Camera Lens Calibration

Navigation:  Widget Designer > Nodes > Input Nodes > Devices Input > ID Tag Tracker Input >

Camera Lens Calibration

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Navigation:  Widget Designer > Nodes > Input Nodes > Devices Input > ID Tag Tracker Input >

Camera Lens Calibration

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This topic explains the section "Camera Lens Calibration" of the ID Tag node, for general information about IR ID tracking and links to other chapters please see the topic ID Tag Tracker.

wd_nodes_input_id-tag-tracker_camera-settings_calibration-only

This section includes all settings for calibrating the lens.
Each lens deforms its image in a different way and it increases the accuracy of the tracking if this deformation is compensated. The lens deformation usually needs to be done only once as long as the lens is not removed. For the very best accuracy it is recommended to redo the calibration if the lens focus is altered.
As long as the cameras are not calibrated by you, Widget Designer calls the default calibration files from its installation path:
C:\Program Files (x86)\coolux\Widget Designer 4.5 Rev 708\Data\camera
If the default or your custom calibration files were able to be loaded, the section will be colored green, otherwise red.
For calibrating a lens you need a special image that depicts a checkerboard (details below...). You can either print on a hard board or glue a printed paper to it. Note, that the board needs to be as straight and plane as possible.

Wrench Icon

The button opens the "Camera Calibration Settings" dialog which is described in more detail below... In short, here you set up how the image looks like that you use for the calibration. The image is a checkerboard and is hold in different poses in front of the camera whilst snap shots are saved.

Calibrate

This calibrates the selected camera with the settings taken in the "Camera Calibration Settings" dialog.

Folder / Load Icon

Click the Folder Icon if you have calibrated the selected camera before and  wish to load its data from a different path than the default one: C:\Program Files (x86)\coolux\Widget Designer...\Data\camera

Disk / Save Icon

Click this button if you wish to save the calibration data for the selected camera to a different folder than the default one: C:\Program Files (x86)\coolux\Widget Designer...\Data\camera

Camera / Precision Icon

Click this button if you wish to see the result of the Calibration (again).

FOV

This informs you about the field of view of the camera lens. The FOV is calculated during the Calibration and cannot be changed manually.

Camera Lens Calibration Steps

wd_nodes_input_id-tag-tracker_camera-calibration-settings_zoom66First, click the Wrench Icon to open the left depicted dialog.

The first drop-down and two check-boxes let you choose the calibration method. Afterwards, enter the FOV of the camera lens. Now, all settings relate to the checkerboard:
Square Size: how wide and high is one square, measure in centimeters!
H Count and V Count: how many horizontal internal corners are there and how many vertical ones (click the info button for more information)
Image Count: how many images will be taken (16 is the recommended minimum)
White / Black Board: is the border around the checkerboard white or black
 

wd_nodes_input_id-tag-tracker_chessboard-setup-info_zoom54This dialog explains the horizontal and vertical square count.

 

 

wd_nodes_input_id-tag-tracker_camera-calibration-manual-mode_zoom55You then hold the checkerboard in front of the camera and take pictures whilst moving either the board or the camera in such a manner that the board covers different parts of the taken image.

click to enlargeThe left image shows recommended calibration poses. Click it, to enlarge the image.