US Patent 11567329 Low-power semi-passive relative six-degree-of-freedom tracking

A system for tracking a position and an orientation of an external device such as a smart watch or a handheld controller relative to a head mounted display (HMD) device is provided. A combination of active markers and passive markers on the external device may be detected by a point tracking camera of the HMD to collect position data for the external device relative to the HMD. Acceleration and/or orientation data of the external device relative to the HMD may be collected from an inertial measurement unit(s) (IMU(s)) of the external device and/or the HMD. The fusion of the position data with the data collected by the IMU(s) may allow for tracking of the external device relative to the HMD.