WorldWideScience

Sample records for white led lighting

  1. Studying Light Color using White LED Lighting

    Science.gov (United States)

    Yamagishi, Misako; Yamaba, Kazuo; Nagata, Manori; Kubo, Chiho; Nokura, Kunihiro

    Recently, white Light Emitting Diodes (LEDs) are receiving attention worldwide as new lighting devices. This study examined effects of a lighting application on performance using white LEDs. The light color—the correlated color temperature (CCT) —was assessed. It affected to psychological states and physiological conditions. Three CCT conditions were respectively set for the experiment: 2500 K, 5000 K, and 8200 K. In all, 20 younger subjects (20-30 years old), 15 middle-aged to elderly subjects (45-60 years old) and 12 elderly subjects (over 65 years-old) participated. They were presented a Numerical Verification (NV) task for performance measurement. The psychological states on performance were evaluated using the lighting assessment questionnaire. The physiological conditions were recorded using an electrocardiograph. Results show that the effects of CCT differ among age groups. Especially, the performance of younger subjects might differ from CCT conditions; elderly subjects are affected by CCT condition because of their visual acuity or response to contrast of objects.

  2. White LED visible light communication technology research

    Science.gov (United States)

    Yang, Chao

    2017-03-01

    Visible light communication is a new type of wireless optical communication technology. White LED to the success of development, the LED lighting technology is facing a new revolution. Because the LED has high sensitivity, modulation, the advantages of good performance, large transmission power, can make it in light transmission light signal at the same time. Use white LED light-emitting characteristics, on the modulation signals to the visible light transmission, can constitute a LED visible light communication system. We built a small visible optical communication system. The system composition and structure has certain value in the field of practical application, and we also research the key technology of transmitters and receivers, the key problem has been resolved. By studying on the optical and LED the characteristics of a high speed modulation driving circuit and a high sensitive receiving circuit was designed. And information transmission through the single chip microcomputer test, a preliminary verification has realized the data transmission function.

  3. Warm white LEDs lighting over Ra=95 and its applications

    Science.gov (United States)

    Kobashi, Katsuya; Taguchi, Tsunemasa

    2007-02-01

    We have for the first time developed warm white LEDs lighting using a combination of near ultraviolet LED and three-band (red, green and blue) white phosphors. This LED has the average color-rendering index Ra=96. Moreover, special color-rendering index R9 (red) and R15 (face color of Japanese) are estimated to be 95 and 97, respectively. We will describe the results of evaluation on the medical lighting applications such as operation, treatment and endoscope experiments, application to the LED fashions and application to the Japanese antique art (ink painting) lighting.

  4. White LEDs and modules in chip-on-board technology for general lighting

    Science.gov (United States)

    Hartmann, Paul; Wenzl, Franz P.; Sommer, Christian; Pachler, Peter; Hoschopf, Hans; Schweighart, Marko; Hartmann, Martin; Kuna, Ladislav; Jakopic, Georg; Leising, Guenther; Tasch, Stefan

    2006-08-01

    At present, light-emitting diode (LED) modules in various shapes are developed and designed for the general lighting, advertisement, emergency lighting, design and architectural markets. To compete with and to surpass the performance of traditional lighting systems, enhancement of Lumen output and the white light quality as well as the thermal management and the luminary integration are key factors for success. Regarding these issues, white LEDs based on the chip-on-board (COB) technology show pronounced advantages. State-of-the-art LEDs exploiting this technology are now ready to enter the general lighting segments. We introduce and discuss the specific properties of the Tridonic COB technology dedicated for general lighting. This technology, in combination with a comprehensive set of tools to improve and to enhance the Lumen output and the white light quality, including optical simulation, is the scaffolding for the application of white LEDs in emerging areas, for which an outlook will be given.

  5. White light-emitting diodes (LEDs) using (oxy)nitride phosphors

    International Nuclear Information System (INIS)

    Xie, R-J; Hirosaki, N; Sakuma, K; Kimura, N

    2008-01-01

    (Oxy)nitride phosphors have attracted great attention recently because they are promising luminescent materials for phosphor-converted white light-emitting diodes (LEDs). This paper reports the luminescent properties of (oxy)nitride phosphors in the system of M-Si-Al-O-N (M = Li, Ca or Sr), and optical properties of white LEDs using a GaN-based blue LED and (oxy)nitride phosphors. The phosphors show high conversion efficiency of blue light, suitable emission colours and small thermal quenching. The bichromatic white LEDs exhibit high luminous efficacy (∼55 lm W -1 ) and the multi-phosphor converted white LEDs show high colour rendering index (Ra 82-95). The results indicate that (oxy)nitride phosphors demonstrate their superior suitability to use as down-conversion luminescent materials in white LEDs

  6. Newly patented process enables low-cost solution for increasing white light spectrum of LEDs

    Science.gov (United States)

    Spanard, Jan-Marie

    2017-10-01

    A newly patented process for completing the spectral light array emitted by LED bulbs provides a low-cost method for producing better human centered lighting (HCL). This process uses non-luminescent colorant filters, filling out the jagged LED spectral emission into a full, white light array. While LED bulbs have the distinct economic advantages of using less energy, producing less heat and lasting years longer than traditional incandescent bulbs, the persistent metameric failure of LED bulbs has resulted in slower, and sometimes reluctant, adoption of LED lighting by the residential, retail and architectural markets. Adding missing wavelengths to LED generated bulbs via colorant filters increases the aesthetic appeal of the light by decreasing current levels of metameric failure, reducing the `flatness', `harshness', and `dullness' of LED generated light reported by consumers. LED phosphor-converted light can be successfully tuned to "whiter" white light with selective color filtering using permanent, durable transparent pigments. These transparent pigments are selectively applied in combination with existing manufacturing technologies and utilized as a final color-tuning step in bulb design. The quantity of emitted light chosen for color filtering can be adjusted from 1% to 100% of emitted light, creating a custom balance of light quantity with light quality. This invention recognizes that "better light" is frequently chosen over "more light" in the consumer marketplace.

  7. Color Degradation of Textiles with Natural Dyes and of Blue Scale Standards Exposed to White LED Lamps:Evaluation of White LED Lamps for Effectiveness as Museum Lighting

    Science.gov (United States)

    Ishii, Mie; Moriyama, Takayoshi; Toda, Masahiro; Kohmoto, Kohtaro; Saito, Masako

    White light-emitting diodes (LED) are well suited for museum lighting because they emit neither UV nor IR radiation, which damage artifacts. The color degradation of natural dyes and blue scale standards (JIS L 0841) by white LED lamps are examined, and the performance of white LED lamps for museum lighting is evaluated. Blue scale standard grades 1-6 and silk fabrics dyed with 22 types of natural dyes classified as mid to highly responsive in a CIE technical report (CIE157:2004) were exposed to five types of white LED lamps using different luminescence methods and color temperatures. Color changes were measured at each 15000 lx·hr (500 lx at fabric surface × 300 hr) interval ten times. The accumulated exposure totaled 150000 lx·hr. The data on conventional white LED lamps and previously reported white fluorescent (W) and museum fluorescent (NU) lamps was evaluated. All the white LED lamps showed lower fading rates compared with a W lamp on a blue scale grade 1. The fading rate of natural dyes in total was the same between an NU lamp (3000 K) and a white LED lamp (2869 K). However, yellow natural dyes showed higher fading rates with the white LED lamp. This tendency is due to the high power characteristic of the LED lamp around 400-500 nm, which possibly contributes to the photo-fading action on the dyes. The most faded yellow dyes were Ukon (Curcuma longa L.) and Kihada (Phellodendron amurense Rupr.), and these are frequently used in historic artifacts such as kimono, wood-block prints, and scrolls. From a conservation point of view, we need to continue research on white LED lamps for use in museum lighting.

  8. Development of Key Technologies for White Lighting Based on Light-Emitting Diodes (LEDs)

    Energy Technology Data Exchange (ETDEWEB)

    Werner Goetz; Bill Imler; James Kim; Junko Kobayashi; Andrew Kim; Mike Krames; Rick Mann; Gerd Mueller-Mach; Anneli Munkholm; Jonathan Wierer

    2004-03-31

    This program was organized to focus on materials development issues critical to the acceleration of solid-state lighting, and was split into three major thrust areas: (1) study of dislocation density reduction for GaN grown on sapphire using 'cantilever epitaxy', and the impact of dislocation density on the performance of state-of-the-art high-power LEDs; (2) the evaluation of in situ techniques for monitoring gas phase chemistry and the properties of GaN-based layers during metal-organic vapor phase epitaxy (MOCVD), and (3) feasibility for using semiconductor nanoparticles ('quantum dots') for the down-conversion of blue or ultraviolet light to generate white light. The program included a partnership between Lumileds Lighting (epitaxy and device fabrication for high power LEDs) and Sandia National Laboratories (cantilever epitaxy, gas phase chemistry, and quantum dot synthesis). Key findings included: (1) cantilever epitaxy can provide dislocation density reduction comparable to that of more complicated approaches, but all in one epitaxial growth step; however, further improvements are required to realize significant gains in LED performance at high drive currents, (2) in situ tools can provide detailed knowledge about gas phase chemistry, and can be used to monitor and control epitaxial layer composition and temperature to provide improved yields (e.g., a fivefold increase in color targeting is demonstrated for 540nm LEDs), and (3) quantum efficiency for quantum dots is improved and maintained up to 70% in epoxy thin films, but further work is necessary to increase densification (absorption) and robustness before practical application to LEDs.

  9. Color design model of high color rendering index white-light LED module.

    Science.gov (United States)

    Ying, Shang-Ping; Fu, Han-Kuei; Hsieh, Hsin-Hsin; Hsieh, Kun-Yang

    2017-05-10

    The traditional white-light light-emitting diode (LED) is packaged with a single chip and a single phosphor but has a poor color rendering index (CRI). The next-generation package comprises two chips and a single phosphor, has a high CRI, and retains high luminous efficacy. This study employs two chips and two phosphors to improve the diode's color tunability with various proportions of two phosphors and various densities of phosphor in the silicone used. A color design model is established for color fine-tuning of the white-light LED module. The maximum difference between the measured and color-design-model simulated CIE 1931 color coordinates is approximately 0.0063 around a correlated color temperature (CCT) of 2500 K. This study provides a rapid method to obtain the color fine-tuning of a white-light LED module with a high CRI and luminous efficacy.

  10. Thermal, optical, and electrical engineering of an innovative tunable white LED light engine

    Science.gov (United States)

    Trivellin, Nicola; Meneghini, Matteo; Ferretti, Marco; Barbisan, Diego; Dal Lago, Matteo; Meneghesso, Gaudenzio; Zanoni, Enrico

    2014-02-01

    Color temperature, intensity and blue spectrum of the light affects the ganglion receptors in human brain stimulating the human nervous system. With this work we review different methods for obtaining tunable light emission spectra and propose an innovative white LED lighting system. By an in depth study of the thermal, electrical and optical characteristics of GaN and GaP based compound semiconductors for optoelectronics a specific tunable spectra has been designed. The proposed tunable white LED system is able to achieve high CRI (above 95) in a large CCT range (3000 - 5000K).

  11. Wireless high-speed data transmission with phosphorescent white-light LEDs

    NARCIS (Netherlands)

    Grubor, J.; Lee, S.C.J.; Langer, K-D.; Koonen, A.M.J.; Walewski, J.

    2007-01-01

    Wireless transmission exceeding 100 Mbit/s is demonstrated using a phosphorescent white-light LED in a lighting-like scenario. The data rate was achieved by detecting the blue part of the optical spectrum and applying discrete multi-tone modulation.

  12. Imaging camera system of OYGBR-phosphor-based white LED lighting

    Science.gov (United States)

    Kobashi, Katsuya; Taguchi, Tsunemasa

    2005-03-01

    The near-ultraviolet (nUV) white LED approach is analogous to three-color fluorescent lamp technology, which is based on the conversion of nUV radiation to visible light via the photoluminescence process in phosphor materials. The nUV light is not included in the white light generation from nUV-based white LED devices. This technology can thus provide a higher quality of white light than the blue and YAG method. A typical device demonstrates white luminescence with Tc=3,700 K, Ra > 93, K > 40 lm/W and chromaticity (x, y) = (0.39, 0.39), respectively. The orange, yellow, green and blue OYGB) or orange, yellow, red, green and blue (OYRGB) device shows a luminescence spectrum broader than of an RGB white LED and a better color rendering index. Such superior luminous characteristics could be useful for the application of several kinds of endoscope. We have shown the excellent pictures of digestive organs in a stomach of a dog due to the strong green component and high Ra.

  13. Development of Advanced Manufacturing Methods for Warm White LEDs for General Lighting

    Energy Technology Data Exchange (ETDEWEB)

    Deshpande, Anirudha; Kolodin, Boris; Jacob, Cherian; Chowdhury, Ashfaqul; Kuenzler, Glenn; Sater, Karen; Aesram, Danny; Glaettli, Steven; Gallagher, Brian; Langer, Paul; Setlur, Anant; Beers, Bill

    2012-03-31

    GE Lighting Solutions will develop precise and efficient manufacturing techniques for the “remote phosphor” platform of warm-white LED products. In volume, this will be demonstrated to drive significant materials, labor and capital productivity to achieve a maximum possible 53% reduction in overall cost. In addition, the typical total color variation for these white LEDs in production will be well within the ANSI bins and as low as a 4-step MacAdam ellipse centered on the black body curve. Achievement of both of these objectives will be demonstrated while meeting a performance target of > 75 lm/W for a warm-white LED and a reliability target of <30% lumen drop / <2-step MacAdam ellipse shift, estimated over 50,000 hrs.

  14. Study and Implementation of White Power-LED Based Indoor Lighting Application for the Healthcare Sector

    Science.gov (United States)

    Chakraborty, A.; Ganguly, R.

    With the current technological growth in the field of device fabrication, white power-LED's are available for solid state lighting applications. This is a paradigm shift from electrical lighting to electronic lighting. The implemented systems are showing some promise by saving a considerable amount of energy as well as providing a good and acceptable illumination level. However, the `useful life' of such devices is an important parameter. If the proper device is not chosen, the desired reliability and performance will not be obtained. In the present work, different parameters associated with reliability of such LED's are studied. Four different varieties of LED's are put to test the `useful life' as per IESNA LM 79 standard. From the results obtained, the proper LED is chosen for further application. Subsequently, lighting design is done for a hospital waiting room (indoor application) with 24 × 7 lighting requirements for replacement of existing CFLs there. The calculations show that although the initial cost is higher for LED based lighting, yet the savings on energy and replacement of the lamp results in a payback time of less than a year.

  15. Multispectral digital lensless holographic microscopy: from femtosecond laser to white light LED

    International Nuclear Information System (INIS)

    Garcia-Sucerquia, J

    2015-01-01

    The use of femtosecond laser radiation and super bright white LED in digital lensless holographic microscopy is presented. For the ultrafast laser radiation two different configurations of operation of the microscope are presented and the dissimilar performance of each one analyzed. The microscope operating with a super bright white light LED in combination with optical filters shows very competitive performance as it is compared with more expensive optical sources. The broadband emission of both radiation sources allows the multispectral imaging of biological samples to obtain spectral responses and/or full color images of the microscopic specimens; sections of the head of a Drosophila melanogaster fly are imaged in this contribution. The simple, solid, compact, lightweight, and reliable architecture of digital lensless holographic microscopy operating with broadband light sources to image biological specimens exhibiting micrometer-sized details is evaluated in the present contribution. (paper)

  16. The Concept of Fashion Design on the Basis of Color Coordination Using White LED Lighting

    Science.gov (United States)

    Mizutani, Yumiko; Taguchi, Tsunemasa

    This thesis focuses on the development of fashion design, especially a dress coordinated with White LED Lighting (=LED). As for the design concept a fusion of the advanced science and local culture was aimed for. For such a reason this development is a very experimental one. Here in particular I handled an Imperial Court dinner dress for the last Japanese First Lady, Mrs. Akie Abe who wore it at the Imperial Court dinner for the Indonesian First Couple held on November 2006 to. This dress made by Prof. T. Taguchi and I open up a new field in the dress design.

  17. Output blue light evaluation for phosphor based smart white LED wafer level packages.

    Science.gov (United States)

    Kolahdouz, Zahra; Rostamian, Ali; Kolahdouz, Mohammadreza; Ma, Teng; van Zeijl, Henk; Zhang, Kouchi

    2016-02-22

    This study presents a blue light detector for evaluating the output light of phosphor based white LED package. It is composed of a silicon stripe-shaped photodiode designed and implemented in a 2 μm BiCMOS process which can be used for wafer level integration of different passive and active devices all in just 5 lithography steps. The final device shows a high selectivity to blue light. The maximum responsivity at 480 nm is matched with the target blue LED illumination. The designed structure have better responsivity compared to simple photodiode structure due to reducing the effect of dead layer formation close to the surface because of implantation. It has also a two-fold increase in the responsivity and quantum efficiency compared to previously similar published sensors.

  18. Progress in characterizing the multidimensional color quality properties of white LED light sources

    Science.gov (United States)

    Teunissen, Kees; Hoelen, Christoph

    2016-03-01

    With the introduction of solid state light sources, the variety in emission spectra is almost unlimited. However, the set of standardized parameters to characterize a white LED light source, such as correlated color temperature (CCT) and CIE general color rendering index (Ra), is known to be limited and insufficient for describing perceived differences between light sources. Several characterization methods have been proposed over the past decades, but their contribution to perceived color quality has not always been validated. To gain more insight in the relevant characteristics of the emission spectra for specific applications, we have conducted a perception experiment to rate the attractiveness of three sets of objects, including fresh food, packaging materials and skin tones. The objects were illuminated with seven different combinations of Red, Green, Blue, Amber and White LEDs, all with the same CCT and illumination level, but with differences in Ra and color saturation. The results show that, in general, object attractiveness does not correlate well with Ra, but shows a positive correlation with saturation increase for two out of three applications. There is no clear relation between saturation and skin tone attractiveness, partly due to differences in preference between males and females. A relative gamut area index (Ga) represents the average change in saturation and a complementary color vector graphic shows the direction and magnitude of chromatic differences for the eight CIE-1974 test-color samples. Together with the CIE general color rendering index (Ra) they provide useful information for designing and optimizing application specific emission spectra.

  19. Phosphors for near UV-Emitting LED's for Efficacious Generation of White Light

    Energy Technology Data Exchange (ETDEWEB)

    McKittrick, Joanna [Univ. of California, San Diego, CA (United States)

    2013-09-30

    1) We studied phosphors for near-UV (nUV) LED application as an alternative to blue LEDs currently being used in SSL systems. We have shown that nUV light sources could be very efficient at high current and will have significantly less binning at both the chip and phosphor levels. We identified phosphor blends that could yield 4100K lamps with a CRI of approximately 80 and LPWnUV,opt equal to 179 for the best performing phosphor blend. Considering the fact that the lamps were not optimized for light coupling, the results are quite impressive. The main bottleneck is an optimum blue phosphor with a peak near 440 nm with a full width half maximum of about 25 nm and a quantum efficiency of >95%. Unfortunately, that may be a very difficult task when we want to excite a phosphor at ~400 nm with a very small margin for Stokes shift. Another way is to have all the phosphors in the blend having the excitation peak at 400 nm or slightly shorter wavelength. This could lead to a white light source with no body color and optimum efficacy due to no self-absorption effects by phosphors in the blend. This is even harder than finding an ideal blue phosphor, but not necessarily impossible. 2) With the phosphor blends identified, light sources using nUV LEDs at high current could be designed with comparable efficacy to those using blue LEDs. It will allow us to design light sources with multiple wattages using the same chips and phosphor blends simply by varying the input current. In the case of blue LEDs, this is not currently possible because varying the current will lower the efficacy at high current and alter the color point. With improvement of phosphor blends, control over CRI could improve. Less binning at the chip level and also at the phosphor blend level could reduce the cost of SSL light sources. 3) This study provided a deeper understanding of phosphor characteristics needed for LEDs in general and nUV LEDs in particular. Two students received Ph.D. degrees and three

  20. The High-Temperature Synthesis of the Nanoscaled White-Light Phosphors Applied in the White-Light LEDs

    Directory of Open Access Journals (Sweden)

    Hao-Ying Lu

    2015-01-01

    Full Text Available The white-light phosphors consisting of Dy3+ doped YPO4 and Dy3+ doped YP1-XVXO4 were prepared by the chemical coprecipitation method. After the 1200°C thermal treatment in the air atmosphere, the white-light phosphors with particle sizes around 90 nm can be obtained. In order to reduce the average particle size of phosphors, the alkaline washing method was applied to the original synthesis process, which reduces the particle sizes to 65 nm. From the PLE spectra, four absorption peaks locating at 325, 352, 366, and 390 nm can be observed in the YPO4-based phosphors. These peaks appear due to the following electron transitions: 6H15/2→4K15/2, 6H15/2→4M15/2+6P7/2, 6H15/2→4I11/2, and 6H15/2→4M19/2. Besides, the emission peaks of wavelengths 484 nm and 576 nm can be observed in the PL spectra. In order to obtain the white-light phosphors, the vanadium ions were applied to substitute the phosphorus ions to compose the YP1-XVXO4 phosphors. From the PL spectra, the strongest PL intensity can be obtained with 30% vanadium ions. As the concentration of vanadium ions increases to 40%, the phosphors with the CIE coordinates locating at the white-light area can be obtained.

  1. How to distinguish scattered and absorbed light from re-emitted light for white LEDs?

    NARCIS (Netherlands)

    Meretska, Maryna; Lagendijk, Aart; Thyrrestrup Nielsen, Henri; Mosk, Allard; IJzerman, Wilbert; Vos, Willem L.

    2017-01-01

    We have studied the light transport through phosphor diffuser plates that are used in commercial solid-state lighting modules (Fortimo). These polymer plates contain YAG:Ce+3 phosphor particles that scatter, absorb and re-emit incident light in the visible wavelength range (400-700 nm). To

  2. Ultrabroad linewidth orange-emitting nanowires LED for high CRI laser-based white lighting and gigahertz communications

    KAUST Repository

    Janjua, Bilal; Ng, Tien Khee; Zhao, Chao; Oubei, Hassan M.; Shen, Chao; Prabaswara, Aditya; Alias, Mohd Sharizal; Alhamoud, Abdullah Ali; Alatawi, Abdullah Awaad; Albadri, Abdulrahman M.; Alyamani, Ahmed Y.; El-Desouki, Munir M.; Ooi, Boon S.

    2016-01-01

    intensity- and bandwidth-tunable for high color-quality remained unexplored. In this paper, we present for the first time, the proof-of-concept of the generation of high-quality white light using an InGaN-based orange nanowires (NWs) LED grown on silicon

  3. Color point tuning for (Sr,Ca,Ba)Si2O2N2:Eu2+ for white light LEDs

    NARCIS (Netherlands)

    Bachmann, V.M.; Ronda, R.C.; Meijerink, A.; Oeckler, O.; Schnick, W.

    2009-01-01

    Color point tuning is an important challenge for improving white light LEDs. In this paper, the possibilities of color tuning with the efficient LED phosphor Sr1-x-y-zCaxBaySi2O2N2:Euz 2+ (0 e x, y e 1; 0.005 e z e 0.16) are investigated. The emission color can be tuned in two ways: by changing Eu2+

  4. Enhancement of Color Rendering Index for White Light LED Lamps by Red Y2O3:EU3+ Phosphor

    Directory of Open Access Journals (Sweden)

    Tran Hoang Quang Minh

    2016-01-01

    Full Text Available We present an application of the red Y2O3:Eu3+ dopant phosphor compound for reaching the color rendering index as high as 86. The Multi-Chip White LED lamps (MCW-LEDs with high Correlated Color Temperatures (CCTs including 7000 K and 8500 K are employed in this study. Besides, the impacts of the Y2O3:Eu3+ phosphor on the attenuation of light through phosphor layers of the various packages is also demonstrated based on the Beer-Lambert law. Simulation results provide important conclusion for selecting and developing the phosphor materials in MCW-LEDs manufacturing.

  5. Comparative Study of Lettuce and Radish Grown Under Red and Blue Light-Emitting Diodes (LEDs) and White Fluorescent Lamps

    Science.gov (United States)

    Mickens, Matthew A.

    2012-01-01

    Growing vegetable crops in space will be an essential part of sustaining astronauts during long-term missions. To drive photosynthesis, red and blue light-emitting diodes (LEDs) have attracted attention because of their efficiency, longevity, small size, and safety. In efforts to optimize crop production, there have also been recent interests in analyzing the subtle effects of green light on plant growth, and to determine if it serves as a source of growth enhancement or suppression. A comparative study was performed on two short cycle crops of lettuce (Outredgeous) and radish (Cherry Bomb) grown under two light treatments. The first treatment being red and blue LEDs, and the second treatment consisting of white fluorescent lamps which contain a portion of green light. In addition to comparing biomass production, physiological characterizations were conducted on how the light treatments influence morphology, water use, chlorophyll content, and the production of A TP within plant tissues.

  6. White emitting CdS quantum dot nanoluminophores hybridized on near-ultraviolet LEDs for high-quality white light generation and tuning

    International Nuclear Information System (INIS)

    Nizamoglu, Sedat; Mutlugun, Evren; Akyuz, Ozgun; Perkgoz, Nihan Kosku; Demir, Hilmi Volkan; Liebscher, Lydia; Sapra, Sameer; Gaponik, Nikolai; Eychmueller, Alexander

    2008-01-01

    To generate white light using semiconductor nanocrystal (NC) quantum dots integrated on light emitting diodes (LEDs), multiple hybrid device parameters (emission wavelengths of the NCs and the excitation platform, order of the NCs with different sizes, amount of the different types of NCs, etc) need to be carefully designed and properly implemented. In this study, we introduce and demonstrate white LEDs based on simple device hybridization using only a single type of white emitting CdS quantum dot nanoluminophores on near-ultraviolet LEDs. Here we present their design, synthesis-growth, fabrication and characterization. With these hybrid devices, we achieve high color rendering index (>70), despite using only a single NC type. Furthermore, we conveniently tune their photometric properties including the chromaticity coordinates, correlated color temperature, and color rendering index with the number of hybridized nanoluminophores in a controlled manner

  7. Ultrabroad linewidth orange-emitting nanowires LED for high CRI laser-based white lighting and gigahertz communications

    KAUST Repository

    Janjua, Bilal

    2016-08-10

    Group-III-nitride laser diode (LD)-based solid-state lighting device has been demonstrated to be droop-free compared to light-emitting diodes (LEDs), and highly energy-efficient compared to that of the traditional incandescent and fluorescent white light systems. The YAG:Ce3+ phosphor used in LD-based solid-state lighting, however, is associated with rapid degradation issue. An alternate phosphor/LD architecture, which is capable of sustaining high temperature, high power density, while still intensity- and bandwidth-tunable for high color-quality remained unexplored. In this paper, we present for the first time, the proof-of-concept of the generation of high-quality white light using an InGaN-based orange nanowires (NWs) LED grown on silicon, in conjunction with a blue LD, and in place of the compound-phosphor. By changing the relative intensities of the ultrabroad linewidth orange and narrow-linewidth blue components, our LED/LD device architecture achieved correlated color temperature (CCT) ranging from 3000 K to above 6000K with color rendering index (CRI) values reaching 83.1, a value unsurpassed by the YAG-phosphor/blue-LD counterpart. The white-light wireless communications was implemented using the blue LD through on-off keying (OOK) modulation to obtain a data rate of 1.06 Gbps. We therefore achieved the best of both worlds when orange-emitting NWs LED are utilized as “active-phosphor”, while blue LD is used for both color mixing and optical wireless communications.

  8. Multi-band transmission color filters for multi-color white LEDs based visible light communication

    Science.gov (United States)

    Wang, Qixia; Zhu, Zhendong; Gu, Huarong; Chen, Mengzhu; Tan, Qiaofeng

    2017-11-01

    Light-emitting diodes (LEDs) based visible light communication (VLC) can provide license-free bands, high data rates, and high security levels, which is a promising technique that will be extensively applied in future. Multi-band transmission color filters with enough peak transmittance and suitable bandwidth play a pivotal role for boosting signal-noise-ratio in VLC systems. In this paper, multi-band transmission color filters with bandwidth of dozens nanometers are designed by a simple analytical method. Experiment results of one-dimensional (1D) and two-dimensional (2D) tri-band color filters demonstrate the effectiveness of the multi-band transmission color filters and the corresponding analytical method.

  9. A long distance voice transmission system based on the white light LED

    Science.gov (United States)

    Tian, Chunyu; Wei, Chang; Wang, Yulian; Wang, Dachi; Yu, Benli; Xu, Feng

    2017-10-01

    A long distance voice transmission system based on a visible light communication technology (VLCT) is proposed in the paper. Our proposed system includes transmitter, receiver and the voice signal processing of single chip microcomputer. In the compact-sized LED transmitter, we use on-off-keying and not-return-to-zero (OOK-NRZ) to easily realize high speed modulation, and then systematic complexity is reduced. A voice transmission system, which possesses the properties of the low-noise and wide modulation band, is achieved by the design of high efficiency receiving optical path and using filters to reduce noise from the surrounding light. To improve the speed of the signal processing, we use single chip microcomputer to code and decode voice signal. Furthermore, serial peripheral interface (SPI) is adopted to accurately transmit voice signal data. The test results of our proposed system show that the transmission distance of this system is more than100 meters with the maximum data rate of 1.5 Mbit/s and a SNR of 30dB. This system has many advantages, such as simple construction, low cost and strong practicality. Therefore, it has extensive application prospect in the fields of the emergency communication and indoor wireless communication, etc.

  10. White LED with High Package Extraction Efficiency

    International Nuclear Information System (INIS)

    Yi Zheng; Stough, Matthew

    2008-01-01

    The goal of this project is to develop a high efficiency phosphor converting (white) Light Emitting Diode (pcLED) 1-Watt package through an increase in package extraction efficiency. A transparent/translucent monolithic phosphor is proposed to replace the powdered phosphor to reduce the scattering caused by phosphor particles. Additionally, a multi-layer thin film selectively reflecting filter is proposed between blue LED die and phosphor layer to recover inward yellow emission. At the end of the project we expect to recycle approximately 50% of the unrecovered backward light in current package construction, and develop a pcLED device with 80 lm/W e using our technology improvements and commercially available chip/package source. The success of the project will benefit luminous efficacy of white LEDs by increasing package extraction efficiency. In most phosphor-converting white LEDs, the white color is obtained by combining a blue LED die (or chip) with a powdered phosphor layer. The phosphor partially absorbs the blue light from the LED die and converts it into a broad green-yellow emission. The mixture of the transmitted blue light and green-yellow light emerging gives white light. There are two major drawbacks for current pcLEDs in terms of package extraction efficiency. The first is light scattering caused by phosphor particles. When the blue photons from the chip strike the phosphor particles, some blue light will be scattered by phosphor particles. Converted yellow emission photons are also scattered. A portion of scattered light is in the backward direction toward the die. The amount of this backward light varies and depends in part on the particle size of phosphors. The other drawback is that yellow emission from phosphor powders is isotropic. Although some backward light can be recovered by the reflector in current LED packages, there is still a portion of backward light that will be absorbed inside the package and further converted to heat. Heat generated

  11. [LED lights in dermatology].

    Science.gov (United States)

    Noé, C; Pelletier-Aouizerate, M; Cartier, H

    2017-04-01

    The use in dermatology of light-emitting diodes (LEDs) continues to be surrounded by controversy. This is due mainly to poor knowledge of the physicochemical phases of a wide range of devices that are difficult to compare to one another, and also to divergences between irrefutable published evidence either at the level of in vitro studies or at the cellular level, and discordant clinical results in a variety of different indications: rejuvenation, acne, wound healing, leg ulcers, and cutaneous inflammatory or autoimmune processes. Therapeutic LEDs can emit wavelengths ranging from the ultraviolet, through visible light, to the near infrared (247-1300 nm), but only certain bands have so far demonstrated any real value. We feel certain that if this article remains factual, then readers will have a different, or at least more nuanced, opinion concerning the use of such LED devices in dermatology. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

  12. ‘No Blue’ White LED

    DEFF Research Database (Denmark)

    Ou, Haiyan; Corell, Dennis Dan; Dam-Hansen, Carsten

    2010-01-01

    This paper explored the feasibility of making a white LED light source by color mixing method without using the blue color. This ‘no blue’ white LED has potential applications in photolithography room illumination, medical treatment and biophotonics research. A no-blue LED was designed......-2005. Even after 15 days of illumination, no effect was observed. So this LED-based solution was demonstrated to be a very promising light source for photolithography room illumination due to its better color rendering in addition to energy efficiency, long life time and design flexibility. Additionally......, and the prototype was fabricated. The spectral power distribution of both the LED bulb and the yellow fluorescent tube was measured. Based on that, colorimetric values were calculated and compared on terms of chromatic coordinates, correlated color temperature, color rendering index, and chromatic deviation...

  13. White LED motorcycle headlamp design

    Science.gov (United States)

    Sun, Wen-Shing

    2015-09-01

    The motorcycle headlamp is composed of a white LED module, an elliptical reflector, a parabolic reflector and a toric lens. We use non-sequential ray to improve the optical efficiency of the compound reflectors. Using the toric lens can meet ECE_113 regulation and obtain a good uniformity.

  14. White LEDs as broad spectrum light sources for spectrophotometry: demonstration in the visible spectrum range in a diode-array spectrophotometric detector.

    Science.gov (United States)

    Piasecki, Tomasz; Breadmore, Michael C; Macka, Mirek

    2010-11-01

    Although traditional lamps, such as deuterium lamps, are suitable for bench-top instrumentation, their compatibility with the requirements of modern miniaturized instrumentation is limited. This study investigates the option of utilizing solid-state light source technology, namely white LEDs, as a broad band spectrum source for spectrophotometry. Several white light LEDs of both RGB and white phosphorus have been characterized in terms of their emission spectra and energy output and a white phosphorus Luxeon LED was then chosen for demonstration as a light source for visible-spectrum spectrophotometry conducted in CE. The Luxeon LED was fixed onto the base of a dismounted deuterium (D(2) ) lamp so that the light-emitting spot was geometrically positioned exactly where the light-emitting spot of the original D(2) lamp is placed. In this manner, the detector of a commercial CE instrument equipped with a DAD was not modified in any way. As the detector hardware and electronics remained the same, the change of the deuterium lamp for the Luxeon white LED allowed a direct comparison of their performances. Several anionic dyes as model analytes with absorption maxima between 450 and 600 nm were separated by CE in an electrolyte of 0.01 mol/L sodium tetraborate. The absorbance baseline noise as the key parameter was 5 × lower for the white LED lamp, showing clearly superior performance to the deuterium lamp in the available, i.e. visible part of the spectrum. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. A new bismuth-based coordination polymer as an efficient visible light responding photocatalyst under white LED irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Ya-Jing; Zheng, Yue-Qing, E-mail: zhengyueqing@nbu.edu.cn; Wang, Jin-Jian; Zhou, Lin-Xia

    2017-02-15

    A new bismuth-based polymer, [Hbpe][Bi(Hpydc){sub 2}(pydc)]·H{sub 2}O (H{sub 2}pydc=pyridine-2,5-dicarboxylic acid, bpe=trans-bis(4-pyridyl) ethylene) has been hydrothermally synthesized. Transient photocurrent response and electrochemical impedance spectroscopy studies indicate that the synthesized polymer with efficient charge separation and transportation can be used as a potential photocatalyst. So we use it for the degradation of rhodamine B (RhB) dye wastewater under visible light. The comparative study on commercial Bi{sub 2}O{sub 3} shows [Hbpe][Bi(Hpydc){sub 2}(pydc)]·H{sub 2}O has the higher photocatalytic performance, with the degradation rate of 97% and 2% within 100 min for [Hbpe][Bi(Hpydc){sub 2}(pydc)]·H{sub 2}O and commercial Bi{sub 2}O{sub 3} respectively. Additionally, the five cycle reproducibility results of [Hbpe][Bi(Hpydc){sub 2}(pydc)]·H{sub 2}O implies that it can be used as a stable photocatalyst. - Graphical abstract: We report a new 1D coordination polymer [Hbpe][Bi(Hpydc){sub 2}(pydc)]·H{sub 2}O by a facile hydrothermal method. The Bi-CP shows good photoelectric property and photocatalytic activity for RhB degradation under visible white LED lamp irradiation. And the stability of the visible-light-responsive bismuth-based coordination polymer has also been examined. - Highlights: • A new Bi(III) coordination polymer is hydrothermally synthesized. • The Bi-CP shows good photoelectric and photocatalytic properties. • Bi-CP shows higher activity than the commercial Bi{sub 2}O{sub 3} for RhB degradation.

  16. 高显色指数LED合成白光光源的研究%Study on LEDs Synthesized High Color Rendering Index White Light Source

    Institute of Scientific and Technical Information of China (English)

    胡奕彬; 庄其仁; 刘士伟; 赖传杜

    2016-01-01

    针对目前白光发光二极管(LED)照明灯具显色性不高的问题,基于测色法研究了LED合成白光显色指数的计算模型,根据参与合成的LED光源光谱及其数量,软件编程计算得出合成光源的色温、显色指数等参数.采用优化的遍历范围,将实验测量得到的冷、暖白光及单色LED的光谱导入程序进行模拟计算,得到不同色温下合成光源的显色指数最大值以及所对应的各种LED配比数量.结果表明,暖白光LED与红、绿、蓝LED合成可以获得色温L介于3500 K~12300 K、显色指数见介于92.0~97.7的白光;与红、绿、青LED合成可以获得Ra介于95.0~97.8的低色温白光(3500 K~4500 K).冷白光LED与红、绿、青LED合成可以获得Ra介于90.9~98.4的高色温白光(8200 K~13000 K).对理论计算的Tc=7803 K、Ra=97.29的LED配比进行实际制作,实验测量得到Tc=7992 K,Ra=97.1,理论计算结果与实验结果吻合.%Targeting poor color rendering property of current white light-emitting diode (LED) lamps,based on the colorimetry method,the calculation model for color rendering index of synthetic white light is studied and the parameters like color temperature and color rendering index of the synthetic LED light source are obtained based on the spectrum and quantity of light sources involved in the synthesis process.By using optimized traversal range,the spectra of cold and warm white light and single-color LEDs are imported into the program for simulating calculation,obtaining the maximum value of color rendering index of the synthesized light source under different color temperatures as well as corresponding matched quantity of various LEDs.The results show that the synthesis with warm white LEDs and red,green and blue LEDs can lead to white light whose color temperature falls in the range of 3500 K~12300 K and color rendering index Ra ranges between 92.0 and 97.7.The synthesis with warm white LEDs and red,green and bluish

  17. EDITORIAL: LED light sources (light for the future) LED light sources (light for the future)

    Science.gov (United States)

    Grandjean, N.

    2010-09-01

    Generating white light from electricity with maximum efficacy has been a long quest since the first incandescent lamp was invented by Edison at the end of the 19th century. Nowadays, semiconductors are making reality the holy grail of converting electrons into photons with 100% efficiency and with colours that can be mixed for white light illumination. The revolution in solid-state lighting (SSL) dates to 1994 when Nakamura reported the first high-brightness blue LED based on GaN semiconductors. Then, white light was produced by simply combining a blue dye with a yellow phosphor. After more than a decade of intensive research the performance of white LEDs is quite impressive, beating by far the luminous efficacy of compact fluorescent lamps. We are likely close to replacing our current lighting devices by SSL lamps. However, there are still technological and fabrication cost issues that could delay large market penetration of white LEDs. Interestingly, SSL may create novel ways of using light that could potentially limit electricity saving. Whatever the impact of SSL, it will be significant on our daily life. The purpose of this special cluster issue is to produce a snapshot of the current situation of SSL from different viewing angles. In an introductory paper, Tsao and co-workers from Sandia National Laboratories, present an energy-economics perspective of SSL considering societal changes and SSL technology evolution. In a second article, Narukawa et al working at Nichia Corporation—the pioneer and still the leading company in SSL—describe the state of the art of current research products. They demonstrate record performance with white LEDs exhibiting luminous efficacy of 183 lm W-1 at high-current injection. Then, a series of topical papers discuss in detail various aspects of the physics and technology of white LEDs Carrier localization in InGaN quantum wells has been considered the key to white LEDs' success despite the huge density of defects. A

  18. Tuning the color point of a white LED

    NARCIS (Netherlands)

    Adhikary, Manashee; Meretska, Maryna; Ladovrechis, K.; Fokkema, Wouter K.; Vissenberg, Gilles; Lagendijk, Ad; Ijzerman, W.L.; Vos, Willem L.

    2018-01-01

    White light is conveniently characterized by a color point that is represented on the color space. Color point of white LED is fixed by the design parameters (e.g. Phosphor type and concentration). When the design parameters are chosen, the color point of the white LED cannot be changed. Here, we

  19. White LEDs with limit luminous efficacy

    Energy Technology Data Exchange (ETDEWEB)

    Lisitsyn, V. M.; Stepanov, S. A., E-mail: stepanovsa@tpu.ru; Yangyang, Ju [National Research Tomsk Polytechnic University, 30 Lenin Av., Tomsk, 634050 (Russian Federation); Lukash, V. S. [JSC Research Institute of Semiconductor Devices, 99a Krasnoarmeyskaja St., Tomsk, 634050 (Russian Federation)

    2016-01-15

    In most promising widespread gallium nitride based LEDs emission is generated in the blue spectral region with a maximum at about 450 nm which is converted to visible light with the desired spectrum by means of phosphor. The thermal energy in the conversion is determined by the difference in the energies of excitation and emission quanta and the phosphor quantum yield. Heat losses manifest themselves as decrease in the luminous efficacy. LED heating significantly reduces its efficiency and life. In addition, while heating, the emission generation output and the efficiency of the emission conversion decrease. Therefore, the reduction of the energy losses caused by heating is crucial for LED development. In this paper, heat losses in phosphor-converted LEDs (hereinafter chips) during spectrum conversion are estimated. The limit values of the luminous efficacy for white LEDs are evaluated.

  20. ZnO-nanorods: A possible white LED phosphor

    Science.gov (United States)

    Sarangi, Sachindra Nath; T., Arun; Ray, Dinseh K.; Sahoo, Pratap Kumar; Nozaki, Shinji; Sugiyama, Noriyuki; Uchida, Kazuo

    2017-05-01

    The white light-emitting diodes (LEDs) have drawn much attention to replace conventional lighting sources because of low energy consumption, high light efficiency and long lifetime. Although the most common approach to produce white light is to combine a blue LED chip and a yellow phosphor, such a white LED cannot be used for a general lighting application, which requires a broad luminescence spectrum in the visible wavelength range. We have successfully chemically synthesized the ZnO nanorods showing intense broad luminescence in the visible wavelength range and made a white LED using the ZnO nanorods as phosphor excited with a blue LED. Their lengths and diameters were 2 - 10 μm and 200 - 800 nm, respectively. The wurtzite structure was confirmed by the x-ray diffraction measurement. The PL spectrum obtained by exciting the ZnO nanorods with the He-Cd laser has two peaks, one associated with the near band-edge recombination and the other with recombination via defects. The peak intensity of the near band-edge luminescence at 388 nm is much weaker than that of the defect-related luminescence. The latter luminescence peak ranges from 450 to 850 nm and broad enough to be used as a phosphor for a white LED. A white LED has been fabricated using a blue LED with 450 nm emission and ZnO nanorod powders. The LED performances show a white light emission and the electroluminescence measurement shows a stiff increase in white light intensity with increasing blue LED current. The Commission International de1'Eclairage (CIE) chromaticity colour coordinates of 450 nm LED pumped white emission shows a coordinate of (0.31, 0.32) for white LED at 350 mA. These results indicate that ZnO nanorods provides an alternate and effective approach to achieve high-performance white LEDs and also other optoelectronic devices.

  1. Using rare earth doped thiosilicate phosphors in white light emitting LEDs: Towards low colour temperature and high colour rendering

    International Nuclear Information System (INIS)

    Smet, P.F.; Korthout, K.; Haecke, J.E. van; Poelman, D.

    2008-01-01

    Rare earth doped thiosilicates are promising materials for use in phosphor converted light emitting diodes (pcLEDs). These phosphors (including the hosts Ca 2 SiS 4 , BaSi 2 S 5 and Ba 2 SiS 4 in combination with Ce 3+ and/or Eu 2+ doping) cover the entire visible part of the spectrum, as the emission colour can be changed from deep blue to red. The photoluminescence emission spectrum and the overlap of the excitation spectrum with the emission of pumping LEDs is evaluated. The trade-off between high colour rendering and high electrical-to-optical power efficiency is discussed by simulation with both blue and UV emitting LEDs. Finally, a phosphor combination with low colour temperature (3000 K) and high colour rendering (CRI = 93) is proposed

  2. Long-term stable stacked CsPbBr3 quantum dot films for highly efficient white light generation in LEDs.

    Science.gov (United States)

    Song, Young Hyun; Yoo, Jin Sun; Kang, Bong Kyun; Choi, Seung Hee; Ji, Eun Kyung; Jung, Hyun Suk; Yoon, Dae Ho

    2016-12-01

    We report highly efficient ethyl cellulose with CsPbBr 3 perovskite QD films for white light generation in LED application. Ethyl cellulose with CsPbBr 3 quantum dots is applied with Sr 2 Si 5 N 8  : Eu 2+ red phosphor on an InGaN blue chip, achieving a highly efficient luminous efficacy of 67.93 lm W -1 under 20 mA current.

  3. Photobiocatalytic alcohol oxidation using LED light sources

    NARCIS (Netherlands)

    Rauch, M.C.R.; Schmidt, S.; Arends, I.W.C.E.; oppelt, K.; Kara, S; Hollmann, F.

    2016-01-01

    The photocatalytic oxidation of NADH using a flavin photocatalyst and a simple blue LED light source is reported. This in situ NAD+ regeneration system can be used to promote biocatalytic, enantioselective oxidation reactions. Compared to the traditional use of white light bulbs this method enables

  4. Selecting the optimal synthesis parameters of InP/CdxZn1-xSe quantum dots for a hybrid remote phosphor white LED for general lighting applications.

    Science.gov (United States)

    Ryckaert, Jana; Correia, António; Tessier, Mickael D; Dupont, Dorian; Hens, Zeger; Hanselaer, Peter; Meuret, Youri

    2017-11-27

    Quantum dots can be used in white LEDs for lighting applications to fill the spectral gaps in the combined emission spectrum of the blue pumping LED and a broad band phosphor, in order to improve the source color rendering properties. Because quantum dots are low scattering materials, their use can also reduce the amount of backscattered light which can increase the overall efficiency of the white LED. The absorption spectrum and narrow emission spectrum of quantum dots can be easily tuned by altering their synthesis parameters. Due to the re-absorption events between the different luminescent materials and the light interaction with the LED package, determining the optimal quantum dot properties is a highly non-trivial task. In this paper we propose a methodology to select the optimal quantum dot to be combined with a broad band phosphor in order to realize a white LED with optimal luminous efficacy and CRI. The methodology is based on accurate and efficient simulations using the extended adding-doubling approach that take into account all the optical interactions. The method is elaborated for the specific case of a hybrid, remote phosphor white LED with YAG:Ce phosphor in combination with InP/CdxZn 1-x Se type quantum dots. The absorption and emission spectrum of the quantum dots are generated in function of three synthesis parameters (core size, shell size and cadmium fraction) by a semi-empirical 'quantum dot model' to include the continuous tunability of these spectra. The sufficiently fast simulations allow to scan the full parameter space consisting of these synthesis parameters and luminescent material concentrations in terms of CRI and efficacy. A conclusive visualization of the final performance allows to make a well-considered trade-off between these performance parameters. For the hybrid white remote phosphor LED with YAG:Ce and InP/CdxZn 1-x Se quantum dots a CRI Ra = 90 (with R9>50) and an overall efficacy of 110 lm/W is found.

  5. An inverse method for color uniformity in white LED spotlights

    NARCIS (Netherlands)

    Prins, C.R.; Thije Boonkkamp, ten J.H.M.; Tukker, T.W.; IJzerman, W.L.

    2013-01-01

    Color over Angle (CoA) variation in the light output of white phosphor-converted LEDs is a common problem in LED lighting technology. In this article we propose an inverse method to design an optical element that eliminates the color variation for a point light source. The method in this article is

  6. An inverse method for color uniformity in white LED spotlights

    NARCIS (Netherlands)

    Prins, C.R.; Thije Boonkkamp, ten J.H.M.; Tukker, T.W.; IJzerman, W.L.

    2014-01-01

    Color over Angle (CoA) variation in the light output of white phosphor-converted LEDs is a common problem in LED lighting technology. In this article we propose an inverse method to design an optical element that eliminates the color variation for a point light source. The method in this article is

  7. Broadband white light emission from Ce:AlN ceramics: High thermal conductivity down-converters for LED and laser-driven solid state lighting

    Directory of Open Access Journals (Sweden)

    A. T. Wieg

    2016-12-01

    Full Text Available We introduce high thermal conductivity aluminum nitride (AlN as a transparent ceramic host for Ce3+, a well-known active ion dopant. We show that the Ce:AlN ceramics have overlapping photoluminescent (PL emission peaks that cover almost the entire visible range resulting in a white appearance under 375 nm excitation without the need for color mixing. The PL is due to a combination of intrinsic AlN defect complexes and Ce3+ electronic transitions. Importantly, the peak intensities can be tuned by varying the Ce concentration and processing parameters, causing different shades of white light without the need for multiple phosphors or light sources. The Commission Internationale de l’Eclairage coordinates calculated from the measured spectra confirm white light emission. In addition, we demonstrate the viability of laser driven white light emission by coupling the Ce:AlN to a readily available frequency tripled Nd-YAG laser emitting at 355 nm. The high thermal conductivity of these ceramic down-converters holds significant promise for producing higher power white light sources than those available today.

  8. Quantifying the radiant exposure and effective dose in patients treated for actinic keratoses with topical photodynamic therapy using daylight and LED white light

    Science.gov (United States)

    Manley, M.; Collins, P.; Gray, L.; O'Gorman, S.; McCavana, J.

