Curved Lens Light Guide with Embedded Outcoupler

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Solution Overview

Problem

Wearable heads-up displays face challenges in minimizing bulk while maintaining high visual quality and aesthetic appeal, often resulting in bulkier designs that obstruct the user's external environment.

Innovation Solution

The use of a surface relief grating-based outcoupler in a light guide with specific grating periods, duty cycles, and modulation heights to minimize second-order diffraction and maximize first-order diffraction efficiency, allowing for efficient exit pupil expansion and optical power compensation, thereby enhancing image quality and reducing bulk.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If large display components are used to maintain visual quality, then image quality is improved, but device bulk increases and aesthetic appeal deteriorates

Engineering Contradiction:

Improvevisual qualityVSAvoiddevice bulk

Core Design Contradiction:

Measurement precisionVSVolume of moving object

Solution Approach 1:

The light guide is embedded within the curved lens structure, nesting multiple optical components within a single integrated element. This reduces overall device bulk while maintaining the optical functionality required for high-quality display output.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The outcoupler uses specific grating parameters (grating period between 320-900 nm, duty cycle between 15-30% or 65-95%, modulation height between 20-100 nm) to optimize diffraction efficiency. By carefully controlling these parameters, the system achieves high visual quality with reduced optical component sizes.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If second-order diffraction is not minimized, then manufacturing is simpler, but ghost images increase and visual quality deteriorates

Engineering Contradiction:

Improveoutcoupler fabricationVSAvoidghost images

Core Design Contradiction:

Ease of manufactureVSObject-generated harmful factors

Solution Approach 1:

The outcoupler is designed with specific grating parameters including grating period (320-900 nm), duty cycle (15-30% or 65-95%), and modulation height (20-100 nm) to minimize second-order diffraction efficiency while maintaining first-order diffraction. This parameter optimization reduces ghost images without requiring complex manufacturing processes.

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 solution enables the creation of more aesthetically pleasing wearable heads-up displays with improved visual quality by minimizing second-order diffraction and maintaining high first-order diffraction efficiency, reducing ghost images and enhancing user experience.

Implementation Method 1

a surface relief grating-based outcoupler in a light guide with specific grating periods, duty cycles, and modulation heights to minimize second-order diffraction and maximize first-order diffraction efficiency

Methodology Applied

Scientific EffectDiffraction: Diffraction

Data Source

PatentUS11668931B2Systems, devices, and methods for exit pupil expansion in a curved lens with embedded light guide

Publication Date: 2023.06.06 GOOGLE LLC

AI summary

Systems, devices, and methods for for exit pupil expansion in a curved lens with embedded light guide are described. Exit pupil expansion in a curved lens may be achieved with a light guide comprising an outcoupler with minimized second order diffraction, where the outcoupler applies an optical power to outcoupled light.