Sub-500 μm Eye Tracking Illuminator with Beam Diversion
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Solution Overview
Problem
Existing eye-tracking systems in artificial reality systems face inaccuracies due to the size of light sources used, which can result in errors in determining the gaze direction, as the glints from non-point source LEDs appear larger than intended, affecting the precision of eye-tracking results.
Innovation Solution
The use of a light source with a maximum dimension of less than 500 μm and an emission cone angle of less than 30°, positioned within the user's field of view, along with a beam diverting component such as micro-prisms or gratings to direct light towards the eye at an angle, enhancing accuracy and minimizing visibility to the user.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a light source with larger emission area (e.g., 200 μm or more diameter LED) is used, then the illumination intensity is sufficient, but the glint size in the captured image increases, reducing measurement precision
Solution Approach 1:
The patent changes the physical parameters of the light source by reducing its emission area to less than 500 μm in maximum dimension and limiting the emission cone angle to less than 30°. This parameter change allows the light source to function effectively while producing a smaller glint image that can be precisely localized, thereby resolving the contradiction between illumination intensity and measurement precision
Solution Approach 2:
The patent introduces beam diverting components (micro-prisms, gratings, or inclined planes) that redirect light at specific angles (e.g., 45 degrees) toward the eye. This dimensional redirection of light paths enables precise control over where the light intersects the eye surface, creating well-defined glint positions that can be accurately measured despite the light source's physical constraints
2Area of stationary object
If light sources are positioned at the periphery of the user's field of view, then the field of view is not blocked, but the large angles of illuminating light result in reduced eye tracking accuracy
Solution Approach 1:
The patent introduces beam diverting components as intermediary elements between the light source and the eye. These components (micro-prisms, gratings, or inclined planes) act as mediators that redirect the light paths at controlled angles, enabling the light to reach the eye at optimal angles even when the light source is positioned in the periphery of the field of view, thus maintaining both field of view and eye tracking accuracy
3Area of stationary object
If a light source with emission cone angle greater than 30° is used, then the light coverage area is larger, but the glint position accuracy decreases due to increased angular spread
Solution Approach 1:
The patent strictly limits the emission cone angle parameter to less than 30° for the light source. This parameter constraint ensures that the light rays intersect the eye surface at well-defined angles, creating sharp, localized glint positions that can be precisely measured, while still providing sufficient coverage through strategic positioning and beam diversion
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 configuration improves the precision of eye-tracking by reducing errors in determining the gaze direction and provides a more immersive experience by minimizing the impact on the user's field of view, allowing for more accurate and invisible light sources within the eye-tracking system.
Implementation Method 1
a light source positioned on a surface of the substrate. The light source is configured to be positioned within a field of view of the eye of the user
Implementation Method 2
the light illuminating the eye may be reflected specularly by the cornea of the user's eye, resulting in 'glints' in a captured image of the eye
Implementation Method 3
The beam diverting component may be a micro-prism, an inverse micro-prism, an off-axis micro-lens, a grating, or an inclined plane
Implementation Method 4
The beam diverting component may be a micro-prism, an inverse micro-prism, an off-axis micro-lens, a grating, or an inclined plane
Implementation Method 5
An encapsulation layer that surrounds the light source. A refractive index of the encapsulation layer matches a refractive index of the substrate
Data Source
AI summary
Disclosed herein are techniques for eye illumination for eye position tracking. An illuminator for eye tracking includes a substrate configured to be placed in front of an eye of a user and a light source positioned on a surface of the substrate. The light source is configured to be positioned within a field of view of the eye of the user. A maximum dimension of the light source in a plane parallel to an emission surface of the light source is less than 500 μm.