Wavelength Converter Coating for LED Edge Color Shift Correction
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Solution Overview
Problem
Shaped surface luminance LEDs in lighting applications, such as automotive lighting, suffer from unwanted color variation due to edge color shift and strong color over source variation, which affects system optical performance.
Innovation Solution
Applying a patterned blue dichroic filter (DCF) and anti-reflection (AR) coatings selectively on the peak luminance areas of LED dies, combined with strategic placement of these coatings to minimize flux loss and improve color transition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If shaped surface luminance LEDs are used to control luminance distribution, then luminance control is improved, but color over source variation increases
Solution Approach 1:
The patent applies different optical properties to different regions of the LED die by using a spatially inhomogeneous dichroic filter. The filter has varying reflectivity and transmission characteristics across the die surface, with peak luminance regions having different optical properties compared to non-peak regions. This local differentiation corrects color variation while maintaining the shaped luminance distribution.
2Manufacturing precision
If dichroic filter is applied to correct color variation, then color over source variation is reduced, but optical flux loss increases
Solution Approach 1:
Instead of applying a uniform dichroic filter across the entire LED die, the patent uses a spatially inhomogeneous filter that applies different optical properties only where needed. Peak luminance regions receive different filter characteristics compared to non-peak regions, correcting color variation locally while minimizing unnecessary optical flux loss in other areas.
Solution Approach 2:
The patent optimizes the dichroic filter parameters (reflectivity, transmission, spectral characteristics) to achieve color correction while minimizing flux loss. By carefully selecting and tuning these parameters, the filter corrects color over source variation to within acceptable tolerances while maintaining high optical efficiency.
3Manufacturing precision
If spatially inhomogeneous dichroic filter is used, then color correction is improved, but device complexity increases
Solution Approach 1:
The patent implements color correction through a spatially inhomogeneous dichroic filter that varies optical properties across the LED die surface. This approach achieves superior color correction by addressing local color variations in peak and non-peak luminance regions, while the filter can be integrated into the existing LED manufacturing process.
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
Reduces color over source variation by up to 35 points and maintains optical flux within 1% of conventional designs, enhancing system optical performance.
Implementation Method 1
The wavelength converter converts some of the pump light to a converted light having a differing color
Implementation Method 2
increases reflection of the pump light in special regions of peak luminance
Implementation Method 3
increases transmission of the pump light in spatial regions of low luminance
Data Source
AI summary
An LED die, a wafer of LED dies, and methods of manufacture are described. The LED die includes a semiconductor stack configured to emit a pump light when energized and a wavelength converter over the semiconductor stack. The wavelength converter converts some of the pump light to a converted light having a differing color. A spatially inhomogeneous dichroic filter on the wavelength converter, which at least one of: increases reflection of the pump light in special regions of peak luminance, increases reflection of the converted light in spatial regions of low luminance, increases transmission in at least a portion of the converted light in spatial regions of peak luminance, or increases transmission of the pump light in spatial regions of low luminance.