Waveguide light multiplexer using crossed gratings
A two-dimensional waveguide light multiplexer is described herein that can efficiently multiplex and distribute a light signal in two dimensions. An example of a two-dimensional waveguide light multiplexer can include a waveguide, a first diffraction grating, and a second diffraction grating disposed above the first diffraction grating and arranged such that the grating direction of the first diffraction grating is perpendicular to the grating direction of the second diffraction grating. Methods of fabricating a two-dimensional waveguide light multiplexer are also disclosed.
1. A wearable display system comprising:
a frame;
a stack of waveguides coupled to the frame, wherein each waveguide of the stack of waveguides comprises:
an outcoupling optical element arranged to outcouple, from the waveguide, at least a portion of light that is propagating in the waveguide, the outcoupling optical element comprising:
one or more first diffraction gratings having a first grating direction, the one or more first diffraction gratings disposed on a first major surface of the waveguide; and
one or more second diffraction gratings having a second grating direction, wherein the one or more second diffraction gratings are disposed on the same waveguide as the one or more first diffraction gratings, on a second major surface of the waveguide that is opposite the first major surface, wherein the one or more second diffraction gratings are disposed over the one or more first diffraction gratings, and wherein the first grating direction is perpendicular to the second grating direction to cause the light propagating in the waveguide to be multiplexed in two perpendicular directions within the waveguide; and
an incoupling optical element arranged to incouple, into the waveguide, light that is incident on the incoupling optical element, the incoupling optical element positioned at a separate laterally displaced location on the waveguide from the outcoupling optical element; and
an image injection device comprising a light emitting diode (LED) and configured to direct image light having image content onto each of the incoupling optical elements such that at least a portion of the image light is incoupled into the respective waveguide and guided within the waveguide to the outcoupling optical element of the waveguide.
2. The display system of claim 1 , wherein the one or more first diffraction gratings are disposed on a bottom major surface of the waveguide and the one or more second diffraction gratings are disposed on a top major surface of the waveguide.
3. The display system of claim 1 , wherein the one or more first diffraction gratings and the one or more second diffraction gratings each comprise a symmetric diffraction grating.
4. The display system of claim 1 , wherein:
the one or more first diffraction gratings comprise at least one or more first asymmetric diffraction gratings having a first diffraction direction and at least one or more second asymmetric diffraction gratings having a second diffraction direction antiparallel to the first diffraction direction; and
the one or more second diffraction gratings comprise at least one or more third asymmetric diffraction gratings having a third diffraction direction and at least one or more fourth asymmetric diffraction gratings having a fourth diffraction direction antiparallel to the third diffraction direction.
5. The display system of claim 1 , wherein the one or more first and second diffraction gratings comprise a binary diffraction grating.
6. The display system of claim 1 , wherein the one or more first and second diffraction gratings comprise a blazed diffraction grating.
7. The display system of claim 1 , wherein the waveguide comprises top and bottom major surfaces, said waveguide having a thickness between said top and bottom major surfaces, said waveguide being wider and longer than said thickness, and wherein the at least one or more first diffraction gratings are disposed on one of the top or bottom major surfaces of the waveguide.
8. The display system of claim 7 , wherein the waveguide comprises an optically transparent portion, wherein the optically transparent portion is configured to transmit light from a portion of a physical environment in front of a user of the display system to an eye of the user to provide a view of the portion of the physical environment in front of the user.
9. The display system of claim 8 , wherein the outcoupling optical element is configured to outcouple the image light to the eye of the user from at least the optically transparent portion.
10. A waveguide comprising:
a substrate;
an outcoupling optical element on the substrate, the outcoupling optical element arranged to outcouple, from the waveguide, at least a portion of light that is propagating in the waveguide, the outcoupling optical element comprising:
one or more first diffraction gratings having a first grating direction, the one or more first diffraction gratings disposed on a first major surface of the waveguide; and
one or more second diffraction gratings having a second grating direction, wherein the one or more second diffraction gratings are disposed on a second major surface of the waveguide that is opposite the first major surface, wherein the one or more second diffraction gratings are disposed over the one or more first diffraction gratings, and wherein the first grating direction is perpendicular to the second grating direction to cause the light propagating in the waveguide to be multiplexed in two perpendicular directions within the waveguide; and
an incoupling optical element on the substrate, the incoupling optical element arranged to incouple, into the waveguide, light that is incident on the incoupling optical element such that at least a portion of the light is guided within the waveguide to the outcoupling optical element, the incoupling optical element positioned at a separate laterally displaced location on the waveguide from the outcoupling optical element.
11. The waveguide of claim 10 , wherein the one or more first diffraction gratings are disposed on a bottom major surface of the waveguide and the one or more second diffraction gratings are disposed on a top major surface of the waveguide.
12. The waveguide of claim 10 , wherein the one or more first diffraction gratings and the one or more second diffraction gratings each comprise a symmetric diffraction grating.
13. The waveguide of claim 10 , wherein:
the one or more first diffraction gratings comprise at least one or more first asymmetric diffraction gratings having a first diffraction direction and at least one or more second asymmetric diffraction gratings having a second diffraction direction antiparallel to the first diffraction direction; and
the one or more second diffraction gratings comprise at least one or more third asymmetric diffraction gratings having a third diffraction direction and at least one or more fourth asymmetric diffraction gratings having a fourth diffraction direction antiparallel to the third diffraction direction.
14. The waveguide of claim 10 , wherein the one or more first and second diffraction gratings comprise a binary diffraction grating.
15. The waveguide of claim 10 , wherein the one or more first and second diffraction gratings comprise a blazed diffraction grating.
16. The waveguide of claim 10 , wherein the substrate comprises an optically transparent portion.
17. The waveguide of claim 16 , wherein the outcoupling optical element is configured to outcouple the light from at least the optically transparent portion.