Color separation in planar waveguides using dichroic 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 an image to an eye of a viewer, the eyepiece comprising:
a first planar waveguide positioned in a first lateral plane, wherein the first waveguide comprises a first diffractive optical element (DOE) coupled thereto and disposed at a lateral position, the first DOE configured to diffract image light in a first wavelength range centered at a first wavelength;
a second planar waveguide positioned in a second lateral plane adjacent the first lateral plane, wherein the second waveguide comprises a second DOE coupled thereto and disposed at the lateral position, the second DOE configured to diffract image light in a second wavelength range centered at a second wavelength longer than the first wavelength;
a third planar waveguide positioned in a third lateral plane adjacent the second lateral plane, wherein the third waveguide comprises a third DOE coupled thereto and disposed at the lateral position, the third DOE configured to diffract image light in a third wavelength range centered at a third wavelength longer than the second wavelength;
a first optical filter disposed between the first waveguide and the second waveguide at the lateral position, wherein the first optical filter is configured to have:
a first transmittance value at the first wavelength range;
a second transmittance value at the second wavelength range and the third wavelength range that is greater than the first transmittance value; and
a first reflectance value at the first wavelength range that is greater than about 90%; and
a second optical filter positioned between the second waveguide and the third waveguide at the lateral position, wherein the second optical filter is configured to have:
a third transmittance value at the first wavelength range and the second wavelength range;
a fourth transmittance value at the third wavelength range that is greater than the third transmittance value; and
a second reflectance value at the second wavelength range that is greater than about 90%.
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 each of the first transmittance value and the third transmittance value is less than about 10%, and each of the second transmittance value and the fourth transmittance value is greater than about 90%.
4. The eyepiece of claim 3 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 degree to about 45 degrees, and the second optical filter is configured to have the third transmittance value and the fourth transmittance value for angles of incidence ranging from about zero degree to about 45 degrees.
5. The eyepiece of claim 1 wherein the first wavelength range is centered substantially at 462 nm, the second wavelength range is centered substantially at 528 nm, and the third wavelength range is centered substantially at 635 nm.
6. The eyepiece of claim 1 further comprising an optical reflector positioned in a sixth lateral plane adjacent the fifth lateral plane at the lateral position and configured to reflect image light transmitted through the third waveguide.
7. The eyepiece of claim 1 further comprising:
a first short-pass filter optically coupled to the second lateral region of the first waveguide and configured to absorb image light in the second wavelength range; and
a second short-pass filter optically coupled to the second lateral region of the second waveguide and configured to absorb image light in the third wavelength range.
8. The eyepiece of claim 7 wherein the first short-pass filter is disposed inside the second lateral region of the first waveguide, and the second short-pass filter is disposed inside the second lateral region of the second waveguide.
9. The eyepiece of claim 7 wherein the first short-pass filter is disposed in a cavity inside the second lateral region of the first waveguide, and the second short-pass filter is disposed in a cavity inside the second lateral region of the second waveguide.
10. The eyepiece of claim 7 wherein the first short-pass filter is disposed on the first lateral surface of the second lateral region of the first waveguide, and the second short-pass filter is disposed on the first lateral surface of the second lateral region of the second waveguide.