Equivalent Brightness Fitting Calculation Method about White LEDs

2011 ◽  
Vol 121-126 ◽  
pp. 2721-2725
Author(s):  
Yong Yang ◽  
Lei Wang ◽  
Chuan Zheng Zhu
Keyword(s):  
Relative Strength ◽  
Luminous Efficiency ◽  
Color Temperature ◽  
Light Sources ◽  
White Led ◽  
Excellent Correlation ◽  
Efficiency Function ◽  
White Leds ◽  
Mesopic Vision ◽  
Brightness Curve

White LEDs can show different correlated color temperature (abbreviated as CCT) by adjusting the luminous spectrum peak distribution and relative strength. Recent research results indicate that spectral luminous efficiency function of mesopic vision Vmes(λ) and equivalent brightness are associated with luminous spectra of light sources. A series of white LEDs with different CCT are tested and calculated, it shows white LED with higher CCT has higher mesopic vision equivalent brightness, although the brightness are identical when the tester corrected by traditional photopic vision spectral luminous efficiency V(λ). From the equivalent brightness curve fitting, the curve can be described as a polynomial function, for it excellent correlation, the more value of equivalent brightness could be calculated without complex derivation.

Properties of Light Sources under Mesopic Vision

2011 ◽  
Vol 308-310 ◽  
pp. 228-231
Author(s):  
Yong Yang ◽  
Lei Wang ◽  
Wei Li
Keyword(s):  
Visual Perception ◽  
Luminous Efficiency ◽  
Light Sources ◽  
Human Visual Perception ◽  
Efficiency Function ◽  
White Leds ◽  
Mesopic Vision ◽  
Vision Condition ◽  
Background Brightness

The mesopic vision theory is used to study illumination properties of series of light sources, through the test of luminous spectrum and derivation based on the MOVE model, the results show that spectral luminous efficiency function Vmes(λ) is between traditional V(λ) and V′(λ) when the background brightness under mesopic vision condition, and the function of Vmes(λ) is changed with the different of light sources and background brightness. Based on human visual perception, the mesopic vision equivalent brightness can be calculated, which of HPS is lower than test brightness corrected by V(λ), but white LEDs and FL show opposite phenomena, and the different value between mesopic and photopic brightness presents reduce trend with rising of background brightness.

Green Innovation Design Based on TRIZ Theory

2011 ◽  
Vol 308-310 ◽  
pp. 373-379 ◽  
Author(s):  
Zhi Feng Liu ◽  
Yang Gao ◽  
Lei Zhang ◽  
Di Hu
Keyword(s):  
Visual Perception ◽  
Luminous Efficiency ◽  
Light Sources ◽  
Green Innovation ◽  
Human Visual Perception ◽  
Efficiency Function ◽  
White Leds ◽  
Mesopic Vision ◽  
Vision Condition ◽  
Background Brightness

The mesopic vision theory is used to study illumination properties of series of light sources, through the test of luminous spectrum and derivation based on the MOVE model, the results show that spectral luminous efficiency function Vmes(λ) is between traditional V(λ) and V′(λ) when the background brightness under mesopic vision condition, and the function of Vmes(λ) is changed with the different of light sources and background brightness. Based on human visual perception, the mesopic vision equivalent brightness can be calculated, which of HPS is lower than test brightness corrected by V(λ), but white LEDs and FL show opposite phenomena, and the different value between mesopic and photopic brightness presents reduce trend with rising of background brightness.

Study on the Highway Tunnel Lighting with Spectrum Superposition

2012 ◽  
Vol 512-515 ◽  
pp. 2713-2717
Author(s):  
Yong Yang ◽  
Wen Yuan Han ◽  
Lei Wang
Keyword(s):  
Luminous Efficiency ◽  
Light Sources ◽  
White Led ◽  
Peak Wavelength ◽  
Mesopic Vision ◽  
Photopic Vision ◽  
Highway Tunnel ◽  
Vision Condition ◽  
The Difference

The lighting level of highway tunnel is usually under mesopic vision condition, but the traditional luminance and illuminance test are corrected by photopic vision spectral luminous efficiency. According to the difference of spectral luminous efficiency between photopic and mesopic, the lighting with different peak wavelength would provide various ratios of radiation / photometric flux. Four kinds of narrowband light sources with the same tested flux were stacked up in white LED and HPS respectively, through equivalent brightness calculation, the most efficient spectral wavelength were obtained under mesopic condition.

