Color separation in planar waveguides using wavelength filters
View Patent ↗An eyepiece for projecting an image to an eye of a viewer includes a first planar waveguide positioned in a first lateral plane, a second planar waveguide positioned in a second lateral plane adjacent the first lateral plane, and a third planar waveguide positioned in a third lateral plane adjacent the second lateral plane. The first waveguide includes a first diffractive optical element (DOE) coupled thereto and disposed at a lateral position. The second waveguide includes a second DOE coupled thereto and disposed at the lateral position. The third waveguide includes a third DOE coupled thereto and disposed at the lateral position. The eyepiece further includes a first optical filter disposed between the first waveguide and the second waveguide at the lateral position, and a second optical filter positioned between the second waveguide and the third waveguide at the lateral position.
1. An eyepiece for projecting image light to an eye of a viewer, the image light including image light in a first wavelength range centered at a first wavelength and image light in a second wavelength range centered at a second wavelength different from the first wavelength, the eyepiece comprising:
a first planar waveguide including a first diffractive optical element (DOE) optically coupled thereto, wherein the first DOE is positioned along an optical path of the image light and configured to couple a portion of the image light in the first wavelength range into the first planar waveguide to be propagated in the first planar waveguide;
a first optical filter positioned along the optical path downstream from the first DOE, wherein the first optical filter is configured to attenuate the image light in the first wavelength range incident thereon;
a second planar waveguide including a second DOE optically coupled thereto, wherein the second DOE is positioned along the optical path downstream from the first optical filter and configured to couple a portion of the image light in the second wavelength range transmitted through the first optical filter into the second planar waveguide to be propagated in the second planar waveguide; and
a second optical filter coupled to the first planar waveguide, wherein the second optical filter is configured to absorb image light in the second wavelength range propagating in the first planar waveguide.
2. The eyepiece of claim 1 wherein the second wavelength is longer than the first wavelength, and the first optical filter comprises a long-pass filter configured to have a first transmittance value for the first wavelength range that is less than about 10% and a second transmittance value for the second wavelength range that is greater than about 90%.
3. The eyepiece of claim 2 wherein the second optical filter comprises a short-pass filter configured to have a first transmittance value for the second wavelength range that is less than about 10%, and a second transmittance value for the first wavelength range that is greater than about 90%.
4. The eyepiece of claim 2 wherein the first optical filter is configured to have the first transmittance value and the second transmittance value for angles of incidence ranging from about zero degrees to about 45 degrees.
5. The eyepiece of claim 2 wherein the first optical filter comprises a dichroic filter configured to reflect a portion of the image light in the first wavelength range toward the first planar waveguide.
6. The eyepiece of claim 1 wherein the second wavelength is shorter than the first wavelength, and the first optical filter comprises a short-pass filter configured to have a first transmittance value for the first wavelength range that is less than about 10% and a second transmittance value for the second wavelength range that is greater than about 90%.
7. The eyepiece of claim 6 wherein the second optical filter comprises a long-pass filter configured to have a first transmittance value for the second wavelength range that is less than about 10%, and a second transmittance value for the first wavelength range that is greater than about 90%.
8. The eyepiece of claim 1 wherein the second optical filter comprises:
a dichroic layer disposed on an outer surface of the first planar waveguide;
a terminating substrate disposed on the dichroic layer; and
an absorptive layer disposed on the terminating substrate.
9. The eyepiece of claim 1 wherein each of the first DOE and the second DOE comprises an incoupling grating.
10. The eyepiece of claim 1 further comprising an optical reflector positioned along the optical path downstream from the second planar waveguide.
11. A method for projecting image light to an eye of a viewer, the image light including image light in a first wavelength range centered at a first wavelength and image light in a second wavelength range centered at a second wavelength different from the first wavelength, the method comprising:
coupling, through a first diffractive optical element (DOE), a portion of the image light in the first wavelength range into a first planar waveguide, wherein the first DOE is positioned along an optical path of the image light in the first wavelength range and optically coupled to the first planar waveguide;
attenuating the image light in the first wavelength range through a first optical filter, wherein the first optical filter is positioned along the optical path downstream from the first DOE;
transmitting a portion of the image light in the second wavelength range through the first optical filter;
coupling, through a second DOE, the transmitted portion of the image light in the second wavelength range into a second planar waveguide, wherein the second DOE is positioned along the optical path of the image light in the second wavelength range downstream from the first optical filter and is optically coupled to the second planar waveguide; and
absorbing at least a portion of the image light in the second wavelength range propagating in the first planar waveguide by a second optical filter coupled to the first planar waveguide.
12. The method of claim 11 wherein the second wavelength is longer than the first wavelength, and the first optical filter comprises a long-pass filter configured to have a first transmittance value for the first wavelength range that is less than about 10% and a second transmittance value for the second wavelength range that is greater than about 90%.
13. The method of claim 12 wherein the second optical filter comprises a short-pass filter configured to have a first transmittance value for the second wavelength range that is less than about 10%, and a second transmittance value for the first wavelength range that is greater than about 90%.
14. The method of claim 12 wherein the first optical filter is configured to have the first transmittance value and the second transmittance value for angles of incidence ranging from about zero degrees to about 45 degrees.
15. The method of claim 12 wherein the first optical filter comprises a dichroic filter configured to reflect a portion of the image light in the first wavelength range toward the first planar waveguide.
16. The method of claim 11 wherein the second wavelength is shorter than the first wavelength, and the first optical filter comprises a short-pass filter configured to have a first transmittance value for the first wavelength range that is less than about 10% and a second transmittance value for the second wavelength range that is greater than about 90%.
17. The method of claim 16 wherein the second optical filter comprises a long-pass filter configured to have a first transmittance value for the second wavelength range that is less than about 10%, and a second transmittance value for the first wavelength range that is greater than about 90%.
18. The method of claim 11 wherein the second optical filter comprises:
a dichroic layer disposed on an outer surface of the first planar waveguide;
a terminating substrate disposed on the dichroic layer; and
an absorptive layer disposed on the terminating substrate.
19. The method of claim 11 wherein each of the first DOE and the second DOE comprises an incoupling grating.
20. The method of claim 11 further comprising reflecting image light in the second wavelength range transmitted through the second planar waveguide by an optical reflector positioned along the optical path downstream from the second planar waveguide.