Street Light Spectrum Design for Low-Scattering Warm Illumination
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Solution Overview
Problem
Outdoor light fixtures, such as street lights and road illumination lights, face challenges in suppressing light scattering due to the use of mercury-based light sources, necessitating a shift to safer alternatives that maintain efficiency and reduce discomfort to humans.
Innovation Solution
A light emitting device comprising a light emitting element with a specific wavelength range and a fluorescent material, configured to emit light with a correlated color temperature of 1,950 K or less, an average color rendering index of 70 or more, and scattering indices B/L and B/A of 0.151 or less and 0.060 or less, respectively, to minimize scattering and ensure effective illumination over long distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If LED light sources with broad spectrum emission are used to achieve high color rendering index, then the color rendering property is improved, but light scattering increases
Solution Approach 1:
The patent applies local quality by using multiple fluorescent materials with different emission characteristics (first fluorescent material with 570-680nm peak, second fluorescent material with 480-570nm peak) to create different spectral regions with controlled properties. Each fluorescent material region contributes differently to the overall spectrum, allowing localized optimization of color rendering while controlling scattering in specific wavelength ranges.
Solution Approach 2:
The patent changes spectral parameters by controlling the full width at half maximum (FWHM) of the light emission peak to be 110nm or less, and adjusting the correlated color temperature to 1950K or less. These parameter changes optimize the balance between color rendering (Ra≥70) and scattering suppression (B/A≤0.060) by narrowing the spectral bandwidth and adjusting the temperature characteristics.
2Object-generated harmful factors
If narrow bandwidth light emission is used to suppress scattering, then scattering is reduced, but color rendering capability deteriorates
Solution Approach 1:
The patent uses composite fluorescent materials comprising both a first fluorescent material (emitting 570-680nm) and a second fluorescent material (emitting 480-570nm). This composite approach combines the benefits of narrow bandwidth emission for scattering suppression with broad spectrum coverage for color rendering, achieving Ra≥70 while maintaining B/A≤0.060.
3Use of energy by moving object
If high correlated color temperature light is used to improve illumination efficiency, then energy efficiency is improved, but light scattering increases
Solution Approach 1:
The patent changes the correlated color temperature parameter to 1950K or less, which is lower than conventional high-efficiency LED temperatures. This parameter change reduces the proportion of short-wavelength blue light that causes scattering, while maintaining illumination efficiency through optimized fluorescent material combinations and controlled spectral bandwidth (FWHM≤110nm).
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 enables light fixtures to emit light with suppressed scattering, maintaining color rendering properties and reducing discomfort, allowing for efficient outdoor and indoor use near outdoor areas.
Implementation Method 1
a light emitting element having a light emission peak wavelength in a range of 400 nm or more and 490 nm or less
Implementation Method 2
a first fluorescent material having a light emission peak wavelength in a range of 570 nm or more and 680 nm or less
Data Source
Figure 1
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Figure 3A
AI summary
A light emitting device comprises a light emitting element having a light emission peak wavelength in a range of 400 nm or more and 490 nm or less and a first fluorescent material having a light emission peak wavelength in a range of 570 nm or more and 680 nm or less, and emits light having a correlated color temperature being 1,950 K or less, an average color rendering index Ra being 70 or more, a full width at half maximum of a light emission peak having the maximum light emission intensity in a light emission spectrum of the light emitting device being 110 nm or less, and a first scattering index B/L of an effective radiance B to a luminance L being 0.151 or less, wherein the luminance of light emitted by the light emitting device in a range of 300 nm or more and 800 nm or less in consideration of photopic standard specific luminous sensitivity of humans specified by CIE (Commission Internationale de l'Eclairage) is referred to as L, and the effective radiance of light emitted by the light emitting device in a range of 300 nm or more and 800 nm or less in consideration of a scattering intensity curve for wavelengths when the scattering intensity of Rayleigh scattering at a wavelength of 300 nm is 1 is referred to as B.