Method and apparatus for optically scanning a pneumatic tire of a vehicle wheel

An apparatus for optically scanning a pneumatic tire of a vehicle wheel that is rotatably mounted on a measuring shaft of a wheel balancing machine, comprising:

• three sensor devices, each comprising a light source that emits a light beam configured to scan the surface of the pneumatic tire while the wheel is rotating to form at least one light spot on the tire surface, and a receiver movable together with the light source, wherein the receiver is configured to receive a beam reflected by the surface of the pneumatic tire while the wheel is rotating, and produce a signal based on the receiving position of the reflected beam at the receiver, and wherein each light source and corresponding receiver are movable together into given positions relative to the measuring shaft for measuring the distance of the at least one light spot relative to a reference position;
• a rotary angle sensor, coupled to the measuring shaft, for generating a rotary angle associated with the at least one light spot of each sensor based on the rotation of the measuring shaft and the vehicle wheel;
• and
• a computer-aided evaluation device, coupled to the rotary angle sensor and the receivers, for ascertaining dimensions and positions of the pneumatic tire or constituent parts of the pneumatic tire based on the measured distance of the at least one light spot of each sensor and the associated rotary angle position of the rotating vehicle wheel;
• wherein one of the sensor devices is configured to scan the tire tread surface, and the other two of the sensor devices are configured to scan the tire side walls at the inside and the outside of the wheel such that all external surface spots of the tire are scanned, and the sensor devices are attached to movable components of a wheel balancing machine.