Binocular AR Display Variable Focus Waveguide

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Solution Overview

Problem

Augmented reality systems face challenges in providing a mixed-reality display that naturally integrates with the user's external environment, leading to user discomfort due to difficulties in focusing on generated images relative to real-world objects.

Innovation Solution

A binocular augmented reality display system that renders and projects separate images to each eye from different perspectives, allowing for stereo fusion at a binocular convergence distance, with variable focus mechanisms to match the convergence and focal distances within a predetermined tolerance, ensuring the augmented reality image is perceived naturally and in sync with the external environment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a generated augmented reality image is positioned to match real-world objects, then the user experience is improved, but the user experiences discomfort due to focus adjustment between the augmented image and physical surroundings

Engineering Contradiction:
Improveuser experienceVSAvoideye strain and nausea
Core Design Contradiction:
Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The patent changes the optical parameters of the system by introducing variable focus mechanisms that can adjust the focal distance of the augmented reality image. This allows the focal distance to be dynamically modified to match the convergence distance, resolving the focus adjustment conflict that causes eye strain and nausea while maintaining natural integration with the external environment.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent implements dynamic adjustment capabilities through variable focus mechanisms that can continuously or discretely change the focal distance. This dynamic system adapts to different convergence distances, allowing the augmented reality image to maintain both natural positioning and comfortable focus conditions throughout the user's viewing experience.

Inventive Principle:
Principle #15Dynamics

2Manufacturing precision

If the focal distance is precisely matched to the convergence distance, then the image quality is optimized, but the device complexity increases due to additional control mechanisms

Engineering Contradiction:
Improveimage qualityVSAvoidcontrol system complexity
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent applies partial action by implementing variable focus mechanisms with a limited number of discrete power states rather than continuous adjustment. This provides sufficient focus matching capability to optimize image quality within acceptable tolerances while avoiding the complexity of fully continuous control systems. The predetermined minimum and maximum values define a practical adjustment range that achieves the desired precision without excessive complexity.

Inventive Principle:
Principle #16Partial or excessive action

Solution Approach 2:

The patent modifies the focal distance parameter through variable focus mechanisms that can adjust between predetermined minimum and maximum values. This parameter change capability allows the system to match the convergence distance within acceptable tolerances, optimizing image quality while maintaining manageable device complexity through defined adjustment boundaries.

Inventive Principle:
Principle #35Parameter changes

3Device complexity

If the augmented reality image is positioned at a fixed focal distance, then the device complexity is reduced, but the adaptability to different convergence distances is limited

Engineering Contradiction:
Improvefocus mechanism simplicityVSAvoidflexibility in focal distance adjustment
Core Design Contradiction:
Device complexityVSAdaptability or versatility

Solution Approach 1:

The patent transforms the static focal distance into a dynamic parameter through variable focus mechanisms. These mechanisms can adjust the focal distance to match different convergence distances, providing adaptability to various viewing conditions and augmented reality image positions while maintaining relatively simple device architecture through discrete power states.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The patent implements multi-functionality by designing variable focus mechanisms that can serve multiple convergence distance requirements within a single device. The mechanisms can adjust between predetermined minimum and maximum focal distances, allowing the same hardware to adapt to different augmented reality scenarios without requiring multiple specialized components.

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

This approach creates a three-dimensional augmented reality image that engages naturally with the external environment, reducing eye strain and nausea by maintaining image quality within the limits of human sensitivity, allowing for flexible focal distance adjustments without significant degradation.

Implementation Method 1

Diffraction gratings are positioned on or in the waveguides to couple light from a projector into a waveguide. A further diffraction grating structure can then be used to couple light out of the waveguide and towards a user.

Methodology Applied
Scientific EffectDiffraction: Diffraction

Implementation Method 2

The first diffractive optical element and the first diffractive optical element are positioned at an internal surface of a first waveguide. The waveguide structure guides light through total internal reflection from the input surface to the output surface.

Methodology Applied
Scientific EffectTotal internal reflection: Total Internal Reflection

Data Source

PatentEP3911991B1Augmented reality system
Publication Date: 2024.04.17 SNAP INC
  • EP3911991B1 patent drawingFigure 1
  • EP3911991B1 patent drawingFigure 2a~2b
  • EP3911991B1 patent drawingFigure 3a~3b

AI summary

A binocular augmented reality display system (2) is disclosed for focussing light from a first projector (4) and a second projector (6). The system includes the first projector (4) and the second projector (6) with first and second variable focus mechanisms respectively, and the first and second projectors are configured to project light to first and second waveguide assemblies of the system respectively. The first and second waveguide assemblies are each configured to outcouple light toward a user in order to present a common augmented reality image to the user, and the system further comprises a control system (3) configured to position the common augmented reality image at a binocular convergence distance and to control the first and second variable focus mechanisms so that the common augmented reality image is provided at a focal distance within predetermined minimum and maximum values on either side of the binocular convergence distance.