• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.6
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• pp.563-569
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• 2023

Micro light-emitting diodes (LEDs), with a chip size of 100 micrometers or less, have attracted significant attention in flexible displays, augmented reality/virtual reality (AR/VR), and bio-medical applications as next-generation light sources due to their outstanding electrical, optical, and mechanical performance. In the realm of bio-medical devices, it is crucial to transfer tiny micro LED chips onto desired flexible substrates with low precision errors, high speed, and high yield for practical applications on various parts of the human body, including someone's face and organs. This paper aims to introduce a fabrication process for flexible micro LED devices and propose micro LED transfer techniques for cosmetic and medical applications. Flexible micro LED technology holds promise for treating skin disorders, cancers, and neurological diseases.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.12 no.1
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• pp.66-74
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• 2013

This paper introduces the improvement of QoS to compensate the decreasing LED performance by temperature characteristic in the LED-ID communication system. LED does not only use as a lighting device, but also uses as a communication device. The conventional system is transmitted by RGB of LED following the mixture color ratio, which determined the color of lighting, and the BER performance of each RGB signals. However, when the LED used consistently, it has occurred the heat temperature. As a result, LED is degraded the performance by increased temperature each device. To solve this problem, we proposed the adaptive modulation and coding scheme by temperature of device to improve the performance of system and satisfied the QoS in the LED-ID system.

• International Journal of Highway Engineering
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• v.13 no.4
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• pp.231-238
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• 2011

Variable message signs(VMS) in use are being displaying with the LED device as the luminous source, and it is a recent trend to be changed from the Lamp type to the Surface-Mount Devices(SMD) type. The LED device leads to get VMS display brightly and clearly, leading to have visibility and legibility better than the existing VMS. However, the lights which display off the road, the unnecessary energy, might have negative effect on ecosystem. This study developed the way of getting the lights be displayed only to drivers without the unnecessary energy and estimated the energy efficiency of the development by the optical testing. As a result, this study showed that the energy consumption of the developed display device appeared to decrease by about 36.1% compared to the existing device. Also the upward and downward angle of the lights changed from an angle of $24^{\circ}C$ to $0^{\circ}C$and from an angle of $-24^{\circ}C$ to $-11^{\circ}C$, respectively. Therefore, it anticipates that the developed device would benefit highway safety due to an improvement in visibility and legibility compared to the existing VMS and the energy consumption would be less lower than the existing VMS.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2005.05a
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• pp.84-88
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• 2005

본 연구에서는 백색광원용 조명램프에 필요한 고밀도로 집적된 LED 어레이를 제작하기 위하여 반도체제조 공정에 필요한 포토마스크를 AutoCAD 상에서 설계하였으며 레이저 리소그래피 장비를 이용하여 포토마스크를 제작하였다. 웨이퍼상에 LED칩을 개별적으로 제작한 후 이들을 직렬 및 병렬로 금속배선하여 연결하였다. 특히 AutoCAD로 각 공정의 포토마스크 패턴을 설계 작업한 후 DWG 파일을 DXF 파일로 변환하여 레이저빔으로 스캔닝하였다. 이를 소다라임 유리판 위에 크롬을 증착한 후 각 패턴에 맞추어 식각 함으로써 포토마스크를 제작하였다. 또한 2인치 InGaN/GaN 다중 양자우물구조의 광소자용 에피박막이 증착된 사파이어 웨이퍼에 포토마스크를 활용하여 반도체 제조공정을 수행하였으며, 금속배선된 백색LED램프를 제작하였다.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1435-1435
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• 2015

광고 및 홍보의 마케팅 수단의 일환으로써 점포별로 QR코드를 사용하는 사례가 급격히 늘고 있다. 정보도트의 일종인 QR코드의 경우는 스마트폰과 더불어 홍보수단의 일환으로 활용되는 사례가 증가하고 있는 반면 QR코드는 정보를 표현할 수 있는 디자인의 범위가 좁고, 전송할 수 있는 Data의 용량이 적으며, 어두운 환경에서의 인식률이 저하되는 단점이 있다. 이에 기존의 QR코드 보다 다양한 디자인이 가능하고 대용량의 Data 전송이 가능한 컬러코드가 대두되고 있다. 컬러코드란 4가지 색상(빨강, 파랑, 초록, 검정)을 이용한 매트릭스 형태의 코드로 각종 디지털 정보를 저장하는 새로운 개념의 데이터 표현 기술이며, 이는 각 컬러에 디지털 정보를 매핑(mapping)하여 콘텐츠나 URL 등의 실제 정보들을 제공하는 역할을 하도록 설계되어 있다. 8MP CMOS센서기반 Colored LED Patch 인식 기법은 VLC에 포함되는 하나의 기술로서 차세대 조명 및 정보 디스플레이 장치로 각광을 받고 있는 반도체 조명 기술인 광원 정보 인식 기법이다. 따라서, 본 논문에서는 8MP CMOS센서 기반 컬러코드 LED Patch 인식 기법에 대해 제안하였다. 8MP CMOS 센서를 이용한 Colored LED Patch 인식 기법 중 하나로서 위치 정보 서비스 등 다양한 정보 획득이 가능하도록 연구하였으며, 동영상, 웹사이트 링크 등 여러 형식에 적용이 가능하도록 하였다. 본 연구에서 사용되는 8MP CMOS센서를 기반 Colored LED Patch 인식 기법을 통해 컬러코드는 코드 플랫폼으로 연결되어 콘텐츠의 위치를 파악하고 이용자에게 콘텐츠 및 정보가 전송된다. 이는 QR코드보다 높은 인식률로 빠르고 편리하게 정보를 제공할 수 있었다. 본 논문에서는 상기 제안 기술을 통하여 LED Patch의 높은 주목성과 가시성을 확보하여 보다 효과적인 광고 및 홍보의 시인성을 확보할 수 있다. 향후 본 제안기술을 통하여 사회 안전망을 위한 위치 및 정보 서비스 제공이 가능하며, 효과적인 광고 효과를 도출할 수 있을 것으로 사료된다.

