Waveguide for an augmented reality or virtual reality display
A waveguide is disclosed for use in an augmented reality or virtual reality display. The waveguide includes a plurality of optical structures exhibiting differences in refractive index from a surrounding waveguide medium. The optical structures are arranged in an array to provide at least two diffractive optical elements overlaid on one another in the waveguide. Each of the two diffractive optical elements is configured to receive light from an input direction and couple it towards the other diffractive optical element which can then act as an output diffractive optical element, providing outcoupled orders towards a viewer. The optical structures have a shape, when viewed in the plane of the waveguide, comprising a plurality of substantially straight sides having respective normal vectors at different angles and this can effectively reduce the amount of light that is coupled out of the waveguide on first interaction with the optical structures.
1 . A system, comprising:
a waveguide; and
an output element of the waveguide, the output element including a plurality of discrete optical structures arranged in an array of a plurality of rows and columns to form a plurality of overlaid diffractive optical elements in or on the waveguide, the plurality of discrete optical structures and the plurality of overlaid diffractive optical elements arranged to receive light input into the waveguide from an input direction and to diffract a first portion of the received light that is input into the waveguide into diffraction orders that are further diffracted in a plane of the waveguide within the output element, and to diffract a second portion of the received light that is input into the waveguide into a diffraction order that is coupled out of the output element of the waveguide towards a viewer without the second portion of the received light internally reflecting in the waveguide, and the plurality of discrete optical structures having respective shapes in a plane view of the waveguide that include a plurality of substantially straight sides having respective angles relative to one another.
2 . The system of claim 1 , wherein each of the plurality of discrete optical structures is parallelogram shaped including four substantially straight sides.
3 . The system of claim 2 , wherein each of the parallelogram shaped discrete optical structures includes a pair of central notches.
4 . The system of claim 1 , wherein each of the plurality of discrete optical structures is embedded within the waveguide.
5 . The system of claim 1 , wherein each of the plurality of discrete optical structures has a different refractive index than a medium of the waveguide.
6 . The system of claim 1 further comprising an input diffractive optical element separate from the plurality of discrete optical structures and the plurality of overlaid diffractive optical elements included in the output element, the input diffractive optical element to couple the light into the waveguide in the input direction to provide light to the plurality of discrete optical structures.
7 . The system of claim 1 , wherein the plurality of discrete optical structures and the plurality of overlaid diffractive optical elements receive the first portion of the received light from an input direction and diffract the first portion of the received light into diffraction orders that are further diffracted in two dimensions in the plane of the waveguide within the output element.
8 . The system of claim 1 , wherein the plurality of discrete optical structures are surface relief structures on a surface of the waveguide.
9 . The system of claim 1 , wherein each of the plurality of discrete optical structures includes substantially straight sides that are angled at substantially ±30° to the input direction.
10 . A system, comprising:
a waveguide; and
an output element of the waveguide, the output element including a plurality of discrete non-circular optical structures arranged in an array of a plurality of rows and columns to form a plurality of overlaid diffractive optical elements in or on the waveguide, the plurality of discrete non-circular optical structures and the plurality of overlaid diffractive optical elements arranged to receive light input into the waveguide from an input direction and to diffract a first portion of the received light that is input into the waveguide into diffraction orders that are further diffracted in two dimensions in a plane of the waveguide within the output element, and to diffract a second portion of the received light that is input into the waveguide into a diffraction order that is coupled out of the output element of the waveguide towards a viewer without the second portion of the received light internally reflecting in the waveguide.
11 . The system of claim 10 , wherein each of the plurality of discrete non-circular optical structures includes a plurality of substantially straight sides having respective angles relative to one another.
12 . The system of claim 11 , wherein each of the plurality of discrete non-circular optical structures has a shape of a parallelogram in the plane of the waveguide.
13 . The system of claim 12 , wherein the parallelogram of each of the plurality of discrete non-circular optical structures includes four main sides and further includes a pair of central notches, each central notch including two sides, each of these two sides being parallel to two of the four main sides.
14 . The system of claim 10 further comprising an input diffractive optical element separate from the plurality of discrete non-circular optical structures and the plurality of overlaid diffractive optical elements included in the output element, the input diffractive optical element to couple the light into the waveguide in the input direction to provide light to the plurality of discrete non-circular optical structures.
15 . The system of claim 10 , wherein the plurality of discrete non-circular optical structures and the plurality of overlaid diffractive optical elements receive the first portion of the received light from an input direction and diffract the first portion of the received light into diffraction orders that are further diffracted in two dimensions in the plane of the waveguide within the output element.
16 . The system of claim 10 , wherein the plurality of discrete non-circular optical structures are surface relief structures on a surface of the waveguide.
17 . A method, comprising:
providing an output element of a waveguide that comprises an array of discrete surface relief optical structures in a plurality of rows and columns on a surface of the waveguide, the discrete surface relief optical structures having a different refractive index than a medium surrounding the discrete surface relief optical structures to form a plurality of overlaid diffractive optical elements on the surface;
receiving light input into the surface of the waveguide from an input direction at the plurality of overlaid diffractive optical elements;
diffracting a first portion of the received light that is input into the surface of the waveguide through the plurality of overlaid diffractive optical elements into diffraction orders that are further diffracted in a plane of the waveguide within the output element; and
diffracting a second portion of the received light that is input into the surface of the waveguide into a diffraction order that is coupled out of the output element of the waveguide towards a viewer without the second portion of the received light internally reflecting in the waveguide.
18 . The method of claim 17 , wherein the medium surrounding the discrete surface relief optical structures is air.
19 . The method of claim 17 further comprising providing a coating on the array of discrete surface relief optical structures to control diffraction efficiency of the plurality of overlaid diffractive optical elements.
20 . The method of claim 17 further comprising:
applying a bonding material on the array of discrete surface relief optical structures, the bonding material having a shape that is the same as a shape of the discrete surface relief optical structures and having an index of refraction that is different than an index of refraction of the waveguide; and
attaching a cover piece to the waveguide through the bonding material, the cover piece having the same index of refraction as the waveguide.