US-20260126660-A1 - WAVEGUIDE AND DIFFRACTION GRATING FOR AUGMENTED REALITY OR VIRTUAL REALITY DISPLAY

Abstract

A waveguide for use in a virtual reality, VR, or augmented reality, AR, device, is disclosed. The waveguide comprising an input region configured to couple light into the waveguide so that it propagates under total internal reflection (TIR) within the waveguide, and an output region comprising optical structures configured to receive image bearing light from the input region. The output region comprises a plurality of zones having different diffraction to each other, the plurality of zones comprising diffraction efficiencies so as to reduce rainbow artefacts.

Inventors

• Alexandra Crai
• Ciaran Phelan
• Mohmed Salim Ibrahim Valera
• David Nicholas Crosby

Assignees

• SNAP INC.

Dates

Publication Date

20260507

Application Date

20260105

Priority Date

20210609

Claims (20)

1. 1 . A waveguide for an augmented reality or virtual reality display, the waveguide comprising: an output region to: receive image-bearing light propagating within the waveguide under total internal reflection (TIR); and outcouple the image-bearing light in multiple different directions toward a viewer through diffractive interactions, wherein the output region comprises a plurality of zones, each zone having optical structures with diffraction efficiencies to: outcouple light propagating in a first direction; and outcouple light propagating in a second direction different from the first direction, wherein the diffraction efficiencies of the optical structures of at least two of the plurality of zones differ from each other to reduce rainbow artifacts visible to a viewer.
2. 2 . The waveguide of claim 1 , wherein: each of the at least two of the plurality of zones has a non-zero diffraction efficiency for: a first interaction outcoupling the light propagating in the first direction; and a second interaction outcoupling the light propagating in the second direction, such that the light outcoupled by the first interaction and the second interaction in each of the at least two zones is non-evanescent.
3. 3 . The waveguide of claim 1 , wherein: each of the at least two of the plurality of zones comprises: a first rectangular periodic array of optical structures arranged on a plane defined by the first and second directions, a period of the first rectangular periodic array being defined by a spacing between neighboring optical structures of the first rectangular periodic array, the first rectangular periodic array forming a first 2D lattice with rectangular symmetry; and a second rectangular periodic array of optical structures arranged on the plane, a period of the second rectangular periodic array being defined by a spacing between neighboring optical structures of the second rectangular periodic array, the second rectangular periodic array forming a second 2D lattice with rectangular symmetry; and the first rectangular periodic array is overlaid on the second rectangular periodic array in the plane such that the arrays are spatially offset from one another on the plane.
4. 4 . The waveguide of claim 3 , wherein: the first rectangular periodic array is offset from the second rectangular periodic array by a factor which is different from half the period of the first rectangular periodic array and different from half the period of the second rectangular periodic array.
5. 5 . The waveguide of claim 4 , wherein: a first zone of the at least two zones has a diffraction efficiency of the outcoupling of light propagating in the first direction that is greater than the diffraction efficiency of the outcoupling of light propagating in the second direction in the first zone; and the first zone comprises the first and second rectangular periodic arrays arranged such that: the first rectangular periodic array is offset from the second rectangular periodic array in the first direction by a factor which is different from each of: the period of the first rectangular periodic array; the period of the second rectangular periodic array; half the period of the first rectangular periodic array; and half the period of the second rectangular periodic array, such that the optical structures of the first and second rectangular periodic arrays form a continuous structure along the second direction.
6. 6 . The waveguide of claim 4 , wherein: a first zone of the at least two zones has a diffraction efficiency of the outcoupling of light propagating in the second direction that is greater than the diffraction efficiency of the outcoupling of light propagating in the first direction in the first zone; and the first zone comprises the first and second rectangular periodic arrays arranged such that: the first rectangular periodic array is offset from the second rectangular periodic array in the second direction by a factor which is different from each of: the period of the first rectangular periodic array; the period of the second rectangular periodic array; half the period of the first rectangular periodic array; and half the period of the second rectangular periodic array, such that the optical structures of the first and second rectangular periodic array form a continuous structure along the first direction.
7. 7 . The waveguide of claim 4 , wherein: a first zone of the at least two zones comprises optical structures arranged such that: the first rectangular periodic array is offset from the second rectangular periodic array by a factor which is different from half the period of the first rectangular periodic array along the second direction and is different from half the period of the second rectangular periodic array along the second direction; and the first rectangular periodic array is offset from the second rectangular periodic array by half the period of the first or second rectangular periodic array along the first direction.
8. 8 . The waveguide of claim 1 , wherein: the second direction is perpendicular to the first direction.
9. 9 . The waveguide of claim 1 , wherein: the optical structures of each of the at least two of the plurality of zones diffracts at least a portion of light to turn such that it is caused to propagate under TIR within the waveguide in a direction that is different from a direction in which it is propagating prior to the turning.
10. 10 . The waveguide of claim 9 , wherein: the turning turns the light to propagate in a direction that is perpendicular to the direction in which it is propagating prior to the turning.
