User Manual

First, the grid should be held closer than 40 cm from the sensor. It must be fully visible in both images and the
cameras should look perpendicularly onto the grid. A green outline that stays in the image indicates the images’
acceptance.
Fig. 6.6.6: Holding the grid closer than 40 cm during stereo calibration
Next, the grid should be held at least 1 m from the cameras. The small cross in the middle of the images should be
inside of the grid and the cameras must look perpendicularly onto the grid. A green outline that stays in the image
indicates the images’ acceptance.
Fig. 6.6.7: Holding the grid farther away than 1 m during stereo calibration
Note: If the check marks on the calibration grid all vanish, then either the camera does not look perpendicularly
onto the grid, the green cross in the middle of the images is not inside the grid, or the grid is too far away from
the camera.
Step 4: Storing the calibration result
Clicking the Compute Calibration button finishes the process and displays the final result. The presented result is
the mean reprojection error of all calibration points. It is given in pixels and typically has a value around 0.3.
Note: The given result is the minimum error left after calibration. The real error is definitely not less than
this, but could in theory be larger. This is true for every camera-calibration algorithm and the reason why
we enforce holding the grid in very specific poses. Doing so ensures that the real calibration error cannot
significantly exceed the reported error.
Pressing Save Calibration applies the calibration and saves it to the sensor.
Warning: If a hand-eye calibration was stored on the rc_visard before camera calibration, the hand-eye
calibration values could have become invalid. Please repeat the hand-eye calibration procedure.
6.6.3 Parameters
The component is called rc
_
stereocalib in the REST-API.
6.6. Camera calibration 53