    2018-02-01

    Daylight photodynamic therapy (dl-PDT) is as effective as conventional PDT (c-PDT) for treating actinic keratoses but has the advantage of reducing patient discomfort significantly. Topical dl-PDT and white light-PDT (wl-PDT) differ from c-PDT by way of light sources and methodology. We measured the variables associated with light dose delivery to skin surface and influence of geometry using a radiometer, a spectral radiometer and an illuminance meter. The associated errors of the measurement methods were assessed. The spectral and spatial distribution of the radiant energy from the LED white light source was evaluated in order to define the maximum treatment area, setup and treatment protocol for wl-PDT. We compared the data with two red LED light sources we use for c-PDT. The calculated effective light dose is the product of the normalised absorption spectrum of the photosensitizer, protoporphyrin IX (PpIX), the irradiance spectrum and the treatment time. The effective light dose from daylight ranged from 3  ±  0.4 to 44  ±  6 J cm-2due to varying weather conditions. The effective light dose for wl-PDT was reproducible for treatments but it varied across the treatment area between 4  ±  0.1 J cm-2 at the edge and 9  ±  0.1 J cm-2 centrally. The effective light dose for the red waveband (615-645 nm) was 0.42  ±  0.05 J cm-2 on a clear day, 0.05  ±  0.01 J cm-2 on an overcast day and 0.9  ±  0.01 J cm-2 using the white light. This compares with 0.95  ±  0.01 and 0.84  ±  0.01 J cm-2 for c-PDT devices. Estimated errors associated with indirect determination of daylight effective light dose were very significant, particularly for effective light doses less than 5 J cm-2 (up to 83% for irradiance calculations). The primary source of error is in establishment of the relationship between irradiance or illuminance and effective dose. Use of the O’Mahoney model is recommended using a

  9. Tunable white light generation from Ce{sup 3+}-Tb{sup 3+}-Mn{sup 2+} doped metaphosphate glass for LED and solar cell applications

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Debarati; Biswas, K.; Balaji, S. [CSIR-Network of Institute for Solar Energy (NISE) (India); Glass Division, Glass Science and Technology Section, CSIR-Central Glass and Ceramic Research Institute, 196, Raja S.C. Mullick Road, Kolkata 700032 (India); Annapurna, K., E-mail: annapurnak@cgcri.res.in [CSIR-Network of Institute for Solar Energy (NISE) (India); Glass Division, Glass Science and Technology Section, CSIR-Central Glass and Ceramic Research Institute, 196, Raja S.C. Mullick Road, Kolkata 700032 (India)

    2017-03-15

    Alkali free Ba-Al metaphosphate glasses doped with Ce, Tb and Mn are prepared and their concentration is tuned to achieve white light emission for production of LEDs and luminescent concentrator for Si-PV applications. The occurrence of a redox reaction among dopant ions (Ce{sup 4+}, Tb{sup 3+}→Ce{sup 3+}, Tb{sup 4+}) is observed from the absorption spectra while there is no change in oxidation state of Mn{sup 2+} ions. This is confirmed from ESR studies. Emission spectra indicated effective downshifting of radiation from near visible to green and red region of the spectrum. On tuning the concentration of Tb{sup 3+} and Mn{sup 2+}, bright white light emission (CIE coordinates: x=3.32, y=3.33) corresponding to CCT of 5900 K is obtained. This white light produced has been further tuned to different hues by varying the excitation wavelength of this triply doped glass.

  10. Practical lighting design with LEDs

    CERN Document Server

    Lenk, Ron

    2016-01-01

    The second edition of Practical Lighting Design with LEDs has been revised and updated to provide the most current information for developing light-emitting diodes products. The authors, noted authorities in the field, offer a review of the most relevant topics including optical performance, materials, thermal design, and modeling and measurement. Comprehensive in scope, the text covers all the information needed to design LEDs into end products.

  11. Tunable white light of a Ce3+,Tb3+,Mn2+ triply doped Na2Ca3Si2O8 phosphor for high colour-rendering white LED applications: tunable luminescence and energy transfer.

    Science.gov (United States)

    Lü, Wei; Xu, Huawei; Huo, Jiansheng; Shao, Baiqi; Feng, Yang; Zhao, Shuang; You, Hongpeng

    2017-07-18

    A tunable white light emitting Na 2 Ca 3 Si 2 O 8 :Ce 3+ ,Tb 3+ ,Mn 2+ phosphor with a high color rendering index (CRI) has been prepared. Under UV excitation, Na 2 Ca 3 Si 2 O 8 :Ce 3+ phosphors present blue luminescence and exhibit a broad excitation ranging from 250 to 400 nm. When codoping Tb 3+ /Mn 2+ ions into Na 2 Ca 3 Si 2 O 8 , energy transfer from Ce 3+ to Tb 3+ and Ce 3+ to Mn 2+ ions is observed from the spectral overlap between Ce 3+ emission and Tb 3+ /Mn 2+ excitation spectra. The energy-transfer efficiencies and corresponding mechanisms are discussed in detail. The mechanism of energy transfer from Ce 3+ to Tb 3+ is demonstrated to be a dipole-quadrupole mechanism by the Inokuti-Hirayama model. The wavelength-tunable white light can be realized by coupling the emission bands centered at 440, 550 and 590 nm ascribed to the contribution from Ce 3+ , Tb 3+ and Mn 2+ , respectively. The commission on illumination value of color tunable emission can be tuned by controlling the content of Ce 3+ , Tb 3+ and Mn 2+ . Temperature-dependent luminescence spectra proved the good thermal stability of the as-prepared phosphor. White LEDs with CRI = 93.5 are finally fabricated using a 365 nm UV chip and the as-prepared Na 2 Ca 3 Si 2 O 8 :Ce 3+ ,Tb 3+ ,Mn 2+ phosphor. All the results suggest that Na 2 Ca 3 Si 2 O 8 :Ce 3+ ,Tb 3+ ,Mn 2+ can act as potential color-tunable and single-phase white emission phosphors for possible applications in UV based white LEDs.

  12. LEDs light up the world

    Energy Technology Data Exchange (ETDEWEB)

    Mather, N.

    2004-06-30

    A lighting system using light-emitting diodes, and privately financed by a Canadian engineering professor at the University of Calgary, has been set up in a village in Nepal in 2000. Since then, through the efforts of the 'Light Up The World' Foundation, established by Dr. Irvine-Halliday, projects have lit up thousands of homes in the Philippines, India, Afghanistan, the Galapagos Islands, Mexico, Sri Lanka, and Angola. Although the goal of the project is primarily to provide lighting for reading and writing for school-children, the project has been the source of many other advantages; creation of enterprise, increased employment, enhanced income, gender equality, and improvements in health and safety among them. Since LED lamps in most cases replace kerosene lamps, the system also has significant environmental benefits. The system as originally envisioned creates electricity by pedal-powered generator, or by solar panels connected to a battery, depending on what is available at each home. Each home is connected to the power supply and supplied with low-energy diode lamps. The lights are extremely efficient and many homes can be equipped with them using less energy than it takes to power a single 100-watt light bulb. 5 photos.

  13. Future Solid State Lighting using LEDs and Diode Lasers

    DEFF Research Database (Denmark)

    Petersen, Paul Michael

    2014-01-01

    applications. Within the coming years, it is expected that the efficiency of blue laser diodes will approach the efficiency of infrared diode lasers. This will enable high efficiency white light generation with very high lumen per watt values. SSL today is mainly based on phosphor converted blue light emitting......Lighting accounts for 20% of all electrical energy usage. Household lighting and commercial lighting such as public and street lighting are responsible for significant greenhouse gas emissions. Therefore, currently many research initiatives focus on the development of new light sources which shows...... significant savings. Solid state lighting (SSL) based on LEDs is today the most efficient light source for generation of high quality white light. Diode lasers, however, have the potential of being more efficient than LEDs for the generation of white light. A major advantage using diode lasers for solid state...

  14. Light Converting Inorganic Phosphors for White Light-Emitting Diodes

    OpenAIRE

    Chen, Lei; Lin, Chun-Che; Yeh, Chiao-Wen; Liu, Ru-Shi

    2010-01-01

    White light-emitting diodes (WLEDs) have matched the emission efficiency of florescent lights and will rapidly spread as light source for homes and offices in the next 5 to 10 years. WLEDs provide a light element having a semiconductor light emitting layer (blue or near-ultraviolet (nUV) LEDs) and photoluminescence phosphors. These solid-state LED lamps, rather than organic light emitting diode (OLED) or polymer light-emitting diode (PLED), have a number of advantages over conventional incand...

  15. Fabrication of a white-light-emitting organic LED adopting the two-wavelength method by using new DPVBi derivatives and an analysis of its characteristics

    International Nuclear Information System (INIS)

    Oh, Hwan-Sool; Cho, Jae-Young; Yoon, Seok-Beom; Kang, Myung-Koo

    2004-01-01

    The white-light emission of the two-wavelength method was represented by the processes of compounding new DPVBi derivatives, methyl-DPVT and nitro-DPVT, from the blue-emitting material DPVBi, after which blue light was emitted from nitro-DPVT and orange light was emitted by doping methyl-DPVT as a host material with Rubrene as a guest material. The basic structure of the fabricated organic white-light-emitting organic light-emitting device (OLED) was glass/ITO/NPB(150 A)/nitro-DPVT(100 A)/methyl-DPVT:Rubrene [2.0 wt%]/BCP(70 A)/Alq 3 (150 A)/Al(600 A).We evaluated the characteristics by varying the thickness of the methyl-DPVT:Rubrene layer from 100 A to 90 A to 80 A to 60 A and obtained nearly-pure white light in the Commission Internationale de l'Eclairage (CIE) coordinates (0.3175, 0.3338) in the case where the methyl-DPVT:Rubrene layer was 60-A thick. It turned out that the device remained stable against voltage changes, the turn-on voltage was 3.5 V, the light-emitting turn-on voltage was 4 V, and the external quantum efficiency was more than 0.5 % for all injection currents.

  16. Development and Performance Assessment of White LED Dimmer

    Science.gov (United States)

    Maiti, Pradip Kr.; Roy, Biswanath

    2017-10-01

    A microcontroller based electronic dimmer is developed using pulse width modulation technique. This dimmer is controllable by infra-red remote within a distance of 4 m and can be electrically connected between LED module and its driver. The performance of a developed LED dimmer is assessed on basis of variation of the photometric parameters of commercially available warm white and cool white LED luminaire used in indoor lighting applications. Four equally spaced dimming levels are considered to measure luminous efficacy, spectral power distribution, CIE 1931 chromaticity coordinates, CIE 1976 CIELUV color difference, correlated color temperature, general color rendering index and one specific color rendering index for saturated red color sample. Variations of above parameters are found out with reference to the values measured at rated voltage without the developed dimmer. Analysis of experimentally measured data shows that the developed LED dimmer is capable to vary light output of the WLED luminaire within a range of 25-100% without appreciable variation of its photometric and color parameters. The only exception is observed for the luminous efficacy parameter where it shows about 17 and 14.7% reduction for warm white and cool white LED luminaire at 25% dimming level.

  17. Smart lighting using LED luminaries

    NARCIS (Netherlands)

    Bhardwaj, S.; Ozcelebi, T.; Lukkien, J.J.

    2010-01-01

    The target of a smart lighting system is to control light sources in an environment (e.g. home, office) adaptively according to user contexts and preferences. Literature work in this area focuses on traditional light sources such as incandescent and fluorescent lights, whereas this paper takes a

  18. Recent developments in white light emitting diodes

    Science.gov (United States)

    Lohe, P. P.; Nandanwar, D. V.; Belsare, P. D.; Moharil, S. V.

    2018-05-01

    In the recent years solid state lighting based on LEDs has revolutionized lighting technology. LEDs have many advantages over the conventional lighting based on fluorescent and incandescent lamps such as mercury free, high conversion efficiency of electrical energy into light, long lifetime reliability and ability to use with many types of devices. LEDs have emerged as a new potentially revolutionary technology that could save up to half of energy used for lighting applications. White LEDs would be the most important light source in the future, so much so that this aspect had been highlighted by the Nobel committee during the award of 2014 Nobel Prize for Physics. Recent advancement in the fabrication of GaN chip capable of emitting in blue and near UV region paved way for fabrication of white LED lamps. Mainly there are two approaches used for preparing white emitting solid state lamp. In the first approach blue light (λ=450 nm) emitted from the InGaN LED chip is partially absorbed by the YAG:Ce3+ phosphor coated on it and re-emitted as yellow fluorescence. A white light can be generated by the combination of blue + yellow emission bands. These lamps are already available. But they are suffering from major drawback that their Colour Rendering Index (CRI) is low. In the second approach, white LEDs are made by coating near ultraviolet emitting (360 to 410nm) LED with a mixture of high efficiency red, green and blue emitting phosphors, analogous to the fluorescent lamp. This method yields lamps with better color rendition. Addition of a yellow emitting phosphor improves CRI further. However conversion efficiency is compromised to some extent. Further the cost of near UV emitting chip is very high compared to blue emitting chips. Thus cost and light output wise, near UV chips are much inferior to blue chips. Recently some rare earth activated oxynitrides, silicates, fluorides have emerged as an important family of luminescent materials for white LED application

  19. Plant growth with Led lighting systems

    International Nuclear Information System (INIS)

    Campiotti, C.A.; Bernardini, A.; Di Carlo, F.; Scoccianti, M.; Alonzo, G.; Carlino, M.; Dondi, F.; Bibbiani, C.

    2009-01-01

    Leds lighting is highly relevant for the horticultural industry. Compared to other light sources used for plant production, leds have several properties which are potentially useful in relation to horticulture. However, although LEDs technology has raised strong interest in research for extraterrestrial agriculture, current LEDs panel costs are still too high for commercial adoption in greenhouse sector, and their electrical efficacies do not compete with those of high-pressure sodium lamps, but several manufactures are working to address these issues. When LEDs become practical, their ability to based light sources specifically suitable for photosynthesis and other horticulturally relevant plant properties (i.e. low radiated heat; lighting from within the canopy) will render the narrow band spectrum of LEDs of particular interest for providing light to greenhouse horticulture. A general description of LEDs application and their technical characteristics is briefly reported. [it

  20. Goniometric characterization of LED based greenhouse lighting

    DEFF Research Database (Denmark)

    Thorseth, Anders; Lindén, Johannes; Corell, Dennis Dan

    2015-01-01

    This paper describes a demonstration of goniospectroradiometry for characterizations of new light emitting diode (LED) based luminaries for enhanced photosynthesis in greenhouses. It highlights the differences between measurement of the traditional high pressure sodium (HPS) luminaries and the LED...

  1. Light extraction efficiency enhancement for fluorescent SiC based white light-emitting diodes

    DEFF Research Database (Denmark)

    Ou, Haiyan; Ou, Yiyu; Argyraki, Aikaterini

    Fluorescent SiC based white light-emitting diodes(LEDs) light source, as an innovative energy-efficient light source, would even have longer lifetime, better light quality and eliminated blue-tone effect, compared to the current phosphor based white LED light source. In this paper, the yellow...

  2. LED lighting increases the ecological impact of light pollution irrespective of color temperature.

    Science.gov (United States)

    Pawson, S M; Bader, M K-F

    Recognition of the extent and magnitude of night-time light pollution impacts on natural ecosystems is increasing, with pervasive effects observed in both nocturnal and diurnal species. Municipal and industrial lighting is on the cusp of a step change where energy-efficient lighting technology is driving a shift from “yellow” high-pressure sodium vapor lamps (HPS) to new “white” light-emitting diodes (LEDs). We hypothesized that white LEDs would be more attractive and thus have greater ecological impacts than HPS due to the peak UV-green-blue visual sensitivity of nocturnal invertebrates. Our results support this hypothesis; on average LED light traps captured 48% more insects than were captured with light traps fitted with HPS lamps, and this effect was dependent on air temperature (significant light × air temperature interaction). We found no evidence that manipulating the color temperature of white LEDs would minimize the ecological impacts of the adoption of white LED lights. As such, large-scale adoption of energy-efficient white LED lighting for municipal and industrial use may exacerbate ecological impacts and potentially amplify phytosanitary pest infestations. Our findings highlight the urgent need for collaborative research between ecologists and electrical engineers to ensure that future developments in LED technology minimize their potential ecological effects.

  3. LED Lighting in a Performing Arts Building

    Energy Technology Data Exchange (ETDEWEB)

    Miller, N. J.; Kaye, S. M. [Univ. of Florida, Gainesville, FL (United States); Coleman, P. M. [Univ. of Florida, Gainesville, FL (United States); Wilkerson, A. M.; Perrin, T. E.; Sullivan, G. P. [Efficiency Solutions, Inc., Richland, WA (United States)

    2014-07-31

    At the University of Florida in Gainesville, the DOE Solid-State Lighting GATEWAY program evaluated LED architectural and theatrical lighting in four academic/performance-related spaces within the Nadine McGuire Theatre + Dance Pavilion. Due to a wise choice of products and luminaire light distributions, the change brought significant quality improvements including improved controllability and color.

  4. Continuous light-emitting Diode (LED) lighting for improving food quality

    OpenAIRE

    Lu, C; Bian, Z

    2016-01-01

    Lighting-emitting diodes (LEDs) have shown great potential for plant growth and development, with higher luminous efficiency and positive impact compared with other artificial lighting. The combined effects of red/blue or/and green, and white LED light on plant growth and physiology, including chlorophyll fluorescence, nitrate content and phytochemical concentration before harvest, were investigated. The results showed that continuous light (CL)\\ud exposure at pre-harvest can effectively redu...

  5. Light Converting Inorganic Phosphors for White Light-Emitting Diodes

    Directory of Open Access Journals (Sweden)

    Chiao-Wen Yeh

    2010-03-01

    Full Text Available White light-emitting diodes (WLEDs have matched the emission efficiency of florescent lights and will rapidly spread as light source for homes and offices in the next 5 to 10 years. WLEDs provide a light element having a semiconductor light emitting layer (blue or near-ultraviolet (nUV LEDs and photoluminescence phosphors. These solid-state LED lamps, rather than organic light emitting diode (OLED or polymer light-emitting diode (PLED, have a number of advantages over conventional incandescent bulbs and halogen lamps, such as high efficiency to convert electrical energy into light, reliability and long operating lifetime. To meet with the further requirement of high color rendering index, warm light with low color temperature, high thermal stability and higher energy efficiency for WLEDs, new phosphors that can absorb excitation energy from blue or nUV LEDs and generate visible emissions efficiently are desired. The criteria of choosing the best phosphors, for blue (450-480 nm and nUV (380-400 nm LEDs, strongly depends on the absorption and emission of the phosphors. Moreover, the balance of light between the emission from blue-nUV LEDs and the emissions from phosphors (such as yellow from Y3Al5O12:Ce3+ is important to obtain white light with proper color rendering index and color temperature. Here, we will review the status of phosphors for LEDs and prospect the future development.

  6. Light Converting Inorganic Phosphors for White Light-Emitting Diodes

    Science.gov (United States)

    Chen, Lei; Lin, Chun-Che; Yeh, Chiao-Wen; Liu, Ru-Shi

    2010-01-01

    White light-emitting diodes (WLEDs) have matched the emission efficiency of florescent lights and will rapidly spread as light source for homes and offices in the next 5 to 10 years. WLEDs provide a light element having a semiconductor light emitting layer (blue or near-ultraviolet (nUV) LEDs) and photoluminescence phosphors. These solid-state LED lamps, rather than organic light emitting diode (OLED) or polymer light-emitting diode (PLED), have a number of advantages over conventional incandescent bulbs and halogen lamps, such as high efficiency to convert electrical energy into light, reliability and long operating lifetime. To meet with the further requirement of high color rendering index, warm light with low color temperature, high thermal stability and higher energy efficiency for WLEDs, new phosphors that can absorb excitation energy from blue or nUV LEDs and generate visible emissions efficiently are desired. The criteria of choosing the best phosphors, for blue (450−480 nm) and nUV (380−400 nm) LEDs, strongly depends on the absorption and emission of the phosphors. Moreover, the balance of light between the emission from blue-nUV LEDs and the emissions from phosphors (such as yellow from Y3Al5O12:Ce3+) is important to obtain white light with proper color rendering index and color temperature. Here, we will review the status of phosphors for LEDs and prospect the future development.

  7. Materials and Designs for High-Efficacy LED Light Engines

    Energy Technology Data Exchange (ETDEWEB)

    Ibbetson, James [Cree, Inc., Durham, NC (United States); Gresback, Ryan [Cree, Inc., Durham, NC (United States)

    2017-09-28

    Cree, Inc. conducted a narrow-band downconverter (NBD) materials development and implementation program which will lead to warm-white LED light engines with enhanced efficacy via improved spectral efficiency with respect to the human eye response. New red (600-630nm) NBD materials could result in as much as a 20% improvement in warm-white efficacy at high color quality relative to conventional phosphor-based light sources. Key program innovations included: high quantum yield; narrow peak width; minimized component-level losses due to “cross-talk” and light scattering among red and yellow-green downconverters; and improved reliability to reach parity with conventional phosphors. NBD-enabled downconversion efficiency gains relative to conventional phosphors yielded an end-of-project LED light engine efficacy of >160 lm/W at room temperature and 35 A/cm2, with a correlated color temperature (CCT) of ~3500K and >90 CRI (Color Rending Index). NBD-LED light engines exhibited equivalent luminous flux and color point maintenance at >1,000 hrs. of highly accelerated reliability testing as conventional phosphor LEDs. A demonstration luminaire utilizing an NBD-based LED light engine had a steady-state system efficacy of >150 lm/W at ~3500K and >90 CRI, which exceeded the 2014 DOE R&D Plan luminaire milestone for FY17 of >150 lm/W at just 80 CRI.

  8. Novel rare-earth doped silicon-nitride based materials as promising conversion phosphors for white LEDs

    NARCIS (Netherlands)

    Li, Yuan Qiang; Hintzen, H.T.J.M.

    2006-01-01

    Lighting world will change drastically due to the replacement of the traditional TL, PL and incandescent lamps by white LEDs. Advantageous features of white LEDs are a longer lifetime, lower energy consumption and extended possibilities for integration and miniaturisation. A white LED can be

  9. Visual color matching system based on RGB LED light source

    Science.gov (United States)

    Sun, Lei; Huang, Qingmei; Feng, Chen; Li, Wei; Wang, Chaofeng

    2018-01-01

    In order to study the property and performance of LED as RGB primary color light sources on color mixture in visual psychophysical experiments, and to find out the difference between LED light source and traditional light source, a visual color matching experiment system based on LED light sources as RGB primary colors has been built. By simulating traditional experiment of metameric color matching in CIE 1931 RGB color system, it can be used for visual color matching experiments to obtain a set of the spectral tristimulus values which we often call color-matching functions (CMFs). This system consists of three parts: a monochromatic light part using blazed grating, a light mixing part where the summation of 3 LED illuminations are to be visually matched with a monochromatic illumination, and a visual observation part. The three narrow band LEDs used have dominant wavelengths of 640 nm (red), 522 nm (green) and 458 nm (blue) respectively and their intensities can be controlled independently. After the calibration of wavelength and luminance of LED sources with a spectrophotometer, a series of visual color matching experiments have been carried out by 5 observers. The results are compared with those from CIE 1931 RGB color system, and have been used to compute an average locus for the spectral colors in the color triangle, with white at the center. It has been shown that the use of LED is feasible and has the advantages of easy control, good stability and low cost.

  10. Concept of white light in stage lighting

    Science.gov (United States)

    Rinaldi, Mauricio R.

    2002-06-01

    In perceiving objects, generally we see them in a white light situation. But, actually, there is not an absolute white, in such a manner that the different light sources have a determined kind of white, what it is known as color temperature. Even the white light may be of different kinds (different color temperature), the individual mind tends to perceive it as the same kind of white, that is to say, there is in our mind a psychological function by which we operate an integration in the perception in order to do the object perceptually invariable. On the other hand, it is a common practice in stage lighting to use color light sources. It is a well known phenomenon that a color of light produces a change in the object color perception. However, when we go to theater, we see the objects as having their real color, even if the lighting is not white. In this paper the concept of white light in stage lighting is presented, showing its possibilities of aesthetical expression.

  11. 130 LPW 1000 Lm Warm White LED for Illumination

    Energy Technology Data Exchange (ETDEWEB)

    Soer, Wouter [Philips Lumileds Lighting Company LLC, San Jose, CA (United States)

    2012-12-21

    An illumination-grade warm-white LED, having correlated color temperature (CCT) between 2700 and 3500 K and capable of producing 1000 lm output at over 130 lm/W at room temperature, has been developed in this program. The high-power warm-white LED is an ideal source for use in indoor and outdoor lighting applications. Over the two year period, we have made the following accomplishments: • Developed a low-cost high-power white LED package and commercialized a series of products with CCT ranging from 2700 to 5700 K under the product name LUXEON M; • Demonstrated a record efficacy of 124.8 lm/W at a flux of 1023 lm, CCT of 3435 K and color rendering index (CRI) over 80 at room temperature in the productized package; • Demonstrated a record efficacy of 133.1 lm/W at a flux of 1015 lm, CCT of 3475 K and CRI over 80 at room temperature in an R&D package. The new high-power LED package is a die-on-ceramic surface mountable LED package. It has four 2 mm2 InGaN pump dice, flip-chip attached to a ceramic submount in a 2x2 array configuration. The submount design utilizes a design approach that combines a high-thermal- conductivity ceramic core for die attach and a low-cost and low-thermal-conductivity ceramic frame for mechanical support and as optical lens carrier. The LED package has a thermal resistance of less than 1.25 K/W. The white LED fabrication also adopts a new batch level (instead of die-by-die) phosphor deposition process with precision layer thickness and composition control, which provides not only tight color control, but also low cost. The efficacy performance goal was achieved through the progress in following key areas: (1) high-efficiency royal blue pump LED development through active region design and epitaxial growth quality improvement (funded by internal programs); (2) improvement in extraction efficiency from the LED package through improvement of InGaN-die-level and package-level optical extraction efficiency; and (3) improvement in phosphor

  12. LED Context Lighting System in Residential Areas

    Directory of Open Access Journals (Sweden)

    Sook-Youn Kwon

    2014-01-01

    Full Text Available As issues of environment and energy draw keen interest around the globe due to such problems as global warming and the energy crisis, LED with high optical efficiency is brought to the fore as the next generation lighting. In addition, as the national income level gets higher and life expectancy is extended, interest in the enhancement of life quality is increasing. Accordingly, the trend of lightings is changing from mere adjustment of light intensity to system lighting in order to enhance the quality of one’s life as well as reduce energy consumption. Thus, this study aims to design LED context lighting system that automatically recognizes the location and acts of a user in residential areas and creates an appropriate lighting environment. The proposed system designed in this study includes three types of processing: first, the creation of a lighting environment index suitable for the user’s surroundings and lighting control scenarios and second, it measures and analyzes the optical characteristics that change depending on the dimming control of lighting and applies them to the index. Lastly, it adopts PIR, piezoelectric, and power sensor to grasp the location and acts of the user and create a lighting environment suitable for the current context.

  13. Controlling the energy transfer via multi luminescent centers to achieve white light/tunable emissions in a single-phased X2-type Y2SiO5:Eu(3+),Bi(3+) phosphor for ultraviolet converted LEDs.

    Science.gov (United States)

    Kang, Fengwen; Zhang, Yi; Peng, Mingying

    2015-02-16

    So far, more than 1000 UV converted phosphors have been reported for potential application in white light-emitting diodes (WLEDs), but most of them (e.g., Y2O2S:Eu, YAG:Ce or CaAlSiN3:Eu) suffer from intrinsic problems such as thermal instability, color aging or re-absorption by commixed phosphors in the coating of the devices. In this case, it becomes significant to search a single-phased phosphor, which can efficiently convert UV light to white lights. Herein, we report a promising candidate of a white light emitting X2-type Y2SiO5:Eu(3+),Bi(3+) phosphor, which can be excitable by UV light and address the problems mentioned above. Single Bi(3+)-doped X2-type Y2SiO5 exhibits three discernible emission peaks at ∼355, ∼408, and ∼504 nm, respectively, upon UV excitation due to three types of bismuth emission centers, and their relative intensity depends tightly on the incident excitation wavelength. In this regard, proper selection of excitation wavelength can lead to tunable emissions of Y2SiO5:Bi(3+) between blue and green, which is partially due to the energy transfer among the Bi centers. As a red emission center Eu(3+) is codoped into Y2SiO5:Bi(3+), energy transfer has been confirmed happening from Bi(3+) to Eu(3+) via an electric dipole-dipole (d-d) interaction. Our experiments reveal that it is easily realizable to create the white or tunable emissions by adjusting the Eu(3+) content and the excitation schemes. Moreover, a single-phased white light emission phosphor, X2-type Y1.998SiO5:0.01Eu(3+),0.01 Bi(3+), has been achieved with excellent resistance against thermal quenching and a QE of 78%. At 200 °C, it preserves >90% emission intensity of that at 25 °C. Consequent three time yoyo experiments of heating-cooling prove no occurrence of thermal degradation. A WLED lamp has been successfully fabricated with a CIE chromaticity coordinate (0.3702, 0.2933), color temperature 4756 K, and color rendering index of 65 by applying the phosphor onto a UV LED

  14. Enhancement of white-light-emission from single-phase Sr5(PO4)3F:Eu(2+),Mn(2+) phosphors for near-UV white LEDs.

    Science.gov (United States)

    Feng, Yaomiao; Huang, Jinping; Liu, Lili; Liu, Jie; Yu, Xibin

    2015-09-07

    A series of single-phase broadband white-light-emitting Sr5(PO4)3F:Eu(2+),Mn(2+) phosphors were prepared by a solid state reaction. The luminescence property, and the crystal and electronic structures of the fluorophosphates were studied by photoluminescence analysis, XRD Rietveld refinement and density functional theory calculation (DFT), respectively. Under near ultraviolet excitation in the 250 to 430 nm wavelength range, the phosphors exhibit two emission bands centered at 440 and 556 nm, caused by the Eu(2+) and Mn(2+) ions. By altering the relative ratios of Eu(2+) and Mn(2+) in the compounds, the emission color could be modulated from blue to white. The efficient energy transfer from the Eu(2+) to Mn(2+) ions could be ascribed to the well crystallized host lattice and the facile substitution of Eu(2+) and Mn(2+) for Sr(2+) sites due to similar ionic radii. A series of fluxes were investigated to improve the photoluminescence intensity. When KCl was used as flux in the synthesis, the photoluminescence intensity of Sr5(PO4)3F:Eu(2+),Mn(2+) was enhanced by 85% compared with no fluxes added. These results demonstrate that the single-phase Sr5(PO4)3F:Eu(2+),Mn(2+) with enhanced luminescence efficiency could be promising as a near UV-convertible direct white-light-emitting phosphor for WLED applications.

  15. Sustainable LED Fluorescent Light Replacement Technology

    Energy Technology Data Exchange (ETDEWEB)

    None, None

    2011-09-30

    Ilumisys and the National Center for Manufacturing Sciences (NCMS) partnered on a three-year project awarded by the United States (U.S.) Department of Energy (DOE), to quantify the impacts of LED lamps, incandescent lamps and fluorescent benchmark lamps over a product lifecycle – i.e. to develop a sustainable design and manufacturing strategy that addresses product manufacturing, use, recycling and disposal scenarios for LED-based lighting. Based on the knowledge gained from extensive product tear-down studies of fluorescent and screw-in lighting products, lifecycle assessment tools, and accelerated lifecycle testing protocols, an interactive Sustainable LED Design Guide has been developed to aid architectural and lighting designers and engineers in making design decisions that consider three important environmental impacts (greenhouse gas emissions, energy use and mercury emission) across all phases of the life of an LED lighting product. Critical information developed for the lifecycle analysis and product feature comparisons is the useful life of the lighting product as well as its performance. The Design Guide is available at www.ncms.org, and was developed based on operational and durability testing of a variety of lighting products including power consumption, light output, and useful life of a lamp in order to allow a more realistic comparison of lamp designs. This report describes the main project tasks, results and innovative features of the lifecycle assessment (LCA)-based design tools, and the key considerations driving the sustainable design of LED lighting systems. The Design Guide incorporates the following three novel features for efficiently evaluating LED lighting features in value-chains: Bill-of-Materials (BOM) Builder – Designers may import process data for each component and supply functional data for the product, including power, consumption, lumen output and expected useful life: Environmental Impact Review – Designs are comparable

  16. LED Street Lighting Solutions: Flagstaff, Arizona as a Case Study

    Science.gov (United States)

    Hall, Jeffrey C.

    2018-01-01

    Dark-sky protection in Flagstaff, Arizona extends back to 1958, with the first ordinance in the City banning advertising floodlights. The current ordinance, adopted in 1989, is comprehensive and has played a critical role in maintaining the quality of the night sky for astronomy, tourism, public enjoyment, and other purposes. Flagstaff, like many communities around the world, is now working on a transition from legacy bulb-based technology to LED for its outdoor lighting. The City, Lowell Observatory, the U. S. Naval Observatory, and the Flagstaff Dark Skies Coalition have been working intensively for two years to identify an LED-based street lighting solution that will preserve the City's dark skies while meeting municipal needs. We will soon be installing test fixtures for an innovative solution incorporating narrow-band amber LED and modest amounts of low-CCT white LED. In this talk, I will review the types of LEDs available for outdoor lighting and discuss the plans for Flagstaff's street lighting in the LED era, which we hope will be a model for communities worldwide.

  17. Blue laser diode (LD) and light emitting diode (LED) applications

    International Nuclear Information System (INIS)

    Bergh, Arpad A.

    2004-01-01

    The family of blue LEDs, edge emitting and surface emitting lasers, enable a number of applications. Blue lasers are used in digital applications such as optical storage in high density DVDs. The resolution of the spot size and hence the storage density is diffraction limited and is inversely proportional to the square of the wavelength of the laser. Other applications include printing, optical scanners, and high-resolution photo-lithography. As light emitters, blue LEDs are used for signaling and in direct view large area emissive displays. They are also making inroads into signage and LCD back-lighting, mobile platforms, and decorative accent lighting in curtains, furniture, etc. Blue LEDs produce white light either with phosphor wavelength converters or in combination with red and green LEDs. The full potential of LED light sources will require three devices to enable complete control over color and intensity. Sensing and medical/bio applications have a major impact on home security, on monitoring the environment, and on health care. New emerging diagnostic and therapeutic applications will improve the quality and reduce the cost of health care. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. Blue laser diode (LD) and light emitting diode (LED) applications

    Energy Technology Data Exchange (ETDEWEB)

    Bergh, Arpad A [Optoelectronics Industry Development Association (OIDA), 1133 Connecticut Avenue, NW, Suite 600, Washington, DC 20036-4329 (United States)

    2004-09-01

    The family of blue LEDs, edge emitting and surface emitting lasers, enable a number of applications. Blue lasers are used in digital applications such as optical storage in high density DVDs. The resolution of the spot size and hence the storage density is diffraction limited and is inversely proportional to the square of the wavelength of the laser. Other applications include printing, optical scanners, and high-resolution photo-lithography. As light emitters, blue LEDs are used for signaling and in direct view large area emissive displays. They are also making inroads into signage and LCD back-lighting, mobile platforms, and decorative accent lighting in curtains, furniture, etc. Blue LEDs produce white light either with phosphor wavelength converters or in combination with red and green LEDs. The full potential of LED light sources will require three devices to enable complete control over color and intensity. Sensing and medical/bio applications have a major impact on home security, on monitoring the environment, and on health care. New emerging diagnostic and therapeutic applications will improve the quality and reduce the cost of health care. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. CALiPER Report 23: Photometric Testing of White Tunable LED Luminaires

    Energy Technology Data Exchange (ETDEWEB)

    None, None

    2016-01-01

    This report documents an initial investigation of photometric testing procedures for white-tunable LED luminaires and summarizes the key features of those products. Goals of the study include understanding the amount of testing required to characterize a white-tunable product, and documenting the performance of available color-tunable luminaires that are intended for architectural lighting.

  20. Signal processing for LED lighting systems : illumination rendering and sensing

    NARCIS (Netherlands)

    Yang, H.

    2010-01-01

    Solid state lighting, employing high brightness light emitting diodes (LEDs), is becoming increasingly widely used. The advantages of LEDs include high radiative efficiency, long lifetime, limited heat generation and superior tolerance to humidity. Another important advantage of LED lighting systems

  1. A color management system for multi-colored LED lighting

    DEFF Research Database (Denmark)

    Chakrabarti, Maumita; Thorseth, Anders; Jepsen, Jørgen

    2015-01-01

    A new color control system is described and implemented for a five–color LED light engine, covering a wide white gamut. The system combines a new way of using pre-calibrated look-up tables and a rule-based optimization of chromaticity distance from the Planckian locus with a calibrated color sensor....... The color sensor monitors the chromaticity of the mixed light providing the correction factor for the current driver by using the generated look-up table. The long term stability and accuracy of the system will be experimentally investigated with target tolerance within a circle radius 0.0011 in the uniform...

  2. Integration of organic LEDs with inorganic LEDs for a hybrid lighting system

    Science.gov (United States)

    Kong, H. J.; Park, J. W.; Kim, Y. M.

    2013-01-01

    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.

  3. Integration of organic LEDs with inorganic LEDs for a hybrid lighting system

    International Nuclear Information System (INIS)

    Kong, H J; Kim, Y M; Park, J W

    2013-01-01

    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)

  4. Determination of illuminants representing typical white light emitting diodes sources

    DEFF Research Database (Denmark)

    Jost, S.; Ngo, M.; Ferrero, A.

    2017-01-01

    is to develop LED-based illuminants that describe typical white LED products based on their Spectral Power Distributions (SPDs). Some of these new illuminants will be recommended in the update of the CIE publication 15 on colorimetry with the other typical illuminants, and among them, some could be used......Solid-state lighting (SSL) products are already in use by consumers and are rapidly gaining the lighting market. Especially, white Light Emitting Diode (LED) sources are replacing banned incandescent lamps and other lighting technologies in most general lighting applications. The aim of this work...... to complement the CIE standard illuminant A for calibration use in photometry....

  5. Freeform TIR collimators for the removal of angular color variation in white LED spotlights

    NARCIS (Netherlands)

    Prins, C.R.; Schneider, C.; IJzerman, W.L.; Tukker, T.W.; Thije Boonkkamp, ten J.H.M.; Winston, R.; Gordon, J.

    2013-01-01

    Angular color variation in white, phosphor-converted LEDs causes undesirable yellow rings in the beams of spotlights. We developed an inverse method to design TIR collimators that remove the angular color variation for point light sources and significantly reduce color variation for extended light

  6. Unidirectional visible light communication and illumination with LEDs

    NARCIS (Netherlands)

    Li, S.; Pandharipande, A.; Willems, F.M.J.

    2016-01-01

    Visible light communication (VLC) with light emitting diodes (LEDs) has attracted interest for interactive and networked lighting control, and consumer infotainment applications. In this paper, we propose an LED system for jointly achieving unidirectional VLC while providing flicker-free

  7. Tuning the colour of white polymer light emitting diodes

    NARCIS (Netherlands)

    Kok, M.M. de; Sarfert, W.; Paetzold, R.

    2010-01-01

    Colour tuning of white polymer light emitting diode (LED) light sources can be attained by various methods at various stages in the production process of the lamps and/or by the design of the active material incorporated in the LEDs. In this contribution we will describe the methods and discuss the

  8. A white–cyan-red LED system for low correlated colour temperature lighting

    DEFF Research Database (Denmark)

    Chakrabarti, Maumita; Thorseth, Anders; Corell, Dennis Dan

    2015-01-01

    A white LED complemented by cyan and red LEDs is a good candidate for achieving high colour rendering at low correlated colour temperatures. This is usually very difficult with commercially available white LEDs. In addition, the system is able to replace incandescent lighting in many applications...... to 2400 K. Within this range the white light is characterized by a high general colour rendering index (Ra>90), special colour rendering indices for saturated red objects (R9>85), and low chromaticity distance (Duv) from the Planckian locus (Duv

  9. High efficiency nitride based phosphores for white LEDs

    NARCIS (Netherlands)

    Li, Yuan Qiang; Hintzen, H.T.J.M.

    2008-01-01

    In this overview paper, novel rare-earth doped silicon nitride based phosphors for white LEDs applications have been demonstrated. The luminescence properties of orange-red-emitting phosphors (M2Si5N8:Eu2+) and green-to-yellow emitting phosphors (MSi2N2O2:Eu2+, M = Ca, Sr, Ba) are discussed in

  10. Fluorescent SiC as a new material for white LEDs

    DEFF Research Database (Denmark)

    Syväjärvi, M.; Müller, J.; Sun, J. W.

    2012-01-01

    Current III–V-based white light-emitting diodes (LEDs) are available. However, their yellow phosphor converter is not efficient at high currents and includes rare-earth metals, which are becoming scarce. In this paper, we present the growth of a fluorescent silicon carbide material that is obtained...

  11. Two-way visible light communication and illumination with LEDs

    NARCIS (Netherlands)

    Li, S.; Pandharipande, A.; Willems, F.M.J.

    2017-01-01

    Visible light communications (VLC) with light-emitting diodes (LEDs) has attracted applications, such as data communications, lighting control, and light interaction. In this paper, we propose a system by which two LED devices are used for two-way VLC while also providing illumination. We consider

  12. Quantification and analysis of color stability based on thermal transient behavior in white LED lamps.

    Science.gov (United States)

    Nisa Khan, M

    2017-09-20

    We present measurement and analysis of color stability over time for two categories of white LED lamps based on their thermal management scheme, which also affects their transient lumen depreciation. We previously reported that lumen depreciation in LED lamps can be minimized by properly designing the heat sink configuration that allows lamps to reach a thermal equilibrium condition quickly. Although it is well known that lumen depreciation degrades color stability of white light since color coordinates vary with total lumen power by definition, quantification and characterization of color shifts based on thermal transient behavior have not been previously reported in literature for LED lamps. Here we provide experimental data and analysis of transient color shifts for two categories of household LED lamps (from a total of six lamps in two categories) and demonstrate that reaching thermal equilibrium more quickly provides better stability for color rendering, color temperature, and less deviation of color coordinates from the Planckian blackbody locus line, which are all very important characterization parameters of color for white light. We report for the first time that a lamp's color degradation from the turn-on time primarily depends on thermal transient behavior of the semiconductor LED chip, which experiences a wavelength shift as well as a decrease in its dominant wavelength peak value with time, which in turn degrades the phosphor conversion. For the first time, we also provide a comprehensive quantitative analysis that differentiates color degradation due to the heat rise in GaN/GaInN LED chips and subsequently the boards these chips are mounted on-from that caused by phosphor heating in a white LED module. Finally, we briefly discuss why there are some inevitable trade-offs between omnidirectionality and color and luminous output stability in current household LED lamps and what will help eliminate these trade-offs in future lamp designs.

  13. Colorimetry and efficiency of white LEDs: Spectral width dependence

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, Elaine; Edwards, Paul R.; Martin, Robert W. [Department of Physics, SUPA, Strathclyde University, Glasgow (United Kingdom)

    2012-03-15

    The potential colour rendering capability and efficiency of white LEDs constructed by a combination of individual red, green and blue (RGB) LEDs are analysed. The conventional measurement of colour rendering quality, the colour rendering index (CRI), is used as well as a recently proposed colour quality scale (CQS), designed to overcome some of the limitations of CRI when narrow-band emitters are being studied. The colour rendering performance is maximised by variation of the peak emission wavelength and relative intensity of the component LEDs, with the constraint that the spectral widths follow those measured in actual devices. The highest CRI achieved is 89.5, corresponding to a CQS value of 79, colour temperature of 3800 K and a luminous efficacy of radiation (LER) of 365 lm/W. By allowing the spectral width of the green LED to vary the CRI can be raised to 90.9, giving values of 82.5 and 370 lm/W for the CQS and LER, respectively. The significance of these values are discussed in terms of optimising the possible performance of RGB LEDs. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. The use of light-emitting diodes (LED in commercial layer production

    Directory of Open Access Journals (Sweden)

    R Borille

    2013-06-01

    Full Text Available Artificial lighting is one of the most powerful management tools available to commercial layer producers. Artificial light allows anticipating or delaying the beginning of lay, improving egg production, and optimizing feed efficiency. This study aimed at comparing the performance of commercial layers submitted to lighting using different LED colors or conventional incandescent lamps. The study was carried out in a layer house divided in isolated environments in order to prevent any influenced from the neighboring treatments. In total, 360 Isa Brown layers, with an initial age of 56 weeks, were used. The following light sources were used: blue LED, yellow LED, green LED, red LED, white LED, and 40W incandescent light. Birds in all treatment were submitted to a 17-h continuous lighting program, and were fed a corn and soybean meal-based diet. A completely randomized experimental design with subplots was applied, with 24 treatments (six light sources and four periods of three replicates. Egg production (% was significantly different (p0.05 by light source. It was concluded that the replacement of incandescent light bulbs by white and red LEDs does not cause any negative effect on the egg production of commercial layers.

  15. Solution processable inverted structure ZnO-organic hybrid heterojuction white LEDs

    Science.gov (United States)

    Bano, N.; Hussain, I.; Soomro, M. Y.; EL-Naggar, A. M.; Albassam, A. A.

    2018-05-01

    Improving luminance efficiency and colour purity are the most important challenges for zinc oxide (ZnO)-organic hybrid heterojunction light emitting diodes (LEDs), affecting their large area applications. If ZnO-organic hybrid heterojunction white LEDs are fabricated by a hydrothermal method, it is difficult to obtain pure and stable blue emission from PFO due to the presence of an undesirable green emission. In this paper, we present an inverted-structure ZnO-organic hybrid heterojunction LED to avoid green emission from PFO, which mainly originates during device processing. With this configuration, each ZnO nanorod (NR) forms a discrete p-n junction; therefore, large-area white LEDs can be designed without compromising the junction area. The configuration used for this novel structure is glass/ZnO NRs/PFO/PEDOT:PSS/L-ITO, which enables the development of efficient, large-area and low-cost hybrid heterojunction LEDs. Inverted-structure ZnO-organic hybrid heterojunction white LEDs offer several improvements in terms of brightness, size, colour, external quantum efficiency and a wider applicability as compared to normal architecture LEDs.

  16. High Output LED-Based Profile Lighting Fixture

    DEFF Research Database (Denmark)

    Török, Lajos; Beczkowski, Szymon; Munk-Nielsen, Stig

    2011-01-01

    Recent developments in power light emitting diode (LED) industry have made LEDs suitable for being efficiently used in high intensity lighting fixtures instead of the commonly used high intensity discharge (HID) lamps. A high output LEDbased profile-light fixture is presented in this paper...

  17. POWERED LED LIGHTING SUPPLIED FROM PV CELLS

    Directory of Open Access Journals (Sweden)

    Tirshu M.

    2011-12-01

    Full Text Available The paper deals with practical realization of efficient lighting system based on LED’s of 80W total power mounted on corridor ceiling total length of which is 120m and substitutes existing traditional lighting system consisting of 29 lighting blocks with 4 fluorescent lamps each of them and summary power 2088W. Realized lighting system is supplied from two photovoltaic panels of power 170W. Generated energy by PV cells is accumulated in two accumulators of 75Ah capacity and from battery by means of specialized convertor is applied to lighting system. Additionally, paper present data measured by digital weather station (solar radiation and UV index, which is mounted near of PV cells and comparative analyze of solar energy with real energy generated by PV cells is done. Measured parameters by digital weather station are stored by computer in on-line mode.

  18. Development of Efficient UV-LED Phosphor Coatings for Energy Saving Solid State Lighting

    International Nuclear Information System (INIS)

    Uwe Happek

    2006-01-01

    The University of Georgia, in collaboration with GE Global Research, has investigated the relevant quenching mechanism of phosphor coatings used in white light devices based on UV LEDs. The final goal of the project was the design and fabrication of a high-efficacy white light UV-LED device through improved geometry and optimized phosphor coatings. At the end of the research period, which was extended to seamlessly carry over the research to a follow-up program, we have demonstrated a two-fold improvement in the conversion efficiency of a white light LED device, where the increase efficacy is due to both improved phosphor quantum efficiency and lamp geometry. Working prototypes have been displayed at DOE sponsored meetings and during the final presentation at the DOE Headquarters in Washington, DC. During the first phase of the project, a fundamental understanding of quenching processes in UV-LEDs was obtained, and the relationships that describe the performance of the phosphor as a function of photon flux, temperature, and phosphor composition were established. In the second phase of the project, these findings were then implemented to design the improved UV-LED lamp. In addition, our research provides a road map for the design of efficient white light LEDs, which will be an important asset during a follow-up project led by GE

  19. Exterior LED Lighting Projects at Princeton University

    Energy Technology Data Exchange (ETDEWEB)

    Davis, Robert G. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Evans, William [Princeton Univ., NJ (United States); Murphy, Arthur T. [Princeton Univ., NJ (United States); Perrin, Tess E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2015-10-01

    For this report, PNNL / the U.S. Department of Energy (DOE) studied a series of past exterior lighting projects at Princeton, in order to document Princeton’s experiences with solid-state lighting (SSL) and the lessons learned along the way, and to show how their approach to SSL projects evolved as their own learning expanded and as the products available improved in performance and sophistication.

  20. Efficient light harvesting from flexible perovskite solar cells under indoor white light-emitting diode illumination

    NARCIS (Netherlands)

    Lucarelli, G.; Di Giacomo, F.; Zardetto, V.; Creatore, M.; Brown, T.M.

    2017-01-01

    This is the first report of an investigation on flexible perovskite solar cells for artificial light harvesting by using a white light-emitting diode (LED) lamp as a light source at 200 and 400 lx, values typically found in indoor environments. Flexible cells were developed using either

  1. Control and Driving Methods for LED Based Intelligent Light Sources

    OpenAIRE

    Beczkowski, Szymon

    2012-01-01

    High power light-emitting diodes allow the creation of luminaires capable of generating saturated colour light at very high efficacies. Contrary to traditional light sources like incandescent and high-intensity discharge lamps, where colour is generated using filters, LEDs use additive light mixing, where the intensity of each primary colour diode has to be adjusted to the needed intensity to generate specified colour. The function of LED driver is to supply the diode with power needed to ach...

