Wavelength-Multiplexed Waveguide Eye Tracking for Obstruction-Free Imaging
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Solution Overview
Problem
Existing eye tracking systems in head-mounted displays (HMDs) are limited by natural obstructions such as eyelashes and eyelids, which degrade the quality of eye tracking operations.
Innovation Solution
A wavelength multiplexed waveguide system is integrated into the HMD, utilizing in-coupling and out-coupling diffraction gratings to capture light reflections from directly in front of the eye, encoding spatial positions of reflections into angles, and expanding the eyebox region for improved eye tracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing eye tracking systems are used, then eye tracking functionality is provided, but image quality is degraded due to obstructions from eyelashes and eyelids
Solution Approach 1:
The patent introduces a waveguide system as an intermediary optical component that captures light reflections from the eye through diffraction gratings. This intermediary structure enables the imaging path to bypass the obstructive eyelashes and eyelids, allowing clear eye tracking imaging without direct line-of-sight obstruction.
Solution Approach 2:
The patent transitions from traditional 2D image sensor imaging to 3D volumetric light field capture using a waveguide with diffraction gratings. By encoding spatial positions into angles and utilizing the waveguide's optical path, the system captures eye reflections from multiple dimensions, enabling obstruction-free imaging from directly in front of the eye.
2Object-affected harmful factors
If in-field imaging is implemented, then obstructions from eyelashes and eyelids are reduced, but system complexity increases due to waveguide integration
Solution Approach 1:
The waveguide system serves multiple functions simultaneously: it acts as both the display waveguide for presenting visual content to the user and the imaging waveguide for capturing eye reflections. By integrating these two functions into a single optical path, the patent reduces overall system complexity despite the advanced optics required.
Solution Approach 2:
The patent merges the display optical path and the eye tracking imaging optical path into a single waveguide structure. The same waveguide that delivers visual information to the user's eye also captures reflected light for eye tracking, combining previously separate subsystems into one integrated unit.
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 enables distraction-free, in-field imaging of the eye, reducing obstructions and enhancing the quality and effectiveness of eye tracking operations in HMDs.
Implementation Method 1
A first in-coupling diffraction grating of a set of in-coupling diffraction gratings is positioned within the waveguide and configured to diffract first-wavelength light into the waveguide
Implementation Method 2
The waveguide may direct (e.g., through total internal reflection (TIR)) the light from the in-coupling diffraction gratings to the out-coupling diffraction grating
Implementation Method 3
An out-coupling diffraction grating is positioned in the waveguide and configured to diffract the light from the in-coupling diffraction gratings
Data Source
AI summary
An apparatus, system, and method for a waveguide system may be used to support eye tracking in a head mounted display (HMD). The waveguide system may be positioned in a user's field of view and within a lens assembly of the HMD to capture light that is reflected from an eye. The waveguide system may include a waveguide, a first diffraction grating, and a second diffraction grating. The first diffraction grating may be configured to in-couple light of a first wavelength into the waveguide, and the second diffraction grating may be configured to in-couple light of a second wavelength. The first and second diffraction gratings operate together to detect light reflections from an eyebox region.