Textured Phosphor Surface Reduces Total Internal Reflection
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Solution Overview
Problem
The total internal reflection (TIR) phenomenon in solid state lighting devices reduces luminous efficiency and can generate heat, particularly when blue light from LEDs interacts with flat phosphor surfaces, impacting the overall lighting output.
Innovation Solution
A phosphor layer with a textured surface, featuring continuously shaped configurations such as hemispheres or triangles, is used to minimize TIR between the solid state light emitter and the phosphor layer, enhancing luminous output by altering the incident ray angles and reducing reflective losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a flat phosphor surface is used, then the device structure is simple and easy to manufacture, but total internal reflection occurs reducing luminous efficiency
Solution Approach 1:
The patent applies curvature by forming the phosphor layer surface as a textured surface with continuous curved configurations rather than a flat surface. This curvature modifies the incident angles of light rays at the phosphor-LED interface, reducing total internal reflection and improving light extraction efficiency while maintaining manufacturing feasibility through deposition processes.
2Loss of energy
If a textured surface is introduced to reduce TIR, then luminous efficiency improves, but manufacturing complexity increases
Solution Approach 1:
The patent changes the surface geometry parameter of the phosphor layer from flat to textured with specific curvature radii (e.g., 1-10 micrometers). This parameter modification enables reduced TIR while the continuous nature of the texture and compatibility with existing deposition techniques keeps manufacturing complexity manageable.
3Productivity
If a textured surface configuration is used, then light extraction efficiency improves, but the device structure becomes more complex
Solution Approach 1:
The continuous curved configurations on the phosphor layer surface extract light more effectively by modifying incident angles, while the uniform and regular nature of these curves (rather than random or discontinuous structures) helps control device complexity and maintains manufacturability.
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 textured surface design effectively reduces TIR, leading to improved visible light output and heat management, thereby increasing the efficiency of solid state lighting devices.
Implementation Method 1
A problem associated with lighting output from a solid state light emitter or LED is the total internal reflection ("TIR") phenomenon. When a light ray or beam crosses between two different materials with two different medium having different refractive indices, the TIR phenomenon occurs.
Data Source
AI summary
An optical device deploring a phosphor layer having a textured surface to improve output of visual light is disclosed. A light emitting device includes a solid state light emitter and a phosphor layer. The solid state light emitter, for example, is configured to convert electrical energy to optical light. The phosphor layer includes a first surface and a second surface, wherein the first surface, for example, is the top surface while the second surface is the bottom surface. The phosphor layer is disposed over the solid state light emitter for generating luminous light in response to the optical light. The first surface of the phosphor layer, in one embodiment, is configured to include a texture, which has similarly shaped uniform configurations, capable of reducing total internal reflection.