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[IEEE 2018 VII. Lighting Conference of the Visegrad Countries (Lumen V4) - Trebic, Czech Republic (2018.9.18-2018.9.20)] 2018 VII. Lighting Conference of the Visegrad Countries (Lumen V4) - The Uncertainty of Measurement of Spectroradiometric System with Double Monochromator
摘要： This article has task to inform a reader about uncertainties of measurement of spectroradiometric systems with double monochromator. Uncertainty of measurement is very important for all photometric measurements and calculations. Spectroradiometric system’s uncertainty is dependent on wavelength and is difficult to estimate uncertainty of measurement for photometric parameters calculated from measured spectrum. In the first part of this article there is theory necessary for understanding uncertainty analyses and description of construction of spectroradiometric system with double monochromator. In the second part there is practical uncertainty analysis of double monochromator in light laboratory and its results.
关键词： spectral irradiance,correlated color temperature,double monochromator,color rendering index,Uncertainty of measurement
更新于2025-09-23 15:21:21
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[IEEE 2019 IEEE Industry Applications Society Annual Meeting - Baltimore, MD, USA (2019.9.29-2019.10.3)] 2019 IEEE Industry Applications Society Annual Meeting - Study on the Influence of Various Factors on Measurement of CCT for a Controlled Lighting System
摘要： A microcontroller, an RGBC sensor and a commercially available programmable lighting section was designed as a building block for developing a more complex intelligent lighting system. Because measurement of the CCT can be affected by different errors, in this paper the main sources of error are identified and discussed. CCT calculation relationships based on the RGBC components given by the RGBC sensor, the influence of the illumination level, the influence of the sensor position and the influence of distance between sensor and lighting elements are identified as the main error sources and considerations regarding their decreasing are given.
关键词： lighting control,correlated color temperature,LED lamps
更新于2025-09-16 10:30:52
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Comfortable indoor lighting conditions for LEDlights evaluated from psychological and physiological responses
摘要： Comfortable light emitting diode (LED) lighting conditions were examined for psychological and physiological responses. Eight male and eight female subjects participated in a series of experiments. They were exposed to light emitted from LED lights of 3000 K in the ranges of 150–400 lux and 1500–5000 lux; 4000 K in the ranges of 140–640 lux and 2000–5000 lux; and 5000 K in the ranges of 70–270 lux and 2500–7000 lux. Illuminance at a given correlated color temperature was first maintained at the lowest value in the designated range and then increased in a stepwise manner. On reaching the highest value in the range, it was then decreased to the lowest value in a stepwise manner. The subjects were required to indicate their perception of brightness, glare, and comfort at the controlled illuminance levels. Electrocardiogram and electroencephalogram data were monitored continuously throughout exposure. The results showed that the boundary illuminances estimated from psychological and physiological responses did not significantly differ between male and female subjects, but differed markedly from those of fluorescent lights tested in a previous study. The high boundaries of the LED lights were higher than those of the fluorescent lights. The low boundaries of the LED lights at 3000 K and 4000 K were higher than those of the fluorescent lights, but the boundaries at 5000 K were lower than those of the fluorescent lights. These differences may be due to differences in the spectral distribution and luminance for a given illuminance between LED and fluorescent lights.
关键词： Electroencephalogram,Heart rate variability,Light intensity,Correlated color temperature
更新于2025-09-12 10:27:22
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Performance Evaluation of Single-Junction Indoor Photovoltaic Devices for Different Absorber Bandgaps Under Spectrally Varying White Light-Emitting Diodes
摘要： In this article, we present a detailed theoretical study to predict performance characteristics of single-junction indoor photovoltaic (PV) devices operated under white light emitting diodes (LEDs) having different spectral characteristics. Efficiency limits of both ideal and practical PV converters have been evaluated considering illumination by commercially available white LEDs. The obtained results have been generalized for white LED sources having a wide range of correlated color temperatures (CCTs) and fraction of blue in their corresponding spectrum. Depending on bandgap of the absorber material, both positive and negative correlations are observed between photon conversion efficiency of PV devices and CCT values of the white LED sources. For material bandgaps of ～1.5 eV or lower, higher photon conversion efficiencies are obtained for warm glow white LEDs. On the contrary, white LEDs characterized to emit cool light are found to be more conducive for PV devices having absorber layer bandgaps of ～2 eV or higher. The observed characteristics have been explained in terms of linewidth of the main emission peak and relative intensity of blue emission peak of the irradiating white LED spectrum. Based on the analysis of photon yield, three distinct bandgap ranges of the PV absorber material have also been identified, each of which represents different dependence of PV device performances on the white LED spectral characteristics. These results in effect provide the necessary guidelines for designing homojunction, heterojunction, or tandem PV devices suitable for operation under different practical white LED sources.
关键词： red-green-blue (RGB) white light emitting diodes (LEDs),energy conversion efficiency,photon yield,Correlated color temperature,indoor photovoltaic (PV)
更新于2025-09-12 10:27:22
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Hue and warm-cool feeling as the visual resemblance criteria for iso-CCT judgment
摘要： The hue perception and ‘warm-cool’ feelings were investigated, in response to various lighting settings, following the adaptation to either 3500K or 5000K to compare which one—between conventional iso-Correlated Color Temperature (CCT) and a new one based on CIE u'v0 color space—is more compatible with the visual perception. Twenty participants evaluated hue and warm-cool feelings for 48 test lighting settings, by observing an empty gray booth. The results showed that yellow-blue and ‘warm-cool’ feelings are closely located around the Planckian locus, while red-green roughly follows the line orthogonal to the Planckian locus in CIE u'v0 color space, at both 3500 K and 5000 K settings. This suggests that u'v0 color space correlates better with human perception.
关键词： correlated color temperature,color appearance,chromatic adaptation,color emotion
更新于2025-09-10 09:29:36
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Optical and structural properties of Curcuminoids Extracted from Curcuma longa L. for hybrid white light diode
摘要： In this study, curcuminoids were extracted from turmeric (Curcuma longa L.) by means of three methods, comprising the normal method, use of Soxhlet apparatus and by combining the normal method with the Soxhlet extraction approach. The limitation of stickiness in the use of curcuminoids was resolved by mixing it with silica gel. The curcuminoids used light down-conversion of UV light (390 nm) for the white light-emitting diode (WLED). The characteristics of the white light chromaticity were controlled by changing the current and concentration of the curcuminoids. The chromaticity coordinates (CIE) and correlated color temperature (CCT) were measured for different applied currents (20, 60 and 100 mA) and weights (25, 35 and 50 mg) of curcuminoids. It was observed from the concentration of phosphor that the combination of the normal and Soxhlet apparatus methods is most effective extraction approach. The results showed that increasing the concentration of phosphor signi?cantly and remarkably increased the value of CCT when different values of current were applied. The stress test showed that the prolongation of dye degradation can be improved using air gap and glass slid, with air gap being more effective. An optimum color rendering index (CRI) value of 61.2 is obtained. The white phosphor exhibited CIE values of 0.333, 0.3151 and color temperature (CCT) of 5405 K.
关键词： white light-emitting diode,turmeric,curcuminoids,correlated color temperature,chromaticity coordinates
更新于2025-09-10 09:29:36