US Patent 10254546 Optically augmenting electromagnetic tracking in mixed reality

A mixed reality system may comprise a head-mounted display (HMD) device with a location sensor and a base station, mounted a predetermined offset from the location sensor, that emits an electromagnetic field (EMF). An EMF sensor affixed to an object may sense the EMF, forming a magnetic tracking system. The HMD device may determine a relative location of the EMF sensor therefrom and determine a location of the EMF sensor in space based on the relative location, the predetermined offset, and the location of the location sensor. An optical tracking system comprising a marker an optical sensor configured to capture optical data may be included to augment the magnetic tracking system based on the optical data and a location of the optical sensor or marker. The HMD device may display augmented reality images and overlay a hologram corresponding to the location of the EMF sensor over time.