Lighting Device Optical Filters for Off-State Color Uniformity
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Solution Overview
Problem
Lighting devices with different types of light sources, such as white and red LEDs, often have distinct visual appearances in their off-state, which can be undesirable, and using a scattering layer to hide this difference results in extra light loss from the white LEDs.
Innovation Solution
A lighting device configuration where a subset of light sources with optical filters are used to ensure that the off-state color appearance of all light sources is identical, with each optical filter associated with a respective second light source and selected to convert less than 30% of the second light source light, matching the off-state color appearance of the first light sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If different types of light sources (e.g., white and red LEDs) are used to provide high quality light with CRI beyond 90 and saturated white light, then lighting quality and efficiency are improved, but the visual appearance in off-state becomes non-uniform and less appreciated
Solution Approach 1:
The patent applies color changes by introducing optical filters on the light emitting surfaces of second light sources (e.g., red LEDs) to match the color appearance of first light sources (e.g., white LEDs) in off-state. The optical filters are selected to have the same color appearance as the first light sources, thereby creating visual uniformity while allowing different types of LEDs to be used for high quality lighting.
2Shape
If a scattering layer is configured over both types of LEDs to hide the appearance difference, then visual uniformity is improved, but extra light loss occurs from the white LED
Solution Approach 1:
The patent applies local quality by placing optical filters only on the light emitting surfaces of second light sources (e.g., red LEDs) rather than using a scattering layer over all light sources. This localized approach allows the second light sources to match the color appearance of first light sources in off-state without causing light loss to the first light sources, thereby achieving visual uniformity while preserving lighting efficiency.
3Shape
If optical filters are used on second light sources to match off-state color appearance, then visual uniformity is improved, but light conversion loss occurs if filters convert too much light
Solution Approach 1:
The patent applies parameter changes by selecting optical filters with specific transmission characteristics that convert less than 30% (preferably less than 20%, more preferably less than 10%) of the second light source light. This parameter optimization ensures that the optical filters achieve color matching in off-state while minimizing light loss and maintaining lighting efficiency.
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 allows all light sources to appear as having the same color in their off-state, maintaining the visual homogeneity while minimizing light loss, enabling the use of different types of LEDs like white and red LEDs to appear as the same type of light source.
Implementation Method 1
the one or more second light sources comprise one or more optical filters, wherein especially the one or more optical filters are selected to convert less than 30%, such as less than 20%, such as especially less than 10%, of the second light source light
Implementation Method 2
the one or more optical filters are selected to convert less than 30%, such as less than 20%, such as especially less than 10%, of the second light source light
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 2C
AI summary
The invention provides a lighting device (1) comprising a plurality of different light sources (10) with a first subset (100) of one or more first light sources (110) configured to provide first light source light (111) and a second subset (200) of one or more second light sources (210) configured to provide second light source light (211) having a spectral distribution different from the first light source light (111), wherein the one or more first light sources (110) have a light-source off-state color appearance, wherein the one or more second light sources (210) comprise one or more optical filters (305), wherein the one or more optical filters (305) are selected to convert less than 10% of said second light source light (211), wherein each optical filter (305) is associated with a respective second light source (210), and wherein the one or more optical filters (305) have the same color appearance as the off-state color appearance of the one or more first light sources (110).