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Four cameras are arranged in a ring shape. How to calibrate the relative postures of the four cameras, that is, the attitudes of the other three cameras relative to the camera 0, the difficulties are:

  1. When using a calibration plate, four cameras cannot see the calibration plate at the same time, and only two cameras can see the calibration plate, such as calibrating cam1 relative to cam0, then calibrating cam2 relative to cam0, and cam2 can only be relative to cam0. The indirect calculation, causing errors;

  2. In the case of only calibrating two cameras, such as cam0 and cam1, the calibration plates seen by both cameras are tilted, and the calibration plate changes angle is small, which also causes errors.

Is there any better way to calibrate, thank you

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Mario
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user3395730
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  • Your approach seems to be legit. However I have been wondering if your chessboard is prone to bending, how many corners do you have in the chessboard, what are your initial conditions, how many observations do you have and do you have precisely estimated intrinsic parameters of each camera before estimating T/R between cameras? – Darko Lukić Jun 28 '19 at 15:50

1 Answers1

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There are many ways and papers introduced to this.

The similiest way is to calibrate two at a time. The pair need to be havig largest common FOV. But there are other methods as well.

  1. You can use structure from motion-based method to move the camera around and jointly optimize for the camera poses. It was first published in CVPR between 2010 to 2016. forgot the exact year, but it about camera calibration with minimal or zero overlap.

  2. You can add an IMU and use kalibra to calibrate them. Anchor all image to this IMU. https://github.com/ethz-asl/kalibr/wiki/camera-imu-calibration. An alternative that I frequently use is the Robotics HAND EYE calibration System used in VINSMONO https://github.com/HKUST-Aerial-Robotics/VINS-Mono. The VINSMONO one requires no complicated pattern. just moving around.

  3. For my paper, We use sea level vanishing line and vanishing point to calibrate cameras which cant get the same chessboard pattern in the same view. Han Wang, Wei Mou, Xiaozheng Mou, Shenghai Yuan, Soner Ulun, Shuai Yang, Bok-Suk Shin, “An Automatic Self-Calibration Approach for Wide Baseline Stereo Cameras Using Sea Surface Images”, Unmanned Systems, Vol. 3, No. 4. pp. 277-290. 2015 enter image description here

There are others as well such as using vicon to image tracking system or many other methods. Just find one which you think is suitable for you and try it out.

Dr Yuan Shenghai
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