Waveguide Eye Tracking Layout for Eyelash-Obstructed HMD Imaging
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Solution Overview
Problem
Existing eye tracking systems in head-mounted displays are limited by natural obstructions such as eyelashes and eyelids, which obstruct images and decrease tracking quality.
Innovation Solution
A multi-directional waveguide eye tracking system that uses two waveguide systems with input and output diffractive optical elements to capture light from different portions of the eyebox region, directing it to multiple image sensors for improved eye orientation determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a camera is positioned at the periphery of the eye to avoid obstructing user vision, then user comfort is improved, but image quality decreases due to obstruction by eyelashes and eyelids
Solution Approach 1:
The patent transitions from peripheral imaging to in-field imaging by redirecting light through waveguide optics. This dimensional change in light path allows the camera to capture high-quality eye images from the front center position without being obstructed by eyelashes and eyelids, while maintaining unobstructed user vision through the display optics.
Solution Approach 2:
The waveguide optical system acts as an intermediary that redirects light from the eye to the image sensor. The diffractive optical elements and waveguide structure serve as mediators to transport optical information from the in-field region to the camera positioned in the display optical path, enabling both high image quality and unobstructed user vision.
2Measurement precision
If the eye tracking system uses in-field imaging to improve image quality, then measurement precision is improved, but the system complexity increases due to additional optical components
Solution Approach 1:
The waveguide optical system performs multiple functions: it guides display light to the user's eye, redirects eye reflection light to the image sensor, and maintains unobstructed vision. By integrating eye tracking functionality into the existing display waveguide structure, the patent avoids adding separate complex optical systems while achieving in-field imaging.
Solution Approach 2:
The patent merges the eye tracking optical path with the display optical path by positioning the image sensor within the display waveguide structure. This consolidation allows the same waveguide components to serve both display and eye tracking functions, reducing overall system complexity compared to having separate independent systems.
3Adaptability or versatility
If the waveguide system captures light from a larger eyebox region, then adaptability is improved, but light intensity decreases due to light distribution over larger area
Solution Approach 1:
The diffractive optical elements are designed with spatially varying properties to redirect light from different regions of the eyebox to appropriate areas of the image sensor. This local optimization ensures that each region of the expanded eyebox maintains sufficient light intensity for high-quality imaging while covering a larger overall area.
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
Enables distraction-free and in-field imaging of the eye, expanding the eyebox region for enhanced eye tracking capabilities and improving the accuracy of eye orientation determination.
Implementation Method 1
The first input diffractive optical element is configured to in-couple light from a first portion of an eyebox region and direct the light in a first direction within the first waveguide. The second input diffractive optical element is configured to in-couple light from a second portion of the eyebox region and direct the light in a second direction within the second waveguide.
Implementation Method 2
a first waveguide, a first input diffractive optical element, and a first output diffractive optical element. The first input diffractive optical element is configured to in-couple light from a first portion of an eyebox region and direct the light in a first direction within the first waveguide.
Data Source
AI summary
A lens assembly for a head mounted device may be configured to in-couple light from an eyebox region using a number of waveguide systems coupled to a number of image sensors, for example, for one or both lens assemblies in the head mounted device. The waveguide systems may be positioned in the lens assembly. The waveguide systems may be configured to in-couple light from various portions of the eyebox region. The waveguide systems may be configured to couple the light from a center region of the lens assembly to a number of peripheral regions of the lens assembly. The image sensors may be optically coupled to the waveguide systems and may be configured to receive portions of the light from the waveguide systems.