Multi-directional waveguide gratings for HMD eye tracking
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Solution Overview
Problem
Existing eye tracking systems for head-mounted displays (HMDs) are limited by natural obstructions such as eyelashes and eyelids, which reduce the quality of eye tracking operations by obstructing image capture from the periphery of the eye.
Innovation Solution
A waveguide system with multi-directional gratings is integrated into the HMD, allowing for in-field eye tracking by capturing light reflections from directly in front of the eye and redirecting them to an image sensor, thereby expanding the eyebox region and minimizing obstructions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If eye tracking is performed from the periphery of the eye, then eye tracking functionality is enabled, but image quality is degraded due to obstructions from eyelashes and eyelids
Solution Approach 1:
The patent transitions from peripheral eye tracking to in-field eye tracking by redirecting light from the optical path into the waveguide. This dimensional change in light routing allows the imaging sensor to be positioned within the optical path without obstructing the user's view, thereby capturing higher quality images of the eye without peripheral obstructions.
Solution Approach 2:
The waveguide acts as an intermediary element that captures light reflections from the eye through diffraction gratings and redirects them to the imaging sensor. This intermediary mechanism enables the sensor to receive clear eye images without being positioned in the direct optical path where it would obstruct the user's view or be subject to peripheral obstructions.
2Measurement precision
If the imaging sensor is positioned in the optical path for in-field eye tracking, then image quality is improved, but the device complexity increases due to additional optical components
Solution Approach 1:
The waveguide performs multiple functions: it guides display light to the user's eye, captures eye tracking light reflections through diffraction gratings, and redirects this light to the imaging sensor. By integrating these functions into a single component, the system achieves in-field eye tracking with high image quality without adding separate complex optical subsystems.
Solution Approach 2:
The patent merges the display optical path and eye tracking imaging path within the same waveguide structure. The diffraction gratings serve dual purposes by both guiding display light and capturing eye reflections, while the imaging sensor is integrated into the waveguide system rather than being a separate peripheral component.
3Area of stationary object
If multiple diffraction gratings are used to redirect light from different directions, then the eyebox region is expanded, but manufacturing complexity increases
Solution Approach 1:
The waveguide incorporates multiple diffraction gratings positioned at different locations and orientations to capture light from different directions within the eyebox region. Each grating segment handles a specific angular range of incoming light, and together they provide comprehensive coverage of the expanded eyebox area through modular functional segmentation.
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 enables distraction-free and high-quality eye tracking by reducing the impact of eyelashes and eyelids, improving user experience and the accuracy of eye orientation detection for HMDs.
Implementation Method 1
A first diffraction grating of the diffraction gratings may be configured to redirect a first portion of the light in a first direction into the waveguide. A second diffraction grating of the diffraction gratings may be configured to redirect a second portion of the light in a second direction into the waveguide.
Implementation Method 2
A waveguide system with multi-directional gratings is integrated into the HMD, allowing for in-field eye tracking by capturing light reflections from directly in front of the eye and redirecting them to an image sensor
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 have a number of multi-directional gratings configured to direct light to an out-coupling grating. The multi-directional gratings include first and second in-coupling diffraction gratings disposed in a waveguide. The first and second in-coupling diffraction gratings are oriented to direct incident light in multiple directions within the waveguide towards the out-coupling diffraction grating.