Annular Diffusor Lens With GRIN Profile for Homogeneous VCSEL Beams
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Solution Overview
Problem
Existing diffusor lenses for VCSELs suffer from diffraction losses and inhomogeneous beam profiles due to small size and discontinuities in Fresnel lenses, which are difficult to integrate into semiconductor chips and cause optical losses and inhomogeneities in beam profiles.
Innovation Solution
A flat diffusor lens with concentric annular segments having varying refractive indices, transitioning smoothly between segments to avoid height steps and ensure homogeneous beam profiles, which can be integrated into VCSEL arrays as a GRIN or meta-lens.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If small diffusor lenses are used to achieve good homogeneity of rectangular beam profile, then beam profile homogeneity is improved, but diffraction losses increase due to lenses not being ideally illuminated
Solution Approach 1:
The diffusor lens is divided into multiple concentric annular segments with different refractive indices. This segmentation allows each segment to be optimized for its specific function: inner segments focus light to create the rectangular profile, while outer segments diffuse light to maintain homogeneity and reduce diffraction losses at the edges.
Solution Approach 2:
Different regions of the diffusor lens are assigned different refractive indices tailored to their specific optical functions. The inner segments have refractive indices optimized for focusing and profile creation, while outer segments have refractive indices optimized for diffusion and loss reduction, allowing each local region to perform its function optimally.
2Loss of energy
If larger lenses are used to avoid diffraction losses, then diffraction losses are reduced, but lens sag increases making integration into semiconductor chips difficult
Solution Approach 1:
Instead of increasing lens aperture size in the lateral dimensions, the invention uses the refractive index dimension to achieve the desired optical effects. By varying the refractive index across different annular segments, the patent accomplishes light control functions that would otherwise require larger physical dimensions, thereby maintaining compatibility with semiconductor chip integration constraints.
3Length of moving object
If Fresnel lenses are used to reduce lens sag, then lens sag is reduced, but discontinuities between annular sections cause losses and inhomogeneities in beam profile
Solution Approach 1:
The invention changes the refractive index parameter across different annular segments to achieve the desired light control. By continuously varying the refractive index from the center to the periphery, the patent eliminates the abrupt discontinuities found in traditional Fresnel lenses, thereby maintaining beam profile homogeneity while keeping the lens thin for easy integration.
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
The solution provides a homogeneous beam profile for reliable sensing applications, reducing optical losses and simplifying integration into semiconductor chips while maintaining cost-effectiveness and flexibility.
Implementation Method 1
The refractive index of the diffusor lens varies in a direction perpendicular to the optical axis. The refractive index profile in a cross-section along a plane including the optical axis of the diffusor lens comprises a first sub-profile and a second sub-profile, each having a curvature, wherein the curvatures of the first and second sub-profiles are described by the same curvature function but have different signs with respect to each other.
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
The present invention describes a diffusor lens (1), comprising a first annular lens segment (2) and a second annular lens segment (4). The first and the second lens segment (2, 4) being concentric, wherein a refractive index of the first and second lens segment (2, 4) in a cross-section along a plane including an optical axis of the diffusor lens is described by a refractive index profile (5) which varies in a direction perpendicular to the optical axis and which comprises a first sub-profile (12) which describes the refractive index profile of the first lens segment (2) and a second sub-profile (14) which describes the refractive index profile of the second lens segment (4). The first sub-profile (12) transitions to the second sub-profile (14) at an interface (10) and the first and second sub-profile (12, 14) have a slope with opposite sign. The present invention further describes a light source (50) comprising a VCSEL (70) and such a diffusor lens (1), a method of fabricating such a light source (50) and a method of illuminating a scene.