Color Correcting Optical Element for LED Lighting
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Solution Overview
Problem
LED lighting systems face challenges in producing uniform white light due to Color-over-Angle (CoA) variation, where light emitted from wavelength converting elements like phosphor materials exhibits color variation based on emission angle, leading to undesirable ring-like effects and increased complexity in correction methods.
Innovation Solution
A circular symmetric optical element is designed to redirect light by separating light into two portions based on emission angles, using calculated shapes to combine shorter and longer wavelengths, ensuring homogeneous color output in the far field, aligning with the central axis of the wavelength converting element and accounting for wavelength and flux distributions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a phosphor element with a flat light emission surface is used, then the structure is simple and manufacturing is easy, but the color output becomes angle dependent causing CoA variation
Solution Approach 1:
The optical element is divided into multiple regions with different optical properties. Specifically, it includes a first region with a first refractive index and a second region with a second refractive index different from the first, allowing different angular ranges of light to be redirected differently to achieve uniform color output across all emission angles.
Solution Approach 2:
Different regions of the optical element have locally optimized properties tailored to specific angular ranges. The first region handles light within a first angular range while the second region handles light within a second angular range, with each region having refractive indices specifically designed for its designated angular sector to ensure uniform color perception.
2Manufacturing precision
If grading the phosphor layer or using dichroic filters is applied for CoA correction, then color uniformity is improved, but the efficiency decreases and manufacturing complexity increases
Solution Approach 1:
The optical element integrates multiple functions into a single component. It simultaneously performs light redirection for different angular ranges and color uniformity correction, eliminating the need for separate dichroic filters or graded phosphor layers while maintaining manufacturing efficiency.
Solution Approach 2:
The optical element serves multiple purposes: it redirects light from the LED chip, corrects color uniformity across different emission angles, and maintains high light extraction efficiency. This multi-functional design avoids the need for additional correction components that would increase system complexity.
3Manufacturing precision
If microstructures are introduced on top of a collimating structure for CoA correction, then color uniformity is improved, but the manufacturing complexity and costs increase
Solution Approach 1:
Instead of introducing complex microstructures, the invention achieves CoA correction by changing the refractive index parameter across different regions of the optical element. The first and second regions have different refractive indices that are optimized for their respective angular ranges, providing a manufacturable solution through material selection rather than complex structuring.
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 optical element effectively corrects CoA variation, providing a homogeneous color output in the far field, reducing manufacturing complexity and costs, and is applicable to various light sources and wavelength converting elements.
Implementation Method 1
a first optical portion configured to receive and redirect light having emission angles from the wavelength converting element lower than tA, and a second optical portion configured to receive and redirect light having emission angles from the wavelength converting element higher than tA
Data Source
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AI summary
A circular symmetric optical element for redirecting light which is emitted by a light source through a wavelength converting element, wherein the emitted light have an average color cA and a wavelength distribution depending on an emission angle from the wavelength converting element. Light having the average color cA have an emission angle tA. The optical element comprises: a first optical portion configured to receive and redirect light having emission angles from the wavelength converting element lower than tA, and a second optical portion configured to receive and redirect light having emission angles from the wavelength converting element higher than tA, wherein the first and second optical portions are individually configured such that for light of each selected out-coupling angle of the optical element, there is light received and redirected by the first optical portion to the selected out-coupling angle of the optical element, and corresponding light received and redirected by the second optical portion to the selected out-coupling angle from the optical element such that the total light beam emitted from the optical element as seen in the far field have a homogeneous color.