US Patent 10983341 Eye tracking based on polarization volume grating

An eye-tracker for determining a position of the pupil of an eye includes a detector and an optical element. The optical element is configured to receive first light reflected off the eye and reflectively diffract a portion of the first light that has a first polarization toward the detector. The optical element is also configured to transmit second light. The second light includes a second portion of the first light that has a second polarization that is different from the first polarization. A head-mounted display device that includes a display system and the eye-tracker is also disclosed. A method for determining the location of a pupil of an eye is also disclosed herein.