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Stereo Calibration of two cameras with different camera resolutions

Asked by Mohammad on 4 Sep 2014
Latest activity Commented on by Image Analyst
on 16 Sep 2019
Hi Everyone;
I have just started with camera calibration and found the awesome APP that MATLAB has to perform the calibration. Unfortunately, we cannot perform stereo calibration with it.
However, there is a matlab example that allows for stereo calibration but the problem I am having is that the resolutions of the two cameras I am using are different. One is high definition (1980X1080) and the other one is (512X412) so I cannot use the code from the example unless I try to modify the image.
So I am guessing I should kind of "cut out" the middle 512X412 of the 1980X1080 image to make the calibration? or would imsize work? Seems to modify the image too much.. Anyone has any idea on how this can be done or the camera calibration in general can be done?
Thanks; Ali

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3 Answers

Answer by Shida
on 23 Feb 2015
 Accepted Answer

Hi, It's very normal to have to calibrate two cameras of different resolution when working in Multi-modal imaging. It's always the case that you have two different sensors with different technologies and highly unlikely that they have same resolution. Kinect is of course a very common example. Unfortunately, the official matlab app doesn't support this. There are some codes which make this possible for kinect 1 which you can google. But if you're looking for something with kinect 2, you can try first using the detectCheckerboardPoints from matlab for each set of images (check the matlab manual) and then when you have the points use : imagePoints = cat(4, poitnsRGB, pointsIR); Then feed these to the estimateCameraParameters (check the manual for more info). The catch is that I've done this for a HD camera and the kinect IR and I get terrible amount of error. I'm still trying to fix this. Worst case, one can use Kinect 1 with one of the available calibration codes.
Regarding what you said about cropping the images, that's a calibration sin ! If you look up info on how to calibrate cameras, they always tell you not to do that because that messes up everything.
Good luck.

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Hi, I just found your another answer in this link with more details: https://www.mathworks.com/matlabcentral/answers/268152-mapping-rgb-and-depth-kinect-v2#answer_209992
And it works! Now the reprojectionError and the cameraParameters are correct.
Thanks for your provided codes and explanations :)
Hey Shida, I followed the same steps you provided, and it worked. Thanks a lot for sharing it. :)

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Answer by Image Analyst
on 4 Sep 2014

I'd buy another camera. Why complicate things when simply buying another camera will solve the problem?

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Well the device I am using is the new Kinect for Windows V2 and I am trying to see how good the factory calibration is for this new device. So I kind of need the rotation and translation matrix inbetween the two new cameras. Thanks
Hania Alhamad comments to Image Analyst
The answer is irrelevant. Some times there is a need to calibrate two cameras with different resolutions. and buying cameras won't solve the issue. like for example calibrating a thermal and a RGB.

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Answer by muhammet balcilar on 14 Jul 2018

Yes, it is still problem to calibrate different resolution camera for stereo vision system. I had the same difficulties. However I just modifie some functions and prepare a demo. here you can find my demo.

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it is not possible to rectify the images in the same resolution of the given image resolution.
But it is possible to project one image into another image. I just updated the demo code and added the results of the projection to the low-resolution image onto the high-resolution image. But without knowing the real depth of the object it does not work 100% accurate. In the given demo, I just supposed all objects are on Z=0 plane where the top-left corner of the first calibration checkerboard is our reference (0,0,0).
within that projection for instance if you have one thermal camera and one USB camera you can know the temperature of each pixel on usb camera image under the assumption that all objects are at Z=0 plane . Just check the updated demo,
Hi Muhammet,
I am trying your code for calibration of cameras with different resolutions, but one of my undistorted image is completely black.
Do you have any idea about this error.
Maybe they're floating point images not in the range of 0-1 so you need to use [] in imshow():
imshow(floatingPointImage, []);

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