Holographic Waveguide Light Control Layer for Grating Haze

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Solution Overview

Problem

Scatter from particulates in holographic gratings, particularly HPDLC gratings, leads to haze, reducing image contrast, color fidelity, and brightness uniformity, with a significant portion entering the eye box.

Innovation Solution

A waveguide display incorporating a light control layer that blocks non-image light, such as haze, while allowing high transmission of external light, using regions with reflection characteristics dependent on spectral bandwidth, incidence angle range, and polarization state, applied to the waveguide's external surfaces to divert or block scattered light from entering the eye box.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If holographic gratings are used for beam folding and expansion, then beam routing and expansion are achieved, but haze is generated due to scattering from particulates

Engineering Contradiction:

Improvebeam routing capabilityVSAvoidhaze

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

A light control layer is introduced as an intermediary component between the gratings and the eye box. This layer selectively blocks scattered light (haze) while allowing direct image-forming light to pass through, thereby mediating between the beam routing function and the haze problem.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The light control layer is positioned specifically at locations where scattered light would enter the eye box, applying the light-blocking function locally rather than uniformly across the entire waveguide. This targeted approach maintains image quality while reducing haze in critical viewing zones.

Inventive Principle:

Principle #3Local quality

2Object-affected harmful factors

If light control layer is added to block scattered light, then image contrast is improved, but device complexity increases

Engineering Contradiction:

Improveimage contrastVSAvoidwaveguide structure

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The light control layer is implemented as a thin film structure that can be applied to the waveguide surface, rather than a bulky mechanical component. This film-based approach improves image contrast while adding minimal structural complexity and maintaining device compactness.

Inventive Principle:

Principle #30Flexible shells and thin films

3Object-affected harmful factors

If light control layer blocks scattered light, then color fidelity is improved, but transmission of external light may be reduced

Engineering Contradiction:

Improvecolor fidelityVSAvoidlight transmission

Core Design Contradiction:

Object-affected harmful factorsVSLoss of energy

Solution Approach 1:

The light control layer is designed with specific optical parameters (wavelength selectivity, angular dependence) that allow it to block scattered light across the visible spectrum while maintaining high transmission for direct light paths. This parameter optimization ensures color fidelity improvement without significant energy loss.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The light control layer replicates the spectral and angular characteristics of the desired light paths, allowing it to distinguish between direct image-forming light (which should pass) and scattered light (which should be blocked), thereby preserving color fidelity and transmission efficiency.

Inventive Principle:

Principle #26Copying

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

Enhances image contrast, color fidelity, and brightness uniformity by effectively blocking scattered light, thereby improving the overall display quality.

Implementation Method 1

said light control layer is operative to divert or block scattered light from said set of gratings that might otherwise enter said eyebox

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 2

a set of gratings configured to: direct said data modulated light into a total internal reflection path in said waveguide

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Implementation Method 3

provide beam expansion and extraction of data modulated light from said waveguide into an eyebox

Methodology Applied

Scientific EffectDiffraction: Diffraction Grating

Data Source

PatentUS20250306367A1Holographic Waveguide Display with Light Control Layer

Publication Date: 2025.10.02 DIGILENS INC

AI summary

Waveguides and waveguide displays having a layer for blocking non-image light (i.e. haze) that could otherwise reduce contrast and degrade color gamut and uniformity, while providing high transmission to external light are provided. Many waveguides and displays incorporate at least one light control layer applied to at least one external surface of said waveguide and overlapping at least a portion of said at least one grating, to divert or block scattered light from said set of gratings that might otherwise enter said eyebox.