• Title, Summary, Keyword: LED arrays

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A Color-Filterless LCD with RGB LED and Lenticular-Lens Arrays

  • Kwon, Jin-Hyuk
    • Journal of Information Display
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    • v.11 no.2
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    • pp.45-48
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    • 2010
  • A direct-lit liquid crystal display that does not use color filters is proposed. A backlight unit that employs compartmentalized RGB LED and lenticular-lens arrays is used instead of color filters to direct the RGB LED lights into the RGB subpixels. The color-filterless LED backlight design, simulation, and experiment results are presented.

A Study on the optical logic gate using LED array (LED 배열을 이용한 광논리 게이트에 관한 연구)

  • 권원현;박한규
    • Proceedings of the Korean Institute of Communication Sciences Conference
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    • pp.25-27
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    • 1984
  • Using LED sources, the system that performs optical logic function of the input data arrays will be presented. Sixteen possible functions of two binary data arrays, such as AND, OR, NOR and XOR are simply obtained in parallel by controlling LED switching mode. Experimental result and some examples of application will be given.

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Adaptive planar vision marker composed of LED arrays for sensing under low visibility

  • Kim, Kyukwang;Hyun, Jieum;Myung, Hyun
    • Advances in robotics research
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    • v.2 no.2
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    • pp.141-149
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    • 2018
  • In image processing and robotic applications, two-dimensional (2D) black and white patterned planar markers are widely used. However, these markers are not detectable in low visibility environment and they are not changeable. This research proposes an active and adaptive marker node, which displays 2D marker patterns using light emitting diode (LED) arrays for easier recognition in the foggy or turbid underwater environments. Because each node is made to blink at a different frequency, active LED marker nodes were distinguishable from each other from a long distance without increasing the size of the marker. We expect that the proposed system can be used in various harsh conditions where the conventional marker systems are not applicable because of low visibility issues. The proposed system is still compatible with the conventional marker as the displayed patterns are identical.

A Color-Filterless LCD by using RGB LED array and lenticular lens array

  • Kwon, Jin-Hyuk
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.76-78
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    • 2009
  • A liquid crystal display that does not use color filters is proposed. A backlight unit that employs compartmentalized RGB LED arrays and a lenticular lens array is used instead of the color filters in order to direct RGB LED lights into the RGB subpixels. A design of color-filterless LED backlight and experimental results are presented.

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Improved Light Output of GaN-Based Light-Emitting Diodes with ZnO Nanorod Arrays (ZnO 나노로드 배열에 의한 GaN기반 광다이오드의 광추출율 향상)

  • Lee, Sam-Dong;Kim, Kyoung-Kook;Park, Jae-Chul;Kim, Sang-Woo
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.59-60
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    • 2008
  • GaN-based light-emitting diodes (LEDs) with ZnO nanorod arrays on a planar indium tin oxide (ITO) transparent electrode were demonstrated. ZnO nanorods were grown into aqueous solution at low temperature of $90^{\circ}C$. Under 20 mA current injection, the light output efficiency of the LED with ZnO nanorod arrays on ITO was remarkably increased by about 40 % of magnitude compared to the conventional LED with only planar ITO. The enhancement of light output by the ZnO nanorod arrays is due to the formation of side walls and a rough surface resulting in multiple photon scattering at the LED surface.

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Variable-color Light-emitting Diodes Using GaN Microdonut Arrays

  • Tchoe, Youngbin;Jo, Janghyun;Kim, Miyoung;Heo, Jaehyuk;Yoo, Geonwook;Sone, Cheolsoo;Yi, Gyu-Chul
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.280-280
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    • 2014
  • We report the fabrication and electroluminescent characteristics of GaN/InxGa1-xN microdonut-shaped light-emitting diode (LED) microarrays as variable-color emitters. The diameter, width, height, and period of the GaN microdonuts were controlled by their growth parameters and the geometrical factors of the growth mask patterns. For the fabrication of microdonut LEDs, p-GaN/p-AlxGa1-xN/u-GaN/u-InxGa1-xN heteroepitaxial layers were coated on the entire surface of n-GaN microdonuts. The microdonut LED arrays showed strong light emission, which could be seen with the unaided eye under normal room illumination. Additionally, magnified optical images of microdonut LED arrays exhibited microdonut-shaped light emissions having spatially resolved blue and green colors. Their electroluminescence spectra had two dominant peaks at 460 and 560 nm. With increasing applied voltage, the intensity of the blue emission peak increased much faster than that of the green emission peak, indicating that the color of the LEDs is tunable. We also demonstrated that EL spectra of the devices could be controlled by changing the size of microdonut LEDs. What we want to emphasize here with the microdonut LEDs is that they have additional inner sidewall facets which did not exist for other typical three-dimensional structures including nanopyramids and nanorods, and that InxGa1-xN single quantum well formed on the inner sidewall facets had unique thickness and chemical composition, which generated additional EL color. The origin of the electroluminescence peaks was investigated by structural characterizations and chemical analyses.

