Holographic eye imaging device
An eye tracking device for tracking an eye is described. The eye tracking device comprises: a first diffractive optical element, DOE, arranged in front of the eye, an image module, wherein the image module is configured to capture an image of the eye via the first DOE. The first DOE is adapted to direct a first portion of incident light reflected from the eye, towards the image module. The eye tracking device is characterized in that the first DOE is configured to provide a lens effect.
1. An eye tracking device for tracking an eye, comprising:
a first diffractive optical element, DOE, arranged in front of the eye,
a second DOE adjacent to the first DOE, wherein the first DOE and the second DOE are positioned side by side, seen from the eye, wherein at least one DOE is arranged on a support structure,
an image module, wherein the image module is configured to capture an image of the eye via the first DOE, wherein the image module is placed on a same side of the support structure as the eye,
wherein the first DOE is adapted to direct a first portion of incident light reflected from the eye towards the image module and the second DOE is adapted to direct a second portion of incident light reflected from the eye towards the image module,
characterized in that the first DOE is configured to provide a lens effect.
2. The eye tracking device according to claim 1 , wherein a focal length of the first DOE is adapted to direct the first portion of incident light so as to give a sharp image of the eye in the image module.
3. The eye tracking device according to claim 2 , wherein the second DOE is configured to provide a lens effect, wherein a focal length of the second DOE is adapted to direct the second portion of incident light so as to give a sharp image of the eye in the image module, and wherein the focal length of the second DOE is different from the focal length of the first DOE.
4. The eye tracking device according to claim 1 , wherein the at least one DOE is part of the support structure.
5. The eye tracking device according to claim 1 , wherein the support structure is transparent and comprises a polymer or silver halide.
6. The eye tracking device according to claim 1 , wherein the support structure has a thickness in the interval of 2-1000 μm, preferably 2-200 μm, more preferably 10-100 μm.
7. The eye tracking device according to claim 1 , wherein a viewing plane is arranged in the vicinity or in contact with the at least one DOE.
8. The eye tracking device according to claim 1 , comprising at least one illuminator configured to produce the incident light, the incident light being within a wavelength range of 650-3000 nm, preferably within a wavelength range of 700-1500 urn and most preferably within a wavelength range of 800-1000 nm.
9. The eye tracking device according to claim 8 , wherein the first portion of incident light has a first wavelength and the second portion of incident light has a second wavelength, and wherein the at least one illuminator comprises a first illuminator configured to emit light at the first wavelength and a second illuminator configured to emit light at the second wavelength being different from the first wavelength.
10. The eye tracking device according to claim 9 , wherein one of the first wavelength and the second wavelength is in the range 840-860 nm, and the other wavelength is in the range 930-950 nm.
11. The eye tracking device according to claim 1 , wherein the at least one DOE is any of:
a holographic optical element, such as a volumetric reflection hologram produced by interfering two or more beams or a computer-generated hologram;
binary optics made by staircases that approximate the ideal surface relief;
a hybrid lens with combined refractive and diffractive power; or
a Fresnel zone plate.
12. The eye tracking device according to claim 1 , also comprising a control unit adapted to receive an image captured by the image module, and calculate a viewing angle of the eye.
13. The eye tracking device according to claim 1 , wherein the eye tracking device is a head-worn device.
14. The eye tracking device according to claim 13 , wherein the head-worn device is one of:
glasses for eye-tracking;
an augmented reality headset, wherein a transparent viewing plane is either integrated into the DOE, attached to the DOE or arranged in the vicinity of the DOE; or
a virtual reality headset, comprising a viewing plane, wherein the DOE is either integrated into the viewing plane, attached in front of the viewing plane or arranged in front of the viewing plane.