  2. LED-technologies for bright light therapy

    Science.gov (United States)

    Kukhta, M. S.; Sidorenko, E. V.; Simutkin, G. G.; Khomushku, O. M.; Glushkov, G. S.

    2018-05-01

    The significance of the LED-based medical equipment design is caused by the need to make up for the sunshine shortfall in many areas of Russia (Siberia, the Far East, the Extreme North) that will allow reducing dramatically the risk of seasonal affective disorders. The sunshine is the essential synchronizer of the human biological rhythms, the abnormality of which plays an important role in the seasonal affective disorder nature. The study allows proving the object database development able to meet the human demand for a comfortable and high-quality placemaking as well as the health potential recoverability.

  3. Improving “color rendering” of LED lighting for the growth of lettuce

    Science.gov (United States)

    Han, Tao; Vaganov, Vitaliy; Cao, Shixiu; Li, Qiang; Ling, Lili; Cheng, Xiaoyao; Peng, Lingling; Zhang, Congzhi; Yakovlev, Alexey N.; Zhong, Yang; Tu, Mingjing

    2017-04-01

    Light plays a vital role on the growth and development of plant. On the base of white light with high color rendering to the benefit of human survival and life, we proposed to improve “color rendering” of LED lighting for accelerating the growth of lettuce. Seven spectral LED lights were adopted to irradiate the lettuces under 150 μmol·m-2·s-1 for a 16 hd-1 photoperiod. The leaf area and number profiles, plant biomass, and photosynthetic rate under the as-prepared LED light treatments were investigated. We let the absorption spectrum of fresh leaf be the emission spectrum of ideal light and then evaluate the “color rendering” of as-prepared LED lights by the Pearson product-moment correlation coefficient and CIE chromaticity coordinates. Under the irradiation of red-yellow-blue light with high correlation coefficient of 0.587, the dry weights and leaf growth rate are 2-3 times as high as the sharp red-blue light. The optimized LED light for lettuce growth can be presumed to be limited to the angle (about 75°) between the vectors passed through the ideal light in the CIE chromaticity coordinates. These findings open up a new idea to assess and find the optimized LED light for plant growth.

  4. Evaluation of OLED and edge-lit LED lighting panels

    Science.gov (United States)

    Mou, Xi; Narendran, Nadarajah; Zhu, Yiting; Freyssinier, Jean Paul

    2016-09-01

    Solid-state lighting (SSL) offers a new technology platform for lighting designers and end-users to illuminate spaces with low energy demand. Two types of SSL sources include organic light-emitting diodes (OLEDs) and light-emitting diodes (LEDs). OLED is an area light source, and its primary competing technology is the edge-lit LED panel. Generally, both of these technologies are considered similar in shape and appearance, but there is little understanding of how people perceive discomfort glare from large area light sources. The objective of this study was to evaluate discomfort glare for the two lighting technologies under similar operating conditions by gathering observers' reactions. The human factors study results showed no statistically significant difference in human response to discomfort glare between OLED and edge-lit LED panels when the two light sources produced the same lighting stimulus. This means both technologies appeared equally glary beyond a certain luminance.

  5. Final report LED solutions for public lighting; Eindrapportage LED oplossingen voor openbare verlichting

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2010-04-15

    This report examines if and how LED can be used for public lighting on a large scale. Pilot projects in 29 municipalities were assessed to test the usefulness of LED lighting. This final report provides answers to the questions that relate to the feasibility of the deployment of LED in public lighting and provides some practical pointers. [Dutch] Er is onderzocht of, en zo ja op welke wijze, LED grootschalig toegepast kan worden in de openbare verlichting (OVL). In 29 gemeenten in Nederland zijn proefprojecten geevalueerd om LED verlichting te toetsen op bruikbaarheid. Deze eindrapportage geeft antwoord op vragen die betrekking hebben op de haalbaarheid van de toepassing van LED binnen de OVL en geeft wat praktische aandachtspunten.

  6. On-off switching patterns for smart LED lighting

    NARCIS (Netherlands)

    Linnartz, J.P.M.G.; Schenk, T.C.W.; Feri, L.; Yang, Hongming; Tjalkens, T.J.; Willems, F.M.J.

    2009-01-01

    This paper formulates a new communication problem for smart LED lighting sys tems designed for light effect control. It introduces the key requirements imposed on the design of the LED driving sequences, which include multiple access, arbi trary duty cycle and no disturbance caused on the normal

  7. Interior LED Lighting Technology. Navy Energy Technology Validation (Techval) Program

    Science.gov (United States)

    2015-09-01

    usually on most of the time. • Consider replacing existing CFL, high-intensity discharge (HID), or halogen lamp light fixtures/ lamps with LED fixtures... lamps . What is the Technology? An LED is a semiconductor-diode that emits light when power is applied. A driver is used, much as a ballast, to...available in integrated luminaires that can be used to replace existing luminaires. LEDs are also available as direct replacement lamps for many

  8. Plant growth regulation by the light of LEDs; LED ko wo tsukatta shokubutsu saibai gijutsu

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, H. [Mitsubishi Chemical Co., Tokyo (Japan). Yokohama Research Center

    1996-03-01

    Light Emitting Diode (LED) has not only an excellent display function for the luminescent device but also a superior feature without other lamps as light source for plant growth. It was National Aeronautics and Space Administration (NASA) to find out such merit for this light source for plant growth and try at first to use for plant growth at the space. They began to examine the LED application to the light source for the plant growth at the space since a stage at high cost of the LED, to develop some researches centered at cultivation of lettuce, wheat, and others. Finding out future possibility of cost-down of the LEDs on the cost/performance and large merits of the LEDs for control of the plant growth and plant physiology, authors have conducted some cultivation experiments of the plants using the LEDs for light source some years ago. In this papers, characterizations, actual possibility, and future developments of the LEDs for the light sources of the plant growth, are introduced. 5 refs., 4 figs.

  9. Accelerated Stress Testing of Multi-Source LED Products: Horticulture Lamps and Tunable-White Modules

    Energy Technology Data Exchange (ETDEWEB)

    Lynn Davis, Kelley Rountree, Karmann Mills

    2018-03-30

    This report discusses the use of accelerated stress testing (AST) to provide insights into the long-term behavior of commercial products utilizing different types of mid-power LEDs (MP-LEDs) integrated into the same LED module. Test results are presented from two commercial lamps intended for use in horticulture applications and one tunable-white LED module intended for use in educational and office lighting applications. Each of these products is designed to provide a custom spectrum for their targeted applications and each achieves this goal in different ways. Consequently, a comparison of the long-term stability of these devices will provide insights regarding approaches that could be used to possibly lengthen the lifetime of SSL products.

  10. Intelligent control of dynamic LED lighting; Intelligent styring af dynamisk LED belysning. Slutrapport

    Energy Technology Data Exchange (ETDEWEB)

    Thorseth, A.; Corell, D.; Hansen, Soeren S.; Dam-Hansen, C.; Petersen, Paul Michael

    2013-01-15

    The project has resulted in a prototype of a new intelligent lighting control system. The control system enables the end user to control his or her own local lighting environment (lighting zone) according to individual preferences and needs. The report provides a description of how the developed intelligent lighting system is composed and functions. The system is designed as a work lamp that enables dynamic change of the light color scheme according to a number of light control algorithms. It is specifically designed in relation to user tests of the intelligent lighting system, which is carried out in the final part of the project. An intelligent and advanced control of LED lighting was developed, which enables optimization of the user's light conditions in a given situation. Based on a number of known parameters, the system can control lighting so that at any time optimal light conditions are created, using a minimum of electric power. (LN)

  11. Effect of LED light on seeds of Capsicum annuum L. var. serrano

    Directory of Open Access Journals (Sweden)

    Alejandra María Moreno-Jiménez

    2017-11-01

    Full Text Available Serrano pepper (Capsicum annuum L. is a crop of economic, nutritional and medicinal importance; so it is necessary to increase its production and improve its characteristics. The objective of this research was to evaluate the stimulatory effect of light emitting diodes (LEDs on serrano pepper seedlings. Germination percentage, stem length, leaf width, leaf length, number of leaves, total chlorophyll content and carotenoid content were analyzed. The seeds were exposed to white, blue and red LED light, using fluorescent light as a control and a photoperiod of 11/13 hours. Once germinated, the seedlings continued with exposure to light for 30 days. After the laboratory conditions, the seedlings were transferred to a greenhouse for 60 days. The results show that there were no significant differences between LED light treatments on seed germination. The variables stem length, leaf width and leaf length, were favored with red light. Blue and red LEDs highlighted by increasing the number of leaves. Seedlings treated with blue light showed the highest content of photosynthetic pigments (chlorophyll= 0.84 mg g-1, carotenoid= 0.12 mg g-1. In conclusion, the red LED light is effective for the growth of serrano pepper seedlings, while the production of photosynthetic pigments was favored by blue LED light.   Keywords: peppers, light-emitting diodes, germination, growth, photosynthetic pigments

  12. Light Sterile Neutrinos: A White Paper

    DEFF Research Database (Denmark)

    Abazajian, K. N.; Acero, M. A.; Agarwalla, S. K.

    2012-01-01

    This white paper addresses the hypothesis of light sterile neutrinos based on recent anomalies observed in neutrino experiments and the latest astrophysical data.......This white paper addresses the hypothesis of light sterile neutrinos based on recent anomalies observed in neutrino experiments and the latest astrophysical data....

  13. Development of high-performance solar LED lighting system

    KAUST Repository

    Huang, B.J.; Wu, M.S.; Hsu, P.C.; Chen, J.W.; Chen, K.Y.

    2010-01-01

    The present study developed a high-performance charge/discharge controller for stand-alone solar LED lighting system by incorporating an nMPPO system design, a PWM battery charge control, and a PWM battery discharge control to directly drive the LED. The MPPT controller can then be removed from the stand-alone solar system and the charged capacity of the battery increases 9.7%. For LED driven by PWM current directly from battery, a reliability test for the light decay of LED lamps was performed continuously for 13,200 h. It has shown that the light decay of PWM-driven LED is the same as that of constant-current driven LED. The switching energy loss of the MOSFET in the PWM battery discharge control is less than 1%. Three solar-powered LED lighting systems (18 W, 100 W and 150 W LED) were designed and built. The long-term outdoor field test results have shown that the system performance is satisfactory with the control system developed in the present study. The loss of load probability for the 18 W solar LED system is 14.1% in winter and zero in summer. For the 100 W solar LED system, the loss of load probability is 3.6% in spring. © 2009 Elsevier Ltd. All rights reserved.

  14. Development of high-performance solar LED lighting system

    International Nuclear Information System (INIS)

    Huang, B.J.; Wu, M.S.; Hsu, P.C.; Chen, J.W.; Chen, K.Y.

    2010-01-01

    The present study developed a high-performance charge/discharge controller for stand-alone solar LED lighting system by incorporating an nMPPO system design, a PWM battery charge control, and a PWM battery discharge control to directly drive the LED. The MPPT controller can then be removed from the stand-alone solar system and the charged capacity of the battery increases 9.7%. For LED driven by PWM current directly from battery, a reliability test for the light decay of LED lamps was performed continuously for 13,200 h. It has shown that the light decay of PWM-driven LED is the same as that of constant-current driven LED. The switching energy loss of the MOSFET in the PWM battery discharge control is less than 1%. Three solar-powered LED lighting systems (18 W, 100 W and 150 W LED) were designed and built. The long-term outdoor field test results have shown that the system performance is satisfactory with the control system developed in the present study. The loss of load probability for the 18 W solar LED system is 14.1% in winter and zero in summer. For the 100 W solar LED system, the loss of load probability is 3.6% in spring.

  15. Development of high-performance solar LED lighting system

    KAUST Repository

    Huang, B.J.

    2010-08-01

    The present study developed a high-performance charge/discharge controller for stand-alone solar LED lighting system by incorporating an nMPPO system design, a PWM battery charge control, and a PWM battery discharge control to directly drive the LED. The MPPT controller can then be removed from the stand-alone solar system and the charged capacity of the battery increases 9.7%. For LED driven by PWM current directly from battery, a reliability test for the light decay of LED lamps was performed continuously for 13,200 h. It has shown that the light decay of PWM-driven LED is the same as that of constant-current driven LED. The switching energy loss of the MOSFET in the PWM battery discharge control is less than 1%. Three solar-powered LED lighting systems (18 W, 100 W and 150 W LED) were designed and built. The long-term outdoor field test results have shown that the system performance is satisfactory with the control system developed in the present study. The loss of load probability for the 18 W solar LED system is 14.1% in winter and zero in summer. For the 100 W solar LED system, the loss of load probability is 3.6% in spring. © 2009 Elsevier Ltd. All rights reserved.

  16. Scalable, Economical Fabrication Processes for Ultra-Compact Warm-White LEDs

    Energy Technology Data Exchange (ETDEWEB)

    Lowes, Ted [Cree, Inc., Durham, NC (United States)

    2016-01-31

    Conventional warm-white LED component fabrication consists of a large number of sequential steps which are required to incorporate electrical, mechanical, and optical functionality into the component. Each of these steps presents cost and yield challenges which multiply throughout the entire process. Although there has been significant progress in LED fabrication over the last decade, significant advances are needed to enable further reductions in cost per lumen while not sacrificing efficacy or color quality. Cree conducted a focused 18-month program to develop a new low-cost, high-efficiency light emitting diode (LED) architecture enabled by novel large-area parallel processing technologies, reduced number of fabrication steps, and minimized raw materials use. This new scheme is expected to enable ultra-compact LED components exhibiting simultaneously high efficacy and high color quality. By the end of the program, Cree fabricated warm-white LEDs with a room-temperature “instant on” efficacy of >135 lm/W at ~3500K and 90 CRI (when driven at the DOE baseline current density of 35 A/cm2). Cree modified the conventional LED fabrication process flow in a manner that is expected to translate into simultaneously high throughput and yield for ultra-compact packages. Building on its deep expertise in LED wafer fabrication, Cree developed these ultra-compact LEDs to have no compromises in color quality or efficacy compared to their conventional counterparts. Despite their very small size, the LEDs will also be robustly electrically integrated into luminaire systems with the same attach yield as conventional packages. The versatility of the prototype high-efficacy LED architecture will likely benefit solid-state lighting (SSL) luminaire platforms ranging from bulbs to troffers. We anticipate that the prototype LEDs will particularly benefit luminaires with large numbers of distributed compact packages, such as linear and area luminaires (e.g. troffers). The fraction of

  17. Fluorescein isothiocyanate and rhodamine B dye encapsulated mesoporous SiO2 for applications of blue LED excited white LED

    Science.gov (United States)

    Das, Sourav; Manam, J.

    2018-05-01

    In this work, the fluorescein isothiocyanate (FITC) and rhodamine B (RhB) dyes were encapsulated in mesoporous silica nanoparticles (MSNp). The MSNp-FITC-RhB nanohybrids phosphor showed a dichromatic PL emission at green region and orange region when excited at 460 nm. A Forster Resonance Energy Transfer (FRET) was observed from FITC to RhB. The materials were further characterized by XRD, FTIR, TEM, and temperature dependent photoluminescence. The CIE coordinates were tuned from greenish yellow to the orange region and quantum yield was reached 52.04% based on FRET. So by combining the MSNp-FITC-RhB nanohybrids phosphor with the blue LED chip, the white light emission with flexible Color Correlated Temperature and improved Color Rendering Index can be obtained.

  18. Monte carlo analysis of multicolour LED light engine

    DEFF Research Database (Denmark)

    Chakrabarti, Maumita; Thorseth, Anders; Jepsen, Jørgen

    2015-01-01

    light engine designed for white tuneable studio lighting. The measured sensitivities to the various factors influencing the colour uncertainty for similar system are incorporated. The method aims to provide uncertainties in the achievable chromaticity coordinates as output over the tuneable range, e...

  19. White organic light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Rosenow, Thomas Conrad

    2011-03-22

    Three approaches were taken in order to achieve reproducible and highly efficient white OLEDs with excellent colour quality. The first approach is based on the triplet harvesting concept. Otherwise unused triplet excitons are transferred from a fluorescent to a phosphorescent emitter with a smaller triplet energy. Because a blue emitter allowing for triplet transfer to a phosphorescent green emitter was not available, a model system for a three-colour white OLED was developed and investigated. This model device consists of the fluorescent blue emitter 4P-NPD and the phosphorescent emitters Ir(dhfpy){sub 2}acac and Ir(MDQ){sub 2}acac emitting in the yellow and red region, respectively. Here, it was shown that both phosphorescent emitters are excited by triplet diffusion and not by direct charge carrier recombination. The second approach is based on a hybrid white OLED with a single emission layer. This layer is a combination of a fluorescent blue and two phosphorescent emitters in a common matrix material. Because of the above mentioned lack of a blue emitter, which allows for triplet transfer to a green phosphorescent emitter, the concentrations of all emitters were chosen in a way that exciton transfer between the emitters was suppressed. The result is a non-radiative recombination of triplet excitons on the fluorescent blue emitter and an accordingly low quantum efficiency. However, a remarkable colour stability against varying brightness was achieved with this OLED. The most successful approach is based on a stacked OLED. Here, the concept of triplet harvesting is limited to triplet transfer between a fluorescent blue and a phosphorescent red emitter. The resulting spectral gap is filled by a full phosphorescent unit comprising the emission of a green and a yellow emitter, which is stacked on top of the triplet harvesting OLED. By individually optimising both units, it was possible to reach lighting relevant luminous efficacies up to {eta}{sub {nu}}=33 lm/W at

  20. White-light-emitting supramolecular gels.

    Science.gov (United States)

    Praveen, Vakayil K; Ranjith, Choorikkat; Armaroli, Nicola

    2014-01-07

    Let there be light, let it be white: Recent developments in the use of chromophore-based gels as scaffolds for the assembly of white-light-emitting soft materials have been significant. The main advantage of this approach lies in the facile accommodation of selected luminescent components within the gel. Excitation-energy-transfer processes between these components ultimately generate the desired light output. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. CMOS-compatible plenoptic detector for LED lighting applications.

    Science.gov (United States)

    Neumann, Alexander; Ghasemi, Javad; Nezhadbadeh, Shima; Nie, Xiangyu; Zarkesh-Ha, Payman; Brueck, S R J

    2015-09-07

    LED lighting systems with large color gamuts, with multiple LEDs spanning the visible spectrum, offer the potential of increased lighting efficiency, improved human health and productivity, and visible light communications addressing the explosive growth in wireless communications. The control of this "smart lighting system" requires a silicon-integrated-circuit-compatible, visible, plenoptic (angle and wavelength) detector. A detector element, based on an offset-grating-coupled dielectric waveguide structure and a silicon photodetector, is demonstrated with an angular resolution of less than 1° and a wavelength resolution of less than 5 nm.

  2. EVALUATION OF ADOPTION OF LED LIGHTING TECHNOLOGY IN MALAYSIA

    OpenAIRE

    Khorasanizadeh, Hasti

    2017-01-01

    Electrical energy consumption in Malaysia is rapidly increasing with illumination being the second largest contributor to this increment. Light Emitting Diode (LED) could be a viable option to reduce the illumination based energy consumption. LEDs are energy efficient and easier to recycle compared to traditional lighting sources such as incandescent and fluorescent lamps. They also have longer life time and lower failure rate. In this thesis, the feasibility of replacing...

  3. A new LED light source for display cases

    DEFF Research Database (Denmark)

    Dam-Hansen, Carsten; Petersen, Paul Michael

    Abstract: We report a new LED light source suitable for illumination of gold objects. It has a variable correlated color temperature from 2760 K to 2200 K with a high color rendering index up to 97.......Abstract: We report a new LED light source suitable for illumination of gold objects. It has a variable correlated color temperature from 2760 K to 2200 K with a high color rendering index up to 97....

  4. [Study on the safety of blue light leak of LED].

    Science.gov (United States)

    Shen, Chong-Yu; Xu, Zheng; Zhao, Su-Ling; Huang, Qing-Yu

    2014-02-01

    In this paper, the blue light properties of LED illumination devices have been investigated. Against the status quo of China's LED lighting, we measured the spectrum component of LED lamps and analyzed the photobiological safety under the current domestic and international standards GB/T 20145-2006/CIE S009/E: 2002 and IEC62471: 2006 standards as well as CTL-0744_2009-laser resolution, which provides the reference to the manufacture of LED lighting lamps as well as related safety standards and laws. If the radiance intensity of blue light in LED is lower than 100 W x m(-2) x Sr(-1), there is no harm to human eyes. LEDs will not cause harm to human eyes under normal use, but we should pay attention to the protection of special populations (children), and make sure that they avoid looking at a light source for a long time. The research has found that the blue-rich lamps can affect the human rule of work and rest, and therefore, the LED lamps with color temperature below 4 000 K and color rendering index of 80 are suitable for indoor use. At the same time, the lamps with different parameters should be selected according to the different distances.

  5. Colour differences in Caucasian and Oriental women's faces illuminated by white LED sources.

    Science.gov (United States)

    Melgosa, M; Richard, N; Fernández-Maloigne, C; Xiao, K; de Clermont-Gallerande, H; Jost-Boissard, S; Okajima, K

    2018-04-10

    To provide an approach to facial contrast, analysing CIELAB colour differences (ΔE* ab,10 ) and its components in women's faces from two different ethnic groups, illuminated by modern white light-emitting diodes (LEDs) or traditional illuminants recommended by the International Commission on Illumination (CIE). We performed spectrophotometric measurements of spectral reflectance factors on forehead and cheek of 87 young healthy women (50 Caucasians and 37 Orientals), plus 5 commercial red lipsticks. We considered a set of 10 white LED illuminants, representative of technologies currently available on the market, plus 8 main illuminants currently recommended by the CIE, representative of conventional incandescent, daylight, and fluorescent light sources. Under each of these 18 illuminants we analysed the magnitude and components of ΔE* ab,10 between Caucasian and Oriental women (considering cheek and forehead), as well as for cheek-forehead and cheek-lipsticks in Caucasian and Oriental women. Colour-inconstancy indices for cheek, forehead, and lipsticks were computed, assuming D65 and A as reference illuminants. ΔE* ab,10 between forehead and cheek were quantitatively and qualitatively different in Orientals and Caucasians, but discrepancies with respect to average values for 18 illuminants were small (1.5% and 5.0% for Orientals and Caucasians, respectively). ΔE* ab,10 between Caucasians and Orientals were also quantitatively and qualitatively different both for forehead and cheek, and discrepancies with respect to average values were again small (1.0% and 3.9% for forehead and cheek, respectively). ΔE* ab,10 between lipsticks and cheek were at least 2 times higher than those between forehead and cheek. Regarding ΔE* ab,10 between lipsticks and cheeks, discrepancies with respect to average values were in the range 1.5% - 12.3%, although higher values of up to 54.2% were found for a white RGB LED. This white RGB LED provided the highest average colour

  6. White Light Photorefractive Phase Zone Plates

    International Nuclear Information System (INIS)

    Yuan-Mei, Gao; Si-Min, Liu

    2008-01-01

    Incoherent white light from an incandescent source is employed to fabricate volume phase zone plates in LiNbO 3 : Fe, for the first time to our knowledge, which can guide and modulate the input white light or laser light. The diffractive efficiency of the white light volume phase zone plates fabricated can reach as high as 12%. In addition, we test the volume phase zone plates by a probe beam and find that the volume phase zone plate is present in the direction perpendicular to the c-axis and absent in the direction parallel to the c-axis. This directly proves the existence of photovoltaic photorefractive anisotropy of white light

  7. Response of Eustoma Leaf Phenotype and Photosynthetic Performance to LED Light Quality

    Directory of Open Access Journals (Sweden)

    Md Zohurul Kadir Roni

    2017-10-01

    Full Text Available In a controlled environment, light from light-emitting diodes (LEDs has been associated with affecting the leaf characteristics of Eustoma. LEDs help plant growth and development, yet little is known about photosynthetic performance and related anatomical features in the early growth stage of Eustoma leaves. In this study, we examined the effects of blue (B, red (R, and white (W LEDs on the photosynthetic performance of Eustoma leaves, as well as leaf morphology and anatomy including epidermal layer thickness, palisade cells, and stomatal characteristics. Leaves grown under B LEDs were thicker and had a higher chlorophyll content than those grown under the R and W LEDs. Leaves under B LEDs had greater net photosynthetic rates (A, stomatal conductance (gs, and transpiration rates (E, especially at a higher photon flux density (PPFD, that resulted in a decrease in the intercellular CO2 concentration (Ci, than leaves under the W and R LEDs. B LEDs resulted in greater abaxial epidermal layer thickness and palisade cell length and width than the R and W LED treatments. The palisade cells also developed a more cylindrical shape in response to the B LEDs. B LED leaves also showed greater guard cell length, breadth, and area, and stomatal density, than W or R LEDs, which may contribute to increased A, gs and E at higher PPFDs.

  8. Reliable LED Lighting Technologies: Key Factors and Procurement Guidance

    Energy Technology Data Exchange (ETDEWEB)

    Davis, Lynn; Arquit Niederberger, Anne

    2015-10-08

    Abstract— Lighting systems have the ability to transform the economic and educational infrastructure of disadvantaged communities, and eradicating “light poverty” has become one of the primary goals of the International Year of Light 2015. Solid-state lighting (SSL) technology, based on light-emitting diode (LED) light sources, has emerged as the next generation of lighting technology, with a current global market penetration of roughly 5%. This paper will report on recent research on understanding SSL lighting system reliability (failure modes, environmental stressors, electrical power quality); discuss the implications of SSL technology reliability for providing lighting services; and suggest practical approaches to ensure SSL reliability to benefit humanity. Among the key findings from this work is that LED sources can be extremely reliable, withstanding a broad range of environmental stresses without failure. Nonetheless, SSL lighting systems can have a negative impact on electrical power reliability, as well as on the affordability of lighting services, without attention to the quality of the accompanying power infrastructure. It is therefore critical to ensure that the performance of the power supply electronics used in lighting systems is matched to the quality of the power source, when evaluating energy efficient lighting choices.

  9. Surface defect assisted broad spectra emission from CdSe quantum dots for white LED application

    Science.gov (United States)

    Samuel, Boni; Mathew, S.; Anand, V. R.; Correya, Adrine Antony; Nampoori, V. P. N.; Mujeeb, A.

    2018-02-01

    This paper reports, broadband photoluminescence from CdSe quantum dots (QDs) under the excitation of 403 nm using fluorimeter and 403 nm CW laser excitation. The broad spectrum obtained from the colloidal quantum dots was ranges from 450 nm to 800 nm. The broadness of the spectra was attributed to the merging of band edge and defect driven emissions from the QDs. Six different sizes of particles were prepared via kinetic growth method by using CdO and elemental Se as sources of Cd and Se respectively. The particle sizes were measured from TEM images. The size dependent effect on broad emission was also studied and the defect state emission was found to be predominant in very small QDs. The defect driven emission was also observed to be redshifted, similar to the band edge emission, due to quantum confinement effect. The emission corresponding to different laser power was also studied and a linear relation was obtained. In order to study the colour characteristics of the emission, CIE chromaticity coordinate, CRI and CCT of the prepared samples were measured. It is observed that, these values were tunable by the addition of suitable intensity of blue light from the excitation source to yield white light of various colour temperatures. The broad photoluminescence spectrum of the QDs, were compared with that of a commercially available white LED. It was found that the prepared QDs are good alternatives for the phosphor in phosphor converted white LEDs, to provide good spectral tunability.

  10. LED Light to improve Strawberry Flavour, Quality and Production

    NARCIS (Netherlands)

    Hanenberg, M.A.A.; Janse, J.; Verkerke, W.

    2016-01-01

    A current demonstration in the greenhouses of Wageningen UR in Bleiswijk (the Netherlands) shows positive results of LED light on the quality and production of strawberries (Fragaria x ananassa). In this demonstration two strawberry cultivars, Elsanta and Sonata, are exposed to three different light

  11. Occupancy-based illumination control of LED lighting systems

    NARCIS (Netherlands)

    Caicedo Fernandez, D.R.; Pandharipande, A.; Leus, G.

    2011-01-01

    Light emitting diode (LED)-based systems are considered to be the future of lighting. We consider the problem of energy-efficient illumination control of such systems. Energy-efficient system design is based on two aspects: localised information on occupancy and optimisation of dimming levels of the

  12. Current-voltage model of LED light sources

    DEFF Research Database (Denmark)

    Beczkowski, Szymon; Munk-Nielsen, Stig

    2012-01-01

    Amplitude modulation is rarely used for dimming light-emitting diodes in polychromatic luminaires due to big color shifts caused by varying magnitude of LED driving current and nonlinear relationship between intensity of a diode and driving current. Current-voltage empirical model of light...

  13. Monochromic radiation through light-emitting diode (LED positively augments in vitro shoot regeneration in Orchid (Dendrobium sonia

    Directory of Open Access Journals (Sweden)

    Vandita Billore

    2017-07-01

    Full Text Available Monochromatic lights emitted by light-emitting diodes (LEDs have generated great interest for efficient and controlled growth in vitro, especially of plants which are endangered or require specific intensity and wavelength of light. In the present study, we have evaluated the effect of monochromatic LEDs on in vitro morphogenesis: growth, proliferation of shoot cultures, and rooting of Dendrobium sonia. Different light sources viz. white LEDs (W, blue LEDs (B, yellow LEDs (Y and red LEDs (R were tested under photoperiod of 16 h of exposure and 8 h of dark. The frequency of morphogenesis depended on the wavelength of the applied monochromatic light. Higher wavelength monochromatic light (yellow light was observed to induce higher shoot proliferation (98%, early PLB (protocorm-like bodies formation, differentiation into green buds and shoot initiation as compared to red, blue and white light treatments. Yellow light also yielded higher number of shoots per explants (29 shoots/explant than red, blue and white light treatments. The results suggest that the monochromatic light sources stimulate morphogenic effects on in vitro culture of Dendrobium sonia, and that yellow light treatment can be used to enhance the efficiency of micropropagation.

  14. Effect of Led Lighting Colors for Laying Japanese Quails

    Directory of Open Access Journals (Sweden)

    KC Nunes

    Full Text Available ABSTRACT Time of exposure and light intensity rearing house may affect the performance and egg quality of laying quails. This research aimed at evaluating the live performance, egg quality, biometry of the reproductive system, and the gastrointestinal tract of Japanese quails (Coturnix coturnix japonica exposed to artificial light-emitting diodes (LED of different colors in comparison with fluorescent lamps. A total of 240 Japanese quails were distributed in completely randomized experimental design with four treatments (fluorescent lamp, and green, red, or blue LED lamps with six replicates of 10 birds each. Average egg weight and eggshell thickness were different (p0.05. The oviduct of 64-d-old hens exposed to green LED lighting was shorter (p<0.05 than those exposed to the fluorescent lamp. Red LED can be used to replace the fluorescent lamps, as they promote the same live performance, egg quality, and morphological development of the reproductive tract of laying Japanese quails.

  15. Anti-glare LED lamps with adjustable illumination light field.

    Science.gov (United States)

    Chen, Yung-Sheng; Lin, Chung-Yi; Yeh, Chun-Ming; Kuo, Chie-Tong; Hsu, Chih-Wei; Wang, Hsiang-Chen

    2014-03-10

    We introduce a type of LED light-gauge steel frame lamp with an adjustable illumination light field that does not require a diffusion plate. Base on the Monte Carlo ray tracing method, this lamp has a good glare rating (GR) of 17.5 at 3050 lm. Compared with the traditional LED light-gauge steel frame lamp (without diffusion plate), the new type has low GR. The adjustability of the illumination light field could improve the zebra effect caused by the inadequate illumination light field of the lamp. Meanwhile, we adopt the retinal image analysis to discuss the influence of GR on vision. High GR could reflect stray light on the retinal image, which will reduce vision clarity and hasten the feeling of eye fatigue.

  16. Photoprotection and photoreception of intraocular lenses under xenon and white LED illumination.

    Science.gov (United States)

    Artigas, J M; Navea, A; García-Domene, M C; Artigas, C; Lanzagorta, A

    2016-05-01

    To analyze the photoprotection and phototransmission that various intraocular lenses (IOLs) provide under the illumination of a xenon (Xe) lamp and white LEDs (light emitting diode). The spectral transmission curves of six representative IOLs were measured using a Perkin-Elmer Lambda 35 UV/VIS spectrometer. Various filtering simulations were performed using a Xe lamp and white LEDs. The spectral emissions of these lamps were measured with an ILT-950 spectroradiometer. The IOLs analyzed primarily show transmission of nearly 100% in the visible spectrum. In the ultraviolet (UV) region, the filters incorporated in the various IOLs did not filter equally, and some of them let an appreciable amount of UV through. The Xe lamp presented a strong emission of ultraviolet A (UVA), and its emission under 300nm was not negligible. The white LED did not present an appreciable emission under 380nm. The cut-off wavelength of most filters is between 380 and 400nm (Physiol Hydriol60C(®), IOLTECH E4T(®), Alcon SA60AT(®), Alcon IQ SN60WF(®)), so that their UV protection is very effective. Nonetheless, the IOL OPHTEC Oculaid(®) contains a filter that, when a Xe lamp is used, lets through up to 20% for 350nm and up to 15% for 300nm, which at this point is ultraviolet B (UVB). The OPHTEC(®) Artisan IOL has a transmission peak below 300nm, which must be taken into account under Xe illumination. White LEDs do not emit energy below 380nm, so no special protection is required in the UV region. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

  17. Light out-coupling from LEDs by means of metal nanoparticles; Lichtauskopplung aus LEDs mittels Metallnanoteilchen

    Energy Technology Data Exchange (ETDEWEB)

    Goehler, Tino

    2010-12-17

    The external quantum efficiency of light-emitting diodes (LEDs) based on Al- GaAs/InGaAlP is limited by total internal reflection because of the high refractive index (typically between 3 and 4) of the semiconductor. Metal nanoparticles (MNP) deposited on the surface of the LED can be used as dipole scatterers in order to enhance the emission of the LED. In this thesis, first, single gold nanoparticles of various sizes deposited on such an LED were investigated. A clear enhancement is detected as long as the dipole plasmon resonance of the particle is at a shorter wavelength than the LED emission. If the plasmon resonance coincides with the LED emission or is at a larger wavelength, the enhancement turns into suppression. Numerical simulations indicate that this latter effect is mainly caused by the particle quadrupole resonance producing extra absorption. Arrays of MNPs can be produced by a special mask technique called ''Fischer pattern nanolithography'' and manipulated in shape and size by additional steps. Originally, the MNPs produced by this technique are triangular in shape and turn out to suppress the LED emission. After transformation of the particles to spheres, a clear enhancement was detected. Light that would otherwise remain trapped inside the substrate is coupled out by resonant plasmonic scattering. Investigations on analogous structures on a transparent high-index material (GaP) indicate a stronger coupling between the particles than expected on the basis of literature data. (orig.)

  18. Fuselage mounted anti-collision lights utilizing high power LEDs

    Science.gov (United States)

    Lundberg, John; Machi, Nicolo; Mangum, Scott; Singer, Jeffrey

    2005-09-01

    As LEDs continue to improve in efficacy and total light output, they are increasingly finding their way in to new applications in the aviation industry as well as adjacent markets. One function that is particularly challenging and may reap substantial benefits from this new technology is the fuselage mounted anti-collision light. Anti-collision lights provide conspicuity for the aircraft by periodically emitting bright flashes of light. The color, light distribution and intensity levels for these lights are all closely regulated through Federal Aviation Regulation (FAR) documents. These lighting requirements, along with thermal, environmental and aerodynamic requirements, drive the overall design. In this paper, we will discuss the existing technologies used in anti-collision lights and the advantages and challenges associated with an LED solution. Particular attention will be given to the optical, thermal, electrical and aerodynamic aspects associated with an LED approach. A specific case study will be presented along with some of the challenges that have arisen during the design process. These challenges include the addition of an integrated covert anti-collision lighting.

  19. Application of high-brightness LEDs in aircraft position lights

    Science.gov (United States)

    Machi, Nicolo; Mangum, Scott; Singer, Jeffrey M.

    2004-10-01

    Solid state lighting devices have made their way into a number of niche markets and continue to make inroads into other markets as their price / performance ratios improve. One of these markets is aviation lighting. Although this paper will focus on the use of LEDs for aircraft position lights, much of the discussion is applicable to other installations on the interior and exterior of the aircraft. The color, light distribution and intensity levels for a position light are all closely regulated through Code of Federal Regulation (CFR; formerly Federal Aviation Regulation (FAR)) documents. These lighting requirements, along with harsh thermal and environmental requirements, drive the design. In this paper, we will look at these requirements and discuss what is required in order to use LEDs for this type of application. We will explore the optical, thermal and electrical issues associated with the use of LEDs for position lights and examine the specific case study of the Astreon forward position lights. Finally, we will discuss some of the challenges that we see with solid state lighting in current and future aircraft applications.

  20. Laser induced white lighting of tungsten filament

    Science.gov (United States)

    Strek, W.; Tomala, R.; Lukaszewicz, M.

    2018-04-01

    The sustained bright white light emission of thin tungsten filament was induced under irradiation with focused beam of CW infrared laser diode. The broadband emission centered at 600 nm has demonstrated the threshold behavior on excitation power. Its intensity increased non-linearly with excitation power. The emission occurred only from the spot of focused beam of excitation laser diode. The white lighting was accompanied by efficient photocurrent flow and photoelectron emission which both increased non-linearly with laser irradiation power.

  1. A summary of LED lighting impacts on health

    Directory of Open Access Journals (Sweden)

    Cosmin Ticleanu

    2017-06-01

    Full Text Available Lighting can affect the health of people in buildings. This goes beyond the safety aspects of providing enough illumination to see by; lighting affects mood and human circadian rhythms, while poor lighting can cause glare, headaches, eyestrain, aches and pains associated with poor body posture or, in extreme cases, skin conditions and various types of sight loss. These aspects ought to be considered by designers and building owners and occupiers in order to improve the lit environment and use adequate lighting and lighting controls that meet the recommendations of codes and standards. Various types of lighting can have different impacts depending on their spectral, optical and electrical characteristics. This paper discusses potential impacts of LED lighting on human health, and is based on a recent BRE review of research investigating the most typical effects of lighting on human health.

  2. Prognostics-based qualification of high-power white LEDs using Lévy process approach

    Science.gov (United States)

    Yung, Kam-Chuen; Sun, Bo; Jiang, Xiaopeng

    2017-01-01

    Due to their versatility in a variety of applications and the growing market demand, high-power white light-emitting diodes (LEDs) have attracted considerable attention. Reliability qualification testing is an essential part of the product development process to ensure the reliability of a new LED product before its release. However, the widely used IES-TM-21 method does not provide comprehensive reliability information. For more accurate and effective qualification, this paper presents a novel method based on prognostics techniques. Prognostics is an engineering technology predicting the future reliability or determining the remaining useful lifetime (RUL) of a product by assessing the extent of deviation or degradation from its expected normal operating conditions. A Lévy subordinator of a mixed Gamma and compound Poisson process is used to describe the actual degradation process of LEDs characterized by random sporadic small jumps of degradation degree, and the reliability function is derived for qualification with different distribution forms of jump sizes. The IES LM-80 test results reported by different LED vendors are used to develop and validate the qualification methodology. This study will be helpful for LED manufacturers to reduce the total test time and cost required to qualify the reliability of an LED product.

  3. Progress in extremely high brightness LED-based light sources

    Science.gov (United States)

    Hoelen, Christoph; Antonis, Piet; de Boer, Dick; Koole, Rolf; Kadijk, Simon; Li, Yun; Vanbroekhoven, Vincent; Van De Voorde, Patrick

    2017-09-01

    Although the maximum brightness of LEDs has been increasing continuously during the past decade, their luminance is still far from what is required for multiple applications that still rely on the high brightness of discharge lamps. In particular for high brightness applications with limited étendue, e.g. front projection, only very modest luminance values in the beam can be achieved with LEDs compared to systems based on discharge lamps or lasers. With dedicated architectures, phosphor-converted green LEDs for projection may achieve luminance values up to 200-300 Mnit. In this paper we report on the progress made in the development of light engines based on an elongated luminescent concentrator pumped by blue LEDs. This concept has recently been introduced to the market as ColorSpark High Lumen Density LED technology. These sources outperform the maximum brightness of LEDs by multiple factors. In LED front projection, green LEDs are the main limiting factor. With our green modules, we now have achieved peak luminance values of 2 Gnit, enabling LED-based projection systems with over 4000 ANSI lm. Extension of this concept to yellow and red light sources is presented. The light source efficiency has been increased considerably, reaching 45-60 lm/W for green under practical application conditions. The module architecture, beam shaping, and performance characteristics are reviewed, as well as system aspects. The performance increase, spectral range extensions, beam-shaping flexibility, and cost reductions realized with the new module architecture enable a breakthrough in LED-based projection systems and in a wide variety of other high brightness applications.

  4. Life-Cycle Assessment of Energy and Environmental Impacts of LED Lighting Products Part 2: LED Manufacturing and Performance

    Energy Technology Data Exchange (ETDEWEB)

    Scholand, Michael; Dillon, Heather E.

    2012-05-01

    Part 2 of the project (this report) uses the conclusions from Part 1 as a point of departure to focus on two objectives: producing a more detailed and conservative assessment of the manufacturing process and providing a comparative LCA with other lighting products based on the improved manufacturing analysis and taking into consideration a wider range of environmental impacts. In this study, we first analyzed the manufacturing process for a white-light LED (based on a sapphire-substrate, blue-light, gallium-nitride LED pumping a yellow phosphor), to understand the impacts of the manufacturing process. We then conducted a comparative LCA, looking at the impacts associated with the Philips Master LEDbulb and comparing those to a CFL and an incandescent lamp. The comparison took into account the Philips Master LEDbulb as it is now in 2012 and then projected forward what it might be in 2017, accounting for some of the anticipated improvements in LED manufacturing, performance and driver electronics.

  5. Design of High Efficiency Illumination for LED Lighting

    OpenAIRE

    Chang, Yong-Nong; Cheng, Hung-Liang; Kuo, Chih-Ming

    2013-01-01

    A high efficiency illumination for LED street lighting is proposed. For energy saving, this paper uses Class-E resonant inverter as main electric circuit to improve efficiency. In addition, single dimming control has the best efficiency, simplest control scheme and lowest circuit cost among other types of dimming techniques. Multiple serial-connected transformers used to drive the LED strings as they can provide galvanic isolation and have the advantage of good current distribution against de...

  6. The Whiteness of Things and Light Scattering

    Science.gov (United States)

    Gratton, L. M.; Lopez-Arias, T.; Calza, G.; Oss, S.

    2009-01-01

    We discuss some simple experiments dealing with intriguing properties of light and its interaction with matter. In particular, we show how to emphasize that light reflection, refraction and scattering can provide a proper, physical description of human perception of the "colour" white. These experiments can be used in the classroom with an enquiry…

  7. Design of High Efficiency Illumination for LED Lighting

    Directory of Open Access Journals (Sweden)

    Yong-Nong Chang

    2013-01-01

    Full Text Available A high efficiency illumination for LED street lighting is proposed. For energy saving, this paper uses Class-E resonant inverter as main electric circuit to improve efficiency. In addition, single dimming control has the best efficiency, simplest control scheme and lowest circuit cost among other types of dimming techniques. Multiple serial-connected transformers used to drive the LED strings as they can provide galvanic isolation and have the advantage of good current distribution against device difference. Finally, a prototype circuit for driving 112 W LEDs in total was built and tested to verify the theoretical analysis.

  8. White light coronagraph in OSO-7

    International Nuclear Information System (INIS)

    Koomen, M.J.; Detwiler, C.R.; Brueckner, G.E.; Cooper, H.W.; Tousey, R.

    1975-01-01

    A small, externally occulted Lyot-type coronagraph, designated for use in the seventh unmanned Orbiting Solar Observatory (OSO-7), is described. Optical configuration, suppression of stray light, SEC vidicon detector, and data system are discussed, as well as integration of the instrument into the spacecraft and operation in orbit. Orbital operation produced daily images of the white light corona, from 2.8 to 10 solar radii, at least once per day for 2 3/4 yr. The first records of white light coronal transient events were obtained, and the corona was shown to be constantly changing

  9. GATEWAY Demonstrations: Tuning the Light in Senior Care: Evaluating a Trial LED Lighting System at the ACC Care Center in Sacramento, CA

    Energy Technology Data Exchange (ETDEWEB)

    Davis, Robert G. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Wilkerson, Andrea M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Samla, Connie [Sacramento Municipal Utility District, Sacramento, CA (United States); Bisbee, Dave [Sacramento Municipal Utility District, Sacramento, CA (United States)

    2016-08-31

    The GATEWAY program documented the performance of tunable-white LED lighting systems installed in several spaces within the ACC Care Center, a senior-care facility in Sacramento, CA. The project results included energy savings and improved lighting quality, as well as other possible health-related benefits that may have been attributable, at least in part, to the lighting changes.

  10. Universal fixture design for body mounted LED lights

    Science.gov (United States)

    Hajra, Debdyut

    2017-09-01

    Today LED headlamps, armbands and ankle-bands, shoe-lights etc. have become very popular. These find extensive use in search and rescue operations, mining, carving, etc. and are also used by individuals during hiking, trekking, running, etc. during dark hours. They serve two main purposes: they provide sufficient illumination in low light conditions and they are used to indicate the presence of a person after dark. These have the same basic requirements. They must produce sufficient light, have high durability, long battery life, must be light weight and energy efficient. This paper discusses possibilities of designing a universal LED fixture can be designed so that it meets the respective needs of everyone irrespective of their background and industry. It discusses the materials to be used for its different body parts, innovative clip design for attachment with support structures like head and armbands, helmets, shoes, etc.

  11. Fluorescent SiC as a new material for white LEDs

    International Nuclear Information System (INIS)

    Syväjärvi, M; Sun, JW; Jokubavicius, V; Hens, P; Ariyawong, K; Hens, P; Liljedahl, R; Müller, J; Spiecker, E; Grivickas, V; Gulbinas, K; Ou, Y; Ou, H; Kaisr, M; Wellmann, P; Linnarsson, M K; Kamiyama, S

    2012-01-01

    Current III-V-based white light-emitting diodes (LEDs) are available. However, their yellow phosphor converter is not efficient at high currents and includes rare-earth metals, which are becoming scarce. In this paper, we present the growth of a fluorescent silicon carbide material that is obtained by nitrogen and boron doping and that acts as a converter using a semiconductor. The luminescence is obtained at room temperature, and shows a broad luminescence band characteristic of donor-to-acceptor pair recombination. Photoluminescence intensities and carrier lifetimes reflect a sensitivity to nitrogen and boron concentrations. For an LED device, the growth needs to apply low-off-axis substrates. We show by ultra-high-resolution analytical transmission electron microscopy using aberration-corrected electrons that the growth mechanism can be stable and that there is a perfect epitaxial relation from the low-off-axis substrate and the doped layer even when there is step-bunching.

  12. Internal quantum efficiency and tunable colour temperature in monolithic white InGaN/GaN LED

    Science.gov (United States)

    Titkov, Ilya E.; Yadav, Amit; Zerova, Vera L.; Zulonas, Modestas; Tsatsulnikov, Andrey F.; Lundin, Wsevolod V.; Sakharov, Alexey V.; Rafailov, Edik U.

    2014-03-01

    Internal Quantum Efficiency (IQE) of two-colour monolithic white light emitting diode (LED) was measured by temperature dependant electro-luminescence (TDEL) and analysed with modified rate equation based on ABC model. External, internal and injection efficiencies of blue and green quantum wells were analysed separately. Monolithic white LED contained one green InGaN QW and two blue QWs being separated by GaN barrier. This paper reports also the tunable behaviour of correlated colour temperature (CCT) in pulsed operation mode and effect of self-heating on device performance.

  13. Health risks occurring when color is percepted under led lighting

    Directory of Open Access Journals (Sweden)

    V.A. Kaptsov

    2017-06-01

    Full Text Available The article deals with problems of color perception under LED lighting. We revealed that inadequate perception of a signal color by a driver led to greater risks of transport accidents. We reviewed both Jung-Helmholtz three-color hypothesis and a modern one based on fiber-optical approach to functioning of "Mueller cells and cones" system. We made an attempt to explain a number of effects related to visibility curves and time delays when defining color of light signals. Our research on assessing influence exerted by LED lighting on functional state and working capacity of railway workers during which we applied occupational selection techniques revealed negative changes. We proved there was a decrease in functional resistance to color sense between red and green signals as well as longer response time for complicated sight-motor reaction and significant decrease in readiness to emergency actions (resistance to monotony in examined individuals. The article also contains data on time peculiarities which are characteristic for defining signals color in relation to red signal (650 nm. We showed that when red color LEDs with wave length much shorter than 650 nm were used in signaling devices it caused risks of inadequate color detection, longer reaction to inhibiting signals, and greater possibility of transport accidents and negative events in everyday life. These peculiarities should be taken into account when designing traffic lights and other signaling devices which provide transport safety. We also proved that signaling traffic lights for transport systems should be designed allowing for physiology of color perception by a human visual analyzer; application of LEDs with wave length shorter than 650 nm should be absolutely excluded

  14. LED-based high-speed visible light communications

    Science.gov (United States)

    Chi, Nan; Shi, Meng; Zhao, Yiheng; Wang, Fumin; Shi, Jianyang; Zhou, Yingjun; Lu, Xingyu; Qiao, Liang

    2018-01-01

    We are seeing a growing use of light emitting diodes (LEDs) in a range of applications including lighting, TV and backlight board screen, display etc. In comparison with the traditional incandescent and fluorescent light bulbs, LEDs offer long life-space, much higher energy efficiency, high performance cost ratio and above all very fast switching capability. LED based Visible Light Communications (VLC) is an emerging field of optical communications that focuses on the part of the electromagnetic spectrum that humans can see. Depending on the transmission distance, we can divide the whole optical network into two categories, long haul and short haul. Visible light communication can be a promising candidate for short haul applications. In this paper, we outline the configuration of VLC, its unique benefits, and describe the state of the art research contributions consisting of advanced modulation formats including adaptive bit loading OFDM, carrierless amplitude and phase (CAP), pulse amplitude modulation (PAM) and single carrier Nyquist, linear equalization and nonlinear distortion mitigation based on machine learning, quasi-balanced coding and phase-shifted Manchester coding. These enabling technologies can support VLC up to 10Gb/s class free space transmission.

