Self-calibrating 3d machine measuring system useful in motor vehicle wheel alignment

Abstract

Techniques are disclosed for providing a system that has a plurality of devices in which the position of a device of the plurality of devices relative to another device of the plurality of devices is self-calibrated. In one embodiment, the system is a five-camera aligner for use in aligning motor vehicle wheels. In this embodiment, the aligner includes a first camera pod having two alignment cameras and a calibration camera, and a second camera pod having another two alignment cameras and a calibration target. Because the aligner has four alignment cameras and a calibration camera, the aligner is often referred to as a five-camera aligner. For illustration purposes, the first camera pod is herein referred to as the left camera pod and the second camera pod is herein referred to as the right camera pod. In one embodiment, the left camera pod is placed to the left of the aligner, and the right camera pod is placed to the right of the aligner. The two alignment cameras of the left camera pod focus at the two left wheels of the vehicle under alignment, while the two alignment cameras of the right camera pod focus at the two right wheels of the same vehicle. In addition, the calibration camera on the left pod focuses at the calibration target mounted in the right camera pod. In one embodiment, the relative positions of the elements (alignment camera, calibration camera, and calibration target) in each camera pod are pre-calibrated. Consequently, the aligner is fully calibrated when the position of the left camera pod to the right camera pod is measured. Further, the calibration camera is configured such that it periodically measures the position of the left camera pod relative to the right camera pod, rendering the aligner a self-calibrated aligner.