Infrared light suppression in eye-tracking imaging
A near-eye optical element, according to aspects herein, includes an illumination layer, an optical combiner layer, and an infrared absorber layer. The illumination layer includes infrared light sources configured to direct narrow-band infrared illumination light to an eyeward side of the near-eye optical element for eye tracking. The optical combiner layer is configured to receive reflected infrared light of the narrow-band infrared illumination light that is reflected off an eye of a user and to direct the reflected infrared light to a camera to generate an eye-tracking image. The infrared absorber layer is disposed between the optical combiner layer and a backside of the near-eye optical element to absorb infrared interference light of the narrow-band.
1. An optical system, comprising:
an illumination layer that includes at least one in-field infrared light source configured to direct narrow-band infrared illumination light to an eyeward side of the optical system for eye-tracking;
a camera configured to capture eye-tracking images of an eye of a user;
an optical combiner disposed between the at least one in-field infrared light source and a backside of the optical system, wherein the optical combiner is configured to receive reflected infrared light of the narrow-band infrared illumination light that is reflected off the eye of the user and to direct the reflected infrared light to the camera to generate the eye-tracking images; and
an infrared absorber disposed between the optical combiner and the backside of the optical system, wherein the infrared absorber is configured to absorb infrared interference light of the narrow-band.
2. The optical system of claim 1 , wherein the infrared interference light comprises reflected infrared light that propagates through the optical combiner to the infrared absorber.
3. The optical system of claim 1 , wherein the infrared interference light comprises external infrared light received from the backside of the optical system.
4. The optical system of claim 1 , wherein the infrared absorber is transmissive to visible light.
5. The optical system of claim 1 , further comprising:
a display layer disposed between the infrared absorber and the backside of the optical system, the display layer configured to provide display light that propagates through the infrared absorber and the optical combiner to the eyeward side of the optical system.
6. The optical system of claim 1 , wherein:
the at least one in-field infrared light source is configured to emit the narrow-band infrared illumination light that is centered around an infrared wavelength;
the camera includes an infrared bandpass filter having a center wavelength corresponding to the infrared wavelength to pass the reflected infrared light; and
the infrared absorber includes a peak absorptivity at a wavelength corresponding to the infrared wavelength of the narrow-band infrared illumination light.
7. The optical system of claim 6 , wherein the infrared wavelength is 940 nm.
8. The optical system of claim 1 , wherein the infrared absorber comprises a paint applied to a surface of the optical combiner.
9. The optical system of claim 1 , wherein the infrared absorber comprises an optical film disposed on a surface of the optical combiner.
10. A near-eye optical element, comprising:
an illumination layer including a plurality of infrared light sources configured to direct narrow-band infrared illumination light to an eyeward side of the near-eye optical element for eye tracking;
an optical combiner layer disposed between the illumination layer and a backside of the near-eye optical element, the optical combiner layer configured to receive reflected infrared light of the narrow-band infrared illumination light that reflects off an eye of a user and to direct the reflected infrared light to a camera to generate an eye-tracking image; and
an infrared absorber layer disposed between the optical combiner layer and the backside of the near-eye optical element, wherein the infrared absorber layer is configured to absorb infrared interference light of the narrow-band.
11. The near-eye optical element of claim 10 , wherein the infrared interference light comprises reflected infrared light that propagates through the optical combiner layer to the infrared absorber layer.
12. The near-eye optical element of claim 11 , wherein the infrared interference light comprises reflected infrared light that propagates through the illumination layer and through the optical combiner layer to the infrared absorber layer.
13. The near-eye optical element of claim 10 , wherein the infrared interference light comprises external infrared light received at the backside of the near-eye optical element.
14. The near-eye optical element of claim 10 , wherein the infrared absorber layer is transmissive to visible light.
15. The near-eye optical element of claim 10 , further comprising:
a display layer disposed between the infrared absorber layer and the backside of the near-eye optical element, the display layer configured to provide display light that propagates through the infrared absorber layer and the optical combiner layer to the eyeward side of the near-eye optical element.
16. The near-eye optical element of claim 10 , wherein the infrared light sources are configured to emit the narrow-band infrared illumination light that is centered around 940 nm.
17. The near-eye optical element of claim 10 , wherein the infrared absorber layer comprises a paint applied to a surface of the optical combiner layer or an optical film disposed on the surface of the optical combiner layer.
18. A head-mounted device, comprising:
a camera configured to generate eye-tracking images in response to reflected infrared light that is reflected off an eye of a user of the head-mounted device;
a near-eye optical element that includes:
an illumination layer including a plurality of in-field infrared light sources configured to generate narrow-band infrared illumination light to illuminate the eye of the user;
an optical combiner layer disposed between the illumination layer and a backside of the near-eye optical element, wherein the optical combiner layer is configured to receive the reflected infrared light of the narrow-band infrared illumination light reflected off the eye of the user and to direct the reflected infrared light to the camera; and
an infrared absorber layer disposed between the optical combiner layer and the backside of the near-eye optical element, wherein the infrared absorber layer is configured to absorb infrared interference light of the narrow-band.
19. The head-mounted device of claim 18 , wherein the infrared interference light comprises at least one of: reflected infrared light that propagates through the optical combiner layer to the infrared absorber layer, or external infrared light received at the backside of the near-eye optical element.
20. The head-mounted device of claim 18 , wherein:
the infrared illumination light has a wavelength of 940 nm;
the camera includes an infrared bandpass filter to pass the reflected infrared light having the wavelength of 940 nm; and
the infrared absorber layer is configured to absorb the infrared interference light having the wavelength of 940 nm.