  15. Measurements of UGR of LED light by a DSLR colorimeter

    Science.gov (United States)

    Hsu, Shau-Wei; Chen, Cheng-Hsien; Jiaan, Yuh-Der

    2012-10-01

    We have developed an image-based measurement method on UGR (unified glare rating) of interior lighting environment. A calibrated DSLR (digital single-lens reflex camera) with an ultra wide-angle lens was used to measure the luminance distribution, by which the corresponding parameters can be automatically calculated. A LED lighting was placed in a room and measured at various positions and directions to study the properties of UGR. The testing results are fitted with visual experiences and UGR principles. To further examine the results, a spectroradiometer and an illuminance meter were respectively used to measure the luminance and illuminance at the same position and orientation of the DSLR. The calculation of UGR by this image-based method may solve the problem of non-uniform luminance-distribution of LED lighting, and was studied on segmentation of the luminance graph for the calculations.

  16. Tuning the white light spectrum of light emitting diode lamps to reduce attraction of nocturnal arthropods.

    Science.gov (United States)

    Longcore, Travis; Aldern, Hannah L; Eggers, John F; Flores, Steve; Franco, Lesly; Hirshfield-Yamanishi, Eric; Petrinec, Laina N; Yan, Wilson A; Barroso, André M

    2015-05-05

    Artificial lighting allows humans to be active at night, but has many unintended consequences, including interference with ecological processes, disruption of circadian rhythms and increased exposure to insect vectors of diseases. Although ultraviolet and blue light are usually most attractive to arthropods, degree of attraction varies among orders. With a focus on future indoor lighting applications, we manipulated the spectrum of white lamps to investigate the influence of spectral composition on number of arthropods attracted. We compared numbers of arthropods captured at three customizable light-emitting diode (LED) lamps (3510, 2704 and 2728 K), two commercial LED lamps (2700 K), two commercial compact fluorescent lamps (CFLs; 2700 K) and a control. We configured the three custom LEDs to minimize invertebrate attraction based on published attraction curves for honeybees and moths. Lamps were placed with pan traps at an urban and two rural study sites in Los Angeles, California. For all invertebrate orders combined, our custom LED configurations were less attractive than the commercial LED lamps or CFLs of similar colour temperatures. Thus, adjusting spectral composition of white light to minimize attracting nocturnal arthropods is feasible; not all lights with the same colour temperature are equally attractive to arthropods. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  17. Design Secondary Optical System Applied in White-LED General Illumination

    International Nuclear Information System (INIS)

    Chen Chen; Zhang Xianhui

    2011-01-01

    As a new generation of light source, LED has many advantages that other light sources do not have. However, due to the nonuniform lighting of LED, secondary LED optical system design is particularly important. Freeform surface tailoring method, an important method of lighting design, establishes a light intensity change model after smooth surface refraction (reflection) of the light and simplifies the solution process for more complex issues of solution using the free surface tailoring method. Based on this method, secondary LED optical system is designed, and the light intensity distribution is simulated after LED light passes through the secondary optical system. The results show that the method has not only simplified the calculation process of the free surface tailoring method, but also the designed LED secondary optical system has achieved the purpose of uniform lighting to a certain degree.

  18. Annealing effect on the electrical and optical properties of Au/n-ZnO NWs Schottky diodes white LEDs

    Science.gov (United States)

    Soomro, M. Y.; Hussain, I.; Bano, N.; Nur, O.; Willander, M.

    2013-10-01

    We report the post-growth heat treatment effect on the electrical and the optical properties of hydrothermally grown zinc oxide (ZnO) nanowires (NWs) Schottky white light emitting diodes (LEDs). It was found that there is a changed in the electroluminescence (EL) spectrum when post growth annealing process was performed at 600 °C under nitrogen, oxygen and argon ambients. The EL spectrum for LEDs based on the as grown NWs show three bands red, green and blue centered at 724, 518 and 450 nm respectively. All devices based on ZnO NWs annealed in oxygen (O2), nitrogen (N2) and argon (Ar) ambient show blue shift in the violet and the red emissions whereas a red shift is observed in the green emission compared to the as grown NWs based device. The color rendering index (CRI) and the correlated color temperature (CCT) of all LEDs were calculated to be in the range 78-91 and 2753-5122 K, respectively. These results indicate that light from the LEDs can be tuned from cold white light to warm white light by post growth annealing.

  19. High-Voltage LED Light Engine with Integrated Driver

    Energy Technology Data Exchange (ETDEWEB)

    Soer, Wouter [Lumileds LLC, San Jose, CA (United States)

    2016-02-29

    LED luminaires have seen dramatic changes in cost breakdown over the past few years. The LED component cost, which until recently was the dominant portion of luminaire cost, has fallen to a level of the same order as the other luminaire components, such as the driver, housing, optics etc. With the current state of the technology, further luminaire performance improvement and cost reduction is realized most effectively by optimization of the whole system, rather than a single component. This project focuses on improving the integration between LEDs and drivers. Lumileds has developed a light engine platform based on low-cost high-power LEDs and driver topologies optimized for integration with these LEDs on a single substrate. The integration of driver and LEDs enables an estimated luminaire cost reduction of about 25% for targeted applications, mostly due to significant reductions in driver and housing cost. The high-power LEDs are based on Lumileds’ patterned sapphire substrate flip-chip (PSS-FC) technology, affording reduced die fabrication and packaging cost compared to existing technology. Two general versions of PSS-FC die were developed in order to create the desired voltage and flux increments for driver integration: (i) small single-junction die (0.5 mm2), optimal for distributed lighting applications, and (ii) larger multi-junction die (2 mm2 and 4 mm2) for high-power directional applications. Two driver topologies were developed: a tapped linear driver topology and a single-stage switch-mode topology, taking advantage of the flexible voltage configurations of the new PSS-FC die and the simplification opportunities enabled by integration of LEDs and driver on the same board. A prototype light engine was developed for an outdoor “core module” application based on the multi-junction PSS-FC die and the single-stage switch-mode driver. The light engine meets the project efficacy target of 128 lm/W at a luminous flux

  20. Novel Coatings for Enhancement of Light-Emitting Diodes (LEDs)

    Science.gov (United States)

    2006-10-28

    quantum efficiency of LEDs. SAIC’s strength is this area is a proprietary nonimaging optics code. In consultation with Lumileds, SAIC developed designs for...five different optical ele- ments that collect and project light from a LED. The simulations showed that the designs achieve a significant improvement... optical microscope at 100x power the coating is not visible. Fire sample 6DecO4P1 in tube furnace As a first test, sample 6Dec04P1 was progressively

  1. Control and Driving Methods for LED Based Intelligent Light Sources

    DEFF Research Database (Denmark)

    Beczkowski, Szymon

    of the diode is controlled either by varying the magnitude of the current or by driving the LED with a pulsed current and regulate the width of the pulse. It has been shown previously, that these two methods yield different effects on diode's efficacy and colour point. A hybrid dimming strategy has been...... proposed where two variable quantities control the intensity of the diode. This increases the controllability of the diode giving new optimisation possibilities. It has been shown that it is possible to compensate for temperature drift of white diode's colour point using hybrid dimming strategy. Also...

  2. High colour purity single-phased full colour emitting white LED phosphor Sr2V2O7:Eu3+

    International Nuclear Information System (INIS)

    Zhou Zhi; Zhou Nan; He Zhangxing; Liu Suqin; Liu Younian; Tian Ziwei; Wang Nanfang; Mao Zhiyong; Hintzen, H T

    2013-01-01

    Single-phased white-light-emitting phosphor Sr 2 V 2 O 7 :Eu 3+ was successfully synthesized by the solid-state method. The result of x-ray diffraction analysis indicated that the obtained phosphor has the same crystal structure as that of Sr 2 V 2 O 7 . The synthesized Sr 2 V 2 O 7 :Eu 3+ was combined with near-UV light (365 nm) chips and then assembled into ligtht-emitting diodes (LED) devices, which generated white light with colour coordinates of (0.324, 0.317). The white light was generated from yellow-green and red emissions, which should be attributed to the host Sr 2 V 2 O 7 and dopant Eu ions, respectively. The effects of the concentration of Eu ions and charge compensation on the emission intensity were carefully investigated. The results show that the energy migrates from the host to the dopant and also that Li 2 CO 3 should be the best charge compensator for this single-phased phosphor. In addition, the colour rendering index and luminescence efficiency of the fabricated LED devices with Sr 1.90 V 2 O 7 :0.10Eu 3+ phosphor were 91 and 32 lm W -1 , respectively, suggesting that Sr 1.90 V 2 O 7 :0.10Eu 3+ phosphor is a potential candidate for the phosphor-converted white-light-emitting diodes with near-UV chips.

  3. Fluorescent silicon carbide materials for white LEDs and photovoltaics

    DEFF Research Database (Denmark)

    Syväjärvi, Mikael; Ou, Haiyan; Wellmann, Peter

    the luminescence appears in the infrared region in a broad range from 700 to 1100 nm. This potentially can be used to develop an infrared LED for de-icing in wind power and airplanes, or medical applications. Further on, a very efficient solar cell material can be investigated by studying the impurity effect...

  4. White Light Generation in Human Saliva

    Science.gov (United States)

    Santhosh, C.; Dharmadhikari, A. K.; Dharmadhikari, J. A.; Alti, K.; Mathur, D.

    2011-07-01

    Interaction of intense, femto-second pulses of infrared light (800 nm) with water generates white light supercontinuum due to nonlinear optical effects. This supercontinuum was found to be suppressed by the addition of alpha amylase, a major protein in the human saliva. We have studied the suppression of supper continuum by human saliva, collected from healthy subjects with and without smoking habits. Suppression of the blue-sided components was observed significantly in non-smokers saliva than chain smokers.

  5. Polymer OLED White Light Development Program

    Energy Technology Data Exchange (ETDEWEB)

    Homer Antoniadis; Vi-En Choong; Stelios Choulis; Brian Cumpston; Rahul Gupta; Mathew Mathai; Michael Moyer; Franky So

    2005-12-19

    OSRAM Opto Semiconductors (OSRAM) successfully completed development, fabrication and characterization of the large area, polymer based white light OLED prototype at their OLED Research and Development (R&D) facility in San Jose, CA. The program, funded by the Department of Energy (DOE), consisted of three key objectives: (1) Develop new polymer materials and device architectures--in order to improve the performance of organic light emitters. (2) Develop processing techniques--in order to demonstrate and enable the manufacturing of large area, white light and color tunable, solid state light sources. (3) Develop new electronics and driving schemes for organic light sources, including color-tunable light sources. The key performance goals are listed. A world record efficiency of 25 lm/W was established for the solution processed white organic device from the significant improvements made during the project. However, the challenges to transfer this technology from an R&D level to a large tile format such as, the robustness of the device and the coating uniformity of large area panels, remain. In this regard, the purity and the blend nature of the materials are two factors that need to be addressed in future work. During the first year, OSRAM's Materials and Device group (M&D) worked closely with the major polymer material suppliers to develop the polymer emissive technology. M&D was successful in demonstrating a 7-8 lm/W white light source which was based on fluorescent materials. However, it became apparent that the major gains in efficiency could only be made if phosphorescent materials were utilized. Thus, in order to improve the performance of the resulting devices, the focus of the project shifted towards development of solution-processable phosphorescent light emitting diodes (PHOLEDs) and device architectures. The result is a higher efficiency than the outlined project milestone.

  6. Fluorescence image excited by a scanning UV-LED light

    Science.gov (United States)

    Tsai, Hsin-Yi; Chen, Yi-Ju; Huang, Kuo-Cheng

    2013-03-01

    An optical scanning system using UV-LED light to induced fluorescence technology can enhance a fluorescence image significantly in a short period. It has several advantages such as lower power consumption, no scattering effect in skins, and multilayer images can be obtained to analyze skin disease. From the experiment results, the light intensity increases with increase spot size and decrease scanning speed, but the image resolution is oppositely. Moreover, the system could be widely used in clinical diagnosis and photodynamic therapy for skin disease because even the irradiated time of fluorescence substance is short but it will provide accurately positioning of fluorescence object.

  7. The cinema LED lighting system design based on SCM

    Science.gov (United States)

    En, De; Wang, Xiaobin

    2010-11-01

    A LED lighting system in the modern theater and the corresponding control program is introduced. Studies show that moderate and mutative brightness in the space would attract audiences' attention on the screen easily. SCM controls LED dynamically by outputting PWM pulse in different duty cycle. That cinema dome lights' intensity can vary with the plot changed, make people get a better view of experience. This article expounds the architecture of hardware system in the schedule and the control flow of the host of the solution. Besides, it introduces the design of software as well. At last, the system which is proved energy-saving, reliable, good visual effect and having using value by means of producing a small-scale model, which reproduce the whole system and achieves the desired result.

  8. Design for The Indoor Visible Light Communication Application System Based on LED Visible Light

    Directory of Open Access Journals (Sweden)

    Lian Wenyu

    2017-01-01

    Full Text Available This paper designs an indoor visible light communication application system based on LED. The system can modulate the original signal one or more times, move to a specific frequency band, transmit on the power line, in the LED terminal use this module to decode, restore the Ethernet signals. This design is applicable to the simplicity of the LED visible light communication applications, which provide the premise and guarantee for the construction of smart home network.

  9. White light signal simulator microcontroller design | Haghighi ...

    African Journals Online (AJOL)

    In this research, first through experimental studies, the recorded signals associated with the light white from human retina cells were digitized, then the digital data were calculated and the resulted mathematical equation was programmed on a microcontroller, and by designing a circuit, the output voltage over time similar to ...

  10. Garden's lighting by led-luminaries supplied by photovoltaic

    International Nuclear Information System (INIS)

    Vasilev, H.; Angelov, A.; Ganchev, G.

    2006-01-01

    The implementation of the project by investment entirely of Denima 2001 Ltd. for garden illumination of the part of the public garden 'Studentski' is consider. The illumination installation is implemented by PV batteries and by luminaries made up by fluorescent laps and LED. The goals of this pilot project are to make a comparative analyses and observation for the operation of the light system for future development

  11. Effect of LED light quality on in vitro shoot proliferation and growth of ...

    African Journals Online (AJOL)

    As an alternative to conventional lighting systems, light emitting diode (LED) has been ... The objective of this study was to determine the effects of different LED light quality on ... Key words: Light quality, micropropagation, orchid, chlorophyll.

  12. Energy savings by implementation of light quality LED lighting. Final report; Implementering af energibesparelser ved benyttelse af hoejkvalitets LED belysning. Slutrapport

    Energy Technology Data Exchange (ETDEWEB)

    Dam-Hansen, C.; Thorseth, A.; Poulsen, Peter

    2010-03-15

    The project developed two new LED light sources and systems, emphasising the potential of LED technology for energy savings and lighting quality. A LED light source for display case lighting, replacing incandescent lamps, was successfully installed in the Treasury at Rosenborg Castle in Copenhagen, Denmark, and it was decided to extend the solution in 2010. Electricity savings of 74% were achieved. LED light sources replacing halogen bulbs in cooker hoods reduce electricity consumption by 69% and ensure even lighting of the entire working surface with about 500 lux at all cooking areas. Furthermore, a new LED optics system was patented. (ln)

  13. LED lighting for greenhouses. Final report; LED belysning til vaeksthuse. Slutrapport

    Energy Technology Data Exchange (ETDEWEB)

    OEstergaard, J.E. (Syddansk Univ. (SDU). Erhvervsinnovation og Teknologi, Odense (Denmark))

    2011-01-15

    The project had 3 main objectives: 1) To develop a prototype of a LED-based luminaire that can replace the existing glasshouse horticultural lighting. The project have developed a working prototype and experimentally replaced the traditional HPS luminaires in a controlled growing area. The project succeeded in producing plants of comparable quality. However, the project shows that the prototype can be improved by: x) being further integrated into the existing horticultural production technology (eg climate computers and purchase of electricity) x) adapting configuration of luminaires specifically to each plant variety x) adapting different cooling technologies to match specific customer needs x) In some cases being combined with heat input to optimize the overall economy. 2) To achieve an effective electricity savings of 50-80% - equivalent to a value of approx. DKK 5 million for a medium sized nursery. The verified electricity savings was 40%. In test setups and in well defined and controllable production areas the prototypes achieved electricity savings of > 50%. It is expected that a new generation of LEDs (Q3 2010) will allow for greater power savings. 3) To continue prototype development and initiate commercialization of the project through the company Fionia Lighting A/S. The shareholders of the company have allocated capital to the company to allow us to address the main challenges in commercializing the technology. It is expected that the company will enter a strategic alliance with a major industrial player in the beginning of 2011. (Author)

  14. White light quality of phosphor converted light-emitting diodes: A phosphor materials perspective of view

    International Nuclear Information System (INIS)

    Sommer, Christian; Hartmann, Paul; Pachler, Peter; Hoschopf, Hans; Wenzl, Franz P.

    2012-01-01

    Highlights: ► We discuss the impact of the optical properties of a phosphor for colour temperature constancy in solid state lighting. ► Quantitative evaluation of permissible variations of the optical properties for batch-to-batch reproducibility. ► Quantitative evaluation of permissible variations of the optical properties upon temperature increase. ► Quantitative evaluation of permissible variations of the optical properties upon materials degradation. - Abstract: For a systematic approach to improve the white light quality of phosphor converted LEDs and to fulfil the demands for colour temperature reproducibility and constancy, it is imperative to understand how variations of the extinction coefficient and the quantum efficiency of the phosphor particles as well as variations of the excitation wavelength of the blue LED die affect the correlated colour temperature of the white LED source. Based on optical ray tracing of a phosphor converted white LED package we deduce permissible values for the variation of a given extinction coefficient and a given quantum efficiency of a phosphor material in order to maintain acceptable colour variations. These quantitative valuations of the required constancy of the optical properties of the phosphors will in particular provide some benchmarks for the synthesis of improved phosphor materials aiming at solid state lighting applications.

  15. New Framework of Sustainable Indicators for Outdoor LED (Light Emitting Diodes Lighting and SSL (Solid State Lighting

    Directory of Open Access Journals (Sweden)

    Annika K. Jägerbrand

    2015-01-01

    Full Text Available Light emitting diodes (LEDs and SSL (solid state lighting are relatively new light sources, but are already widely applied for outdoor lighting. Despite this, there is little available information allowing planners and designers to evaluate and weigh different sustainability aspects of LED/SSL lighting when making decisions. Based on a literature review, this paper proposes a framework of sustainability indicators and/or measures that can be used for a general evaluation or to highlight certain objectives or aspects of special interest when choosing LED/SSL lighting. LED/SSL lighting is reviewed from a conventional sustainable development perspective, i.e., covering the three dimensions, including ecological, economic and social sustainability. The new framework of sustainable indicators allow prioritization when choosing LED/SSL products and can thereby help ensure that short-term decisions on LED/SSL lighting systems are in line with long-term sustainability goals established in society. The new framework can also be a beneficial tool for planners, decision-makers, developers and lighting designers, or for consumers wishing to use LED/SSL lighting in a sustainable manner. Moreover, since some aspects of LED/SSL lighting have not yet been thoroughly studied or developed, some possible future indicators are suggested.

  16. Colour tuning in white hybrid inorganic/organic light-emitting diodes

    International Nuclear Information System (INIS)

    Bruckbauer, Jochen; Brasser, Catherine; Edwards, Paul R; Martin, Robert W; Findlay, Neil J; Skabara, Peter J; Wallis, David J

    2016-01-01

    White hybrid inorganic/organic light-emitting diodes (LEDs) were fabricated by combining a novel organic colour converter with a blue inorganic LED. An organic small molecule was specifically synthesised to act as down-converter. The characteristics of the white colour were controlled by changing the concentration of the organic molecule based on the BODIPY unit, which was embedded in a transparent matrix, and volume of the molecule and encapsulant mixture. The concentration has a critical effect on the conversion efficiency, i.e. how much of the absorbed blue light is converted into yellow light. With increasing concentration the conversion efficiency decreases. This quenching effect is due to aggregation of the organic molecule at higher concentrations. Increasing the deposited amount of the converter does not increase the yellow emission despite more blue light being absorbed. Degradation of the organic converter was also observed during a period of 15 months from LED fabrication. Angular-dependent measurements revealed slight deviation from a Lambertian profile for the blue and yellow emission peaks leading to a small change in ‘whiteness’ with emission angle. Warm white and cool white light with correlated colour temperatures of 2770 K and 7680 K, respectively, were achieved using different concentrations of the converter molecule. Although further work is needed to improve the lifetime and poor colour rendering, these hybrid LEDs show promising results as an alternative approach for generating white LEDs compared with phosphor-based white LEDs. (paper)

  17. Tunable white light source for medical applications

    Science.gov (United States)

    Blaszczak, Urszula J.; Gryko, Lukasz; Zajac, Andrzej

    2017-08-01

    Development of light-emitting diodes has brought new possibilities in many applications, especially in terms of flexible adjustment of light spectra. This feature is very useful in construction of many devices, for example for medical diagnosis and treatment. It was proved, that in some cases LEDs can easily replace lasers during therapy of cancer without reduction of efficiency of this process. On the other hand during diagnosis process LED-based constructions can provide unique ability to adjust the color temperature of the output light while maintaining high color rendering. It allows for optimum surface contrast and enhanced tissue differentiation at the operator site. In the paper we describe the construction of the tunable LED-based source designed for application in endoscopy. It was optimized from the point of view of the color rendition for 5 different correlated color temperatures (illuminant A, D55, D65, 3500K and 4500K) with the restriction of very high (>90) values of general and specific color rendering indexes (according to Ra method). The source is composed of 13 light-emitting diodes from visible region mounted on the common radiator and controlled by dedicated system. Spectra of the components are mixed and the spectra of output light is analyzed. On the basis of obtained spectra colorimetric parameters are calculated and compared with the results of theoretical analysis.

  18. White light emission from engineered silicon carbide

    DEFF Research Database (Denmark)

    Ou, Haiyan

    Silicon carbide (SiC) is a wide indirect bandgap semiconductor. The light emission efficiency is low in nature. But this material has very unique physical properties like good thermal conductivity, high break down field etc in addition to its abundance. Therefore it is interesting to engineer its...... light emission property so that to take fully potential applications of this material. In this talk, two methods, i.e. doping SiC heavily by donor-acceptor pairs and making SiC porous are introduced to make light emission from SiC. By co-doping SiC with nitrogen and boron heavily, strong yellow emission...... is demonstrated. After optimizing the passivation conditions, strong blue-green emission from porous SiC is demonstrated as well. When combining the yellow emission from co-doped SiC and blue-green from porous SiC, a high color rendering index white light source is achieved....

  19. Innovations in LED lighting for reduced-ESM crop production in space

    Science.gov (United States)

    Massa, Gioia; Mitchell, Cary; Bourget, C. Michael; Morrow, Robert

    In controlled-environment crop production such as will be practiced at the lunar outpost and Mars base, the single most energy-demanding aspect is electric lighting for plant growth, including energy costs for energizing lamps as well as for removing excess heat. For a variety of reasons, sunlight may not be a viable option as the main source of crop lighting off-Earth and traditional electric lamps for crop lighting have numerous drawbacks for use in a space environment. A collaborative research venture between the Advanced Life Support Crops Group at Purdue University and the Orbital Technologies Corporation (ORBITEC) has led to the development of efficient, reconfigurable LED lighting technologies for crop growth in an ALSS. The light sources use printed-circuit red and blue LEDs, which are individually tunable for a range of photosynthetic photon fluxes and photomorphogenic plant responses. Initial lighting arrays have LEDs that can be energized from the bottom upward when deployed in a vertical, intracanopy configuration, allowing the illumination to be tailored for stand height throughout the cropping cycle. Preliminary testing with the planophile crop cowpea (Vigna unguiculata L. Walp, breeding line IT87D-941-1), resulted in optimizing internal reflectance of growth compartments by lining walls, floor, and a movable ceiling with white Poly film, as well as by determining optimal planting density and plant positioning. Additionally, these light strips, called "lightsicles", can be configured into an overhead plane of light engines. When intracanopy and overhead-LED-lit cowpea crop production was compared, cowpea plants grown with intracanopy lighting had much greater understory leaf retention and produced more dry biomass per kilowatt-hour of lighting energy than did overhead-lit plants. The efficiency of light capture is reduced in overhead-lit scenarios due to mutual shading of lower leaves by upper leaves in closed canopies leading to premature abscission

  20. Laser Based Phosphor Converted Solid State White Light Emitters

    Science.gov (United States)

    Cantore, Michael

    Artificial lighting and as a consequence the ability to be productive when the sun does not shine may be a profound achievement in society that is largely taken for granted. As concerns arise due to our dependence on energy sources with finite lifespan or environmentally negative effects, efforts to reduce energy consumption and create clean renewable alternatives has become highly valued. In the scope of artificial lighting, the use of incandescent lamps has shifted to more efficient light sources. Fluorescent lighting made the first big gains in efficiency over incandescent lamps with peak efficiency for mature designs reaching luminous efficacy of approximately 90 lm/W; more than three times as efficient as an incandescent lamp. Lamps based on light emitting diodes (LEDs) which can produce light at even greater efficiency, color quality and without the potential for hazardous chemical release from lamp failure. There is a significant challenge with LED based light sources. Their peak efficiency occurs at low current densities and then droops as the current density increases. Laser diodes (LDs) do not suffer from decreasing efficiency due to increased current. An alternative solid state light source using LDs has potential to make further gains in efficiency as well as allow novel illuminant designs which may be impractical or even impossible even with LED or other conventional sources. While similar to LEDS, the use of LDs does present new challenges largely due to the increased optical power density which must be accommodated in optics and phosphor materials. Single crystal YAG:Ce has been shown to be capable of enduring this more extreme operating environment while retaining the optical and fluorescing qualities desired for use as a wavelength converter in phosphor converted LD based white emitting systems. The incorporation of this single crystal phosphor in a system with a commercial laser diode with peak wall plug efficiency of 31% resulted in emission of

  1. Stolephorus sp Behavior in Different LED (Light Emitting Diode) Color and Light Intensities

    Science.gov (United States)

    Fitri Aristi, D. P.; Ramadanita, I. A.; Hapsari, T. D.; Susanto, A.

    2018-02-01

    This research aims to observe anchovy (Stolephorus sp) behavior under different LED light intensities that affect eye physiology (cell cone structure). The materials used were Stolephorus sp taken from the waters off Jepara and 13 and 10 watt light emitting diode (LED). The research method was an experiment conducted from March through August 2015 in the waters off Jepara. Data analysis of visual histology and fish respond was carried out at the fishing gear material laboratory, anatomy and cultivate. Cone cell structure (mosaic cone) of Stolephorus sp forms a connected regular square pattern with every single cone surrounded by four double cones, which indicate that anchovies are sensitive to light. The 13 watt LED (628 lux) has faster response than the 10 watt LED (531 lux) as it has wider and higher emitting intensity, which also attracts fish to gather quicker.

  2. Patterns of Light Chasing the Spectrum from Aristotle to LEDs

    CERN Document Server

    Beeson, Steven

    2008-01-01

    Light is all around us – even when we do not see it. Our eyes do not detect the higher energy and shorter-than-visible-wavelength ultraviolet radiation, yet we know it is there from the sunburn we receive in Arizona. We know that window glass can block ultraviolet rays so we do not get a burn while driving with the windows rolled up. Our eyes do not detect the low-energy, long-wavelength infrared (IR) radiation but we know it exists from discussions of war applications and televised images of guided weapons targets. We also know about radio waves from the little boxes that talk to us and x-rays from the dentist's office. Patterns of Light, Chasing the Spectrum from Aristotle to LEDs, written by Steve Beeson and Jim Mayer starts with the visible – the straight path of light. It continues with chapters detailing reflection (mirrors, storefront windows) and refraction (eyeglasses, binoculars). Color is then introduced with the query "Why is the sky blue?" After answering that and other similar questions ("Wh...

  3. Environmentally Benign Technology for Efficient Warm-White Light Emission

    Science.gov (United States)

    Shen, Pin-Chun; Lin, Ming-Shiun; Lin, Ching-Fuh

    2014-06-01

    Nowadays efficient down conversion for white light emission is mainly based on rare-earth doped phosphors or cadmium-containing quantum dots. Although they exhibit high luminescence efficiency, the rare-earth mining and cadmium pollution have so far led to extremely high environmental cost, which conflicts the original purpose of pursuing efficient lighting. Here, we explore a new strategy to achieve efficient luminescence conversion based on polymer-decorated nanoparticles. The ZnO and Mn2+ doped ZnS nanoparticles are encapsulated by poly(9,9-di-n- hexylfluorenyl-2,7-diyl). The resultant core-shell nanocomposites then encompass three UV-to-visible luminescence conversion routes for photon emissions at blue, green, and orange colors, respectively. As a result, the color temperature is widely tunable (2100 K ~ 6000 K), so candle light or pure white light can be generated. The quantum yield up to 91% could also be achieved. Such rare-earth-element free nanocomposites give the bright perspectives for energy-saving, healthy, and environmentally benign lighting.

  4. Fluorescent Silicon Carbide and its Applications in White Light-Emitting Diodes

    DEFF Research Database (Denmark)

    Ou, Yiyu

    light extraction efficiency are presented. White LEDs are the most promising techniques to replace the conventional lighting sources. A typical white LED consists of a Gallium Nitride (GaN) blue or Ultraviolet (UV) LED stack and a wavelengthconversion material. Silicon Carbide (SiC) has a wide optical...... rendering performance and a much longer material lifetime compared with the commonly used wavelength-conversion material like Phosphors. In this thesis, f-SiC with different doping concentrations are analyzed and optimized in order to enhance the quantum efficiency. On the other hand, semiconductor...

  5. A transition to white LED increases ecological impacts of nocturnal illumination on aquatic primary producers in a lowland agricultural drainage ditch.

    Science.gov (United States)

    Grubisic, Maja; van Grunsven, Roy H A; Manfrin, Alessandro; Monaghan, Michael T; Hölker, Franz

    2018-05-14

    The increasing use of artificial light at night (ALAN) has led to exposure of freshwater ecosystems to light pollution worldwide. Simultaneously, the spectral composition of nocturnal illumination is changing, following the current shift in outdoor lighting technologies from traditional light sources to light emitting diodes (LED). LEDs emit broad-spectrum white light, with a significant amount of photosynthetically active radiation, and typically a high content of blue light that regulates circadian rhythms in many organisms. While effects of the shift to LED have been investigated in nocturnal animals, its impact on primary producers is unknown. We performed three field experiments in a lowland agricultural drainage ditch to assess the impacts of a transition from high-pressure sodium (HPS) to white LED illumination (color temperature 4000 K) on primary producers in periphyton. In all experiments, we compared biomass and pigment composition of periphyton grown under a natural light regime to that of periphyton exposed to nocturnal HPS or, consecutively, LED light of intensities commonly found in urban waters (approximately 20 lux). Periphyton was collected in time series (1-13 weeks). We found no effect of HPS light on periphyton biomass; however, following a shift to LED the biomass decreased up to 62%. Neither light source had a substantial effect on pigment composition. The contrasting effects of the two light sources on biomass may be explained by differences in their spectral composition, and in particular the blue content. Our results suggest that spectral composition of the light source plays a role in determining the impacts of ALAN on periphyton and that the ongoing transition to LED may increase the ecological impacts of artificial lighting on aquatic primary producers. Reduced biomass in the base of the food web can impact ecosystem functions such as productivity and food supply for higher trophic levels in nocturnally-lit ecosystems. Copyright

  6. Conversion of Biowaste Asian Hard Clam (Meretrix lusoria) Shells into White-Emitting Phosphors for Use in Neutral White LEDs.

    Science.gov (United States)

    Chang, Tsung-Yuan; Wang, Chih-Min; Lin, Tai-Yuan; Lin, Hsiu-Mei

    2016-12-02

    The increasing volume and complexity of waste associated with the modern economy poses a serious risk to ecosystems and human health. However, the remanufacturing and recycling of waste into usable products can lead to substantial resource savings. In the present study, clam shell waste was first transformed into pure and well-crystallized single-phase white light-emitting phosphor Ca₉Gd(PO₄)₇:Eu 2+ ,Mn 2+ materials. The phosphor Ca₉Gd(PO₄)₇:Eu 2+ ,Mn 2+ materials were synthesized by the solid-state reaction method and the carbothermic reduction process, and then characterized and analyzed by means of X-ray diffraction (XRD) and photoluminescence (PL) measurements. The structural and luminescent properties of the phosphors were investigated as well. The PL and quantum efficiency measurements showed that the luminescence properties of clam shell-based phosphors were comparable to that of the chemically derived phosphors. Moreover, white light-emitting diodes were fabricated through the integration of 380 nm chips and single-phase white light-emitting phosphors (Ca 0.979 Eu 0.006 Mn 0.015 )₉Gd(PO₄)₇ into a single package of a white light emitting diode (WLED) emitting a neutral white light of 5298 K with color coordinates of (0.337, 0.344).

  7. Conversion of Biowaste Asian Hard Clam (Meretrix lusoria Shells into White-Emitting Phosphors for Use in Neutral White LEDs

    Directory of Open Access Journals (Sweden)

    Tsung-Yuan Chang

    2016-12-01

    Full Text Available The increasing volume and complexity of waste associated with the modern economy poses a serious risk to ecosystems and human health. However, the remanufacturing and recycling of waste into usable products can lead to substantial resource savings. In the present study, clam shell waste was first transformed into pure and well-crystallized single-phase white light-emitting phosphor Ca9Gd(PO47:Eu2+,Mn2+ materials. The phosphor Ca9Gd(PO47:Eu2+,Mn2+ materials were synthesized by the solid-state reaction method and the carbothermic reduction process, and then characterized and analyzed by means of X-ray diffraction (XRD and photoluminescence (PL measurements. The structural and luminescent properties of the phosphors were investigated as well. The PL and quantum efficiency measurements showed that the luminescence properties of clam shell-based phosphors were comparable to that of the chemically derived phosphors. Moreover, white light-emitting diodes were fabricated through the integration of 380 nm chips and single-phase white light-emitting phosphors (Ca0.979Eu0.006Mn0.0159Gd(PO47 into a single package of a white light emitting diode (WLED emitting a neutral white light of 5298 K with color coordinates of (0.337, 0.344.

  8. Tuning the diurnal natural daylight with phosphor converted white LED – Advent of new phosphor blend composition

    International Nuclear Information System (INIS)

    Kim, Yoon Hwa; Arunkumar, Paulraj; Park, Seung Hyok; Yoon, Ho Shin; Im, Won Bin

    2015-01-01

    Highlights: • Designed phosphor blend that mimics diurnal daylight for health benefits. • Developed new phosphor blend composition that mimics natural sunlight under near UV. • The phosphor blend also exhibits high CRI (≥90) under blue LED excitation. • Fabricated WLED exhibited ∼91% spectral resemblance with daylight at 4500 K. • While ∼39.2% spectral resemblance were observed for YAG:Ce 3+ at 4500 K. - Abstract: We demonstrate the feasibility of developing phosphor converted white LED (pc-WLED) that mimics diurnal natural daylight with the newly designed phosphor blend in the color temperature (CCT) 2700–6000 K for health benefits. Natural daylight (sunlight) spectrum possesses broad emission in the visible region and closely approximates black body radiator, with color rendition index (CRI) of 100 under wide CCT (2500–6500 K). Current white light LEDs although are efficient and durable, they are not broad enough compared to daylight. We report new phosphor blend based on Sr 3 MgSi 2 O 8 :Eu 2+ blue phosphor with broad emission and high CRI ≥ 96 under both near UV and blue excitation. The fabricated WLED has exhibited ∼91% spectral resemblance with natural daylight compared to 39.2% for YAG:Ce 3+ white LED at 4500 K. The developed phosphor blend tunes the spectrum in wider CCT and would be a prospective candidate for full spectrum daylight WLED

  9. Tuning the diurnal natural daylight with phosphor converted white LED – Advent of new phosphor blend composition

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yoon Hwa [School of Materials Science and Engineering, Chonnam National University, 300, Yongbong-dong, Buk-gu, Gwangju 500-757 (Korea, Republic of); Research Institute, Force4 Corp., Daechon-dong, Buk-gu, Gwangju 500-470 (Korea, Republic of); Arunkumar, Paulraj [School of Materials Science and Engineering, Chonnam National University, 300, Yongbong-dong, Buk-gu, Gwangju 500-757 (Korea, Republic of); Park, Seung Hyok; Yoon, Ho Shin [Research Institute, Force4 Corp., Daechon-dong, Buk-gu, Gwangju 500-470 (Korea, Republic of); Im, Won Bin, E-mail: imwonbin@jnu.ac.kr [School of Materials Science and Engineering, Chonnam National University, 300, Yongbong-dong, Buk-gu, Gwangju 500-757 (Korea, Republic of)

    2015-03-15

    Highlights: • Designed phosphor blend that mimics diurnal daylight for health benefits. • Developed new phosphor blend composition that mimics natural sunlight under near UV. • The phosphor blend also exhibits high CRI (≥90) under blue LED excitation. • Fabricated WLED exhibited ∼91% spectral resemblance with daylight at 4500 K. • While ∼39.2% spectral resemblance were observed for YAG:Ce{sup 3+} at 4500 K. - Abstract: We demonstrate the feasibility of developing phosphor converted white LED (pc-WLED) that mimics diurnal natural daylight with the newly designed phosphor blend in the color temperature (CCT) 2700–6000 K for health benefits. Natural daylight (sunlight) spectrum possesses broad emission in the visible region and closely approximates black body radiator, with color rendition index (CRI) of 100 under wide CCT (2500–6500 K). Current white light LEDs although are efficient and durable, they are not broad enough compared to daylight. We report new phosphor blend based on Sr{sub 3}MgSi{sub 2}O{sub 8}:Eu{sup 2+} blue phosphor with broad emission and high CRI ≥ 96 under both near UV and blue excitation. The fabricated WLED has exhibited ∼91% spectral resemblance with natural daylight compared to 39.2% for YAG:Ce{sup 3+} white LED at 4500 K. The developed phosphor blend tunes the spectrum in wider CCT and would be a prospective candidate for full spectrum daylight WLED.

  10. Integrated Automotive High-Power LED-Lighting Systems in 3D-MID Technology

    NARCIS (Netherlands)

    Thomas, W.

    2014-01-01

    The growing energy consumption of lighting as well as rising luminous efficacies and -fluxes of high-power Light Emitting Diodes (LEDs) have contributed to the widespread use of LEDs in modern lighting systems. One of the most prominent users of the LED-technology is automotive (exterior) lighting.

  11. Monochromatic light-emitting diode (LED source in layers hens during the second production cycle

    Directory of Open Access Journals (Sweden)

    Rodrigo Borille

    2015-09-01

    Full Text Available ABSTRACTLight is an important environmental factor for birds, allowing not only their vision, but also influencing their physiological responses, such as behavioral and reproductive activity. The objective of this experiment was to evaluate the impact of different colors of monochromatic light (LED sources in laying hens production during the second laying cycle. The study was conducted in an experimental laying house during 70 days. A total of 300 laying hens Isa Brown® genetic strain, aged 95 weeks, in the second laying cycle were used in the study. The artificial light sources used were blue, yellow, green, red and white. The light regimen was continuous illumination of 17 h per day (12 h natural and 5 h artificial in a daily light regimen of 17L:5D (light: dark. The Latin Square design was adopted with five treatments (five colors divided into five periods, and five boxes, with six replicates of ten birds in each box. The production and egg quality were evaluated. The different colors of light source did not affect production parameters or egg quality (p > 0.05. The monochromatic light source may be considered as an alternative to artificial lighting in laying hens during the second production cycle.

  12. Visible light communication based vehicle positioning using LED street light and rolling shutter CMOS sensors

    Science.gov (United States)

    Do, Trong Hop; Yoo, Myungsik

    2018-01-01

    This paper proposes a vehicle positioning system using LED street lights and two rolling shutter CMOS sensor cameras. In this system, identification codes for the LED street lights are transmitted to camera-equipped vehicles through a visible light communication (VLC) channel. Given that the camera parameters are known, the positions of the vehicles are determined based on the geometric relationship between the coordinates of the LEDs in the images and their real world coordinates, which are obtained through the LED identification codes. The main contributions of the paper are twofold. First, the collinear arrangement of the LED street lights makes traditional camera-based positioning algorithms fail to determine the position of the vehicles. In this paper, an algorithm is proposed to fuse data received from the two cameras attached to the vehicles in order to solve the collinearity problem of the LEDs. Second, the rolling shutter mechanism of the CMOS sensors combined with the movement of the vehicles creates image artifacts that may severely degrade the positioning accuracy. This paper also proposes a method to compensate for the rolling shutter artifact, and a high positioning accuracy can be achieved even when the vehicle is moving at high speeds. The performance of the proposed positioning system corresponding to different system parameters is examined by conducting Matlab simulations. Small-scale experiments are also conducted to study the performance of the proposed algorithm in real applications.

  13. A phosphor-free white light-emitting diode using In2O3 : Tb transparent conductive light converter

    International Nuclear Information System (INIS)

    Chen, Lung-Chien; Tien, Ching-Ho; Liao, Wei-Chian

    2011-01-01

    Tb-doped indium oxide (In 2 O 3 : Tb) films were deposited on a GaN-based near-ultraviolet (NUV) light-emitting diode (LED) as a transparent conductive light converter to form a white LED. The transmittance of the In 2 O 3 : Tb film (Tb at 10 wt%) exceeded 80% in visible light and the resistivity was 0.325 Ω cm. The In 2 O 3 : Tb transparent conductive light converter was also employed on GaN-based LEDs. GaN-based NUV-LEDs with In 2 O 3 : Tb film (Tb at 10 wt%) produced forward biases of 3.42 V at an injection current of 20 mA. With increasing temperature, increasing Tb 3+ concentration and increasing injection current from 20 to 100 mA, the chromaticity coordinates barely changed in the white light area. Therefore, the GaN-based NUV-LED with In 2 O 3 : Tb film had a stable white light colour, when temperature and injection current changed, and is suitable for solid-state lighting.

  14. The health risks associated with energy efficient fluorescent, LEDs, and artificial lighting

    Science.gov (United States)

    Panahi, Allen

    2014-09-01

    With the phasing out of incandescent lamps in many countries, the introduction of new LED based light sources and luminaries sometimes raise the question of whether the spectral characteristics of the LED and other energy savings Fluorescent lights including the popular CFLs are suitable to replace the traditional incandescent lamps. These concerns are sometimes raised particularly for radiation emissions in the UV and Blue parts of the spectrum. This paper aims to address such concerns for the common `white light' sources typically used in household and other general lighting used in the work place. Recent studies have shown that women working the night shift have an increased probability of developing breast cancer. We like to report on the findings of many studies done by medical professionals, in particular the recent announcement of AMA in the US and many studies conducted in the UK, as well as the European community to increase public awareness on the long term health risks of the optical and opto-biological effects on the human health caused by artificial lighting.

  15. Color Shift Failure Prediction for Phosphor-Converted White LEDs by Modeling Features of Spectral Power Distribution with a Nonlinear Filter Approach.

    Science.gov (United States)

    Fan, Jiajie; Mohamed, Moumouni Guero; Qian, Cheng; Fan, Xuejun; Zhang, Guoqi; Pecht, Michael

    2017-07-18

    With the expanding application of light-emitting diodes (LEDs), the color quality of white LEDs has attracted much attention in several color-sensitive application fields, such as museum lighting, healthcare lighting and displays. Reliability concerns for white LEDs are changing from the luminous efficiency to color quality. However, most of the current available research on the reliability of LEDs is still focused on luminous flux depreciation rather than color shift failure. The spectral power distribution (SPD), defined as the radiant power distribution emitted by a light source at a range of visible wavelength, contains the most fundamental luminescence mechanisms of a light source. SPD is used as the quantitative inference of an LED's optical characteristics, including color coordinates that are widely used to represent the color shift process. Thus, to model the color shift failure of white LEDs during aging, this paper first extracts the features of an SPD, representing the characteristics of blue LED chips and phosphors, by multi-peak curve-fitting and modeling them with statistical functions. Then, because the shift processes of extracted features in aged LEDs are always nonlinear, a nonlinear state-space model is then developed to predict the color shift failure time within a self-adaptive particle filter framework. The results show that: (1) the failure mechanisms of LEDs can be identified by analyzing the extracted features of SPD with statistical curve-fitting and (2) the developed method can dynamically and accurately predict the color coordinates, correlated color temperatures (CCTs), and color rendering indexes (CRIs) of phosphor-converted (pc)-white LEDs, and also can estimate the residual color life.

  16. High efficient white organic light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Seidel, Stefan; Krause, Ralf [Department of Materials Science VI, University of Erlangen-Nuremberg (Germany); Siemens AG, CT MM 1, Erlangen (Germany); Kozlowski, Fryderyk; Schmid, Guenter; Hunze, Arvid [Siemens AG, CT MM 1, Erlangen (Germany); Winnacker, Albrecht [Department of Materials Science VI, University of Erlangen-Nuremberg (Germany)

    2007-07-01

    Due to the rapid progress in the last years the performance of organic light emitting diodes (OLEDs) has reached a level where general lighting presents a most interesting application target. We demonstrate, how the color coordinates of the emission spectrum can be adjusted using a combinatorial evaporation tool to lie on the desired black body curve representing cold and warm white, respectively. The evaluation includes phosphorescent and fluorescent dye approaches to optimize lifetime and efficiency, simultaneously. Detailed results are presented with respect to variation of layer thicknesses and dopant concentrations of each layer within the OLED stack. The most promising approach contains phosphorescent red and green dyes combined with a fluorescent blue one as blue phosphorescent dopants are not yet stable enough to achieve long lifetimes.

  17. Light source comprising a common substrate, a first led device and a second led device

    Science.gov (United States)

    Choong, Vi-En

    2010-02-23

    At least one stacked organic or polymeric light emitting diode (PLEDs) devices to comprise a light source is disclosed. At least one of the PLEDs includes a patterned cathode which has regions which transmit light. The patterned cathodes enable light emission from the PLEDs to combine together. The light source may be top or bottom emitting or both.

  18. Technical Feasibility Assessment of LED Roadway Lighting on the Golden Gate Bridge

    Energy Technology Data Exchange (ETDEWEB)

    Tuenge, Jason R.

    2012-09-01

    example, it would be preferable in terms of performance to simply replace existing luminaires (some of which may already be nearing end of life) with fully-integrated LED or CMH luminaires rather than replacing internal components. Among other benefits, this would allow reputable manufacturers to offer standard warranties for their products. Similarly, the amber lenses might be reformulated such that they do not render white light sources in a greenish cast, thereby allowing the use of off-the-shelf LED or CMH products. Last, it should be noted that the existing amber-lensed shoeboxes bear no daytime resemblance to the LPS luminaires originally used to light the roadway.

  19. GATEWAY Report Brief: Tuning the Light in Classrooms: Evaluating Trial LED Lighting Systems in Three Classrooms at the Carrollton-Farmers Branch Independent School District in Carrollton, TX

    Energy Technology Data Exchange (ETDEWEB)

    None

    2017-09-29

    Summary of GATEWAY report evaluating a trial installation of tunable-white LED lighting systems in three classrooms in the Carrollton-Farmers Branch Independent School District in Carrollton, TX. The report provides valuable insights into the use of this technology in a real-world setting.

  20. GATEWAY Report: Tuning the Light in Classrooms: Evaluating Trial LED Lighting Systems in Three Classrooms at the Carrollton-Farmers Branch Independent School District in Carrollton, TX

    Energy Technology Data Exchange (ETDEWEB)

    None, None

    2017-09-29

    The GATEWAY program evaluated a trial installation of tunable-white LED lighting systems in three classrooms in the Carrollton-Farmers Branch Independent School District in Carrollton, TX. The report provides valuable insights into the use of this technology in a real-world setting.

  1. The Design and Comparison of Central and Distributed Light Sensored Smart LED Lighting Systems

    Directory of Open Access Journals (Sweden)

    Mehmet Ali Özçelik

    2018-01-01

    Full Text Available There is a lack of published peer-reviewed research comparing the efficiencies of distributed versus central sensor-controlled LED lighting systems. This research proposes improving the smart illumination of a room with external fenestration using central and distributed light sensors. The optical and electrical measurements of the daylight have been made in the case where the light was not distributed evenly and not sufficient. Test results show that the proposed distributed light sensor illumination system has increased the efficiency by 28% when compared to the proposed central system. It has also been shown that the two tested systems are more cost-effective than common smart illumination systems.

  2. Spectrally resolved digital holography using a white light LED

    Science.gov (United States)

    Claus, D.; Pedrini, G.; Buchta, D.; Osten, W.

    2017-06-01

    This paper introduces the concept of spectrally resolved digital holography. The measurement principle and the analysis of the data will be discussed in detail. The usefulness of spectrally resolved digital holography is demonstrated for colour imaging and optical metrology with regards to the recovery of modulus information and phase information, respectively. The phase information will be used to measure the shape of an object via the application of the dual wavelength method. Based on the large degree of data available, multiple speckle de-correlated dual wavelength phase maps can be obtained, which when averaged result in a signal to noise ratio improvement.

