Solid State Lighting Devices with Negative Planckian Offset
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Solution Overview
Problem
Conventional solid state lighting devices struggle to replicate the desirable illumination characteristics of natural light sources, such as daylight and incandescent lamps, as they often produce color points coincident with the blackbody locus, leading to inadequate color rendering and gamut area index, which limits their ability to accurately illuminate colors and provide aesthetically pleasing light.
Innovation Solution
The development of solid state lighting devices that include at least one electrically activated solid state light emitter and a lumiphor, with emissions arranged to achieve a color point in a desired correlated color temperature range (CCT) that is non-coincident with the blackbody locus, utilizing a negative Planckian offset Delta u′v′ value and notch filtering materials to enhance color rendering index (CRI Ra) and gamut area index (GAI), while maintaining high luminous efficacy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional solid state lighting devices use single or simple lumiphor combinations, then device complexity is reduced, but color rendering quality and gamut area index values deteriorate
Solution Approach 1:
The patent combines multiple electrically activated solid state light emitters (first and second emitters with different dominant wavelengths) with multiple lumiphors (first and second lumiphors with different peak wavelengths) to create a composite lighting system. This merging of multiple light sources and lumiphoric materials enables improved color rendering and gamut area index values while maintaining manageable device complexity through systematic integration.
Solution Approach 2:
The patent employs composite lumiphor systems where multiple lumiphors with different emission characteristics are combined. The first lumiphor has a first peak wavelength and the second lumiphor has a second peak wavelength, creating a composite material system that produces enhanced spectral output. This composite approach allows simultaneous achievement of high color rendering index and gamut area index values.
2Illumination intensity
If multiple electrically activated solid state light emitters and lumiphors are used to achieve specific color temperature and negative Planckian offset, then color rendering index and gamut area index values improve, but device complexity increases
Solution Approach 1:
The patent assigns specific functional roles to different components: the first solid state light emitter with dominant wavelength in 430-480 nm range stimulates the first lumiphor, while the second solid state light emitter with dominant wavelength in 560-630 nm range stimulates the second lumiphor. Each component is optimized for its specific function, allowing the system to achieve high color rendering and gamut area index values through localized optimization rather than uniform complexity.
Solution Approach 2:
The patent systematically varies key parameters including dominant wavelengths of solid state emitters (430-480 nm for first emitter, 560-630 nm for second emitter), peak wavelengths of lumiphors, correlated color temperature (2,500K to 10,000K), and Planckian offset values. By optimizing these parameters, the invention achieves high color rendering index and gamut area index values while controlling device complexity through parameter selection rather than component proliferation.
3Ease of manufacture
If conventional lighting sources with color points on blackbody locus are used, then manufacturing simplicity is maintained, but color rendering accuracy and visual vividness deteriorate
Solution Approach 1:
Instead of placing the color point on the blackbody locus as in conventional lighting, the patent inverts this approach by positioning the color point with a negative Planckian offset (below the blackbody locus). This inversion strategy, combined with multiple emitters and lumiphors, achieves superior color rendering accuracy and visual vividness while maintaining manufacturing simplicity through systematic design.
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
These devices achieve improved color rendering and gamut area index values, providing more accurate color representation and aesthetically pleasing light with a CCT range from 2,500K to 10,000K, exceeding traditional lighting devices in terms of CRI Ra and GAI, and offering a luminous efficacy of at least 60 lumens per watt.
Implementation Method 1
Solid state emitters may include lumiphoric materials (also known as lumiphors) that absorb a portion of emissions having a first peak wavelength emitted by the emitter and re-emit light having a second peak wavelength that differs from the first peak wavelength
Data Source
AI summary
Solid state lighting devices include at least one electrically activated solid state light emitter and at least one lumiphor (or multiple electrically activated emitters optionally devoid of a lumiphor), with resulting emissions arranged to attain a color point in a desired CCT range (e.g., from 2,500K to 10,000K) that is non-coincident with a blackbody or Planckian locus, preferably with a negative Planckian offset Delta u′v′ value (below the Planckian locus) according to a CIE 1976 chromaticity diagram, such as a value in a range of no greater than negative 0.01.