How to calibrate camera with OpenCV

When using MYNT EYE camera first time, the SDK will download a calibration file for this camera to "settings/SN*.conf".

Besides, the SDK also provides a stereo_calib tool to help calibrate camera with OpenCV by yourself.

stereo_calib

$ cd $MYNTEYE_SDK_ROOT
$ ./tools/stereo_calib -help
Stereo calibration with square chessboard.

  Calibrate the stereo camera and display rectified results along with the computed disparity images.

  Chessboard pattern which has a size of 9 X 6: http://docs.opencv.org/master/pattern.png.

Usage:

  ./stereo_calib -w=9 -h=6 -s=1.0 [-nr] [-n=12 -i=1] <image list>

Options:
                     Default    Description
  -help                         show help message

  -w=<board_width>        9     number of inner corners per a chessboard row
  -h=<board_height>       6     number of inner corners per a chessboard column
  -s=<square_size>      1.0     the square side length in real measurement
                                    scale the vectors of the calibration pattern points
  -nr                           not display rectified results

  -n=<image_number>       0     capture images manually if greater then 0
                                    stored into `./images` directory
  -i=<device_index>       0     device index, but default is MYNTEYE on Windows
                                    `./tools/list_devices` to see indexes on Linux/Mac

  <image list>  ./stereo_calib.xml  given images in a XML/YML file

Calibration

1. Prepare a calibration board with square chessboard.
   • Could print a chessboard pattern and paste it on a board which had better be flat and hard.
2. Plug the camera in a USB 3.0 port.
3. Run stereo_calib to calibrate camera.

    ```
    # Manually capture `12` images of device `1`, then calibrate.
    $ ./tools/stereo_calib -w=9 -h=6 -s=25 -n=12 -i=1
   
    # Using captured images in `images/imagelist.yaml` to calibrate.
    $ ./tools/stereo_calib -w=9 -h=6 -s=25 images/imagelist.yaml
    ```
   

   • If not sure which index is MYNT EYE, you could run ./tools/list_devices.
   • If not -nr option, you will preview rectified results after calibration done.
     • Press space to next or esc to exit.
4. The calibration file will be saved to "<MYNTEYE_SDK_ROOT>/settings/SN*.conf".

SN*.conf

References

• Camera calibration With OpenCV