Varifocal Optics Block for VR Headset Vergence-Accommodation Conflict
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Solution Overview
Problem
Virtual reality headsets fail to correctly render depth and cause visual fatigue and nausea due to an inability to compensate for vergence and accommodation conflicts, leading to discomfort for users.
Innovation Solution
A virtual reality headset automatically adjusts its focus based on the user's gaze point within a virtual scene by using a varifocal element to change the focal length of the optics block, tracking eye positions, and refining vergence depth with geometric data, while dynamically adding depth of field blur for a more realistic rendering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed focal length optics block is used in the virtual reality headset, then the device structure is simple and manufacturing is easier, but vergence and accommodation conflicts cannot be compensated causing visual fatigue and nausea
Solution Approach 1:
The patent implements a varifocal optics block that dynamically adjusts its focal length based on the user's gaze point and vergence depth. The optics block transitions from a fixed focal length design to a dynamic adjustable design, allowing the focal length to change in real-time to match the user's viewing depth in the virtual scene, thereby compensating for vergence-accommodation conflicts and improving user comfort
Solution Approach 2:
The patent changes the optical parameter (focal length) of the optics block to resolve the contradiction. By adjusting the focal length parameter dynamically based on gaze tracking and vergence depth calculations, the system can compensate for vergence-accommodation conflicts without requiring complete redesign of the entire optics system, thus improving user comfort while controlling complexity
2Reliability
If the focal length is dynamically adjusted to track gaze point, then vergence and accommodation conflicts are compensated reducing visual fatigue, but the device complexity and control difficulty increase
Solution Approach 1:
The patent implements a feedback loop where the system continuously tracks the user's gaze point using eye tracking sensors, calculates the vergence depth based on gaze line intersections, and uses this information to dynamically adjust the focal length of the optics block. This closed-loop feedback system automatically compensates for vergence-accommodation conflicts, improving visual comfort while managing control complexity through automation
Solution Approach 2:
The system performs self-adjustment by automatically tracking the user's eyes, calculating the appropriate vergence depth, and adjusting the focal length without requiring manual user intervention. The gaze tracking and focal adjustment are seamlessly integrated, allowing the system to serve itself in maintaining proper focus alignment with the user's natural viewing behavior
3Extent of automation
If gaze tracking and vergence depth calculation are implemented, then the focus can be automatically adjusted to the user's viewing point, but the measurement precision requirements and processing complexity increase
Solution Approach 1:
The patent applies partial action by focusing measurement and adjustment efforts on the critical parameter of vergence depth rather than attempting to perfectly measure all aspects of eye movement. The system calculates vergence depth from gaze line intersections and uses this partial information to achieve sufficient focus adjustment accuracy, accepting that complete precision is not necessary for effective vergence-accommodation conflict compensation
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 mitigates vergence-accommodation conflicts, keeping users' eyes in a comfortable zone and enhancing the realism of the virtual environment by accurately focusing on the intended depth, reducing visual fatigue and nausea.
Implementation Method 1
a varifocal element (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.)
Data Source
AI summary
A virtual reality headset displays a three-dimensional (3D) virtual scene and includes a varifocal element to dynamically adjust a focal length of an optics block included in the virtual reality headset based on a location in the virtual scene where the user is looking. The headset tracks a user's eyes to approximate gaze lines and determines a plane of focus for a frame of the virtual scene as the intersection of the gaze lines. The varifocal element adjusts the focal length of the optics block so the optics block is focused at the plane of focus, which keeps the user's eyes in a zone of comfort as vergence and accommodation change. Based on the plane of focus, the virtual reality headset may provide depth cues, such as depth of field blur, to planes in the virtual scene deeper in the user's field of view than the plane of focus.