Highway Tunnel Lighting Research Based on Mesopic Vision

2011 ◽  
Vol 71-78 ◽  
pp. 4061-4064
Author(s):  
Yong Yang ◽  
Chuan Zheng Zhu ◽  
Lei Wang
Keyword(s):  
Reaction Time ◽  
Design Method ◽  
B Value ◽  
Light Sources ◽  
White Led ◽  
Mesopic Vision ◽  
Highway Tunnel ◽  
Function Fitting ◽  
Sodium Lamp ◽  
High Pressure Sodium Lamp

The white LED and high-pressure sodium lamp (HPS) are used to simulate highway tunnel lighting under different background brightness (abbreviated as B) conditions, from a series of reaction time tests, the result shows that white LED can provide shorter reaction time for observers compared with HPS, further research suggests under the mesopic vision, different kinds of light sources maybe have unlike brightness, although which is identical under the photopic vision. From the luminous spectrum test and mesopic vision spectral luminous efficiency function fitting calculation, the mesopic equivalent brightness can be determined with certain light source and B value. This conclusion would provide a more accurate and lower energy consumption lighting design method for highway tunnel.

scholarly journals Simultaneously Improve White LED Omni-Directional Package Efficacy and Spatial Color Uniformity on Scattered Photon Extraction Technology

Crystals ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 21 ◽  
Author(s):  
Tsung-Xian Lee ◽  
Yun-Chieh Huang
Keyword(s):  
Extraction Efficiency ◽  
Critical Index ◽  
Light Extraction Efficiency ◽  
Color Temperature ◽  
Scattered Photon ◽  
Lens Design ◽  
White Led ◽  
Extraction Technology ◽  
White Leds ◽  
Color Uniformity

The Scattered Photon Extraction (SPE™) based on the concept of TIR lens combined with remote phosphor is proven to be one of the effective solutions for improving white LED efficiency, and it provides the omnidirectional light distribution for luminaire design. Not only the light extraction efficiency (LEE) is important, but also the angular uniformity of correlated color temperature (CCT) is a critical index in the evaluation of high-quality white LEDs. A non-optimized SPE™ will cause an increase in the angular CCT deviation (ACCTD) and ultimately affect lighting quality. Two possible ways using lens design are proposed to reduce the ACCTD and even improve its efficiency. Among them, using the concept of light guiding to design the lens can minimum the deviation of forward and backward CCT from 2720 K to 657 K, and the overall efficiency can be further enhanced by 12% compared to typical SPE™ lens.

scholarly journals High Luminescence White LEDs Prepared with 2D Island-Pattern of Quantum Dots Dispersed Photopolymer Films

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Hyun-Guk Hong ◽  
Min-Ho Shin ◽  
Hyo-Jun Kim ◽  
Jinsoo Shin ◽  
Young-Joo Kim
Keyword(s):  
Quantum Dots ◽  
Simulation Analysis ◽  
Critical Issue ◽  
Film Structure ◽  
Luminous Efficiency ◽  
Optical Path ◽  
White Led ◽  
Optical Efficiency ◽  
White Leds ◽  
Phosphor Film

Since the reabsorption loss among different size quantum dots (QDs) is a critical issue in the QD based white LEDs, we proposed and fabricated new film structure of 2D island-patterns consisting of separate green and red QDs dispersed photopolymer patterns in a zigzag form. A small air-gap such as 60 μm between QD islands helps to control the optical path at the interface to reduce the lateral reabsorption loss to enhance the optical efficiency of white LED. The 2D island-patterns of QD phosphor film were fabricated using a UV imprinting process and compared the optical efficiency with the other QD film structure prepared with same QD concentrations and thicknesses such as a mixed and separately layered QD structure. Experimental and simulation analysis were performed to confirm the better optical efficiency from the 2D island-patterns of QD films due to the reduced reabsorption loss. High luminescence white LED was finally realized with 2D island-patterns of QD film, resulting in a luminous efficiency of 62.2 lm/W and CRI of 83 with CCT of 4537 K at the operation current of 60 mA.

Road Luminaire’ Mesoptic Luminous Efficiency Analysis

2011 ◽  
Vol 71-78 ◽  
pp. 4918-4922
Author(s):  
Ke Huang ◽  
Ji Weng ◽  
Ying Kui Hu
Keyword(s):  
Luminance Level ◽  
Efficiency Analysis ◽  
Luminous Efficiency ◽  
Light Sources ◽  
Efficiency Function ◽  
Photopic Vision

Four kinds of traffic lighting sources HPS, MH, LED and EDL are widely used in roads and tunnels, the luminance at this place almost in the range of 1-10 cd/m2, which is the mesoptic vision. The mesoptic luminous efficiency can be calculated from photopic vision spectral luminous efficiency function. The results indicate that HPS’s luminous efficiency increased with improve of adaptation brightness, while the rest three kinds of light sources’ luminous efficiency reduced. At the same luminance level, HPS, MH, LED and EDL’s mesoptic luminous efficiency reduced in turn.

