• 센서학회지
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• 제29권2호
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• pp.75-81
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• 2020

We introduce a new visible light communication (VLC) method in which three-level return-to-zero (RZ) modulation is used for flicker-free transmission. In the VLC transmitter, the three-level RZ modulation ensures that the average optical power is constant; thus, a flicker-free light-emitting diode (LED) light is achieved. In the VLC receiver, a resistor-capacitor high-pass filter is used for generating spike signals, which are used for data recovery while eliminating the 120 Hz optical noise from adjacent lighting lamps. In transmission experiments, we applied this method for wireless transmission of an air quality sensor message using the visible light of an LED array. This configuration is useful for the construction of indoor wireless sensor networks for air pollution monitoring using LED lights.

• 한국전자파학회논문지
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• 제21권8호
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• pp.905-910
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• 2010

본 논문에서는 조명용 LED(Light Emitting Diode)의 스위칭 구동 회로를 이용한 변조 기법으로 조명 기능과 무선 통신 기능을 동시에 수행하는 가시광 통신(VLC: Visible Light Communication) 시스템을 제안하였다. 본 방식은 기존의 선형 영역에서 동작하는 LED 구동 회로를 갖는 가시광 통신 시스템에 비해 고효율이므로 고출력의 조명용 LED 시스템에 적용할 수 있는 장점이 있다. 제안된 시스템의 유용성을 입증하기 위하여 디지틀 방식의 오디오 시스템을 채용하여 가시광 통신 시스템을 구현하고, 그 실험 결과를 제시함으로써 제안된 방식의 우수성을 검증하였다. 실험 결과, 제안 회로의 시작품은 특별한 광필터 없이 20 W급 조명을 사용해서 약 1.5 m의 반경에서 최대 10 Mbps의 데이터 전송률을 달성하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.241-241
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• 2010

Recently high and persistent spontaneous buildup of a surface potential (SP) upon vacuum deposition of tris (8-hydroxyquinolinato) aluminum (III) ($Alq_3$), which is widely used for organic light emitting devices. The removal of the giant surface potential by visible light irradiation has also been reported. In this study, we coated $Alq_3$ on the FTO substrate and raise the capacity for absorbing sun light. The $Alq_3$ which is green light emitting diode emits light at wavelengths between 500 and 550nm. If we apply one's FTO/$Alq_3$ substrate in one's DSSC, we could get higher energy conversion efficiency because the N719 dye that we used for fabricating the DSSC emits light just at near 540nm. The energy conversion efficiency of approximately 4.8 % at the condition of irradiation of AM 1.5 (100 mW/$cm^2$) simulated sunlight, and the $J_{sc}$ is 12.0 mA/$cm^2$, $V_{oc}$ is 0.71 V, FF is 0.56, respectively.

• 한국통신학회논문지
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• 제37권4A호
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• pp.219-226
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• 2012

본 연구는 조명 및 무선통신이 동시에 가능한 가시광 송수신기에 대해 가시광 통신 본연의 가시성, 무선 통신의 사용 편의성 그리고 고속의 통신 속도를 고려해 edge-emitting laser diode와 silicon photo diode를 기반으로한 고속 가시광 무선 송수신기를 구현하였다. 제안된 가시광 무선 송수신기는 120Mbit/s의 고속에서 양방향 전송이 가능하도록 설계되었으며 이때 발생하는 누화(crosstalk)를 방지하기 위한 방법으로 shielding 방식을 적용해 가시광 송수신기의 성능을 실험적으로 측정 분석하였다. 또 수신기의 시야각 확대를 위한 방법으로는 새로운 구조의 광학적 antenna를 적용해 광학적 antenna가 없는 두 개의 송수신기 사이의 전송링크 특성과 광학적 antenna를 사용한 두 개의 송수신기 사이의 전송링크 특성을 2차원 평면상에서 전송거리, 적용범위 그리고 기울임 정도를 변화시켜 실험과 시뮬레이션을 통해 그 성능을 비교 분석하였다.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2010년도 춘계학술대회
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• pp.226-229
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• 2010

발광다이오드(Light Emitting Diode; LED)는 p형과 n형의 반도체 접합에서 다이오드양단에 전압을 가하여 정공과 전자가 접합부분에서 결합하면서 그 밴드갭만큼의 에너지가 빛으로 발광되는 현상을 이용한 다이오드 소자의 일종이다. 최근 고휘도 LED소자가 신호등이나 어선의 집어등 등에서 기존의 백열전구를 대체하고 있으며, 또한 디스플레이분야에서도 LED와 더불어 광범위하게 사용되고 있다. 또한 LCD 디스플레이의 백라이트로 사용되기 시작하면서 새로운 영역을 개척하고 있다. 한편으로는 가시광영역의 LED 소자의 빛에 디지털 정보를 실어서 보내는 LED 통신기술이 개발되어서, 조명이나 디스플레이기능과 동시에 디지털 정보를 전달하는 분야에 적용되는 노력이 이루어지고 있다. 본 논문에서는 이러한 LED통신시스템을 위한 기반 기술들을 살펴보고, LED통신의 응용분야에 대한 고찰하고자 한다.

