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[IEEE 2019 14th IEEE Conference on Industrial Electronics and Applications (ICIEA) - Xi'an, China (2019.6.19-2019.6.21)] 2019 14th IEEE Conference on Industrial Electronics and Applications (ICIEA) - Signature-Based Morse Code Encoding for a LED-Based optical Layer 2 data communication
摘要： With the rapid improvements in engineering technology, underwater communications have gained major interests from researchers with application areas from commercial to military water based communication systems. However, underwater wireless communication is challenging and difficult compared to wireless terrestrial as it can be easily interrupted due to interference from harsh underwater operation conditions, noise, limited bandwidth and power resources. Various researches in underwater acoustic, optical, and RF communications for secured and reliable underwater wireless network have been carried out. In this paper, an LED based optical wireless communications is proposed using a layered 2 Morse-code based encoding protocol for short distance underwater communication. The proposed system converts the data into a serial of dots and spaces before it is transmitted using the LED as a light source. At the receiver end, the system decodes sequences of on-off light sensed by the photo-diode into the data. The main contribution of this work is the design of a layer 2 signature-based encoding and decoding systems for short range wireless underwater optical communication protocol that can provide a higher data rates compared to traditional acoustic systems with significant lower power consumption and simpler computational complexity. The transmission protocol is evaluated in a dark room and in a water medium. The results have shown above 90% transmission success rate. The result also showed that different colors of the LED emission can affect the reliability of data transmission.
关键词： LED,Transmission Protocol,Optical Communication,Morse Code,Underwater Communication
更新于2025-09-11 14:15:04
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[IEEE 2019 Compound Semiconductor Week (CSW) - Nara, Japan (2019.5.19-2019.5.23)] 2019 Compound Semiconductor Week (CSW) - Superpower Transistor Consisting of Only LED and Silicon Solar Cell — Its Application to Electric Vehicle Drive Control
摘要： High-power IGBT, Insulated Gate Bipolar Transistor, is currently used for the motor control of EV i.e. Electric Vehicle. In 2012, Professor Okamoto, the first author of this paper, invented a novel power transistor, named power distar, consisting of only LED and Si solar cell. The performance of the new transistor was comparable to Si power transistor. Further very recently, he developed a superpower distar with an output as large as 50kW for EV, and at the onset he has succeeded in the motor control of an electric cart for the elderly. We would like to introduce our original superpower distar transistor and its application to EV drive control in the late news of this conference.
关键词： Si solar cell,LED,distar,EV
更新于2025-09-11 14:15:04
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White LEDs With High Optical Consistency Packaged Using 3D Ceramic Substrate
摘要： Packaging efficiency and optical performances are important indexes for white light-emitting diodes (WLEDs) packaging. In this letter, wafer-level WLEDs packaging were presented by printing phosphor on three-dimensional (3D) ceramic substrate to improve packaging efficiency and optical consistency. The 3D ceramic substrate was prepared by repeatedly electroplating copper cups on the planar direct plated copper (DPC) ceramic substrate. The phosphor concentration was adjusted to realize natural white light. The fabrication errors of the 3D ceramic substrate and the optical performances of WLED modules were analyzed to evaluate the optical consistency of the WLED modules packaged by using 3D ceramic substrate. Consequently, the fabrication errors of 3D ceramic substrate are less than 1%. When the phosphor concentration was set at 12.5 wt%, the packaged LEDs achieve a natural white light with luminous efficiency (LE) of 94.55 lm/W, correlated color temperature (CCT) of 5915 K, and chromaticity coordinate of (0.3166, 0.3345). The WLED modules exhibit small standard deviations in LE (1%), color rendering index (1%), correlated color temperature (98 K), and high reliability. The results indicate that the WLEDs packaged using 3D ceramic substrate have excellent optical consistency.
