Wavelength-Converted Light Emission for Balanced Visibility
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Solution Overview
Problem
Conventional light emitting devices using blue LEDs and fluorescent materials struggle to provide consistent visibility in both bright and dark environments, and fail to effectively convey specific states like charging status while minimizing impact on human circadian rhythms.
Innovation Solution
A light emitting device with a rare earth aluminate fluorescent material, having a specific composition, is used in conjunction with a light emitting element to produce light with a dominant wavelength between 400 nm and 500 nm, achieving a scotopic to photopic vision ratio of 6.5 or less and a melanopic ratio of 3.4 or less, ensuring visibility and minimizing circadian disruption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the S/P ratio is increased to improve visibility in mesopic environment, then visibility in dark place is improved, but the light may be perceived as dark in photopic vision and bright in scotopic vision
Solution Approach 1:
The patent applies parameter changes by precisely controlling the dominant wavelength of the light emitting element (400-500nm) and the composition of the rare earth aluminate fluorescent material (formula (I) with specific ranges for k, m, n, and p). These parameter adjustments optimize the spectral distribution to achieve an S/P ratio of 6.5 or less, balancing visibility performance across both scotopic and photopic vision conditions.
Solution Approach 2:
The patent uses composite materials by combining a light emitting element (blue light emitting diode) with a rare earth aluminate fluorescent material. This composite structure enables wavelength conversion from blue light (400-500nm) to green light, creating a mixed spectrum that simultaneously satisfies scotopic and photopic vision requirements while maintaining appropriate S/P ratio.
2Loss of information
If the light emitting device emits light with specific wavelength to notify specific state, then information transmission is improved, but the impact on human circadian rhythm may increase
Solution Approach 1:
The patent controls the melanopic ratio by adjusting the spectral distribution parameters - specifically the dominant wavelength (400-500nm) and the fluorescent material composition (formula (I) with controlled ratios of Lu, Ln, Ce, Al, and Ga). This ensures the melanopic ratio remains at 3.4 or less, minimizing circadian rhythm disruption while preserving the ability to convey state information through color variations.
3Ease of manufacture
If conventional blue LED and fluorescent material are used, then manufacturing simplicity is maintained, but consistent visibility in both bright and dark environments cannot be achieved
Solution Approach 1:
The patent employs a composite material system consisting of a blue light emitting element combined with a specifically formulated rare earth aluminate fluorescent material having composition (I). This composite approach maintains manufacturing simplicity while achieving reliable visibility consistency across different lighting conditions through optimized spectral characteristics and controlled S/P ratio.
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 device emits light that is bright in both scotopic and photopic vision, reducing perceived brightness differences and minimizing impact on human circadian rhythms, while effectively conveying specific states like charging status.
Implementation Method 1
a wavelength conversion member that is arranged on a light emitting side of the light emitting element and includes a rare earth aluminate fluorescent material
Implementation Method 2
a light emitting element having a dominant wavelength in a range of 400 nm or more and 500 nm or less
Implementation Method 3
a rare earth aluminate fluorescent material having a composition represented by the following formula (I): (Lu 1-p-n Ln p Ce n ) 3 (Al 1-m Ga m ) 5k O 12
Data Source
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AI summary
A light emitting device includes a light emitting element having a dominant wavelength in a range of 400 nm or more and 500 nm or less, and a wavelength conversion member that is arranged on the light emitting side of the light emitting element and includes a rare earth aluminate fluorescent material having a composition represented by the following formula (I), wherein the light emitting device emits light having a dominant wavelength in a range of 475 nm or more and 500 nm or less, and has an S/P ratio of 6.5 or less derived from the formula (1), which is the ratio of a luminous flux in scotopic vision relative to a luminous flux in photopic vision: (Lu1-p-nLnpCen)3(Al1-mGam)5kO12 (I) wherein in the formula (I), Ln represents at least one rare earth element selected from the group consisting of Y, La, Gd, and Tb, and the parameters k, m, n, and p satisfy 0.95 ≤ k ≤ 1.05, 0.05 ≤ m ≤ 0.70, 0.002 ≤ n ≤ 0.050, and 0 ≤ p ≤ 0.30 respectively.