Curved Luminescent Rod Core-Shell Design for Light Extraction
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Solution Overview
Problem
Current luminescent concentrators with rectangular cross-sections suffer from low optical efficiency due to significant light loss through total internal reflection, with only 32% of generated light escaping through non-TIR cones and the remaining locked-in light being difficult to extract efficiently.
Innovation Solution
A lighting device featuring an elongated light transmissive body with a curved side face and a core-shell configuration, where the luminescent material concentration is higher in the shell and lower or zero in the core, enhances light outcoupling efficiency by guiding luminescent radiation through total internal reflection and using facets or optical elements like CPCs to redirect locked-in light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a rectangular cross-section luminescent concentrator is used, then the structure is simple and easy to manufacture, but light extraction efficiency is low due to total internal reflection
Solution Approach 1:
The patent applies curvature by transitioning from a rectangular cross-section to a circular cross-section for the luminescent concentrator rod. This curved geometry eliminates the sharp corners and flat surfaces of rectangular designs that cause significant total internal reflection, thereby improving light extraction efficiency while maintaining manufacturing feasibility through established circular rod fabrication processes
Solution Approach 2:
The patent implements a core-shell configuration where the luminescent material concentration varies spatially: the core region has zero or low concentration while the shell region has high concentration. This local differentiation optimizes light propagation in the core (minimizing reabsorption) while maintaining efficient light generation in the shell, directly addressing the light extraction efficiency problem
2Illumination intensity
If luminescent material concentration is increased to improve light generation, then more light is produced, but light extraction becomes more difficult due to increased total internal reflection
Solution Approach 1:
The patent resolves this contradiction by creating a core-shell structure with spatially varying luminescent material concentration. The shell region contains high concentration for efficient light generation, while the core region has zero or low concentration to minimize total internal reflection and facilitate light extraction. This local differentiation allows simultaneous optimization of both light generation and extraction
Solution Approach 2:
The patent segments the luminescent concentrator into distinct functional regions: a core region and a shell region. This segmentation allows independent optimization of each region's properties - the core for light propagation and extraction, and the shell for light generation - thereby resolving the contradiction between light generation intensity and extraction efficiency
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 curved side face design and core-shell configuration increase light extraction efficiency, potentially achieving up to 84% optical efficiency compared to 68% in rectangular designs, with facets further improving output light distribution and etendue.
Implementation Method 1
the elongated light transmissive body comprises a luminescent material configured to convert at least part of a light source light selected from one or more of the UV, visible light, and IR received by the elongated light transmissive body into luminescent material radiation
Implementation Method 2
the luminescent element is configured to guide at least part of the luminescent material radiation to the first radiation exit window by total internal reflection
Data Source
Figure 1A~1B
Figure 1C
Figure 1D~1E
AI summary
The invention provides a lighting device (1) comprising a light source configured to provide light source light and a luminescent element (5) comprising an elongated light transmissive body (100), the elongated light transmissive body (100) comprising a side face (140), wherein the elongated light transmissive body (100) comprises a luminescent material (120) configured to convert at least part of the light source light (11) selected from one or more of the UV, visible light, and IR received by the elongated light transmissive body (100) into luminescent material radiation (8). The side face comprises the radiation input face (111), and the body further comprises a first face (141) and a second face (142) defining a length of the body, wherein the second face comprises a first radiation exit window (112). The side face comprises a curvature with a radius r, and the concentration of the luminescent material is chosen such that at least 80% of the source light is absorbed within a first length x from the side face, wherein x/r <= 0.4 applies.