AR Eyepiece Grating Architecture for Higher Transmission

Solution Overview

Problem

Augmented reality eyepieces with high-index waveguides suffer from poor light transmission and noticeable back-reflection, which obstruct the user's view and compromise display performance.

Innovation Solution

Implementing secondary gratings with smaller pitch, either one-dimensional or two-dimensional, stacked on top of primary gratings to enhance transmission and reduce back-reflection without affecting display performance, using morphed or combined diffractive optical elements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of moving object

If high-index waveguides are used to achieve large field-of-view, then field-of-view is improved, but light transmission deteriorates and back-reflection increases

Engineering Contradiction:

Improvefield-of-viewVSAvoidlight transmission

Core Design Contradiction:

Area of moving objectVSIllumination intensity

Solution Approach 1:

The waveguide surface is segmented into multiple diffraction gratings with different pitch values. The first grating has a larger pitch optimized for field-of-view expansion, while the second grating has a smaller pitch optimized for reducing back-reflection and improving light transmission. This segmentation allows each grating to perform its specific function without compromising the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the waveguide surface are assigned different grating structures with locally optimized properties. The first grating regions provide large field-of-view characteristics, while the second grating regions provide anti-reflection characteristics. This local quality differentiation resolves the contradiction by allowing each area to excel at its specific function.

Inventive Principle:

Principle #3Local quality

2Area of moving object

If high-index waveguides are used to achieve large field-of-view, then field-of-view is improved, but back-reflection increases

Engineering Contradiction:

Improvefield-of-viewVSAvoidback-reflection

Core Design Contradiction:

Area of moving objectVSObject-generated harmful factors

Solution Approach 1:

The waveguide surface is segmented into multiple diffraction gratings with different pitch values. The first grating has a larger pitch optimized for field-of-view expansion, while the second grating has a smaller pitch optimized for reducing back-reflection and improving light transmission. This segmentation allows each grating to perform its specific function without compromising the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the waveguide surface are assigned different grating structures with locally optimized properties. The first grating regions provide large field-of-view characteristics, while the second grating regions provide anti-reflection characteristics. This local quality differentiation resolves the contradiction by allowing each area to excel at its specific function.

Inventive Principle:

Principle #3Local quality

3Illumination intensity

If additional secondary gratings are stacked on primary gratings, then transmission to reflection ratio is improved, but device complexity increases

Engineering Contradiction:

Improvetransmission to reflection ratioVSAvoidgrating structure complexity

Core Design Contradiction:

Illumination intensityVSDevice complexity

Solution Approach 1:

Multiple diffraction gratings with different functions are merged into a single integrated waveguide structure. The first grating for field-of-view expansion and the second grating for back-reflection reduction are combined in a way that they work together synergistically, improving the transmission to reflection ratio while avoiding the need for separate components.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The diffraction grating structure serves multiple functions simultaneously. The same grating structure that expands the field-of-view also reduces back-reflection when the second grating is added, creating a multi-functional optical element that improves performance without proportionally increasing complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 significantly improves the transmission to reflection ratio by up to 10 times, enhancing the clarity and brightness of augmented reality displays while maintaining image uniformity and reducing artifacts.

Implementation Method 1

The primary and secondary gratings can be one-dimensional (1D) or two-dimensional (2D). When multiple 1D or 2D gratings of small pitch, e.g., lattice periodicity of the gratings, are stacked on top of the primary diffraction gratings used for display of digital content

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 2

The waveguides used for an augmented reality eyepiece display have high refractive indices associated with a surface relief pattern and substrate, both of which are criteria for achieving a large field-of-view with good image brightness

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Data Source

PatentUS20250347907A1Highly transmissive eyepiece architecture

Publication Date: 2025.11.13 MAGIC LEAP INC

AI summary

An eyepiece includes a substrate, an input coupling grating on a first side of the substrate, and a morphed grating comprising characteristics of both a primary grating and a secondary grating on at least the first side of the substrate. The primary grating and the secondary grating may differ in pitch, orientation, and dimensions.