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Uh-Chan Ryu,Yong Wook Lee 한국조명·전기설비학회 2017 조명·전기설비학회논문지 Vol.31 No.8
In measuring optical properties of lighting with a colored surface using an integrating sphere, it is necessary to calibrate out the variations caused by the surface color as recommended in the IES LM-79-08. Assuming hemispheres as non-fluorescent surfaces of test samples such as LED lamps, LED luminaires, etc., the sizes and the colors of the hemispheres are changed to give variations of the optical properties tested in the integrating sphere. Real measurement data and simulation results for a 0.5-m diameter integrating sphere were compared to give another simulation for a 2-m diameter integrating sphere. Calibration effectiveness will be shown in terms of total luminous flux (TLF), xy color coordinates, correlated color temperature (CCT) and color rendering index (CRI) in a 0.5-m diameter integrating sphere. As the hemisphere diameters are increased from 3cm to 20cm and those colors are varied, TLF decreased up to 61%, and CCT increased from 3452K to 4366K. CRI was raised by 11 without calibration. The deviations of TLF, CCT and CRI were decreased to less than 5%, 22K and 0, respectively, with the calibration procedure, even if the hemisphere sizes were increased up to 0.2m. This implies that a proper calibration procedure for an integrating sphere assures accurate measurement for large-sized samples.
Transmission-Type Polarization-Insensitive Polarization Plane Excitation
Ryu, Uh-Chan,Jo, Songhyun,Choi, Sungwook,Lee, Seul-Lee,Jeong, Jun Hyeok,Jeong, Sun Jae,Christian, Nouaze Joseph,Kim, Jihoon,Kang, Hyun Wook,Nam, Seung Yun American Scientific Publishers 2017 Journal of Nanoscience and Nanotechnology Vol.17 No.11
<P>In optical communications, light polarization of optical signals is randomly varied during the signal transmission, and system performances can be deteriorated by polarization-dependent loss and gain or polarization-mode dispersion. Polarization scrambling that actively changes the state of polarization (SOP) using a polarization modulation method is often utilized to reduce polarization-related impairments. To make use of polarization-dependent routing devices during the transmission, however, scrambled or depolarized light should be polarized and then scrambled again after passing through the routing devices. Here, we suggest a novel polarization-insensitive polarization plane excitation scheme that enables transmission-type polarization-dependent routing elements to exploit their polarization-dependent routing functions irrespective of the SOP and degree of polarization of an input beam. The proposed scheme is composed of a polarization beam splitter (PBS) for a polarization-diversified loop, two half-wave plates (HWPs) and two 45 degrees Faraday rotators (FRs) for irreciprocal polarization transformation. We could make unpolarized light selectively excite one of the two principal axes of a polarization-dependent element using the polarization decomposition/superposition property of the polarization-diversified loop and the irreciprocal nature of optical Faraday rotation. The operation principle of the proposed scheme is explained using the polarization evolution of light passing through the PBS, FRs, and HWPs that comprise the scheme. The theoretically predicted operation was experimentally verified by utilizing a long-period fiber grating (LPFG) inscribed on high birefringence fiber (HBF) as a polarization-dependent element. The LPFG written on HBF has polarization-dependent loss bands at two resonance wavelengths. By controlling the four waveplates, one of the two loss bands of the LPFG could be selected even for unpolarized input light.</P>
편광상이 고리 구조 기반 사냑 간섭계를 이용한 편광 간섭형 광섬유 압력 센서
류우찬(Uh-Chan Ryu),최성욱(Sung Wook Choi),이용욱(Yong Wook Lee) 한국조명·전기설비학회 2015 조명·전기설비학회논문지 Vol.29 No.7
In this paper, we demonstrated a polarimetric fiber pressure sensor using a polarization-diversity-loop-based Sagnac interferometer(PDLSI) composed of polarization-maintaining fiber(PMF) and a fiber Bragg grating(FBG). In order to compare the pressure sensitivity for various kinds of PMF, three kinds of bow-tie PMF were employed as sensor heads. The maximum pressure sensitivity was measured as approximately -15.07㎚/MPa, and an R2 value to represent sensor linearity was measured as ∼0.992 at the sensor system using corresponding PMF over a pressure range of 0-0.3MPa. An FBG was utilized and located adjacent to the PMF segment for compensating temperature-induced errors in the measurement of pressure. The pressure sensitivity of the proposed sensor was improved by approximately four times compared with the previously reported pressure sensor based on polarization-maintaining photonic crystal fiber.
