Lightguide with image-forming diffractive in-coupler

Patent metadata

Field	Value
Publication number	US-2023393322-A1
Application number	US-202217834760-A
Country	US
Kind code	A1
Filing date	Jun 7, 2022
Priority date	Jun 7, 2022
Publication date	Dec 7, 2023
Grant date	—

Abstract

A display apparatus includes a lightguide for conveying images to an eyebox. The lightguide includes a substrate, a diffractive optical element (DOE) configured to couple the image light into the substrate. The DOE has a spatially variable pitch configured to provide the DOE with a positive optical power. The lightguide further includes a grating out-coupler supported by the substrate for out-coupling portions of the image light from the substrate toward the eyebox.

First claim

What is claimed is:

1 . A lightguide for a display apparatus, the lightguide comprising:
a substrate for relaying image light to an eyebox; an input diffractive optical element (DOE) configured to couple the image light into the substrate, the input DOE having a spatially variable pitch to provide the DOE with an optical power; and a grating out-coupler supported by the substrate for out-coupling portions of the image light from the substrate toward the eyebox.

2 . The lightguide of claim 1 wherein the substrate comprises two opposing surfaces for guiding the image light within the substrate by total internal reflection (TIR) from the surfaces.

3 . The lightguide of claim 2 wherein the input DOE comprises a holographic optical element (HOE) having a positive optical power.

4 . The lightguide of claim 3 wherein the HOE is configured to operate as a focusing lens.

5 . The lightguide of claim 3 wherein the HOE is configured to operate as an off-axis lens.

6 . The lightguide of claim 3 wherein the HOE is configured to transmit therethrough, substantially without diffraction, light incident thereon at angles outside an angular acceptance range of the input DOE.

7 . The lightguide of claim 6 wherein the input DOE is disposed at one of the two opposing surfaces, and is configured so as not to diffract rays of in-coupled image light that are incident thereon after a TIR at the other one of the two opposing surfaces.

8 . The lightguide of claim 6 wherein the angular acceptance range of the input DOE is outside of an angular range of TIR at the opposing surfaces of the substrate.

9 . The lightguide of claim 2 wherein the input DOE has a positive optical power, and wherein the grating out-coupler comprises a first optical diffraction grating (ODG).

10 . The lightguide of claim 9 wherein the input DOE and the first ODG are disposed along the two opposing surfaces with an overlap.

11 . The lightguide of claim 9 wherein the first ODG has a constant grating pitch.

12 . The lightguide of claim 9 wherein the grating out-coupler comprises a second ODG, the first and second ODGs having opposite slant angles.

13 . A display apparatus comprising:
a first lightguide comprising a substrate for relaying image light to a viewing area; an input diffractive optical element (DOE) configured to couple the image light into the lightguide, the input DOE having a spatially variable pitch to provide the DOE with a positive optical power; and a grating out-coupler supported by the substrate for out-coupling the image light from the substrate toward the viewing area.

14 . The display apparatus of claim 13 comprising a curved shell substrate of an optically transparent material, the curved shell substrate comprising the first lightguide including the input DOE and the grating out-coupler.

15 . The display apparatus of claim 14 wherein the first lightguide is disposed in a cavity within the curved shell substrate with gaps between opposing surfaces of the substrate and the material of the shell.

16 . The display apparatus of claim 14 comprising a second lightguide disposed within the curved shell substrate and comprising a substrate, an input DOE, and a diffractive out-coupler, wherein the substrates of the first and second lightguides are an angle to each other.

17 . The display apparatus of claim 13 comprising an image projector for directing the image light toward the input DOE, the image projector disposed at a top portion of the substrate when the display apparatus is in use by a standing person.

18 . The display apparatus of claim 13 wherein the grating out-coupler comprises a diffraction grating having a substantially constant grating pitch.

19 . A lightguide for a display apparatus, the lightguide comprising:
a substrate for relaying image light to an eyebox; an input diffractive optical element (DOE) configured to couple the image light into the substrate, the input DOE having a spatially variable pitch; and a diffractive out-coupler supported by the substrate for out-coupling portions of the image light from the substrate toward the eyebox, the diffractive out-coupler comprising an optical diffraction grating having a substantially constant grating pitch.

20 . The lightguide of claim 19 wherein the input DOE is configured to have a positive optical power.

Assignees

• Meta Platforms Tech Llc

Inventors

• Feng Xiayu
• Zhao Zhexin
• Wang Xuan
• Huang Hekun
• Li Gang
• Lu Lu

Classifications

• G02B2027/0107

  with optical power · CPC title

• G02B2027/0174

  holographic · CPC title

• G02B27/0172 Primary

  characterised by optical features · CPC title

• G02B6/0023 Primary

  provided by one optical element, or plurality thereof, placed between the light guide and the light source, or around the light source · CPC title

• G02B27/4222

  in projection exposure systems, e.g. photolithographic systems · CPC title