• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.221-221
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• 2013

Vertical LED (VLED) has been recognized as a way to obtain the high-power LED due to their advantages [1]. However, approximately 4% of the light generated from the active region is extracted, if the light extraction from side walls and back side is neglected because of Fresnel reflection (FR) and total internal reflection (TIR) [2,3]. In this study, the optical simulation of the VLED with the various microstructures was performed. Among them, the microlens having the diameter of 3 ${\mu}m$ and the height of 1.5 ${\mu}m$ shown the best result was chosen, and then, optimized microlens was formed on a GaN template using conventional semiconductor process. Various microstructures were proposed to improve the light extraction efficiency (LEE) of the VLED for the simulation. The LEE was simulated using LightTools based on a Monte Carlo ray tracing. The microstructures with hemisphere, cone, truncated and cylinder pattern having diameter of 3 ${\mu}m$ were employed on the top layer of the VLED respectively. The improvement of the LEE by using the microstructure is 87% for the hemisphere, 77% for the cone, 53% for the truncated, 21% for the cylinder, compared with the LEE of the flat surface at the reflectance of 85%. The LEE was increased by 88% at the height of 1.5 ${\mu}m$, compared with the LEE of the flat surface. We found that the microlens on the top layer is the most suitable for increasing the LEE. In order to apply the proposed microlens on n-GaN surface, we fabricated microlens on a GaN template. A photoresist array having hexagonal-closed packed microlens was fabricated on the GaN template. Then, optimization of etching the GaN template was performed using a dry etching process with ICP-RIE. The dry etching carried out using a gas mixture of Cl2 and Ar, each having a flow rate of 16 sccm and 10 sccm, respectively with RF power of 50 W, ICP power of 900 W and chamber pressure of 2 mTorr was the optimum etching condition as shown in Fig. 2(a).

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.5
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• pp.494-500
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• 2010

In this paper, we newly propose a wireless optical identification system and carried out experiments. A wireless optical identification system consists of a reader and a transponder. The configuration of a reader is the same as that of a transponder, which uses LED light as transmission media and detects the signal light with a solar cell. Optical alignment with a lens is not required because the absorption area of a solar cell is wide and flat, and it is very easy to attach a solar cell on the surface of an object. As the light wavelength does not interfere with radio frequency, a wireless optical identification system shows stable operation. In experiments, we realized a wireless optical identification system that automatically identifies the transponder data at a distance of 1 m using solar cells.

• Proceedings of the IEEK Conference
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• 2002.07c
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• pp.1398-1400
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• 2002

A new PLF-BLU (Plastic Light Fiber-Back Light Unit) using side glowing light fiber rods array for the 42" LCD TV display has been evelopedd. The light fibers were 14mm in diameter and 50cm long pure transparent acrylic rods of 1.49 refractive index. Fine seratees were made on the flat side of rod. extremely bright incandscent light from lamp fed into the fiber si scattered at scratches then emerges through the surface of rod. A typical PLF-BLU system consists of 24 PLFs produced side glow of brightness of 4,500cd/㎡ to 6,500cd/㎡. New PLF-BLU is proved to be a BLU of rigid, bright, no heat generation, and low power consumption, hence a prospective BLU system for very and/or ultra large size TVs. A new LED-PLF-BLU system considered to be a revolutionary to break-through of the BLU technologies has also been developed, and is decribed briefly.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2007.05a
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• pp.166-169
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• 2007

최근에 정부의 "15/30 LED조명 보급정책"에 힘입어 개발된 8W급 조명용 LED광원의 CIE 색도좌표 (chromaticity coordinate)와 주파장(dominant wavelength)등을 측정 고찰 하였다. 적색(R), 녹색(G), 청색(B), 백색(W)순으로 주파장은 각각 620[nm], 531[nm], 465[nm], 579[nm]이고, 자극순도(excitation purity)는 0.98, 0.82, 0.97, 0.15이며, 휘도순도(colorimetric putity)는 45[%], 16[%], 279[%], 6[%]로 나타났다. Power LED의 최적배치 설계로서, 특히 백색 LED광원의 경우 백열전구(15 lm/W)에 비해 3배 이상의 높은 효율(47.71m/W)을 보였고, 배광측정에서는 78.7%의 효율로 나타났다. 현재 LED광원은 MR16이나 베이스 타입 등의 형태로 제작하여 스탠드, 복도등, 비상유도등, 침실용 등의 용도에 사용되고, 일부는 LED의 원형이나 면(flat)타입으로 가로등이나 투광등으로도 활용되고 있다. 따라서 이들에 대한 각각의 특성들을 제시해 둘 필요성인 인지되어 국내 최초로 개발된 R/G/B/W 8W급 LED광원에 대한 기본적인 광특성 결과를 얻었으며, 이중에서 HB 백색 LED램프의 색도좌표 값을 얻어 CIE표준광과의 색도좌표(x, y) 위치를 비교 검토할 수 가 있었다.

