Semiconductor Light Emitting Device with Localized Wavelength Conversion
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Solution Overview
Problem
Semiconductor light emitting devices face challenges in achieving uniform brightness and color distribution due to non-uniform current density and emission wavelength distributions, leading to color unevenness in mixed light, especially in applications like vehicle lamps where high brightness and specific chromaticity are required.
Innovation Solution
A semiconductor light emitting device with a wavelength converting layer that has different wavelength conversion characteristics at areas of high and low current density, ensuring uniform emission color by adjusting the thickness and concentration of the fluorescent substance accordingly, and an optical system that projects light to form a desired distribution pattern without color unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a uniform wavelength converting layer is formed on the light emitting element, then the manufacturing process is simple, but color unevenness occurs due to non-uniform current density distribution
Solution Approach 1:
The patent applies local quality by forming a wavelength converting layer with spatially varying thickness or fluorescent substance concentration that corresponds to the non-uniform current density distribution of the light emitting element. The layer has different conversion characteristics in different regions to compensate for the non-uniformity in light emission, thereby achieving uniform emission color across the entire surface.
2Manufacturing precision
If the current density distribution is made uniform, then the emission color becomes uniform, but the brightness distribution becomes non-uniform which is undesirable for vehicle lamps
Solution Approach 1:
The patent maintains the non-uniform brightness distribution desired for vehicle lamp applications while achieving uniform emission color by implementing local variations in the wavelength converting layer. The layer's thickness or fluorescent substance concentration is adjusted in different regions to compensate for non-uniform current density, allowing the brightness profile to remain optimized for vehicle lighting while the color remains uniform.
3Power
If the wavelength converting layer thickness is increased, then more light is converted, but color unevenness increases due to non-uniform current density
Solution Approach 1:
The patent achieves both high light conversion efficiency and uniform emission color by implementing a wavelength converting layer with non-uniform thickness or fluorescent substance concentration. The local properties of the layer are optimized in different regions to match the current density distribution, ensuring that each region converts light efficiently while maintaining uniform overall color output.
4Ease of manufacture
If a uniform fluorescent substance concentration is used, then the manufacturing process is simple, but the mixing ratio of blue and yellow light becomes non-uniform
Solution Approach 1:
The patent addresses the non-uniform mixing ratio of blue and yellow light by implementing a wavelength converting layer with spatially varying fluorescent substance concentration. The concentration is adjusted in different regions to compensate for non-uniform current density distribution, achieving uniform light mixing ratio and emission color while maintaining practical manufacturability.
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 effectively suppresses color unevenness and achieves uniform emission color, enhancing the light distribution pattern in vehicle lamps while maximizing light use efficiency by minimizing light cutoff, thus making the semiconductor light emitting device suitable for vehicle lamp applications.
Implementation Method 1
a fluorescent substance that absorbs part of light from the light emitting element to emit light having a wavelength longer than that of the light from the light emitting element
Data Source
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AI summary
A semiconductor light emitting device which produces mixed light of a desired emission color by a combination of a semiconductor light emitting element and a wavelength converting layer containing a fluorescent substance, and a vehicle lamp including the semiconductor light emitting device. The wavelength converting layer has different wavelength conversion characteristics respectively at its portion covering an area of relatively high current density at light emission operation of the semiconductor light emitting element and at its portion covering an area of relatively low current density so as to reduce chromaticity difference over the light extraction surface of the mixed light due to non-uniformity of current density in the light emitting layer at light emission operation.