Correction of Lens Distortion and Camera Tilt

In order to increase the detection success of Geometric and Correlation objects, to operate the robot with higher accuracy, and to measure the dimensions with higher accuracy, lens distortion and camera tilt can be corrected.
Position the square lattice pattern like the sample shown below so that it fills the entire field of view, and then perform lens distortion calibration. The lattice pattern must be square. The optional calibration plate can also be used.

This square lattice pattern is essential for distortion correction. Prepare a lattice pattern with minimum distortion as possible and place it on the work plane in the camera’s field of view. When placing the lattice pattern, also consider its working distance (WD) from the camera. It is necessary to place the pattern at the same height as the work piece height where the actual work piece will be detected.

The angle of the lattice pattern is not necessary to be aligned to that of the camera’s field of view.

It is important to set the square lattice pattern so that it fills the entire field of view of the camera. If calibration is performed while the lattice pattern is in only a part of the field of view, distortion cannot be corrected properly since the area with no lattice pattern is not taken into account.
When executing calibration, make sure that at least 100 points of the lattice pattern are within the field of view.
After completing correction of lens distortion and camera tilt, subsequent camera images will be corrected when they are captured, and images with less distortion can be obtained.

Tips:
When executing calibration, an error may occur depending on how the lattice pattern is captured. In this case, calibration can be done properly by adjusting the lattice pattern and executing calibration again. Also, set the camera so that the angle between camera’s optical axis and the lattice pattern is 45 to 90°. If the camera angle is 45° or less, calibration will become an error.