Beam walking detection for eye tracking in a head-mounted device

A head-mounted device comprising:

• a frame configured to be worn about a head of a user;
• a lens assembly carried by the frame;
• and
• an eye tracking system comprising:
• a detector array positioned on the head-mounted device to receive reflected light from an eyebox region of the head-mounted device;
• a scanning mirror optically coupled between the eyebox region and the detector array, wherein the scanning mirror is configured to rotate to direct the reflected light from a plurality of locations within the eyebox region to the detector array;
• a light source configured to provide pulses of light to illuminate at least part of the eyebox region;
• and
• processing logic coupled to the detector array and configured to receive light detection data, wherein the processing logic is configured to determine an orientation or depth characteristic of an eye based at least partially on a travel duration of the pulses of light between the light source, the eyebox region, and the detector array.

A method of eye tracking with a head-mounted device comprising:

• emitting pulses of light from a light source;
• rotating a scanning mirror at an eyebox scanning frequency within a range of scanning angles;
• directing, with the scanning mirror, the pulses of light from the light source towards an eye in an eyebox region;
• directing, with the scanning mirror, light reflections from the eye to a detector array, wherein the detector array includes a plurality of pixels;
• providing, with the detector array, light detection data that is representative of ones of the plurality of pixels that received light reflections in the detector array;
• and
• determining, with processing logic, depth characteristics of the eye based on the light detection data, wherein the depth characteristics are determined at least partially based on a travel duration of the pulses of light between the light source, the eyebox region, and the detector array.