Solid-State Filament Lighting With Local Phosphor Layers
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Solution Overview
Problem
Solid state lighting devices struggle to achieve homogeneous spectral composition in their luminous output due to variations in the thickness of the phosphor-containing resin coating, leading to noticeable spectral variations when projected onto surfaces or observed in motion, and diffusive coatings to address this issue compromise luminous efficiency.
Innovation Solution
A transmissive housing with further phosphor layers optically aligned with regions of reduced resin coating thickness to compensate for spectral variations, maintaining luminous efficiency by avoiding diffusive layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a diffusive coating is applied to the housing to homogenize spectral composition, then spectral uniformity is improved, but luminous efficiency deteriorates due to light losses
Solution Approach 1:
The patent applies phosphor layers locally at specific positions on the housing where resin coating thickness is reduced, rather than applying a uniform diffusive coating across the entire housing. This localized approach compensates for spectral variations only where needed, maintaining luminous efficiency in other regions.
Solution Approach 2:
The patent modifies the spectral composition by adding phosphor layers with specific characteristics at targeted locations, changing the local optical parameters to compensate for resin thickness variations without altering the overall luminous efficiency of the system.
2Stability of the object's composition
If the resin coating thickness is increased to improve spectral homogeneity, then spectral uniformity is improved, but luminous efficiency deteriorates due to increased light absorption
Solution Approach 1:
Instead of uniformly increasing resin coating thickness across the entire housing, the patent applies phosphor layers locally only at positions where the resin coating is thinner, thereby achieving spectral homogeneity without the energy losses associated with increased overall coating thickness.
3Stability of the object's composition
If a uniform phosphor coating is applied across the entire housing, then spectral composition is homogenized, but luminous efficiency deteriorates due to unnecessary light losses in regions with adequate resin thickness
Solution Approach 1:
The patent implements a selective phosphor coating strategy where phosphor layers are applied only at specific locations on the housing where resin coating thickness is insufficient, rather than applying a uniform coating everywhere. This localized application achieves spectral homogeneity while preserving luminous efficiency in regions where the resin coating is already adequate.
Solution Approach 2:
The patent applies phosphor coating partially rather than excessively across the entire housing surface, targeting only the specific regions that require spectral compensation, thereby avoiding unnecessary light losses in other areas.
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
Improves spectral uniformity and luminous efficiency by aligning additional phosphor layers with specific regions of the resin coating, ensuring consistent light emission without significant light loss.
Implementation Method 1
the light produced by the LEDs, e.g. blue light, may be spectrally converted by the phosphor particles in the resin, e.g. to produce white light
Implementation Method 2
the phosphor particles in the resin may be converted to produce white light
Implementation Method 3
providing a further phosphor layer on the housing for each region with a reduced thickness in the phosphor-containing resin coating such that such a further phosphor is optically aligned with such a region
Data Source
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AI summary
A lighting device (1) is disclosed comprising a transmissive housing (3) and a filament (10) within said transmissive housing. The filament comprises a transmissive substrate (20) carrying a plurality of solid state lighting elements (30) and a phosphor containing resin coating (40) enveloping said filament. The resin coating includes at least one region (42) leaking light produced by said solid state lighting elements that is unconverted by said phosphor and the transmissive housing carries a further phosphor layer (7) covering part of the transmissive housing for each of said regions of the resin coating, each of said further phosphor layers being arranged to receive said unconverted light leaking from at least one of said regions. Also disclosed is a method of manufacturing such a lighting device.