Directional Wavelength Conversion for LED Brightness
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Solution Overview
Problem
Solid-state illumination devices, such as LED arrays, face challenges in achieving sufficient brightness for directional applications due to the decrease in average brightness with increased effective emitting area and heat-induced reduction in wavelength converting efficiency.
Innovation Solution
The implementation of a light source system that includes light couplers with compound parabolic reflecting surfaces to efficiently collect and collimate light, wavelength selective filters to direct converted light forward, and a cavity of wavelength converting material to enhance brightness, preventing light loss and thermal degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multiple LEDs are used to increase total output lumen, then the total light output is improved, but the average brightness significantly decreases due to increased effective emitting area
Solution Approach 1:
The invention divides the illumination system into multiple independent LED modules, each with its own wavelength conversion cavity. This segmentation allows each module to maintain high brightness while the aggregate system provides increased total lumen output. Each module operates as an independent brightness source that can be individually optimized.
Solution Approach 2:
The invention transitions from planar LED array arrangement to three-dimensional cavity structures with wavelength conversion materials. By creating vertical cavities above each LED, the system achieves brightness enhancement in the vertical dimension while maintaining compact horizontal footprint, effectively resolving the brightness dilution problem of large-area arrays.
2Quantity of substance
If driving current is increased to improve light output, then total lumen is improved, but LED chip temperature increases causing phosphorescent material to reduce wavelength converting efficiency and potentially be damaged
Solution Approach 1:
The invention extracts the wavelength conversion function from the immediate vicinity of the LED chip by placing phosphorescent materials in separate cavities at controlled distances. This spatial separation removes the heat-sensitive conversion process from the high-temperature LED chip environment, allowing high current operation without compromising conversion efficiency or material integrity.
Solution Approach 2:
The invention introduces optical cavities with controlled reflectivity as intermediary structures between the LED chip and the wavelength conversion materials. These cavities act as thermal and optical mediators, directing light efficiently while maintaining physical separation that protects the phosphorescent materials from direct thermal exposure to the LED chip.
3Loss of energy
If wavelength converting material is placed directly contacting the LED chip to convert wavelength, then the conversion is efficient, but the material is exposed to high heat and may be damaged
Solution Approach 1:
The invention extracts the wavelength conversion function from the immediate vicinity of the LED chip by placing phosphorescent materials in separate cavities at controlled distances. This spatial separation removes the heat-sensitive conversion process from the high-temperature LED chip environment, allowing high current operation without compromising conversion efficiency or material integrity.
Solution Approach 2:
The invention implements thermal protection by pre-establishing controlled air gaps and using cavity structures with appropriate reflectivity before thermal damage can occur. The cavity design provides beforehand thermal cushioning that maintains conversion efficiency while preventing heat-induced material degradation.
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 solution significantly enhances light brightness and efficiency by ensuring that converted light propagates forward, reducing thermal impact on wavelength converting materials and allowing scalable output with minimal light loss.
Implementation Method 1
The light at the first wavelength passing through the filters interacts with the wavelength converting material and generates the light of the second wavelength that is different from the first wavelength
Implementation Method 2
Exiting LED light that is substantially perpendicular to the LED chip surface is directly applied to the compound parabolic reflector and is collimated
Implementation Method 3
The LED light that is substantially parallel to LED chip surface strikes the light tunnel portion and is guided into the parabolic reflecting portion through one or multiple reflections and is also collimated
Implementation Method 4
The wavelength selective filters reflect the light with the second wavelength and prevent the light with second wavelength from going back to the light couplers and then back to the light source such as LEDs
Data Source
AI summary
An LED based illumination system with enhanced brightness is described. The system includes one or more light sources such as LEDs, one or more light couplers for efficiently collecting and collimating the light from the light sources, one or more wavelength selective filters, one or more light concentrators that focus the collimated light, and a cavity made of a layer of wavelength converting material such as a phosphorescent material located at the focus planes of the light concentrators. Each light coupler includes a light tunnel portion and a compound parabolic reflecting portion, and effectively collects and collimates light emitted by the LED in all directions. The wavelength selective filters pass the collimated light from the light sources and reflect light of a second wavelength generated by the phosphorescent material. The lights of both wavelengths exit the light cycling cavity through an aperture.