High Refractive Index Optical Element for Eye-Tracking Illumination
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Solution Overview
Problem
Current optical devices face challenges in achieving uniform illumination, particularly for eye-tracking applications, where light beams need to be directed towards the center of the eyebox from large lateral displacements, and existing solutions often suffer from total internal reflection issues leading to stray glare and non-uniform illumination patterns.
Innovation Solution
The use of high refractive index optical elements, such as gallium phosphide, embedded in an encapsulant layer with a lower refractive index, and combined with metamaterial layers, to shape and steer light beams, preventing total internal reflection and ensuring uniform illumination across the eyebox.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional optical elements are used to direct light beams from large lateral displacements, then beam steering capability is achieved, but total internal reflection occurs causing stray glare and non-uniform illumination
Solution Approach 1:
The patent changes the refractive index parameter by using high refractive index materials (n>2.0, preferably n>2.5, more preferably n>3.0) for the optical element. This parameter change allows the optical element to maintain precise beam steering capability from large lateral displacements while eliminating total internal reflection issues that cause stray glare and non-uniform illumination patterns.
Solution Approach 2:
The patent employs composite material structures where a high refractive index optical element (such as gallium phosphide or other semiconductor materials) is integrated with an encapsulant layer having a lower refractive index. This composite structure enables the optical element to achieve both effective beam steering and uniform illumination by controlling the refractive index relationship between the two materials, preventing harmful total internal reflection at their interface.
2Illumination intensity
If high refractive index optical elements are used to prevent total internal reflection, then illumination uniformity is improved, but device complexity increases due to material integration requirements
Solution Approach 1:
The patent merges the optical element with the light source by integrating the high refractive index optical element directly onto the light source substrate or housing. This merging approach simplifies the overall device structure by combining multiple components into a single integrated unit, thereby achieving uniform illumination without proportionally increasing device complexity.
Solution Approach 2:
The patent utilizes parameter changes in the encapsulant layer by selecting materials with specific refractive index ranges (lower than the optical element but optimized for light transmission). This parameter optimization ensures that the interface between the optical element and encapsulant layer minimizes total internal reflection, achieving uniform illumination while maintaining manageable device complexity through careful material selection.
3Ease of manufacture
If conventional materials are used for optical elements, then ease of manufacture is maintained, but beam shaping capability at high projection angles is insufficient
Solution Approach 1:
The patent changes the material parameter by adopting high refractive index materials (n>2.0, preferably n>2.5, more preferably n>3.0) such as gallium phosphide or other semiconductor materials. These materials inherently provide superior beam shaping capability at high projection angles due to their optical properties, while their compatibility with existing semiconductor fabrication processes maintains ease of manufacture.
Solution Approach 2:
The patent replaces conventional optical materials with advanced semiconductor materials that can be manufactured using standard semiconductor fabrication techniques. This substitution enables precise beam shaping at high projection angles through material property optimization rather than complex mechanical or geometric designs, thereby maintaining manufacturing simplicity while achieving superior beam shaping precision.
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 enhances illumination uniformity and prevents stray glare, providing improved beam shaping and steering capabilities, especially at high projection angles, ensuring efficient light distribution for eye-tracking systems.
Implementation Method 1
The optical element may include a material (e.g., a high-index material), such as at least one of a semiconductor or a dielectric material
Implementation Method 2
existing solutions often suffer from total internal reflection issues leading to stray glare and non-uniform illumination patterns
Implementation Method 3
The exit surface of the optical element may have a shaped surface, such as a freeform curved surface, configured to redirect the light beam
Implementation Method 4
embedded in an encapsulant layer with a lower refractive index, and combined with metamaterial layers, to shape and steer light beams, preventing total internal reflection
Data Source
AI summary
An example device may include a light source, an optical element, and, optionally, an encapsulant layer. A light beam generated by the light source may be received by the optical element and redirected towards an illumination target, such as an eye of a user. The optical element may include a material, for example, with a refractive index of at least approximately 2 at a wavelength of the light beam. The light source may be a semiconductor light source, such as a light-emitting diode or a laser. The optical element may be supported by an emissive surface of the light source. Refraction at an exit surface of the optical element, and/or within a metamaterial layer, may advantageously modify the beam properties, for example, in relation to illuminating a target. In some examples, the light source and optical element may be integrated into a monolithic light source module.