Calibration
Overview
Calibration is an important part of the Vision Guide 8.0 system.
In order to locate parts in the robot coordinate system, or to make physical measurements, you must calibrate the system.
Vision Guide 8.0 supports mobile (mounted to robot), fixed upward, fixed downward, and standalone camera calibrations.
Calibration Definition
Vision Guide 8.0 supports multiple calibrations for each project. Any calibration can be used with one or more vision sequences in the same project.
Each calibration includes the following data:
| Item | Description |
|---|---|
| Calibration name | The name of the calibration that is referenced by vision sequences. (Up to 16 alphabets.) |
| Camera number | The number for the camera being calibrated. |
| Camera orientation | Camera mounting method |
| Calibration target sequence name | The name of the vision sequence that will be used to calibrate the camera. (This can be any sequence in the current project.) |
| Robot calibration speed and acceleration (when required) | The speed and acceleration used during calibration. |
| Robot Arm number and Tool number used during calibration | You can use an Arm or Tool during calibration. These must be defined prior to teaching points or calibrating. |
| Robot Points for reference and camera locations | These points are saved for each calibration. |
| Light outputs | These are optional standard outputs that can be used to control lights during calibration. |
| Image distortion correction | Specifies whether to execute image distortion (camera tilt and lens distortion) correction |
| Image distortion correction target sequence name | The name of the vision sequence used for image distorting correction. (Any sequence in the current project can be used) |
Each calibration uses nine points that span the field of view of the camera being calibrated.
By spanning the field of view, the system can do the best job of compensating for camera tilt and lens inaccuracies.
When performing a distance measurement with the whole field of view, perform image distortion correction. By performing image distortion correction, camera tilt (angle error between the work plane and the camera’s optical axis) and lens distortion can be corrected.
When do you need to calibrate?
Calibration is required anytime you want to make a physical measurement or locate a position in robot coordinates.
Several results reported for vision objects require calibration. For example, the CameraX, CameraY, RobotX, RobotY, RobotU results require calibration.
Imaging Pattern for Image Distortion Correction
The following is a sample of the image used for image distortion correction.
To perform image distortion correction, the grids must have the same pitches in both horizontal and vertical lines, and more than 100 targets must be seen within the camera’s field of view.
