Waveguide Eye Position Tracking via Corneal Reflections in Compact Wearables
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Solution Overview
Problem
Existing eye-tracking sensors in AR/VR devices are bulky, energy-intensive, and vulnerable to ambient light, making them unsuitable for reliable user gaze direction tracking.
Innovation Solution
A waveguide optical system using collimated light sources to irradiate a light pattern on the cornea, with a sensor waveguide to detect and determine gaze direction, employing diffractive optical elements for efficient light guidance and a detector to analyze the reflected pattern.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a camera is used to register eye position in wearable devices, then eye tracking can be enabled, but the device size increases and energy consumption rises
Solution Approach 1:
The patent replaces the mechanical camera-based eye tracking system with a waveguide optical system that uses light reflection and total internal reflection principles. This substitution eliminates the need for bulky camera modules while maintaining eye tracking functionality through optical detection of corneal reflections.
Solution Approach 2:
The patent employs thin waveguide films to guide and detect light for eye tracking. These thin film structures enable compact integration into wearable devices while providing sufficient optical path length for reliable eye position detection through total internal reflection.
2Reliability
If a camera is used to register eye position, then eye tracking can be enabled, but energy consumption increases
Solution Approach 1:
The patent replaces the energy-intensive camera-based system with a passive optical waveguide system that utilizes natural light reflection from the cornea. This substitution dramatically reduces power consumption by eliminating the need for active imaging sensors and complex image processing.
Solution Approach 2:
The waveguide system utilizes the cornea itself as a reflective surface, requiring no external illumination or active sensing components. The system passively detects eye position through total internal reflection of ambient or display-generated light, making the eye structure serve the tracking function.
3Reliability
If a camera is used to register eye position, then eye tracking can be enabled, but the sensor becomes vulnerable to ambient light
Solution Approach 1:
The patent replaces the camera-based system that is sensitive to ambient light with a waveguide optical system that uses total internal reflection. This substitution creates an optical path that is inherently isolated from external light interference, as the waveguide confines light through physics-based reflection principles.
Solution Approach 2:
The waveguide acts as an intermediary optical element that separates the detection path from the ambient environment. By guiding light through total internal reflection within the waveguide structure, the system isolates the detection process from harmful ambient light while maintaining sensitivity to corneal reflection changes.
4Reliability
If a camera is used to register eye position, then eye tracking can be enabled, but the sensor obstructs the user's field of view
Solution Approach 1:
The patent uses thin waveguide films that can be positioned close to the eye without creating significant visual obstruction. These thin films allow light to pass through while enabling optical detection, maintaining a clear field of view for the user.
Solution Approach 2:
The patent moves the detection function from a spatially intrusive camera positioned in the user's field of view to a waveguide system that operates in a different optical dimension. The waveguide detects eye position through light reflection at the corneal surface, eliminating the need for blocking optical paths.
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 provides compact, low-energy, and safe eye-tracking that does not obstruct the user's view, offering reliable gaze direction determination for various wearable devices.
Implementation Method 1
a sensor waveguide configured to guide at least part of the light pattern reflected from the cornea surface to a detector
Implementation Method 2
employing diffractive optical elements for efficient light guidance
Implementation Method 3
a detector configured to detect at least part of the light pattern guided by the sensor waveguide and to obtain a mapping image corresponding to the at least part of the light pattern
Data Source
AI summary
A method of eye tracking includes: irradiating a light pattern, output from at least one collimated light source, to a cornea surface; detecting at least a part of the light pattern reflected from the cornea surface, the at least the part of the light pattern being guided by a sensor waveguide; obtaining a mapping image corresponding to the at least the part of the light pattern; and determining a direction of a gaze based on the obtained mapping image. The sensor waveguide used to determine the direction of the gaze is different from a waveguide for displaying output information.