LED Light Extraction Using Microlens Array and Remote Phosphor
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Solution Overview
Problem
Current phosphor-converted white LED (pc-LED) technology is inefficient in the visible spectrum, resulting in low light output and decreased efficacy as temperature increases, necessitating larger LED chips or multiple LEDs and additional cooling mechanisms.
Innovation Solution
A light emitting apparatus with a light source and an optic device that directs short wavelength radiation into a down-conversion material, extracting back transferred radiation to enhance light output and efficacy, using a remote down-conversion material and a tailored optic device to capture and redirect radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If phosphor particles are randomly oriented and interspersed throughout epoxy, then the structure is simple and easy to manufacture, but light output efficiency is low and much primary radiation passes through without impinging on phosphor particles
Solution Approach 1:
The patent applies local quality by creating a structured arrangement where phosphor particles are positioned in specific locations rather than randomly distributed. The microlens array focuses light onto specific phosphor particles, creating localized high-intensity regions that maximize conversion efficiency while maintaining overall system simplicity
Solution Approach 2:
The patent uses preliminary action by pre-positioning phosphor particles in a structured array and pre-configuring microlenses to focus light onto these particles before the light emission process begins. This pre-arrangement ensures optimal light-phosphor interaction from the start, maximizing efficiency without requiring complex real-time adjustments
2Illumination intensity
If a larger LED chip or multiple LED chips are used to achieve comparable light output, then light output increases, but device complexity and cooling requirements increase
Solution Approach 1:
The patent changes the key parameter of light-phosphor interaction by introducing microlenses that concentrate light onto phosphor particles. This parameter change in light delivery mechanism allows a single small LED chip to achieve the light output of multiple larger chips, reducing device complexity while maintaining high illumination intensity
Solution Approach 2:
The patent uses an array of microlenses that replicate the light-focusing function multiple times across the phosphor layer. Each microlens creates a focused spot on a phosphor particle, and the collective effect of many such copies achieves high overall light output without requiring a single large LED chip
3Temperature
If direct energy absorbing cooling is incorporated to handle temperature rise, then temperature control is achieved, but device complexity and cost increase
Solution Approach 1:
The patent converts the harmful effect of heat generation into a beneficial outcome by using the heat to excite phonons in the phosphor material, which enhances the down-conversion efficiency. This approach transforms the cooling requirement into a self-regulating thermal management system, reducing the need for active cooling mechanisms
Solution Approach 2:
The patent implements self-service by designing a system where the LED-chip array and phosphor particle array work together autonomously. The structured arrangement allows the system to self-optimize light extraction and thermal management through its geometric configuration, eliminating the need for external cooling systems
4Reliability
If phosphor conversion efficiency drops dramatically above 90°C threshold, then temperature management becomes critical, but this limits the operational range and requires additional cooling infrastructure
Solution Approach 1:
The patent changes the thermal parameter management by using phonon-mediated energy transfer that becomes more efficient at higher temperatures. The structured LED-phosphor arrangement allows the system to operate reliably across a wide temperature range by exploiting the temperature-dependent properties of phonon interactions in the phosphor material
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
Significantly increases light output and luminous efficacy of pc-white LEDs by extracting phosphor-emitted and back-scattered radiation, achieving a 1500-lumen package at 150 lm/W, while reducing the need for larger LED chips or cooling mechanisms.
Implementation Method 1
Conversion of primary emissions of the LED to longer wavelengths is commonly referred to as down-conversion of the primary emission
Implementation Method 2
The optic device may be configured to extract the back transferred radiation from the core of the waveguide
Implementation Method 3
solid state light emitting devices, including solid state lamps having light emitting diodes (LEDs)
Data Source
Figure 1~2
Figure 3
Figure 4A~4E
AI summary
A light emitting apparatus having a light source for emitting short wavelength radiation and an optic device configured to receive the radiation emitted from the light source. A device directs at least some of the short wavelength radiation emitted from the light source into the optic device and a down conversion material receives at least some of the short wavelength radiation directed into the optic device in one spectral region and emits the radiation in another spectral region.