Method and device for optically aligning the axels of motor vehicles

A method for providing optical axle alignment of the wheels of a motor vehicle, the method comprising:

• using a measuring unit, in a measurement process, to take at least one stereoscopic image of at least three marks of a planar target mounted on a wheel, wherein a plane defined by the planar target is perpendicular to a plane defined by a side wall of the wheel;
• ascertaining, using an evaluation unit, a spatial position of a rotational axis of the wheel in a previously determined local 3D coordinate system using image processing, and in which, in a referencing process, a measuring location reference system is established for the measuring unit, a calibration process being carried out before the measuring process, in which the targets rotate about the rotational axis of the wheel, and in the calibration process, using at least three marks of the target, the local 3D coordinate system is established and the spatial position of the rotational axis of the wheel is ascertained;
• and
• during a subsequent measuring process, while the wheel is standing still and the target is unmoved, the spatial position of at least the at least three marks of the target drawn upon during the calibration process is ascertained, in the local 3D coordinate system, wherein, during the calibration process, a determination of a reference plane is carried out using a significant mark of the target, the significant mark on the targets of the wheels of the same axle having an identical distance from a common reference area.