Hyeong-Seob Jo,Uh-Chan Ryu 한국조명·전기설비학회 2017 조명·전기설비학회논문지 Vol.31 No.10
Recent studies have been performed regarding various methods of improving the colour rendering property of white LEDs. One of these methods is mixing the white and red LED spectra, but the specific combination results have been insufficient. Furthermore, CRI variations have not been represented during CCT changes in a white light composed of warm and cool white LEDs. In this paper, CRI variations in the CCT-tunable LED light in conjunction with a red LED will be presented according to the combination of the white and red LED spectra by simulation.
시뮬레이션 프로그램을 이용한 Melanopic-to-photopic Ratio(α-opic) 및 연색특성 향상에 대한 연구
김종오(Jong-Oh Kim),류우찬(Uh-Chan Ryu) 한국조명·전기설비학회 2022 조명·전기설비학회논문지 Vol.36 No.4
Invention of artificial lights has extended human activity time, which has greatly contributed to the development of modern civilization. However, continuous exposure of artificial lights has reduced human sleeping time, which causes a decrease in melatonin production resulting in the side effects such as insomnia, depression, and so on. To prevent the reduction of melatonin by the artificial lights, LED packages helping melatonin generation have been developed. While the commercial LED packages have a high melanopic to photopic ratio (M/P ratio) due to their peak wavelength near the melatonic response around 490nm, those cannot accurately express several colors, that is, give a low R<SUB>9</SUB> or R<SUB>12</SUB> value less than 60 resulting from the peak. Since M/P ratio has a similar formula to that of scotopic to photopic ratio (S/P ratio), the former would have a trade-off relation with color rendering properties as the latter. Therefore, those should be optimized to have values above a certain level by adjusting LED package’s spectral compositions. In this study, M/P ratio and color rendering characteristics were simulated by special combination of 4 blue LEDs and 7 types of phosphors. As a result, the M/P ratios were 0.67, 0.72, 0.78, 0.9, 1.04, 1.14, 1.23, and 1.35 or more. Also, the color rendering properties were R<SUB>a</SUB>≥89, R<SUB>9</SUB>≥75, R<SUB>12</SUB>≥80, R<SUB>9-14</SUB>≥83, and Q<SUB>a</SUB>≥79.
조명용 고출력 발광다이오드의 Decapsulation 기술
임수현(Sue-Hyun Lim),류우찬(Uh-Chan Ryu),조용익(Young-Ick Cho),여인선(In-Seon Yeo) 한국조명·전기설비학회 2011 한국조명·전기설비학회 학술대회논문집 Vol.2011 No.5월
고출력 발광다이오드(LED)는 장수명, 저전력, 친환경 등의 장점이 있어서 기존 조명 대체용 조명 광원으로 각광받고 있으나 LED조명 온도 상승은 열화 및 Wire 단선을 야기하여 고장을 일으킨다. 고장 제거 및 고장 재발 방지를 위해 발생 고장의 고장모드에 대한 체계적인 분석 과정이 필요하다. 본 연구에서는 조명용 고출력 LED 케이스 제거 방법인 Decapsulation에 대해 알아보고자 한다.
LED조명 반사 스펙트럼이 적분구 광학 특성에 미치는 영향
배문섭(Mun-Seob Bae),류우찬(Uh-Chan Ryu) 한국조명·전기설비학회 2016 조명·전기설비학회논문지 Vol.30 No.7
To measure optical properties of an LED lamp with a colored surface using an integrating sphere, its properties are influenced by not only the emission color of the lamp but also the color of the non-emitting surface. This study was conducted to evaluate the effect of the non-emitting color surface experimentally. The fluctuations of the optical properties according to the various colors and sizes of the non-emitting surface of the LED lamp were tested and analyzed in an integrating sphere as recommended in the IES LM-79-08. It is possible to correct the total luminous flux(TLF) less than 1.7%, the xy color coordinates 0.0014, the correlated color temperature(CCT) 62K, color rendering index(CRI) 0 even though the non-emitting surface area is up to 2.9% of the surface area of the integrating sphere. Through the calibration process it is possible to suppress the TLF to 5%, CCT 170K, CRI 1, while the non-emitting surface area is increased to 9.28% of that of the integrating sphere.