  3. Effect of light dispersion of LED curing lights on resin composite polymerization.

    Science.gov (United States)

    Vandewalle, Kraig S; Roberts, Howard W; Andrus, Jeffrey L; Dunn, William J

    2005-01-01

    This study evaluated the effect of light dispersion of halogen and LED curing lights on resin composite polymerization. One halogen (Optilux 501, SDS/Kerr, Orange, CA, USA) and five light-emitting diode (LED) curing lights (SmartLite iQ, Dentsply Caulk, Milford, DE, USA; LEDemetron 1, SDS/Kerr; FLASHlite 1001, Discus Dental, Culver City, CA, USA; UltraLume LED 5, Ultradent Products, South Jordan, UT, USA; Allegro, Den-Mat, Santa Maria, CA, USA) were used in this study. Specimens (8 mm diameter by 2 mm thick) were made in polytetrafluoroethylene molds using hybrid (Z100, 3M ESPE, St. Paul, MN, USA) and microfill (A110, 3M ESPE) composite resins. The top surface was polymerized for 5 seconds with the curing light guide tip positioned at a distance of 1 and 5 mm. Degree of conversion (DC) of the composite specimens was analyzed on the bottom surface using micro-Fourier Transform Infrared (FTIR) spectroscopy (Perkin-Elmer FTIR Spectrometer, Wellesley, PA, USA) 10 minutes after light activation. DC at the bottom of the 2 mm specimen was expressed as a percentage of the mean maximum DC. Five specimens were created per curing light and composite type (n=5). Percent mean DC ratios and SDs were calculated for each light under each testing condition. Data were analyzed by analysis of variance (ANOVA)/Tukey's test (alpha = .05). A beam analyzer (LBA-700, Spiricon, Logan, UT, USA) was used to record the emitted light from the curing lights at 0 and 5 mm distances (n=5). A Top Hat factor was used to compare the quality of the emitted beam profile (LBA/PC, Spiricon). The divergence angle from vertical was also determined in the x- and y-axes (LBA/PC). Mean values and SDs were calculated for each light under each testing condition (0 and 5 mm, x- and y-axes) and analyzed by a two-way ANOVA/Tukey's test (alpha = .05). For DC ratios, significant differences were found based on curing light and curing distance (p < .05). At 1 mm, Optilux 501 and FLASHlite 1001 produced significantly

  4. Color Shift Failure Prediction for Phosphor-Converted White LEDs by Modeling Features of Spectral Power Distribution with a Nonlinear Filter Approach

    Directory of Open Access Journals (Sweden)

    Jiajie Fan

    2017-07-01

    Full Text Available With the expanding application of light-emitting diodes (LEDs, the color quality of white LEDs has attracted much attention in several color-sensitive application fields, such as museum lighting, healthcare lighting and displays. Reliability concerns for white LEDs are changing from the luminous efficiency to color quality. However, most of the current available research on the reliability of LEDs is still focused on luminous flux depreciation rather than color shift failure. The spectral power distribution (SPD, defined as the radiant power distribution emitted by a light source at a range of visible wavelength, contains the most fundamental luminescence mechanisms of a light source. SPD is used as the quantitative inference of an LED’s optical characteristics, including color coordinates that are widely used to represent the color shift process. Thus, to model the color shift failure of white LEDs during aging, this paper first extracts the features of an SPD, representing the characteristics of blue LED chips and phosphors, by multi-peak curve-fitting and modeling them with statistical functions. Then, because the shift processes of extracted features in aged LEDs are always nonlinear, a nonlinear state-space model is then developed to predict the color shift failure time within a self-adaptive particle filter framework. The results show that: (1 the failure mechanisms of LEDs can be identified by analyzing the extracted features of SPD with statistical curve-fitting and (2 the developed method can dynamically and accurately predict the color coordinates, correlated color temperatures (CCTs, and color rendering indexes (CRIs of phosphor-converted (pc-white LEDs, and also can estimate the residual color life.

  5. Combined daylight and intelligent LED lighting - getting the daylight into the buildings; Kombineret dagslys og intelligent LED belysning - fae dagslys ind i bygningerne. Slutrapport

    Energy Technology Data Exchange (ETDEWEB)

    Dam-Hansen, C.; Corell, D.D.; Thorseth, A.; Behrensdorff Poulsen, P. [Technical Univ. of Denmark, DTU Fotonik, DTU Risoe Campus, Roskilde (Denmark); Markvart, J.; Iversen, A.; Logadottir, A. [Aalborg Univ., Statens Byggeforskningsinstitut (SBi), Koebenhavn (Denmark)

    2013-03-15

    The main result of the project is the construction of the new intelligent and dynamic LED lighting system for demonstration and research purposes, and a number of extensive user testing is completed. The LED lighting system is a total system for office lighting with ceiling fixtures and desk lamps, which has made it possible to create a general and workplace lighting in two offices each with two work places. The system is installed in a day light laboratory for such two office spaces. All lamps can be controlled via a developed computer interface, and the desk lamps are further manually controllable by a user via two buttons for color temperature and brightness, respectively. The new intelligent and dynamic lighting system is based on color mixing LED technology and makes it possible to control the color composition, color coordinates and thus the color temperature of the light. Control-wise, the system is pre-programmed to produce white light with a correlated color temperature from 2700 K to 7000 K. The color composition is optimized from the desire for a very good color given at a general CRI value of 92-97 over the area. The system can be dimmed 20-100 %, with no significant change in the light's color properties. A mini-spectrometer is calibrated and built-in in the system and provides the current estimate of daylight brightness and color temperature through measurement of daylight color scheme in the visible range. The system uses daylight properties to control the light from the LED lighting system. The results of user tests show, that the developed possibility to automatically control of light in the office depending on the daylight color temperature is considered to be equally preferred and results in equally satisfied users as a traditional lighting system with even lighting in the room. On the other hand, user results showed that there were both energy savings and more satisfied users to be gained by providing users the opportunity to self-adjust either

  6. Spectroscopic studies of Dy3 + ion doped tellurite glasses for solid state lasers and white LEDs

    Science.gov (United States)

    Himamaheswara Rao, V.; Syam Prasad, P.; Mohan Babu, M.; Venkateswara Rao, P.; Satyanarayana, T.; Luís F., Santos; Veeraiah, N.

    2018-01-01

    Rare earth ion Dy3 +-doped tellurite glasses were synthesised in the system of (75-x)TeO2-15Sb2O3-10WO3-xDy2O3 (TSWD glasses). XRD and FTIR characterizations were used to find the crystalline and structural properties. The intensities of the electronic transitions and the ligand environment around the Dy3 + ion were determined using the Judd-Ofelt (J-O) theory on the absorption spectra of the glasses. The measured luminescence spectra exhibit intense emissions at 574 and 484 nm along with less intense emissions around 662 and 751 nm. Various radiative properties of the 4F9/2 excited level of Dy3 + ion were calculated for the glasses. Decay profiles were measured to find the life times and quantum efficiencies. Yellow to blue intensity ratio (Y/B), CIE chromaticity coordinates and correlated color temperature (CCT) values are calculated using the emission spectra to evaluate the emitted light. The obtained results suggest the utility of the glasses for potential yellow laser and white LED's applications.

  7. Spectral optimization simulation of white light based on the photopic eye-sensitivity curve

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Qi, E-mail: qidai@tongji.edu.cn [College of Architecture and Urban Planning, Tongji University, 1239 Siping Road, Shanghai 200092 (China); Institute for Advanced Study, Tongji University, 1239 Siping Road, Shanghai 200092 (China); Key Laboratory of Ecology and Energy-saving Study of Dense Habitat (Tongji University), Ministry of Education, 1239 Siping Road, Shanghai 200092 (China); Hao, Luoxi; Lin, Yi; Cui, Zhe [College of Architecture and Urban Planning, Tongji University, 1239 Siping Road, Shanghai 200092 (China); Key Laboratory of Ecology and Energy-saving Study of Dense Habitat (Tongji University), Ministry of Education, 1239 Siping Road, Shanghai 200092 (China)

    2016-02-07

    Spectral optimization simulation of white light is studied to boost maximum attainable luminous efficacy of radiation at high color-rendering index (CRI) and various color temperatures. The photopic eye-sensitivity curve V(λ) is utilized as the dominant portion of white light spectra. Emission spectra of a blue InGaN light-emitting diode (LED) and a red AlInGaP LED are added to the spectrum of V(λ) to match white color coordinates. It is demonstrated that at the condition of color temperature from 2500 K to 6500 K and CRI above 90, such white sources can achieve spectral efficacy of 330–390 lm/W, which is higher than the previously reported theoretical maximum values. We show that this eye-sensitivity-based approach also has advantages on component energy conversion efficiency compared with previously reported optimization solutions.

  8. Spectral optimization simulation of white light based on the photopic eye-sensitivity curve

    International Nuclear Information System (INIS)

    Dai, Qi; Hao, Luoxi; Lin, Yi; Cui, Zhe

    2016-01-01

    Spectral optimization simulation of white light is studied to boost maximum attainable luminous efficacy of radiation at high color-rendering index (CRI) and various color temperatures. The photopic eye-sensitivity curve V(λ) is utilized as the dominant portion of white light spectra. Emission spectra of a blue InGaN light-emitting diode (LED) and a red AlInGaP LED are added to the spectrum of V(λ) to match white color coordinates. It is demonstrated that at the condition of color temperature from 2500 K to 6500 K and CRI above 90, such white sources can achieve spectral efficacy of 330–390 lm/W, which is higher than the previously reported theoretical maximum values. We show that this eye-sensitivity-based approach also has advantages on component energy conversion efficiency compared with previously reported optimization solutions

  9. Zero- and two-dimensional hybrid carbon phosphors for high colorimetric purity white light-emission.

    Science.gov (United States)

    Ding, Yamei; Chang, Qing; Xiu, Fei; Chen, Yingying; Liu, Zhengdong; Ban, Chaoyi; Cheng, Shuai; Liu, Juqing; Huang, Wei

    2018-03-01

    Carbon nanomaterials are promising phosphors for white light emission. A facile single-step synthesis method has been developed to prepare zero- and two-dimensional hybrid carbon phosphors for the first time. Zero-dimensional carbon dots (C-dots) emit bright blue luminescence under 365 nm UV light and two-dimensional nanoplates improve the dispersity and film forming ability of C-dots. As a proof-of-concept application, the as-prepared hybrid carbon phosphors emit bright white luminescence in the solid state, and the phosphor-coated blue LEDs exhibit high colorimetric purity white light-emission with a color coordinate of (0.3308, 0.3312), potentially enabling the successful application of white emitting phosphors in the LED field.

  10. New Silicate Phosphors for a White LED(Electronic Displays)

    OpenAIRE

    Toda, Kenji; Kawakami, Yoshitaka; Kousaka, Shin-ichiro; Ito, Yutaka; Komeno, Akira; Uematsu, Kazuyoshi; Sato, Mineo

    2006-01-01

    We focus on the development of new silicate phosphors for a white LED. In the europium doped silicate system, four LED phosphor candidates-Li_2SrSiO_4:Eu^, Ba_9Sc_2Si_6O_:Eu^, Ca_3Si_2O_7:Eu^ and Ba_2MgSi_2O_7:Eu^ were found. Luminescent properties under near UV and visible excitation were investigated for the new Eu^ doped LED silicate phosphors. These new phosphors have a relatively strong absorption band in a long wavelength region.

  11. Limits of computational white-light holography

    International Nuclear Information System (INIS)

    Mader, Sebastian; Kozacki, Tomasz; Tompkin, Wayne

    2013-01-01

    Recently, computational holograms are being used in applications, where previously conventional holograms were applied. Compared to conventional holography, computational holography is based on imaging of virtual objects instead of real objects, which renders them somewhat more flexibility. Here, computational holograms are calculated based on the superposition of point sources, which are placed at the mesh vertices of arbitrary 3D models. The computed holograms have full parallax and exhibit a problem in viewing that we have called g hosting , which is linked to the viewing of computational holograms based on 3D models close to the image plane. Experimental white-light reconstruction of these holograms showed significant blurring, which is explained here based on simulations of the lateral as well as the axial resolution of a point image with respect to the source spectrum and image distance. In accordance with these simulations, an upper limit of the distance to the image plane is determined, which ensures high quality imaging.

  12. Lifetime prediction of LED lighting systems considering thermal coupling between LED sources and drivers

    DEFF Research Database (Denmark)

    Alfarog, Azzarn Orner; Qu, Xiaohui; Wang, Huai

    2017-01-01

    and accelerate the failure. In this paper, a new thermal model concerning the thermal coupling is proposed with Finite Element Method (FEM) simulation for parameter acquirement. The proposed model has a better estimation of the thermal stresses of key components in the LED lamps and therefore an improved...... separately, and then the thermal design is also optimized independently. In practice, the LED source and driver are usually compacted in a single fixture. The heat dissipated from LED source and driver will be coupled together and affect the heat transfer performance, which may degrade the whole system...

  13. Enhanced Ce{sup 3+} photoluminescence by Li{sup +} co-doping in CaO phosphor and its use in blue-pumped white LEDs

    Energy Technology Data Exchange (ETDEWEB)

    Hao, Zhendong, E-mail: haozd@ciomp.ac.cn; Zhang, Xia; Luo, Yongshi; Zhang, Ligong; Zhao, Haifeng; Zhang, Jiahua, E-mail: zhangjh@ciomp.ac.cn

    2013-08-15

    In this paper, we demonstrate a method to improve the photoluminescence of CaO: Ce{sup 3+} phosphor and delineate its first use in blue-pumped white LEDs. The results show that the yellow emission of Ce{sup 3+} is enhanced by a factor of 1.88 by adding Li{sup +} into CaO host at 474 nm blue light excitation. On analyzing the diffuse reflection spectra and fluorescence decay curves, we reveal that the photoluminescence enhancement is originated from the rise of absorbance to the excitation photons but not from the improvement of the luminescent efficiency. Li{sup +}-improved CaO: Ce{sup 3+} exhibits more red component when it is compared with the commercial Y{sub 3}Al{sub 5}O{sub 12}: Ce{sup 3+} (YAG: Ce{sup 3+}) phosphor, indicating its potential application for high color rendering white LEDs. Thus, a white LED is fabricated by combining blue InGaN LED chip with CaO: Ce{sup 3+}, Li{sup +} phosphor and a warm white light with high color rendering index (R{sub a}) of 80, low correlated color temperature (T{sub c}) of 4524 K, and sufficient luminous efficiency of 50 lm W{sup −1} is obtained. -- Highlights: • The photoluminescence of Ce{sup 3+} in CaO host was enhanced by Li{sup +} co-doping. • A CaO: Ce{sup 3+}, Li{sup +} based white LED was fabricated for the first time. • An efficient warm white light was obtained. • CaO: Ce{sup 3+}, Li{sup +} is expected to be used as a yellow phosphor for blue-pumped white LEDs.

  14. Demonstration Assessment of Light-Emitting Diode (LED) Parking Lot Lighting in Leavenworth, KS

    Energy Technology Data Exchange (ETDEWEB)

    Myer, Michael; Kinzey, Bruce R.; Curry, Ku' uipo

    2011-05-06

    This report describes the process and results of a demonstration of solid-state lighting (SSL) technology in a commercial parking lot lighting application, under the U.S. Department of Energy (DOE) Solid-State Lighting Technology GATEWAY Demonstration Program. The parking lot is for customers and employees of a Walmart Supercenter in Leavenworth, Kansas and this installation represents the first use of the LED Parking Lot Performance Specification developed by the DOE’s Commercial Building Energy Alliance. The application is a parking lot covering more than a half million square feet, lighted primarily by light-emitting diodes (LEDs). Metal halide wall packs were installed along the building facade. This site is new construction, so the installed baseline(s) were hypothetical designs. It was acknowledged early on that deviating from Walmart’s typical design would reduce the illuminance on the site. Walmart primarily uses 1000W pulse-start metal halide (PMH) lamps. In order to provide a comparison between both typical design and a design using conventional luminaires providing a lower illuminance, a 400W PMH design was also considered. As mentioned already, the illuminance would be reduced by shifting from the PMH system to the LED system. The Illuminating Engineering Society of North America (IES) provides recommended minimum illuminance values for parking lots. All designs exceeded the recommended illuminance values in IES RP-20, some by a wider margin than others. Energy savings from installing the LED system compared to the different PMH systems varied. Compared to the 1000W PMH system, the LED system would save 63 percent of the energy. However, this corresponds to a 68 percent reduction in illuminance as well. In comparison to the 400W PMH system, the LED system would save 44 percent of the energy and provide similar minimum illuminance values at the time of relamping. The LED system cost more than either of the PMH systems when comparing initial costs

  15. Savings in Cooling Energy with a Thermal Management System for LED Lighting in Office Buildings

    Directory of Open Access Journals (Sweden)

    Byung-Lip Ahn

    2015-06-01

    Full Text Available Light-emitting diode (LED lighting should be considered for lighting efficiency enhancement, however, waste heat from light-emitting diode (LED lighting increases the internal cooling load during the summer season. In order to solve this problem we propose a thermal management system for light-emitting diode (LED lighting with a heat exchanger module integrated with the building’s heating, ventilation, and air conditioning (HVAC system to move the lighting’s waste heat outdoors. An experiment was carried out to investigate the thermal effects in a test chamber and the heat exchange rate between the heat sink and the duct air. The heat generated by the light-emitting diode (LED lighting was calculated as 78.1% of light-emitting diode (LED input power and the heat exchange rate of the lighting heat exchange module was estimated to be between 86.5% and 98.1% according to the light-emitting diode (LED input power and the flow rate of air passing the heat sink. As a result, the average light-emitting diode (LED lighting heat contribution rate for internal heat gain was determined as 0.05; this value was used to calculate the heating and cooling energy demand of the office building through an energy simulation program. In the simulation results, the cooling energy demand was reduced by 19.2% compared with the case of conventionally installed light-emitting diode (LED lighting.

  16. Fundamentals of solid-state lighting LEDs, OLEDs, and their applications in illumination and displays

    CERN Document Server

    Khanna, Vinod Kumar

    2014-01-01

    History and Basics of LightingChronological History of LightingLearning Objectives How Early Man Looked at the ""Sun"" The Need for Artificial Light Sources First Steps in the Evolution of Artificial Lighting The First Solid-State Lighting Device The First Practical Electrical Lighting Device The Incandescent Filament Lamp Mercury and Sodium Vapor Lamps The Fluorescent Lamp The Compact Fluorescent Lamp Revolution in the World of Lighting: Advent of Light-Emitting Diodes Birth of the First LED and the Initial Stages of LED Development The Father of the LED: Holonyak Jr. The Post-1962 Developmen

  17. The Development of LED-Based Dental Light Using a Multiplanar Reflector Design

    Directory of Open Access Journals (Sweden)

    Chi-Chang Hsieh

    2014-01-01

    Full Text Available A multiplanar reflector was designed to enhance the application efficiency of light-emitting diode (LED light sources that can be employed as LED-based dental lights. This study used a high-power LED developed by Nichia, that is, a single LED capable of providing a total luminous flux of 120 lm, as the primarily light source to design and develop an LED-based dental light. This LED complies with the international standards and regulations stipulated in ISO 9680:2007. The light spots produced by the prototype were rectangular, with a length of 200 mm and a width of 100 mm. These light spots achieved maximum illumination of 12,000 lux. The use of LEDs can reduce energy consumption from 50 W to 3 W, providing an energy saving of more than 90%.

  18. Molecular Beam Epitaxy-Grown InGaN Nanomushrooms and Nanowires for White Light Source Applications

    KAUST Repository

    Gasim, Anwar A.; Bhattacharya, Pallab K.; Cha, Dong Kyu; Ng, Tien Khee; Ooi, Boon S.

    2012-01-01

    We report the observation of coexisting InGaN nanomushrooms and nanowires grown via MBE. Photoluminescence characterization shows that the nanostructures emit yellow and blue light, respectively. The combined emission is promising for white-LEDs.

  19. Demonstration Assessment of Light-Emitting Diode (LED) Roadway Lighting on Lija Loop in Portland, OR

    International Nuclear Information System (INIS)

    Kinzey, Bruce R.; Myer, Michael

    2009-01-01

    This report describes the process and results of a demonstration of solid-state lighting (SSL) technology in a residential street lighting application, under the U.S. Department of Energy GATEWAY Solid-State Lighting Technology Demonstration Program. In this project, eight 100W (nominal) high-pressure sodium cobra head fixtures were replaced with a like number of LED street light luminaires manufactured by Leotek, Inc. The Leotek product achieved an estimated payback in the Lija Loop installation of about 20 years for replacement scenarios and a much shorter 7.6 years for new installations. Much of the associated energy savings (55%) supporting these payback periods, however, were achieved by reducing average horizontal photopic illuminance a similar amount (53%). Examined from a different perspective, the measured performance suggests that the Leotek product is at approximate parity with the HPS cobra head in terms of average delivered photopic illumination for a given power consumption. HPS comprises the second most efficacious street lighting technology available, exceeded only by low pressure sodium (LPS). LPS technology is not considered suitable for most street lighting applications due to its monochromatic spectral output and poor color rendering ability; therefore, this LED product is performing at an efficiency level comparable to its primary competition in this application.

  20. GATEWAY Report Brief: Tunable-White Lighting at the ACC Care Center

    Energy Technology Data Exchange (ETDEWEB)

    None, None

    2016-09-30

    Summary of a GATEWAY program report that documented the performance of tunable-white LED lighting systems installed in several spaces within the ACC Care Center, a senior-care facility in Sacramento, CA. The project results included energy savings and improved lighting quality, as well as other possible health-related benefits that may have been attributable, at least in part, to the lighting changes.

  1. CdSe white quantum dots-based white light-emitting diodes with high color rendering index

    Science.gov (United States)

    Su, Yu-Sheng; Hsiao, Chih-Chun; Chung, Shu-Ru

    2016-09-01

    A white light emission CdSe quantum dots (QDs) can be prepared by chemical route under 180°C. An organic oleic acid (OA) is used to react with CdO to form Cd-OA complex. Hexadecylamine (HDA) and 1-Octadecene (ODE) were used as co-surfactants. By controlling the reaction time, a white light emission CdSe QDs can be obtained after reacts for 3 to 10 min. The luminescence spectra compose two obvious emission peaks and entire visible light ranges from 400 to 650 nm. Based on TEM measurement result, spherical morphologies with particle size 2.39+/-0.27 nm can be obtained. The quantum yields (QYs) of white CdSe QD are between 20 and 60 %, which depends on reaction time. A white CdSe QDs were mixed with UV cured gel (OPAS-226) with weight ratios 50.0 wt. %, and putted the mixture into reflective cup (3020, 13 mil) as convert type. The white LEDs have controllable CIE coordinates and correlated color temperature (CCT). The luminous efficacy of the device is less than 3 lm/W, but the color rendering index (CRI) for all devices are higher than 80. Since the luminous efficacy of hybrid devices has a direct dependence on the external QY of the UV-LED as well, the luminous efficacy can be improved by well dispersion of CdSe QDs in UV gel matrix and using optimized LED chips. Therefore, in this study, we provide a new and simple method to prepare high QY of white CdSe QDs and its have a potential to applicate in solid-state lighting.

  2. Light emitting diodes (LED): applications in forest and native plant nurseries

    Science.gov (United States)

    Thomas D. Landis; Jeremiah R. Pinto; R. Kasten Dumroese

    2013-01-01

    It was quotes like this that made us want to learn more about light emitting diodes (LED). Other than knowing that LEDs were the latest innovation in artificial lighting, we knew that we had a lot to learn. So we started by reviewing some of the basics. The following review is a brief synopsis of how light affects plants and some discussion about LED lighting. If you...

  3. Non-imaging optics for LED-lighting

    NARCIS (Netherlands)

    Berg, van den J.B.; Castro, R.M.; Draisma, J.; Evers, J.H.M.; Hendriks, M.; Krehel, O.; Kryven, I.; Mora, K.; Szabó, B.T.; Zwiernik, P.W.; Boon, M.A.A.

    2013-01-01

    In this report, several methods are investigated to rapidly compute the light intensity function, either in the far field or on a finite-distance screen, of light emanating from a light fixture with a given shape. Different shapes are considered, namely polygonal and (piecewise) smooth. In the first

  4. Luminescent features of sol–gel derived rare-earth multi-doped oxyfluoride nano-structured phosphors for white LED application

    International Nuclear Information System (INIS)

    Gouveia-Neto, A.S.; Silva, A.F. da; Bueno, L.A.; Costa, E.B. da

    2012-01-01

    Rare-earth doped oxyfluoride 75SiO 2 :25PbF 2 nano-structured phosphors for white-light-emitting diodes were synthesized by thermal treatment of precursor sol–gel derived glasses. Room temperature luminescence features of Eu 3+ , Sm 3+ , Tb 3+ , Eu 3+ /Tb 3+ , and Sm 3+ /Tb 3+ ions incorporated into low-phonon-energy PbF 2 nanocrystals dispersed in the aluminosilicate glass matrix and excited with UV light emitting diode were investigated. The luminescence spectra exhibited strong emission signals in the red (600, 610, 625, and 646 nm), green (548 and 560 nm), and blue (485 nm) wavelength regions. White-light emission was observed in Sm/Tb and Eu/Tb double-doped activated phosphors employing UV-LED excitation at 395 nm. The dependence of the luminescence emission intensities upon annealing temperature and rare-earth concentration was also examined. The results indicated that there exist optimum annealing temperature and activator ion concentration in order to obtain intense visible emission light with high color rendering index. The study suggests that the nanocomposite phosphor based upon 75SiO 2 :25PbF 2 host herein reported is a promising contender for white-light LED applications. - Highlights: ► White-light emission in double-doped activated phosphors employing UV-LED excitation. ► Luminescent features of europium, samarium, and terbium in nanocrystals dispersed in aluminosilicate glass. ► New nanocomposite phosphor host for white-light LED applications.

  5. Effect of LED lighting on the cooling and heating loads in office buildings

    International Nuclear Information System (INIS)

    Ahn, Byung-Lip; Jang, Cheol-Yong; Leigh, Seung-Bok; Yoo, Seunghwan; Jeong, Hakgeun

    2014-01-01

    Highlights: • Application of heat control strategy reduces total energy consumption of LED lighting. • Convective heat from LED lighting should be emitted outdoors during cooling period. • Seasonal optimization of convective heat lowers total energy consumption. - Abstract: LED lighting has the potential to provide energy savings, and in many countries, there are policies to encourage its use owing to its higher efficiency and longer life in comparison to other lighting fixtures. However, since 75–85% of the light electric power in LED lights is still generated as heat, the sole use of LED lighting in a building could have a negative effect on the cooling load. In this paper, we study the heating properties of LED lighting and establish a management strategy to exploit these properties to reduce the energy used for heating and cooling of buildings. Using a simulation program, the energy consumption of the Green Building in Daejeon, Korea, and the virtual building provided by the U.S. Department of Energy (DOE) was computed according for different light fixtures. A control strategy is more applicable to LED lighting than to general fluorescent lighting, especially for the cooling of a building, because the use of a return-air duct and the heat sinks on the LED fixtures allow the heat to be better directed. Deployment of LED lights in combination with such a control strategy can help to increase the energy efficiency of a building

  6. LED intense headband light source for fingerprint analysis

    Science.gov (United States)

    Villa-Aleman, Eliel

    2005-03-08

    A portable, lightweight and high-intensity light source for detecting and analyzing fingerprints during field investigation. On-site field analysis requires long hours of mobile analysis. In one embodiment, the present invention comprises a plurality of light emitting diodes; a power source; and a personal attachment means; wherein the light emitting diodes are powered by the power source, and wherein the power source and the light emitting diodes are attached to the personal attachment means to produce a personal light source for on-site analysis of latent fingerprints. The present invention is available for other applications as well.

  7. Catalyst-free activation of peroxides under visible LED light irradiation through photoexcitation pathway

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Yaowen [Department of Environmental Engineering, Wuhan University, Wuhan, 430079 (China); Shenzhen Research Institute of Wuhan University, Shenzhen, 518057 (China); Li, Yixi; Yao, Linyu; Li, Simiao; Liu, Jin [Department of Environmental Engineering, Wuhan University, Wuhan, 430079 (China); Zhang, Hui, E-mail: eeng@whu.edu.cn [Department of Environmental Engineering, Wuhan University, Wuhan, 430079 (China); Shenzhen Research Institute of Wuhan University, Shenzhen, 518057 (China)

    2017-05-05

    Highlights: • Persulfate could decolorize Rhodamine B (RhB) directly via non-radical reactions. • LED lamps emitting white light were utilized as the visible light source. • Dyes could activate peroxides through photoexcitation pathway. • Decolorization of dyes and production of radicals were achieved simultaneously. • The catalyst-free peroxide/dye/Vis process was effective in a broad pH range. - Abstract: Catalysts are known to activate peroxides to generate active radicals (i.e., hydroxyl radical (·OH) and sulfate radical (SO{sub 4}·{sup −})) under certain conditions, but the activation of peroxides in the absence of catalysts under visible light irradiation has been rarely reported. This work demonstrates a catalyst-free activation of peroxides for the generation of ·OH and/or SO{sub 4}·{sup −} through photoexcited electron transfer from organic dyes to peroxides under visible LED light irradiation, where Rhodamine B (RhB) and Eosin Y (EY) were selected as model dyes. The formation of ·OH and/or SO{sub 4}·{sup −} in the reactions and the electron transfer from the excited dyes to peroxides were validated via electron paramagnetic resonance (EPR), photoluminescence (PL) spectra and cyclic voltammetry (CV). The performance of the peroxide/dye/Vis process was demonstrated to be altered depending on the target substrate. Meanwhile, the peroxide/dye/Vis process was effective for simultaneous decolorization of dyes and production of active radicals under neutral even or basic conditions. The findings of this study clarified a novel photoexcitation pathway for catalyst-free activation of peroxides under visible light irradiation, which could avoid the secondary metal ion (dissolved or leached) pollution from the metal-based catalysts and expand the application range of the peroxide-based catalytic process.

  8. Bonding bare die LEDs on PET foils for lighting applications: Thermal design modeling and bonding experiments

    NARCIS (Netherlands)

    Ende, D.A. van den; Kusters, R.H.L.; Cauwe, M.; Waal, A. van der; Brand, J. van den

    2012-01-01

    Integration of LEDs on flexible foil substrates is of interest for flexible lighting applications and flexible photonic devices. A matrix of LEDs on a foil combined with a diffuser can be a potential alternative for flexible OLED lighting devices. Preferably, these LEDs are integrated in an

  9. Large area flexible lighting foils using distributed bare LED dies on polyester substrates

    NARCIS (Netherlands)

    Ende, D.A. van den; Kusters, R.H.L.; Cauwe, M.; Waal, A. van der; Brand, J. van den

    2013-01-01

    Integration of LEDs on flexible foil substrates is of interest for flexible lighting applications and for backlights for flexible displays. Such a large area lighting device can be made by integrating a matrix of closely spaced LEDs on a flexible foil substrate. Preferably, these LEDs are integrated

  10. Bivariate constant stress degradation model: LED lighting system reliability estimation with two-stage modelling

    NARCIS (Netherlands)

    Sari, J.K.; Newby, M.J.; Brombacher, A.C.; Tang, L.C.

    2009-01-01

    Light-emitting diode (LED) lamp has received great attention as a potential replacement for the more commercially available lighting technology, such as incandescence and fluorescence lamps. LED which is the main component of LED lamp has a very long lifetime. This means that no or very few failures

  11. Light Emitting Diode (LED) circular traffic signal lifetime management system.

    Science.gov (United States)

    2011-02-01

    The objective of this research is to build lifetime curves for red, yellow, and green LED circular traffic signals through 20,000-hr. accelerated stress testing of samples operating under Louisianas environmental conditions.

  12. LED Retrofit Kits, TLEDs, and Lighting Controls: An Application Guide

    Energy Technology Data Exchange (ETDEWEB)

    None

    2017-03-01

    This document provides guidance for retrofitting existing fluorescent troffers including the LED and associated control options available, the pro/cons and costs/benefits of each option, and agency specific requirements (where applicable).

  13. Biological Research in Canisters (BRIC) - Light Emitting Diode (LED)

    Science.gov (United States)

    Levine, Howard G.; Caron, Allison

    2016-01-01

    The Biological Research in Canisters - LED (BRIC-LED) is a biological research system that is being designed to complement the capabilities of the existing BRIC-Petri Dish Fixation Unit (PDFU) for the Space Life and Physical Sciences (SLPS) Program. A diverse range of organisms can be supported, including plant seedlings, callus cultures, Caenorhabditis elegans, microbes, and others. In the event of a launch scrub, the entire assembly can be replaced with an identical back-up unit containing freshly loaded specimens.

  14. Thermal behavior of a quantum dot nanocomposite as a color converting material and its application to white LED

    Energy Technology Data Exchange (ETDEWEB)

    Woo, Ju Yeon; Kim, Kyung Nam; Jeong, Sohee; Han, Chang-Soo, E-mail: cshan@kimm.re.kr [Nano-Mechanical Systems Research division, Korea Institute of Machinery and Materials (KIMM), Daejeon 305343 (Korea, Republic of)

    2010-12-10

    We present a novel nanocomposite, a mixture of a CdSe/CdS/ZnS red quantum dot (QD), an Sr{sub 2}SiO{sub 4}:Eu green phosphor and silicone resin for a color converting material. The temperature rise and the optical characteristics of the nanocomposite due to the addition of the QD have been investigated in terms of QD content ratio and the mixing components. The experimental results suggested that a small addition of QDs generated a large amount of heat during light conversion at the wavelength of QD emission. Considering the temperature rise in a nanocomposite, we applied 0.2 wt% QDs on an InGaN blue LED chip. As a result, we could achieve a white LED device with a high color rendering index of 83.2, a high luminance of 65.86 lm W{sup -1} and a moderate temperature increase of 94 deg. C. The white LED converted by the newly developed QD-phosphor nanocomposite has great potential in future illumination.

  15. Demonstration Assessment of Light-Emitting Diode (LED) Roadway Lighting, I-35W Bridge, Minneapolis, Minnesota, Phase I Report

    Energy Technology Data Exchange (ETDEWEB)

    Kinzey, B. R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Myer, M. A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2009-08-01

    On the I-35W Bridge in Minneapolis, Minnesota, the GATEWAY program conducted a two-phase demonstration of LED roadway lighting on the main span, which is one of the country's oldest continuously operated exterior LED lighting installations. The Phase I report provides an overview of initial project results including lighting performance, economic performance, and potential energy savings.

  16. The Use of Light-Emitting Diodes (LEDs) as Green and Red/Far-Red Light Sources in Plant Physiology.

    Science.gov (United States)

    Jackson, David L.; And Others

    1985-01-01

    The use of green, red, and far-red light-emitting diodes (LEDs) as light sources for plant physiological studies is outlined and evaluated. Indicates that LED lamps have the advantage over conventional light sources in that they are lightweight, low-cost, portable, easily constructed, and do not require color filters. (Author/DH)

  17. Conduction-driven cooling of LED-based automotive LED lighting systems for abating local hot spots

    Science.gov (United States)

    Saati, Ferina; Arik, Mehmet

    2018-02-01

    Light-emitting diode (LED)-based automotive lighting systems pose unique challenges, such as dual-side packaging (front side for LEDs and back side for driver electronics circuit), size, harsh ambient, and cooling. Packaging for automotive lighting applications combining the advanced printed circuit board (PCB) technology with a multifunctional LED-based board is investigated with a focus on the effect of thermal conduction-based cooling for hot spot abatement. A baseline study with a flame retardant 4 technology, commonly known as FR4 PCB, is first compared with a metal-core PCB technology, both experimentally and computationally. The double-sided advanced PCB that houses both electronics and LEDs is then investigated computationally and experimentally compared with the baseline FR4 PCB. Computational models are first developed with a commercial computational fluid dynamics software and are followed by an advanced PCB technology based on embedded heat pipes, which is computationally and experimentally studied. Then, attention is turned to studying different heat pipe orientations and heat pipe placements on the board. Results show that conventional FR4-based light engines experience local hot spots (ΔT>50°C) while advanced PCB technology based on heat pipes and thermal spreaders eliminates these local hot spots (ΔT<10°C), leading to a higher lumen extraction with improved reliability. Finally, possible design options are presented with embedded heat pipe structures that further improve the PCB performance.

  18. Blue light filtered white light induces depression-like responses and temporary spatial learning deficits in rats.

    Science.gov (United States)

    Meng, Qinghe; Lian, Yuzheng; Jiang, Jianjun; Wang, Wei; Hou, Xiaohong; Pan, Yao; Chu, Hongqian; Shang, Lanqin; Wei, Xuetao; Hao, Weidong

    2018-04-18

    Ambient light has a vital impact on mood and cognitive functions. Blue light has been previously reported to play a salient role in the antidepressant effect via melanopsin. Whether blue light filtered white light (BFW) affects mood and cognitive functions remains unclear. The present study aimed to investigate whether BFW led to depression-like symptoms and cognitive deficits including spatial learning and memory abilities in rats, and whether they were associated with the light-responsive function in retinal explants. Male Sprague-Dawley albino rats were randomly divided into 2 groups (n = 10) and treated with a white light-emitting diode (LED) light source and BFW light source, respectively, under a standard 12 : 12 h L/D condition over 30 days. The sucrose consumption test, forced swim test (FST) and the level of plasma corticosterone (CORT) were employed to evaluate depression-like symptoms in rats. Cognitive functions were assessed by the Morris water maze (MWM) test. A multi-electrode array (MEA) system was utilized to measure electro-retinogram (ERG) responses induced by white or BFW flashes. The effect of BFW over 30 days on depression-like responses in rats was indicated by decreased sucrose consumption in the sucrose consumption test, an increased immobility time in the FST and an elevated level of plasma CORT. BFW led to temporary spatial learning deficits in rats, which was evidenced by prolonged escape latency and swimming distances in the spatial navigation test. However, no changes were observed in the short memory ability of rats treated with BFW. The micro-ERG results showed a delayed implicit time and reduced amplitudes evoked by BFW flashes compared to the white flash group. BFW induces depression-like symptoms and temporary spatial learning deficits in rats, which might be closely related to the impairment of light-evoked output signals in the retina.

  19. High-power LED light sources for optical measurement systems operated in continuous and overdriven pulsed modes

    Science.gov (United States)

    Stasicki, Bolesław; Schröder, Andreas; Boden, Fritz; Ludwikowski, Krzysztof

    2017-06-01

    The rapid progress of light emitting diode (LED) technology has recently resulted in the availability of high power devices with unprecedented light emission intensities comparable to those of visible laser light sources. On this basis two versatile devices have been developed, constructed and tested. The first one is a high-power, single-LED illuminator equipped with exchangeable projection lenses providing a homogenous light spot of defined diameter. The second device is a multi-LED illuminator array consisting of a number of high-power LEDs, each integrated with a separate collimating lens. These devices can emit R, G, CG, B, UV or white light and can be operated in pulsed or continuous wave (CW) mode. Using an external trigger signal they can be easily synchronized with cameras or other devices. The mode of operation and all parameters can be controlled by software. Various experiments have shown that these devices have become a versatile and competitive alternative to laser and xenon lamp based light sources. The principle, design, achieved performances and application examples are given in this paper.

  20. Assessing the use of Low Voltage UV-light Emitting Miniature LEDs for Marine Biofouling Control

    Science.gov (United States)

    2016-07-01

    of that required to drive traditional UV mercury lamps . Secondly, given their small size and relatively low cost, UV LEDs provide ease of maintenance...UNCLASSIFIED UNCLASSIFIED Assessing the use of Low Voltage UV -light Emitting Miniature LEDs for Marine Biofouling Control Richard...settling organisms. The introduction of miniature UV light emitting diodes ( LEDs ) as a light source enables them to be embedded into thin, flexible

  1. Liquid cooling applications on automotive exterior LED lighting

    Science.gov (United States)

    Aktaş, Mehmet; Şenyüz, Tunç; Şenyıldız, Teoman; Kılıç, Muhsin

    2018-02-01

    In this study cooling of a LED unit with heatsink and liquid cooling block which is used in automotive head lamp applications has been investigated numerically and experimentally. Junction temperature of a LED which is cooled with heatsink and liquid cooling block obtained in the experiment. 23°C is used both in the simulation and the experiment phase. Liquid cooling block material is choosed aluminium (Al) and polyamide. All tests and simulation are performed with three different flow rate. Temperature distribution of the designed product is investigated by doing the numerical simulations with a commercially software. In the simulations, fluid flow is assumed to be steady, incompressible and laminar and 3 dimensional (3D) Navier-Stokes equations are used. According to the calculations it is obtained that junction temperature is higher in the heatsink design compared to block cooled one. By changing the block material, it is desired to investigate the variation on the LED junction temperature. It is found that more efficient cooling can be obtained in block cooling by using less volume and weight. With block cooling lifetime of LED can be increased and flux loss can be decreased with the result of decreased junction temperature.

  2. Energy Efficient LED Spectrally Matched Smart Lighting, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Innovative Imaging and Research and the University of Houston Clear Lake have teamed to develop a widely extensible, affordable, energy efficient, smart lighting...

  3. GATEWAY Demonstrations: Exterior LED Lighting Projects at Princeton University

    Energy Technology Data Exchange (ETDEWEB)

    Davis, Robert G. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Evans, WIlliam E. [Princeton Univ., NJ (United States); Murphy, Arthur [Princeton Univ., NJ (United States); Perrin, Tess [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2015-10-30

    This report focuses on four exterior solid-state lighting projects that have been completed at Princeton since 2008, when the University adopted a comprehensive sustainability plan. Through these initial projects – which include a parking garage, a pedestrian path, and two parking lot installations – the school’s facilities engineering staff learned important lessons about SSL technology and gained experience in dealing with the rapidly changing landscape of lighting manufacturers and their suppliers.

  4. Life-Cycle Assessment of Energy and Environmental Impacts of LED Lighting Products, Part 3: LED Environmental Testing

    Energy Technology Data Exchange (ETDEWEB)

    Tuenge, Jason R.; Hollomon, Brad; Dillon, Heather E.; Snowden-Swan, Lesley J.

    2013-03-01

    This report covers the third part of a larger U.S. Department of Energy (DOE) project to assess the life-cycle environmental and resource impacts in the manufacturing, transport, use, and disposal of light-emitting diode (LED) lighting products in relation to incumbent lighting technologies. All three reports are available on the DOE website (www.ssl.energy.gov/tech_reports.html). • Part 1: Review of the Life-Cycle Energy Consumption of Incandescent, Compact Fluorescent and LED Lamps; • Part 2: LED Manufacturing and Performance; • Part 3: LED Environmental Testing. Parts 1 and 2 were published in February and June 2012, respectively. The Part 1 report included a summary of the life-cycle assessment (LCA) process and methodology, provided a literature review of more than 25 existing LCA studies of various lamp types, and performed a meta-analysis comparing LED lamps with incandescent and compact fluorescent lamps (CFLs). Drawing from the Part 1 findings, Part 2 performed a more detailed assessment of the LED manufacturing process and used these findings to provide a comparative LCA taking into consideration a wider range of environmental impacts. Both reports concluded that the life-cycle environmental impact of a given lamp is dominated by the energy used during lamp operation—the upstream generation of electricity drives the total environmental footprint of the product. However, a more detailed understanding of end-of-life disposal considerations for LED products has become increasingly important as their installation base has grown. The Part 3 study (reported herein) was undertaken to augment the LCA findings with chemical analysis of a variety of LED, CFL, and incandescent lamps using standard testing procedures. A total of 22 samples, representing 11 different models, were tested to determine whether any of 17 elements were present at levels exceeding California or Federal regulatory thresholds for hazardous waste. Key findings include: • The selected

  5. Demonstration Assessment of LED Roadway Lighting: Philadelphia, PA

    Energy Technology Data Exchange (ETDEWEB)

    Royer, Michael P.; Tuenge, Jason R.; Poplawski, Michael E.

    2012-09-01

    For this demonstration assessment, 10 different groups of LED luminaires were installed at three sites in Philadelphia, PA. Each of the three sites represented a different set of conditions, most importantly with regard to the incumbent HPS luminaires, which were nominally 100 W, 150 W, and 250 W. The performance of each product was evaluated based on manufacturer data, illuminance calculations, field measurements of illuminance, and the subjective impressions of both regular and expert observers.

  6. Color homogeneity in LED spotlights

    NARCIS (Netherlands)

    Prins, C.R.

    2013-01-01

    Color variation in the light output of white LEDs is a common problem in LED lighting. We aim to design LED spotlights with a uniform color output while keeping the cost of the system low and the energy efficiency high. Therefore we design a special optic to eliminate the color variation of the LED.

  7. Smart street lighting : The advantages of LED street lighting and a smart control system in Uppsala municipality

    OpenAIRE

    Sjöberg, Inga; Gidén Hember, Amanda; Wallerström, Carolina

    2017-01-01

    The purpose of this bachelor thesis is to examine how LED street lights and a smart street light control system can reduce the energy consumption, costs and in extension the CO2 equivalents in a geographically delimited area. In 2015 the municipality of Sala installed LED armatures connected to a smart control system in the whole municipality. The smart control system enables for instance adjustment of the light intensity at specific times during the day and a supervision of the street light ...

  8. Efficient and versatile light. LEDs save energy and open up manifold possibilities of design; Effizientes und vielseitiges Licht. LEDs sparen Energie und eroeffnen zahlreiche Designmoeglichkeiten

    Energy Technology Data Exchange (ETDEWEB)

    Fiebig, Michael [OSRAM Opto Semicondutors GmbH, Muenchen (Germany). Bereich Marketing und Business Development

    2010-07-01

    Light bulbs leave the European market step by step. These conventional light sources are too inefficient in the private and conventional sector. There are a lot of alternatives to light bulbs. But no technology will be able to save as much energy as light emitting diodes (LED) in the future. Today, these LEDs meet us in most different applications. Continuously new areas of application are opened up in order to reduce the power requirement clearly for the production of artificial light. Apart from energy conservation diodes also enable untold possibilities. In the future, light can be still more flexibly used owing to LED. LEDs are ideal light sources for planners and designers.

  9. The PV LED Engine - a new generation of intelligent solar powered LED lighting

    DEFF Research Database (Denmark)

    Poulsen, Peter Behrensdorff; Thorsteinsson, Sune

    parameters are ltered mathematical by the optical properties of the materials in front of the solar panel and assumptions about the soiling parameters. Lab measurements of solar cells/panels underdierent lighting conditions (spectrally and intensity) makes it possible to simulate performance of realsolar...... projectat design and simulation tool for small PV applications for the urban environment is developed. The tool is advanced in its calculations on the solar irradiation parameters being very dierent in the urban environment compared to roof top applications both spectrally and in intensity variations...... panels of different technologies in the addressed environment since detailed electrical characteristicsis known by the measurements. Optical parameters for the protection layer (in front of the solar panel)are put into a material library so the optimal choice can be made for a given application...

  10. Spatial layout optimization design of multi-type LEDs lighting source based on photoelectrothermal coupling theory

    Science.gov (United States)

    Xue, Lingyun; Li, Guang; Chen, Qingguang; Rao, Huanle; Xu, Ping

    2018-03-01

    Multiple LED-based spectral synthesis technology has been widely used in the fields of solar simulator, color mixing, and artificial lighting of plant factory and so on. Generally, amounts of LEDs are spatially arranged with compact layout to obtain the high power density output. Mutual thermal spreading among LEDs will produce the coupled thermal effect which will additionally increase the junction temperature of LED. Affected by the Photoelectric thermal coupling effect of LED, the spectrum of LED will shift and luminous efficiency will decrease. Correspondingly, the spectral synthesis result will mismatch. Therefore, thermal management of LED spatial layout plays an important role for multi-LEDs light source system. In the paper, the thermal dissipation network topology model considering the mutual thermal spreading effect among the LEDs is proposed for multi-LEDs system with various types of power. The junction temperature increment cased by the thermal coupling has the great relation with the spatial arrangement. To minimize the thermal coupling effect, an optimized method of LED spatial layout for the specific light source structure is presented and analyzed. The results showed that layout of LED with high-power are arranged in the corner and low-power in the center. Finally, according to this method, it is convenient to determine the spatial layout of LEDs in a system having any kind of light source structure, and has the advantages of being universally applicable to facilitate adjustment.

  11. Nanopatterned yttrium aluminum garnet phosphor incorporated film for high-brightness GaN-based white light emitting diodes

    International Nuclear Information System (INIS)

    Cho, Joong-yeon; Park, Sang-Jun; Ahn, Jinho; Lee, Heon

    2014-01-01

    In this study, we fabricated high-brightness white light emitting diodes (LEDs) by developing a nanopatterned yttrium aluminum garnet (YAG) phosphor-incorporated film. White light can be obtained by mixing blue light from a GaN-based LED and yellow light of the YAG phosphor-incorporated film. If white light sources can be fabricated by exciting proper yellow phosphor using blue light, then these sources can be used instead of the conventional fluorescent lamps with a UV source, for backlighting of displays. In this work, a moth-eye structure was formed on the YAG phosphor-incorporated film by direct spin-on glass (SOG) printing. The moth-eye structures have been investigated to improve light transmittance in various optoelectronic devices, including photovoltaic solar cells, light emitting diodes, and displays, because of their anti-reflection property. Direct SOG printing, which is a simple, easy, and relatively inexpensive process, can be used to fabricate nanoscale structures. After direct SOG printing, the moth-eye structure with a diameter of 220 nm was formed uniformly on the YAG phosphor-incorporated film. As a result of moth-eye patterning on the YAG phosphor-incorporated film, the light output power of a white LED with a patterned YAG phosphor-incorporated film increased to up to 13% higher than that of a white LED with a non-patterned film. - Highlights: • GaN-based high-brightness white LED was prepared using patterned YAG phosphor-incorporated films. • Direct hydrogen silsesquioxane printing was used to form moth-eye patterns on the YAG films. • The electroluminescence intensity of the white LED was enhanced by up to 14.9%

  12. Nanopatterned yttrium aluminum garnet phosphor incorporated film for high-brightness GaN-based white light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Joong-yeon; Park, Sang-Jun [Department of Materials Science and Engineering, Korea University, Seoul 136-713 (Korea, Republic of); Ahn, Jinho, E-mail: jhahn@hanyang.ac.kr [Department of Material Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Lee, Heon, E-mail: heonlee@korea.ac.kr [Department of Materials Science and Engineering, Korea University, Seoul 136-713 (Korea, Republic of)

    2014-11-03

    In this study, we fabricated high-brightness white light emitting diodes (LEDs) by developing a nanopatterned yttrium aluminum garnet (YAG) phosphor-incorporated film. White light can be obtained by mixing blue light from a GaN-based LED and yellow light of the YAG phosphor-incorporated film. If white light sources can be fabricated by exciting proper yellow phosphor using blue light, then these sources can be used instead of the conventional fluorescent lamps with a UV source, for backlighting of displays. In this work, a moth-eye structure was formed on the YAG phosphor-incorporated film by direct spin-on glass (SOG) printing. The moth-eye structures have been investigated to improve light transmittance in various optoelectronic devices, including photovoltaic solar cells, light emitting diodes, and displays, because of their anti-reflection property. Direct SOG printing, which is a simple, easy, and relatively inexpensive process, can be used to fabricate nanoscale structures. After direct SOG printing, the moth-eye structure with a diameter of 220 nm was formed uniformly on the YAG phosphor-incorporated film. As a result of moth-eye patterning on the YAG phosphor-incorporated film, the light output power of a white LED with a patterned YAG phosphor-incorporated film increased to up to 13% higher than that of a white LED with a non-patterned film. - Highlights: • GaN-based high-brightness white LED was prepared using patterned YAG phosphor-incorporated films. • Direct hydrogen silsesquioxane printing was used to form moth-eye patterns on the YAG films. • The electroluminescence intensity of the white LED was enhanced by up to 14.9%.