• International journal of advanced smart convergence
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• 제1권1호
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• pp.52-56
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• 2012

As inexhaustible clean energy, solar energy will be the most ideal green energy in the 21st century. The effective method to convert solar energy into electrical energy is by solar photovoltaic power generation technologies. LED Emitting Diode is a kind of component which can transform electricity into visible light. As the smart current control system for photovoltaic street lights, the proposed system has improved the battery charging and discharging mechanism to extend the lifespan and effectively controls the LED discharge current according to battery charge state and lighting.

• ETRI Journal
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• 제18권3호
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• pp.181-193
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• 1996

A blue light emitting device has been successfully fabricated using a polymer with regulated conjugation length containing trimethylsilyl substituted phenylenevinylene units. Electroluminescence from the device has an emission maximum at 470 nm. The device shows typical diode characteristics with operating voltage of 20 V and the light becomes visible at a current density of less than $0.5;mA/cm^2$. The electroluminescence spectrum is virtually identical with the photoluminescence spectrum, indicating that the radiation mechanisms are the same for both. A light emitting device using the blend of a large band gap polymer and a small band gap polymer was also fabricated. Light emission from the small band gap polymer shows much improved quantum efficiency, but there is no light emission from the large band gap polymer. Quantum efficiency of the blend increases up to about two orders of magnitude greater than that of the small band gap polymer with increasing proportion of the large band gap polymer. The improvement in quantum efficiency is interpreted in terms of exciton transfer and the hole blocking behaviour of the large band gap polymer. Finally, we have fabricated a patterned flexible light emitting device using the high quantum efficiency polymer blend system.

• 정보와 통신
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• 제28권12호
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• pp.50-60
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• 2011

Visible light communication(VLC) is one type of short-range, optical, and wireless communication system utilizing light emitting diode(LED) and laser diode(LD) as optical source. In a VLC system, visible light is used as a transmission medium and used to illuminate. Using VLC has a lot of advantages: it is harmless to human body; it transmits with high power, and it has excellent security, a high data rate, and a license free frequency band. With such a unique blend of communication and illumination in one system, the most common application would be an indoor environment. We aim at reviewing key issues in VLC network such as : FOV(field of view), priority MAC, cooperative MAC, link switching, LED-ID technique, cell site diversity, and link recovery.

• 센서학회지
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• 제30권4호
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• pp.196-203
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• 2021

In this study, an optical identification system was developed, wherein visible light is used to transmit the interrogating signal, and infrared is used to send the response signal. In the reader, visible light from a light emitting diode (LED) array was modulated via modified pulse width modulation for flicker-free illumination and dimming control. Moreover, the duty factor of the dimming control time was employed to control the illumination from the LED. In the transponder, the spike signal in the output of the high-pass filter was utilized to recover the interrogating signal while preventing interference from the 120-Hz noise from adjacent lighting lamps. The illumination was controlled in 26-86% range of the constant wave LED illumination by changing the duty factor from 20% to 90%. This configuration is advantageous for the construction of optical identification systems for automatic security check and car fare calculation at toll gates or parking facilities.

• 센서학회지
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• 제29권3호
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• pp.149-155
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• 2020

In this study, we employed Manchester code for illumination control and flicker prevention of the light-emitting diode (LED) used in a visible light communication (VLC) system. In the VLC transmitter, the duty factor of the Manchester code was utilized for illumination control; in the VLC receiver, the spike signal from an RC-high pass filter was utilized to recover the transmitted signal whilst suppressing the 120-Hz noise arising from adjacent lighting lamps. Instead of the clock being transmitted in a separate channel, a syncmark signal was transmitted in front of each data byte and used as the reference time for transforming the Manchester code to non-return-to-zero (NRZ) data in the receiver. In experiments, the LED illumination was controlled in the range of approximately 12-84% of the constant wave (CW) light via changing of the duty factor from 10% to 90%. This scheme is useful for constructing indoor wireless sensor networks using LED light that is flicker-free and presents capability for illumination control.