Waveguide Facet Layout for Compact Near-Eye Optical Coupling

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Solution Overview

Problem

Existing optical systems for near-eye displays face challenges in minimizing the size of optical components while maintaining a given angular field of view, particularly in shallow-angle implementations, due to inefficient coupling-in configurations and unnecessary attenuation of image illumination.

Innovation Solution

The optical system employs a light-guide optical element (LOE) with optimized deployment of partially-reflecting surfaces, including a coupling-in prism with specific orientations and dimensions, and a refined concave polygon design for facet locations, reducing unnecessary reflections and minimizing component size.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If traditional coupling-in configurations are used in shallow-angle implementations, then the angular field of view can be achieved, but the size of optical components increases and image illumination is unnecessarily attenuated

Engineering Contradiction:

Improveimage illumination efficiencyVSAvoidoptical component size

Core Design Contradiction:

Illumination intensityVSVolume of stationary object

Solution Approach 1:

The patent applies local quality by optimizing the coupling-in prism geometry and facet orientations in specific regions of the waveguide. The first and second sets of facets are positioned and angled differently to locally control light propagation paths, enabling efficient image illumination delivery to the eye-motion box while minimizing overall component size.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent utilizes three-dimensional facet arrangements within the waveguide thickness dimension. By positioning facets at different depths and angles in 3D space, the system achieves efficient shallow-angle coupling without increasing the lateral footprint of optical components, effectively using the thickness dimension to resolve the size-efficiency contradiction.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Adaptability or versatility

If multiple partially-reflecting surfaces are deployed to expand aperture in two dimensions, then the field of view is improved, but unnecessary reflections and attenuation occur

Engineering Contradiction:

Improvefield of view coverageVSAvoidimage illumination loss

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The patent segments the aperture expansion function into two distinct sets of facets with different orientations. The first set of facets handles one dimension of aperture expansion while the second set handles the other dimension, allowing each set to be optimized for its specific function and reducing unnecessary reflections compared to a single comprehensive reflecting surface.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent converts what would normally be harmful multiple reflections into beneficial controlled reflections by carefully designing the facet orientations and positions. The shallow-angle reflections that would typically cause loss are redirected through precise facet angling to deliver illumination efficiently to the eye-motion box, turning potential energy loss into useful light delivery.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Use of energy by moving object

If the coupling-in prism thickness is increased to improve coupling efficiency, then image illumination is enhanced, but the component size increases

Engineering Contradiction:

Improvecoupling efficiencyVSAvoidprism thickness

Core Design Contradiction:

Use of energy by moving objectVSLength of moving object

Solution Approach 1:

The patent optimizes the coupling-in prism thickness to a specific range that balances coupling efficiency with compactness. By carefully selecting the thickness parameter and combining it with optimized facet angles and positions, the system achieves effective shallow-angle coupling without requiring excessive prism thickness, thus maintaining a compact overall size.

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 design enhances the efficiency of image illumination propagation, reduces component size, and minimizes unwanted reflections, resulting in a more compact and effective near-eye display system.

Implementation Method 1

image illumination propagating within the LOE by internal reflection at the major external surfaces

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Implementation Method 2

second set of planar, mutually-parallel, partially-reflecting surfaces

Methodology Applied

Scientific EffectPartial reflection: Reflection

Data Source

PatentUS20260029659A1Optical System

Publication Date: 2026.01.29 LUMUS LTD

AI summary

An optical system employs a waveguide including a first set of partially-reflecting surfaces (“facets”) for progressively redirecting image illumination propagating from a coupling-in region towards a second region, and a second set of facets in the second region for progressively coupling-out the redirected image illumination towards the eye of a viewer. The first set of facets includes at least a first facet close to the coupling-in region, a third facet fare from the coupling-in region, and a second facet located on a medial plane between the first and the third facets. The second facet is located in a subregion of the medial plane such that image illumination propagating from the coupling-in region to the third facet passes through the medial plane without passing through the second facet.