Low-Density MicroLED Light Source With Backside Attenuation
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Solution Overview
Problem
Existing eye-tracking systems using oblique illumination sources are inefficient and require higher optical power or more sensitive detectors due to the distance from the eye, leading to reduced accuracy and interference with the user's line of sight.
Innovation Solution
A low-density set of light-emitting elements positioned on or within a transparent or reflective substrate, emitting light out-of-plane to directly illuminate the observer's eyes without obstructing the line of sight, combined with an optical attenuator to manage unwanted light propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If oblique illumination sources are used for eye-tracking, then the line of sight is not obstructed, but the illumination efficiency is reduced and higher optical power is required
Solution Approach 1:
The patent transitions from oblique illumination (side lighting) to normal illumination by positioning light-emitting elements on the rear surface of the substrate, causing light to propagate perpendicular to the substrate surface. This dimensional change in light propagation direction enables direct illumination of the observer's eyes while maintaining line-of-sight clarity, thereby improving illumination efficiency without obstructing the view.
2Illumination intensity
If light-emitting elements are positioned densely to ensure adequate illumination, then illumination coverage is improved, but visibility of the light source increases and line of sight is obstructed
Solution Approach 1:
By positioning light-emitting elements on the rear surface and directing light propagation perpendicular to the substrate, the patent achieves adequate illumination coverage even with sparse element distribution. The light path is directed away from the observer's line of sight, reducing visibility of the light source while maintaining illumination effectiveness.
Solution Approach 2:
The patent employs a low-density arrangement of light-emitting elements where each element is sufficiently small and sparsely spaced to be negligibly visible, yet collectively provides adequate illumination coverage. This local quality approach balances illumination requirements with aesthetic considerations.
3Measurement precision
If conventional light sources are used with high optical power to compensate for distance, then illumination accuracy is improved, but interference with user's line of sight increases
Solution Approach 1:
The patent positions light-emitting elements on the rear surface of the substrate, directing light propagation perpendicular to the substrate surface and away from the observer's line of sight. This dimensional change in light emission direction enables high optical power illumination without interfering with the user's view, as the light travels through the substrate rather than blocking it.
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 accurate eye-tracking with minimal interference by allowing direct illumination and clear observation through the light source, using microLEDs with small dimensions and sparse spacing to resemble dust or hair, thus being negligibly visible.
Implementation Method 1
Each light-emitting element comprises one or more inorganic microLEDs that are arranged to generate and emit visible output light
Implementation Method 2
The optical attenuator structure attenuates or blocks transmission of any of the visible output light that propagates in a second direction opposite the first direction
Data Source
AI summary
An inventive light source includes a transparent substrate, light-emitting elements on or within the substrate, and an optical attenuator structure. The light-emitting elements include inorganic microLEDs that generate and emit visible output light to propagate out-of-plane in a first direction away from a first surface of the substrate. The light-emitting elements are sufficiently small, and occupy a sufficiently small fraction of area, to enable visual observation of a scene through the substrate along a sight line that passes through the set of light-emitting elements. The optical attenuator structure attenuates or blocks transmission of the visible output light that propagates in a second direction opposite the first direction, and transmits enough visible light to enable visual observation of the scene along the sight line through the optical attenuator structure and through the set of light-emitting elements.