Selective Index Matching Material for LED Color Shift Control
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Solution Overview
Problem
Conventional LED lighting systems using multiple solid state light sources often produce undesirable, unnatural-looking colors and suffer from reduced light intensity due to internal reflections, making it challenging to achieve energy-efficient and aesthetically pleasing white light output.
Innovation Solution
A solid state lighting device with a plurality of solid state light emitters, where at least one emitter has an index matching material in the optical path to enhance light extraction and another without, to control color shift and brightness, using a single type of light source, such as blue LEDs, and phosphors to produce white light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If index matching material is used to improve light extraction efficiency, then light intensity is improved, but color shift increases due to reduced internal phosphor excitation
Solution Approach 1:
The patent applies index matching material selectively to only certain LED emitters within the array, rather than uniformly to all emitters. This local differentiation allows specific emitters to have enhanced light extraction while others maintain internal phosphor excitation, thereby achieving overall color consistency while improving total light intensity.
Solution Approach 2:
The patent modifies the optical parameters of specific LED emitters by applying index matching material, changing their light extraction characteristics. This parameter change enables selective optimization of light intensity for certain emitters while preserving the color-shifting function in other emitters, resolving the contradiction between intensity and color consistency.
2Stability of the object's composition
If multiple surfaces are used to combine light from multiple LED sources, then uniform light output is improved, but internal reflections increase causing yellowing and reduced intensity
Solution Approach 1:
The patent differentiates the optical treatment of different LED emitters by applying index matching material to specific ones. This local quality approach optimizes the light extraction path for selected emitters, reducing unnecessary internal reflections and energy loss while still achieving uniform overall light output through the combined emission of multiple emitters.
3Stability of the object's composition
If internal reflections are increased to improve light mixing, then uniformity is improved, but color temperature shifts occur due to additional phosphor excitation
Solution Approach 1:
By selectively applying index matching material to specific LED emitters, the patent creates local variations in light extraction efficiency. This allows certain emitters to contribute more directly emitted light with minimal phosphor interaction, while others contribute more phosphor-converted light, achieving color temperature consistency while maintaining uniformity.
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 provides a brighter, natural-looking white light with reduced color shift, improving light intensity and aesthetic appeal while maintaining energy efficiency using a single type of solid state light source.
Implementation Method 1
An index matching material for matching the index of refraction of the light transmissive solid is provided in an optical path between a light emission output of at least one first solid state light emitter and each surface of the light transmissive solid arranged to receive light from the at least one first solid state light emitter
Implementation Method 2
Phosphors absorb excitation energy then re-emit the energy as radiation of a different wavelength. For example, a blue light absorbing phosphor can emit yellow light
Data Source
AI summary
Where a lighting device uses solid state emitters and an optic processes light from the emitters, it may improve efficiency in light extraction from the emitters to have an index of refraction matching material in between emitter output and a surface of solid of the optic that receives emitted light. However, such improved out-coupling or extraction efficiency may cause an overall color shift in the output of the overall lighting device, for example, if improved emitter output reduces internal reflection and associated internal phosphor excitation. To reduce the color shift in the output of the lighting device, the device may have index matching material used in association with one or some of the solid state light emitters but not all of the emitters, so that the combined light output of the device exhibits a desired spectral characteristics, e.g. remains a desirable color of white light.