  13. Demonstration Assessment of Light-Emitting Diode (LED) Post-Top Lighting at Central Park in New York City

    Energy Technology Data Exchange (ETDEWEB)

    Myer, Michael; Goettel, Russell T.; Kinzey, Bruce R.

    2012-09-30

    A review of five post-top light-emitting diode (LED) pedestrian luminaires installed in New York City's Central Park for possible replacement to the existing metal halide post-top luminaire. This report reviews the energy savings potential and lighting delivered by the LED post-top luminaires.

  14. Solution of multi-element LED light sources development automation problem

    Science.gov (United States)

    Chertov, Aleksandr N.; Gorbunova, Elena V.; Korotaev, Valery V.; Peretyagin, Vladimir S.

    2014-09-01

    The intensive development of LED technologies resulted in the creation of multicomponent light sources in the form of controlled illumination devices based on usage of mentioned LED technologies. These light sources are used in different areas of production (for example, in the food industry for sorting products or in the textile industry for quality control, etc.). The use of LED lighting products in the devices used in specialized lighting, became possible due to wide range of colors of light, LED structures (which determines the direction of radiation, the spatial distribution and intensity of the radiation, electrical, heat, power and other characteristics), and of course, the possibility of obtaining any shade in a wide dynamic range of brightness values. LED-based lighting devices are notable for the diversity of parameters and characteristics, such as color radiation, location and number of emitters, etc. Although LED technologies have several advantages, however, they require more attention if you need to ensure a certain character of illumination distribution and/or distribution of the color picture at a predetermined distance (for example, at flat surface, work zone, area of analysis or observation). This paper presents software designed for the development of the multicomponent LED light sources. The possibility of obtaining the desired color and energy distribution at the zone of analysis by specifying the spatial parameters of the created multicomponent light source and using of real power, spectral and color parameters and characteristics of the LEDs is shown as well.

  15. Communications and sensing of illumination contributins in a power LED lighting system

    NARCIS (Netherlands)

    Linnartz, J.P.M.G.; Feri, L.; Yang, Hongming; Colak, S.B.; Schenk, T.C.W.

    2008-01-01

    In recent years, LED technology emerged as a prime candidate for the future illumination light source, due to high energy efficiency and long life time. In addition, LEDs offer a superior flexibility in terms of colors and shapes, which leads to a potentially infinite variety of available light

  16. GATEWAY Demonstrations: Philadelphia International Airport Apron Lighting: LED System Performance in a Trial Installation

    Energy Technology Data Exchange (ETDEWEB)

    Davis, Robert G. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Wilkerson, Andrea M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2015-10-30

    This report documents a trial installation of LED apron lighting that replaced the existing high-pressure sodium luminaires at Philadelphia International Airport. Such high-mast applications remain challenging for LED technology, and the lessons learned from this project may help facility managers and LED product manufacturers better meet those challenges.

  17. A high-performance stand-alone solar PV power system for LED lighting

    KAUST Repository

    Huang, B. J.

    2010-06-01

    The present study developed a high-performance solar PV power technology for the LED lighting of a solar home system. The nMPPO (near-Maximum-Power- Point- Operation) design is employed in system design to eliminate MPPT. A feedback control system using pulse width modulation (PWM) technique was developed for battery charging control which can increase the charging capacity by 78%. For high-efficiency lighting, the LED is directly driven by battery using a PWM discharge control to eliminate a DC/DC converter. Two solar-powered LED lighting systems (50W and 100W LED) were built. The long-term outdoor tests have shown that the loss of load probability for full-night lighting requirement is zero for 50W LED and 3.6% for 100W LED. © 2010 IEEE.

  18. Effect of stimulated phase separation on properties of blue, green and monolithic white LEDs

    Energy Technology Data Exchange (ETDEWEB)

    Tsatsulnikov, A.F.; Lundin, W.V.; Sakharov, A.V.; Zavarin, E.E.; Nikolaev, A.E.; Sizov, V.S. [Ioffe Physical-Technical Institute, Russian Academy of Sciences, Politekhnicheskaya Str. 26, 194021 St. Petersburg (Russian Federation); Usov, S.O.; Zakgeim, A.L.; Mizerov, M.N. [Submicron Heterostructures for Microelectronics Research and Engineering Center, Russian Academy of Sciences, Politekhnicheskaya Str. 26, 194021 St. Petersburg (Russian Federation); Cherkashin, N.A.; Hytch, M. [CEMES-CNRS, Universite de Toulouse, Toulouse (France)

    2012-03-15

    Different methods of stimulation of phase separation in an InGaN QWs by technological methods and by design of structure were investigated. Effect of admixing of hydrogen during growth interruptions (GIs) after deposition of the InGaN QWs on their structural and optical properties and properties of InGaN-based LEDs was investigated. Effect of growth pressure on the phase separation was investigated and formation of separate InGaN islands at increase in growth pressure was revealed. It was shown that the phase separation is stimulated in composite InAlN/GaN/InGaN heterostructures and formation of well isolated InGaN islands was observed. Effect of the phase separation on the properties of the blue and deep green LEDs was investigated and strong changes in the spectral position and current dependence of the quantum efficiency were revealed. It was shown that formation of the island due to the phase separation allows control position and width of the emission line and maximum in current dependence of the quantum efficiency. Monolithic white LEDs are containing in active region blue and green InGaN QWs grown with applying of the GIs and emitting in spectral range from 440 nm to 560 nm were studied. Monolithic white LEDs having optimal design of active region demonstrate CCT in the range of 9000-12000 K and maximal external quantum efficiency up to 14 lm/W. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Uniformity of LED light illumination in application to direct imaging lithography

    Science.gov (United States)

    Huang, Ting-Ming; Chang, Shenq-Tsong; Tsay, Ho-Lin; Hsu, Ming-Ying; Chen, Fong-Zhi

    2016-09-01

    Direct imaging has widely applied in lithography for a long time because of its simplicity and easy-maintenance. Although this method has limitation of lithography resolution, it is still adopted in industries. Uniformity of UV irradiance for a designed area is an important requirement. While mercury lamps were used as the light source in the early stage, LEDs have drawn a lot of attention for consideration from several aspects. Although LED has better and better performance, arrays of LEDs are required to obtain desired irradiance because of limitation of brightness for a single LED. Several effects are considered that affect the uniformity of UV irradiance such as alignment of optics, temperature of each LED, performance of each LED due to production uniformity, and pointing of LED module. Effects of these factors are considered to study the uniformity of LED Light Illumination. Numerical analysis is performed by assuming a serious of control factors to have a better understanding of each factor.

  20. White light emission of carbon dots by creating different emissive traps

    International Nuclear Information System (INIS)

    Joseph, Julin; Anappara, Aji A.

    2016-01-01

    Here we report a facile and rapid synthetic strategy for white light emitting carbon dots (CDs) by creating inhomogeneity in the surface-moieties by carbonizing ethylene diamine tetra acetic acid (EDTA) and ethylene glycol (EG) which are having different functional groups. The aqueous solution of the as-synthesised nanoparticles exhibits broad-band emission at several excitation wavelengths, with CIE parameters in the white gamut. Furthermore, white light emission is demonstrated through remote-phosphor technology, by capping 365 nm UV chip with PMMA, after dispersing the polymer with CDs. The resulting emission from the white-LED reported colour parameters such as CIE (0.34, 0.38), CRI of 84 and CCT of 5078 K.

  1. White light emission of carbon dots by creating different emissive traps

    Energy Technology Data Exchange (ETDEWEB)

    Joseph, Julin; Anappara, Aji A., E-mail: aji@nitc.ac.in

    2016-10-15

    Here we report a facile and rapid synthetic strategy for white light emitting carbon dots (CDs) by creating inhomogeneity in the surface-moieties by carbonizing ethylene diamine tetra acetic acid (EDTA) and ethylene glycol (EG) which are having different functional groups. The aqueous solution of the as-synthesised nanoparticles exhibits broad-band emission at several excitation wavelengths, with CIE parameters in the white gamut. Furthermore, white light emission is demonstrated through remote-phosphor technology, by capping 365 nm UV chip with PMMA, after dispersing the polymer with CDs. The resulting emission from the white-LED reported colour parameters such as CIE (0.34, 0.38), CRI of 84 and CCT of 5078 K.

  2. LED; Zum Thema LED

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2010-07-01

    This collection of articles on the subject of light emitting diodes (LED) provides technical information on LED technology, examines latest developments and provides examples of LED use in practice. An 'ABC' of LED technology is presented and fifteen common LED mistakes are noted. The chances and risks of LED use are discussed as is the retrofitting of lighting installations with LEDs. The use of LEDs in street lighting is examined. The journal also includes interviews with architects and a lighting designer. Practical examples of the use of LEDs include the refurbished parliamentary library in Berne, their use in the bird sanctuary headquarters in Sempach, Switzerland, as well as LED use in sales outlets. Also, the use of LED lighting in a spa gazebo in Lucerne is examined.

  3. Comparative Study of Lettuce and Radish Grown Under Red and Blue LEDs and White Fluorescent Lamps

    Science.gov (United States)

    Mickens, Matthew A.; Massa, Gioia; Newsham, Gerard; Wheeler, Raymond; Birmele, Michele

    2016-01-01

    Growing vegetable crops in space will be an essential part of sustaining astronauts during long-range missions. To drive photosynthesis, red and blue light-emitting diodes (LEDs) have attracted attention because of their efficiency, longevity, small size, and safety. In efforts to optimize crop yield, there is also recent interest in analyzing the subtle effects of additional wavelengths on plant growth. For instance, since plants often look purplish gray under red and blue LEDs, the addition of green light allows easy recognition of disease and the assessment of plant health status. However, it is important to know if wavelengths outside the traditional red and blue wavebands have a direct effect on enhancing or hindering the mechanisms involved in plant growth. In this experiment, a comparative study was performed on two short cycle crops of red romaine lettuce (Lactuca sativa cv. "Outredgeous") and radish (Raphanus sativa cv. 'Cherry Bomb'), which were grown under two light treatments. The first treatment being red (630 nm) and blue (450 nm) LEDs alone, while the second treatment consisted of daylight tri-phosphor fluorescent lamps (CCT approximately 5000 K) at equal photosynthetic photon flux (PPF). The treatment effects were evaluated by measuring the fresh biomass produced, plant morphology and leaf dimensions, leaf chlorophyll content, and adenosine triphosphate (ATP) within plant leaf/storage root tissues.

  4. Studies in crystal structure and luminescence properties of Eu3+-doped metal tungstate phosphors for white LEDs

    International Nuclear Information System (INIS)

    Lee, Gwan-Hyoung; Kang, Shinhoo

    2011-01-01

    The correlation between the crystal structure and luminescent properties of Eu 3+ -doped metal tungstate phosphors for white LEDs was investigated. Red-emitting A 4-3x (WO 4 ) 2 :Eu x 3+ (A=Li, Na, K) and B (4-3x)/2 (WO 4 ) 2 :Eu x 3+ (B=Mg, Ca, Sr) phosphors were synthesized by solid-state reactions. The findings confirmed that these phosphors exhibited a strong absorption in the near UV to green range, due to the intra-configurational 4f-4f electron transition of Eu 3+ ions. The high doping concentration of Eu 3+ enhanced the absorption of near UV light and red emission without any detectable concentration quenching. Based on the results of a Rietveld refinement, it was attributed to the unique crystal structure. In the crystal structure of the Eu 3+ -doped metal tungstate phosphor, the critical energy transfer distance is larger than 5 A so that exchange interactions between Eu 3+ ions would occur with difficulty, even at a high doping concentration. The energy transfer between Eu 3+ ions, which causes a decrease in red emission with increasing concentration of Eu 3+ , appears to be due to electric multi-polar interactions. In addition, the Eu-O distance in the host lattice affected the shape of emission spectrum by splitting of emission peak at the 5 D 0 → 7 F 2 transition of Eu 3+ . - Highlights: → Eu 3+ -doped metal tungstate was synthesized as a red phosphor for white LEDs. → Crystal structure is tetragonal with a space group of I4 1 /c. → A strong absorption in the near UV to green range was observed. → High doping of Eu 3+ enhanced the absorption of near UV light and red emission.

  5. Structural Control of InP/ZnS Core/Shell Quantum Dots Enables High-quality White LEDs.

    Science.gov (United States)

    Ganesh Kumar, Baskaran; Sadeghi, Sadra; Melikov, Rustamzhon; Mohammadi Aria, Mohammed; Bahmani Jalali, Houman; Ow-Yang, Cleva; Nizamoglu, Sedat

    2018-05-30

    Herein, we demonstrate that the structural and optical control of InP-based quantum dots can lead to high-performance LEDs. Zinc sulphide (ZnS) shells passivate the InP quantum dot core and increase the quantum yield in green-emitting quantum dots by 13-fold and red-emitting quantum dots by 8-fold. The optimised quantum dots are integrated in the liquid-state to eliminate aggregation induced emission quenching and we fabricated white LEDs with warm, neutral, and cool white appearance by the down-conversion mechanism. The quantum dot-functionalized white LEDs achieve luminous efficiency up to 14.7 lm/W and colour-rendering index up to 80. The structural and optical control of InP/ZnS core/shell quantum dots enable 23-fold enhancement in luminous efficiency of white LEDs compared to ones containing only QDs of InP core. © 2018 IOP Publishing Ltd.

  6. Rare earths (Ce, Eu, Tb) doped Y2Si2O7 phosphors for white LED

    International Nuclear Information System (INIS)

    Sokolnicki, Jerzy

    2013-01-01

    Nanocrystalline yttrium pyrosilicate Y 2 Si 2 O 7 (YPS) singly, doubly or triply doped with Ce 3+ , Eu 3+ , Tb 3+ was obtained by the reaction of nanostructured Y 2 O 3 :Ln 3+ and colloidal SiO 2 at high temperatures. X-ray diffraction analysis confirmed the formation of a single phase of α-YPS at 1200 °C. Two series of YPS samples doped with Eu 3+ or Eu 3+ /Tb 3+ were obtained by applying the reducing atmosphere (75%N 2 +25%H 2 ) at different temperatures. The luminescence and excitation spectra are reported. The singly Eu 3+ doped YPS emit from both Eu 3+ and Eu 2+ ions, with the spectral position and width of the Eu 2+ emission different in both series. The presence of Eu 2+ in the samples was confirmed by electron paramagnetic resonance (EPR) spectra. A broadband emission of Eu 2+ (380–650 nm), combined with the red emission of Eu 3+ is perceived by the naked eye as white light. Co-doping of YPS:Eu 3+ with Tb 3+ results in enhancement of the green component of the emission, and well-balanced white luminescence. The colour of this emission is tunable, and it is possible to get Commission International de I'Eclairage (CIE) chromaticity coordinates of (0.327, 0.327), colour-rendering index (CRI) of 85, and quantum efficiency (QE) of 71%. These phosphors are efficiently excited in the wavelength range of 300–420 nm, which perfectly matches a near UV-emitting InGaN chip. It was shown that for triply (Ce 3+ , Eu 3+ and Tb 3+ ) doped samples the three emissions from the particular activators can be generated using one excitation wavelength. The white light resulting from the superposition of the blue (Ce 3+ ), green (Tb 3+ ) and red (Eu 3+ ) emissions can be obtained by varying the concentration of the active ions and the treating atmosphere, i.e. reducing or oxidising. Eu 2+ was not detected in the triply doped samples, and hence line emissions mostly exhibit CRI values equal to or below 30. - Highlights: ► Nanocrystalline Y 2 Si 2 O 7 was obtained by the

  7. Monolithic Inorganic ZnO/GaN Semiconductors Heterojunction White Light-Emitting Diodes.

    Science.gov (United States)

    Jeong, Seonghoon; Oh, Seung Kyu; Ryou, Jae-Hyun; Ahn, Kwang-Soon; Song, Keun Man; Kim, Hyunsoo

    2018-01-31

    Monolithic light-emitting diodes (LEDs) that can generate white color at the one-chip level without the wavelength conversion through packaged phosphors or chip integration for photon recycling are of particular importance to produce compact, cost-competitive, and smart lighting sources. In this study, monolithic white LEDs were developed based on ZnO/GaN semiconductor heterojunctions. The electroluminescence (EL) wavelength of the ZnO/GaN heterojunction could be tuned by a post-thermal annealing process, causing the generation of an interfacial Ga 2 O 3 layer. Ultraviolet, violet-bluish, and greenish-yellow broad bands were observed from n-ZnO/p-GaN without an interfacial layer, whereas a strong greenish-yellow band emission was the only one observed from that with an interfacial layer. By controlled integration of ZnO/GaN heterojunctions with different postannealing conditions, monolithic white LED was demonstrated with color coordinates in the range (0.3534, 0.3710)-(0.4197, 0.4080) and color temperatures of 4778-3349 K in the Commission Internationale de l'Eclairage 1931 chromaticity diagram. Furthermore, the monolithic white LED produced approximately 2.1 times higher optical output power than a conventional ZnO/GaN heterojunction due to the carrier confinement effect at the Ga 2 O 3 /n-ZnO interface.

  8. MudGet: Reproduction of the desired lighting environment using a smart-LED

    Directory of Open Access Journals (Sweden)

    Yong Hwi Kim

    2017-07-01

    Full Text Available With the emergence of smart LEDs, lighting based interior design is becoming popular. However, most of the smart LED-based lighting systems rely on expert-human intervention to create a desired atmosphere. For convenience, commercial lighting systems offer a number of options but their usability is fairly restricted. Therefore, an intuitive interface is required for novice users to generate the desired lighting environment. In this paper, we have developed a software, named MudGet, which automatically extracts the light mood from a digital image and controls the LED lamps to reproduce a desired lighting effect according to the extracted light mood. In our method, the light mood is regarded as a set of the representative colors of the digital image. The representative colors are extracted by utilizing K-means clustering algorithm. The dimming parameters are set for which each of the LED lamps create the lighting environment with the mood extracted by the software. To evaluate the feasibility of mood reproduction qualitatively, the degree of similarity between the light mood in the digital image and the reproduced result using LEDs is evaluated by a user study under a miniaturized experimental set. We observe that users can easily produce a desired atmosphere through the proposed MudGet software.

  9. A new method to manipulate broiler chicken growth and metabolism: Response to mixed LED light system

    Science.gov (United States)

    Yang, Yefeng; Yu, Yonghua; Pan, Jinming; Ying, Yibin; Zhou, Hong

    2016-05-01

    Present study introduced a new method to manipulate broiler chicken growth and metabolism by mixing the growth-advantage LED. We found that the green/blue LED mixed light system (G-B and G × B) have the similar stimulatory effect on chick body weight with single green light and single blue light (G and B), compared with normal artificial light (P = 0.028). Moreover, the percentage of carcass was significantly greater in the mixed light (G × B) when compared with the single light (P = 0.003). Synchronized with body weight, the mixed light (G-B and G × B) had a significant improved influence on the feed conversion of birds compared with normal light (P = 0.002). A significant improvement in feed conversion were found in mixed light (G × B) compared with single LED light (P = 0.037). G group resulted in a greater high-density lipoprotein cholesterol level than B group (P = 0.002), whereas B group resulted in a greater low-density lipoprotein cholesterol level than G group (P = 0.017). The mixed light significantly increased the birds’ glucose level in comparison with the single light (P = 0.003). This study might establish an effective strategy for maximizing growth of chickens by mixed LED technology.

  10. Monolithically Integrated Light Feedback Control Circuit for Blue/UV LED Smart Package

    NARCIS (Netherlands)

    Koladouz Esfahani, Z.; Tohidian, M.; van Zeijl, H.W.; Kolahdouz, Mohammadreza; Zhang, G.Q.

    2017-01-01

    Given the performance decay of high-power light-emitting diode (LED) chips over time and package condition changes, having a reliable output light for sensitive applications is a point of concern. In this study, a light feedback control circuit, including blue-selective photodiodes, for

  11. Analysis of Shade Matching in Natural Dentitions Using Intraoral Digital Spectrophotometer in LED and Filtered LED Light Sources.

    Science.gov (United States)

    Chitrarsu, Vijai Krishnan; Chidambaranathan, Ahila Singaravel; Balasubramaniam, Muthukumar

    2017-10-31

    To evaluate the shade matching capabilities in natural dentitions using Vita Toothguide 3D-Master and an intraoral digital spectrophotometer (Vita Easyshade Advance 4.0) in various light sources. Participants between 20 and 40 years old with natural, unrestored right maxillary central incisors, no history of bleaching, orthodontic treatment, or malocclusion and no rotations were included. According to their shades, subjects were randomly selected and grouped into A1, A2, and A3. A total of 100 participants (50 male and 50 female) in each group were chosen for this study. Shade selection was made between 10 am and 2 pm for all light sources. The same examiner selected the shade of natural teeth with Vita Toothguide 3D-Master under natural light within 2 minutes. Once the Vita Toothguide 3D-Masterwas matched with the maxillary right central incisor, the L*, a*, and b* values, chroma, and hue were recorded with Vita Easyshade Advance 4.0 by placing it on the shade tab under the same light source. The values were statistically analyzed using one-way ANOVA and Tukey's HSD post hoc test with SPSS v22.0 software. The mean ∆E* ab values for shades A1, A2, and A3 for groups 1, 2, and 3 were statistically significantly different from each other (p spectrophotometer showed statistically significant differences in shade matching compared to Vita Toothguide 3D-Master. Incandescent light showed more accurate shade matching than the filtered LED, LED, and daylight. © 2017 by the American College of Prosthodontists.

  12. LEDs light spectrum effect on the success of fragmentation and growth of the leather coral Sarcophyton spp.

    Directory of Open Access Journals (Sweden)

    João Chambel

    2014-06-01

    Full Text Available The increasing demand for soft corals is reflected on the high attention of the scientific community during the last decades, with several studies focus on production techniques and optimization of coral husbandry (Schlacher et al., 2007;Sella and Benayahu, 2010. However, coral culture success is influenced by the interaction of different factors, such as water movement, temperature, nutrients, heterotrophic feeding and light conditions (Rocha et al., 2013a. Light plays a key role in the growth, reproduction and physiology of scleractinian corals that host phototrophic symbionts and it has been found that the photoresponse of corals is species-specific. Several studies have already focused on the effects of irradiance on coral and its algal symbionts (Osinga et al., 2011. Although, only a few works have investigated the role of the spectral quality of light on coral photobiology, physiology and growth (Rocha et al., 2013b. In the present study, we hypothesize that light spectrum can influence the growth performance of scleractinian corals when exposed at identical intensities of photosynthetically active radiation (PAR. To test our hypothesis we evaluated the effect of contrasting light spectra with an identical PAR of 70 ± 10 μmol quantam−2.s−1emitted by T8 fluorescent lamps (used as a control treatment and three different colours of Light Emitting Diode (LED, white, blue and red. It was evaluated survival and growth rates of Sarcophyton spp., an important scleractinian coral in the marine aquarium trade and for the bioprospecting of marine natural compounds. Replicated coral fragments were obtained from two mother colonies and were exposed to the four types of light spectrum for a period of 30 days. At the end of the experiment period, the results showed 100% of survival in coral fragments, and specific growth rate (SGR of 0,055 ± 0,09 %/day in control group and 0,091 ± 0,019 %/day, 0,210 ± 0,031 %/day and 0,380 ± 0,245 %/day in

  13. White organic light-emitting diodes with fluorescent tube efficiency.

    Science.gov (United States)

    Reineke, Sebastian; Lindner, Frank; Schwartz, Gregor; Seidler, Nico; Walzer, Karsten; Lüssem, Björn; Leo, Karl

    2009-05-14

    The development of white organic light-emitting diodes (OLEDs) holds great promise for the production of highly efficient large-area light sources. High internal quantum efficiencies for the conversion of electrical energy to light have been realized. Nevertheless, the overall device power efficiencies are still considerably below the 60-70 lumens per watt of fluorescent tubes, which is the current benchmark for novel light sources. Although some reports about highly power-efficient white OLEDs exist, details about structure and the measurement conditions of these structures have not been fully disclosed: the highest power efficiency reported in the scientific literature is 44 lm W(-1) (ref. 7). Here we report an improved OLED structure which reaches fluorescent tube efficiency. By combining a carefully chosen emitter layer with high-refractive-index substrates, and using a periodic outcoupling structure, we achieve a device power efficiency of 90 lm W(-1) at 1,000 candelas per square metre. This efficiency has the potential to be raised to 124 lm W(-1) if the light outcoupling can be further improved. Besides approaching internal quantum efficiency values of one, we have also focused on reducing energetic and ohmic losses that occur during electron-photon conversion. We anticipate that our results will be a starting point for further research, leading to white OLEDs having efficiencies beyond 100 lm W(-1). This could make white-light OLEDs, with their soft area light and high colour-rendering qualities, the light sources of choice for the future.

  14. [Hygienic aspects of the use of LED light sources for general illumination in schools].

    Science.gov (United States)

    Kuchma, V R; Sukhareva, L M; Teksheva, L M; Stepanova, M I; Sazaniuk, Z I

    2013-01-01

    For the time present becoming more common semiconductor sources of artificial lighting has become a more and more frequent practice. With the aim to study the impact of LEDs on the health of schoolchildren studies in experimental conditions (specially equipped classrooms) were performed. The comparative analysis of the state of vision, mental health and emotional state of pupils in primary, middle and high schools under fluorescent and LED lighting, meeting to the regulatory requirements, has revealed that the physiological cost of schooling in the use of LED units in classrooms is lower than in a traditional, fluorescent lighting.

  15. Handheld White Light Interferometer for Measuring Defect Depth in Windows

    Science.gov (United States)

    Youngquist, Robert; Simmons, Stephen; Cox, Robert

    2010-01-01

    Accurate quantification of defects (scratches and impacts) is vital to the certification of flight hardware and other critical components. The amount of damage to a particular component contributes to the performance, reliability, and safety of a system, which ultimately affects the success or failure of a mission or test. The launch-commit criteria on a Space Shuttle Orbiter window are governed by the depth of the defects that are identified by a visual inspection. This measurement of a defect is not easy to obtain given the environment, size of the defect, and location of the window(s). The determination of depth has typically been performed by taking a mold impression and measuring the impression with an optical profiling instrument. Another method of obtaining an estimate of the depth is by using a refocus microscope. To use a refocus microscope, the surface of the glass and bottom of the defect are, in turn, brought into focus by the operator. The amount of movement between the two points corresponds to the depth of the defect. The refocus microscope requires a skilled operator and has been proven to be unreliable when used on Orbiter windows. White light interferometry was chosen as a candidate to replace the refocus microscope. The White Light Interferometer (WLI) was developed to replace the refocus microscope as the instrument used for measuring the depth of defects in Orbiter windows. The WLI consists of a broadband illumination source, interferometer, detector, motion control, displacement sensor, mechanical housing, and support electronics. The illumination source for the WLI is typically a visible light emitting diode (LED) or a near-infrared superluminescent diode (SLD) with power levels of less than a milliwatt. The interferometer is a Michelson configuration consisting of a 1-in. (2.5-cm) cube beam splitter, a 0.5-in. (1.3-cm) optical window as a movable leg (used to closely match the return intensity of the fixed leg from the window), and a

  16. Comparative Phenotypical and Molecular Analyses of Arabidopsis Grown under Fluorescent and LED Light

    Directory of Open Access Journals (Sweden)

    Franka Seiler

    2017-06-01

    Full Text Available Comparative analyses of phenotypic and molecular traits of Arabidopsis thaliana grown under standardised conditions is still a challenge using climatic devices supplied with common light sources. These are in most cases fluorescent lights, which have several disadvantages such as heat production at higher light intensities, an invariable spectral output, and relatively rapid “ageing”. This results in non-desired variations of growth conditions and lowers the comparability of data acquired over extended time periods. In this study, we investigated the growth behaviour of Arabidopsis Col0 under different light conditions, applying fluorescent compared to LED lamps, and we conducted physiological as well as gene expression analyses. By changing the spectral composition and/or light intensity of LEDs we can clearly influence the growth behaviour of Arabidopsis and thereby study phenotypic attributes under very specific light conditions that are stable and reproducible, which is not necessarily given for fluorescent lamps. By using LED lights, we can also roughly mimic the sun light emission spectrum, enabling us to study plant growth in a more natural-like light set-up. We observed distinct growth behaviour under the different light regimes which was reflected by physiological properties of the plants. In conclusion, LEDs provide variable emission spectra for studying plant growth under defined, stable light conditions.

  17. Monte Carlo analysis of a control technique for a tunable white lighting system

    DEFF Research Database (Denmark)

    Chakrabarti, Maumita; Thorseth, Anders; Jepsen, Jørgen

    2017-01-01

    A simulated colour control mechanism for a multi-coloured LED lighting system is presented. The system achieves adjustable and stable white light output and allows for system-to-system reproducibility after application of the control mechanism. The control unit works using a pre-calibrated lookup...... table for an experimentally realized system, with a calibrated tristimulus colour sensor. A Monte Carlo simulation is used to examine the system performance concerning the variation of luminous flux and chromaticity of the light output. The inputs to the Monte Carlo simulation, are variations of the LED...... peak wavelength, the LED rated luminous flux bin, the influence of the operating conditions, ambient temperature, driving current, and the spectral response of the colour sensor. The system performance is investigated by evaluating the outputs from the Monte Carlo simulation. The outputs show...

  18. Blue and white light emission from zinc oxide nanoforests

    Directory of Open Access Journals (Sweden)

    Nafisa Noor

    2015-12-01

    Full Text Available Blue and white light emission is observed when high voltage stress is applied using micrometer-separated tungsten probes across a nanoforest formed of ZnO nanorods. The optical spectrum of the emitted light consistently shows three fine peaks with very high amplitude in the 465–485 nm (blue range, corresponding to atomic transitions of zinc. Additional peaks with smaller amplitudes in the 330–650 nm range and broad spectrum white light is observed depending on the excitation conditions. The spatial and spectral distribution of the emitted light, with pink–orange regions identifying percolation paths in some cases and high intensity blue and white light with center to edge variations in others, indicate that multiple mechanisms lead to light emission. Under certain conditions, the tungsten probe tips used to make electrical contact with the ZnO structures melt during the excitation, indicating that the local temperature can exceed 3422 °C, which is the melting temperature of tungsten. The distinct and narrow peaks in the optical spectra and the abrupt increase in current at high electric fields suggest that a plasma is formed by application of the electrical bias, giving rise to light emission via atomic transitions in gaseous zinc and oxygen. The broad spectrum, white light emission is possibly due to the free electron transitions in the plasma and blackbody radiation from molten silicon. The white light may also arise from the recombination through multiple defect levels in ZnO or due to the optical excitation from solid ZnO. The electrical measurements performed at different ambient pressures result in light emission with distinguishable differences in the emission properties and I–V curves, which also indicate that the dielectric breakdown of ZnO, sublimation, and plasma formation processes are the underlying mechanisms.

  19. Electrical aging effect of ZnS based quantum dots for white light-emitting diodes

    Science.gov (United States)

    Kim, Yohan; Ippen, Christian; Greco, Tonino; Jang, Ilwan; Park, Sungkyu; Oh, Min Suk; Han, Chul Jong; Lee, Jeongno; Wedel, Armin; Kim, Jiwan

    2014-03-01

    The present work reports cadmium-free colloidal ZnS:Al quantum dot (QD) based white quantum dot light-emitting diodes (QD-LEDs). The device was fabricated with a structure of ITO/PEDOT:PSS/PVK/QDs/TPBi/LiF/Al using synthesized ZnS:Al QDs which has 393 nm of peak wavelength and sub peaks in visible wavelength. White emission with high color rending index (CRI) was achieved by the combination of blue emission from PVK and ZnS:Al QDs, electroplex emission at the interface between PVK and ZnS:Al QDs, and Al traps/defects emission, which are controlled by electrical aging effect. The characteristic of our device shows the potential for spectrum tunable and Cd-free white QD-LEDs in the near future.

  20. Efficient and stable laser-driven white lighting

    Directory of Open Access Journals (Sweden)

    Kristin A. Denault

    2013-07-01

    Full Text Available Laser-based white lighting offers a viable option as an efficient and color-stable high-power solid-state white light source. We show that white light generation is possible using blue or near-UV laser diodes in combination with yellow-emitting cerium-substituted yttrium aluminum garnet (YAG:Ce or a mixture of red-, green-, and blue-emitting phosphors. A variety of correlated color temperatures (CCT are achieved, ranging from cool white light with a CCT of 4400 K using a blue laser diode to a warm white light with a CCT of 2700 K using a near-UV laser diode, with respective color rendering indices of 57 and 95. The luminous flux of these devices are measured to be 252 lm and 53 lm with luminous efficacies of 76 lm/W and 19 lm/W, respectively. An estimation of the maximum efficacy of a device comprising a blue laser diode in combination with YAG:Ce is calculated and the results are used to optimize the device.

  1. Best practices : bus signage for persons with visual impairments : light-emitting diode (LED) signs

    Science.gov (United States)

    2004-01-01

    This best-practices report provides key information regarding the use of Light-Emitting Diode (LED) sign technologies to present destination and route information on transit vehicles. It will assist managers and engineers in the acquisition and use o...

  2. A comparative study of fluorescent and LED lighting in industrial facilities

    Science.gov (United States)

    Perdahci PhD, C.; Akin BSc, H. C.; Cekic Msc, O.

    2018-05-01

    Industrial facilities have always been in search for reducing outgoings and minimizing energy consumption. Rapid developments in lighting technology require more energy efficient solutions not only for industries but also for many sectors and for households. Addition of solid-state technology has brought LED lamps into play and with LED lamp usage, efficacy level has reached its current values. Lighting systems which uses fluorescent and LED lamps have become the prior choice for many industrial facilities. This paper presents a comparative study about fluorescent and LED based indoor lighting systems for a warehouse building in an industrial facility in terms of lighting distribution values, colour rendering, power consumption, energy efficiency and visual comfort. Both scenarios have been modelled and simulated by using Relux and photometric data for the luminaires have been gathered by conducting tests and measurements in an accredited laboratory.

  3. Efficient light extraction from GaN LEDs using gold-coated ZnO nanoparticles

    KAUST Repository

    Alhadidi, A.

    2015-11-01

    We experimentally demonstrate the effect of depositing gold-coated ZnO nanoparticles on the surface of GaN multi-quantum well LED structures. We show that this method can significantly increase the amount of extracted light.

  4. Design and radiation tests on a LED based emergency evacuation directional lighting

    CERN Document Server

    Trikoupis, Nikolaos

    2017-01-01

    A LED (Light Emitting Diode) based directional lighting system has been designed to indicate the best evacuation direction for applications like the Large Hadron Collider (LHC) tunnel. The design includes constraints for redundancy required by safety systems and for components selection by radiation effects. Most of the literature for radiation effects on LEDs concern digital communications systems, although some recent reports do exist for visible spectrum power LEDs and the reduction in light output versus dose is coherent with the results presented in this paper. Prototype lighting units were irradiated in CERN’s CHARM facility up to a Total Integrated Dose (TID) of 870 Gy and no failures were observed. This paper describes the basic design, presents field tests and the effects of radiation on the LEDs luminance.

  5. Photoluminescence from a Tb-doped photonic crystal microcavity for white light generation

    International Nuclear Information System (INIS)

    Li Yigang; Almeida, Rui M

    2010-01-01

    Terbium-doped one-dimensional triple microcavities have been prepared by sol-gel processing. The photoluminescence (PL) of Tb 3+ ions outside a microcavity structure, when excited by blue laser light at 488 nm, consisted of three distinct peaks at 542, 587 and 619 nm. When embedded in the microcavities, the three Tb 3+ PL peaks were enhanced, balanced and broadened by the photonic crystal structure and combined into a continuous broad band. An analysis in the CIE colour space showed that white light can be obtained by mixing the modified Tb 3+ PL with the blue exciting light, while this is impossible with the original PL profile. This novel technique may improve white light generation by enhancing and modifying the spontaneous emission of current phosphors. It may also lead to the development of new rare-earth phosphor materials based on 4f-4f transitions, able to generate white light more efficiently, via simpler and cheaper alternatives to the current phosphor compositions. A novel configuration to combine this kind of structure with a white light-emitting-diode (LED) is also proposed.

  6. Fluorescent SiC for white light-emitting diodes

    DEFF Research Database (Denmark)

    Ou, Haiyan; Ou, Yiyu; Kamiyama, S.

    2012-01-01

    The strong photoluminescence from f-SiC was achieved after the optimization of the B and N concentrations. Surface nanostructures were successfully applied to enhance the extraction efficiency. f-SiC is a promising wavelength convertor for white LEDs....

  7. Temperature dependence of Ce:YAG single-crystal phosphors for high-brightness white LEDs/LDs

    Science.gov (United States)

    Arjoca, Stelian; Víllora, Encarnación G.; Inomata, Daisuke; Aoki, Kazuo; Sugahara, Yoshiyuki; Shimamura, Kiyoshi

    2015-05-01

    The growth of Ce:Y3Al5O12(Ce:YAG) single-crystal phosphors (SCPs) by the Czochralski technique is analyzed in terms of segregation coefficient, solubility and absorption cross-section. The emission characteristics of these SCPs are investigated in a wide temperature range, from liquid He temperature up to 500 °C. The internal quantum efficiency of SCPs achieves its maximum at about 250 °C. Thermal quenching of SCPs at high temperature is attributed to the Mott-Seitz mechanism. In the case of ceramic powder phosphors, a continuous droop is observed with the temperature due to defect-related non-radiative recombination paths. It is shown that (Ce:YAG SCPs + blue LEDs/LDs) can cover a wide range of color temperatures 5500-7000 K, with color rendering indices around 70. In conclusion, it is shown that Ce:YAG SCPs are the most efficient and temperature stable converters to fabricate high-brightness white light sources with high-power blue LEDs and LDs.

  8. Setup of a LED light-pulser system for the OLYMPUS experiment; Aufbau eines LED-Lichtpulsersystems fuer das OLYMPUS-Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Rehman, Waqaas

    2011-12-15

    The aim of this thesis consists in the construction and test of an external light-calibration system based on light-emitting diodes (LED) for the application at the symmetric Moller/Bhabha (SYMB) luminosity monitor. In chapter 2 the theoretical foundations of the OLYMPUS experiment, especially of the SYMB luminosity monitor are explained. Thereafter in chapter 3 the details of the setup of the OLYMPUS experiment and the fundamental properties of the SYMB detectors are discussed. In chapter 4 the whole concept of the LED light-pulser system is treated. In chapter 5 then test measurements with the ready LED light-pulser system are described. Thereby the light source shall be optimized in the shape that thereafter light pulses with short signal width are producable. Also different measurements for the unique characterization of the systems are performed. In chapter 6 light-intensity measurements during the operation of the LED light-pulser system are described.

  9. Direct battery-driven solar LED lighting using constant-power control

    KAUST Repository

    Huang, Bin-Juine; Chen, Chun-Wei; Hsu, Po-Chien; Tseng, Wei-Min; Wu, Min-Sheng

    2012-01-01

    A direct battery-driven LED lighting technique using constant-power control is proposed in the present study. A system dynamics model of LED luminaire was derived and used in the design of the feedback constant-power control system. The test result

  10. The sunstone – an intelligent platform for pv led lighting in the urban environment

    DEFF Research Database (Denmark)

    Poulsen, Peter Behrensdorff; Dam-Hansen, Carsten; Harboe, Rene Kirstein

    and maintenance. Such markets are interesting for solar energy powered LED applications since the additional price due to the PV and LEDs are hugely offset by the savings of avoiding digging up and repaving the road when laying a cable to the grid and avoid the investment and man-power cost of replacing light...

  11. Illumination sensing in LED lighting systems based on frequency-division multiplexing

    NARCIS (Netherlands)

    Yang, Hongming; Bergmans, J.W.M.; Schenk, T.C.W.

    2009-01-01

    Recently, light emitting diode (LED) based illumination systems have attracted considerable research interest. Such systems normally consist of a large number of LEDs. In order to facilitate the control of such high-complexity system, a novel signal processing application, namely illumination

  12. Dim-light photoreceptor of chub mackerel Scomber japonicus and the photoresponse upon illumination with LEDs of different wavelengths.

    Science.gov (United States)

    Jang, Jun-Chul; Choi, Mi-Jin; Yang, Yong-Soo; Lee, Hyung-Been; Yu, Young-Moon; Kim, Jong-Myoung

    2016-06-01

    To study the absorption characteristics of rhodopsin, a dim-light photoreceptor, in chub mackerel (Scomber japonicus) and the relationship between light wavelengths on the photoresponse, the rod opsin gene was cloned into an expression vector, pMT4. Recombinant opsin was transiently expressed in COS-1 cells and reconstituted with 11-cis-retinal. Cells containing the regenerated rhodopsin were solubilized and subjected to UV/Vis spectroscopic analysis in the dark and upon illumination. Difference spectra from the lysates indicated an absorption maximum of mackerel rhodopsin around 500 nm. Four types of light-emitting diode (LED) modules with different wavelengths (red, peak 627 nm; cyan, 505 nm; blue, 442 nm; white, 447 + 560 nm) were constructed to examine their effects on the photoresponse in chub mackerel. Behavioral responses of the mackerels, including speed and frequencies acclimated in the dark and upon LED illumination, were analyzed using an underwater acoustic camera. Compared to an average speed of 22.25 ± 1.57 cm/s of mackerel movement in the dark, speed increased to 22.97 ± 0.29, 24.66 ± 1.06, 26.28 ± 2.28, and 25.19 ± 1.91 cm/s upon exposure to red, blue, cyan, and white LEDs, respectively. There were increases of 103.48 ± 1.58, 109.37 ± 5.29, 118.48 ± 10.82, and 109.43 ± 3.92 %, respectively, in the relative speed of the fishes upon illumination with red, blue, cyan, and white LEDs compared with that in the dark (set at 100 %). Similar rate of wavelength-dependent responses was observed in a frequency analysis. These results indicate that an LED emitting a peak wavelength close to an absorption maximum of rhodopsin is more effective at eliciting a response to light.

  13. Hybrid sunlight/LED illumination and renewable solar energy saving concepts for indoor lighting.

    Science.gov (United States)

    Tsuei, Chih-Hsuan; Sun, Wen-Shing; Kuo, Chien-Cheng

    2010-11-08

    A hybrid method for using sunlight and light-emitting diode (LED) illumination powered by renewable solar energy for indoor lighting is simulated and presented in this study. We can illuminate an indoor space and collect the solar energy using an optical switching system. When the system is turned off, the full spectrum of the sunlight is concentrated by a concentrator, to be absorbed by solar photovoltaic devices that provide the electricity to power the LEDs. When the system is turned on, the sunlight collected by the concentrator is split into visible and non-visible rays by a beam splitter. The visible rays pass through the light guide into a light box where it is mixed with LED light to ultimately provide uniform illumination by a diffuser. The non-visible rays are absorbed by the solar photovoltaic devices to provide electrical power for the LEDs. Simulation results show that the efficiency of the hybrid sunlight/LED illumination with the renewable solar energy saving design is better than that of LED and traditional lighting systems.

  14. VLC-based indoor location awareness using LED light and image sensors

    Science.gov (United States)

    Lee, Seok-Ju; Yoo, Jong-Ho; Jung, Sung-Yoon

    2012-11-01

    Recently, indoor LED lighting can be considered for constructing green infra with energy saving and additionally providing LED-IT convergence services such as visible light communication (VLC) based location awareness and navigation services. For example, in case of large complex shopping mall, location awareness to navigate the destination is very important issue. However, the conventional navigation using GPS is not working indoors. Alternative location service based on WLAN has a problem that the position accuracy is low. For example, it is difficult to estimate the height exactly. If the position error of the height is greater than the height between floors, it may cause big problem. Therefore, conventional navigation is inappropriate for indoor navigation. Alternative possible solution for indoor navigation is VLC based location awareness scheme. Because indoor LED infra will be definitely equipped for providing lighting functionality, indoor LED lighting has a possibility to provide relatively high accuracy of position estimation combined with VLC technology. In this paper, we provide a new VLC based positioning system using visible LED lights and image sensors. Our system uses location of image sensor lens and location of reception plane. By using more than two image sensor, we can determine transmitter position less than 1m position error. Through simulation, we verify the validity of the proposed VLC based new positioning system using visible LED light and image sensors.

  15. High luminous flux from single crystal phosphor-converted laser-based white lighting system

    KAUST Repository

    Cantore, Michael

    2015-12-14

    The efficiency droop of light emitting diodes (LEDs) with increasing current density limits the amount of light emitted per wafer area. Since low current densities are required for high efficiency operation, many LED die are needed for high power white light illumination systems. In contrast, the carrier density of laser diodes (LDs) clamps at threshold, so the efficiency of LDs does not droop above threshold and high efficiencies can be achieved at very high current densities. The use of a high power blue GaN-based LD coupled with a single crystal Ce-doped yttrium aluminum garnet (YAG:Ce) sample was investigated for white light illumination applications. Under CW operation, a single phosphor-converted LD (pc-LD) die produced a peak luminous efficacy of 86.7 lm/W at 1.4 A and 4.24 V and a peak luminous flux of 1100 lm at 3.0 A and 4.85 V with a luminous efficacy of 75.6 lm/W. Simulations of a pc-LD confirm that the single crystal YAG:Ce sample did not experience thermal quenching at peak LD operating efficiency. These results show that a single pc-LD die is capable of emitting enough luminous flux for use in a high power white light illumination system.

  16. Tunable and white light emitting AlPO4 mesoporous glass by design of inorganic/organic luminescent species

    Directory of Open Access Journals (Sweden)

    Jin He

    2015-04-01

    Full Text Available The realization of tunable and white light emitting sources employed by UV-LED with single-host phosphors has been an exciting development in the search for high luminous efficiency and excellent color rendering index white-light source. A tunable and white light emitting mesoporous glass was prepared by utilizing both inorganic/organic (Europium/coumarin luminescent species in the meso-structure. The tunable and white light emission was deliberately designed by CIE calculation based on the individual emission spectra, which was realized by tailoring the emission of Eu2+/Eu3+ ions and coumarin 535 in sol-gel AlPO4 mesoporous glass. This simple and versatile procedure is not limited in the combination of rare earth and organic dye and is therefore extendable to other luminescent species in meso-structure for color-tunable efficient solid-state lighting sources.

  17. Optimal nitrogen and phosphorus codoping carbon dots towards white light-emitting device

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Feng; Wang, Yaling; Miao, Yanqin; Yang, Yongzhen, E-mail: yyztyut@126.com, E-mail: liuxuguang@tyut.edu.cn [Key Laboratory of Interface Science and Engineering in Advanced Materials, Taiyuan University of Technology, Ministry of Education, Taiyuan 030024 (China); Research Center on Advanced Materials Science and Technology, Taiyuan University of Technology, Taiyuan 030024 (China); He, Yuheng; Liu, Xuguang, E-mail: yyztyut@126.com, E-mail: liuxuguang@tyut.edu.cn [Key Laboratory of Interface Science and Engineering in Advanced Materials, Taiyuan University of Technology, Ministry of Education, Taiyuan 030024 (China); College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan 030024 (China)

    2016-08-22

    Through a one-step fast microwave-assisted approach, nitrogen and phosphorus co-doped carbon dots (N,P-CDs) were synthesized using ammonium citrate (AC) as a carbon source and phosphates as additive reagent. Under the condition of an optimal reaction time of 140 s, the influence of additive with different N and P content on fluorescent performance of N,P-CDs was further explored. It was concluded that high nitrogen content and moderate phosphorus content are necessary for obtaining high quantum yield (QY) N,P-CDs, among which the TAP-CDs (CDs synthesized using ammonium phosphate as additive reagent) show high quantum yield (QY) of 62% and red-green-blue (RGB) spectral composition of 51.67%. Besides, the TAP-CDs exhibit satisfying thermal stability within 180 °C. By virtue of good optical and thermal properties of TAP-CDs, a white light-emitting device (LED) was fabricated by combining ultraviolet chip with TAP-CDs as phosphor. The white LED emits bright warm-white light with the CIE chromaticity coordinate of (0.38, 0.35) and the corresponding color temperature (CCT) of 4450 K, indicating the potential of TAP-CDs phosphor in white LED.

  18. Cationic surfactant assisted ultrasound synthesis of Dy3+ doped CdSiO3 nanostructures for white LED application

    Science.gov (United States)

    Basavaraj, R. B.; Nagabhushana, H.; Lingaraju, K.; Prasad, B. Daruka

    2017-05-01

    In this paper we report for the first time Dy3+ (1-7 mol %) doped CdSiO3 nanophosphors prepared via facile ultrasound supported sonochemical route using EGCG (epigallocatechin gallate). The final product was well characterized by PXRD, FTIR, SEM, TEM and PL. The powder X-ray diffraction (PXRD) profiles showed monoclinic phase with highly crystalline nature. The sonication time, concentration of the surfactant play vital role in tuning the morphology. The crystallite size was calculated from PXRD patterns as well as by TEM image and it was found to 20-30 nm. The Fourier transform infrared spectroscopy (FTIR) results confirmed the presence of Si-O-Si and Si-O stretching vibrations in CdSiO3. Photoluminescence properties of Dy3+ (1-7 mol %) doped CdSiO3 excited under near ultra violet wavelength (350 nm) was studied in order to investigate the possibility of its use in white light emitting diode applications. The emission spectra consists of intra 4f transitions of Dy3+, namely 4F9/2 → 6H15/2 (480 nm), and 4F9/2 → 6H13/2 (574 nm) respectively. The 3 mol% Dy3+ doped phosphor showed maximum intensity. The Commission Internationale de I'Eclairage (CIE) and correlated color temperature (CCT) was evaluated. Further, the quantum efficiency and color purity results of the product showed high efficiency and it was highly useful in white light emitting diodes (wLEDs) applications.

