• Title, Summary, Keyword: visible light

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Convex Optimization Approach to Multi-Level Modulation for Dimmable Visible Light Communications under LED Efficiency Droop

  • Lee, Sang Hyun;Park, Il-Kyu;Kwon, Jae Kyun
    • Journal of the Optical Society of Korea
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    • v.20 no.1
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    • pp.29-35
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    • 2016
  • This paper deals with a design method and capacity loss of an efficient multi-level modulation scheme for dimmable visible light communications (VLC) systems that use light-emitting diodes (LEDs) with efficiency droop. To this end, the impact of such an impairment on dimmable VLC is addressed with respect to multi-level modulations based on pulse-amplitude modulation (PAM) via data-rate optimization formulation.

Photopodegradation efficiency of visible light cured dental resin composites with novel photosensitizers (가시광선 중합형 복합수지용 광증감제의 분해율 비교)

  • Sun, Gum-Ju
    • The Journal of Korean Academy of Dental Technology
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    • v.33 no.4
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    • pp.291-297
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    • 2011
  • Purpose: The purpose of this study was to know the availability of three photosensitizers, CQ, PD, DA, as a photosensitizer of dental resin composite. We want to know abortion band around visible light region for the using potential possibility as a photosensitizer for visible light cured dental composite resin. And I studied to know the relative photodecomposition ratio of three photosensitizers with or without photoinitiator, DAEM. Methods: The photodecomposition of three photosensitizers were studied by UV absorption spectroscopy in ethanol and determined by same instrument with irradiation time for relative photodecomposition. In order to study the effect of amine on photodecomposition was added the DAEM in the photosensitizer solution and the relative rate was measured by the same procedure with aove mentioned. Results: The all of three photosensitizers are absorbed around visible light region. The relative rate of decrease in absorbance incereased in the order: CQ < BD < PD. The effect of DAEM on the photodecomposition of the photosensitizers was appeared different results without DAEM. The photodecomposition rate of PD and DA decreased somewhat with the addition of amine, while that of CQ increased. The rtealtive photodecomposition rate increased in the oprder: BD ${\leq}$ CQ < PD with the addition of amine, but the differnce was not significant. Conclusion: PD and DA like CQ gives to the possibility of use as a photosensitizer for visible light cured dental composite resin by absorption around visible light region and photodecomposition in the maximum absorption wavelength. And it is showed that PD and DA are not effective decomposed with amine initiator, DAEM but CQ decomposed with DAEM effectively. This result may be due to a different mechanism operating for the decomposition of photosensitizers in the presence of amine.

A STUDY ON THE PHYSICAL PROPERTIES OF RESTORATIVE MATERIALS FOR PHOTO-POLYMERIZATION OF ARGON LASER (아르곤 레이저를 이용한 광중합 수복재의 물리적 성질에 관한 연구)

  • Ju, Sang-Ho;Choi, Hyung-Jun;Kim, Seong-Oh;Lee, Jong-Gap
    • THE JOURNAL OF THE KOREAN ACADEMY OF PEDTATRIC DENTISTRY
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    • v.25 no.2
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    • pp.368-382
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    • 1998
  • The purpose of this study is to evaluate and compare the results of argon laser for 5 seconds, argon laser for 10 seconds, and visible light for 40 seconds photo-polymerization in compressive strength, microhardness, curing depth, temperature rising during polymerization, and polymerization shrinkage. Hybrid type composite resin(Z-100) and compomer(Dyract) were used to be compared. The compressive strength was measured by an Instron(1mm/min cross head speed) in 60 specimens and the microhardness of the surface was expressed by Vickers Hardness Number(VHN) in 30 specimens. The curing depth was evaluated comparing the different values of upper and lower VHN according to irradiation time and thickness for the light source polymerization in 60 specimens. The temperature rising during photopolymerization was observed by the temperature change with thermocouple sensitizer beneath 40 specimens at the argon laser for 10 seconds and visible light 40 seconds irradiation. The polymerization shinkage was evaluated by calculating the decrease of % volume by using a dilatometer in 30 specimens. The results were as follows ; 1. In the case of compressive strength, the argon laser polymerization groups were higher than visible light group in Z-100 (p<0.05). In Dyract, the argon laser 5 seconds group did not show a significant difference with the visible light 40 seconds group. The argon laser 10 seconds group showed the markedly low value when compared with other groups (p<0.05) 2. In microhardness, Z-100 was better than Dyract when comparing by VHNs (p<0.05); however, there was not a significant difference between two materials in the visible light 40 seconds group and the argon laser 10 seconds group. 3. In the study of curing depth, Z-100 showed the consistent polymerization in argon laser irradiation because there was no difference in the VHN decrease according to the thickness change. Over the thickness control, the results did not show a significant difference between visible light and argon laser group in Z-100; however, in the case of Dyract, the visible light 40 seconds group was better than the argon laser groups(p<0.05). 4. There was a significant difference between the two materials in temperature rising during polymerization (p<0.05), but not a significant difference between irradiation times, 5. There was not a significant difference between the two materials in polymerization shrink age. The argon laser 5 seconds group was smaller than the other groups (p<0.05). It could be concluded that Z-100 polymerization was recommended to use the argon laser for reduction of the irradiation time while Dyract was recommended to use the visible light polymerization.

