Eye-tracking device and display apparatus including the same
Provided are an eye-tracking device that may rapidly and accurately track an observer's eye and may be made compact, and a display apparatus including the eye-tracking device. The eye-tracking device includes: a light source configured to emit an illumination light; a light guide plate configured to transmit the illumination light emitted from the light source to an observer's eye and transmit the illumination light reflected from the observer's eye in a direction opposite to a propagation direction of the illumination light emitted from the light source; a photodetector array configured to detect the illumination light reflected from the observer's eye; and a signal processor configured to determine an angle of rotation of the observer's eye based on a two-dimensional (2D) intensity distribution of the illumination light detected by the photodetector array.
1. An eye-tracking device comprising:
a light source configured to emit an illumination light;
a light guide plate configured to transmit the illumination light emitted from the light source to an observer's eye and transmit the illumination light reflected from the observer's eye in a direction opposite to a propagation direction of the illumination light emitted from the light source;
a photodetector array configured to detect the illumination light reflected from the observer's eye, the photodetector array comprising a plurality of two-dimensionally arranged photodiodes; and
a signal processor configured to determine a displacement of the observer's eye based on a two-dimensional (2D) intensity distribution of the illumination light incident on the plurality of photodiodes,
wherein the light guide plate comprises:
a first input/output coupler and a second input/output coupler configured to guide the illumination light to be incident into the light guide plate, to travel inside the light guide plate, and to travel outside the light guide plate;
an input coupler facing the first input/output coupler, the input coupler being configured to guide visible light into the light guide plate; and
an output coupler facing the second input/output coupler, the output coupler being configured to output the visible light traveling inside the light guide plate to an outside of the light guide plate,
wherein the eye-tracking device further comprises:
a wavelength selective mirror facing the input coupler and the first input/output coupler and configured to combine the illumination light emitted from the light source with an image formed by an image forming device and cause a combination of the illumination light and the image to propagate through a same optical path; and
a beam splitter disposed between the wavelength selective mirror and the light guide plate and configured to transmit the illumination light emitted from the light source to the first input/output coupler and transmit the illumination light received from the first input/output coupler to the photodetector array.
2. The eye-tracking device of claim 1 , wherein the light source faces a first surface of the beam splitter, and the photodetector array faces a second surface of the beam splitter, and
wherein the first surface of the beam splitter is disposed to oppose the second surface of the beam splitter.
3. The eye-tracking device of claim 1 , wherein the beam splitter comprises a half mirror configured to reflect a first half of the illumination light and transmit a second half of the illumination light.
4. The eye-tracking device of claim 1 , wherein the beam splitter comprises a polarizing beam splitter configured to reflect the illumination light having a first linear polarization component and configured to transmit the illumination light having a second linear polarization component perpendicular to the first linear polarization component.
5. The eye-tracking device of claim 2 , further comprising a quarter-wave plate disposed between the beam splitter and the light guide plate.
6. The eye-tracking device of claim 1 , further comprising a varifocal lens disposed between the beam splitter and the light guide plate and configured to change a focal length according to a distance between the second input/output coupler and the observer's eye.
7. The eye-tracking device of claim 1 , wherein the light guide plate comprises a first surface and a second surface facing the first surface,
wherein the light source and the photodetector array face the first surface of the light guide plate, and the first input/output coupler and the second input/output coupler are disposed on the second surface of the light guide plate.
8. The eye-tracking device of claim 1 , wherein the light guide plate comprises a first surface and a second surface facing the first surface,
wherein the light source and the photodetector array face the first surface of the light guide plate, and the first input/output coupler and the second input/output coupler are disposed on the first surface of the light guide plate.
9. The eye-tracking device of claim 1 , wherein the second input/output coupler comprises a holographic optical element having a positive refractive power to focus the illumination light, which is output from the light guide plate and passes through the pupil of the observer's eye, on a center of the observer's eye.
