Concave Light Input Surface for LED Coupling
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Solution Overview
Problem
Existing light sources struggle to efficiently couple and collimate light emitted by light-emitting devices with angular distributions, often resulting in non-uniform brightness and color distribution at the output, especially when using LEDs with Lambertian emission characteristics.
Innovation Solution
A light source comprising a light-emitting device and an optical element with a concave curved input surface that covers a larger solid angle than a flat input surface, allowing efficient coupling of light and subsequent collimation through a larger output surface, achieved via a non-imaging optical design with total internal reflection and materials like polycarbonate, which provides refractive indices greater than air, ensuring homogeneous brightness and color distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a flat input surface is used, then the device complexity is reduced, but the light coupling efficiency deteriorates
Solution Approach 1:
The input surface of the optical element is designed with a concave curvature that matches the emitting surface geometry, enabling the surface to cover a larger solid angle and capture light emitted at various angles. This curved geometry increases the coupling efficiency from less than 50% with flat surfaces to over 90% without adding complex multi-element optical systems.
2Illumination intensity
If the light output surface area is enlarged for better light distribution, then the brightness uniformity is improved, but the device size increases
Solution Approach 1:
The optical element utilizes the third dimension (depth/thickness) to achieve light redistribution. By designing the internal geometry and output surface area to be larger than the input surface, the element spreads light across a broader area while maintaining a compact overall form factor, improving brightness uniformity without proportionally increasing the device footprint.
3Loss of energy
If the concave curvature of the input surface is increased to capture more light, then the light coupling efficiency is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent optimizes the concave curvature parameters to achieve a balance between light coupling efficiency and manufacturability. By selecting specific curvature radii and surface profiles that match common LED emitting geometries, the design achieves high coupling efficiency while remaining compatible with standard manufacturing processes such as injection molding, avoiding the need for ultra-precise custom fabrication.
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 achieves efficient light coupling and collimation, resulting in a homogeneous brightness and color distribution at the output surface, with up to 90% of light being coupled and a beam opening angle of 20° to 60°, enhancing the light source's efficiency and longevity by minimizing scattering and refraction.
Implementation Method 1
the light input surface has a concave curvature and an area being smaller than the area of the light output surface
Implementation Method 2
the electromagnetic radiation entering the optical element through the light input surface
Data Source
AI summary
A light source comprises a light-emitting device (1) emitting electromagnetic radiation from an emitting surface (18) and an optical element (2) having a light input surface (21), a light output surface (22) and side surfaces (23) connecting the light input surface (21) to the light output surface (22). The light input surface (21) is located in the optical path of the light-emitting device (1), the electromagnetic radiation entering the optical element (2) through the light input surface (21), and the light input surface (21) has a concave curvature and an area being smaller than the area of the light output surface (22).