Hybrid Waveguide Outcoupler Layout for Larger XR Eyebox

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Solution Overview

Problem

Conventional waveguides in extended reality eyewear displays face limitations due to restricted space within the waveguide form factor, leading to reduced eyebox size and diminished optical performance, particularly in the positioning and sizing of the exit pupil expander and outcoupler, which affects brightness and color uniformity.

Innovation Solution

A waveguide architecture incorporating a hybrid outcoupler and exit pupil expander region, along with a recycler region, optimizes the use of available space by allowing the outcoupler and exit pupil expander to functionally overlap, enhancing light propagation and efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If the waveguide form factor is maintained with conventional separate outcoupler and exit pupil expander regions, then the device complexity is reduced, but the eyebox size and optical performance are limited due to restricted space

Engineering Contradiction:

Improveeyebox sizeVSAvoidwaveguide structure complexity

Core Design Contradiction:

Area of stationary objectVSDevice complexity

Solution Approach 1:

The patent merges the outcoupler and exit pupil expander into a single hybrid region where both functions are performed simultaneously. The hybrid outcoupler and exit pupil expander region allows light to be both expanded and outcoupled in the same spatial location, effectively increasing the eyebox size without requiring additional separate components that would increase device complexity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The hybrid region serves multiple functions: it acts as both an exit pupil expander to increase the eyebox size and an outcoupler to direct light to the user's eye. This multi-functionality allows a single region to perform what would traditionally require two separate components, thereby increasing eyebox size while maintaining manageable device complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Illumination intensity

If the outcoupler and exit pupil expander are positioned separately to optimize each function, then the manufacturing precision is improved, but the brightness and color uniformity are reduced due to space constraints

Engineering Contradiction:

Improvebrightness and color uniformityVSAvoidpositioning accuracy of optical components

Core Design Contradiction:

Illumination intensityVSManufacturing precision

Solution Approach 1:

By combining the outcoupler and exit pupil expander into a hybrid region, the patent eliminates the need for precise positioning between two separate components. The merged structure ensures optimal light propagation paths and uniform color distribution across the eyebox while simplifying manufacturing requirements compared to aligning multiple separate optical elements.

Inventive Principle:

Principle #5Merging (Combining)

3Productivity

If the waveguide is designed with traditional separate regions for outcoupling and pupil expansion, then the ease of manufacture is improved, but the light propagation efficiency is reduced

Engineering Contradiction:

Improvelight propagation efficiencyVSAvoidmanufacturing simplicity

Core Design Contradiction:

ProductivityVSEase of manufacture

Solution Approach 1:

The hybrid outcoupler and exit pupil expander region increases light propagation efficiency by eliminating the need for light to travel between separate outcoupler and exit pupil expander components. This merged structure reduces optical path length and potential loss points, thereby improving productivity while remaining manufacturable through integrated fabrication processes.

Inventive Principle:

Principle #5Merging (Combining)

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 hybrid design improves brightness and color uniformity across the eyebox by increasing the amount of display light propagated to the user, addressing the limitations of conventional waveguides.

Implementation Method 1

the incoupled display light beams are 'guided' through the waveguide, typically by multiple instances of total internal reflection (TIR), expanded in at least one direction by an exit pupil expander

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Implementation Method 2

an outcoupler, which can also be formed as an optical grating on a surface of the waveguide

Methodology Applied

Scientific EffectDiffraction: Diffraction

Data Source

PatentUS20250341719A1Waveguide with hybrid outcoupler and exit pupil expander region

Publication Date: 2025.11.06 GOOGLE LLC

AI summary

A waveguide includes an incoupler to incouple light beams into the waveguide, an exit pupil expander to receive a first portion of the incoupled light beams and redirect the first portion of the incoupled light beams to an outcoupler, and an outcoupler to receive the redirected first portion of the incoupled light beams and outcouple the redirected first portion of the incoupled light beams from the waveguide. The outcoupler includes a section that receives a second portion of the incoupled light beams and redirects the second portion of the incoupled light beams to the exit pupil expander, and the exit pupil expander includes a section that receives the redirected second portion of the incoupled light beams and outcouples the redirected second portion of the incoupled light beams from the waveguide.