Boundary Region Glint Tracking for Eye Position Estimation
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Solution Overview
Problem
Designing an accurate eye tracking system for head-mounted displays in virtual and augmented reality applications is challenging due to power budget and form factor constraints, particularly in distinguishing reflection locations on the eye surface.
Innovation Solution
An eye tracking system that uses a plurality of emitters to illuminate the eye with a light pattern, producing glints on the boundary region between the sclera and cornea, which are captured by a camera and used by a controller to estimate the eye's position, employing polarization and time of flight to disambiguate reflection locations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional eye tracking methods are used in head-mounted displays, then gaze direction can be detected, but power consumption is high and form factor constraints are violated
Solution Approach 1:
The system segments the eye surface into distinct regions (cornea, sclera, boundary region) and uses multiple emitters to create separate glints on each region. By tracking the relative positions of these segmented glints rather than using complex traditional eye tracking hardware, the system achieves accurate gaze detection with reduced power consumption.
Solution Approach 2:
The system introduces glints as intermediary markers on the eye surface to indirectly measure gaze direction. Instead of directly measuring eye orientation with complex sensors, the emitters create light reflections (glints) that serve as mediators, whose positions encode the eye's orientation and gaze direction, enabling simpler and more power-efficient tracking.
2Measurement precision
If multiple emitters are used to illuminate the eye, then more glints are produced for better tracking, but it becomes harder to distinguish reflection locations on the eye surface
Solution Approach 1:
The system assigns different local qualities to different regions of the eye by illuminating specific areas (cornea, sclera, boundary region) with emitters positioned at different locations. Each emitter creates glints with distinctive characteristics based on its position and the local surface properties, enabling the system to distinguish reflection locations even with multiple emitters active simultaneously.
Solution Approach 2:
The system resolves reflection location ambiguity by adding spatial dimensionality - using the known three-dimensional positions of multiple emitters and analyzing the two-dimensional pattern of glints on the eye surface. This dimensional transformation allows the system to disambiguate which glint corresponds to which emitter by considering the geometric relationships in 3D space.
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 system effectively tracks the user's gaze with reduced bandwidth and power consumption, enabling accurate eye position estimation and gaze angle determination for enhanced VR/AR experiences.
Implementation Method 1
The light pattern produces a plurality of glints on a portion of the surface of the eye. The captured image includes a subset of the plurality of glints that are reflected by the boundary region.
Implementation Method 2
The camera captures an image of the portion of the eye. The captured image includes a subset of the plurality of glints that are reflected by the boundary region.
Implementation Method 3
employing polarization and time of flight to disambiguate reflection locations
Implementation Method 4
employing polarization and time of flight to disambiguate reflection locations
Data Source
AI summary
Embodiments relate to a head-mounted display including an eye tracking system. The eye tracking system includes a source assembly, a camera, and a controller. In some embodiments, the source assembly is a plurality of sources and are positioned to illuminate at least a peripheral area of a cornea of an eye. In some embodiments, the sources are masked to be a particular shape. The peripheral region is a location on the eye where the cornea transitions to the sclera. In some embodiments, the camera can detect a polarization of the reflected light, and uses polarization to disambiguate possible reflection locations. Similarly, time of flight may also be used to disambiguate potential reflection locations. The controller uses information from the detector to track positions of the user's eyes.