  19. White light emission from exciplex using tris-(8-hydroxyquinoline)aluminum as chromaticity-tuning layer

    International Nuclear Information System (INIS)

    Feng, Jing; Li, Feng; Gao, Wenbao; Liu, Shiyong; Liu, Yu; Wang, Yue

    2001-01-01

    We demonstrate efficient organic white light-emitting devices (LEDs), using N,N prime-diphenyl-N,N prime-bis(1-naphthyl) - (1,1 prime-biphenyl)-4,4 prime-diamine (NPB) as the hole-transporting layer, 1,6-bis(2-hydroxyphenyl)pyridine boron complex [(dppy)BF] as the emitting layer, tris-(8-hydroxyquinoline)aluminum (Alq) as the electron-transporting and chromaticity-tuning layer. The white light comes from exciplex emission at the solid-state interface between (dppy)BF and NPB in addition to the exciton emission from NPB and (dppy)BF, respectively. The chromaticity of white emission can be tuned by adjusting the thickness of the Alq layer. The white LEDs with an Alq thickness of 15 nm exhibit a maximum luminescence of 2000 cd/m2 and efficiency of 0.58 lm/W, and the Commission Internationale De l'Eclairage coordinates of resulting emission vary from (0.29,0.33) to (0.31,0.35) with increasing forward bias from 10 to 25 V. The region is very close to the equienergy white point (0.33,0.33). [copyright] 2001 American Institute of Physics

  20. White-Light Emission from Layered Halide Perovskites.

    Science.gov (United States)

    Smith, Matthew D; Karunadasa, Hemamala I

    2018-03-20

    With nearly 20% of global electricity consumed by lighting, more efficient illumination sources can enable massive energy savings. However, effectively creating the high-quality white light required for indoor illumination remains a challenge. To accurately represent color, the illumination source must provide photons with all the energies visible to our eye. Such a broad emission is difficult to achieve from a single material. In commercial white-light sources, one or more light-emitting diodes, coated by one or more phosphors, yield a combined emission that appears white. However, combining emitters leads to changes in the emission color over time due to the unequal degradation rates of the emitters and efficiency losses due to overlapping absorption and emission energies of the different components. A single material that emits broadband white light (a continuous emission spanning 400-700 nm) would obviate these problems. In 2014, we described broadband white-light emission upon near-UV excitation from three new layered perovskites. To date, nine white-light-emitting perovskites have been reported by us and others, making this a burgeoning field of study. This Account outlines our work on understanding how a bulk material, with no obvious emissive sites, can emit every color of the visible spectrum. Although the initial discoveries were fortuitous, our understanding of the emission mechanism and identification of structural parameters that correlate with the broad emission have now positioned us to design white-light emitters. Layered hybrid halide perovskites feature anionic layers of corner-sharing metal-halide octahedra partitioned by organic cations. The narrow, room-temperature photoluminescence of lead-halide perovskites has been studied for several decades, and attributed to the radiative recombination of free excitons (excited electron-hole pairs). We proposed that the broad white emission we observed primarily stems from exciton self-trapping. Here, the

  1. Investing in Their Future: Portland’s Purchase and Conversion of an LED Street Lighting System

    Energy Technology Data Exchange (ETDEWEB)

    Kinzey, B. R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Rosinbum, T. [Portland Bureau of Transportation, Portland, OR (United States)

    2015-08-28

    During the ongoing process of converting its streetlights from high-pressure sodium to LED, the city of Portland, Oregon, purchased a large portion of its street lighting system and encountered a range of issues among the stakeholders. This report identifies some of the challenges involved and discusses how they were addressed, in order to help inform and facilitate future lighting transitions elsewhere.

  2. User evaluation of eight led light sources with different special colour rendering indices R9

    DEFF Research Database (Denmark)

    Markvart, Jakob; Iversen, Anne; Logadottir, Asta

    2013-01-01

    In this study we evaluated the influence of the special colour rendering index R9 on subjective red colour perception and Caucasian skin appearance among untrained test subjects. The light sources tested are commercially available LED based light sources with similar correlated colour temperature...

  3. Optimization of Multiband White-Light Illuminants for Specified Color Temperatures

    Directory of Open Access Journals (Sweden)

    Snjezana Soltic

    2015-01-01

    Full Text Available This paper describes an effective approach for the optimization of multiband spectra to produce prospective white-light spectra having specific color temperatures. The optimization process employs a genetic algorithm known as differential evolution, which aims to minimize the color rendering differences between a prospective white-light spectrum and its corresponding reference illuminant. Color rendering is assessed by calculating the CIEDE2000 color difference (ΔE00 for 14 CIE test colors under the two sources. Optimized white-light spectra were matched to three CIE standard illuminants, that is, A (2856 K, D50 (5003 K, and D65 (6504 K. Optimal solutions for three- and four-band 25 and 50 nm Gaussian spectra are presented and analyzed, together with mixed 4-LED spectra that were optimized in the same way. In all cases, the simulated sources were shown to provide color rendering of such quality that ΔE00av ≤ 2.24 units. Such white-light sources would likely find wide acceptance in numerous lighting applications.

  4. Investigation of structure in the modular light pipe component for LED automotive lamp

    Science.gov (United States)

    Chen, Hsi-Chao; Zhou, Yang; Huang, Chien-Sheng; Jhong, Wan-Ling; Cheng, Bo-Wei; Jhang, Jhe-Ming

    2014-09-01

    Light-Emitting Diodes (LEDs) have the advantages of small length, long lifetime, fast response time (μs), low voltage, good mechanical properties and environmental protection. Furthermore, LEDs could replace the halogen lamps to avoid the mercury pollution and economize the use of energy. Therefore, the LEDs could instead of the traditional lamp in the future and became an important light source. The proposal of this study was to investigate the effects of the structure and length of the reflector component for a LED automotive lamp. The novel LED automotive lamp was assembled by several different modularization columnar. The optimized design of the different structure and the length to the reflector was simulated by software TracePro. The design result must met the vehicle regulation of United Nations Economic Commission for Europe (UNECE) such as ECE-R19 etc. The structure of the light pipe could be designed by two steps structure. Then constitute the proper structure and choose different power LED to meet the luminous intensity of the vehicle regulation. The simulation result shows the proper structure and length has the best total luminous flux and a high luminous efficiency for the system. Also, the stray light could meet the vehicle regulation of ECE R19. Finally, the experimental result of the selected structure and length of the light pipe could match the simulation result above 80%.

  5. Solid State pH Sensor Based on Light Emitting Diodes (LED) As Detector Platform

    OpenAIRE

    Lau, King Tong; Shepherd, R.; Diamond, Danny; Diamond, Dermot

    2006-01-01

    A low-power, high sensitivity, very low-cost light emitting diode (LED)-based device developed for low-cost sensor networks was modified with bromocresol green membrane to work as a solid-state pH sensor. In this approach, a reverse-biased LED functioning as a photodiode is coupled with a second LED configured in conventional emission mode. A simple timer circuit measures how long (in microsecond) it takes for the photocurrent generated on the detector LED to discharge its capacitance from lo...

  6. Lighting and social practices - what role does lighting play for low energy house (LEH) households and LED frontrunners?

    DEFF Research Database (Denmark)

    Jensen, Charlotte Louise

    As lighting in Danish households consume approximately 1.3 TWh every year, reducing electricity consumption from lighting is important. Studies have shown that a mere substitution of inefficient lighting technologies towards more efficient ones may not be possible, as many social and cultural...... dimensions influence how people use and relate to lighting. Assessing how very distinctive contexts of households (that diverge from an exemplary kind of household), such as low energy houses and LED frontrunner households, use and understand lighting, may give some insight into what may trigger or hamper...

  7. Improvement of illumination uniformity for LED flat panel light by using micro-secondary lens array.

    Science.gov (United States)

    Lee, Hsiao-Wen; Lin, Bor-Shyh

    2012-11-05

    LED flat panel light is an innovative lighting product in recent years. However, current flat panel light products still contain some drawbacks, such as narrow lighting areas and hot spots. In this study, a micro-secondary lens array technique was proposed and applied for the design of the light guide surface to improve the illumination uniformity. By using the micro-secondary lens array, the candela distribution of the LED flat panel light can be adjusted to similar to batwing distribution to improve the illumination uniformity. The experimental results show that the enhancement of the floor illumination uniformity is about 61%, and that of the wall illumination uniformity is about 20.5%.

  8. LED surgical lighting system with multiple free-form surfaces for highly sterile operating theater application.

    Science.gov (United States)

    Liu, Peng; Zhang, Yaqin; Zheng, Zhenrong; Li, Haifeng; Liu, Xu

    2014-06-01

    Although the ventilation system is widely employed in the operating theater, a strictly sterile surgical environment still cannot be ensured because of laminar disturbance, which is mainly caused by the surgical lighting system. Abandoning traditional products, we propose an LED surgical lighting system, which can alleviate the laminar disturbance and provide an appropriate lighting condition for surgery. It contains a certain amount of LED lens units, which are embedded in the ceiling and arranged around the air supply smallpox. The LED lens unit integrated with an LED light source and a free-form lens is required to produce a uniform circular illumination with a large tolerance to the change of lighting distance. To achieve such a dedicated lens, two free-form refractive surfaces, which are converted into two ordinary differential equations by the design method presented in this paper, are used to deflect the rays. The results show that the LED surgical lighting system can provide an excellent illumination environment for surgery, and, apparently, the laminar disturbance also can be relieved.

  9. Study of LED modulation effect on the photometric quantities and beam homogeneity of automotive lighting

    Science.gov (United States)

    Koudelka, Petr; Hanulak, Patrik; Jaros, Jakub; Papes, Martin; Latal, Jan; Siska, Petr; Vasinek, Vladimir

    2015-07-01

    This paper discusses the implementation of a light emitting diode based visible light communication system for optical vehicle-to-vehicle (V2V) communications in road safety applications. The widespread use of LEDs as light sources has reached into automotive fields. For example, LEDs are used for taillights, daytime running lights, brake lights, headlights, and traffic signals. Future in the optical vehicle-to-vehicle (V2V) communications will be based on an optical wireless communication technology that using LED transmitter and a camera receiver (OCI; optical communication image sensor). Utilization of optical V2V communication systems in automotive industry naturally brings a lot of problems. Among them belongs necessity of circuit implementation into the current concepts of electronic LED lights control that allows LED modulation. These circuits are quite complicated especially in case of luxury cars. Other problem is correct design of modulation circuits so that final vehicle lightning using optical vehicle-to-vehicle (V2V) communication meets standard requirements on Photometric Quantities and Beam Homogeneity. Authors of this article performed research on optical vehicle-to-vehicle (V2V) communication possibilities of headlight (Jaguar) and taillight (Skoda) in terms of modulation circuits (M-PSK, M-QAM) implementation into the lamp concepts and final fulfilment of mandatory standards on Photometric Quantities and Beam Homogeneity.

  10. Efficient conceptual design for LED-based pixel light vehicle headlamps

    Science.gov (United States)

    Held, Marcel Philipp; Lachmayer, Roland

    2017-12-01

    High-resolution vehicle headlamps represent a future-oriented technology that can be used to increase traffic safety and driving comfort. As a further development to the current Matrix Beam headlamps, LED-based pixel light systems enable ideal lighting functions (e.g. projection of navigation information onto the road) to be activated in any given driving scenario. Moreover, compared to other light-modulating elements such as DMDs and LCDs, instantaneous LED on-off toggling provides a decisive advantage in efficiency. To generate highly individualized light distributions for automotive applications, a number of approaches using an LED array may be pursued. One approach is to vary the LED density in the array so as to output the desired light distribution. Another notable approach makes use of an equidistant arrangement of the individual LEDs together with distortion optics to formulate the desired light distribution. The optical system adjusts the light distribution in a manner that improves resolution and increases luminous intensity of the desired area. An efficient setup for pixel generation calls for one lens per LED. Taking into consideration the limited space requirements of the system, this implies that the luminous flux, efficiency and resolution image parameters are primarily controlled by the lens dimensions. In this paper a concept for an equidistant LED array arrangement utilizing distortion optics is presented. The paper is divided into two parts. The first part discusses the influence of lens geometry on the system efficiency whereas the second part investigates the correlation between resolution and luminous flux based on the lens dimensions.

  11. Application of 265-nm UVC LED Lighting to Sterilization of Typical Gram Negative and Positive Bacteria

    Science.gov (United States)

    Lee, Yong Wook; Yoon, Hyung Do; Park, Jae-Hyoun; Ryu, Uh-Chan

    2018-05-01

    UV LED lightings have been displacing conventional UV lamps due to their high efficiency, long lifetime, etc. A sterilizing lighting was prepared by assembling a UV LED module composed of 265-nm UVC LEDs and a silica lens array with a driver module comprised of a driver IC controlling pulse width modulation and constant current. The silica lens array was designed and fabricated to focus UV beam and simultaneously to give a uniform light distribution over specimens. Then pasteurizing effect of the lighting was analyzed for four kinds of bacteria and one yeast which are dangerous to people with low immunity. Sterilizing tests on these germs were carried out at the both exposure distances of 10 and 100 mm for various exposure durations up to 600 s.

  12. Improved predictive modeling of white LEDs with accurate luminescence simulation and practical inputs with TracePro opto-mechanical design software

    Science.gov (United States)

    Tsao, Chao-hsi; Freniere, Edward R.; Smith, Linda

    2009-02-01

    The use of white LEDs for solid-state lighting to address applications in the automotive, architectural and general illumination markets is just emerging. LEDs promise greater energy efficiency and lower maintenance costs. However, there is a significant amount of design and cost optimization to be done while companies continue to improve semiconductor manufacturing processes and begin to apply more efficient and better color rendering luminescent materials such as phosphor and quantum dot nanomaterials. In the last decade, accurate and predictive opto-mechanical software modeling has enabled adherence to performance, consistency, cost, and aesthetic criteria without the cost and time associated with iterative hardware prototyping. More sophisticated models that include simulation of optical phenomenon, such as luminescence, promise to yield designs that are more predictive - giving design engineers and materials scientists more control over the design process to quickly reach optimum performance, manufacturability, and cost criteria. A design case study is presented where first, a phosphor formulation and excitation source are optimized for a white light. The phosphor formulation, the excitation source and other LED components are optically and mechanically modeled and ray traced. Finally, its performance is analyzed. A blue LED source is characterized by its relative spectral power distribution and angular intensity distribution. YAG:Ce phosphor is characterized by relative absorption, excitation and emission spectra, quantum efficiency and bulk absorption coefficient. Bulk scatter properties are characterized by wavelength dependent scatter coefficients, anisotropy and bulk absorption coefficient.

  13. LEDWIRE: A Versatile Networking Platform for Smart LED Lighting Applications Using LIN-Bus and WSNs

    Directory of Open Access Journals (Sweden)

    Dimitrios D. Piromalis

    2016-05-01

    Full Text Available In this paper, the architecture of a versatile networking and control platform for Light-Emitting Diode (LED lighting applications is presented, based on embedded wireless and wired networking technologies. All the possible power and control signals distribution topologies of the lighting fixtures are examined with particular focus on dynamic lighting applications with design metrics as the cost, the required wiring installation expenses and maintenance complexity. The proposed platform is optimized for applications where the grouping of LED-based lighting fictures clusters is essential, as well as their synchronization. With such an approach, the distributed control and synchronization of LED lighting fixtures' clusters is performed through a versatile network that uses the single wire Local Interconnect Network (LIN bus. The proposed networking platform is presented in terms of its physical layer architecture, its data protocol configuration, and its functionality for smart control. As a proof of concept, the design of a LED lighting fixture together with a LIN-to-IEEE802.15.4/ZigBee data gateway is presented.

  14. Modeling the effects of phosphor converted LED lighting to the night sky of the Haleakala Observatory, Hawaii

    Science.gov (United States)

    Aubé, M.; Simoneau, A.; Wainscoat, R.; Nelson, L.

    2018-05-01

    The goal of this study is to evaluate the current level of light pollution in the night sky at the Haleakala Observatory on the island of Maui in Hawaii. This is accomplished with a numerical model that was tested in the first International Dark Sky Reserve located in Mont-Mégantic National Park in Canada. The model uses ground data on the artificial light sources present in the region of study, geographical data, and remotely sensed data for: 1) the nightly upward radiance; 2) the terrain elevation; and, 3) the ground spectral reflectance of the region. The results of the model give a measure of the current state of the sky spectral radiance at the Haleakala Observatory. Then, using the current state as a reference point, multiple light conversion plans are elaborated and evaluated using the model. We can thus estimate the expected impact of each conversion plan on the night sky radiance spectrum. A complete conversion to white (LEDs) with (CCT) of 4000K and 3000K are contrasted with a conversion using (PC) amber (LEDs). We include recommendations concerning the street lamps to be used in sensitive areas like the cities of Kahului and Kihei and suggest best lighting practices related to the color of lamps used at night.

  15. Warm White Light-Emitting Diodes Based on a Novel Orange Cationic Iridium(III) Complex.

    Science.gov (United States)

    Tang, Huaijun; Meng, Guoyun; Chen, Zeyu; Wang, Kaimin; Zhou, Qiang; Wang, Zhengliang

    2017-06-16

    A novel orange cationic iridium(III) complex [(TPTA)₂Ir(dPPOA)]PF₆ (TPTA: 3,4,5-triphenyl-4 H -1,2,4-triazole, dPPOA: N,N-diphenyl-4-(5-(pyridin-2-yl)-1,3,4-oxadiazol-2-yl)aniline) was synthesized and used as a phosphor in light-emitting diodes (LEDs). [(TPTA)₂Ir(dPPOA)]PF₆ has high thermal stability with a decomposition temperature ( T d ) of 375 °C, and its relative emission intensity at 100 °C is 88.8% of that at 25°C. When only [(TPTA)₂Ir(dPPOA)]PF₆ was used as a phosphor at 6.0 wt % in silicone and excited by a blue GaN (GaN: gallium nitride) chip (450 nm), an orange LED was obtained. A white LED fabricated by a blue GaN chip (450 nm) and only yellow phosphor Y₃Al₅O 12 :Ce 3+ (YAG:Ce) (1.0 wt % in silicone) emitted cold white light, its CIE (CIE: Commission International de I'Eclairage ) value was (0.32, 0.33), color rendering index (CRI) was 72.2, correlated color temperature (CCT) was 6877 K, and luminous efficiency ( η L ) was 128.5 lm∙W -1 . Such a cold white LED became a neutral white LED when [(TPTA)₂Ir(dPPOA)]PF₆ was added at 0.5 wt %; its corresponding CIE value was (0.35, 0.33), CRI was 78.4, CCT was 4896 K, and η L was 85.2 lm∙W -1 . It further became a warm white LED when [(TPTA)₂Ir(dPPOA)]PF₆ was added at 1.0 wt %; its corresponding CIE value was (0.39, 0.36), CRI was 80.2, CCT was 3473 K, and η L was 46.1 lm∙W -1 . The results show that [(TPTA)₂Ir(dPPOA)]PF₆ is a promising phosphor candidate for fabricating warm white LEDs.

  16. GaN-on-Si blue/white LEDs: epitaxy, chip, and package

    Science.gov (United States)

    Qian, Sun; Wei, Yan; Meixin, Feng; Zengcheng, Li; Bo, Feng; Hanmin, Zhao; Hui, Yang

    2016-04-01

    The dream of epitaxially integrating III-nitride semiconductors on large diameter silicon is being fulfilled through the joint R&D efforts of academia and industry, which is driven by the great potential of GaN-on-silicon technology in improving the efficiency yet at a much reduced manufacturing cost for solid state lighting and power electronics. It is very challenging to grow high quality GaN on Si substrates because of the huge mismatch in the coefficient of thermal expansion (CTE) and the large mismatch in lattice constant between GaN and silicon, often causing a micro-crack network and a high density of threading dislocations (TDs) in the GaN film. Al-composition graded AlGaN/AlN buffer layers have been utilized to not only build up a compressive strain during the high temperature growth for compensating the tensile stress generated during the cool down, but also filter out the TDs to achieve crack-free high-quality n-GaN film on Si substrates, with an X-ray rocking curve linewidth below 300 arcsec for both (0002) and (101¯2) diffractions. Upon the GaN-on-Si templates, prior to the deposition of p-AlGaN and p-GaN layers, high quality InGaN/GaN multiple quantum wells (MQWs) are overgrown with well-engineered V-defects intentionally incorporated to shield the TDs as non-radiative recombination centers and to enhance the hole injection into the MQWs through the via-like structures. The as-grown GaN-on-Si LED wafers are processed into vertical structure thin film LED chips with a reflective p-electrode and the N-face surface roughened after the removal of the epitaxial Si(111) substrates, to enhance the light extraction efficiency. We have commercialized GaN-on-Si LEDs with an average efficacy of 150-160 lm/W for 1mm2 LED chips at an injection current of 350 mA, which have passed the 10000-h LM80 reliability test. The as-produced GaN-on-Si LEDs featured with a single-side uniform emission and a nearly Lambertian distribution can adopt the wafer-level phosphor

  17. LED and Halogen Light Transmission through a CAD/CAM Lithium Disilicate Glass-Ceramic.

    Science.gov (United States)

    Pereira, Carolina Nemesio de Barros; De Magalhães, Cláudia Silami; Daleprane, Bruno; Peixoto, Rogéli Tibúrcio Ribeiro da Cunha; Ferreira, Raquel da Conceição; Cury, Luiz Alberto; Moreira, Allyson Nogueira

    2015-01-01

    The effect of thickness, shade and translucency of CAD/CAM lithium disilicate glass-ceramic on light transmission of light-emitting diode (LED) and quartz-tungsten-halogen units (QTH) were evaluated. Ceramic IPS e.max CAD shades A1, A2, A3, A3.5, high (HT) and low (LT) translucency were cut (1, 2, 3, 4 and 5 mm). Light sources emission spectra were determined. Light intensity incident and transmitted through each ceramic sample was measured to determine light transmission percentage (TP). Statistical analysis used a linear regression model. There was significant interaction between light source and ceramic translucency (p=0.008) and strong negative correlation (R=-0.845, pceramic thickness and TP. Increasing one unit in thickness led to 3.17 reduction in TP. There was no significant difference in TP (p=0.124) between shades A1 (ß1=0) and A2 (ß1=-0.45) but significant reduction occurred for A3 (ß1=-0.83) and A3.5 (ß1=-2.18). The interaction QTH/HT provided higher TP (ß1=0) than LED/HT (ß1=-2.92), QTH/LT (ß1=-3.75) and LED/LT (ß1=-5.58). Light transmission was more effective using halogen source and high-translucency ceramics, decreased as the ceramic thickness increased and was higher for the lighter shades, A1 and A2. From the regression model (R2=0.85), an equation was obtained to estimate TP value using each variable ß1 found. A maximum TP of 25% for QTH and 20% for LED was found, suggesting that ceramic light attenuation could compromise light cured and dual cure resin cements polymerization.

  18. Supporting Information Blue and White light electroluminescence in ...

    Indian Academy of Sciences (India)

    Administrator

    Blue and White light electroluminescence in a multilayer OLED using a new Aluminium complex. Pabitra K. Nayak a. , Neeraj Agarwal a. , Farman Ali a. , Meghan P. Patankar b. , K. L.. Narasimhan b. *, N. Periasamy a. *. 1. Department of Chemical Sciences,. 2. Department of Condensed Matter Physics and. Materials ...

  19. 4-Gbit/s visible light communication link based on 16-QAM OFDM transmission over remote phosphor-film converted white light by using blue laser diode

    KAUST Repository

    Duran Retamal, Jose Ramon

    2015-12-21

    Visible Light Communication (VLC) as a new technology for ultrahigh-speed communication is still limited when using slow modulation light-emitting diode (LED). Alternatively, we present a 4-Gbit/s VLC system using coherent blue-laser diode (LD) via 16-quadrature amplitude modulation orthogonal frequency division multiplexing. By changing the composition and the optical-configuration of a remote phosphor-film the generated white light is tuned from cool day to neutral, and the bit error rate is optimized from 1.9 × 10-2 to 2.8 × 10-5 in a blue filter-free link due to enhanced blue light transmission in forward direction. Briefly, blue-LD is an alternative to LED for generating white light and boosting the data rate of VLC. © 2015 Optical Society of America.

  20. 4-Gbit/s visible light communication link based on 16-QAM OFDM transmission over remote phosphor-film converted white light by using blue laser diode

    KAUST Repository

    Duran Retamal, Jose Ramon; Oubei, Hassan M.; Janjua, Bilal; Chi, Yu-Chieh; Wang, Huai-Yung; Tsai, Cheng-Ting; Ng, Tien Khee; Hsieh, Dan-Hua; Kuo, Hao-Chung; Alouini, Mohamed-Slim; He, Jr-Hau; Lin, Gong-Ru; Ooi, Boon S.

    2015-01-01

    Visible Light Communication (VLC) as a new technology for ultrahigh-speed communication is still limited when using slow modulation light-emitting diode (LED). Alternatively, we present a 4-Gbit/s VLC system using coherent blue-laser diode (LD) via 16-quadrature amplitude modulation orthogonal frequency division multiplexing. By changing the composition and the optical-configuration of a remote phosphor-film the generated white light is tuned from cool day to neutral, and the bit error rate is optimized from 1.9 × 10-2 to 2.8 × 10-5 in a blue filter-free link due to enhanced blue light transmission in forward direction. Briefly, blue-LD is an alternative to LED for generating white light and boosting the data rate of VLC. © 2015 Optical Society of America.

  1. PV led engine characterization lab for standalone light to light systems

    DEFF Research Database (Denmark)

    Thorsteinsson, Sune; Poulsen, Peter Behrensdorff; Lindén, Johannes

    2014-01-01

    PV-powered lighting systems, light-to-light systems (L2L), offer outdoor lighting where it is else where cumbersome to enable lighting. Application of these systems at high latitudes, where the difference in day length between summer and winter is large and the solar energy is low requires smart...... dimming functions for reliable lighting. In this work we have built a laboratory to characterize these systems up to 200 Wp from “nose to tail” in great details to support improvement of the systems and to make accurate field performance predictions....

  2. "Light-box" accelerated growth of poinsettias: LED-only illumination

    Science.gov (United States)

    Weerasuriya, Charitha; Detez, Stewart; Hock Ng, Soon; Hughes, Andrew; Callaway, Michael; Harrison, Iain; Katkus, Tomas; Juodkazis, Saulius

    2018-01-01

    For the current commercialized agricultural industry which requires a reduced product lead time to customer and supply all year round, an artificial light emitting diodes (LEDs)-based illumination has high potential due to high efficiency of electrical-to-light conversion. The main advantage of the deployed Red Green Blue Amber LED lighting system is colour mixing capability, which means ability to generate all the colours in the spectrum by using three or four primary colours LEDs. The accelerated plant growth was carried out in a "light-box" which was made to generate an artificial day/night cycle by moving the colour mixing ratio along the colour temperature curve of the chromaticity diagram. The control group of plants form the same initial batch was grown on the same shelf in a greenhouse at the same conditions with addition of artificial illumination by incandescent lamps for few hours. Costs and efficiency projections of LED lamps for horticultural applications is discussed together with required capital investment. The total cost of the "light-box" including LED lamps and electronics was 850 AUD.

  3. Investigation of Light-Emitting Diode (LED) Point Light Source Color Visibility against Complex Multicolored Backgrounds

    Science.gov (United States)

    2017-11-01

    authors. Statistical analyses and analysis plots were obtained using IBM SPSS Statistics.* 5.1 Threshold Visible Illuminance by LED Color and...LED Visibility vs. Outdoor Background Illuminance Across all camouflage materials, the outdoor distances of visibility are plotted with SPSS in Fig

  4. Improved light extraction from white organic light-emitting devices using a binary random phase array

    Energy Technology Data Exchange (ETDEWEB)

    Inada, Yasuhisa, E-mail: inada.yasuhisa@jp.panasonic.com; Nishiwaki, Seiji; Hirasawa, Taku; Nakamura, Yoshitaka; Hashiya, Akira; Wakabayashi, Shin-ichi; Suzuki, Masa-aki [R and D Division, Panasonic Corporation, 1006 Kadoma, Kadoma City, Osaka 571-8501 (Japan); Matsuzaki, Jumpei [Device Development Center, Eco Solutions Company, Panasonic Corporation, 1048 Kadoma, Osaka 571-8686 Japan (Japan)

    2014-02-10

    We have developed a binary random phase array (BRPA) to improve the light extraction performance of white organic light-emitting devices (WOLEDs). We demonstrated that the scattering of incoming light can be controlled by employing diffraction optics to modify the structural parameters of the BRPA. Applying a BRPA to the substrate of the WOLED leads to enhanced extraction efficiency and suppression of angle-dependent color changes. Our systematic study clarifies the effect of scattering on the light extraction of WOLEDs.

  5. Improved light extraction from white organic light-emitting devices using a binary random phase array

    International Nuclear Information System (INIS)

    Inada, Yasuhisa; Nishiwaki, Seiji; Hirasawa, Taku; Nakamura, Yoshitaka; Hashiya, Akira; Wakabayashi, Shin-ichi; Suzuki, Masa-aki; Matsuzaki, Jumpei

    2014-01-01

    We have developed a binary random phase array (BRPA) to improve the light extraction performance of white organic light-emitting devices (WOLEDs). We demonstrated that the scattering of incoming light can be controlled by employing diffraction optics to modify the structural parameters of the BRPA. Applying a BRPA to the substrate of the WOLED leads to enhanced extraction efficiency and suppression of angle-dependent color changes. Our systematic study clarifies the effect of scattering on the light extraction of WOLEDs

  6. Effect of LED-LCU light irradiance distribution on mechanical properties of resin based materials

    Energy Technology Data Exchange (ETDEWEB)

    Magalhães Filho, T.R.; Weig, K.M. [Faculdade de Odontologia, Universidade Federal Fluminense, Rua São Paulo 28, CEP 24020-150 Niterói (Brazil); Engenharia Metalúrgica e de Materiais (COPPE), Universidade Federal do Rio de Janeiro, CP 68505, CEP: 21941-972 Rio de Janeiro (Brazil); Costa, M.F. [Engenharia Metalúrgica e de Materiais (COPPE), Universidade Federal do Rio de Janeiro, CP 68505, CEP: 21941-972 Rio de Janeiro (Brazil); Werneck, M.M. [Engenharia Elétrica (COPPE), Universidade Federal do Rio de Janeiro, CP 68504, CEP: 21941-972 Rio de Janeiro (Brazil); Barthem, R.B. [Instituto de Física, Universidade Federal do Rio de Janeiro, CP 68528, CEP: 21941-972 Rio de Janeiro (Brazil); Costa Neto, C.A., E-mail: celio@metalmat.ufrj.br [Engenharia Metalúrgica e de Materiais (COPPE), Universidade Federal do Rio de Janeiro, CP 68505, CEP: 21941-972 Rio de Janeiro (Brazil)

    2016-06-01

    The objective of this study is to analyze the light power distribution along the tip end of the light guide of three LED-LCUs (Light Curing Units) and to evaluate its effect on the mechanical properties of a polymer based dental composite. Firstly, the light power distribution over the whole area of LED-LCU light guide surface was analyzed by three methods: visual projection observation, spectral measurement and optical spectral analysis (OSA). The light power distribution and the total irradiance were different for the three LEDs used, but the wavelength was within the camphorquinone absorption spectrum. The use of a blank sheet was quite on hand to make a qualitative analysis of a beam, and it is costless. Secondly, specimens of a hybrid composite with approximately 8 mm diameter and 2 mm thickness were produced and polymerized by 20 s exposition time to each LED-LCU. Thirdly, the elastic modulus (E) and hardness (HV) were measured throughout the irradiated area by instrumented micro-indentation test (IIT), allowing to correlate localized power and mechanical properties. Both E and HV showed to be very sensitive to local power and wavelength dependent, but they followed the beam power profile. It was also shown that the mechanical properties could be directly correlated to the curing process. Very steep differences in mechanical properties over very short distances may impair the material performance, since residual stresses can easily be built over it. - Highlights: • A resin based composite (RBC) was polymerized by three different Light Emitting Diodes. • Each LED had its beam profile visually, wavelength and power analyzed. • The effective polymerization power (EPP) varied from 28% to 52% of the total beam power. • Wavelength seems to be as relevant as power in the light curing process. • Mechanical properties depend on the simultaneous effect of wavelength and power.

  7. Effect of LED-LCU light irradiance distribution on mechanical properties of resin based materials

    International Nuclear Information System (INIS)

    Magalhães Filho, T.R.; Weig, K.M.; Costa, M.F.; Werneck, M.M.; Barthem, R.B.; Costa Neto, C.A.

    2016-01-01

    The objective of this study is to analyze the light power distribution along the tip end of the light guide of three LED-LCUs (Light Curing Units) and to evaluate its effect on the mechanical properties of a polymer based dental composite. Firstly, the light power distribution over the whole area of LED-LCU light guide surface was analyzed by three methods: visual projection observation, spectral measurement and optical spectral analysis (OSA). The light power distribution and the total irradiance were different for the three LEDs used, but the wavelength was within the camphorquinone absorption spectrum. The use of a blank sheet was quite on hand to make a qualitative analysis of a beam, and it is costless. Secondly, specimens of a hybrid composite with approximately 8 mm diameter and 2 mm thickness were produced and polymerized by 20 s exposition time to each LED-LCU. Thirdly, the elastic modulus (E) and hardness (HV) were measured throughout the irradiated area by instrumented micro-indentation test (IIT), allowing to correlate localized power and mechanical properties. Both E and HV showed to be very sensitive to local power and wavelength dependent, but they followed the beam power profile. It was also shown that the mechanical properties could be directly correlated to the curing process. Very steep differences in mechanical properties over very short distances may impair the material performance, since residual stresses can easily be built over it. - Highlights: • A resin based composite (RBC) was polymerized by three different Light Emitting Diodes. • Each LED had its beam profile visually, wavelength and power analyzed. • The effective polymerization power (EPP) varied from 28% to 52% of the total beam power. • Wavelength seems to be as relevant as power in the light curing process. • Mechanical properties depend on the simultaneous effect of wavelength and power.

  8. Secrecy Dimming Capacity in Multi-LED PAM-Based Visible Light Communications

    Directory of Open Access Journals (Sweden)

    Byung Wook Kim

    2017-01-01

    Full Text Available Recently, mobile cloud computing (MCC has gained a lot of interest for researchers building the next-generation mobile applications. Because unauthorized access may cause serious problems, security and privacy with MCC have become significant issues. This paper addresses the secrecy dimming capacity of secure transmission in MCC over visible light communication (VLC channels. By obtaining the entropy-maximizing symbol probability of multiple light emitting diode- (LED- based pulse amplitude modulation (PAM, mathematical analysis of the secrecy dimming capacity of VLC was derived. Simulation results show that the secure transmission ability of multi-LED-based VLC is determined according to the number of activated LEDs and target dimming level. This can be a guideline for practical VLC-based mobile network designers intending to secure wireless transmission and to decide on the number of activated LEDs at target dimming level to operate.

  9. Direct battery-driven solar LED lighting using constant-power control

    KAUST Repository

    Huang, Bin-Juine

    2012-11-01

    A direct battery-driven LED lighting technique using constant-power control is proposed in the present study. A system dynamics model of LED luminaire was derived and used in the design of the feedback constant-power control system. The test result has shown that the power of 18. W and 100. W LED luminaires can be controlled accurately with error at 2-5%. A solar LED street lighting system using constant-power and dimming control was designed and built for field test in a remote area. The long-term performance was satisfactory and no any failure since the installation. Since no high-power capacitor is used in the present constant-power control circuit, a longer lifetime is expected. © 2012 Elsevier Ltd.

  10. White OLED devices and processes for lighting applications

    Science.gov (United States)

    Ide, Nobuhiro; Tsuji, Hiroya; Ito, Norihiro; Matsuhisa, Yuko; Houzumi, Shingo; Nishimori, Taisuke

    2010-05-01

    In these days, the basic performances of white OLEDs are dramatically improved and application of OLEDs to "Lighting" is expected to be true in the near future. We have developed various technologies for OLED lighting with the aid of the Japanese governmental project, "High-efficiency lighting based on the organic light-emitting mechanism." In this project, a white OLED with high efficiency (37 lm/W) and high quality emission characteristics (CRI of 95 with a small variation of chromaticity in different directions and chromaticity just on the black-body radiation curve) applicable to "Lighting" was realized by a two-unit structure with a fluorescent deep blue emissive unit and a phosphorescent green and red emissive unit. Half-decay lifetime of this white OLED at 1,000 cd/m2 was over 40,000 h. A heat radiative, thin encapsulation structure (less than 1 mm) realized a very stable emission at high luminance of over 3,000 cd/m2. A new deposition source with a hot-wall and a rate controllable valve was developed. Thickness uniformity within +/- 3% at high deposition rate of over 8 nm/s, high material utilization of over 70 %, and repeatable deposition rate controllability were confirmed.

  11. Yuma Border Patrol Lighting Retrofit: Final LED System Performance Assessment of Trial and Full Installation

    Energy Technology Data Exchange (ETDEWEB)

    Andrea Wilkerson, Gregory P Sullivan, Robert G Davis, Sarah Safranek

    2018-04-30

    Along the Yuma Sector Border Patrol Area in Yuma, Arizona, the GATEWAY program conducted a trial evaluation in which the incumbent quartz metal halide area lighting was replaced with LED at three pole locations, and illuminance measurements were recorded initially and at 2500 hours, 5000 hours, 7000, and 11,000 hours of operation. Additionally, four second-generation LED luminaires installed as part of the full installation were evaluated initially and again after 4,000 hours of operation. While the initial energy, lighting quality, and maintenance benefits relative to the incumbent high-pressure sodium system were very satisfactory, the study raises important questions regarding the long-term performance of LED lighting systems in high-temperature environments.

  12. Optimization of colour quality of LED lighting with reference to memory colours

    OpenAIRE

    Smet, Kevin; Ryckaert, Wouter; Pointer, Michael R.; Deconinck, Geert; Hanselaer, Peter

    2012-01-01

    Simulated and real tri- and tetrachromatic light-emitting-diode (LED) clusters were optimized for luminous efficacy of radiation (LER) and the memory colour quality metric developed by the authors. The simulated clusters showed no significant differences in achievable colour quality and LER between the different cluster types investigated. The real clusters (composed of commercially available LEDs) showed substantial differences in achievable colour quality and LER between the different clus...

  13. Light extraction from GaN-based LED structures on silicon-on-insulator substrates

    Energy Technology Data Exchange (ETDEWEB)

    Tripathy, S.; Teo, S.L.; Lin, V.K.X.; Chen, M.F. [Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology, and Research), 117602 (Singapore); Dadgar, A.; Krost, A. [Institut fuer Exerimentelle Physik, Otto-von Guericke Universitaet Magdeburg, Universitaetsplatz 1, 39016 Magdeburg (Germany); AZZURRO Semiconductors AG, Universitaetsplatz 1, 39016 Magdeburg (Germany); Christen, J. [Institut fuer Exerimentelle Physik, Otto-von Guericke Universitaet Magdeburg, Universitaetsplatz 1, 39016 Magdeburg (Germany)

    2010-01-15

    Nano-patterning of GaN-based devices is a promising technology in the development of high output power devices. Recent researches have been focused on the realization of two-dimensional (2D) photonic crystal (PhC) structure to improve light extraction efficiency and to control the direction of emission. In this study, we have demonstrated improved light extraction from green light emitting diode (LED) structures on thin silicon-on-insulator (SOI) substrates using surface nanopatterning. Scanning electron microscopy (SEM) is used to probe the size, shape, and etch depth of nano-patterns on the LED surfaces. Different types of nanopatterns were created by e-beam lithography and inductively coupled plasma etching. The LED structures after post processing are studied by photoluminescence (PL) measurements. The GaN nanophotonic structures formed by ICP etching led to more than five-fold increase in the intensity of the green emission. The improved light extraction is due to the combination of SOI substrate reflectivity and photonic structures on top GaN LED surfaces. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  14. Double-Grating Displacement Structure for Improving the Light Extraction Efficiency of LEDs

    Directory of Open Access Journals (Sweden)

    Zhibin Wang

    2012-01-01

    Full Text Available To improve the light extraction efficiency of light-emitting diodes (LEDs, grating patterns were etched on GaN and silver film surfaces. The grating-patterned surface etching enabled the establishment of an LED model with a double-grating displacement structure that is based on the surface plasmon resonance principle. A numerical simulation was conducted using the finite difference time domain method. The influence of different grating periods for GaN surface and silver film thickness on light extraction efficiency was analyzed. The light extraction efficiency of LEDs was highest when the grating period satisfied grating coupling conditions. The wavelength of the highest value was also close to the light wavelength of the medium. The plasmon resonance frequencies on both sides of the silver film were affected by silver film thickness. With increasing film thickness, plasmon resonance frequency tended toward the same value and light extraction efficiency reached its maximum. When the grating period for the GaN surface was 365 nm and the silver film thickness was 390 nm, light extraction efficiency reached a maximum of 55%.

  15. Smart LED allocation scheme for efficient multiuser visible light communication networks.

    Science.gov (United States)

    Sewaiwar, Atul; Tiwari, Samrat Vikramaditya; Chung, Yeon Ho

    2015-05-18

    In a multiuser bidirectional visible light communication (VLC), a large number of LEDs or an LED array needs to be allocated in an efficient manner to ensure sustainable data rate and link quality. Moreover, in order to support an increasing or decreasing number of users in the network, the LED allocation is required to be performed dynamically. In this paper, a novel smart LED allocation scheme for efficient multiuser VLC networks is presented. The proposed scheme allocates RGB LEDs to multiple users in a dynamic and efficient fashion, while satisfying illumination requirements in an indoor environment. The smart LED array comprised of RGB LEDs is divided into sectors according to the location of the users. The allocated sectors then provide optical power concentration toward the users for efficient and reliable data transmission. An algorithm for the dynamic allocation of the LEDs is also presented. To verify its effective resource allocation feature of the proposed scheme, simulations were performed. It is found that the proposed smart LED allocation scheme provides the effect of optical beamforming toward individual users, thereby increasing the collective power concentration of the optical signals on the desirable users and resulting in significantly increased data rate, while ensuring sufficient illumination in a multiuser VLC environment.

  16. Assessment of filament led bulbs with respect to temporal light artefacts

    DEFF Research Database (Denmark)

    Lindén, Johannes; Thorseth, Anders; Corell, Dennis Dan

    2017-01-01

    Temporal light artefacts, abbreviated TLAs (including flicker, stroboscopic effect and phantom arrays), i.e. undesired time modulation in luminance from a light source, has shown to be a threat to wider SSL adoption especially related to dimming functions and low-quality LED products. This is due...... to the effects that both noticeable and unperceivable TLAs have on human perception and wellbeing. In the present work a number of filament LED bulbs, currently available on the market, are assessed primarily with respect to TLAs, but also with respect to photometric, colorimetric and efficiency properties...

  17. White light generation tuned by dual hybridization of nanocrystals and conjugated polymers

    International Nuclear Information System (INIS)

    Demir, Hilmi Volkan; Nizamoglu, Sedat; Ozel, Tuncay; Mutlugun, Evren; Huyal, Ilkem Ozge; Sari, Emre; Holder, Elisabeth; Tian Nan

    2007-01-01

    Dual hybridization of highly fluorescent conjugated polymers and highly luminescent nanocrystals (NCs) is developed and demonstrated in multiple combinations for controlled white light generation with high color rendering index (CRI) (> 80) for the first time. The generated white light is tuned using layer-by-layer assembly of CdSe/ZnS core-shell NCs closely packed on polyfluorene, hybridized on near-UV emitting nitride-based light emitting diodes (LEDs). The design, synthesis, growth, fabrication and characterization of these hybrid inorganic-organic white LEDs are presented. The following experimental realizations are reported: (i) layer-by-layer hybridization of yellow NCs (λ PL =580 nm) and blue polyfluorene (λ PL =439 nm) with tristimulus coordinates of (x, y)=(0.31, 0.27), correlated color temperature of T c =6962 K and CRI of R a =53.4; (ii) layer-by-layer assembly of yellow and green NCs (λ PL =580 and 540 nm) and blue polyfluorene (λ PL =439 nm) with (x, y)=(0.23, 0.30), T c =14395 K and R a =65.7; and (iii) layer-by-layer deposition of yellow, green and red NCs (λ PL =580, 540 and 620 nm) and blue polyfluorene (λ PL =439 nm) with (x, y)=(0.38, 0.39), T c =4052 K and R a = 83.0. The CRI is demonstrated to be well controlled and significantly improved by increasing multi-chromaticity of the NC and polymer emitters

  18. Study of system dynamics model and control of a high-power LED lighting luminaire

    International Nuclear Information System (INIS)

    Huang, B.-J.; Hsu, P.-C.; Wu, M.-S.; Tang, C.-W.

    2007-01-01

    The purpose of the present study is to design a current control system which is robust to the system dynamics uncertainty and the disturbance of ambient temperature to assure a stable optical output property of LED. The system dynamics model of the LED lighting system was first derived. A 96 W high-power LED luminaire was designed and built in the present study. The linearly perturbed system dynamics model for the LED luminaire is derived experimentally. The dynamics model of LED lighting system is of a multiple-input-multiple-output (MIMO) system with two inputs (applied voltage and ambient temperature) and two outputs (forward current and heat conducting body temperature). A step response test method was employed to the 96 W LED luminaire to identify the system dynamics model. It is found that the current model is just a constant gain (resistance) and the disturbance model is of first order, both changing with operating conditions (voltage and ambient temperature). A feedback control system using PI algorithm was designed using the results of the system dynamics model. The control system was implemented on a PIC microprocessor. Experimental results show that the control system can stably and accurately control the LED current to a constant value at the variation of ambient temperature up to 40 o C. The control system is shown to have a robust property with respect to the plant uncertainty and the ambient temperature disturbance

  19. White polymer light-emitting diode based on polymer blending

    International Nuclear Information System (INIS)

    Lee, Yong Kyun; Kwon, Soon Kab; Kim, Jun Young; Park, Tae Jin; Song, Dae Ho; Kwon, Jang Hyuk; Choo, Dong Jun; Jang, Jin; Jin, Jae Kyu; You, Hong

    2006-01-01

    A series of white polymer light emitting devices have been fabricated by using a polymer blending system of polyfluorene-based blue and MEH-PPV red polymers. A device structure of ITO/PEDOT:PSS/polymer/LiF/Al was employed. The white polymer device exhibited a current efficiency of 4.33 cd/A (4,816 cd/m 2 , Q.E. = 1.9 %) and a maximum luminance of 21,430 cd/m 2 at 9.2 V. The CIE coordinates were (0.35, 0.37) at 5 V and (0.29, 0.30) at 9 V.

  20. GATEWAY Demonstrations: Tuning Hospital Lighting: Evaluating Tunable LED Lighting at the Swedish Hospital Behavioral Health Unit in Seattle

    Energy Technology Data Exchange (ETDEWEB)

    Wilkerson, Andrea [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Davis, Robert G. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Clark, Edward [ZGF Architects LLP, Seattle, WA (United States)

    2017-08-23

    The GATEWAY program evaluated a tunable LED lighting system installed in the new Swedish Medical Behavioral Health Unit in Seattle that incorporates color-tunable luminaires in common areas, and uses advanced controls for dimming and color tuning, with the goal of providing a better environment for staff and patients. The report reviews the design of the tunable lighting system, summarizes two sets of measurements, and discusses the circadian, energy, and commissioning implications as well as lessons learned from the project.

  1. Stakeholder Values and Perspectives when Implementing Led Lights on Navy Ships

    Science.gov (United States)

    2014-06-01

    Human Factors in Lighting Freymiller, 2009, from Boyce, 2003) LEDs have no known cause of headaches due to flicker and the electronic magnetic...reoccurrence of dimming and flickering can reoccur. There should be further research conducted on how a headache affects the loss of productivity on...Walls, P. M. (2011, Dec). Eye disease resulting from increased use of fluorescent lighting as a climate change mitigation strategy. Retrieved from

  2. Slim planar apparatus for converting LED light into collimated polarized light uniformly emitted from its top surface.

    Science.gov (United States)

    Teng, Tun-Chien; Tseng, Li-Wei

    2014-10-20

    This study proposes a slim planar apparatus for converting nonpolarized light from a light-emitting diode (LED) into an ultra-collimated linearly polarized beam uniformly emitted from its top surface. The apparatus was designed based on a folded-bilayer configuration comprising a light-mixing collimation element, polarization conversion element, and polarization-preserving light guide plate (PPLGP) with an overall thickness of 5 mm. Moreover, the apparatus can be extended transversally by connecting multiple light-mixing collimation elements and polarization conversion elements in a side-by-side configuration to share a considerably wider PPLGP, so the apparatus can have theoretically unlimited width. The simulation results indicate that the proposed apparatus is feasible for the maximal backlight modules in 39-inch liquid crystal panels. In the case of an apparatus with a 480 × 80 mm emission area and two 8-lumen LED light sources, the average head-on polarized luminance and spatial uniformity over the emission area was 5000 nit and 83%, respectively; the vertical and transverse angular distributions of the emitting light were only 5° and 10°, respectively. Moreover, the average degree of polarization and energy efficiency of the apparatus were 82% and 72%, respectively. As compared with the high-performance ultra-collimated nonpolarized backlight module proposed in our prior work, not only did the apparatus exhibit outstanding optical performance, but also the highly polarized light emissions actually increased the energy efficiency by 100%.

