Remote Phosphor Lighting Device with Reflective Filter
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Solution Overview
Problem
Conventional LED lamps with external phosphor regions appear yellow when switched off, which is undesirable, and internal phosphor regions are thermally disadvantaged due to lack of cooling by ambient air.
Innovation Solution
A lighting device with a semiconductor light source, a remote phosphor region, and a partly reflective filter that reflects primary light back towards the phosphor region, reducing the need for phosphor material and improving appearance by minimizing the yellow color impression when off, and allowing for beam shaping and efficient wavelength conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the phosphor region is placed on the exterior of the outer bulb, then the yellow appearance is strong, but the phosphor can be cooled by ambient air
Solution Approach 1:
A light-transmissive cover is introduced as an intermediary element between the phosphor region and the external environment. This cover allows the phosphor to be positioned externally for cooling while preventing direct visual contact that would cause the yellow appearance. The cover transmits light while masking the phosphor's color.
Solution Approach 2:
The light-transmissive cover is applied selectively to cover only the phosphor region while leaving other parts of the bulb transparent or unaffected. This localized approach allows different parts of the bulb to have different optical properties - the cover area masks the yellow phosphor, while other areas remain transparent for light transmission.
2Object-generated harmful factors
If the phosphor region is covered by a diffusely scattering bulb, then the yellow appearance is reduced, but the phosphor cannot be cooled by ambient air
Solution Approach 1:
Instead of using a diffusely scattering bulb that would trap heat, a light-transmissive cover is used as a mediator. This cover provides the optical function of masking the yellow appearance while maintaining thermal functionality by allowing ambient air to flow around and cool the externally positioned phosphor region.
3Illumination intensity
If more phosphor material is used to achieve the desired color locus, then the color conversion is sufficient, but the costs for phosphors increase
Solution Approach 1:
A reflective layer is positioned behind the phosphor region to reflect unconverted primary light back onto the phosphor. This creates a feedback loop where light that initially missed the phosphor is given another opportunity to be converted, increasing the overall conversion efficiency and reducing the amount of phosphor material needed to achieve the desired color output.
Solution Approach 2:
The reflective layer ensures that the useful action of wavelength conversion continues by redirecting unconverted light back through the phosphor region. This extends the interaction path of the light with the phosphor, ensuring more complete conversion without requiring additional 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
The solution reduces phosphor costs, minimizes yellow color appearance when the device is off, and allows for precise control of light color and beam shaping, while maintaining efficient wavelength conversion and cooling of the phosphor region.
Implementation Method 1
at least one phosphor region spaced apart from the at least one semiconductor light source and serving for at least partly converting the primary light into light in a second spectral range
Implementation Method 2
the at least one filter is partly reflective at least to the primary light... By means of a filter, the light incident on the lighting device from outside, at least in the spectral range encompassing the primary light, is reflected back
Data Source
AI summary
A lighting may include at least one semiconductor light source which emits primary light, at least one phosphor region spaced apart from the at least one semiconductor light source and serving for at least partly converting the primary light into secondary light, and at least one filter disposed downstream of the at least one phosphor region, wherein the at least one filter is partly reflective at least to the primary light.