scholarly journals The Effects of TiO2 Diffuser-Loaded Encapsulation on Corrected Color Temperature Uniformity of Remote Phosphor White LEDs

2019 ◽  
Vol 9 (4) ◽  
pp. 675 ◽  
Author(s):  
Yung-Fang Chou ◽  
Chi-Feng Chen ◽  
Shang-Ping Ying ◽  
Yun-Ying Yeh
Keyword(s):  
Energy Efficient ◽  
High Efficiency ◽  
Luminous Flux ◽  
Color Temperature ◽  
White Led ◽  
Phosphor Layer ◽  
White Leds ◽  
Color Uniformity ◽  
Remote Phosphor ◽  
The Mean

With the development of high-efficiency and high-power LEDs, they have become the most energy-efficient and environmentally friendly artificial light source. Phosphor-converted white LEDs are currently mainstream in the market. The remote phosphor is an effective way to enhance the conversion efficiency and lifetime of phosphor-converted LEDs. For applications of high-quality lighting and LCD backlights, the uniformity of angular correlated color temperature (CCT) is very important. This report explored a remote phosphor white LED with low angular CCT variance and high luminous efficiency by using TiO2 diffuser-loaded encapsulation. Experimental results revealed that for the TiO2 diffuser-loaded encapsulation remote phosphor white LED, the angular color uniformity could be improved by 31.82% and the luminous flux by 8.65%. Moreover, the mean CCTs of the TiO2 diffuser-loaded encapsulation and non-diffuser remote phosphor white LEDs were similar at a driving current of 350 mA. Finally, we showed that incorporating the TiO2 diffuser into the phosphor layer of the remote phosphor white LEDs, does not influence the reliability of the LED.

Effects of Sintering Route and Flux on the Luminescence and Morphology of YAG: Ce Phosphors for White Emitting-Light Diodes (LEDs)

2012 ◽  
Vol 236-237 ◽  
pp. 9-15
Author(s):  
Tao Han ◽  
Shi Xiu Cao ◽  
Ming Xing Ma ◽  
Da Chuan Zhu ◽  
Cong Zhao ◽  
...  
Keyword(s):  
White Light ◽  
Potential Application ◽  
Color Temperature ◽  
Precipitation Method ◽  
Photoluminescence Intensity ◽  
White Led ◽  
White Leds ◽  
Chromaticity Coordinates ◽  
Co Precipitation ◽  
Surface Morphologies

YAG:Ce phosphors were synthesized by co-precipitation method. The photoluminescence intensity of samples sintered by the two-step route increases by about 10%, and with 0.5 wt.% NH4Cl added as flux, surface morphologies and size distribution are improved. The white LEDs were fabricated using as-obtained phosphors. It shows natural white light with chromaticity coordinates of (0.3083, 0.3163), color temperature (Tc) of 6886 K, the average CRI of 75, and the luminous efficacy of 85 ml/W. Therefore, The as-obtained YAG:Ce phosphors could be regard to have potential application in white LED devices.

Packaging of Phosphor Based High Power White LEDs: Effects of Phosphor Concentration and Packaging Configuration

2011 ◽  
Vol 133 (1) ◽  
Author(s):  
Yuan-Chang Lin ◽  
Jiun Pyng You ◽  
Nguyen T. Tran ◽  
Yongzhi He ◽  
Frank G. Shi
Keyword(s):  
Optical Power ◽  
Luminous Efficiency ◽  
Color Temperature ◽  
Light Emitting ◽  
White Leds ◽  
Chromaticity Coordinate ◽  
Air Interface ◽  
Output Only ◽  
White Light Emitting Diodes ◽  
Color Rendering

Two types of packaged white light emitting diodes in which one has a flat-top (FT) emitting surface and the other is a flat-top-with-lens (FTWL) type are fabricated by using the same leadframe and investigated on their optical properties, such as optical power, luminous efficiency, correlated color temperature (CCT), chromaticity coordinate, and color-rendering index (CRI), as a function of phosphor concentration in silicone encapsulant. It is found out that the optical power, CRI, and CCT decrease steadily as the phosphor ratio increases, while the luminous efficiency increases up to a level and then drops after a certain value of the phosphor ratio for both types of packages. Due to the totally internal reflection (TIR) at the encapsulant-air interface, the FT package shows a 10∼11% power (in mW) reduction compared with the FTWL package at the same phosphor concentration. However, it is demonstrated that the FT package provides a more efficient way of utilizing phosphor than the FTWL package based on the same targeted chromaticity coordinates due to the TIR effect inside, resulting in a reduced phosphor usage with a lumen output only about 3% lower than that of the FTWL package.

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