Color separation in planar waveguides using an optical filter between two diffractive optical elements (DOE)
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 planar waveguide includes a first diffractive optical element (DOE) coupled thereto and disposed at a first lateral position. The second planar waveguide includes a second DOE coupled thereto and disposed at a second lateral position. The third planar waveguide includes a third DOE coupled thereto and disposed at the second lateral position. The eyepiece further includes an optical filter positioned between the second planar waveguide and the third planar waveguide at the second lateral position.
1. An eyepiece for projecting an image to an eye of a viewer, the eyepiece comprising:
a first planar waveguide positioned in a first lateral plane, wherein the first planar waveguide comprises a first diffractive optical element (DOE) coupled thereto and disposed at a first lateral position;
a second planar waveguide positioned in a second lateral plane adjacent the first lateral plane, wherein the second planar waveguide comprises a second DOE coupled thereto and disposed at a second lateral position;
a third planar waveguide positioned in a third lateral plane adjacent the second lateral plane, wherein the third planar waveguide comprises a third DOE coupled thereto and disposed at the second lateral position; and
an optical filter positioned between the second planar waveguide and the third planar waveguide at the second lateral position.
2. The eyepiece of claim 1 wherein each of the first DOE, the second DOE, and the third DOE comprises an incoupling grating.
3. The eyepiece of claim 1 wherein:
the second DOE is configured to diffract image light in a first wavelength range centered at a first wavelength;
the first DOE is configured to diffract image light in a second wavelength range centered at a second wavelength longer than the first wavelength;
the third DOE is configured to diffract image light in a third wavelength range centered at a third wavelength longer than the second wavelength; and
the optical filter is configured to have a first transmittance value at the first wavelength range and a second transmittance value at the third wavelength range that is greater than the first transmittance value.
4. The eyepiece of claim 3 wherein the first transmittance value is less than about 10%, and the second transmittance value is greater than about 90%.
5. The eyepiece of claim 4 wherein the optical filter is configured to have the first transmittance value and the second transmittance value for angles of incidence ranging from about zero degree to about 45 degrees.
6. The eyepiece of claim 1 wherein the first lateral position is laterally offset from the second lateral position.
7. The eyepiece of claim 6 further comprising a reflector positioned between the first planar waveguide and the second planar waveguide at the first lateral position.
8. The eyepiece of claim 7 wherein:
the first planar waveguide has a first surface and a second surface opposite the first surface, and the first DOE is coupled to the first surface of the first planar waveguide;
the second planar waveguide has a first surface and a second surface opposite the first surface, the first surface of the second planar waveguide faces the second surface of the first planar waveguide, and the second DOE is coupled to the first surface of the second planar waveguide; and
the third planar waveguide has a first surface and a second surface opposite the first surface, the first surface of the third planar waveguide faces the second surface of the second planar waveguide, and the third DOE is coupled to the first surface of the third planar waveguide.
9. The eyepiece of claim 8 wherein the reflector is attached to the second surface of the first planar waveguide.
10. The eyepiece of claim 8 wherein the optical filter is attached to the second surface of the second planar waveguide.
11. The eyepiece of claim 7 wherein:
the first planar waveguide has a first surface and a second surface opposite the first surface, and the first DOE is coupled to the second surface of the first planar waveguide;
the second planar waveguide has a first surface and a second surface opposite the first surface, the first surface of the second planar waveguide faces the second surface of the first planar waveguide, and the second DOE is coupled to the second surface of the second planar waveguide; and
the third planar waveguide has a first surface and a second surface opposite the first surface, the first surface of the third planar waveguide faces the second surface of the second planar waveguide, and the third DOE is coupled to the second surface of the third planar waveguide.
12. The eyepiece of claim 11 wherein the reflector is attached to the second surface of the first planar waveguide.
13. The eyepiece of claim 11 wherein the optical filter is attached to the second surface of the second planar waveguide.
14. The eyepiece of claim 11 wherein the optical filter is attached to the first surface of the third planar waveguide.
15. The eyepiece of claim 1 further comprising a reflector positioned in a fourth lateral plane adjacent the third lateral plane at the second lateral position.