Results 1 - 10 of 35729
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[en] We demonstrate that a surface-emitting hybrid light source can be realized by a combination of organic and inorganic light-emitting devices (LEDs). To this end, a blue inorganic LED bar is deployed at one side of a transparent light guide plate (LGP), and a yellow organic LED (OLED) is in contact with the rear surface of the LGP. In such a configuration, it is found that the overall luminance is almost equivalent to the sum of the luminances measured from each light source, and the overall luminance uniformity is determined mainly by the luminance uniformity of the OLED panel at high luminances. We have achieved a white color showing the Commission Internationale d'Eclairage (CIE) chromaticity coordinates of (x = 0.34, y = 0.33), the power efficiency of 9.3 lm/W, the luminance uniformity of 63% at the luminance of 3100 cd m–2, the color rendering index as high as 89.3, and the correlated color temperature finely tunable within the range between 3000 and 8000 K. Such a system facilitates color tuning by adjusting their luminous intensities and hence the implementation of the emotional lighting system. (paper)
[en] Artificial light sources play an indispensable role in the daily life of any human being. This paper provides an overview of the present state of research in the science and technology of light sources. The paper includes a brief historical overview and a discussion of the properties that determine the performance of light sources. Existing technologies and future challenges for the lighting industry are presented in the domains of both electrical discharge lamps and solid-state light sources. Finally, the paper emphasizes the importance of taking a holistic view of the development of lighting systems in order to obtain high quality lighting that is needed for ensuring quality of life, health and security of end-users. (topical review)
[en] The mains characteristics of LED output lighting are high efficiency, long lifetime and the ability of low level voltage operation, making it suitable for working with photovoltaic panels. In the beginning this application was constrained to isolated and disaster areas where there are not possibilities of connection with the electric grid, this situation is changing as a consequence of the systematic price reduction in photovoltaic panels and LEDs and the increasing of the efficiency of this light source, therefore this option has become attractive in lighting projects of new facilities. It is important to know that in our country we have the means for the design and manufacturing of the elements of the lighting system and for making the lighting project, assuring a high level of national production integration. In this work the factors that make possible the feasibility of this type of illumination are analyzed and several options for its implementation are proposed. (author)
[en] This publication reports a study of the relationship between public lighting and biodiversity. It outlines what is at stake for biodiversity (a biodiversity under increasing pressure, legal framework of biodiversity protection), and discusses the definitions, evolutions and challenges of outer lighting (technical aspects and values, lamps characteristics, elements to be considered when selecting a lighting system, technological evolutions, costs, notions of light pollution, legal framework and standards). The next chapter describes and outlines the strong relationship between light and life: light as a factor of biological synchronisation, varying perception of light by the different species. The third chapter proposes an overview of knowledge on the relationship between artificial light and species (fishes, shellfishes, insects, amphibians, reptiles, birds and mammals) and a synthesis of disturbing effects of lighting on biodiversity. Some recommendations are made, notably for lamps and spectral distributions. Available contracts and public subsidies to renew public lighting networks, or to deal with the addressed issues are overviewed
[en] This paper was about a reliable research on high-power LED lighting. Based on the samples of the self-developed high-power LED streetlights, an electrical stress ageing test was carried out and thermocouple method was used in the temperature test. The ageing test showed that the initial flux reduction was mainly due to the absorption of the light lamp or the block by some parts of the lighting. And the late light decling was mainly caused by the decay of the high-power LED light source itself. Some suggestions on improving the design of streetlights will be given according to my research.
[en] Non-destructive technique based on visible (VIS) spectroscopy using light emitting diode (LED) as lighting was used for evaluation of the internal quality of mango fruit. The objective of this study was to investigate feasibility of white LED as lighting in spectroscopic instrumentation to predict the acidity and soluble solids content of intact Sala Mango. The reflectance spectra of the mango samples were obtained and measured in the visible range (400–700 nm) using VIS spectroscopy illuminated under different white LEDs and tungsten-halogen lamp (pro lamp). Regression models were developed by multiple linear regression to establish the relationship between spectra and internal quality. Direct calibration transfer procedure was then applied between master and slave lighting to check on the acidity prediction results after transfer. Determination of mango acidity under white LED lighting was successfully performed through VIS spectroscopy using multiple linear regression but otherwise for soluble solids content. Satisfactory results were obtained for calibration transfer between LEDs with different correlated colour temperature indicated this technique was successfully used in spectroscopy measurement between two similar light sources in prediction of internal quality of mango.
[en] We present a new algorithm to calculate the near-field distribution of scattered light of multiple nanospheres based on recursive order-of-scattering (OS) and the matrix inversion approaches, which avoids the divergent problem encountered in origin OS method at the resonance condition. Using this method, we investigate the light-transport properties of linear chains of Ag nanospheres. We found a maximum 3 dB damping length of 1.4 μm of the light propagation when the first sphere of the linear Ag spheres with the radius R=25 nm was illuminated. The optimal configurations that favor the photon energy transport are investigated as well
[en] In this work, the authors present the necessity of photometric measurements in order to determine quality parameters when changing light sources with other types of light sources. To emphasize this we conducted a case study, measuring luminous parameters on two different streets, and we determined the technical luminous coefficients that establish the lighting system quality. We made photometric measurements on a street with sodium vapours lamps and on a street with LED lamps, determined the technical light parameters and did a comparison of the results. The outcome of the case study underline the need of conducting photometric measurements and of the lighting system redesign such that, upon changing the light sources and the technical characteristics of the lighting systems, the system still fulfils the technical standards requirements. In conclusion, for each space that is to be illuminated, an optimal solution should be found, which ensures both a reduction of the energy consumptions (reducing the system’s costs) and meets the technical lighting requirements. (paper)
[en] Incandescent lamps, simple artifacts with radiation spectrum very similar to a black-body emitter, are traditional standards in photometry. Nowadays LEDs are broadly used in lighting, with great variety of spectra, and it is convenient to use standards for photometry with spectral distribution similar to that of the measured artifact. Research and development of such standards occur in several National Metrology Institutes. In Brazil, Inmetro is working on a practical solution for providing a LED based standard to be used for luminous flux measurements in the field of general lighting. This paper shows the measurements made for the developing of a prototype, that in sequence will be characterized in photometric quantities. (paper)
[en] Highlights: • Proper design of efficient lighting systems. • The reliability and durability of the light sources. • Maintenance of lighting systems. • Quality standards of LED lamps. • Optimum economic choice of light sources. - Abstract: The performance of lighting system must be calculated in order to determine the energy requirements of the building. In the normative [EN 12464-1] are established lighting requirements which have effects on energy needs. The European standard [EN 15193] provides guidance on that evaluation. The easiest way to comply with reduction of energy requirements leads to the replacement of traditional lamps with LED ones, but if we calculate also the reliability parameters, the economic return is not guaranteed. Using bibliographic data, we have compared lighting’s results for a museum (LED lamps versus CFL and halogen lamps). The objective function of the study is to optimize the energy consumption of lighting systems, but at the same time to assess the reliability (MTTF of the lamps) of these systems. Without accurate information about this last parameters, the right choice of the lamps cannot be done successfully