlab function that will tell you the response but could you explain the theory a little. Do you just project a fixed set of gray values from the projector (for example all a value of 100 and check the response) or do they go from dark to bright across the width of the image or some other variation. Thanks in advance

[matBBA]

Hi DotZ1,
This may be closed, but I had similar waves in my application. It turns out the culprit was then neon light in the room. The projector I used projects sinusoidal patterns by concatenating various black & white pictures in a short period. And I guess each b&w pattern was a bit modified by neon light at this exact moment ( as I changes at ~100Hz if you're In Europe).

As soon as I turned the lights off, this effect was gone...