# How to calibrate two cameras whose field of View is 180 deg apart

I have two cameras which are fixed back to back and they view exactly opposite directions. I need to find the extrinsics between the two cameras. They dont have fish eye lenses. The cameras are two primesense RGBD sensors. I am trying to calibrate the two RGB cameras or two IR cameras in the respective sensors

Options which I could think of (by adding intermediate cameras with overlapping views):

1. Multi camera calibration: Bo LI IROS 2013
2. Pairwise Stereo calibration with checker board

Ha s anyone solved this problem?

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" they view exactly opposite directions" -- it's not, what is usually meant with "stereo", then, you'll probably have to calibrate them seperately (like with a single camera).

http://docs.opencv.org/master/d4/d94/...

do they also have fisheye lenses ?

( 2017-10-10 02:46:02 -0500 )edit
1

I need to find the extrinsics between the two cameras. They dont have fish eye lenses. The cameras are two primesense RGBD sensors. I am trying to calibrate the two RGB cameras or two IR cameras in the respective sensors.

( 2017-10-10 03:02:02 -0500 )edit

^^ that's important information, why didn't you write it in your question... ?

( 2017-10-10 03:03:50 -0500 )edit

ok. I ll edit it and put it.

( 2017-10-10 03:05:48 -0500 )edit

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The easiest way involves another camera.

First calibrate the camera intrinsics for all three really well.

Then get two calibration targets (chessboards) and place one in the FOV of each of the opposing cameras. Then use the third to take a video that contains both targets in the frame at the same time.

So to find the transform from Camera A to Camera B (the opposing cameras), you need to go Camera A -> Chessboard A -> Camera Ext -> Chessboard B -> Camera B

There's a lot of room for error there, so you'll need several views from the external camera per positioning, and several positionings of the chessboards to get good results.

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