Eyepieces for augmented reality display system
An eyepiece waveguide for an augmented reality display system. The eyepiece waveguide can include an optically transmissive substrate with an input coupling grating (ICG) region. The ICG region can receive a beam of light and couple the beam into the substrate in a guided propagation mode. The eyepiece waveguide can also include a combined pupil expander-extractor (CPE) grating region that receives the beam of light from the ICG region and alters the propagation direction of the beam with a first interaction and out-couples the beam with a second interaction. The diffractive features of the CPE grating region can be arranged in rows and columns of alternating higher and lower quadrilateral surfaces or the diffractive features can comprise diamond shaped raised ridges. The eyepiece waveguide can also include one or more recycler grating regions.
1 . An eyepiece waveguide for an augmented reality display system, the eyepiece waveguide comprising:
an optically transmissive substrate having a first surface and a second surface;
an input coupling grating (ICG) region formed on or in one of the surfaces of the substrate, the ICG region being configured to receive a beam of light and to couple the beam into the substrate such that the beam of light propagates in the substrate in a guided propagation mode; and
a first combined pupil expander-extractor (CPE) grating region formed on or in the first surface of the substrate, the first CPE grating region being positioned to receive the beam of light that is propagating in the substrate, and the first CPE grating region comprising a plurality of diffractive features configured to alter a propagation direction of the propagating beam with a first interaction, and to out-couple the propagating beam from the eyepiece waveguide with a second interaction,
wherein the diffractive features are arranged in rows and columns of alternating higher and lower quadrilateral surfaces,
wherein the diffractive features comprise a 2D grating with a diamond-shaped unit cell, and
wherein the diamond-shaped unit cell comprises one of the higher quadrilateral surfaces inscribed therein such that corners of the higher quadrilateral surface are located at midpoints of the diamond-shaped unit cell.
2 . The eyepiece waveguide of claim 1 , wherein the rows and columns of alternating higher and lower quadrilateral surfaces form a checkered pattern.
3 . The eyepiece waveguide of claim 2 , wherein the checkered pattern has a substantially 50% duty cycle.
4 . The eyepiece waveguide of claim 1 , wherein the quadrilateral surfaces are rectangular.
5 . The eyepiece waveguide of claim 4 , wherein the rectangular surfaces have length and width dimensions such that an angle between their diagonals is substantially 60°.
6 . The eyepiece waveguide of claim 1 , wherein the higher and lower quadrilateral surfaces are equally sized and shaped.
7 . The eyepiece waveguide of claim 1 , wherein the 2D grating comprises a tiled pattern of the diamond-shaped unit cell.
8 . The eyepiece waveguide of claim 1 , wherein the CPE grating region exhibits direct out-coupling diffraction with an efficiency that is less than 1% of spreading diffraction.
9 . The eyepiece waveguide of claim 1 , wherein the higher quadrilateral surfaces comprise pillars with sidewalls that are perpendicular to the first surface of the substrate.
10 . The eyepiece waveguide of claim 1 , wherein the higher quadrilateral surfaces comprise pillars with sidewalls that are slanted with respect to the first surface of the substrate.
11 . The eyepiece waveguide of claim 10 , wherein the slanted sidewalls are symmetric.
12 . The eyepiece waveguide of claim 10 , wherein the slanted sidewalls are asymmetric to form a blazed grating.
13 . The eyepiece waveguide of claim 1 , wherein the heights of the higher quadrilateral surfaces are spatially gradated.
14 . The eyepiece waveguide of claim 13 , wherein the higher quadrilateral surfaces have increasing heights with increasing distance from the ICG region.
15 . The eyepiece waveguide of claim 1 , further comprising a second CPE grating region formed on or in the second surface of the substrate, the second CPE grating region comprising a plurality of diffractive features configured to alter the propagation direction of the propagating beam with a first interaction, and to out-couple the propagating beam from the eyepiece waveguide with a second interaction.
16 . The eyepiece waveguide of claim 15 , wherein the first and second CPE grating regions are identical.
17 . The eyepiece waveguide of claim 15 , wherein the substrate has a thickness that is large enough to prevent the propagating beam from interacting with the ICG region.
18 . The eyepiece waveguide of claim 1 , wherein the ICG region is further configured to receive the beam of light that is collimated and has a diameter of 5 mm or less.
19 . The eyepiece waveguide of claim 1 , wherein the optically transmissive substrate is planar.
20 . An augmented reality display system comprising an eyepiece that includes the eyepiece waveguide of claim 1 .
21 . The augmented reality display system of claim 20 , wherein the eyepiece is configured to display color images at a plurality of depth planes.
22 . The eyepiece waveguide of claim 1 , wherein a coating is formed over the diffractive features.
23 . The eyepiece waveguide of claim 22 , wherein the refractive index of the coating is at least 2.0.
24 . The eyepiece waveguide of claim 22 , wherein the coating is conformal.
25 . The eyepiece waveguide of claim 22 , wherein the coating is no thicker than 100 nm.
26 . The eyepiece waveguide of claim 25 , wherein the coating is no thicker than 60 nm.
27 . The eyepiece waveguide of claim 22 , wherein the coating comprises a material with a higher refractive index than that of the diffractive features.
28 . An eyepiece waveguide for an augmented reality display system, the eyepiece waveguide comprising:
an optically transmissive substrate having a first surface and a second surface;
an input coupling grating (ICG) region formed on or in one of the surfaces of the substrate, the ICG region being configured to receive a beam of light and to couple the beam into the substrate such that the beam of light propagates in the substrate in a guided propagation mode; and
a first combined pupil expander-extractor (CPE) grating region formed on or in the first surface of the substrate, the first CPE grating region being positioned to receive the beam of light that is propagating in the substrate, and the first CPE grating region comprising a plurality of diffractive features configured to alter a propagation direction of the propagating beam with a first interaction, and to out-couple the propagating beam from the eyepiece waveguide with a second interaction,
wherein the diffractive features are arranged in rows and columns of alternating higher and lower quadrilateral surfaces,
wherein the plurality of diffractive features of the first CPE grating region exhibit periodicities in at least a first direction, a second direction, and a third direction,
wherein the first and second directions are oriented at an angle of substantially 60° with respect to one another, and
wherein the third direction is oriented at an angle of substantially 60° with respect to both the first direction and the second direction.