Wafer-Level Optics for VCSEL Eye Tracking Uniformity
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Solution Overview
Problem
In head-mounted displays (HMDs) using VCSELs for eye tracking, there is a challenge in efficiently directing infrared light from VCSELs to the eyebox area, particularly at the edges where the narrow emission cone angle results in wasted light, due to the difficulty in bonding VCSELs on curved surfaces and the need for uniform illumination to enhance eye-tracking accuracy.
Innovation Solution
The use of beam diverting components such as micro-prisms, off-axis micro-lenses, inverse micro-prisms, gratings, and inclined planes to adjust the tilt angle and divergence of light emitted by VCSELs, ensuring that light is directed towards the eye even at the edges, and the implementation of wafer-level optics with different tilt and divergence angles to optimize light distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If VCSELs are used with narrow emission cone angles, then device complexity is reduced, but light distribution uniformity deteriorates causing wasted light at edges
Solution Approach 1:
A curved diffuser is introduced as an intermediary component between the VCSEL array and the eyebox area. The diffuser has a specific curvature radius that matches the VCSEL emission characteristics, transforming the narrow emission cones into uniformly distributed light across the eyebox region without requiring complex VCSEL structures or arrangements
Solution Approach 2:
The emission parameters of the VCSELs are effectively changed by using a diffuser with a specific curvature radius. The curvature radius is selected to match the emission cone angle characteristics, transforming the directional emission into omnidirectional uniform illumination while keeping the VCSELs themselves simple and unchanged
2Ease of operation
If VCSELs are bonded on curved surfaces to direct light to eyebox, then light direction control is improved, but manufacturing difficulty increases
Solution Approach 1:
Instead of bonding VCSELs on a curved surface to achieve light direction control, the invention inverts the approach: VCSELs are mounted on a flat substrate, and a curved diffuser is placed over them. The curvature of the diffuser, not the VCSEL mounting surface, provides the light direction control, making manufacturing much easier while achieving the same optical effect
3Illumination intensity
If beam diverting components are added to direct light at edges, then light distribution uniformity is improved, but device complexity increases
Solution Approach 1:
Multiple functions are merged into a single curved diffuser component. The diffuser simultaneously performs light scattering, directional control, and uniformity enhancement that would otherwise require separate beam diverting components for each VCSEL or zone. This single integrated component achieves uniform light distribution without increasing device complexity
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 ensures that light is uniformly distributed across the eyebox area, improving eye-tracking accuracy and reducing light wastage by effectively directing infrared light from VCSELs towards the eye, even at the edges, thereby enhancing the overall performance of HMDs in augmented and virtual reality applications.
Implementation Method 1
beam diverting components such as micro-prisms, off-axis micro-lenses, inverse micro-prisms
Implementation Method 2
gratings
Implementation Method 3
wafer-level optics with different tilt and divergence angles
Data Source
AI summary
A plurality of light sources such as vertical-cavity surface-emitting lasers (VCSELs) are configured to emit non-visible light through emission apertures. Optics are formed over the emission apertures of the plurality of light sources. The optics may provide different tilt angles or divergence angles to the non-visible light emitted by the light sources in the plurality of light sources.