Patent ID: 8639471

Claim:
A method for determining a position of a mobile controller relative to a fixed unit, wherein the mobile controller comprises an infrared (IR) light source and an ultrasonic transducer, and wherein the fixed unit comprises a camera and a first ultrasonic transducer, the method comprising the steps of: using the camera to determine an angular location of the IR light source relative to the fixed unit; determining a distance between the mobile controller and the fixed unit by measuring a time of flight of an ultrasonic transmission between the mobile controller and the fixed unit; determining a three dimensional position of the mobile controller, relative to the fixed unit, by combining the angular location with the distance; using the camera to track a path of the IR light source detected over time; and using the tracked path to distinguish the IR light source from a background light source, when the IR light source and the background light source are detected close to each other, by comparing the tracked path with a extrapolated path of the IR light source.