Reference Points for Fixed Camera
The 'Fixed Downward' and 'Standalone' calibration schemes require a calibration target plate or sheet that contains nine targets.
Fixed Camera Calibration Targets
For 'Fixed Downward' calibrations, the targets could be holes in a plate that a rod on the robot end effector can be slipped into. The distances between the targets do not have to be exact.
For Standalone cameras, a pattern sheet can be used. The horizontal and vertical distances between the targets must be known.