Phosphor-Converted Light Source for Age-Related Blue Sensitivity Loss
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Solution Overview
Problem
The discoloration of the crystalline lens due to aging reduces visual sensitivity to blue light, leading to reduced discernability of displayed letters or objects, especially in elderly individuals.
Innovation Solution
A light emitting device comprising a light emitting element with a peak emission wavelength between 440 nm to 470 nm and a wavelength conversion member with specific phosphors, adjusting the luminous intensity ratios at 480 nm, 530 nm, and 550 nm to enhance the blue component of the light emitted.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a blue light emitting LED combined with yellow light emitting phosphor is used, then white light is emitted, but the visual sensitivity to blue light is reduced in elderly individuals
Solution Approach 1:
The patent changes the spectral parameters of the emitted light by carefully selecting phosphor materials and adjusting their ratios. Specifically, it uses a green phosphor with peak wavelength 520-540nm and a red phosphor with peak wavelength 610-650nm in specific proportions to modify the emission spectrum, thereby improving blue light sensitivity while maintaining white light emission
Solution Approach 2:
The patent employs a composite phosphor system consisting of multiple phosphor materials (green phosphor and red phosphor) combined with the blue LED. This composite approach allows optimization of the overall emission spectrum to compensate for age-related blue light sensitivity loss while maintaining efficient white light generation
2Illumination intensity
If the luminous intensity ratio at 550 nm is increased, then the perceived brightness improves, but the discernability of letters decreases
Solution Approach 1:
The patent optimizes the spectral distribution parameters by controlling the luminous intensity ratios at specific wavelengths. It sets the ratio of luminous intensity at 480nm to peak intensity between 0.05-0.20, at 530nm between 0.20-0.35, and at 550nm between 0.23-0.38, creating a balanced spectrum that maintains both brightness and letter discernability
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 light emitting device improves the discernability of letters or objects for individuals with reduced visual sensitivity to blue light by adjusting the light spectrum to resemble the blackbody radiation locus, enhancing visibility and color recognition.
Implementation Method 1
a light emitting element emitting light having a peak emission wavelength in a range of 440 nm to 470 nm
Implementation Method 2
a wavelength conversion member including multiple phosphors emitting light when excited by the light from the light emitting element
Data Source
AI summary
Provided is a light-emitting device capable of improving discernibility of letters or the like when used by a person with reduced visual sensitivity to blue light. The light-emitting device comprises a light-emitting element emitting light having an emission peak wavelength in a range of 440 nm to 470 nm, and a wavelength conversion member including a plurality of phosphors emitting light when excited by the light from the light emitting element. Ratios of luminous intensities of the light emitted from the light emitting device at wavelengths 480 nm, 530 nm, and 550 nm to the luminous intensity at the peak emission wavelength attributed to the light emitting element in an emission spectrum are 0.05 to 0.20, 0.20 to 0.35, and 0.23 to 0.38, respectively.