• Korean Journal of Optics and Photonics
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• v.31 no.6
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• pp.334-343
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• 2020

In this paper, a study of the design of a lighting optical system to form indirect light was conducted, to reduce the glare caused by the hot spot of the LED. In the case of using an LED for indoor lighting, glare is caused because of the high luminance and non-uniform luminance distribution. In particular, LED stands are located close to the user's eyes and are used for a long time, so research to reduce glare is essential. Therefore, in this paper an optical system structural study and the design of an LED stand for glare reduction were conducted. Afterward, the luminance analysis and comparison to an existing LED stand product confirmed that the reflective LED stand proposed in this paper had better performance in terms of glare.

• Horticultural Science & Technology
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• v.31 no.1
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• pp.56-64
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• 2013

Recent unusual weather due to global warming causes shortage of daily sunlight and constitutes one of the primary reasons for agricultural damages. LED light sources are frequently utilized to compensate for the shortage of sunlight in greenhouse agriculture. The present study is aimed at evaluating formations of phytochemicals as well as growth characteristics of mature strawberry fruits ('Daewang' cultivar) during cultivation in a closed growth chamber equipped with artificial LED light as a sole light source. Each LED light of blue (448 nm), red (634 and 661 nm) or mixed blue plus red (blue:red = 3:7) was separately supplied and the intensity of each light was adjusted to $200{\pm}1{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ at plant level with a photoperiod consisted of 16 hours light and 8 hours darkness. Strawberries grown under mixed LED light of blue and red wavelengths showed a higher production of fruits than those grown under other LED treatments. Fructose, one of the free sugars, increased in mixed LED light-grown fruits. Anthocyanin contents were elevated remarkably in the mixed LED light-grown fruits compared with those in other LED treatments. Contrastingly, contents of total phenolics and flavonoids were not of much different from one another among the fruits treated with various LED lights. On the other hand, ripening of strawberry fruits was found to be faster when grown under blue LED light compared with other LED treatments. Moreover, antioxidant activities of blue or red LED light-grown fruits, respectively, were significantly higher than those of mixed LED light-grown fruits. We suggest that when daylight is in shortage during cultivation in a greenhouse, supplementation of sunlight with LED light, which is composed of blue and red wavelengths, could be useful for the enhancement of productivity as well as of free sugar content in strawberry fruits. In addition, for the strawberry culture in the plant factory, selective adoption of LED light wavelength would be required to accomplish the purpose of controlling fruit maturation time as well as of enhancing contents of sugars and antioxidants of fruits.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.12
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• pp.8901-8907
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• 2015

Conventional streetlight with the not-adjustable light distribution characteristic is generating light pollution such as glare, damage to the crops and disturbed sleep, because beam of streetlight is not distributed evenly according to the surrounding areas and road conditions. In this paper, we proposed the new structure LED streetlight controlled light irradiation angle according to the surrounding areas and road conditions. Proposed LED streetlight are available to the adjustable light distribution characteristic using the half-circle angle control device. Result of measurement and simulation, beam angle is made available to control at least from $100^{\circ}$ up to $154^{\circ}$, average illumination exceeded 15% of KS regulation and overall uniformity exceeded more than 50% of KS regulation. the Developed large capacity LED streetlight luminaire is considered to minimize glare and light pollution and optimize uniformity ratio of illuminance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.10B
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• pp.1258-1267
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• 2011

In this paper, using the indoor LED-ID communication system have researched for how to transmit video signals. In LED-ID communications use the LEDs for lighting features at the same time communication is an effective way to implement. This proposed system using Visible light(RGB) as way to transmit signals, depends on the mixture RGB, which decided the color of light, moreover, each things determined their performance. However, if the video signal were fixed allocated RGB to transmit such as the original system, the importance of the each signals a different occur the limit on the quality of the video than SVC signals. In order to solve this problem in this paper, according to the RGB mixture ratios analyze the performance for the White LED, which analyzed based on allocating the SVC signal by transmitting to improve the quality of the video was about how researched.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.46 no.3
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• pp.59-68
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• 2023

Currently, yellow phosphor of Y3Al5O12:Ce3+ (YAG:Ce) fluorescent material is applied to a 450~480nm blue LED light source to implement a white LED device and it has a simple structure, can obtain sufficient luminance, and is economical. However, in this method, in terms of spectrum analysis, it is difficult to mass-produce white LEDs having the same color coordinates due to color separation cause by the wide wavelength gap between blue and yellow band. There is a disadvantage that it is difficult to control optical properties such as color stability and color rendering. In addition, this method does not emit purple light in the range of 380 to 420nm, so it is white without purple color that can not implement the spectrum of the entire visible light spectrum as like sunlight. Because of this, it is difficult to implement a color rendering index(CRI) of 90 or higher, and natural light characteristics such as sunlight can not be expected. For this, need for a method of implementing sunlight with one LED by using a method of combining phosphors with one light source, rather than a method of combining red, blue, and yellow LEDs. Using this method, the characteristics of an artificial sunlight LED device with a spectrum similar to that of sunlight were demonstrated by implementing LED devices of various color temperatures with high color rendering by injecting phosphors into a 405nm deep blue LED light source. In order to find the spectrum closest to sunlight, different combinations of phosphors were repeatedly fabricated and tested. In addition, reliability and mass productivity were verified through temperature and humidity tests and ink penetration tests.