White Light Source Spectral Smoothing via Phosphor Ratios
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Solution Overview
Problem
Conventional white light sources with LEDs exhibit irregularities in their light emission spectra, leading to differences in color tone perception when objects are illuminated compared to sunlight, due to numerous bumps and dips in their spectral distributions.
Innovation Solution
A white light source with a light emitting diode having a peak wavelength between 350 and 490 nm and phosphors that emit visible light, where the ratio of local minimum to local maximum intensity values in the spectrum is 0.5 or more, reducing spectral irregularities and making color tones appear similar to those under sunlight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional white LEDs combine blue LEDs with YAG phosphors to achieve white light, then energy saving and long service life are improved, but spectral irregularities cause color tone perception differences compared to sunlight
Solution Approach 1:
The patent applies parameter changes by carefully selecting and adjusting the peak wavelengths of multiple phosphors (blue: 440-480nm, cyan: 470-500nm, green: 500-540nm, yellow: 560-580nm, red: 600-650nm) to smooth the spectral distribution. By changing the wavelength parameters and intensity ratios of each phosphor component, the overall spectrum achieves better alignment with sunlight while maintaining LED energy efficiency.
Solution Approach 2:
The patent uses composite materials by combining multiple phosphor types with different emission characteristics. Instead of a single phosphor material, it employs a composite phosphor system including blue phosphor (e.g., BaMgAl10O17:Eu3+), cyan phosphor (e.g., Sr2Si5N8:Eu2+), green phosphor (e.g., SrSi2O2N2:Eu2+), yellow phosphor (e.g., YAG:Ce3+), and red phosphor (e.g., CaAlSiN3:Eu2+), creating a composite luminescent material system that produces a balanced spectrum.
2Illumination intensity
If blue LED peak intensity is 1.5 times or more the yellow phosphor peak intensity, then white light is achieved, but strong blue light influence causes spectral irregularities
Solution Approach 1:
The patent applies parameter changes by adjusting the intensity ratio parameter between blue LED and yellow phosphor from the conventional 1.5:1 or higher to a more balanced ratio. It also introduces additional phosphors with peak wavelengths between 470-540nm to fill the spectral gaps, changing the overall spectral composition parameters to achieve a more uniform distribution.
Solution Approach 2:
The patent introduces intermediary phosphors (cyan and green phosphors with peak wavelengths of 470-500nm and 500-540nm respectively) that act as mediators between the blue LED emission and the yellow phosphor emission. These intermediary phosphors fill the spectral gaps and smooth the transitions, reducing the harshness of the blue light influence while maintaining overall white light output.
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 reduces spectral irregularities, ensuring that color tones of objects are perceived similarly to those under natural sunlight, reducing eye strain and discomfort, and is suitable for various illumination tasks.
Implementation Method 1
a light emitting diode having a light emission peak wavelength equal to or greater than 350 nm and less than or equal to 490 nm
Implementation Method 2
a phosphor that emits visible light upon excitation by a light emitted from the light emitting diode
Data Source
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AI summary
The present invention provides a white light source comprising a light emitting diode having a light emission peak wavelength of 350 to 490 nm and a phosphor that emits visible light upon excitation by a light emitted from the light emitting diode; wherein, with respect to an arbitrary local maximum value of light-emission intensity between 350 and 780 nm of a light emission spectrum of the white light source, a ratio of a local minimum value of light-emission intensity that is closest on a long wavelength side to the local maximum value is such that, when the local maximum value is taken as 1, the local minimum value is 0.5 or more. It is preferable that, with respect to an arbitrary local maximum value of light-emission intensity between 350 and 780 nm of a light emission spectrum of the white light source, a ratio of a local minimum value of light-emission intensity that is closest on a long wavelength side to the local maximum value is such that, when the local maximum value is taken as 1, the local minimum value is 0.7 or more. According to the above structure, there can be provided a white light source capable of preventing a specified wavelength region from protruding in the light emission spectrum, and capable of visually perceiving the color tone of the irradiation object as the same state where the object is irradiated with sunlight.