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시뮬레이션을 통한 455nm 청색 LED 여기 광원과 형광체 조합에 따른 연색특성 변화 연구
조형섭(Hyeong-Seob Jo),김종오(Jong-Oh Kim),류우찬(Uh-Chan Ryu) 한국조명·전기설비학회 2019 조명·전기설비학회논문지 Vol.33 No.12
Recently, studies have been performed regarding to various methods of improving color rendering properties of white LEDs by mixing warm white (WW) and cool white (CW) or red (R), green (G), blue (B), and yellow (Y) LED spectra. However, the previous researches have been insufficient in presenting maximum optical characteristics over all correlated color temperature (CCT) ranges or representing recently suggested evaluation methods of color rendering properties. In this paper, color rendering properties including the recent methods at all CCTs will be investigated through simulation combining various kinds of phosphors excited by a 455nm blue LED. For evaluating CRI values, general and special color rendering indices (R<SUB>a</SUB> and R<SUB>9∼14</SUB>), general color quality scale (Q<SUB>a</SUB>), fidelity index (R<SUB>f</SUB>), and color gamut (R<SUB>g</SUB>) will be examined and compared by root mean square (RMS) values. 2-phosphor combination with a blue LED resulted in R<SUB>a</SUB>≥95, R<SUB>1∼14</SUB>≥75, and Q<SUB>a</SUB>≥90, 3-phosphor in R<SUB>a</SUB>≥98, R<SUB>1∼14</SUB>≥75, and Q<SUB>a</SUB>≥97, and 4-phosphor in R<SUB>a</SUB>≥94, R<SUB>1∼14</SUB>≥71, and Q<SUB>a</SUB>≥90.
Multi-chip LED의 RBG 색상 변화에 따른 LED조명의 CRI, CCT 변화 연구
조형섭(Hyeong-Seob Jo),류우찬(Uh-Chan Ryu) 한국조명·전기설비학회 2016 조명·전기설비학회논문지 Vol.30 No.12
Recent studies have been made to develope various methods for improving color rendering property of multi-chip LEDs, due to their variety of colors and color temperatures. It is well known that RGB multi-chip LEDs have different color rendering indices according to the correlated color temperatures and barely have a CRI above 90. In the paper, we reviewed the CRI variations with the changing the peak wavelengths of commercially available RGB LEDs in the previous papers and standards. And varying the spectral bandwidths of the RGB LEDs, CRI higher than 90 can be accomplished in the CCT ranging from 2000K to 6000K. The possibility of a CRI higher than 95 was proposed by controlling the spectral characteristics.
RGBY 멀티칩 LED의 스펙트럼 변화에 따른 광학 특성 변화 연구
조형섭(Hyeong-Seob Jo),류우찬(Uh-Chan Ryu) 한국조명·전기설비학회 2017 조명·전기설비학회논문지 Vol.31 No.2
Recently, various multi-chip LEDs have been developed as the efficiency of red, green, and blue LED chips is improved. RGBY multi-chip LEDs have a high color rendering index, but there is no research on the change of optical characteristics according to the peak wavelength, peak power and bandwidth of the spectrum. In this study, the spectra of commercially available RGBY LEDs are approximated by the Gaussian model and the effect of the spectral variations of red, green, blue and yellow regions on the color rendering indices was examined. CCT and CRI changes due to peak wavelength shift and change in full width at half maximum (FWHM) were simulated and a CRI higher than 98 at 2500 K to 6000 K color temperature range was resulted.
CCT 조절형 백색 LED와 단일 파장 LED의 스펙트럼 조합에 따른 S/P Ratio와 CRI 변화에 대한 전산모사 연구
김종오(Jong-Oh Kim),조형섭(Hyeong-Seob Jo),류우찬(Uh-Chan Ryu) 한국조명·전기설비학회 2019 조명·전기설비학회논문지 Vol.33 No.1
Human eyes are adopted to the mesophic vision in accordance with luminance levels from artificial lightings which are estimated by the corresponding parameter of S/P ratio. And another parameter to measure a visibility at night is color rendering index (CRI). Nonetheless, there have been rare reports on improving simultaneously S/P raio and CRI for white LED lightings, to the best knowledge of the authors. In this paper, variations of S/P ratio and CRI will be investigated by simulation for a correlated color temepature (CCT) tunable LED lighting, composed of warm white (WW) and cool white (CW) LEDs, along with a single LED spectrum to increase CRI of the lighting. Based on these results, the CRI is over 75 and the S/P ratio is 0.19∼0.56 better than 1.39 for WW-LED and 0.16∼0.36 better than 2.04 for CW-LED.