Multiplanar HMD Varifocal Focus for Vergence-Accommodation Alignment
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Solution Overview
Problem
Existing head-mounted displays (HMDs) cause visual fatigue and nausea due to an inability to correctly render or compensate for vergence and accommodation conflicts, which occur when the eyes converge on a point at a different depth from the focal plane of the displayed image.
Innovation Solution
A multiplanar head-mounted display with dynamically adjustable optical distances using varifocal systems to align convergence and accommodation by positioning multiple display planes at varying optical distances based on the user's gaze, tracked by eye movement and vergence detection, allowing simultaneous or sequential display of virtual planes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single fixed focal plane is used in existing HMDs, then the device structure is simple, but visual fatigue and nausea occur due to vergence-accommodation conflict
Solution Approach 1:
The patent divides the display system into multiple electronic displays (first electronic display and second electronic display) positioned at different optical distances from the optics block. Each display presents content for a different focal plane, allowing the system to segment the visual information across multiple depth planes. This segmentation resolves the vergence-accommodation conflict by providing separate focal planes for different depth cues.
Solution Approach 2:
The patent implements dynamic focus adjustment through a varifocal system that changes the focal length of the optics block based on detected user gaze. The system dynamically transitions between different focal planes (first optical distance and second optical distance) to match the user's accommodation needs with vergence cues, making the optical system adaptive rather than fixed.
2Reliability
If multiple display planes at different optical distances are implemented, then vergence and accommodation are aligned, but device complexity increases
Solution Approach 1:
The patent combines multiple electronic displays with the optics block to form an integrated optical system. The first and second electronic displays are positioned at different optical distances and work together with the varifocal optics block to present a unified multiplanar virtual scene. This merging allows the system to achieve vergence-accommodation alignment while consolidating components into a compact head-mounted form factor.
3Ease of operation
If the focal length is dynamically adjusted based on user gaze, then visual comfort is improved, but the system requires complex eye tracking and varifocal mechanisms
Solution Approach 1:
The patent implements a feedback loop where the system detects user gaze direction and vergence through eye tracking sensors, determines the appropriate focal plane based on this feedback, and dynamically adjusts the optics block's focal length accordingly. This closed-loop feedback system enables automatic focus adjustment that adapts to user viewing behavior, improving visual comfort without requiring manual intervention.
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 effectively reduces visual fatigue and nausea by aligning vergence and accommodation, providing a more comfortable and immersive virtual reality experience.
Implementation Method 1
a focal length of an optics block that directs image light from the electronic display elements towards the eyes of a user is adjusted using a varifocal system
Implementation Method 2
At least one of the electronic displays is at least semi-transparent to allow image light of the virtual scene to be combined for viewing by the user wearing the HMD
Data Source
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AI summary
A multiplanar head mounted display (HMD) includes two or more artificial display planes for each eye located at optical distances that can be dynamically adjusted based on a location within a scene presented by the HMD that the user views. For example, a scene is presented on two or more electronic display elements (e.g., screens) of the HMD. A focal length of an optics block that directs image light from the electronic display elements towards the eyes of a user is adjusted using a varifocal system (e.g., an element that mechanically changes a distance between a lens system in the optics block and the electronic display element, an element that changes shape of one or more lenses in the lens system in the optics block, etc.) based on a location or object within the scene where the user is looking.