Waveguide Display Gratings Using EPS for Unpolarized Light Efficiency

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Solution Overview

Problem

Existing waveguide-based displays face challenges in achieving high efficiency and compactness, particularly when using unpolarized light sources like OLEDs, due to the inefficiency of P-polarization diffracting gratings, leading to a 50% loss in diffraction efficiency.

Innovation Solution

Incorporating evacuated periodic structures (EPS) as input, fold, and output gratings, which can efficiently diffract both S- and P-polarized light, utilizing high S-diffraction efficiency deep SRGs and VBGs, and optionally combining them with anti-reflection coatings and optical layers to enhance performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If conventional gratings are used in waveguide-based displays, then the structure is simple, but the diffraction efficiency for P-polarized light is low, resulting in 50% loss

Engineering Contradiction:

Improvediffraction efficiencyVSAvoidgrating structure complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent changes the physical parameters of the grating structure by evacuating the periodic structures to create air-filled cavities, transforming the refractive index modulation mechanism. This parameter change enables high diffraction efficiency for both S- and P-polarized light without requiring complex multi-layer architectures

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite structure combining solid polymer matrices with evacuated air cavities, forming a hybrid material system that leverages the refractive index contrast between solid and gas phases to achieve enhanced diffraction efficiency for unpolarized light

Inventive Principle:

Principle #40Composite materials

2Adaptability or versatility

If the waveguide display uses unpolarized light sources like OLEDs, then the light source is versatile and commonly available, but the overall diffraction efficiency is reduced by 50% due to P-polarization loss

Engineering Contradiction:

Improvelight source compatibilityVSAvoiddiffraction efficiency

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The evacuated periodic structure grating is designed to perform multiple functions: it efficiently diffracts both S- and P-polarized light, maintains compatibility with unpolarized light sources like OLEDs, and achieves high diffraction efficiency across different polarization states, making it universally applicable to common light sources

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Weight of stationary object

If the waveguide display is made compact and lightweight, then the user comfort and portability are improved, but the manufacturing complexity increases

Engineering Contradiction:

Improvewaveguide weightVSAvoidmanufacturing complexity

Core Design Contradiction:

Weight of stationary objectVSEase of manufacture

Solution Approach 1:

The patent segments the waveguide into distinct functional zones with gratings applied only at specific locations (input, fold, and output gratings), allowing for optimized material usage and simplified manufacturing processes while maintaining compact dimensions and lightweight construction

Inventive Principle:

Principle #1Segmentation

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 achieves up to 99% S-diffraction efficiency and improved overall diffraction efficiency for both polarizations, enabling compact and efficient waveguide-based displays.

Implementation Method 1

an input grating including an evacuated periodic structure (EPS) supported by the substrate, wherein the input grating diffracts light into total internal reflection (TIR) within the substrate

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 2

wherein the input grating diffracts light into total internal reflection (TIR) within the substrate

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Implementation Method 3

a fold grating including an EPS or a volume Bragg grating (VBG), wherein the fold grating receives the TIR light and expands the TIR light in a first direction

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 4

an output grating including an EPS or a VBG, wherein the output grating receives the expanded light and outputs the light, wherein the input grating is spatially separated from the fold grating and the output grating

Methodology Applied

Scientific EffectDiffraction: Diffraction

Data Source

PatentUS20260009934A1Waveguide-Based Displays Incorporating Evacuated Periodic Structures

Publication Date: 2026.01.08 DIGILENS INC

AI summary

Disclosed herein is a waveguide based display including: an optically transparent substrate; an input grating including an evacuated periodic structure (EPS) supported by the substrate, wherein the input grating diffracts light into total internal reflection (TIR) within the substrate; a fold grating comprising an EPS or a volume Bragg grating (VBG), wherein the fold grating receives the TIR light and expands the TIR light in a first direction; and an output grating including an EPS or a VBG. The output grating receives the expanded light and outputs the light and the input grating is spatially separated from the fold grating and the output grating.