关键词： direct plated copper (DPC) ceramic substrate,optical performance,White light-emitting diodes (WLEDs),LED packaging,reliability
更新于2025-09-11 14:15:04
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Facile synthesis of the desired red phosphor Li <sub/>2</sub> Ca <sub/>2</sub> Mg <sub/>2</sub> Si <sub/>2</sub> N <sub/>6</sub> :Eu <sup>2+</sup> for high CRI white LEDs and plant growth LED device
摘要： The red emission with suitable peak wavelength and narrow band is acutely required for high color rendering index (CRI) white LEDs without at the cost of the luminous efficacy. Herein, the Li2Ca2Mg2Si2N6:Eu2+ red phosphor was prepared with facile solid-state method using Ca3N2, Mg3N2, Si3N4, Li3N, and Eu2O3 as the safety raw materials under atmospheric pressure for the first time, which shows red emission peaking at 638 nm with full width at half maximum (FWHM) of 62 nm under blue light irradiation and becomes the desired red phosphor to realize the balance between luminous efficacy and high CRI in white LEDs. The morphology, structure, luminescence properties, thermal quenching behavior, and chromaticity stability of the Li2Ca2Mg2Si2N6:Eu2+ phosphor are investigated in detail. Concentration quenching occurs when the Eu2+ content exceeds 1.0 mol%, whereas high temperature photoluminescent measurements show a 32% drop from the room temperature efficiency at 423 K. In view of the excellent luminescence performances of Li2Ca2Mg2Si2N6:Eu2+ phosphor, a white LEDs with CRI of 91 as a proof-of-concept experiment was fabricated by coating the title phosphor with Y3Al5O12:Ce3+ on a blue LED chip. In addition, the potential application of the title phosphor in plant growth LED device was also demonstrated. All the results indicate that Li2Ca2Mg2Si2N6:Eu2+ is a promising red-emitting phosphor for blue-LED-based high CRI white LEDs and plant growth lighting sources.
关键词： Li2Ca2Mg2Si2N6:Eu2+,high CRI white LEDs,plant growth LED device,phosphor
更新于2025-09-11 14:15:04
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Heteroepitaxial Growth of High-Quality and Crack-Free AlN Film on Sapphire Substrate with Nanometer-Scale-Thick AlN Nucleation Layer for AlGaN-Based Deep Ultraviolet Light-Emitting Diodes
摘要： High-quality and crack-free aluminum nitride (AlN) film on sapphire substrate is the foundation for high-efficiency aluminum gallium nitride (AlGaN)-based deep ultraviolet light-emitting diodes (DUV LEDs). We reported the growth of high-quality and crack-free AlN film on sapphire substrate with a nanometer-scale-thick AlN nucleation layer (NL). Three kinds of nanometer-scale-thick AlN NLs, including in situ low-temperature AlN (LT-AlN) NL, oxygen-undoped ex situ sputtered AlN NL, and oxygen-doped ex situ sputtered AlN NL, were prepared for epitaxial growth of AlN films on sapphire substrates. The influence of nanoscale AlN NL thickness on the optical transmittance, strain state, surface morphology, and threading dislocation (TD) density of the grown AlN film on sapphire substrate were carefully investigated. The average optical transmittance of AlN film on sapphire substrate with oxygen-doped sputtered AlN NL was higher than that of AlN films on sapphire substrates with LT-AlN NL and oxygen-undoped sputtered AlN NL in the 200–270 nm wavelength region. However, the AlN film on sapphire substrate with oxygen-undoped sputtered AlN NL had the lowest TD density among AlN films on sapphire substrates. The AlN film on sapphire substrate with the optimum thickness of sputtered AlN NL showed weak tensile stress, a crack-free surface, and low TD density. Furthermore, a 270-nm AlGaN-based DUV LED was grown on the high-quality and crack-free AlN film. We believe that our results offer a promising and practical route for obtaining high-quality and crack-free AlN film for DUV LED.
关键词： crystal quality,tensile stress,nucleation layer,surface morphology,DUV LED
更新于2025-09-11 14:15:04
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The static and dynamic analysis of GaN-based blue light-emitting diodes used in visible light communication
摘要： The static and dynamic electrical characteristics of GaN-based blue light-emitting diodes with different numbers of quantum wells were investigated by software Silvaco technology computer-aided design numerically, which were essential for visible light communication study. As a factor impacts on the response time of light-emitting diodes, the capacitance, varying with applied bias, with modulation frequency, and with the numbers of quantum wells, was analyzed detailedly. Besides that, the response time of light-emitting diodes, including the optical rise time and fall time, was also ?rstly simulated in Silvaco, and then, based on these, the pure - 3 dB bandwidth of the light-emitting diodes without building-out circuit could be calculated, so as to self-design semiconductor devices like light-emitting diodes mentioned in this study with the optimum bandwidth used for visible light communication.
