• 전기학회논문지
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• 제59권5호
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• pp.996-1000
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• 2010

In order to apply VLC (visible light communication) in harsh environment of nuclear power plant in-containment building, the high luminance LEDs, which are key components of the VLC system, have been gamma irradiated at the dose rate of 4 kGy/h during 72 hours up to a total dose of 288 kGy. The radiation induced coloration effect in the high luminance LED bulb made of acryl or plastic material was observed. In the VLC wireless data transmission experiment using the high luminance LEDs irradiated by high dose rate gamma-ray, the radiation induced coloration effect of the high luminance LED bulb extended the communication distance compared to non-irradiated LEDs.

• 제어로봇시스템학회논문지
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• 제16권6호
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• pp.586-591
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• 2010

VLC (Visible Light Communication) is a wireless communication method using light that is visible to the human eye. It has a major advantage that it causes no interference to RF-based devices. This makes wireless communication possible in RF hazardous areas such as nuclear facilities. In order to apply VLC communication in harsh environment of nuclear power plant, the high luminance LEDs, which are key components of the VLC communication, have been gamma-ray irradiated at the dose rate of 4kGy/h during 72 hours up to a total dose of 288 kGy. The radiation induced color-center was formed in the LED housing cap made of transparent plastic or acryl material. The beam degradations of high luminance LEDs by high dose-rate gammaray irradiation are analyzed using color CCD image processing technology.

• 한국세라믹학회지
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• 제52권4호
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• pp.229-233
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• 2015

Currently, the majority of commercial white LEDs are phosphor converted LEDs made of a blue-emitting chip and YAG yellow phosphor dispersed in organic silicone. However, silicone in high-power devices results in long-term performance problems such as reacting with water, color transition, and shrinkage by heat. Additionally, yellow phosphor is not applicable to warm white LEDs that require a low CCT and high CRI. To solve these problems, mixing of green phosphor, red phosphor and glass, which are stable in high temperatures, is common a production method for high-power warm white LEDs. In this study, we fabricated conversion lenses with LUAG green phosphor, SCASN red phosphor and low-softening point glass for high-power warm white LEDs. Conversion lenses can be well controlled through the phosphor content and heat treatment temperature. Therefore, when the green phosphor content was increased, the CRI and luminance efficiency gradually intensified. Moreover, using high heat treatment temperatures, the fabricated conversion lenses had a high CRI and low luminance efficiency. Thus, the fabricated conversion lenses with green and red phosphor below 90 wt% and 10 wt% with a sintering temperature of $500^{\circ}C$ had the best optical properties. The measured values for the CCT, CRI and luminance efficiency were 3200 K, 80, and 85 lm/w.

• 한국수산과학회지
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• 제41권6호
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• pp.511-517
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• 2008

The radiation characteristics and economic efficiency of high - luminance light - emitting diodes (LEDs), a metal halide lamp, and a halogen lamp were studied to evaluate their potential as an energy-saving light source for fishing lamps. The wavelengths at which irradiance was maximum were 709, 613, 473, 501, 525, 465, 578, and 973 nm for red, orange, blue, peacock blue, green, and white LEDs, the metal halide lamp, and the halogen lamp, respectively. If the irradiance characteristics at 300-1,100 nm wavelengths are set as 100%, the irradiance rates at 381-780 nm were 99-78%, 82%, and 24% for the LEDs, metal halide lamp, and halogen lamp, respectively. The economic efficiency was superior in the order metal halide lamp, halogen lamp, peacock blue LED, and blue LED at 381-780 nm and metal halide lamp, peacock blue LED, blue LED, and halogen lamp at 480-520 nm. Based on the radiation characteristics and economic efficiency evaluated at 480-520 nm, the blue and peacock blue LED light sources can be used as energy-saving light sources for fishing lamps.

• 전력전자학회논문지
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• 제20권3호
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• pp.223-231
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• 2015

LEDs have been widely used in lighting displays, automobiles, and airplanes owing to their excellent light output characteristics and long lifespan. Though LEDs are manufactured under the same process, variations in impurity concentrations cause electrical deviation among LEDs. The resulting electrical deviation can not only reduce the life time of the LED but also cause non-uniform luminance of LEDs connected in parallel. LED driving circuit is required to solve these problems. In this paper, we propose a LED driving system using Y-type current balancing transformer to maximize the efficiency of the system by removing output stage Schottky diodes. Experimental results are presented to verify the performance of proposed LED driving system that is applied to 80 W LED modules.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2009년도 IWAIT
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• pp.476-481
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• 2009

