US Patent 7624510 Joint axis for coordinate measurement machine

One aspect of the present invention comprises a coordinate measurement apparatus that includes an articulated arm having a first end, a second end, and plurality of jointed arm segments therebetween, each arm segment including at least one position transducer. A measurement probe assembly is coupled to the second end of the arm. The measurement probe assembly comprises a first joint providing a first axis of rotation between the second end of the arm and a body of the measurement probe assembly. An encoder includes an encoder housing and an encoder shaft. The encoder housing is configured to rotate about a second axis with respect to the encoder shaft, which is rigidly coupled to the body. A probe is rigidly coupled to the encoder shaft. A measurement device is coupled to the encoder housing such that the measurement device rotates about a second axis with respect to the probe.