AR/VR Waveguide and Diffraction Grating Zones for Rainbow Artefact Reduction

Solution Overview

Problem

Existing augmented reality (AR) and virtual reality (VR) waveguide combiners suffer from issues such as limited eyebox expansion, rainbow artefacts, and inefficient use of space, which restrict the size and performance of the display system, particularly due to the constraints of diamond-shaped optical structures and narrow manufacturing tolerances.

Innovation Solution

A waveguide design with an output region comprising multiple zones of varying diffraction efficiencies, utilizing interleaved rectangular gratings with offset arrays to reduce rainbow artefacts and enhance image uniformity, allowing for two-dimensional eyebox expansion and efficient light distribution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If diamond-shaped optical structures are used in the waveguide output region, then pupil replication and eyebox expansion are achieved, but rainbow artefacts are generated and manufacturing tolerances become extremely narrow

Engineering Contradiction:

Improveeyebox sizeVSAvoidrainbow artefacts

Core Design Contradiction:

Area of stationary objectVSObject-affected harmful factors

Solution Approach 1:

The output region is divided into multiple zones with different diffraction efficiency characteristics. The first zone has higher diffraction efficiency for generating pupil replicas, while the second zone has lower diffraction efficiency to reduce rainbow artefacts. This spatial segmentation allows different regions to perform different functions, resolving the contradiction between eyebox expansion and artefact reduction.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different zones within the output region are assigned different local optical properties, specifically varying diffraction efficiencies. The first zone is optimized for strong pupil replication to expand the eyebox, while the second zone is optimized for reduced diffraction to minimize rainbow artefacts. This local differentiation resolves the contradiction by allowing each zone to optimize for its specific function.

Inventive Principle:

Principle #3Local quality

2Area of stationary object

If diamond-shaped optical structures are used in the waveguide output region, then pupil replication and eyebox expansion are achieved, but manufacturing tolerances become extremely narrow

Engineering Contradiction:

Improveeyebox sizeVSAvoidmanufacturing tolerances

Core Design Contradiction:

Area of stationary objectVSManufacturing precision

Solution Approach 1:

The output region is divided into multiple zones with different diffraction efficiency characteristics. The first zone has higher diffraction efficiency for generating pupil replicas, while the second zone has lower diffraction efficiency to reduce rainbow artefacts. This spatial segmentation allows different regions to perform different functions, resolving the contradiction between eyebox expansion and artefact reduction.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different zones within the output region are assigned different local optical properties, specifically varying diffraction efficiencies. The first zone is optimized for strong pupil replication to expand the eyebox, while the second zone is optimized for reduced diffraction to minimize rainbow artefacts. This local differentiation resolves the contradiction by allowing each zone to optimize for its specific function.

Inventive Principle:

Principle #3Local quality

3Ease of manufacture

If uniform diffraction efficiency is used across the entire output region, then manufacturing is simplified, but rainbow artefacts increase and image uniformity deteriorates

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidrainbow artefacts

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The output region is divided into multiple zones with different diffraction efficiency characteristics. The first zone has higher diffraction efficiency for generating pupil replicas, while the second zone has lower diffraction efficiency to reduce rainbow artefacts. This spatial segmentation allows different regions to perform different functions, resolving the contradiction between eyebox expansion and artefact reduction.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different zones within the output region are assigned different local optical properties, specifically varying diffraction efficiencies. The first zone is optimized for strong pupil replication to expand the eyebox, while the second zone is optimized for reduced diffraction to minimize rainbow artefacts. This local differentiation resolves the contradiction by allowing each zone to optimize for its specific function.

Inventive Principle:

Principle #3Local quality

4Use of energy by moving object

If higher diffraction efficiency is used throughout the output region, then light coupling out to the viewer is improved, but rainbow artefacts from external light sources increase

Engineering Contradiction:

Improvelight coupling efficiencyVSAvoidrainbow artefacts from external light

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The output region is divided into multiple zones with different diffraction efficiency characteristics. The first zone has higher diffraction efficiency for generating pupil replicas, while the second zone has lower diffraction efficiency to reduce rainbow artefacts. This spatial segmentation allows different regions to perform different functions, resolving the contradiction between eyebox expansion and artefact reduction.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different zones within the output region are assigned different local optical properties, specifically varying diffraction efficiencies. The first zone is optimized for strong pupil replication to expand the eyebox, while the second zone is optimized for reduced diffraction to minimize rainbow artefacts. This local differentiation resolves the contradiction by allowing each zone to optimize for its specific function.

Inventive Principle:

Principle #3Local quality

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution provides a larger eyebox with reduced rainbow artefacts and improved image uniformity, enhancing the user experience by minimizing distracting visual effects and optimizing the display system's size and efficiency.

Implementation Method 1

an input region configured to couple light into the waveguide so that it propagates under total internal reflection (TIR) within the waveguide

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Implementation Method 2

an output element comprising a diffractive optical element configured to expand light in two dimensions and couple it out of the waveguide towards a viewer

Methodology Applied

Scientific EffectDiffraction: Diffraction

Data Source

PatentEP4352410B1Waveguide and diffraction grating for augmented reality or virtual reality display

Publication Date: 2025.07.09 SNAP INC

Figure 1a~1c
Figure 1d~1e
Figure 2

AI summary

A waveguide (5002) for use in a virtual reality, VR, or augmented reality, AR, device, is disclosed. The waveguide (5002) comprising an input region (5006) configured to couple light into the waveguide (5002) so that it propagates under total internal reflection (TIR) within the waveguide (5002), and an output region (5008) comprising optical structures configured to receive image bearing light from the input region (5006). The output region (5008) comprises a plurality of zones (5010, 5012, 5014) having different diffraction to each other, the plurality of zones (5010, 5012, 5014) comprising diffraction efficiencies so as to reduce rainbow artefacts.