Focus Tunable Lens for AR Vergence Accommodation Conflict
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Solution Overview
Problem
Augmented reality (AR) devices, such as AR glasses, cause eye strain due to vergence accommodation conflict, where the vergence distance and focal length of the eyes do not match, leading to discomfort during prolonged use.
Innovation Solution
An AR device with an optical engine, a waveguide, polarization converters, and a focus tunable lens that adjusts focal length to match the depth of virtual images with the user's gaze, allowing the device to alternate between displaying virtual and real scenes to reduce eye strain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If virtual images are displayed at a fixed depth using a waveguide, then the AR display function is achieved, but vergence accommodation conflict occurs causing eye strain
Solution Approach 1:
The patent applies a focus tunable lens that dynamically adjusts its focal length based on the depth of virtual images. When virtual images are displayed at different depths, the lens focal length is tuned accordingly to match the vergence distance, thereby resolving the vergence accommodation conflict and reducing eye strain while maintaining reliable AR display functionality.
2Adaptability or versatility
If multiple virtual image layers at different depths are displayed simultaneously, then comprehensive AR information is provided, but system complexity increases
Solution Approach 1:
The focus tunable lens enables dynamic adjustment of focal length to match different virtual image depths. This allows the system to display multiple virtual image layers at different depths by sequentially tuning the lens focal length, achieving comprehensive AR information display without requiring complex optical systems for each depth layer.
Solution Approach 2:
The system displays multiple virtual image layers at different depths by periodically adjusting the focus tunable lens focal length corresponding to each depth layer. This periodic focal adjustment enables comprehensive multi-depth AR display while maintaining relatively simple optical system architecture.
3Object-affected harmful factors
If the focus tunable lens continuously adjusts focal length, then vergence accommodation conflict is resolved, but energy consumption increases
Solution Approach 1:
The focus tunable lens adjusts its focal length periodically only when virtual images at different depths are displayed, rather than continuously. This periodic adjustment resolves vergence accommodation conflict for multi-depth AR content while minimizing energy consumption by keeping the lens static during periods when focal adjustment is not required.
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 device effectively reduces eye strain by aligning the focal length with the depth of virtual images, preventing vergence accommodation conflict and allowing users to view both virtual and real scenes without discomfort.
Implementation Method 1
a polarization converter configured to maintain or convert a polarization direction of light
Implementation Method 2
a focus tunable lens of which a focal length for the light of the virtual image output from the waveguide is adjusted
Data Source
AI summary
An electronic device for displaying augmented reality (AR) includes: an optical engine configured to output light of virtual image; a waveguide from which the light of the virtual image is output and through which light of a real scene is transmitted; an optical shutter configured to transmit or block the light of the real scene; a focus tunable lens configured to adjust a focal length for the light of the virtual image output from the waveguide; and one or more processors configured to, during a first period, control the optical shutter to block at least part of a first light of the real scene, and control the focus tunable lens to have a first focal length, and during a second period, control the optical shutter to transmit a second light of the real scene, and control the focus tunable lens to have a second focal length different from the first focal length.