Vehicle wheel alignment apparatus and method

Abstract From the Canadian patent

Noncontact sensors project fanned or structured light onto the tire, while the wheel is rotated, to illuminate at least two contour lines on the surface of the tire. The contour lines are read by video cameras, positioned offset from the optical plane of the structured light, to allow triangulation in determining the spatial position of the contour lines. Radially equivalent points are selected from each contour line by an algorithm which ignores the effects of any raised lettering on the tire sidewalls. Control of the video cameras and processing of the video data is performed by parallel processor-based computer system coordinated by sequencer circuit.