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Hello everyone,

does anybody have any idea how to calculate the relative transformation between the cameras of a multi camera rig with no overlap?

Thanks in advance.


Originally posted by Ifx13 on ROS Answers with karma: 54 on 2021-07-04

Post score: 0


Original comments

Comment by midjji on 2022-03-03:
It is trivial to do so using any standard toolbox for the calibration of overlapping cameras. All you need is one more camera not part of the rig, which is placed in such a way as to create overlap with both. Then simply chain the transform. The method, including what to do if one camera isn't enough is described in: http://www.diva-portal.org/smash/get/diva2:1185614/FULLTEXT02

This approach is simpler than using a mirror, and more accurate. Further, because the extra camera is only needed during the calibration, you can use a high end one, and achieve very high accuracy. The paper also includes a simulator to show expected accuracy.

As with all camera calibration, to ensure a good result:

  1. Light the scene well, preferably sunlight
  2. use tripods for the pattern and the camera to ensure they are stationary
  3. cover the entire sensor with roughly evenly sampled observations
  4. Use a minimum number of camera parameters
  5. non-monotonic lens distortion is failed estimation
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I would suggest to take a look at ethz-asl/kalibr.

From the readme:

Kalibr is a toolbox that solves the following calibration problems:

  • Multiple camera calibration: intrinsic and extrinsic calibration of a camera-systems with non-globally shared overlapping fields of view

Originally posted by gvdhoorn with karma: 86574 on 2021-07-05

This answer was ACCEPTED on the original site

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Comment by Ifx13 on 2021-07-06:
I've tried this. The thing is that the overlap is practically zero and when they say that the input is "non-globally shared overlapping fields of view" they mean that there is no need for every camera at the rig to have overlapping FoV but there is still the need to have overlap at in between the pairs of the cameras. Also, this package can work with different targets, one of the supported targets is the aprilgrid, this target does not require to be "seen" completely by both cameras, it says that it can be partially viewed but at least one marker of the grid must be seen at both cameras. With my current camera configuration, this is not possible. Not a single marker is shared between images, they're cut in half. Please correct me if misunderstood something.

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