US Patent 7201069 Angle sensor

An angle sensor includes a first gear configured to be concentrically mounted to a rotor, a second gear configured to mesh with the first gear, and a first rotation angle detector configured to detect a rotation angle of the second gear, wherein the first rotation angle detector outputs absolute angle signals according to the rotation angle of the second gear, generates a first pulse based on rotation of the second gear, generates a second pulse having a different phase compared to the first pulse based on rotation of the second gear, generates a third pulse once per rotation of the second gear based on rotation of the second gear, varies each resolution of rotation angles of the first pulse, the second pulse, and the third pulse, and detects the rotation angle of the second gear in accordance with the resolution.