Double-sided imaging light guide
An imaging light guide has waveguide for conveying image-bearing light beams from an image source to an eyebox within which a virtual image can be viewed. First and second in-coupling diffractive optics direct first and second sets of the image-bearing light beams into the waveguide along different first and second paths. First and second turning diffractive optics disposed along the respective paths expand the image-bearing light beams of the first and second sets in a first dimension and direct the expanded image-bearing light beams of the first and second sets to first and second out-coupling diffractive optics. The first and second out-coupling diffractive optics further expand the image-bearing light beams of the two sets in a second dimension and direct the further expanded image-bearing light beams of the two sets from the waveguide toward the eyebox.
1. An imaging light guide comprising:
a waveguide operable to convey image-bearing light beams from an image source to an eyebox within which a virtual image can be viewed;
a first in-coupling diffractive optic disposed to direct a first set of the image-bearing light beams into the waveguide along a first path;
a first turning diffractive optic disposed along the first path and arranged to expand the image-bearing light beams of the first set in a first dimension and to direct the expanded image-bearing light beams of the first set to a first out-coupling diffractive optic;
wherein the first out-coupling diffractive optic is arranged to further expand the image-bearing light beams of the first set in a second dimension and to direct the further expanded image-bearing light beams of the first set from the waveguide toward the eyebox;
a second in-coupling diffractive optic disposed to direct a second set of the image-bearing light beams into the waveguide along a second path that is different from the first path; and
a second turning diffractive optic disposed along the second path and arranged to expand the image-bearing light beams of the second set in a first dimension and to direct the expanded image-bearing light beams of the second set to a second out-coupling diffractive optic;
wherein the second out-coupling diffractive optic is arranged to further expand the image-bearing light beams of the second set in a second dimension and to direct the further expanded image-bearing light beams of the second set from the waveguide toward the eyebox;
wherein the first in-coupling diffractive optic has a corresponding first in-coupling grating vector and the second in-coupling diffractive optic has a corresponding second in-coupling grating vector; and the first in-coupling grating vector is oriented at an angle of 25 to 40 degrees relative to the second in-coupling grating vector.
2. The imaging light guide of claim 1 wherein the first out-coupling diffractive optic has a first out-coupling grating vector, the second out-coupling diffractive optic has a second out-coupling grating vector, and the first out-coupling grating vector is oriented away from the second out-coupling grating vector.
3. The imaging light guide of claim 2 wherein the first out-coupling grating vector is oriented away from the second out-coupling grating vector by 90 degrees.
4. The imaging light guide of claim 1 wherein the waveguide includes a substrate with parallel front and back surfaces, the first in-coupling diffractive optic and the second in-coupling diffractive optic are aligned along a common normal to the front and back surfaces of the substrate, and the first turning diffractive optic and the second turning diffractive optic are not aligned along a common normal to the front and back surfaces of the substrate.
5. The imaging light guide of claim 3 wherein the waveguide includes a substrate with parallel front and back surfaces, the first out-coupling diffractive optic and the second out-coupling diffractive optic are aligned along a common normal to the front and back surfaces of the substrate, and the first turning diffractive optic and the second turning diffractive optic are not aligned along a common normal to the front and back surfaces of the substrate.
6. The imaging light guide of claim 1 wherein the first in-coupling diffractive optic is a volume hologram.
7. The imaging light guide of claim 1 wherein the first in-coupling diffractive optic is a diffraction grating.
8. The imaging light guide of claim 1 in which the waveguide includes a planar substrate.
9. The imaging light guide of claim 1 wherein the first set of image-bearing light beams comprises a first range of wavelengths and the second set of image-bearing light beams comprises a second range of wavelengths that differs from the first range of wavelengths.
10. The imaging light guide of claim 1 wherein the first set of image-bearing light beams comprises a first range of angularly related beams and the second set of image-bearing light beams comprises a second range of angularly related beams that differs from the first range of angularly related beams.
11. The imaging light guide of claim 1 wherein the first in-coupling grating vector is oriented away from the second in-coupling grating vector by 30 degrees.
12. An imaging light guide comprising:
a waveguide operable to convey image-bearing light beams from an image source to an eyebox within which a virtual image can be viewed;
a first in-coupling diffractive optic disposed to direct a first set of the image-bearing light beams into the waveguide along a first path;
a first turning diffractive optic disposed along the first path and arranged to expand the image-bearing light beams of the first set in a first dimension and to direct the expanded image-bearing light beams of the first set to a first out-coupling diffractive optic;
the first out-coupling diffractive optic arranged to further expand the image-bearing light beams of the first set in a second dimension and to direct the further expanded image-bearing light beams of the first set from the waveguide toward the eyebox;
a second in-coupling diffractive optic disposed to direct a second set of the image-bearing light beams into the waveguide along a second path that is different from the first path;
a second turning diffractive optic disposed along the second path and arranged to expand the image-bearing light beams of the second set in a first dimension and to direct the expanded image-bearing light beams of the second set to a second out-coupling diffractive optic; and
the second out-coupling diffractive optic being arranged to further expand the image-bearing light beams of the second set in a second dimension and to direct the further expanded image-bearing light beams of the second set from the waveguide toward the eyebox;
wherein the first out-coupling diffractive optic has a first out-coupling grating vector, the second out-coupling diffractive optic has a second out-coupling grating vector, and the first out-coupling grating vector is oriented at an angle of 25 to 40 degrees relative to the second out-coupling grating vector.
13. The imaging light guide of claim 12 wherein the first in-coupling diffractive optic has a first in-coupling grating vector, the second in-coupling diffractive optic has a second in-coupling grating vector, and the first in-coupling grating vector is oriented away from the second in-coupling grating vector.
14. The imaging light guide of claim 13 wherein the first in-coupling grating vector is oriented away from the second in-coupling grating vector by 90 degrees.
15. The imaging light guide of claim 12 wherein:
the waveguide includes a substrate with parallel front and back surfaces,
the first in-coupling diffractive optic and the second in-coupling diffractive optic are aligned along a first common normal to the front and back surfaces of the substrate,
the first turning diffractive optic and the second turning diffractive optic are not aligned along a common normal to the front and back surfaces of the substrate, and
the first out-coupling diffractive optic and the second out-coupling diffractive optic are aligned along a second common normal to the front and back surfaces of the substrate.