Eye Tracking With Aspheric Cornea Models for Virtual Depth Alignment
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Solution Overview
Problem
Existing VR, AR, and MR technologies face challenges in providing a comfortable, natural-feeling presentation of virtual image elements amidst real-world imagery due to complexities in human visual perception, leading to issues like unstable imaging and eye strain.
Innovation Solution
A display system that projects light into a user's eye using a head-mounted device, equipped with eye tracking cameras and processing electronics, estimates the center of rotation of the eye based on corneal curvature using spherical and/or aspherical models, and adjusts virtual image content to correspond with the eye's depth perception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple eye tracking method is used, then device complexity is reduced, but measurement precision of eye center of rotation deteriorates
Solution Approach 1:
The patent changes the mathematical model parameters from simple spherical to aspheric corneal models, using higher-order polynomial coefficients (k3, k5, k7) to describe corneal curvature. This allows precise estimation of the eye's center of rotation without adding physical complexity to the tracking hardware, resolving the contradiction between device simplicity and measurement precision.
2Device complexity
If virtual images are displayed at fixed depth, then display system complexity is reduced, but user comfort and realism deteriorate
Solution Approach 1:
The patent implements dynamic depth adjustment of virtual images based on real-time eye accommodation data. The display system continuously adapts the focal plane of virtual content to match the user's actual eye focus, eliminating eye strain and enhancing realism while maintaining manageable system complexity through software-based dynamic rendering.
3Manufacturing precision
If corneal curvature is modeled as spherical, then manufacturing precision requirements are reduced, but measurement precision of corneal center deteriorates
Solution Approach 1:
The patent transitions from spherical to aspheric corneal models, introducing higher-order terms (k3, k5, k7 coefficients) that capture the true aspheric shape of the cornea. This mathematical enhancement improves corneal center estimation accuracy without requiring physically more precise manufacturing, as the model itself adapts to individual corneal geometries through parameter fitting.
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
Enhances the realism and comfort of VR, AR, and MR experiences by aligning virtual image depth with the user's accommodative response, reducing eye strain and providing credible depth cues.
Implementation Method 1
uses an aspheric model of the cornea in numerical calculations to determine a value or an estimate or a location of a center of curvature of the cornea
Implementation Method 2
one or more eye tracking cameras configured to image the user's eye
Data Source
AI summary
A display system can include a head-mounted display configured to project light to an eye of a user to display virtual image content at different amounts of divergence and collimation. The display system can include an inward-facing imaging system possibly comprising a plurality of cameras that image the user's eye and glints thereon and processing electronics that are in communication with the inward-facing imaging system and that are configured to obtain an estimate of a center of cornea and/or center of rotation of the user's eye, and/or other parameter(s), using data derived from the glint images. The display system may use spherical and/or aspheric cornea models to estimate a location of the corneal center of the user's eye and/or other parameter(s).