SLANTED BURIED DIFFRACTIVE GRATINGS FOR OPTICAL ELEMENTS OF AUGMENTED REALITY AND VIRTUAL REALITY DISPLAYS
Head-mounted displays (HMD) or other suitable optical equipment with waveguides comprising one or more slanted buried diffractive gratings and methods for fabricating said waveguides are described herein. In an embodiment, an HMD comprises an optical element and an image source that provides an image beam to the optical element. The optical element may comprise a first flat surface, a second flat surface, and a buried diffractive grating disposed between the first surface and the second surface. The buried diffractive grating may be positioned in a slanted arrangement at a particular angle relative to the first flat surface and the second flat surface.
1 . (canceled)
2 . A display comprising:
an image source configured to provide an image beam; and
an optical element comprising a flat first surface, a flat second surface opposing the flat first surface, a first buried diffractive grating disposed between the flat first surface and the flat second surface, and a second buried diffractive grating disposed between the first flat surface and the flat second surface, the first buried diffractive grating being positioned in a slanted arrangement at a first angle relative to the flat first surface and the flat second surface, and the second buried diffractive grating being positioned in a slanted arrangement at a second angle relative to the flat first surface and the flat second surface;
wherein the first buried diffractive grating is positioned at a first depth within the optical element and the second buried diffractive grating is positioned at a second depth, different from the first depth, within the optical element; and
wherein the optical element is configured to convert the image beam into an output image by diffracting the beam through the first buried diffractive grating, the second buried diffractive grating, and propagating the image beam through the optical element.
3 . The display of claim 2 , wherein the optical element further comprises a third buried diffractive grating having a non-slanted arrangement.
4 . The display of claim 2 , wherein the optical element further comprises:
an in-coupling diffractive grating disposed on the flat first surface and configured to diffract the image beam into the optical element; and
an out-coupling diffractive grating disposed on the flat second surface and configured to diffract the image beam out of the optical element.
5 . The display of claim 4 , wherein the in-coupling diffractive grating is the first buried diffractive grating, and the out-coupling diffractive grating is the second buried diffractive grating.
6 . The display of claim 2 , wherein the first angle and the second angle are the same.
7 . The display of claim 2 , wherein the first angle and the second angle are different.
8 . The display of claim 2 , wherein a size of the second buried diffractive gating is smaller than a size of the first buried diffractive grating.
9 . The display of claim 2 , wherein the first buried diffractive grating is spaced closer to the first surface than the second buried diffractive grating.
10 . The display of claim 2 , wherein a refractive index of the first buried diffractive grating is the same as a refractive index of the second buried diffractive grating.
11 . The display of claim 2 , wherein a refractive index of the first buried diffractive grating is the different from a refractive index of the second buried diffractive grating.
12 . A method for producing a waveguide for a display comprising:
fabricating an optical element comprising:
a first buried diffractive grating positioned in a slanted arrangement at a first angle relative to a first flat surface and a second flat surface of the optical element; and
a second buried diffractive grating positioned in a slanted arrangement at a second angle relative to the first flat surface and the second flat surface of the optical element;
wherein the first buried diffractive grating is positioned at a first depth within the optical element and the second buried diffractive grating is positioned at a second depth, different from the first depth, within the optical element.
13 . The method of claim 12 , wherein the optical element is further fabricated to comprise a third buried diffractive grating having a non-slanted arrangement.
14 . The method of claim 12 , wherein the optical element is further fabricated to comprise:
an in-coupling diffractive grating disposed on the flat first surface and configured to diffract an image beam into the optical element; and
an out-coupling diffractive grating disposed on the flat second surface and configured to diffract the image beam out of the optical element.
15 . The method of claim 12 , wherein the first angle and the second angle are the same.
16 . The method of claim 12 , wherein the first angle and the second angle are different.
17 . method of claim 12 , wherein fabricating the optical element comprises:
bonding together a plurality of layers to obtain a stack of the layers, wherein at least one of the layers comprises one or more diffractive gratings; and
slicing the stack of the plurality of layers at a desired angle to obtain the optical element comprising the first and second buried diffractive gratings having the slanted arrangement.
18 . A display comprising:
an image source configured to provide an image beam; and
an optical element comprising a flat first surface, a flat second surface opposing the flat first surface, a first buried diffractive grating disposed between the flat first surface and the flat second surface, and a second buried diffractive grating disposed between the first flat surface and the flat second surface, the first buried diffractive grating being positioned in a slanted arrangement at a first angle relative to the flat first surface and the flat second surface, and the second buried diffractive grating being positioned in a slanted arrangement at a second angle relative to the flat first surface and the flat second surface, wherein the second angle is different from the first angle; and
wherein the optical element is configured to convert the image beam into an output image by diffracting the beam through the first buried diffractive grating, the second buried diffractive grating, and propagating the image beam through the optical element.
19 . The display of claim 18 , wherein the first buried diffractive grating is spaced closer to the first surface than the second buried diffractive grating.
20 . The display of claim 18 , wherein the optical element further comprises:
an in-coupling diffractive grating disposed on the flat first surface and configured to diffract the image beam into the optical element; and
an out-coupling diffractive grating disposed on the flat second surface and configured to diffract the image beam out of the optical element.
21 . The display of claim 18 , wherein the optical element further comprises a third buried diffractive grating having a non-slanted arrangement.