Head-mounted eye tracking system

A head-mounted eye tracking system adapted to track eyeballs of a wearer, the head-mounted eye tracking system comprising:

• a light-transmitting substrate made from a material that allows light to pass through;
• at least two eye trackers configured to sense the eyeballs on the light-transmitting substrate, each eye tracker comprising:
• a light-emitting device on a surface of the light-transmitting substrate, configured to emit a tracking beam;
• and
• a sensing device adjacent to the light-emitting device, configured to receive a reflected beam after the light-emitting device emits a tracking beam;
• a signal processor electrically connected to both of the eye trackers, wherein the surface of the light-transmitting substrate has at least two grooves with a reflect surface, and each sensing device is embedded in a groove;
• and
• an optical combiner, comprising an optical coupler, wherein the eye tracker is at least partially on the optical combiner along a front view of the head-mounted eye tracking system at a third arrangement direction perpendicular to a first arrangement direction and a second arrangement direction, the first arrangement direction is perpendicular to the second arrangement direction.