Eye movement determination
A method for operating a display of a virtual reality or augmented reality headset includes determining a direction of movement of a user's eye, estimating a future gaze direction from the determined direction of movement, and rendering an image on the display having higher resolution image data in a region including the estimated gaze direction and lower resolution image data outside of the region including the determined gaze direction. The determining the direction of movement of the user's eye includes illuminating the user's eye with a beam of light emitted by a first laser, receiving, at the first laser, light redirected from the user's eye_such that self-mixing interference occurs within the laser cavity between light generated by the first laser and the light redirected from the user's eye, measuring the self-mixing interference, and determining a direction of movement of the user's eye-from the measured self-mixing interference.
1 . A method for operating a display of a virtual reality (VR) or augmented reality (AR) headset, the method comprising:
determining a direction of movement of a user's eye;
estimating a future gaze direction from the determined direction of movement; and
rendering an image on the display comprising higher resolution image data in a region comprising the estimated gaze direction and lower resolution image data outside of the region comprising the estimated gaze direction, wherein determining a direction of movement of the user's eye comprises:
illuminating the user's eye with a first pair of lasers, wherein the first pair of lasers comprises a first laser and a second laser,
wherein the first laser is configured to emit light in a first direction, and wherein the second laser is configured to emit light in a second direction, wherein the second direction is nonparallel to the first direction;
illuminating the user's eye with a second pair of lasers, wherein the second pair of lasers comprises a third laser and a fourth laser,
wherein the third laser is configured to emit light in a direction parallel to the first direction and wherein the fourth laser is configured to emit light in a direction parallel to the second direction;
receiving, at the first laser, light redirected from the user's eye, such that self- mixing interference occurs within a laser cavity between light generated by the first laser and the light redirected from the user's eye;
measuring the self-mixing interference; and
determining a direction of movement of the user's eye from the measured self-mixing interference.
2 . The method according to claim 1 , wherein illuminating the user's eye comprises illuminating only a sclera of the user's eye.
3 . The method according to claim 1 , wherein the method further comprises determining a speed of movement of the user's eye from the measured self-mixing interference.
4 . The method according to claim 1 , wherein determining the direction of movement of the user's eye from the self-mixing interference comprises determining the direction of movement of the user's eye from self-mixing interference caused by a Doppler shift of the redirected light due to movement of the user's eye.
5 . The method according to claim 4 , wherein determining the direction of movement of the user's eye from self-mixing interference caused by a Doppler shift of the redirected light due to movement of the user's eye comprises performing a Fourier transform on the measured self-mixing interference.
6 . The method according to claim 1 , wherein measuring the self-mixing interference comprises measuring a voltage or current of the first laser.
7 . A virtual reality (VR) or augmented reality (AR) headset comprising:
a frame for mounting to a user's head;
a device for determining eye movement integrated in or located on the frame, the device comprising:
a first laser configured to emit a beam of light for illuminating the user's eye when in use and to receive light redirected from the user's eye, such that self-mixing interference occurs within a laser cavity between light generated by the first laser and the light redirected from the user's eye;
a measurement apparatus configured to measure the self-mixing interference; and
a processing unit configured to determine a direction of movement of the user's eye from the measured self-mixing interference, wherein the processing unit is further configured to estimate a future gaze direction from the determined direction of movement of the user's eye; and
a display configured to render an image on the display comprising higher resolution image data in a display region in the determined future gaze direction and lower resolution image data outside of the display region in the determined future gaze direction;
a first pair of lasers each configured to emit a beam of light for illuminating the user's eye when in use,
wherein the first pair of lasers comprises the first laser and a second laser, and wherein the first laser is configured to emit light in a first direction, and wherein the second laser is configured to emit light in a second direction, wherein the second direction is nonparallel to the first direction; and
a second pair of lasers each configured to emit a beam of light for illuminating the user's eye when in use, wherein the second pair of lasers comprises a third laser and a fourth laser, wherein the third laser is configured to emit light in a direction parallel to the first direction and wherein the fourth laser is configured to emit light in a direction parallel to the second direction.
8 . The VR or AR headset according to claim 7 , wherein the first laser is configured to emit light towards only a sclera of the user's eye.
9 . The VR or AR headset according to claim 7 , wherein the processing unit is further configured to determine speed of movement of the user's eye from the measured self-mixing interference.
10 . The VR or AR headset according to claim 7 , wherein the processing unit is configured to determine the direction of movement of the user's eye from self-mixing interference caused by a Doppler shift of the redirected light due to movement of the user's eye.
11 . The VR or AR headset according to claim 7 , wherein the first laser comprises a vertical cavity surface emitting laser; and/or wherein the measurement apparatus comprises a sensor configured to measure a voltage input or current input of the first laser.
12 . The VR or AR headset according to claim 7 , wherein the measurement apparatus comprises a photodetector.
13 . The VR or AR headset according to claim 12 , wherein the processing unit is configured to determine a frequency modulation of light incident on the photodetector; and/or wherein the first laser comprises a vertical cavity surface emitting laser and wherein the photodetector is integrated with the vertical cavity surface emitting laser as single semiconductor device; and/or wherein the photodetector is spatially separated from the first laser and wherein the device further comprises an optical element configured to redirect at least a portion of the self-mixing interference towards the photodetector.
14 . The VR or AR headset according to claim 7 , wherein the first laser is configured to emit the beam of light such that an optical axis of the emitted beam of light forms an acute angle with respect to a surface of the user's eye.
15 . The VR or AR headset according to claim 7 , wherein the device is configured such that an offset of the emitted beam of light from the first laser relative to a first plane bisecting the center of the user's eye is equal to an offset of the emitted beam of light from the third laser relative to the first plane bisecting the center of the user's eye, and wherein the device is configured such that an offset of the emitted beam of light from the second laser relative to a second plane bisecting the center of the user's eye is equal to an offset of the emitted beam of light from the fourth laser relative to the second plane bisecting the center of the user's eye.
16 . The VR or AR headset according to claim 7 , wherein the third laser is configured to emit light in a third direction, wherein the third direction is different to the first direction, and wherein the fourth laser is configured to emit light in a fourth direction different to the second direction and non-parallel to the third direction.