• Journal of Digital Convergence
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• v.14 no.4
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• pp.419-424
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• 2016

In this paper, we studied a light distribution for the LED chips arrangement using an optical design software. The structures of the edge type LED luminaires are reflector plane, LGP(lighting guide plane) and diffuse plane. The reflector plane is on the middle of the overall structure. We had simulation that placing LED chips on the reflector center of the reflector edge by changing the position of LED chips above the reflector center at 1mm, 2mm, and 3mm respectively. In the case, when LED chips are on the center of the reflector, it shows the light distribution of the general diffuse illumination, the semi-direct distribution with 0.56 efficiency and the direct distribution with 0.31 efficiency. And the wedge type LGP shows more efficiency than the flat type. Gradually increasing shape of semi-spherical type by 0.015mm has power of 1.02W, efficiency of 0.25, and maximum luminous intensity of 0.104W/sr, it also and shows the better optical characteristics than the reflector plane that have no patterns. This semi-spherical type shows the better optical characteristics than the reflector plane that have no patterns.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2009.10a
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• pp.205-207
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• 2009

LCD (liquid crystal display) industry is needed to goods of high reliability and is interested in products without harmful material. In this experiment, we made the LED backlight unit for Automotive-navigation. And for making this backlight unit we used to eight side emitting type white LEDs with 1W high power of the lumileds company. We could know that this backlight unit releases to 6500 nit in 14W power consumption and start up voltage time is under the15ms in the ambient temperature -20 $^{\circ}C$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.6
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• pp.488-492
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• 2013

Current limiting diode (CLD) was fabricated using junction field effect transistor (JFET) structured two small cells and eight large cells. Two small cells and eight large cells were connected in parallel and the obtained constant current was 110 mA. The application of CLD in each of the parallel circuits on chip on board (COB) type LED lighting source, could significantly reduce the current deviation within the parallel circuits. The applications of CLD on AC power small lighting source, battery power low voltage parallel lighting source and AC flat lighting source were investigated.

• Korean Journal of Optics and Photonics
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• v.30 no.4
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• pp.142-145
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• 2019

Normally, a corner cube retroreflector (CCRR) sheet is used as a retroreflective mirror array (RRMA) in a volumetric display. Each CCRR unit reflects light in the retroreflective direction, which is parallel to the incident light, and it makes a blurred image, as it shifts the position of light within its dimensions. Adopting a "curved planar wall" and "parabolic focusing" (x-axis), a hybrid-t(transverse direction)-RRMA is proposed, to improve the image quality and brightness. The improvement of image contrast is achieved by tuning a "linear v-shaped groove" structure to a "parabolic v-shaped groove". Also, the system has been simplified and the brightness enhanced 4 times by removing the half mirror.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.368-369
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• 2003

The recent development of InGaN-based white light emitting diodes (LEDs) has expanded their potential applications in areas such as white electric home appliances, backlight for mobile phone or notebook PC, and indoor lightings. In this lecture, recent researches related to the phosphors for LEDs applications and their luminescent properties were reviewed. PDPs are considered as the most potential flat panel displays with a large-screen size. Phosphors in PDPs directly affect the brightness and lifetime. So, many researchers have tried to improve the luminescence characteristics of the phosphors especially under vacuum ultraviolet (VUV) excitation. We overviewed recent research trends and conclusive achievements for the PDP phosphors.

• Journal of Applied Reliability
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• v.9 no.2
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• pp.131-148
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• 2009

An organic light emitting diode (OLED), also light emitting polymer (LEP) and organic electro luminescence (OEL), is any light emitting diode (LED) whose emissive electroluminescent layer is composed of a film of organic compounds. The layer usually contains a polymer substance that allows suitable organic compounds to be deposited. They are deposited in rows and columns onto a flat carrier by a simple "printing" process. The resulting matrix of pixels can emit light of different colors. Such systems can be used in television screens, computer displays, small, portable system screens such as cell phones and PDAs, advertising, information and indication. OLEDs can also be used in light sources for general space illumination, and large-area light-emitting elements. In this paper, we develop the general guide line of the accelerated life test for assuring B10 life of AMOLED(Active Matrix Organic Light Emitting Diode) and PMOLED(Passive Matrix Organic Light Emitting Diode) which are widely used for display monitor less than 115 mm.