AR Optical Waveguide Grating Brightness Uniformity

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Solution Overview

Problem

Existing optical waveguide systems in AR technology suffer from uneven light efficiency and brightness distribution within the pupil, due to uniform diffraction efficiency across coupling-out gratings.

Innovation Solution

The optical waveguide structure incorporates coupling-out gratings with varying diffraction efficiencies, arranged to maintain consistent image light brightness across the pupil, achieved through surface relief or volume holographic gratings with different duty cycles, inclinations, and refractive indexes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If uniform diffraction efficiency is used across all coupling-out gratings, then the device complexity is reduced, but the light efficiency and brightness distribution within the pupil become uneven

Engineering Contradiction:

Improvecomplexity of coupling-out gratingsVSAvoidbrightness distribution within pupil

Core Design Contradiction:

Device complexityVSIllumination intensity

Solution Approach 1:

The patent applies local quality by making each coupling-out grating have different diffraction efficiency characteristics tailored to its specific position in the optical path. This ensures that each grating compensates for the cumulative reflection losses at its location, achieving uniform brightness across the pupil while maintaining a relatively simple overall structure.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the diffraction efficiency parameter of each coupling-out grating based on its position. By adjusting this parameter, the system compensates for varying light losses due to total internal reflections at different stages, thereby achieving uniform light intensity distribution without significantly increasing device complexity.

Inventive Principle:

Principle #35Parameter changes

2Illumination intensity

If multiple coupling-out gratings with different diffraction efficiencies are used, then the light efficiency and brightness uniformity are improved, but the manufacturing precision requirements increase

Engineering Contradiction:

Improveuniformity of light intensity within pupilVSAvoidprecision of grating fabrication

Core Design Contradiction:

Illumination intensityVSManufacturing precision

Solution Approach 1:

The patent segments the coupling-out grating system into multiple discrete gratings, each with optimized diffraction efficiency for its specific position. This segmentation allows for systematic control of light distribution while enabling standardized manufacturing processes for each segment, balancing precision requirements with manufacturing feasibility.

Inventive Principle:

Principle #1Segmentation

3Productivity

If diffraction efficiency is optimized for each coupling-out grating, then the overall light efficiency is improved, but the device complexity increases

Engineering Contradiction:

Improvelight efficiency of optical waveguide structureVSAvoidcomplexity of grating configuration

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent optimizes the diffraction efficiency parameter for each coupling-out grating based on its position in the optical path. This parameter optimization maximizes overall light efficiency by compensating for cumulative reflection losses, while the systematic approach to parameter selection keeps the increase in device complexity manageable.

Inventive Principle:

Principle #35Parameter changes

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

This approach ensures uniform light intensity distribution within the pupil, enhancing the overall light efficiency and in-eye brightness of the AR device by optimizing the diffraction and reflection efficiencies of the coupling-out gratings.

Implementation Method 1

a coupling-in grating disposed at the optical waveguide body, wherein the coupling-in grating is configured to couple image light into the optical waveguide body

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 2

the optical waveguide body is configured to generate a total internal reflection of the image light to the coupling-out gratings

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Implementation Method 3

diffraction efficiencies of each of the coupling-out gratings are different, and each of the coupling-out gratings is configured to couple the image light out of the optical waveguide body

Methodology Applied

Scientific EffectDiffraction: Diffraction

Data Source

PatentUS12222507B2Optical waveguide structure, AR device, and method for obtaining emergent light efficiency of optical waveguide structure

Publication Date: 2025.02.11 BEIJING BOE DISPLAY TECH CO LTD

AI summary

Provided are an optical waveguide structure, an Augmented Reality (AR) device, and a method for obtaining an emergent light efficiency of an optical waveguide structure, which relates to the technical field of display. The optical waveguide structure includes: an optical waveguide body, a coupling-in grating disposed at the optical waveguide body, and a plurality of coupling-out gratings distributed and arranged. The coupling-in grating is configured to couple image light into the optical waveguide body. The optical waveguide body is configured to generate a total internal reflection of the image light to the coupling-out gratings. Diffraction efficiencies of each of the coupling-out gratings are different, and each of the coupling-out gratings is configured to couple the image light out of the optical waveguide body at the same brightness.