Gaze-Directed Variable Focus Lenses for AR VAC Mitigation
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Solution Overview
Problem
Augmented reality (AR) devices cause vergence-accommodation conflict (VAC), leading to user discomfort such as dizziness and motion sickness due to inconsistencies between focal length and vergence distance when viewing virtual images.
Innovation Solution
The AR device employs a variable focus lens system with electrically tunable liquid crystal lenses and eye trackers to adjust the refractive power and position of focus adjustment regions based on the user's gaze direction, aligning the focal length of virtual and real-world objects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed focal length lens is used in the AR device, then the device structure is simple, but the vergence-accommodation conflict causes user discomfort such as dizziness and motion sickness
Solution Approach 1:
The patent employs variable focus lenses that can dynamically adjust their focal length based on the user's gaze direction and distance. The lens system transitions from a fixed focal length configuration to a dynamic, adjustable focal length configuration, allowing the AR device to adapt to different viewing conditions and eliminate the vergence-accommodation conflict that causes user discomfort
Solution Approach 2:
The patent changes the optical parameters of the lens system by using variable focus lenses with adjustable refractive power. The focal length parameter is made variable rather than fixed, allowing the system to match the focal length with the vergence distance for different gaze directions, thereby resolving the VAC issue without significantly increasing device complexity
2Object-affected harmful factors
If the focal length is adjusted to match vergence distance, then user comfort is improved, but the device requires variable focus lenses and eye tracking systems increasing complexity
Solution Approach 1:
The patent applies local quality by using eye tracking to determine the user's gaze direction and adjusting the focal length specifically for the region of interest. Instead of adjusting the entire lens uniformly, the system focuses computational and optical resources on the local area where the user is looking, optimizing comfort while managing system complexity
Solution Approach 2:
The patent implements a feedback loop where the eye tracking system continuously monitors the user's gaze direction and provides this information to the variable focus lens control system. This closed-loop feedback enables real-time adjustment of the focal length to match the vergence distance, improving user comfort while maintaining manageable device complexity through intelligent control
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 effectively reduces user discomfort by aligning the focal length of virtual objects with real-world objects, enhancing clarity and reducing dizziness and motion sickness.
Implementation Method 1
each of the first variable focus lenses and each of the second variable focus lenses is an electrically tunable liquid crystal lens
Implementation Method 2
adjust a refractive power of the first focus adjustment region and a refractive power of a third focus adjustment region based on the gaze point
Data Source
AI summary
An augmented reality (AR) device including a variable focus lens of which a focal length may be changed by adjusting refractive power and adjusting the position of a focus adjustment region of the variable focus lens according to a direction of the user's view. The AR device may obtain an eye vector indicating a direction of the user's view using an eye tracker, adjust a refractive power of a first focus adjustment region of a first variable focus lens to change a focal length for displaying a virtual image, and complementarily adjust a refractive power of a second focus adjustment lens with respect to the adjusted refractive power of the first focus adjustment region.