• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.464-467
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• 2002

We propose the use of visible scintillation light for monitoring the X-ray CT in the gantry of a diagnostic CT for its performance test and maintenance works. We placed a disk of bare plastic scintillator disk in the gantry opening area of a helical X-ray CT. When we operated the CT, we could observe the emission of blue scintillation light from the scintillator in a dark room. Visible light was identified under all scanning conditions of diagnostic uses. As a result, we observed the direction and the spread of the incident X-ray in the scintillator. We also observed the change of the part of the scintillator where visible light was generated, and the move that took place associating with the rotation of the X-ray tube during one CT scan. On the basis of the observation, we examined the usefulness of the visible scintillation light as a convenient performance-evaluating tool as well as a maintenance tool of the CT.

• 대한지구과학교육학회지
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• 제8권1호
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• pp.35-44
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• 2015

The purpose of this paper is to identify the conceptions of middle school and high school students about visible light, Ultra violet(UV) and Infrared ray(IR). We administered questionnaire 40 people of middle school 3rd students and 43 people of high school 2nd students in Gyeonggi-do. Misconceptions about visible light, UV and Ir were observed in many students. The results of study are as follows: Firstly, Many students think that it is possible to see objects without visible light. The explanations given by students for the visiblity of objects in darkness indicates a heavy reliance on personal experiences. Secondly, we have confirmed that high school students well understand the fact that the object reflects the light. However, a significant number of students exhibited an eye-centered perspective of vision. Thirdly, students had a variety of ideas about the meaning of the term UV and IR. Analysis of questionnaire data indicates that many students believe that it is possible to see objects in the presence of UV light alone.

• Current Optics and Photonics
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• 제1권2호
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• pp.90-94
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• 2017

Visible light identification (VLID) is a user identification system for a door lock application using smartphone that adopts visible light communication (VLC) technology with the objective of high security, small form factor, and cost effectiveness. The user is verified by the identification application program of a smartphone via fingerprint recognition or password entry. If the authentication succeeds, the corresponding encoded visible light signals are transmitted by a light emitting diode (LED) camera flash. Then, only a small size and low cost photodiode as an outdoor interface converts the light signal to the digital data along with a comparator, and runs the authentication process, and releases the lock. VLID can utilize powerful state-of-the-art hardware and software of smartphones. Furthermore, the door lock system is allowed to be easily upgraded with advanced technologies without its modification and replacement. It can be upgraded by just update the software of smartphone application or replacing the smartphone with the latest one. Additionally, wireless connection between a smartphone and a smart home hub is established automatically via Bluetooth for updating the password and controlling the home devices. In this paper, we demonstrate a prototype VLID door lock system that is built up with LEGO blocks, a photodiode, a comparator circuit, Bluetooth module, and FPGA board.

• 한국전자통신학회논문지
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• 제6권3호
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• pp.425-432
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• 2011

LED 무선 가시광 통신기술의 성능을 1Gb/s 이상으로 높이기 위해서는 실내환경에서 다중 반사로 인한 멀티패스 효과를 없애주어야 한다. 본 논문에서는 이러한 멀티패스 효과를 없애주기 위하여 빔포밍 기술을 접목한 LED 무선 가시광 LAN 통신을 위한 MAC 프로토콜을 제안하고자 한다. 본 MAC 프로토콜은 각 방향으로 빔포밍 된 빛을 각 방향에 대한 방향코드와 함께 송신하는 절차가 삽입되어 있는 것이 특징이다. 또한, 기존의 무선 LAN 과는 달리 충돌감지가 어려운 무선 가시광 통신의 특징을 감안하여 중앙 집중형 polling 기법을 사용하였다. 또한 본 논문에서 제안한 MAC 프로토콜의 성능을 평가하여 그래프로 나타내었다.

• 전기학회논문지
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• 제59권11호
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• pp.2043-2047
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• 2010

This study is to solve problems of depletion of RF bandwidth frequency, confusion possibility, security that current wireless communications system have and is to confirm possibility of applying next generation network. To solve problems of current wireless communications system, visible light communications system for power line communications using ATmega16 Microcontroller is was realized and receiver property was analyzed. PLC exclusive chip APLC-485MA, Microcontroller ATmega16, 5pi bulb type LED and high flux LED, visible light receiving sensor LLS08-A1 were used for transmitter and receiver. Performance was analyzed by designed program and an oscilloscope. It was showed average 20% improved receiver rate rather than bulb type LED in the case of high flux LED through voltage change rate on communication distance and LED type of distance between 10 to 50 cm. The blue LED showed the best performance among measured LED types with above 10% of voltage decreasing rate. But As it gradually becomes more distant, the precise date was difficult to obtain due to weak light. To overcome these sort of problems, specific values such as changing conditions and efficiency value relevant to light emitting parts and visible light receiving sensor should be calculated and continuous study and improvements should also be accomplished for the better communications condition.

• 한국위성정보통신학회논문지
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• 제10권2호
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• pp.46-53
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• 2015

Visible Light Communication (VLC)은 Light Emitting Diode (LED)를 사용하여 조명의 역할과 통신의 기능을 동시에 구현할 수 있는 효과적인 방법이다. VLC는 통신 가능 영역인 Field Of View (FOV)를 가져 높은 보안성을 가지고, 가시광을 이용해 고속의 데이터 전송이 가능하다. VLC 시스템에서 RGB 채널에 데이터를 분할하여 전송하는 방법은, RGB 채널에 동일한 데이터를 전송하는 방법에 비해 빠른 데이터 전송 속도를 가지고 있으나, 가시광의 산란 및 반사로 인한 데이터의 burst 에러가 발생할 시 복원이 불가능하여 BER 성능의 열화가 발생한다는 단점이 존재한다. 이러한 문제를 해결하기 위해 VLC에서 빠른 데이터 전송률을 가지면서 BER 성능 향상을 만족하는 2-step 인터리빙 기법을 제안한다. 제안 시스템의 Cyclic 인터리빙과 convolutional 인터리빙을 통해 RGB 채널의 성능 평준화 및 데이터 에러율의 감소로 전체 시스템의 BER 성능이 향상됨을 확인 할 수 있다.

• 한국ITS학회:학술대회논문집
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• 한국ITS학회 2010년도 춘계학술대회
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• pp.141-144
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• 2010

• 대한치과기공학회지
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• 제33권4호
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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.

• 대한소아치과학회지
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• 제25권2호
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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.

• 한국정보전자통신기술학회논문지
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• 제6권1호
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• pp.51-56
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• 2013

본 논문에서는 LED 조명을 기반으로 미디어 전송기법 가시광통신 시스템 모듈 설계 및 효율 연구와 성능분석을 하였다. 고휘도 Withe LED조명을 이용한 가시광통신(Visible Light Communication) 송 수신기 모듈을 통해 미디어 전송 시스템을 구현하기 위해 송신부에는 1~12개의 LED 발광 소자와 수신부에는 PD(Photo Diode)센서를 구성하여 전송속도에 따른 최대 송 수신의 통신 거리를 실험해 보고자 가시광통신 시스템을 제안하였다. 또한 미디어 전송 시스템의 효율을 증대시키기 위해 LED모듈에 렌즈 착용시와 미착용시 각각의 성능을 측정하여 약 20%의 효율이 증가하였음을 확인 할 수 있었다.