Compound Converging Optical Element for LED Light Extraction
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Solution Overview
Problem
LEDs face challenges in efficiently extracting light due to the high refractive index mismatch between semiconductor materials and air, leading to significant total internal reflection and reduced brightness, despite the use of encapsulants which also have a higher refractive index than air.
Innovation Solution
The development of optical elements with converging shapes, optically coupled to the LED emitting surface, which redirect light to the sides without the need for mirrors or reflective layers, using materials with high refractive indices and thermal conductivity to enhance light extraction and modify the emission pattern.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If light is emitted from LED in semiconductor materials, then brightness and output are achieved, but light extraction efficiency is reduced due to high refractive index mismatch with air
Solution Approach 1:
The patent introduces an optical element with refractive index n2 that serves as an intermediary between the semiconductor material (n1) and air (n3). This intermediate medium reduces the refractive index mismatch, allowing light to escape the semiconductor more efficiently while maintaining brightness. The optical element acts as a mediator that facilitates light extraction without requiring the semiconductor to directly interface with air.
Solution Approach 2:
The patent changes the refractive index parameter by introducing materials with specific refractive indices between the semiconductor and air. By selecting optical materials with refractive indices that form a gradient (n1 > n2 > n3), the system modifies the optical parameters to reduce total internal reflection and improve light extraction efficiency while preserving brightness.
2Loss of energy
If encapsulants with higher refractive index than air are used, then light extraction is enhanced, but significant refractive index mismatch remains between semiconductor and encapsulant
Solution Approach 1:
The optical element is divided into multiple sections with different refractive indices. The first section has refractive index n2 and the second section has refractive index n4, creating a segmented structure that progressively manages the refractive index transition. This segmentation allows each section to handle a portion of the refractive index mismatch, reducing the overall optical complexity.
Solution Approach 2:
Different sections of the optical element have different local optical properties (refractive indices). The first section closer to the semiconductor has one refractive index while the second section farther away has another, optimizing light extraction at each interface. This local differentiation of optical properties addresses the refractive index mismatch problem zone by zone.
3Loss of energy
If optical elements with high refractive index materials are used, then light extraction efficiency is improved, but thermal management requirements increase
Solution Approach 1:
The optical element is designed to perform multiple functions simultaneously: it extracts light efficiently through its refractive index properties while also serving as a thermal management component. By integrating both optical and thermal functions into a single element, the patent avoids adding separate components, thereby managing temperature without compromising light extraction efficiency.
Solution Approach 2:
The patent employs composite material structures in the optical element that combine materials with appropriate refractive indices for light extraction and materials with good thermal conductivity for heat dissipation. This composite approach allows simultaneous optimization of optical performance and thermal management properties within the same component.
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 approach improves light extraction efficiency, reduces manufacturing costs by eliminating reflective layers, and provides thermal management capabilities, suitable for various applications including backlights in liquid crystal displays and backlit signs.
Implementation Method 1
an optical element including a base, an apex, the base, and a converging side joining the base and the apex... which redirect light to the sides
Implementation Method 2
Because of a large refractive index mismatch between the semiconductor and air, an angle of an escape cone for the semiconductor-air interface is relatively small. Much of the light generated in the semiconductor is totally internally reflected
Implementation Method 3
Encapsulants have a higher index of refraction than air, which reduces the total internal reflection at the semiconductor-encapsulant interface thus enhancing extraction efficiency
Implementation Method 4
using materials with high refractive indices and thermal conductivity to enhance light extraction and modify the emission pattern
Data Source
AI summary
The present application discloses a light source comprising an LED die having an emitting surface and an optical element including a base, an apex, the base, and a converging side joining the base and the apex, wherein the base is optically coupled to the emitting surface. Furthermore, the optical element comprises a first section including the base and that is composed of a first material and a second section including the apex and that is composed of a second material.