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A Novel Ultraviolet Sensor using Photoluminescent Porous Silicon (광 루미네슨스 다공질 실리콘을 이용한 새로운 자외선 센서)

  • Min, Nam-Gi;Go, Ju-Yeol;Gang, Cheol-Gu
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.50 no.9
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    • pp.444-449
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    • 2001
  • In this paper, a novel ultraviolet sensor is presented based on a photoluminescent porous silicon. Porous silicon layer was formed by chemical etching of surface of pn junction in a $HF(48%)-HNO_3(60%)-H_20$ solution. Incident ultraviolet(UV) light is converted to visible light by photoluminescent porous silicon layer, and then this visible light generates electron-hole pairs in the pn junction, which produces a photocurrent flow through the device. In order to maximize detection efficiency, the peak sensitivity wavelength of the pn junction diode was matched with the peak wavelength of Photoluminescence from porous silicon layer. The porous silicon ultraviolet sensor showed a large output current as UV intensity increases and but very low sensitivity to visible light. The detection sensitivity of porous silicon sensor was calculated as 2.91mA/mW. These results are expected to open up a possibility that the present porous silicon sensor can be used for detecting UV light in a visible background, compared to silicon UV detectors which have an undesirable response to visible light.

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Development of a Hydroponic Recycle System using the Visible Light-reactive Titanium Dioxide Photocatalyst for Sterilization of Nutrient Solution(I) - Determination of factors - (가시광 감응형 광촉매에 의한 수경재배용 배양액의 재이용 살균시스템 개발(I) - 광촉매 필터 요인시험 -)

  • Chung, Sung-Won;Ha, Yu-Shin;Lee, Jong-Won;Park, Jong-Min;Kwon, Soon-Hong;Lee, Ki-Myung
    • Journal of Biosystems Engineering
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    • v.35 no.6
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    • pp.420-425
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    • 2010
  • We produced a basic system of sterilization of nutrient solution based on the characteristics of coated filter with the visible light-reactive titanium oxide photocatalyst according to the findings of the first stage. We developed a model system with a proper number and arrangement of filter elements, the visible light-reactive titanium oxide photocatalyst according to findings from the basic performance test. Main results of this study were as followers; The ceramic filters showed the best performance of sterilization of nutrient solution. The visible light-reactive titanium oxide photocatalyst sterilized more effectively the nutrient solution under the sunlight than UV light. The sterilization performance by passing repeatedly through a few filter was more efficient than that by treating simultaneously with a large number of filters. The filter with 15ppi in pore size, 20 mm in thickness, and 3 layers in titanium oxide coating was desirable in the intensity and sterilization performance.

A Study on the LED-based Media Transmission Mechanics VLC System Module and Efficiency (LED 조명 기반 미디어 전송기법 가시광통신 시스템 모듈 설계 및 효율 연구)

  • Lee, Jun-myung;Kwon, Jae-hyun;Choi, Jung-won;Park, Keon-Jun
    • The Journal of Korea Institute of Information, Electronics, and Communication Technology
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    • v.6 no.1
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    • pp.51-56
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    • 2013
  • In this paper, we had design the module of the LED-based media transmission mechanics visible light communication system. To implement the media transmission system through visible light communication transmitter, receiver module the using high brightness, we proposed visible light communication system to implement communication distance of up to a maximum transmitter-receiver distance using a variable PD sensor to the receiver and 1~12 the LED light-emitting device to the transmitter. It was increased efficiency of approximately 20% by measuring the performance during lens wearing or not wearing on the LED module to improve the efficiency of the media transmission system.

Design and Implementation of Visible Light Communication Circuit with a Built-in Distance Compensation Function (거리 보상 기능이 내장된 가시광 통신 회로 설계와 구현)

  • Park, Jeong-Uk;Lee, Yong Up
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.40 no.4
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    • pp.740-749
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    • 2015
  • In the visible light (VL) communication based on the conventional LED lights, depending on the increase of the communication range, the signal received at the photodiode of the VL receiver has usually the random distorted and decreased amplitude due to the path loss and fading effects of the VL channel. In order to overcome this problem, we propose, design, and implement the visible light communication circuit based on the comparator threshold voltage, where has a built-in distance compensation function. In addition, the performance of the proposed technique is evaluated and analyzed depending on the distance and communication speed through comparing the proposed VLC system based on the threshold voltage with the conventional one.

A Study on Performance of Visible Light Wireless Communication System in Marine Environment (해양 환경에서 가시광 무선통신 시스템의 성능에 관한 연구)

  • Yu, Sung Yub;Jang, Se Bong;Cha, Jae Sang;Kim, Suk Chan
    • Journal of Satellite, Information and Communications
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    • v.11 no.2
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    • pp.65-68
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    • 2016
  • In this paper, visible light wireless communication system according to the climate is studied in the marine environment. The light visibility can be determined by the different weather conditions (clear air, rain, storm, fog) in Kim's atmospheric channel model. By simulating the OOK-NRZ modulation technique, the BER performances are compared in the different weather conditions. In the field test, the error bit is measured in the visible-light communication. The effectiveness of visible light communication in the marine environment is confirmed by comparing the analysis of simulations and field experiments.

LED based Visible Light Communication System using Broadcast Method (브로드캐스트 방법을 이용한 LED 기반 가시광 통신 시스템)

  • Lee, Jong-sung;Oh, Chang-heon
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • pp.641-642
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    • 2018
  • LED-based visible light communication requires separate transmission and reception equipment and is capable of communication only in the range of the light source. Also, there is an advantage that it can be used in a frequency sensitive area using a visible light band. Research is needed to apply these advantages and characteristics to various fields. In this paper, we implemented and verified the functions of the visible light communication system using broadcast methods.

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