3D Scattering Element and Convex Extractor for SSL Light Extraction
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Solution Overview
Problem
Existing solid-state lighting (SSL) devices face challenges such as light-energy losses due to Stokes loss, self-heating, dependence on operating temperature, degradation of phosphors, and unwanted light propagation directions.
Innovation Solution
A lighting device incorporating one or more light-emitting elements (LEE) and a scattering element with a matrix of phosphor embedded in dielectric material, where the phosphor absorbs pump light and emits converted light, and an optical extractor with a convex output surface that impinges mixed light at incident angles smaller than or equal to the critical angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If light is generated within optically dense material to achieve high brightness, then luminous efficacy is improved, but light extraction efficiency deteriorates due to total internal reflection
Solution Approach 1:
The patent introduces an optical extractor as an intermediary component between the optically dense scattering element and the ambient environment. The extractor has a convex output surface with radius of curvature greater than the radius of the extraction interface, which mediates the light extraction process by reducing incident angles and enabling light to escape the optically dense material without total internal reflection
Solution Approach 2:
The optical extractor employs a convex output surface with specific curvature (radius of curvature greater than the extraction interface radius) to geometrically transform light propagation. This curvature modifies the incident angles of light rays, converting high-angle internally reflected rays into lower-angle exiting rays that can escape the device efficiently
2Illumination intensity
If phosphor is used for wavelength conversion to generate white light, then color quality is improved, but light-energy losses occur due to Stokes loss
Solution Approach 1:
The patent embeds phosphor particles locally within a scattering element matrix rather than using a separate phosphor layer. This local integration allows precise control of phosphor distribution and concentration, optimizing wavelength conversion while minimizing Stokes loss through reduced light path length and improved spatial utilization of converted light
Solution Approach 2:
The patent merges the phosphor conversion function with the light scattering and extraction functions into a single integrated scattering element. The phosphor-embedded scattering element simultaneously performs wavelength conversion, light scattering for homogenization, and works with the optical extractor to maximize light extraction, eliminating the need for separate components and reducing overall energy losses
3Adaptability or versatility
If light is emitted in random directions from phosphor, then omnidirectional illumination is achieved, but directionality control deteriorates
Solution Approach 1:
The patent introduces asymmetry through the optical extractor's convex output surface geometry. While the scattering element maintains symmetry for omnidirectional light generation, the asymmetric extraction geometry preferentially directs light outward in useful directions while allowing some backward-directed light to be reflected back into the scattering element for secondary extraction opportunities
Solution Approach 2:
The patent adds a geometric dimension through the convex optical extractor surface that transforms the light extraction process. The curved surface in the third dimension (radius of curvature) modifies the angular distribution of exiting light, providing directionality control without constraining the omnidirectional nature of phosphor emission
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 solution efficiently provides broadband, homogenized light across a broad range of angles, reducing light-energy losses and enhancing light directionality, thereby improving the efficacy and durability of SSL devices.
Implementation Method 1
The phosphor is configured to absorb at least a portion of the pump light and to emit converted light with converted light wavelengths longer than pump light wavelengths
Implementation Method 2
An output surface of the optical extractor is arranged and shaped relative to the extraction interface such that the mixed light received by the optical extractor through the extraction interface impinges on the output surface at incident angles smaller than or equal to the critical angle θC = arcsin(nE/nO)
Data Source
Figure 1A
Figure 1B
Figure 2A~2B
AI summary
A lighting device includes (1) one or more solid-state lighting (SSL) devices, (2) a thick, for example prism- or cylinder- or spherical- or dome-shaped scattering element, and (3) an optical extractor with a convex output surface.