In this paper, we propose a visible light road-to-vehicle communication system at intersection as one of ITS technique. In this system, the communication between vehicle and a LED traffic light is approached using LED traffic light as the transmitter, and on-vehicle high-speed camera as the receiver. The LEDs in the transmitter are emitted with 500Hz and those emitting LEDs are captured by a high-speed camera for making communication. The images from the high-speed camera are processed to get luminance value of each LED in the transmitter. For this purpose, first transmitter should be found, then it should be tracked for each frame, and the luminance value of each LED in the transmitter should be captured. In our previous work, transmitter was found by getting the subtraction of two consecutive frames. In this paper, we mainly introduce an algorithm to detect the found transmitter in consecutive frames. Experimental results using appropriate images showed the effectiveness of the proposal

• 한국전자통신학회논문지
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• 제10권5호
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• pp.615-622
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• 2015

반도체 제조기술의 발달로 고효율 및 고휘도의 LED가 개발됨에 따라 재래식 조명들로부터 LED를 이용한 조명으로 조명산업이 이동하는 추세이다. LED 조명등은 에너지 효율이 재래식 조명보다 뛰어나지만 많은 열이 발생한다는 단점이 있다. 특히 대형 LED 조명등에서는 이러한 발열문제가 심각한 실정으로, LED에 의한 메탈기판의 열은 납땜 부분을 열화시켜 조명등의 수명을 단축시키는 주된 원인이 된다. 따라서 대형 조명등을 개발하기 위해서는 이러한 열 문제를 해결하는 것이 매우 중요하다. 본 연구에서는 대형 LED 조명등에서 열문제를 해결하기 위한 방법을 제시하였고, 제시한 방식으로 1200W급 LED 조명등을 개발하였다. 본 연구에서 이용한 방법은 LED 조명등에 워터재킷을 설치하여 냉각수를 채웠으며, 소형의 수중펌프를 이용하여 냉각수를 순환시키는 방법을 이용하였다.

• 한국산학기술학회논문지
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• 제16권11호
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• pp.7256-7261
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• 2015

본 논문은 식물 재배시스템을 제작하고 LED 광원은 단색광 3개(적색, 청색, 백색), 혼합광 3개(적색1+청색1, 적색2+청색1, 적색1+청색2)를 제작하여 사용하였다. 제작한 식물 재배시스템을 이용하여 LED 광원별 광 특성, 광량의 변화에 따른 조도 및 PPFD의 특성과 식물성장을 분석하였다. 분석결과 LED 광원의 광 효율은 백색 광원이 125 lm/W로 높으며 적색1+청색2 광원은 9.9 lm/W로 낮았다. 이러한 결과로 단색광이 혼합광 보다 광효율이 좋은 것을 확인 할 수 있었다. LED의 파장별 PPFD ($25{\mu}mol$, $50{\mu}mol$, $100{\mu}mol$) 조도값 크기는 백색 LED가 높으며 청색 LED가 낮았다. 따라서 LED 광원의 다양한 단색 혼합광 파장대역 조합에 따라 식물성장에 적합한 효율적인 LED 조명 시스템을 구성할 수 있다.

• Current Optics and Photonics
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• 제7권6호
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• pp.755-760
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• 2023

In this paper, an illumination optical system that can mitigate the saturation phenomenon in the center of an image (caused by the typical flexible-endoscope illumination system using LEDs with Lambertian light distribution) is designed. When an LED with Lambertian light distribution is used as a light source, the amount of light in the center of the endoscopic illumination system is relatively high, compared to the periphery, causing saturation in the image. Since this phenomenon causes difficulty in detecting the patient's lesion, it is necessary to find a lighting-system design that can alleviate the saturation phenomenon. Therefore, in this paper a lighting system with bat-wing light distribution, which can lower the intensity at the center and secure the maximum amount of light at the maximum light distribution angle, is designed. In addition, to check the performance of the designed lighting system, a simulation of illumination and luminance is conducted for a system using a common aspherical lens with otherwise the same components. As a result, it is confirmed that the lighting system designed in this paper effectively reduces the luminance value at the center and secures more luminance values at the periphery than the familiar lighting system.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.215-215
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• 2014

Red color light emitting diodes (LEDs) were fabricated using CdSe/CdZnS quantum dots (QDs). During the device fabrication process, oxygen plasma treatment on the ITO surface was performed to improve the interfacial contact between ITO anode and the hole injection layer. CdSe/CdZnS quantum dots were cross-linked to remove their surrounded organic surfactants. The device shows red emission at 622 nm, which is consistent with the dimension of the QDs (band gap=1.99 eV). The luminance shows 6026% improvement compared with that of LEDs fabricated without oxygen plasma treatment and quantum dots cross-linking process. This approach would be useful for the fabrication of high-performance QLEDs with ITO electrode and PEDOT:PSS hole injection layers.