Stereo calibration using OpenCV

[Bertz]

I've got some problem with stereo calibration using OpenCV library. I've got more or less expected results (with high amount of error though) only when I not moving calibration chessboard much, so it looks like intrinsic parameters are inconsistent. Can autofocusing be the reason? Is it possible to control it somehow?

Thanks!

[Joe_Ward]

No the cameras are fixed focus. They do have complex distortion, though. What types of distortion can the OpenCV API you are using handle?

[Bertz]

I'm using C++ OpenCV 3.1 library, and according to docs it can handle radial and tangential distortion. I have used it for calibrating wide angle lenses with standard web cameras.

Thanks, now it makes sense! Lately I was getting better results with my chessboard in the middle of image (less distorted part). I think in that case I should try to apply distortion map from Leap Motion API and try to do stereo calibration after that.

[Bertz]

Tried with pre-undistored images, calibration behavior is the same with even bigger error.
This is the result I've got:

Some parts of images was aligned properly, but apparently amount of distortion is more than OpenCV can handle. If anyone was able to do successful calibration, please let me know. For now, I will try to do detection in plugin and use rectify() function from Leap Motion SDK.

[Joe_Ward]

I spoke with one of our computer vision guys. He said that it is possible to calibrate directly with OpenCV, however it wasn't easy. You have to give it lots of different poses with the chessboard. Also, he said that the pinhole camera model wasn't a good starting point.

[Bertz]

That's good to know! It is quite hard to get a lot of different poses especially for the corners of image since there is not enough light coming from IR LEDs. Maybe bigger chessboard and additional IR illumination can help.

Anyway, I was able to implement simple image processing with OpenCV in native plugin, and use triangulation example from pre-Orion SDK to get the tracked controller position.

[flankechen]

Hi Bertz, what you mean by the pre-Orion SDK, I can't find the triangulation example.
I am working on something needs leap motion camera intrinsics, do you know a reasonable way to do this?
Opencv is not producing good enough results, the FOV of leap camera is much too big for a pinhole model calibration.

[Bertz]

Hello!
I've ended up not using camera intrinsic parameters at all in my project since I was not able to calibrate the Leap Motion cameras properly. Instead I used code from "Calculate the Direction to an Image Feature" section at https://developer.leapmotion.com/documentation/v2/cpp/devguide/Leap_Images.html

[sattar_asd]

I have done camera calibration and had used camera parameters for depth image

@ankababubilla I have done camera calibration and successfully got parameters for depth map, you can check below my depth image result. The only thing left is pointcloud , anyone here who have done pointcloud creation ? I would be very helpful to me [image] [image] [image] [image]