Shaped Phosphor Element Angular Color Uniformity
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Solution Overview
Problem
Conventional phosphor-converted LEDs suffer from poor angular color uniformity due to the hemispherical shape of phosphor particles, leading to non-uniform color distribution when viewed from different angles, which requires additional elements like diffusers to homogenize color characteristics, increasing cost and reducing efficiency.
Innovation Solution
The use of phosphor elements with a curved outer contour defining a portion of a hemisphere and a planar base with a non-zero centroid z-offset, combined with a cylindrical cutoff, to engineer the angular intensity distribution of light emitted from both the light-emitting die and the phosphor, achieving a uniform color temperature across viewing angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional hemispherical phosphor particles are used, then light extraction efficiency is improved, but angular color uniformity deteriorates
Solution Approach 1:
The patent applies asymmetry by positioning the light-emitting element off-center within the phosphor element, creating a non-symmetric configuration where the LEE is located at a distance from the base of the phosphor element. This asymmetric positioning, combined with the specific curved outer contour, balances the angular distribution of light from the LEE and phosphor, achieving uniform chromaticity across viewing angles while maintaining high light extraction efficiency.
Solution Approach 2:
The patent utilizes spheroidality by defining the outer contour of the phosphor element as a curved surface that defines only a portion of a hemisphere. This curved geometry, with specific radius and centroid z-offset parameters, optimizes the angular intensity distribution of emitted light, ensuring uniform color temperature and chromaticity across different viewing angles while maintaining efficient light extraction.
2Stability of the object's composition
If additional elements like diffusers are added to homogenize color, then angular color uniformity is improved, but device complexity and cost increase
Solution Approach 1:
The patent merges the functions of the phosphor element and the light-emitting element into a single integrated structure. The phosphor element's curved outer contour and off-center LEE positioning simultaneously achieve light extraction and angular color uniformity, eliminating the need for separate diffusers or color-homogenizing elements, thus reducing device complexity and cost.
Solution Approach 2:
The phosphor element serves multiple functions: it converts wavelength, extracts light, and simultaneously provides angular color uniformity through its engineered curved geometry and LEE positioning. This multi-functionality eliminates the need for additional dedicated components for color homogenization, simplifying the overall device structure.
3Loss of energy
If phosphor particles are arranged in a hemisphere, then light extraction efficiency is improved, but chromaticity uniformity with viewing angle deteriorates
Solution Approach 1:
The patent applies local quality by creating regions with different optical properties within the phosphor element. The off-center positioning of the LEE creates a specific spatial distribution where the phosphor material density and geometry are optimized at different locations to balance the angular intensity distribution, achieving uniform chromaticity while maintaining high light extraction efficiency.
Solution Approach 2:
The curved outer contour of the phosphor element, defining a portion of a hemisphere with specific radius and centroid z-offset, creates controlled optical paths that balance the angular distribution of light. This curved geometry ensures that light from both the LEE and phosphor combines to produce uniform color temperature and chromaticity across viewing angles.
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 configuration ensures a uniform color temperature with minimal deviation in chromaticity across a wide angular range, eliminating the need for additional elements and maintaining high light-extraction efficiency.
Implementation Method 1
an LED combined with a wavelength-conversion material generates white light by combining the short-wavelength radiant flux (e.g., blue light) emitted by the semiconductor LED with long-wavelength radiant flux (e.g., yellow light) emitted by the wavelength conversion material
Implementation Method 2
The wavelength-conversion material is generally one or more phosphor particles
Implementation Method 3
The hemispherical shape is used because it generally results in relatively high light extraction efficiency because of reduced total internal reflection (TIR) at the phosphor/air interface
Implementation Method 4
Such particles emit with a substantially isotropic distribution
Data Source
AI summary
In accordance with certain embodiments, a phosphor element at least partially surrounding a light-emitting die is shaped to influence color-temperature divergence.