10. The eye-tracking device of claim 1 , wherein the light source comprises an infrared light source configured to emit an infrared light as the illumination light.
11. The eye-tracking device of claim 1 , wherein the photodetector array comprises a plurality of infrared detectors that are arranged in a two-dimensional (2D) manner.
12. The eye-tracking device of claim 1 , wherein the light guide plate has a curved shape.
13. A display apparatus comprising:
an image forming device configured to form an image;
an eye-tracking device configured to track an observer's eye and comprising:
an infrared light source configured to emit an infrared illumination light;
a photodetector array comprising a plurality of infrared photodiodes that are arranged in a two-dimensional (2D) manner;
a light guide plate configured to transmit the infrared illumination light emitted from the infrared light source to the observer's eye and transmit the infrared illumination light reflected from the observer's eye to the photodetector array; and
a signal processor configured to determine a displacement of the observer's eye based on a 2D intensity distribution of the infrared illumination light incident on the plurality of infrared photodiodes; and
an image shifter configured to move the image according to an angle of rotation of the observer's eye,
wherein the light guide plate comprises:
a first input/output coupler and a second input/output coupler configured to guide the infrared illumination light to be incident into the light guide plate, to travel inside the light guide plate, and to travel outside the light guide plate;
an input coupler facing the first input/output coupler, the input coupler being configured to guide visible light into the light guide plate; and
an output coupler facing the second input/output coupler, the output coupler being configured to output the visible light traveling inside the light guide plate to an outside of the light guide plate,
wherein the display apparatus further comprises:
a wavelength selective mirror facing the input coupler and the first input/output coupler and configured to combine the infrared illumination light emitted from the infrared light source with the image formed by the image forming device and cause a combination of the infrared illumination light and the image to propagate through a same optical path; and
a beam splitter disposed between the wavelength selective mirror and the light guide plate and configured to transmit the infrared illumination light emitted from the infrared light source to the first input/output coupler and transmit the infrared illumination light received from the first input/output coupler to the photodetector array.
14. The display apparatus of claim 13 , wherein the image forming device comprises:
a visible light source configured to emit the visible light; and
a spatial light modulator configured to modulate the visible light emitted from the visible light source and generate the image.
15. The display apparatus of claim 13 , wherein the light guide plate comprises a first surface and a second surface facing the first surface,
wherein the input coupler and the output coupler are disposed on the first surface of the light guide plate, and
the first input/output coupler is disposed on the second surface of the light guide plate to face the input coupler, and the second input/output coupler is disposed on the second surface of the light guide plate to face the output coupler.
16. The display apparatus of claim 13 , wherein the infrared light source faces a first surface of the beam splitter and the photodetector array faces a second surface of the beam splitter.
17. The display apparatus of claim 13 , wherein the beam splitter is configured to reflect a first half of the infrared illumination light, transmit a second half of the infrared illumination light, and transmit the visible light.
18. The display apparatus of claim 13 , wherein the beam splitter is configured to reflect the infrared illumination light having a first linear polarization component, transmit the infrared illumination light having a second linear polarization component perpendicular to the first linear polarization component, and transmit the visible light,
wherein the display apparatus further comprises a quarter-wave plate disposed between the beam splitter and the light guide plate.
19. The display apparatus of claim 13 , further comprising a varifocal lens disposed between the beam splitter and the light guide plate and configured to change a focal length according to a distance between the second input/output coupler and the observer's eye.
20. The display apparatus of claim 13 , wherein the second input/output coupler comprises a holographic optical element having a positive refractive power to focus the infrared illumination light, which is output from the light guide plate and passes through a pupil of the observer's eye, on a center of the observer's eye.
21. The display apparatus of claim 13 , wherein the display apparatus includes a virtual reality (VR) display apparatus, an augmented reality (AR) display apparatus, a mixed reality (MR) display apparatus that is a head mounted display, a glasses-type display, or a goggle-type display.