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Thermal Analysis and Design of AlGaInP-based Light Emitting Diode Arrays

  • Ban, Zhang;Liang, Zhongzhu;Liang, Jingqiu;Wang, Weibiao;JinguangLv, JinguangLv;Qin, Yuxin
    • Current Optics and Photonics
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    • v.1 no.2
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    • pp.143-149
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    • 2017
  • LED arrays with pixel numbers of $3{\times}3$, $4{\times}4$, and $5{\times}5$ have been studied in this paper in order to enhance the optical output power and decrease heat dissipation of an AlGaInP-based light emitting diode display device (pixel size of $280{\times}280{\mu}m$) fabricated by micro-opto-electro-mechanical systems. Simulation results showed that the thermal resistances of the $3{\times}3$, $4{\times}4$, $5{\times}5$ arrays were $52^{\circ}C/W$, $69.7^{\circ}C/W$, and $84.3^{\circ}C/W$. The junction temperature was calculated by the peak wavelength shift method, which showed that the maximum value appears at the center pixel due to thermal crosstalk from neighboring pixels. The central temperature would be minimized with $40{\mu}m$ pixel pitch and $150{\mu}m$ substrate thickness as calculated by thermal modeling using finite element analysis. The modeling can be used to optimize parameters of highly integrated AlGaInP-based LED arrays fabricated by micro-opto-electro-mechanical systems technology.

The Variation of Sapphire Substrate Shape of Micro LED Array to Increasing of Light Intensity and Contrast Ratio (Light Intensity 및 명암비 향상을 위한 마이크로 LED의 사파이어 기판 형상 변화 연구)

  • Cha, Yu-Jung;Kwak, Joon Seop
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.34 no.1
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    • pp.8-15
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    • 2021
  • Micro-LEDs can be applied to various parts of a product. However, it has disadvantages compared to general LEDs in large displays such as low efficiency, intensity, and contrast ratio, among others, owing to their short history of study. The simulations were carried out using ray-tracing software to investigate the change in light intensity and light distribution according to pattern shapes on the sapphire substrate of the flip-chip micro-LED (FC μ-LED) array. Three patterns-concave square patterns, convex square patterns, and Ag coated convex patterns-which existed on the opposite side of FC μ-LEDs (115 ㎛ × 115 ㎛) array, were applied. The intensity of FC μ-LEDs on the center of the receivers depends on the pattern depth with shape. The concave square patterns having FC μ-LEDs arrays show that decreasing intensity as the patterns depth. On the contrary, the convex square patterns having FC μ-LEDs arrays shows that increasing intensity as the patterns depth. In addition, the highest intensity shows that FC μ-LEDs having Ag-coated convex patterns on the opposite side of sapphire lead to a reduction in light crosstalk owing to the Ag film.

Thermal Transient Characteristics of Die Attach in High Power LED Package

  • Kim Hyun-Ho;Choi Sang-Hyun;Shin Sang-Hyun;Lee Young-Gi;Choi Seok-Moon;Oh Yong-Soo
    • Journal of the Microelectronics and Packaging Society
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    • v.12 no.4
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    • pp.331-338
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    • 2005
  • The rapid advances in high power light sources and arrays as encountered in incandescent lamps have induced dramatic increases in die heat flux and power consumption at all levels of high power LED packaging. The lifetime of such devices and device arrays is determined by their temperature and thermal transients controlled by the powering and cooling, because they are usually operated under rough environmental conditions. The reliability of packaged electronics strongly depends on the die attach quality, because any void or a small delamination may cause instant temperature increase in the die, leading sooner or later to failure in the operation. Die attach materials have a key role in the thermal management of high power LED packages by providing the low thermal resistance between the heat generating LED chips and the heat dissipating heat slug. In this paper, thermal transient characteristics of die attach in high power LED package have been studied based on the thermal transient analysis using the evaluation of the structure function of the heat flow path. With high power LED packages fabricated by die attach materials such as Ag paste, solder paste and Au/Sn eutectic bonding, we have demonstrated characteristics such as cross-section analysis, shear test and visual inspection after shear test of die attach and how to detect die attach failures and to measure thermal resistance values of die attach in high power LED package. From the structure function oi the thermal transient characteristics, we could know the result that die attach quality of Au/Sn eutectic bonding presented the thermal resistance of about 3.5K/W. It was much better than those of Ag paste and solder paste presented the thermal resistance of about 11.5${\~}$14.2K/W and 4.4${\~}$4.6K/W, respectively.

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The Creation of a Strong Magnetic Field by Means of Large Magnetic Blocks from NdFeB Magnets in Opposing Linear Halbach Arrays

  • Zezulka, Vaclav;Straka, Pavel
    • Journal of Magnetics
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    • v.21 no.3
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    • pp.364-373
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    • 2016
  • The article presents the results and findings obtained through the assembly of opposing linear Halbach arrays from two magnet layers using large magnetic blocks from permanent NdFeB magnets, especially concerning the distribution of magnetic induction in an air gap. The use of these large blocks has led to a significant expansion of the area of magnetic field with a substantially higher value of magnetic induction in comparison with similar linear Halbach arrays composed of small magnets. The paper also discusses the determined dependences of magnetic induction on the parameters of the x, y, z coordinate system and indicates the possibilities of achieving an even stronger magnetic field in a larger volume of an air gap for application for instance in equipment for magnetic separation of raw materials, in instrument technologies and in other areas.