Time-Multiplexed Eye Tracking Glint Detection
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Solution Overview
Problem
Eye tracking in head-mounted display (HMD) systems, particularly in VR and AR environments, faces challenges due to obscured glints by the pupil or eyelids, and limitations in the number and intensity of light beams that can be projected safely, which affect the accuracy of eye orientation determination.
Innovation Solution
The HMD system employs a time-multiplexed illumination source that projects different light patterns over distinct time periods, allowing the controller to identify sufficient unobscured glints and determine the eye's shape and orientation by capturing images with a camera assembly, ensuring accurate eye tracking even when some glints are obscured.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multiple light beams are projected simultaneously towards the user's eye to increase the number of reflected glints, then the number of detectable glints improves, but the light intensity and safety limits are exceeded
Solution Approach 1:
The patent applies periodic action by projecting light beams in sequential time-multiplexed patterns rather than simultaneously. Multiple light patterns are projected at different time periods, allowing the system to accumulate sufficient glint data over time while keeping the intensity of individual beams within safe limits. This temporal separation resolves the contradiction between needing multiple beams and maintaining safety limits.
2Object-affected harmful factors
If the number of light beams is limited due to safety reasons, then light intensity safety is maintained, but the number and intensity of reflected glints are reduced
Solution Approach 1:
By using periodic action with time-multiplexed light patterns, the system projects multiple patterns sequentially rather than simultaneously. This allows accumulation of sufficient glint reflections over multiple time periods while maintaining safe intensity levels for each individual pattern, thereby preserving measurement precision without exceeding safety limits.
Solution Approach 2:
The system performs preliminary actions by projecting multiple light patterns in advance over different time periods. The controller captures images and identifies glints from each pattern sequentially, building up sufficient data before determining eye orientation. This preliminary accumulation of data ensures accurate eye tracking even with limited simultaneous beams.
3Device complexity
If a single light pattern is projected, then the system complexity is reduced, but some glints may be obscured by the pupil or eyelids reducing tracking accuracy
Solution Approach 1:
The patent applies segmentation by dividing the illumination into multiple distinct light patterns projected at different time periods. Each pattern is designed to illuminate different regions or angles, ensuring that if some glints are obscured by the pupil or eyelids, other glints from different patterns remain visible. This segmentation maintains measurement precision without significantly increasing system complexity.
Solution Approach 2:
By implementing periodic action with multiple time-multiplexed light patterns, the system cycles through different illumination configurations. This ensures comprehensive coverage of the eye surface over time, capturing glints from various angles and positions, thereby improving glint detection accuracy while keeping the illumination system relatively simple.
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 approach enhances the accuracy of eye tracking by ensuring sufficient glints are identified for determining the eye's orientation, improving signal-to-noise ratio and reducing interference, while adhering to safety limits on light intensity and number.
Implementation Method 1
Each light pattern comprises a plurality of light beams projected towards different locations on the user's eye, each of the light beams able to be reflected by the cornea of the eye to produce a corresponding glint
Data Source
AI summary
A head mounted display (HMD) comprises an eye tracking system configured to enable eye-tracking using light. The eye tracking system implements time-multiplexing by configuring a source assembly comprising a plurality of light sources to project at least a first light pattern towards the user's eye over a first time period, and a second light pattern towards the user's eye over a second time period in accordance with a set of emission instructions. A camera assembly is configured to capture images of the user's eye during the first and second time periods in accordance with a set of imaging instructions, the captured images containing one or more glints corresponding to reflections of the first or second light patterns on the cornea of the user's eye. The location of the glints may be used to determine a shape or orientation of the eye.