Waveguide-based displays with anti-reflective and highly-reflective coating

Patent metadata

Field	Value
Publication number	US-9891436-B2
Application number	US-201615041664-A
Country	US
Kind code	B2
Filing date	Feb 11, 2016
Priority date	Feb 11, 2016
Publication date	Feb 13, 2018
Grant date	Feb 13, 2018

Abstract

A near eye or heads up display system includes a display engine, at least two optical waveguides, and a respective coating on at least one of the major surfaces of at least one of the waveguides. At least one such coating has a low reflectance for light within a specific wavelength range for the waveguide and incident on a major surface of the waveguide on which the coating is located at an angle below a low threshold angle relative to a normal, and has a high reflectance for light within the specific wavelength range for the waveguide that is incident on the major surface on which the coating is located at an angle above a high threshold angle relative to the normal.

First claim

What is claimed is:

1. An apparatus, comprising:
an optical waveguide including a bulk-substrate, an input-coupler and an output-coupler;
the bulk-substrate of the optical waveguide including a first major surface and a second major surface opposite and the first major surface;
the input-coupler of the optical waveguide configured to couple, into the bulk substrate of the optical waveguide, light that is within an input angular range and within a first wavelength range;
the output-coupler of the optical waveguide configured to couple, out of the bulk-substrate of the optical waveguide, light within an output angular range and within the first wavelength range that travels through the optical waveguide from the input-coupler to the output-coupler at least in part by way of total internal reflection (TIR);
a coating on one of the first and second major surfaces of the optical waveguide;
the coating configured to have a low reflectance of no more than 2 percent for light within the first wavelength range that is traveling within the bulk-substrate of the optical waveguide and is incident on the one of the first and second major surfaces of the optical waveguide on which the coating is located at each angle below a low threshold angle of no more than 25 degrees relative to a normal of the one of the first and second major surfaces of the optical waveguide on which the coating is located; and
the coating configured to have a high reflectance of at least 50 percent for light within the first wavelength range that is traveling within the bulk-substrate of the optical waveguide and is incident on the one of the first and second major surfaces of the optical waveguide on which the coating is located at each angle above a high threshold angle of at least 30 degrees relative relative to the normal of the one of the first and second major surfaces of the optical waveguide on which the coating is located.

2. The apparatus of claim 1 , wherein the coating includes alternating layers of two or more different materials having different indices of refraction between 1.3 and 2.2.

3. The apparatus of claim 2 , wherein at least some of the alternating layers of the two or more different materials, which have different indices of refraction between 1.3 and 2.2, have different thicknesses than one another, the thickness selected to provide:
the low reflectance of no more than 2 percent for light within the first wavelength range that is incident on the one of the first and second major surfaces of the optical waveguide on which the coating is located at each angle below the low threshold angle of no more than 25 degrees relative to the normal of the one of the first and second major surfaces of the optical waveguide on which the coating is located, and
the high reflectance of at least 50 percent for light within the first wavelength range that is incident on the one of the first and second major surfaces of the optical waveguide on which the coating is located at each angle above the high threshold angle of at least 30 degrees relative to the normal of the one of the first and second major surfaces of the optical waveguide on which the coating is located.

4. The apparatus of claim 1 , wherein the coating includes:
alternating layers of silicon dioxide and titanium dioxide;
alternating layers of silicon dioxide and aluminum oxide; or
alternating layers of silicon dioxide, titanium dioxide and aluminum oxide.

5. The apparatus of claim 1 , wherein the high reflectance is of at least 75 percent for light within the first wavelength range that is traveling within the bulk-substrate of the optical waveguide and is incident on the one of the first and second major surfaces of the optical waveguide on which the coating is located at each angle above the high threshold angle of at least 30 degrees relative relative to the normal of the one of the first and second major surfaces of the optical waveguide on which the coating is located.

6. The apparatus of claim 1 , wherein the coating on the one of the first and second major surfaces of the optical waveguide has a preferential polarization orientation that enables the coating to have the low reflectance of no more than 2 percent for light within the first wavelength range that is traveling within the bulk-substrate of the optical waveguide and is incident on the one of the first and second major surfaces of the optical waveguide on which the coating is located at each angle below the low threshold angle that is no more than 25 degrees relative to the normal of the one of the first and second major surfaces of the optical waveguide on which the coating is located, and enables the coating on the one of the first and second major surfaces of the optical waveguide to have the high reflectance of at least 50 percent for light within the first wavelength range that is traveling within the bulk-substrate of the optical waveguide and is incident on the one of the first and second major surfaces of the optical waveguide on which the coating is located at each angle above the high threshold angle that is at least 30 degrees relative to the normal of the one of the first and second major surfaces of the optical waveguide on which the coating is located.

7. The apparatus of claim 1 , wherein the first wavelength range comprises one of a red wavelength range, a green wavelength range or a blue wavelength range.

8. The apparatus of claim 1 , wherein the first wavelength range comprises both a green wavelength range and a blue wavelength range.

9. The apparatus of claim 1 , wherein the optical waveguide comprises a first optical waveguide and the coating comprises a first coating, and wherein the apparatus further comprises:
a display engine configured to produce an image including light within the first wavelength range and light within a second wavelength range that differs from the first wavelength range, and wherein:
a second optical waveguide next to the first optical waveguide, the second optical waveguide including a bulk-substrate, an input-coupler and an output-coupler;
the bulk-substrate of the second optical waveguide including a first major surface and a second major surface opposite and the first major surface;
the input-coupler of the second optical waveguide configured to couple, into the bulk substrate of the second optical waveguide, light of the image produced by the display engine that is within the input angular range and within the second wavelength range;
the output-coupler of the second optical waveguide configured to couple, out of the bulk-substrate of the second optical waveguide, light of the image within the output angular range and within the second wavelength range that travels through the second optical waveguide from the input-coupler to the output-coupler of the second optical waveguide at least in part by way of TIR; and
wherein the first coating is on the one of the first and second major surfaces of the first optical waveguide that is closest to the second optical waveguide.

10. The apparatus of claim 9 , wherein:
the image produced by the display engine also includes light within a third wavelength range that differs from the first and second wavelength ranges;
the first and second optical waveguides are part of a waveguide assembly that also includes a third optical waveguide arranged next to the second optical waveguide;
the third optical waveguide includes a bulk-substrate, an input-coupler and an output-coupler;
the input-coupler of the third optical waveguide is configured to couple, into the bulk substrate of the third optical waveguide, light of the image produced by the display engine that is within the input angular range and within the third wavelength

Assignees

• Microsoft Technology Licensing Llc

Inventors

• Wall R Andrew
• Vallius Tuomas
• Pietila Pasi
• Oka Keita

Classifications

• G02B1/115

  Multilayers · CPC title

• G02B6/0026

  Wavelength selective element, sheet or layer, e.g. filter or grating · CPC title

• G02B2027/0112

  comprising device for genereting colour display · CPC title

• G02B6/0076

  Stacked arrangements of multiple light guides of the same or different cross-sectional area · CPC title

• G02B5/26

  Reflecting filters (G02B5/28 takes precedence) · CPC title