Immersed Hot Mirrors for Eye Tracking Illumination
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Solution Overview
Problem
Existing eye-tracking systems in near-eye display devices face inaccuracies due to the size of light sources used for illumination, which appear as extended sources rather than point sources, leading to errors in determining the gaze direction and increased power consumption with multiple light sources.
Innovation Solution
Incorporating a plurality of dichroic mirrors, such as hot mirrors, immersed in a transparent substrate within the user's field of view to reflect infrared light for illumination while allowing visible light to pass through, creating a more precise glint location detection and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a light source with a larger emission area is used to illuminate the eye, then the illumination intensity is improved, but the glint location precision deteriorates because the light source cannot be approximated as a point source
Solution Approach 1:
A transparent substrate with optical properties matching the surrounding medium is introduced as an intermediary. The substrate contains an extended light source that appears as a point source when viewed from the eye's perspective, thereby maintaining illumination intensity while achieving precise glint location measurement.
Solution Approach 2:
The invention creates an optical copy or virtual image of the extended light source that appears as a point source. The transparent substrate reproduces the appearance of a point source while the actual physical light source remains extended, allowing both high illumination and precise localization.
2Measurement precision
If multiple light sources are positioned in the periphery of the user's field of view, then the eye tracking accuracy is improved through multiple glint measurements, but the power consumption increases
Solution Approach 1:
Multiple light sources are merged into a single transparent substrate that can be positioned centrally in the field of view. The substrate integrates the illumination function of multiple sources while appearing as a single point source, reducing power consumption while maintaining tracking accuracy through the point source approximation.
Solution Approach 2:
The transparent substrate serves multiple functions simultaneously: it houses the light source, provides optical matching to eliminate reflections, and creates a virtual point source image. This multi-functionality allows a single component to replace multiple peripheral light sources.
3Illumination intensity
If a light source is positioned at the periphery of the user's field of view, then the eye can be illuminated for tracking, but the visible display content is obstructed
Solution Approach 1:
A transparent substrate acts as an intermediary that allows the light source to be positioned in the central field of view without obstructing visible content. The substrate's optical matching with the surrounding medium makes it invisible, enabling simultaneous eye illumination and unobstructed display viewing.
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 enhances the accuracy of eye tracking by making the light source appear as a point source, improving gaze direction determination and reducing power consumption by eliminating the need for multiple light sources.
Implementation Method 1
The at least one reflector may be configured to reflect the light in the first wavelength range to the eye of the user
Implementation Method 2
reflectors or mirrors (e.g., dichroic mirrors such as hot mirrors) immersed in a transparent substrate
Implementation Method 3
The substrate may be transparent to both the light in the first wavelength range and the light in the second wavelength range
Implementation Method 4
The camera may be configured to receive light in the first wavelength range and reflected by the eye of the user
Data Source
AI summary
Disclosed herein are techniques for eye illumination for eye position tracking. An illuminator for eye illumination includes a light source, a substrate configured to be placed in front of an eye of a user, and at least one reflector located within the substrate. The light source is configured to emit light in a first wavelength range to illuminate the at least one reflector. The at least one reflector is configured to reflect the light in the first wavelength range to the eye of the user, and transmit light in a second wavelength range different from the first wavelength range. The substrate is transparent to both the light in the first wavelength range and the light in the second wavelength range.