11. 11 . The waveguide of claim 9 , wherein: the plurality of zones further comprises a third zone in addition to the at least two zones; the third zone receives light propagating under TIR within the waveguide before interacting with either of the at least two zones, the third zone having a diffraction efficiency for the turning that is higher than the diffraction efficiency of the third zone of both the outcoupling of light propagating in the first direction and the outcoupling of light propagating in the second direction; the third zone is located in the first direction from a first zone of the at least two zones; and the first zone has a diffraction efficiency of the outcoupling of light propagating in the second direction that is greater than a diffraction efficiency of the outcoupling of light propagating in the second direction of the third zone.
12. 12 . The waveguide of claim 11 , wherein: the diffraction efficiency of the outcoupling of light propagating in the first direction in a second zone of the at least two zones is greater than: the diffraction efficiency of the outcoupling of light propagating in the first direction in the first zone; and the diffraction efficiency of the outcoupling of light propagating in the first direction in the third zone.
13. 13 . The waveguide of claim 11 , wherein: the diffraction efficiency of the outcoupling of light propagating in the second direction in a second zone of the at least two zones is greater than: the diffraction efficiency of the outcoupling of light propagating in the second direction in the first zone; and the diffraction efficiency of the outcoupling of light propagating in the second direction in the third zone.
14. 14 . The waveguide of claim 11 , wherein: the third zone comprises: a first rectangular periodic array of optical structures arranged on a plane defined by the first and second directions, a period of the first rectangular periodic array being defined by a spacing between neighboring optical structures of the first rectangular periodic array, the first rectangular periodic array forming a first 2D lattice with rectangular symmetry; and a second rectangular periodic array of optical structures arranged on the plane, a period of the second rectangular periodic array being defined by a spacing between neighboring optical structures of the second rectangular periodic array, the second rectangular periodic array forming a second 2D lattice with rectangular symmetry; and the first rectangular periodic array is overlaid on the second rectangular periodic array in the plane such the first rectangular periodic array is: offset from the second rectangular periodic array along the second direction by a factor which is different from half the period of the first rectangular periodic array and different from half the period of the second rectangular periodic array; and offset from the second rectangular periodic array along the first direction by half the period of the first rectangular periodic array or half the period of the second rectangular periodic array.
15. 15 . The waveguide of claim 14 , wherein the factor by which the first rectangular periodic array is offset from the second rectangular periodic array along the second direction in the third zone is smaller than the factor by which the first rectangular periodic array is offset from the second rectangular periodic array along the second direction in the first zone.
16. 16 . The waveguide of claim 1 , wherein: the at least two zones comprises a first zone and a second zone; the second zone has a diffraction efficiency of the outcoupling of light propagating in the second direction that is greater than the diffraction efficiency of the outcoupling of light propagating in the first direction in the second zone; and the second zone has a diffraction efficiency of the outcoupling of light propagating in the first direction that is less than the diffraction efficiency of the outcoupling of light propagating in the first direction in the first zone.
17. 17 . The waveguide of claim 1 , wherein: a first zone of the at least two zones has a diffraction efficiency of the outcoupling of light propagating in the first direction on that is greater than the diffraction efficiency of the outcoupling of light propagating in the second direction in the first zone; and the first zone comprises optical structures that are continuous along the second direction.
18. 18 . The waveguide of claim 1 , wherein: a first zone of the at least two zones has a diffraction efficiency of the outcoupling of light propagating in the second direction that is greater than the diffraction efficiency of the outcoupling of light propagating in the first direction in the first zone; and the first zone comprises optical structures that are continuous along the first direction.
19. 19 . An augmented reality or virtual reality display comprising a waveguide, the waveguide comprising an output region to: receive image-bearing light propagating within the waveguide under total internal reflection (TIR); and outcouple the image-bearing light in multiple different directions toward a viewer through diffractive interactions, wherein the output region comprises a plurality of zones, each zone having optical structures with diffraction efficiencies to: outcouple light propagating in a first direction; and outcouple light propagating in a second direction different from the first direction, wherein the diffraction efficiencies of the optical structures of at least two of the plurality of zones differ from each other to reduce rainbow artifacts visible to a viewer.
20. 20 . A method comprising: receiving image-bearing light propagating under total internal reflection (TIR) within a waveguide at a plurality of zones of an output region of the waveguide; and outcoupling the image-bearing light in multiple different directions toward a viewer through diffractive interactions, wherein each zone of the plurality of zones has optical structures with diffraction efficiencies to: outcouple light propagating in a first direction; and outcouple light propagating in a second direction different from the first direction, wherein the diffraction efficiencies of the optical structures of at least two of the plurality of zones differ from each other to reduce rainbow artifacts visible to a viewer.

