An articulating joint for a coordinate measurement machine can include an improved optical encoder. The optical encoder can have an encoder hub and a read head that are rotatable with respect to each other based on movement of the articulating joint about an axis of rotation of the joint. The encoder hub has a read surface. The read surface can be an outer surface of a generally cylindrical segment. The read head can be positioned such that a read direction defined by the read surface is generally perpendicular to the axis of rotation of the articulating joint.