Waveguide Edge Absorbers Using Nanotube Films to Reduce Ghosting

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Solution Overview

Problem

Existing waveguides in augmented reality systems suffer from ghosting and low contrast ratios due to recirculated light, which affects the quality of displayed images.

Innovation Solution

Incorporating light absorbers made of carbon and silicon, such as thin films of carbon nanotubes or black silicon, onto the waveguide surfaces to absorb a significant portion of incident light, reducing recirculated light and improving image quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If light absorbers are incorporated onto waveguide surfaces, then contrast ratio and image quality are improved, but device complexity and manufacturing difficulty increase

Engineering Contradiction:

Improveimage qualityVSAvoiddevice complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent changes the optical parameters of the waveguide system by introducing light-absorbing materials with specific absorption coefficients and thicknesses. By controlling the absorption properties (parameter changes), the contrast ratio is improved from poor to good levels, resolving the technical contradiction between manufacturing simplicity and image quality.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite material structures by combining the waveguide material with light-absorbing materials (such as chromium, aluminum, or carbon-based materials). This composite approach allows the system to maintain the waveguide's light-guiding function while adding light absorption capabilities, thereby improving image quality without fundamentally redesigning the entire device.

Inventive Principle:

Principle #40Composite materials

2Reliability

If light absorbers are incorporated onto waveguide surfaces, then ghosting is reduced, but manufacturing process complexity increases

Engineering Contradiction:

Improveghosting reductionVSAvoidmanufacturing process

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent extracts the harmful recirculated light from the system by introducing light absorbers that selectively remove unwanted light paths. By taking out the problematic recirculated light while preserving the desired light guidance function, ghosting is reduced without requiring a complete redesign of the waveguide manufacturing process.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The light absorbers are applied locally at specific positions on the waveguide surfaces where recirculated light problems occur, rather than uniformly across the entire waveguide. This localized application reduces ghosting in critical areas while minimizing the impact on manufacturing complexity and maintaining ease of production.

Inventive Principle:

Principle #3Local quality

3Loss of energy

If light absorbers are incorporated onto waveguide surfaces, then recirculated light is reduced, but manufacturing precision requirements increase

Engineering Contradiction:

Improverecirculated lightVSAvoidmanufacturing precision

Core Design Contradiction:

Loss of energyVSManufacturing precision

Solution Approach 1:

The patent controls the light absorption efficiency by adjusting parameters such as absorber material type, thickness, and deposition uniformity. By optimizing these parameters, the system achieves effective reduction of recirculated light while maintaining manufacturable precision levels that are practical for production environments.

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

The light absorbers increase the contrast ratio and reduce ghosting, resulting in higher-quality displayed images with improved clarity and reduced recirculated light.

Implementation Method 1

the light absorber may comprise a thin film that absorbs a significant portion of incident light

Methodology Applied

Scientific EffectLight absorption: Absorption (EM radiation)

Data Source

PatentEP4235232B1Waveguides with light absorbing films and processes for forming the same

Publication Date: 2026.02.25 MAGIC LEAP INC

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AI summary

An optical device comprising one or more optical waveguides (1310), wherein each optical waveguide comprises a first major surface (1311) and a second major surface (1312), a first edge surface (1313) and a second edge surface (1315), and one or more diffractive incoupling optical elements and one or more diffractive outcoupling optical elements on at least one of the first and second major surfaces (1311, 1312) of the waveguide; a first light absorber (1320) directly on the first edge surface (1313), wherein the first light absorber (1320) comprises a vertically aligned nanotube array, wherein nanotubes of the nanotube arrays extend normal to the first edge on which the nanotubes are disposed; and optionally, a second light absorber (1320) directly on the second edge surface (1315), wherein the second light absorber (1320) comprises a vertically aligned nanotube array, wherein nanotubes of the nanotube arrays extend normal to the second edge on which the nanotubes are disposed.