Method and system for tracking eye movement in conjunction with a light scanning projector
An eye tracking system includes a pair of glasses including two frames; a light scanning projector coupled to the pair of glasses and operable to scan a beam of light to project an image frame including a plurality of pixels; an eyepiece mounted in one of the two frames and optically coupled to the light scanning projector; one or more photodetectors coupled to one of the two frames and operable to detect time-varying reflected signals; and a processor coupled to the light scanning projector and the photodetectors. The eyepiece includes an exit pupil expander operable to direct a portion of the beam of light towards an eye of a user. Each of the time-varying reflected signals is associated with the plurality of pixels. The processor is operable to correlate the time-varying reflected signals with the plurality of pixels and determine a first eye orientation.
1. An eye tracking system comprising:
a pair of glasses including two frames;
a light scanning projector coupled to the pair of glasses and operable to scan a beam of light to project a first portion of an image frame including a first series of pixels and a second portion of the image frame including a second series of pixels;
an eyepiece mounted in one of the two frames and optically coupled to the light scanning projector, the eyepiece including an exit pupil expander operable to direct at least a portion of the beam of light towards an eye of a user;
one or more photodetectors coupled to at least one of the two frames of the pair of glasses and operable to detect a first set of time-varying reflected signals associated with the first series of pixels and a second set of time-varying reflected signals associated with the second series of pixels; and
a processor coupled to the light scanning projector and the one or more photodetectors, wherein the processor is operable to determine an eye orientation based on a correlation between the first set of time-varying reflected signals and the first series of pixels and a correlation between the second set of time-varying reflected signals and the second series of pixels.
2. The eye tracking system of claim 1 wherein the light scanning projector comprises a fiber scanning projector configured to scan in a spiral pattern with an increasing angular deflection as a function of time during the image frame.
3. The eye tracking system of claim 1 wherein the pair of glasses include a temple, wherein the light scanning projector is mounted in the one of the two frames and the one or more photodetectors are mounted in the temple.
4. The eye tracking system of claim 3 wherein the one or more photodetectors are mounted in the temple at a longitudinal position between the eyepiece and the eye of the user.
5. The eye tracking system of claim 1 wherein the eyepiece comprises a plurality of planar waveguides.
6. The eye tracking system of claim 1 , wherein the light scanning projector is operable to output a display signal and a characterization signal.
7. The eye tracking system of claim 6 , wherein the display signal comprises one or more visible wavelengths and the characterization signal comprises one or more non-visible wavelengths.
8. The eye tracking system of claim 1 , wherein the eyepiece comprises a diffractive structure operable to diffract the one or more time-varying reflected signals to the one or more photodetectors.
9. The eye tracking system of claim 8 , wherein the one or more photodetectors are disposed in front of the eyepiece.
10. The eye tracking system of claim 1 , wherein the eyepiece comprises a diffractive reflector operable to reflect through diffraction the one or more time-varying reflected signals to the one or more photodetectors.
11. The eye tracking system of claim 10 , wherein the one or more photodetectors are disposed at a longitudinal position between the eyepiece and the eye.
12. A method of performing eye tracking, the method comprising:
providing a light scanning projector, an eyepiece mounted in a frame, and a plurality of optical detectors arrayed around a periphery of the frame;
scanning a beam of the light scanning projector to form a first portion of an image frame, wherein the first portion of the image frame comprises a first series of pixels;
coupling the first portion of the image frame into the eyepiece;
transmitting at least a portion of the first portion of the image frame to an eye of a user;
detecting, at each of a plurality of optical detectors, a first set of time-varying reflected signals, wherein each of the first set of time-varying reflected signals is associated with the first series of pixels;
correlating the first set of time-varying reflected signals with the first series of pixels;
scanning the beam to form a second portion of the image frame, wherein the second portion of the image frame comprises a second series of pixels;
coupling the second portion of the image frame into the eyepiece;
transmitting at least a portion of the second portion of the image frame to the eye of the user;
detecting, at each of the plurality of optical detectors, a second set of time-varying reflected signals, wherein each of the second set of time-varying reflected signals is associated with the second series of pixels;
correlating the second set of time-varying reflected signals with the second series of pixels; and
determining an eye orientation based on correlating the first set of time-varying reflected signals with the first series of pixels and correlating the second set of time-varying reflected signals with the second series of pixels.
13. The method of claim 12 wherein the plurality of optical detectors are disposed at a longitudinal position between the eyepiece and the eye.
14. The method of claim 13 wherein the plurality of optical detectors are mounted in a temple mechanically coupled to the frame.
15. The method of claim 12 further comprising outputting a track related to the eye orientation.
16. The method of claim 12 wherein the first set of time-varying reflected signals are associated with increasing scan angle of the light scanning projector during the first portion of the image frame.
17. The method of claim 12 wherein the second set of time-varying reflected signals are associated with increasing scan angle of the light scanning projector during the second portion of the image frame.
18. The method of claim 12 wherein the eyepiece includes a plurality of planar waveguides, and wherein projecting the first portion of the image frame to the eye comprises:
coupling portions of the first portion of the image frame into each of the plurality of planar waveguides; and
transmitting at least a portion of the coupled portions to the eye.
19. The method of claim 12 wherein the eyepiece includes a plurality of planar waveguides, and wherein projecting the second portion of the image frame to the eye comprises:
coupling portions of the second portion of the image frame into each of the plurality of planar waveguides; and
transmitting at least a portion of the coupled portions to the eye.
20. The method of claim 12 wherein the light scanning projector comprises a fiber scanning projector configured to scan in a spiral pattern with an increasing angular deflection as a function of time during the image frame.