Input/output coupling grating and display including the same
A head-mounted display system includes a waveguide configured to guide light from a light projection system coupled into the waveguide; a grating structure optically coupled to the waveguide, the grating structure being configured to couple light from the light projection system into the waveguide. The grating structure includes a grating layer having a grating with multiple ridges having ablaze profile in at least one cross-section, the blaze profile having an anti-blaze angle of 85° or less; and one or more additional layers on the grating layer, the additional layers including a first layer of a material having a refractive index of 1.5 or less at an operative wavelength of the head-mounted display, the first layer being an outermost layer of the grating structure.
1 . A head-mounted display system comprising:
a head-mountable frame;
a light projection system configured to output light to provide image content;
a waveguide supported by the head-mountable frame, the waveguide configured to guide at least a portion of the light from the light projection system coupled into the waveguide;
a grating structure optically coupled to the waveguide, the grating structure being configured to couple the light from the light projection system into the waveguide, the grating structure comprising:
a grating layer comprising a grating comprising a plurality of ridges having a blaze profile in at least one cross-section, the blaze profile comprising an anti-blaze angle of 89° or less; and
one or more additional layers disposed on the grating layer, the one or more additional layers comprising a first layer of a material having a refractive index of 1.5 or less at an operative wavelength of the head-mounted display system, the first layer being an outermost layer of the grating structure,
wherein the grating layer is disposed between the waveguide and the one or more additional layers, and the first layer is discontinuous between adjacent ridges of the plurality of ridges.
2 . The head-mounted display system of claim 1 , wherein the blaze profile has a blaze angle of 95° or more.
3 . The head-mounted display system of claim 1 , wherein the ridges have a profile shape selected from the group consisting of: trapezoidal, parallelogram, triangular, and stepped.
4 . The head-mounted display system of claim 1 , wherein the anti-blaze angle is in a range from 1° to 89°.
5 . The head-mounted display system of claim 1 , wherein the ridges have a height in a range from 10 nm to 1,000 nm.
6 . The head-mounted display system of claim 1 , wherein the grating has a pitch in a range from 100 nm to 5,000 nm.
7 . The head-mounted display system of claim 1 , wherein the grating has a duty cycle in a range from 5% to 95%.
8 . The head-mounted display system of claim 1 , wherein the first layer has a thickness in a range from 5 nm to 500 nm.
9 . The head-mounted display system of claim 1 , wherein the one or more additional layers comprise a second layer between the first layer and the grating layer, the second layer comprises a second material having a refractive index greater than 1.5 at the operative wavelength, and
the grating layer comprises a grating material having a refractive index of 1.5 or more at the operative wavelength.
10 . The head-mounted display system of claim 9 , wherein the grating material comprises a cross-linked polymer.
11 . The head-mounted display system of claim 10 , wherein the grating material comprises nanoparticles.
12 . The head-mounted display system of claim 1 , wherein the grating structure is at least partially transmissive at the operative wavelength.
13 . The head-mounted display system of claim 1 , wherein, during operation, the grating structure is configured to couple light into the waveguide at operative wavelengths corresponding to multiple differently colored pixels of the light projection system.
14 . The head-mounted display system of claim 1 , wherein the grating layer and the waveguide are composed of the same material.
15 . The head-mounted display system of claim 14 , wherein the material comprises a polymer.
16 . The head-mounted display system of claim 14 , wherein the material has a refractive index of 1.7 or more.
17 . The head-mounted display system of claim 1 , wherein the light from the light projection system is unpolarized light or polarized light.
18 . The head-mounted display system of claim 1 , wherein the light projection system comprises a microLED display, an LCOS display, or a laser beam scanner display.
19 . The head-mounted display system of claim 1 , wherein the grating structure is a first grating structure, and
further comprising a second grating structure located on an opposite side of the waveguide from the first grating structure, the second grating structure being optically coupled to the waveguide and comprising a second grating layer comprising a second grating comprising a plurality of ridges having a blaze profile in at least one cross-section, the blaze profile comprising an anti-blaze angle of 89° or less.
20 . The head-mounted display system of claim 1 , further comprising one or more additional waveguides and one or more additional grating structures each associated with a corresponding one of the additional waveguides.
21 . The head-mounted display system of claim 20 , wherein the one or more additional grating structures of each of the one or more additional waveguides is arranged in an inline configuration,
wherein at least one of the one or more additional grating structures is a reflection grating, and
wherein the reflection grating is the grating structure of the waveguide furthest from the light projection system.
22 . The head-mounted display system of claim 1 , wherein at least some of the ridges have a single-step geometry.
23 . The head-mounted display system of claim 1 , wherein at least some of the ridges have a multi-step geometry.