Description

CLAIM OF PRIORITY This application is a continuation of U.S. patent application Ser. No. 18/976,111, filed on Dec. 10, 2024, which is a continuation of U.S. patent application Ser. No. 18/563,733, filed on Nov. 22, 2023, which is a U.S. national-phase application filed under 35 U.S.C. § 371 from International Application Serial No. PCT/EP2022/065292, filed on Jun. 6, 2022, and published as WO 2022/258553 on Dec. 15, 2022, which claims the benefit of priority to European Patent Application Serial No. 21178594.4, filed on Jun. 9, 2021, each of which is incorporated herein by reference in its entirety. FIELD The present invention relates to a diffractive waveguide combiner for use in an augmented reality or virtual reality display. In particular, an aspect of the invention relates to a waveguide in which light coupled into the waveguide is expanded in two dimensions by a diffractive optical element as well as coupled out of the waveguide towards a viewer. This can allow pupil replication, eyebox expansion and relay of a projected image in an augmented reality or virtual reality display. BACKGROUND An augmented reality display provides a user, or viewer, with a view of their real-world surroundings combined with other images such as those artificially generated by a computerised display system. Often the overlaid images provide information that is relevant to the real-world surroundings. For example, in transportation applications the overlaid images may provide navigation assistance or information regarding hazards. In medical applications such as in an operating theatre the overlaid images may provide real-time information regarding a patient such as heart-rate and blood oxygen levels, or provide complementary data to assist a surgeon such as x-ray images or other medical scans. In video game applications the overlaid images may include computer generated characters or objects which may then appear to interact with the real-world, including the viewer, in response to data gathered from other sensors, such as cameras. In some augmented reality display systems the entire image provided to the viewer is in the form of a computer generated display output on a monitor or other visual display screen. In these systems cameras are used to capture images of the real-world surroundings which are then combined with computer generated images and the resulting combination shown to a viewer using the image processing software and hardware of a computerised display system. Suitable display systems are widely available and typically found in personal computers, smartphones, tablets and other devices which combine computational processing, image capture and a visual display screen. In other augmented reality display systems a viewer directly observes the real-world through a transparent or semi-transparent optical device, often termed a combiner. The combiner provides a means by which additional images can be overlaid on this view of the real-world. These images will typically be generated by a computerised display system connected to suitable image projection hardware such as a micro-display based projector. The provision of direct viewing of real-world surroundings to a viewer rather than via image capture and re-display provides multiple advantages, such as: the field-of-view, resolution and dynamic-range of real-world viewing considerably outstrips the capability of any artificial display hardware available at present; removal of the need to place a display screen in-front of the viewer can result in a smaller and more socially acceptable form-factor for a display system; and real-world viewing contains three-dimensional data and focus cues which are known to be important for long term wear and the avoidance of eye-strain. Augmented reality display systems that combine direct viewing of real-world surroundings with additional, generated images may be fixed to a larger installation such as the cockpit of an aircraft, in which case they are often referred to as Head-Up Displays (or HUDs), or part of a portable device that is worn by a viewer, in which case they are often called Head-Mounted Displays (HMDs). A virtual reality display is one where the entire image seen by a viewer is artificially generated. A combiner used in an AR-HMD may also be configured for use in a virtual reality head mounted display (VR-HMD) simply by suppressing observation of the real-world, for example, by using an opaque black screen between the combiner and the real world, but not between the combiner and a viewer's eyes. There are several different methods by which computer generated images may be optically combined with a view of the real world. A simple method is to make the combiner a partially reflective piece of glass and place it at a tilted angle such that the reflection from the glass allows the viewer to see an image that would otherwise be outside of their field of view. This is the approach used in many autocue systems where a tilted