关键词： Silvaco,Visible light communication,Response time,Bandwidth,GaN-based LED
更新于2025-09-11 14:15:04
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[IEEE 2019 Second Balkan Junior Conference on Lighting (Balkan Light Junior) - Plovdiv, Bulgaria (2019.9.19-2019.9.21)] 2019 Second Balkan Junior Conference on Lighting (Balkan Light Junior) - Investigating the Influence of Environmental and Design Parameters on the Thermal Regime of a LED Lamp
摘要： The increase of the LED’s temperature above a certain threshold decreases significantly their live expectancy. Therefore, it is important to investigate LEDs’ thermal regime during exploitation. The influence of the construction and the environment parameters on the thermal regime of LED lamp was investigated in this paper. The study was done with a specially developed software, based on a model, describing the thermal regime of LED lamps. Next, a methodology for the research has been developed and a simulation study was carried out. The results of this investigation are represented graphically.
关键词： simulation,model,LED lamp,investigation
更新于2025-09-11 14:15:04
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A comparison between a white LED confocal imaging system and a conventional flash fundus camera using chromaticity analysis
摘要： Background: Conventional flash fundus cameras capture color images that are oversaturated in the red channel and washed out in the green and blue channels, resulting in a retinal picture that often looks flat and reddish. A white LED confocal device was recently introduced to provide a high-quality retinal image with enhanced color fidelity. In this study, we aimed to evaluate the color rendering properties of the white LED confocal system and compare them to those of a conventional flash fundus camera through chromaticity analysis. Methods: A white LED confocal device (Eidon, Centervue, Padova, Italy) and a traditional flash fundus camera (TRC-NW8, Topcon Corporation, Tokyo, Japan) were used to capture fundus images. Color images were evaluated with respect to chromaticity. Analysis was performed according to the image color signature. The color signature of an image was defined as the distribution of its pixels in the rgb chromaticity space. The descriptors used for the analysis are the average and variability of the barycenter positions, the average of the variability and the number of unique colors (NUC) of all signatures. Results: Two hundred thirty-three color photographs were acquired with each retinal camera. The images acquired by the confocal white LED device demonstrated an average barycenter position (rgb = [0.448, 0.328, 0.224]) closer to the center of the chromaticity space, while the conventional fundus camera provides images with a clear shift toward red at the expense of the blue and green channels (rgb = [0.574, 0.278, 0.148] (p < 0.001). The variability of the barycenter positions was higher in the white LED confocal system than in the conventional fundus camera. The average variability of the distributions was higher (0.003 ± 0.007, p < 0.001) in the Eidon images compared to the Topcon camera, indicating a greater richness of color. The NUC percentage was higher for the white LED confocal device than for the conventional flash fundus camera (0.071% versus 0.025%, p < 0.001). Conclusions: Eidon provides more-balanced color images, with a wider richness of color content, compared to a conventional flash fundus camera. The overall higher chromaticity of Eidon may provide benefits in terms of discriminative power and diagnostic accuracy.
关键词： Conventional flash fundus camera,Chromaticity,Topcon,Eidon,Confocal white LED system
更新于2025-09-11 14:15:04
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Estimation on hazardous characteristics of the components from linear type of end-of-life light-emitting diode lamps
摘要： The supply of light-emitting diode (LED) lamps has been expanding as lighting devices to replace fluorescent lamps. Accordingly, it is expected that a large amount of end-of-life LED lamps will be generated. Among various types of LED lamps, liner LED lamps are generally used. Since linear LED lamps have been reported to use hazardous materials such as As and Pb, the hazardous characteristics of end-of-life LED lamps were estimated. To verify the hazardous characteristics of end-of-life linear LED lamps, leaching tests such as Korea Extraction Test (KET) and Toxicity Characteristics Leaching Procedure (TCLP) were carried out for the overall mixture and the each component of end-of-life linear LED lamps. The linear LED lamp is generally composed of cover, frame, LED, the driver and others. The portions of LED and the driver in linear LED lamp are only about 1% and 10%, respectively. End-of-life linear LED lamp can be non-hazardous waste because leaching concentrations of heavy metals in the overall mixture of end-of-life linear LED lamp were lower than the regulatory level. Since leaching concentrations of As, Pb and Cu in LED and the driver were higher than the regulatory level, however, LED and the driver can be classified as the hazardous waste.
关键词： Hazardous characteristic,LED,Toxicity characteristics leaching procedure (TCLP),Korea extraction test (KET)
更新于2025-09-11 14:15:04
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Best practices for measuring emerging light-emitting diode technologies
摘要： The arrival of light-emitting diodes based on new materials is posing challenges for the characterization and comparison of devices in a trusted and consistent manner. Here we provide some advice and guidelines that we hope will benefit the community.
关键词： LED characterization,emerging technologies,performance metrics,standardization,light-emitting diodes
更新于2025-09-11 14:15:04