Head-Mounted Imaging Device With Patterned Waveguide Interface

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Solution Overview

Problem

Conventional augmented reality systems face challenges in increasing field-of-view (FOV) while maintaining a compact and lightweight design, and reducing sensitivity to eye movements, which is critical for head-mounted applications.

Innovation Solution

A compact light-guide optical element (LOE) using a waveguide configured for total internal reflection, with a patterned interface to create a pseudo air layer between the waveguide and additional optical elements, allowing for effective angular sensitive reflections and maintaining image quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If the field-of-view (FOV) is increased in conventional augmented reality systems, then the imaging quality is improved, but the optical module becomes larger, heavier and bulkier

Engineering Contradiction:
Improvefield-of-viewVSAvoidoptical module weight
Core Design Contradiction:
Area of stationary objectVSWeight of stationary object

Solution Approach 1:

The optical element is embedded within the waveguide substrate, with the waveguide acting as a light guide and the optical element integrated into its structure. This nesting allows the optical module to maintain compact dimensions while achieving wide field-of-view through the waveguide's light guiding properties

Inventive Principle:
Principle #7Nested doll (Nesting)

Solution Approach 2:

The waveguide substrate serves as a thin, flexible light guiding structure that can be integrated into head-mounted displays. The waveguide's thin film nature allows for compact optical module design while maintaining the necessary optical path length for wide field-of-view imaging

Inventive Principle:
Principle #30Flexible shells and thin films

2Area of stationary object

If the field-of-view (FOV) is increased in conventional augmented reality systems, then the imaging quality is improved, but the optical module becomes bulkier

Engineering Contradiction:
Improvefield-of-viewVSAvoidoptical module volume
Core Design Contradiction:
Area of stationary objectVSVolume of stationary object

Solution Approach 1:

The optical element is embedded within the waveguide substrate, utilizing the waveguide's internal light guiding structure. This integration eliminates the need for separate bulk optical components, achieving wide field-of-view while maintaining compact optical module volume

Inventive Principle:
Principle #7Nested doll (Nesting)

Solution Approach 2:

The waveguide replaces traditional mechanical optical paths with a light guiding structure based on total internal reflection. This substitution allows for more compact optical design while achieving the necessary light propagation paths for wide field-of-view imaging

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

3Ease of manufacture

If conventional optical modules are used in head-mounted displays, then the system is easier to manufacture, but the device becomes heavier and bulkier

Engineering Contradiction:
Improvemanufacturing simplicityVSAvoidhead-mounted device weight
Core Design Contradiction:
Ease of manufactureVSWeight of moving object

Solution Approach 1:

The waveguide and optical element are combined into a single integrated structure where the optical element is embedded within the waveguide substrate. This merging reduces the overall device weight while maintaining manufacturing feasibility through integrated fabrication processes

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The invention changes the refractive index parameters by using a waveguide substrate with higher refractive index than the surrounding medium, enabling total internal reflection and compact light guiding. This parameter change allows for lightweight design while maintaining optical performance

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 solution enables wide FOVs and large eye-motion-box values, providing high-quality images with reduced bulkiness and sensitivity to eye movements, making it suitable for compact head-mounted displays.

Implementation Method 1

a light-transmitting waveguide substrate configured for receiving input light indicative of an image being projected, guiding said input light by total internal reflection

Methodology Applied
Scientific EffectTotal internal reflection: Total Internal Reflection

Implementation Method 2

an interface region between at least a portion of a surface of said waveguide substrate and a surface of the optical element being a patterned interface configured to provide optical coupling between the waveguide substrate and said optical element while maintaining the total internal reflection condition of light propagation within said light-transmitting waveguide

Methodology Applied
Scientific EffectTotal internal reflection: Total Internal Reflection

Data Source

PatentEP3458898B1Head-mounted imaging device
Publication Date: 2023.02.15 LUMUS LTD
  • EP3458898B1 patent drawingFigure 1
  • EP3458898B1 patent drawingFigure 2~3
  • EP3458898B1 patent drawingFigure 4~5

AI summary

An optical system is provided, for use in an electronic device, for example of the kind utilizing a head up display system. The optical system comprising: a light-transmitting waveguide substrate configured for receiving input light indicative of an image being projected, guiding said input light s by total internal reflection, and coupling the light out of the substrate to propagate along an output path in a predetermined direction; at least one transparent optical element accommodated in said output path and interfacing at least a portion of a surface of said waveguide substrate; an interface region between at least a portion of the surface of said waveguide substrate and a surface of the optical element being a patterned interface configured to provide optical coupling between the waveguide substrate and said optical element while maintaining the total internal reflection condition R of light propagation within said light-transmitting waveguide.