MACHINE VISION METHODS USING FEEDBACK TO DETERMINE CALIBRATION LOCATIONS OF MULTIPLE CAMERAS THAT IMAGE A COMMON OBJECT

摘要

The invention provides improved machine vision methods for determining a calibration relationship among the imaging reference frames of multiple cameras (16) that acquire images of a common moveable object (12). The calibration relationship includes parameters for transforming positional coordinates among the camera's (16) respective imaging reference frames. The method includes placing on the common object (12), stage, or belt a plurality of fiducials (14), e.g., calibration marks, that are at known positions relative to each other with respect to a frame of reference referred to as the 'alignment reference frame'; aligning an axis of the alignment reference frame with an axis of the object's reference frame of motion, i.e., the reference frame in which the object (12), frame or belt moves; placing a respective fiducial (14) in the field of view of each camera (16); determining a calibration relationship among the imaging reference frames of the respective image acquisition devices as a function of the known relative locations of the fiducials (14) the fiducial calibrating positions determined for each camera (16) and the object calibrating positions determined for each respective image acquisition device.