Eye tracker based on retinal imaging via light-guide optical element

An apparatus for deriving a gaze direction of a human eye, the apparatus comprising;

• (a) a light-guide optical element (LOE) formed from transparent material and having pair of parallel faces for guiding light by internal reflection, one of said parallel faces being deployed in facing relation to the eye;
• (b) a coupling-in configuration associated with said LOE and configured for coupling-in a proportion of light incident on one of said parallel faces within a coupling-in region so as to propagate within said LOE;
• (c) focusing optics associated with said LOE and configured for converting sets of parallel light rays propagating within said LOE into converging beams of captured light;
• (d) an optical sensor deployed for sensing said captured light;
• and
• (e) a processing system including at least one processor, said processing system being electrically associated with said optical sensor and configured so as to process signals from said optical sensor to derive a current gaze direction of the eye,
• wherein said coupling-in configuration is configured to generate rays propagating within said LOE, each ray having a direction indicative of a direction of incidence of a corresponding incident light ray, and wherein a plurality of spaced-apart parallel incident rays are combined into a single ray propagating within said LOE,