  3. Human Adolescent Phase Response Curves to Bright White Light.

    Science.gov (United States)

    Crowley, Stephanie J; Eastman, Charmane I

    2017-08-01

    Older adolescents are particularly vulnerable to circadian misalignment and sleep restriction, primarily due to early school start times. Light can shift the circadian system and could help attenuate circadian misalignment; however, a phase response curve (PRC) to determine the optimal time for receiving light and avoiding light is not available for adolescents. We constructed light PRCs for late pubertal to postpubertal adolescents aged 14 to 17 years. Participants completed 2 counterbalanced 5-day laboratory sessions after 8 or 9 days of scheduled sleep at home. Each session included phase assessments to measure the dim light melatonin onset (DLMO) before and after 3 days of free-running through an ultradian light-dark (wake-sleep) cycle (2 h dim [~20 lux] light, 2 h dark). In one session, intermittent bright white light (~5000 lux; four 20-min exposures) was alternated with 10 min of dim room light once per day for 3 consecutive days. The time of light varied among participants to cover the 24-h day. For each individual, the phase shift to bright light was corrected for the free-run derived from the other laboratory session with no bright light. One PRC showed phase shifts in response to light start time relative to the DLMO and another relative to home sleep. Phase delay shifts occurred around the hours corresponding to home bedtime. Phase advances occurred during the hours surrounding wake time and later in the afternoon. The transition from delays to advances occurred at the midpoint of home sleep. The adolescent PRCs presented here provide a valuable tool to time bright light in adolescents.

  4. Zinc oxide nanorods/polymer hybrid heterojunctions for white light emitting diodes

    Science.gov (United States)

    Willander, M.; Nur, O.; Zaman, S.; Zainelabdin, A.; Bano, N.; Hussain, I.

    2011-06-01

    Zinc oxide (ZnO) with its deep level defect emission covering the whole visible spectrum holds promise for the development of intrinsic white lighting sources with no need of using phosphors for light conversion. ZnO nanorods (NRs) grown on flexible plastic as substrate using a low temperature approach (down to 50 °C) were combined with different organic semiconductors to form hybrid junction. White electroluminescence (EL) was observed from these hybrid junctions. The configuration used for the hybrid white light emitting diodes (LEDs) consists of two-layers of polymers on the flexible plastic with ZnO NRs on the top. The inorganic/organic hybrid heterojunction has been fabricated by spin coating the p-type polymer poly (3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT : PSS) for hole injection with an ionization potential of 5.1 eV and poly(9, 9-dioctylfluorene) (PFO) is used as blue emitting material with a bandgap of 3.3 eV. ZnO NRs are grown on top of the organic layers. Two other configurations were also fabricated; these are using a single MEH PPV (red-emitting polymer) instead of the PFO and the third configuration was obtained from a blend of the PFO and the MEH PPV. The white LEDs were characterized by scanning electron microscope, x-ray diffraction (XRD), current-voltage (I-V) characteristics, room temperature photoluminescence (PL) and EL. The EL spectrum reveals a broad emission band covering the range from 420 to 800 nm, and the emissions causing this white luminescence were identified.

  5. Zinc oxide nanorods/polymer hybrid heterojunctions for white light emitting diodes

    International Nuclear Information System (INIS)

    Willander, M; Nur, O; Zaman, S; Zainelabdin, A; Bano, N; Hussain, I

    2011-01-01

    Zinc oxide (ZnO) with its deep level defect emission covering the whole visible spectrum holds promise for the development of intrinsic white lighting sources with no need of using phosphors for light conversion. ZnO nanorods (NRs) grown on flexible plastic as substrate using a low temperature approach (down to 50 0 C) were combined with different organic semiconductors to form hybrid junction. White electroluminescence (EL) was observed from these hybrid junctions. The configuration used for the hybrid white light emitting diodes (LEDs) consists of two-layers of polymers on the flexible plastic with ZnO NRs on the top. The inorganic/organic hybrid heterojunction has been fabricated by spin coating the p-type polymer poly (3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT : PSS) for hole injection with an ionization potential of 5.1 eV and poly(9, 9-dioctylfluorene) (PFO) is used as blue emitting material with a bandgap of 3.3 eV. ZnO NRs are grown on top of the organic layers. Two other configurations were also fabricated; these are using a single MEH PPV (red-emitting polymer) instead of the PFO and the third configuration was obtained from a blend of the PFO and the MEH PPV. The white LEDs were characterized by scanning electron microscope, x-ray diffraction (XRD), current-voltage (I-V) characteristics, room temperature photoluminescence (PL) and EL. The EL spectrum reveals a broad emission band covering the range from 420 to 800 nm, and the emissions causing this white luminescence were identified.

  6. All-inorganic white light emitting devices based on ZnO nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Nannen, Ekaterina

    2012-09-21

    Semiconductor nanaocrystals (NCs) are very promising candidates for lightweight large-area rollable displays and light emitting devices (LEDs). They are expected to combine the efficiency, robustness and color tunability of conventional semiconductor LEDs with the flexible fabrication techniques known from OLED technology, since the NCs are compatible with solution processing and therefore can be deposited on virtually any substrates including glass and plastic. Today, NC-LEDs consist of chemically synthesized QDs embedded in organic charge injection and transport layers. The organic layers limit the robustness of the NC-LEDs and result in significant constrictions within the device fabrication procedure, such as organic evaporation steps, inert (i.e. humidity and oxygen free) atmosphere and obligatory encapsulation. These limitations during the production process as well as complex chemical synthesis route of the implemented NCs and organic components lead to high fabrication costs and low turnover. So far, only prototype devices have been introduced by several research groups and industrial companies. Still, the main concern retarding NC-LEDs from market launch is the high content of toxic heavy metals like Cd in the active nanocrystalline light emitting material. Within this work, possible environmentally safe and ambient-air-compatible alternatives to conventional QDs and organics were explored, with the main focus on design and fabrication of completely inorganic white NC-LEDs with commercial ZnO nanoparticles as an active light emitting material. While the electrical transport properties through the NC-network of the commercially available VP AdNano {sup registered} ZnO2O particles were already to some extent explored, their optical properties and therefore suitability as an active light emitter in NC-LEDs were not studied so far. (orig.)

  7. Protocol for Determining Ultraviolet Light Emitting Diode (UV-LED) Fluence for Microbial Inactivation Studies.

    Science.gov (United States)

    Kheyrandish, Ataollah; Mohseni, Madjid; Taghipour, Fariborz

    2018-06-15

    Determining fluence is essential to derive the inactivation kinetics of microorganisms and to design ultraviolet (UV) reactors for water disinfection. UV light emitting diodes (UV-LEDs) are emerging UV sources with various advantages compared to conventional UV lamps. Unlike conventional mercury lamps, no standard method is available to determine the average fluence of the UV-LEDs, and conventional methods used to determine the fluence for UV mercury lamps are not applicable to UV-LEDs due to the relatively low power output, polychromatic wavelength, and specific radiation profile of UV-LEDs. In this study, a method was developed to determine the average fluence inside a water suspension in a UV-LED experimental setup. In this method, the average fluence was estimated by measuring the irradiance at a few points for a collimated and uniform radiation on a Petri dish surface. New correction parameters were defined and proposed, and several of the existing parameters for determining the fluence of the UV mercury lamp apparatus were revised to measure and quantify the collimation and uniformity of the radiation. To study the effect of polychromatic output and radiation profile of the UV-LEDs, two UV-LEDs with peak wavelengths of 262 and 275 nm and different radiation profiles were selected as the representatives of typical UV-LEDs applied to microbial inactivation. The proper setup configuration for microorganism inactivation studies was also determined based on the defined correction factors.

  8. Demonstration Assessment of Light-Emitting Diode (LED) Roadway Lighting at the I-35W Bridge, Minneapolis, MN

    Energy Technology Data Exchange (ETDEWEB)

    Kinzey, Bruce R.; Myer, Michael

    2009-08-31

    This report describes the process and results of a demonstration of solid-state lighting (SSL) technology conducted in 2009 at the recently reconstructed I-35W bridge in Minneapolis, MN. The project was supported under the U.S. Department of Energy (DOE) Solid-State Lighting GATEWAY Technology Demonstration Program. Other participants in the demonstration project included the Minnesota Department of Transportation (Mn/DOT), Federal Highways Administration (FHWA), and BetaLED™ (a division of Ruud Lighting). Pacific Northwest National Laboratory (PNNL) conducted the measurements and analysis of the results. DOE has implemented a three-year evaluation of the LED luminaires in this installation in order to develop new longitudinal field data on LED performance in a challenging, real-world environment. This document provides information through the initial phase of the I-35W bridge project, up to and including the opening of the bridge to the public and the initial feedback received on the LED lighting installation from bridge users. Initial findings of the evaluation are favorable, with minimum energy savings level of 13% for the LED installation relative to the simulated base case using 250W high-pressure sodium (HPS) fixtures. The LEDs had an average illuminance level of 0.91 foot candles compared to 1.29 fc for the HPS lamps. The LED luminaires cost $38,000 more than HPS lamps, yielding a lengthy payback period, however the bridge contractor had offered to include the LED luminaires as part of the construction package at no additional cost. One potentially significant benefit of the LEDs in this installation is avoiding rolling lane closures on the heavily-traveled interstate bridge for the purpose of relamping the HPS fixtures. Rolling lane closures involve multiple crew members and various maintenance and safety vehicles, diversion of traffic, as well as related administrative tasks (e.g., approvals, scheduling, etc.). Mn/DOT records show an average cost of

  9. Design and fabrication of adjustable red-green-blue LED light arrays for plant research

    Directory of Open Access Journals (Sweden)

    Kenitz J Dustin

    2005-08-01

    Full Text Available Abstract Background Although specific light attributes, such as color and fluence rate, influence plant growth and development, researchers generally cannot control the fine spectral conditions of artificial plant-growth environments. Plant growth chambers are typically outfitted with fluorescent and/or incandescent fixtures that provide a general spectrum that is accommodating to the human eye and not necessarily supportive to plant development. Many studies over the last several decades, primarily in Arabidopsis thaliana, have clearly shown that variation in light quantity, quality and photoperiod can be manipulated to affect growth and control developmental transitions. Light emitting diodes (LEDs has been used for decades to test plant responses to narrow-bandwidth light. LEDs are particularly well suited for plant growth chambers, as they have an extraordinary life (about 100,000 hours, require little maintenance, and use negligible energy. These factors render LED-based light strategies particularly appropriate for space-biology as well as terrestrial applications. However, there is a need for a versatile and inexpensive LED array platform where individual wavebands can be specifically tuned to produce a series of light combinations consisting of various quantities and qualities of individual wavelengths. Two plans are presented in this report. Results In this technical report we describe the practical construction of tunable red-green-blue LED arrays to support research in plant growth and development. Two light fixture designs and corresponding circuitry are presented. The first is well suited for a laboratory environment for use in a finite area with small plants, such as Arabidopsis. The second is expandable and appropriate for growth chambers. The application of these arrays to early plant developmental studies has been validated with assays of hypocotyl growth inhibition/promotion and phototropic curvature in Arabidopsis seedlings

  10. Solid State pH Sensor Based on Light Emitting Diodes (LED) As Detector Platform

    Science.gov (United States)

    Lau, King Tong; Shepherd, R.; Diamond, Danny; Diamond, Dermot

    2006-01-01

    A low-power, high sensitivity, very low-cost light emitting diode (LED)-based device developed for low-cost sensor networks was modified with bromocresol green membrane to work as a solid-state pH sensor. In this approach, a reverse-biased LED functioning as a photodiode is coupled with a second LED configured in conventional emission mode. A simple timer circuit measures how long (in microsecond) it takes for the photocurrent generated on the detector LED to discharge its capacitance from logic 1 (+5 V) to logic 0 (+1.7 V). The entire instrument provides an inherently digital output of light intensity measurements for a few cents. A light dependent resistor (LDR) modified with similar sensor membrane was also used as a comparison method. Both the LED sensor and the LDR sensor responded to various pH buffer solutions in a similar way to obtain sigmoidal curves expected of the dye. The pKa value obtained for the sensors was found to agree with the literature value.

  11. A high-performance stand-alone solar PV power system for LED lighting

    KAUST Repository

    Huang, B. J.; Hsu, P. C.; Wu, M. S.; Chen, K.Y.

    2010-01-01

    The present study developed a high-performance solar PV power technology for the LED lighting of a solar home system. The nMPPO (near-Maximum-Power- Point- Operation) design is employed in system design to eliminate MPPT. A feedback control system

  12. Light outputs of LED with various refractive indices and geometrical structures of encapsulants

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Kyung-Tae [Chosun University, Gwangju (Korea, Republic of); Jo, Kyoung-Woo; Hwang, Jung-Ha; Kwon, Ho-Ki [LG Innotek Co., Ltd., Seoul (Korea, Republic of); Park, Si-Hyun [Yeungnam University, Gyeongsan (Korea, Republic of)

    2010-12-15

    In this paper we present the results of experiments and simulations for the light output power from LEDs for various refractive indices and the geometrical structures of the LED encapsulants. InGaN-based LED chips were fabricated and were bonded in Ag reflector cups within polyphthalamide (PPA) chip carriers; then, encapsulants with various refractive indices and the geometrical structures were fabricated onto them by using a dispensing method. The light output power with the encapsulant was shown to increase with the refractive index of the encapsulant materials in the case of a spherical encapsulant while it decreased in the case of a flat geometry encapsulant. We performed ray tracing simulations for the LED light output and confirmed that the simulation results were consistent with our experimentally measured results. In addition, the light output with the encapsulant rapidly increased with the sidewall angle of the chip carrier in the case of the flat encapsulant while it was not affected by the sidewall angle, remaining constant, in the case of the spherical geometry.

  13. Light outputs of LED with various refractive indices and geometrical structures of encapsulants

    International Nuclear Information System (INIS)

    Kim, Kyung-Tae; Jo, Kyoung-Woo; Hwang, Jung-Ha; Kwon, Ho-Ki; Park, Si-Hyun

    2010-01-01

    In this paper we present the results of experiments and simulations for the light output power from LEDs for various refractive indices and the geometrical structures of the LED encapsulants. InGaN-based LED chips were fabricated and were bonded in Ag reflector cups within polyphthalamide (PPA) chip carriers; then, encapsulants with various refractive indices and the geometrical structures were fabricated onto them by using a dispensing method. The light output power with the encapsulant was shown to increase with the refractive index of the encapsulant materials in the case of a spherical encapsulant while it decreased in the case of a flat geometry encapsulant. We performed ray tracing simulations for the LED light output and confirmed that the simulation results were consistent with our experimentally measured results. In addition, the light output with the encapsulant rapidly increased with the sidewall angle of the chip carrier in the case of the flat encapsulant while it was not affected by the sidewall angle, remaining constant, in the case of the spherical geometry.

  14. Effect of buck driver ripple on BER performance in visible light communication using LED

    NARCIS (Netherlands)

    Deng, X.; Linnartz, J.P.M.G.; Arulandu, K.; Zhou, G.; Wu, Y.

    2015-01-01

    This paper analyses the communication performance for visible light communication (VLC) with Manchester encoded amplitude modulation. In particular, it considers the ripple generated by the LED driver as an important noise contribution for VLC. The ripple depends on the oscillation frequency of the

  15. Raman study of the effect of LED light on grafted bone defects

    Science.gov (United States)

    Soares, Luiz G. G. P.; Aciole, Jouber M. S.; Aciole, Gilbeth T. S.; Barbosa, Artur F. S.; Silveira-Júnior, Landulfo; Pinheiro, Antônio L. B.

    2013-03-01

    Benefits of the isolated or combined use light and biomaterials on bone healing have been suggested. Our group has used several models to assess the effects of laser on bone. A Raman spectral analysis on surgical bone defects grafted or not with Hydroxyapatite (HA), treated or not with LED was carried out. 40 rats were divided into 4 groups. On Group I the defect was filled with the clot. On Group II, the defect was filled with the HA. On groups III the defect was filled with Clot and further irradiated with LED and on group IV the defects was filled with the HA and further irradiated with LED. LED (λ850 +/- 10nm, 150mW, A= 0.5cm2, 68s, 20 J/cm2 per session, 140 J/cm2 per treatment) was applied at 48 h intervals during 15 days. Specimens were taken after 15 and 30 days after surgery and kept on liquid nitrogen, and underwent Raman analysis. For this, the peak of hydroxyapatite (~960 cm-1) was used as marker of bone mineralization. Significant difference was observed at both times (p<0.05). When the biomaterial was used higher peaks were observed. Association with LED further improved the intensity. Conclusion: It is concluded that LED light improved the effect of the HA.

  16. Recent advances in light outcoupling from white organic light-emitting diodes

    Science.gov (United States)

    Gather, Malte C.; Reineke, Sebastian

    2015-01-01

    Organic light-emitting diodes (OLEDs) have been successfully introduced to the smartphone display market and have geared up to become contenders for applications in general illumination where they promise to combine efficient generation of white light with excellent color quality, glare-free illumination, and highly attractive designs. Device efficiency is the key requirement for such white OLEDs, not only from a sustainability perspective, but also because at the high brightness required for general illumination, losses lead to heating and may, thus, cause rapid device degradation. The efficiency of white OLEDs increased tremendously over the past two decades, and internal charge-to-photon conversion can now be achieved at ˜100% yield. However, the extraction of photons remains rather inefficient (typically physics of outcoupling in white OLEDs and review recent progress toward making light extraction more efficient. We describe how structures that scatter, refract, or diffract light can be attached to the outside of white OLEDs (external outcoupling) or can be integrated close to the active layers of the device (internal outcoupling). Moreover, the prospects of using top-emitting metal-metal microcavity designs for white OLEDs and of tuning the average orientation of the emissive molecules within the OLED are discussed.

  17. Rectangular illumination using a secondary optics with cylindrical lens for LED street light.

    Science.gov (United States)

    Chen, Hsi-Chao; Lin, Jun-Yu; Chiu, Hsuan-Yi

    2013-02-11

    The illumination pattern of an LED street light is required to have a rectangular distribution at a divergence-angle ratio of 7:3 for economical illumination. Hence, research supplying a secondary optics with two cylindrical lenses was different from free-form curvature for rectangular illumination. The analytical solution for curvatures with different ratio rectangles solved this detail by light tracing and boundary conditions. Similarities between the experiments and the simulation for a single LED and a 9-LED module were analyzed by Normalized Cross Correlation (NCC), and the error rate was studied by the Root Mean Square (RMS). The tolerance of position must be kept under ± 0.2 mm in the x, y and z directions to ensure that the relative illumination is over 99%.

  18. Intrinsic white-light emission from layered hybrid perovskites.

    Science.gov (United States)

    Dohner, Emma R; Jaffe, Adam; Bradshaw, Liam R; Karunadasa, Hemamala I

    2014-09-24

    We report on the second family of layered perovskite white-light emitters with improved photoluminescence quantum efficiencies (PLQEs). Upon near-ultraviolet excitation, two new Pb-Cl and Pb-Br perovskites emit broadband "cold" and "warm" white light, respectively, with high color rendition. Emission from large, single crystals indicates an origin from the bulk material and not surface defect sites. The Pb-Br perovskite has a PLQE of 9%, which is undiminished after 3 months of continuous irradiation. Our mechanistic studies indicate that the emission has contributions from strong electron-phonon coupling in a deformable lattice and from a distribution of intrinsic trap states. These hybrids provide a tunable platform for combining the facile processability of organic materials with the structural definition of crystalline, inorganic solids.

  19. USER EVALUATION OF EIGHT LED LIGHT SOURCES WITH DIFFERENTSPECIAL COLOUR RENDERING INDICES R9

    DEFF Research Database (Denmark)

    Markvart, Jakob; Iversen, Anne; Logadóttir, Ásta

    2013-01-01

    In this study we evaluated the influence of the special colour rendering index R9 on subjective red colour perception and Caucasian skin appearance among untrained test subjects. The light sources tested are commercially available LED based light sources with similar correlated colour temperature...... and general colour rendering index, but with varying R9. It was found that the test subjects in general are more positive towards light sources with higher R9. The shift from a majority of negative responses to a majority of positive responses is found to occur at R9 values of ~20....

  20. Study of LED layout in indoor visible light communication and performance analysis

    Science.gov (United States)

    Wang, Jiaan; Che, Ying; Wang, Xinlan; Guo, Linyang; Li, Jing

    2017-10-01

    Light emitting diodes(LED) could provide both illumination and data communication in indoor visible light communication(VLC) that owns the modulation bandwith from several from several MHz to seneral hundreds of MHz. The layout of LED plays an important role in maintaining a steady optical power distribution over the receiving plane. The existing rectangular LED layout does not provide a full coverage on the receiving plane leaving receiving optical power outage area, which in turn affects the best performance of the VLC system. This paper design a circular layout scheme of LED in 5mX5mX3m room based on the criterion of the illumination minimum mean square deviation. The influence of the distribution of the intensity of illumination with the radius of 1m and 1.5m,for including the wall reflection and not including the wall reflection, and make a comparison with rectangular LED layout of illumination distribution, when the number of LEDs with rectangular layout as same as circular layout. Including the number of LEDs are 4 and 16.For a specific simulation parameters as following:height of receiving plane is 0.85m,a single LEDs is composed of 60X60 LED chips, the parameters of a single chip is that transmitting power is 20mW,center luminous intensity is 0.73cd.semiangle at half power is 70deg.The parameters of concentrator is that photodiode area is 1cm2,photodiode responsivity is 0.4,field of view at the receiver is 85deg.Other parameters are that reflective index of concentrator is 1.5,reflectivity of wall is 0.8.Circular layout and rectangular layout are analyzed through simulation of the received optical power distribution, signal noise ratio distribution in non line of sight(including the wall reflection) and line of sight(not including the wall reflection),when the number of the LED is different. It is clear from the results that the received optical power distribution of non line of sight is better than line of sight, when the number of the LED are same, but

  1. Demonstration of 575-Mb/s downlink and 225-Mb/s uplink bi-directional SCM-WDM visible light communication using RGB LED and phosphor-based LED.

    Science.gov (United States)

    Wang, Yuanquan; Wang, Yiguang; Chi, Nan; Yu, Jianjun; Shang, Huiliang

    2013-01-14

    We propose and experimentally demonstrate a novel full-duplex bi-directional subcarrier multiplexing (SCM)-wavelength division multiplexing (WDM) visible light communication (VLC) system based on commercially available red-green-blue (RGB) light emitting diode (LED) and phosphor-based LED (P-LED) with 575-Mb/s downstream and 225-Mb/s upstream transmission, employing various modulation orders of quadrature amplitude modulation (QAM) orthogonal frequency division multiplexing (OFDM). For the downlink, red and green colors/wavelengths are assigned to carry useful information, while blue chip is just kept lighting to maintain the white color illumination, and for the uplink, the low-cost P-LED is implemented. In this demonstration, pre-equalization and post-equalization are also adopted to compensate the severe frequency response of LEDs. Using this scheme, 4-user downlink and 1-user uplink transmission can be achieved. Furthermore, it can support more users by adjusting the bandwidth of each sub-channel. Bit error rates (BERs) of all links are below pre-forward-error-correction (pre-FEC) threshold of 3.8x 10(-3) after 66-cm free-space delivery. The results show that this scheme has great potential in the practical VLC system.

  2. Signal-to-noise limitations in white light holography.

    Science.gov (United States)

    Ribak, E; Roddier, C; Roddier, F; Breckinridge, J B

    1988-03-15

    A simple derivation is given for the signal-to-noise ratio (SNR) in images reconstructed from incoherent holograms. Dependence is shown to be on the hologram SNR, object complexity, and the number of pixels in the detector. Reconstruction of involved objects becomes possible with high dynamic range detectors such as charge coupled devices. We have produced such white light holograms by means of a rotational shear interferometer combined with a chromatic corrector. A digital inverse transform recreated the object.

  3. Signal-to-noise limitations in white light holography

    Science.gov (United States)

    Ribak, Erez; Breckinridge, James B.; Roddier, Claude; Roddier, Francois

    1988-01-01

    A simple derivation is given for the SNR in images reconstructed from incoherent holograms. Dependence is shown to be on the hologram SNR, object complexity, and the number of pixels in the detector. Reconstruction of involved objects becomes possible with high-dynamic-range detectors such as CCDs. White-light holograms have been produced by means of a rotational shear interferometer combined with a chromatic corrector. A digital inverse transform recreated the object.

  4. DC Grids for Smart LED-Based Lighting: The EDISON Solution

    Directory of Open Access Journals (Sweden)

    Steffen Thielemans

    2017-09-01

    Full Text Available This paper highlights the benefits and possible drawbacks of a DC-based lighting infrastructure for powering Light Emitting Diode (LED-lamps. It also evaluates the efforts needed for integrating the so called smart lighting and other sensor/actuator based control systems, and compares existing and emerging solutions. It reviews and discusses published work in this field with special focus on the intelligent DC-based infrastructure named EDISON that is primarily dedicated to lighting, but is applicable to building automation in general. The EDISON “PowerLAN” consists of a DC-based infrastructure that offers telecommunication abilities and can be applied to lighting retrofitting scenarios for buildings. Its infrastructure allows simple and efficient powering of DC-oriented devices like LED lamps, sensors and microcontrollers, while offering a wired communication channel. This paper motivates the design choices for organizing DC lighting grids and their associated communication possibilities. It also shows how the EDISON based smart lighting solution is evolving today to include new communication technologies and to further integrate other parts of building management solutions through the OneM2M (Machine to Machine service bus.

  5. An organic white light-emitting dye: very small molecular architecture displays panchromatic emission.

    Science.gov (United States)

    Nandhikonda, Premchendar; Heagy, Michael D

    2010-11-14

    The synthesis and photophysical characterization of a new white-light fluorophore is described. The optimization of excitation wavelengths allows the naphthalimide (NI) dyes to display blue, green or white light emission depending on the excitation wavelength.

  6. Performance of the mixed LED light quality on the growth and energy efficiency of Arthrospira platensis.

    Science.gov (United States)

    Mao, Ruixin; Guo, Shuangsheng

    2018-06-01

    The effect of mixed light quality with red, blue, and green LED lamps on the growth of Arthrospira platensis was studied, so as to lay the theoretical and technical basis for establishing a photo-bioreactor lighting system for application in space. Meanwhile, indexes, like morphology, growth rate, photosynthetic pigment compositions, energy efficiency, and main nutritional components, were measured respectively. The results showed that the blue light combined with red light could decrease the tightness of filament, and the effect of green light was opposite. The combination of blue light or green light with red light induced the filaments to get shorter in length. The 8R2B treatment could promote the growth of Arthrospira platensis significantly, and its dry weight reached 1.36 g L -1 , which was 25.93% higher than the control. What's more, 8R2B treatment had the highest contents of carbohydrate and lipid, while 8R2G was rich in protein. 8R0.5G1.5B had the highest efficiency of biomass production, which was 161.53 mg L -1  kW -1  h -1 . Therefore, the combination of red and blue light is more conducive to the growth of Arthrospira platensis, and a higher biomass production and energy utilization efficiency can be achieved simultaneously under the mixed light quality with the ratio of 8R0.5G1.5B.

  7. Testing a high-power LED based light source for hyperspectral imaging microscopy

    Science.gov (United States)

    Klomkaew, Phiwat; Mayes, Sam A.; Rich, Thomas C.; Leavesley, Silas J.

    2017-02-01

    Our lab has worked to develop high-speed hyperspectral imaging systems that scan the fluorescence excitation spectrum for biomedical imaging applications. Hyperspectral imaging can be used in remote sensing, medical imaging, reaction analysis, and other applications. Here, we describe the development of a hyperspectral imaging system that comprised an inverted Nikon Eclipse microscope, sCMOS camera, and a custom light source that utilized a series of high-power LEDs. LED selection was performed to achieve wavelengths of 350-590 nm. To reduce scattering, LEDs with low viewing angles were selected. LEDs were surface-mount soldered and powered by an RCD. We utilized 3D printed mounting brackets to assemble all circuit components. Spectraradiometric calibration was performed using a spectrometer (QE65000, Ocean Optics) and integrating sphere (FOIS-1, Ocean Optics). Optical output and LED driving current were measured over a range of illumination intensities. A normalization algorithm was used to calibrate and optimize the intensity of the light source. The highest illumination power was at 375 nm (3300 mW/cm2), while the lowest illumination power was at 515, 525, and 590 nm (5200 mW/cm2). Comparing the intensities supplied by each LED to the intensities measured at the microscope stage, we found there was a great loss in power output. Future work will focus on using two of the same LEDs to double the power and finding more LED and/or laser diodes and chips around the range. This custom hyperspectral imaging system could be used for the detection of cancer and the identification of biomolecules.

  8. Considerable photoluminescence enhancement of LiEu(MoO4)2 red phosphors via Bi and/or Si doping for white LEDs

    International Nuclear Information System (INIS)

    Wang, Qing-Feng; Liu, Ying; Wang, Yu; Wang, Wenxi; Wan, Yi; Wang, Gui-Gen; Lu, Zhou-Guang

    2015-01-01

    Graphical abstract: Doping of Bi and Si into the lattice leads to an considerable increase of the excitation efficiency and luminous intensity, and obvious movement of the CIE chromaticity coordinates to the NTSC standard values of the LiEu(MoO 4 ) 2 , a promising red phosphors suitable for near UV excited white-light emitting diodes. - Highlights: • High performance red phosphors for near UV light excited white LEDs. • Lithium lanthanide molybdate red phosphors. • Bi and Si substitution. • Considerable enhancement of luminescence intensity and excitation efficiency. • CIE chromaticity coordinates very close to the NTSC standard values. - Abstract: Novel Bi and/or Si substituted LiEu(MoO 4 ) 2 phosphors, where Bi was used as sensitizer to enhance the emission intensity and Si was used as substitution to improve the excitation efficiency, were prepared using the sol–gel method, and the photoluminescent properties of the resulting phosphors were intensively investigated. All samples can be excited efficiently by UV (395 nm) light and emit bright red light at 614 nm, which are coupled well with the characteristic emission from a UV-LED. In the Bi 3+ -doped samples, the intensities of the main emission line ( 5 D 0 – 7 F 2 transition at 614 nm) are strengthened because of the energy transition from Bi 3+ to Eu 3+ . With the substitution of Mo 4+ by Si 4+ , there are no significant changes in the emission peak positions, but the emission intensity was significantly enhanced under 395 nm excitation. Particularly, the LiEu 0.9 Bi 0.1 (Mo 0.97 Si 0.03 O 4 ) 2 phosphor doped with both Bi and Si demonstrates superior comprehensive photoluminescence properties with an excellent combination of easy excitation in the near UV range, bright emission intensity, high PL quantum efficiency as well as suitable decay time, which are very suitable for application as red phosphor for near UV type LEDs

  9. A design of LED adaptive dimming lighting system based on incremental PID controller

    Science.gov (United States)

    He, Xiangyan; Xiao, Zexin; He, Shaojia

    2010-11-01

    As a new generation energy-saving lighting source, LED is applied widely in various technology and industry fields. The requirement of its adaptive lighting technology is more and more rigorous, especially in the automatic on-line detecting system. In this paper, a closed loop feedback LED adaptive dimming lighting system based on incremental PID controller is designed, which consists of MEGA16 chip as a Micro-controller Unit (MCU), the ambient light sensor BH1750 chip with Inter-Integrated Circuit (I2C), and constant-current driving circuit. A given value of light intensity required for the on-line detecting environment need to be saved to the register of MCU. The optical intensity, detected by BH1750 chip in real time, is converted to digital signal by AD converter of the BH1750 chip, and then transmitted to MEGA16 chip through I2C serial bus. Since the variation law of light intensity in the on-line detecting environment is usually not easy to be established, incremental Proportional-Integral-Differential (PID) algorithm is applied in this system. Control variable obtained by the incremental PID determines duty cycle of Pulse-Width Modulation (PWM). Consequently, LED's forward current is adjusted by PWM, and the luminous intensity of the detection environment is stabilized by self-adaptation. The coefficients of incremental PID are obtained respectively after experiments. Compared with the traditional LED dimming system, it has advantages of anti-interference, simple construction, fast response, and high stability by the use of incremental PID algorithm and BH1750 chip with I2C serial bus. Therefore, it is suitable for the adaptive on-line detecting applications.

  10. A new LED lamp for the collection of nocturnal Lepidoptera and a spectral comparison of light-trapping lamps

    Directory of Open Access Journals (Sweden)

    Gunnar Brehm

    2017-04-01

    Full Text Available Most nocturnal Lepidoptera can be attracted to artificial light sources, particularly to those that emit a high proportion of ultraviolet radiation. Here, I describe a newly developed LED lamp set for the use in the field that is lightweight, handy, robust, and energy efficient. The emitted electromagnetic spectrum corresponds to the peak sensitivity in most Lepidoptera eye receptors (ultraviolet, blue and green. Power LEDs with peaks at 368 nm (ultraviolet, 450 nm (blue, 530 nm (green, and 550 nm (cool white are used. I compared the irradiance (Ee of many commonly used light-trapping lamps at a distance of 50 cm. Between wavelengths of 300 and 1000 nm, irradiance from the new lamp was 1.43 W m-2. The new lamp proved to be the most energy efficient, and it emitted more radiation in the range between 300 and 400 nm than any other lamp tested. Cold cathodes are the second most energy-efficient lamps. Irradiation from fluorescent actinic tubes is higher than from fluorescent blacklight-blue tubes. High-wattage incandescent lamps and self-ballasted mercury vapour lamps have highest irradiance, but they mainly emit in the long wave spectrum. The use of gauze and sheets decreases the proportion of UV radiation and increases the share of blue light, probably due to optical brighteners. Compared with sunlight, UV irradiance is low at a distance of 50 cm from the lamp, but (safety glasses as well as keeping sufficient distance from the lamp are recommended. In field tests, the new LED lamp attracted large numbers of Lepidoptera in both the Italian Alps and in the Peruvian Andes.

  11. Time Effectiveness of Ultraviolet C Light (UVC Emitted by Light Emitting Diodes (LEDs in Reducing Stethoscope Contamination

    Directory of Open Access Journals (Sweden)

    Gabriele Messina

    2016-09-01

    Full Text Available Today it is well demonstrated that stethoscopes can be as contaminated as hands, which are a recognized source of Health-Care Associated Infections (HCAIs. Ultraviolet C (UVC light has proven disinfection capacity and the innovative UVC technology of Light Emitting Diode (LED shows several potential benefits. To verify whether the use of UVC LEDs is effective and reliable in stethoscope membrane disinfection after prolonged use, a pre-post intervention study was conducted. A total of 1668 five-minute cycles were performed on two UVC LEDs to simulate their use; thereafter, their disinfection capacity was tested on stethoscope membranes used on a previously auscultated volunteer. Then, a further 1249 cycles were run and finally the LEDs were tested to assess performance in reducing experimental contamination by Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli on the stethoscope membrane. Baseline volunteer contamination identified 104 Colony Forming Units (CFUs while treated Petri dishes had 12 and 15 CFUs (p < 0.001. Statistically significant differences (p < 0.001 were also found relating to the reduction of specific bacteria: in particular, after treatment no CFU were observed for S. aureus and E. coli. UVC LEDs demonstrated the capacity to maintain high levels of disinfection after more than 240 h of use and they were effective against common microorganisms that are causative agents of HCAIs.

  12. Time Effectiveness of Ultraviolet C Light (UVC) Emitted by Light Emitting Diodes (LEDs) in Reducing Stethoscope Contamination.

    Science.gov (United States)

    Messina, Gabriele; Fattorini, Mattia; Nante, Nicola; Rosadini, Daniele; Serafini, Andrea; Tani, Marco; Cevenini, Gabriele

    2016-09-23

    Today it is well demonstrated that stethoscopes can be as contaminated as hands, which are a recognized source of Health-Care Associated Infections (HCAIs). Ultraviolet C (UVC) light has proven disinfection capacity and the innovative UVC technology of Light Emitting Diode (LED) shows several potential benefits. To verify whether the use of UVC LEDs is effective and reliable in stethoscope membrane disinfection after prolonged use, a pre-post intervention study was conducted. A total of 1668 five-minute cycles were performed on two UVC LEDs to simulate their use; thereafter, their disinfection capacity was tested on stethoscope membranes used on a previously auscultated volunteer. Then, a further 1249 cycles were run and finally the LEDs were tested to assess performance in reducing experimental contamination by Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli on the stethoscope membrane. Baseline volunteer contamination identified 104 Colony Forming Units (CFUs) while treated Petri dishes had 12 and 15 CFUs (p < 0.001). Statistically significant differences (p < 0.001) were also found relating to the reduction of specific bacteria: in particular, after treatment no CFU were observed for S. aureus and E. coli. UVC LEDs demonstrated the capacity to maintain high levels of disinfection after more than 240 h of use and they were effective against common microorganisms that are causative agents of HCAIs.

  13. PV LED ENGINE characterization lab for stand alone light-to-light systems

    DEFF Research Database (Denmark)

    Poulsen, Peter Behrensdorff; Thorsteinsson, Sune; Lindén, Johannes

    2015-01-01

    dimming functions for reliable lighting. A barrier for exploiting use of standalone solar lighting for the urban environment seem to be lack of knowledge and lack of available tools for proper dimensioning. In this work the development of powerful dimensioning tool is described and initial measurements...... are presented. Furthermore, a laboratory has been build to characterize these systems up to 200 Wp from “nose to tail” in great details to support improvement of the systems and to make accurate field performance predictions by the dimensioning tool....

  14. White light Sagnac interferometer—a common (path) tale of light

    Science.gov (United States)

    Schwartz, Eyal

    2017-11-01

    White or polychromatic light sources are vastly abundant in nature and lie in our most basic understanding of the theory of light, beginning from stars like our Sun and extending to every common household light bulb or street lamp. In this paper, I present concepts of white light interferometery using a common-path Sagnac interferometer, manifested in a straightforward laboratory experiment. I further show the use of this as a Fourier transform spectrometer while presenting a basic overview of the theoretical concepts and spectrum of different light sources obtained experimentally. This work, both experimentally and analytically, is suitable for upper-level undergraduate physics or engineering courses where electromagnetic theory and optics are discussed. The experiment and theory presents important deep concepts and aspects in modern optics and physics that every science student should acquire.

  15. White light Sagnac interferometer—a common (path) tale of light

    International Nuclear Information System (INIS)

    Schwartz, Eyal

    2017-01-01

    White or polychromatic light sources are vastly abundant in nature and lie in our most basic understanding of the theory of light, beginning from stars like our Sun and extending to every common household light bulb or street lamp. In this paper, I present concepts of white light interferometery using a common-path Sagnac interferometer, manifested in a straightforward laboratory experiment. I further show the use of this as a Fourier transform spectrometer while presenting a basic overview of the theoretical concepts and spectrum of different light sources obtained experimentally. This work, both experimentally and analytically, is suitable for upper-level undergraduate physics or engineering courses where electromagnetic theory and optics are discussed. The experiment and theory presents important deep concepts and aspects in modern optics and physics that every science student should acquire. (paper)

  16. Tapering-induced enhancement of light extraction efficiency of nanowire deep ultraviolet LED by theoretical simulations

    KAUST Repository

    Lin, Ronghui; Galan, Sergio Valdes; Sun, Haiding; Hu, Yangrui; Alias, Mohd Sharizal; Janjua, Bilal; Ng, Tien Khee; Ooi, Boon S.; Li, Xiaohang

    2018-01-01

    A nanowire (NW) structure provides an alternative scheme for deep ultraviolet light emitting diodes (DUV-LEDs) that promises high material quality and better light extraction efficiency (LEE). In this report, we investigate the influence of the tapering angle of closely packed AlGaN NWs, which is found to exist naturally in molecular beam epitaxy (MBE) grown NW structures, on the LEE of NW DUV-LEDs. It is observed that, by having a small tapering angle, the vertical extraction is greatly enhanced for both transverse magnetic (TM) and transverse electric (TE) polarizations. Most notably, the vertical extraction of TM emission increased from 4.8% to 24.3%, which makes the LEE reasonably large to achieve high-performance DUV-LEDs. This is because the breaking of symmetry in the vertical direction changes the propagation of the light significantly to allow more coupling into radiation modes. Finally, we introduce errors to the NW positions to show the advantages of the tapered NW structures can be projected to random closely packed NW arrays. The results obtained in this paper can provide guidelines for designing efficient NW DUV-LEDs.

  17. Tapering-induced enhancement of light extraction efficiency of nanowire deep ultraviolet LED by theoretical simulations

    KAUST Repository

    Lin, Ronghui

    2018-04-21

    A nanowire (NW) structure provides an alternative scheme for deep ultraviolet light emitting diodes (DUV-LEDs) that promises high material quality and better light extraction efficiency (LEE). In this report, we investigate the influence of the tapering angle of closely packed AlGaN NWs, which is found to exist naturally in molecular beam epitaxy (MBE) grown NW structures, on the LEE of NW DUV-LEDs. It is observed that, by having a small tapering angle, the vertical extraction is greatly enhanced for both transverse magnetic (TM) and transverse electric (TE) polarizations. Most notably, the vertical extraction of TM emission increased from 4.8% to 24.3%, which makes the LEE reasonably large to achieve high-performance DUV-LEDs. This is because the breaking of symmetry in the vertical direction changes the propagation of the light significantly to allow more coupling into radiation modes. Finally, we introduce errors to the NW positions to show the advantages of the tapered NW structures can be projected to random closely packed NW arrays. The results obtained in this paper can provide guidelines for designing efficient NW DUV-LEDs.

  18. Red light emitting solid state hybrid quantum dot-near-UV GaN LED devices

    International Nuclear Information System (INIS)

    Song, Hongjoo; Lee, Seonghoon

    2007-01-01

    We produced core-shell (CdSe)ZnSe quantum dots by direct colloidal chemical synthesis and the surface-passivation method-an overcoating of the core CdSe with a larger-bandgap material ZnSe. The (CdSe)ZnSe quantum dots(QDs) play the role of a colour conversion centre. We call these quantum dots nanophosphors. We fabricated red light emitting hybrid devices of (CdSe)ZnSe QDs and a near-UV GaN LED by combining red light emitting (CdSe)ZnSe quantum dots (as a colour conversion centre) with a near-UV(NUV) GaN LED chip (as an excitation source). A few good red phosphors have been known for UV excitation wavelengths, and red phosphors for UV excitation have been sought for a long time. Here we tested the possibility of using (CdSe)ZnSe QDs as red nanophosphors for UV excitation. The fabricated red light emitting hybrid device of (CdSe)ZnSe and a NUV GaN LED chip showed a good luminance. We demonstrated that the (CdSe)ZnSe quantum dots were promising red nanophosphors for NUV excitation and that a red LED made of QDs and a NUV excitation source was a highly efficient hybrid device

  19. Synthesis and optical properties of red/blue-emitting Sr2MgSi2O7:Eu3+/Eu2+ phosphors for white LED

    Directory of Open Access Journals (Sweden)

    Tong Thi Hao Tam

    2016-06-01

    Full Text Available Phosphor-converted white light emitting diodes (white LEDs have received great attention in recent years since they have several excellent features such as high lumen output, low power consumption, long lifetime and environmentally friendly. In this work, we report the co-precipitation synthesis of red/blue Sr2MgSi2O7:Eu3+/Eu2+ phosphors with various Eu doping concentration. The results show that the obtained Sr2MgSi2O7:Eu3+/Eu2+ phosphors have good crystallinity and emit strong red (Sr2MgSi2O7:Eu3+ and blue (Sr2MgSi2O7:Eu2+ emissions under near UV light excitation. The sharp emission peaks at 577, 590, 612, 653, and 701 nm corresponded to the typical 5D0 → 7Fj (j = 0,1,2,3,4 transitions of Eu3+, and the blue emission peaking at 460 nm is attributed to the typical 4f65d1-4f7 transition of Eu2+ in the same Sr2MgSi2O7 host lattice. Both phosphors can be well excited in the wavelength range of 260–400 nm where the near UV-LED is well matched. The above results suggest that the Sr2MgSi2O7:Eu3+/Eu2+ phosphors are promising red/blue-emitting phosphors for the application in near UV pumped phosphor-converted white LEDs.

  20. A Simple, Small-Scale Lego Colorimeter with a Light-Emitting Diode (LED) Used as Detector

    Science.gov (United States)

    Asheim, Jonas; Kvittingen, Eivind V.; Kvittingen, Lise; Verley, Richard

    2014-01-01

    This article describes how to construct a simple, inexpensive, and robust colorimeter from a few Lego bricks, in which one light-emitting diode (LED) is used as a light source and a second LED as a light detector. The colorimeter is suited to various grades and curricula.

  1. First demonstration of 'white-light' laser cooling of a stored ion beam

    International Nuclear Information System (INIS)

    Atutov, S.N.; Biancalana, V.; Calabrese, R.; Clauser, T.; Grimm, R.; Guidi, V.; Lamanna, G.; Lauer, I.; Lenisa, P.; Luger, V.; Mariotti, E.; Moi, L.; Schramm, U.; Stagno, V.; Stoessel, M.; Tecchio, L.; Variale, V.

    1998-01-01

    'White-light' cooling of an ion beam confined in a storage ring has been demonstrated at Test Storage Ring in Heidelberg. Measurements aimed at comparing 'white-light' with single-mode laser cooling show that 'white-light' cooling gives lower temperatures at higher ion densities both in a coasting and in a bunched beam

  2. The study of LED light source illumination conditions for ideal algae cultivation

    Science.gov (United States)

    Tsai, Chun-Chin; Huang, Chien-Fu; Chen, Cin-Fu; Yue, Cheng-Feng

    2017-02-01

    Utilizing LED light source modules with 3 different RGB colors, the illumination effect of different wavelengths had been investigated on the growth curve of the same kind of micro algae. It was found that the best micro algae culturing status came out with long wavelength light such as red light (650 670 nm). Based on the same condition for a period of 3 weeks , the grown micro algae population density ratio represented by Optical Density (O.D.) ratio is 1?0.4?0.7 corresponding to growth with Red, Green, Blue light sources, respectively. Mixing 3 types and 2 types of LEDs with different parameters, the grown micro algae population densities were compared in terms of O.D. Interestingly enough, different light sources resulted in significant discoloration on micro algae growth, appearing yellow, brown, green, etc. Our experiments results showed such discoloration effect is reversible. Based on the same lighting condition, micro algae growth can be also affected by incubator size, nutrition supply, and temperature variation. In recent years, micro algae related technologies have been international wise a hot topic of energy and environmental protection for research and development institutes, and big energy companies among those developed countries. There will be an economically prosperous future. From this study of LED lighting to ideal algae cultivation, it was found that such built system would be capable of optimizing artificial cultivation system, leading to economic benefits for its continuous development. Since global warming causing weather change, accompanying with reducing energy sources and agriculture growth shortage are all threatening human being survival.

  3. Potential environmental impacts of light-emitting diodes (LEDs): metallic resources, toxicity, and hazardous waste classification.

    Science.gov (United States)

    Lim, Seong-Rin; Kang, Daniel; Ogunseitan, Oladele A; Schoenung, Julie M

    2011-01-01

    Light-emitting diodes (LEDs) are advertised as environmentally friendly because they are energy efficient and mercury-free. This study aimed to determine if LEDs engender other forms of environmental and human health impacts, and to characterize variation across different LEDs based on color and intensity. The objectives are as follows: (i) to use standardized leachability tests to examine whether LEDs are to be categorized as hazardous waste under existing United States federal and California state regulations; and (ii) to use material life cycle impact and hazard assessment methods to evaluate resource depletion and toxicity potentials of LEDs based on their metallic constituents. According to federal standards, LEDs are not hazardous except for low-intensity red LEDs, which leached Pb at levels exceeding regulatory limits (186 mg/L; regulatory limit: 5). However, according to California regulations, excessive levels of copper (up to 3892 mg/kg; limit: 2500), Pb (up to 8103 mg/kg; limit: 1000), nickel (up to 4797 mg/kg; limit: 2000), or silver (up to 721 mg/kg; limit: 500) render all except low-intensity yellow LEDs hazardous. The environmental burden associated with resource depletion potentials derives primarily from gold and silver, whereas the burden from toxicity potentials is associated primarily with arsenic, copper, nickel, lead, iron, and silver. Establishing benchmark levels of these substances can help manufacturers implement design for environment through informed materials substitution, can motivate recyclers and waste management teams to recognize resource value and occupational hazards, and can inform policymakers who establish waste management policies for LEDs.

  4. White light generation using CdSe/ZnS core-shell nanocrystals hybridized with InGaN/GaN light emitting diodes

    International Nuclear Information System (INIS)

    Nizamoglu, S; Ozel, T; Sari, E; Demir, H V

    2007-01-01

    We introduce white light generation using CdSe/ZnS core-shell nanocrystals of single, dual, triple and quadruple combinations hybridized with InGaN/GaN LEDs. Such hybridization of different nanocrystal combinations provides the ability to conveniently adjust white light parameters including the tristimulus coordinates (x,y), correlated colour temperature (T c ) and colour rending index (R a ). We present the design, growth, fabrication and characterization of our white hybrid nanocrystal-LEDs that incorporate combinations of (1) yellow nanocrystals (λ PL = 580 nm) on a blue LED (λ EL = 440 nm) with (x,y) = (0.37,0.25), T c = 2692 K and R a 14.69; (2) cyan and red nanocrystals (λ PL = 500 and 620 nm) on a blue LED (λ EL = 440 nm) with (x,y) = (0.37,0.28), T c = 3246 K and R a = 19.65; (3) green, yellow and red nanocrystals (λ PL = 540, 580 and 620 nm) on a blue LED (λ EL = 452 nm) with (x,y) = (0.30,0.28), T c = 7521 K and R a = 40.95; and (4) cyan, green, yellow and red nanocrystals (λ PL = 500, 540, 580 and 620 nm) on a blue LED (λ EL = 452 nm) with (x,y) = (0.24,0.33), T c = 11 171 K and R a 71.07. These hybrid white light sources hold promise for future lighting and display applications with their highly adjustable properties

  5. Energy-Saving Automation and LED Lighting Systems in Industry, Transport, Building and Municipal Sector

    Directory of Open Access Journals (Sweden)

    V.P. Klimenko

    2013-09-01

    Full Text Available Protocol of diverse technological data unification providing the ability to scale with a minimal increase in auxiliary information volume that allows its usage, ranging from the simplest microcontrollers to integration of automation equipment in global systems was designed for industrial automation systems. Basic technical solutions implemented in development of LED lighting systems of salon subway cars, including a schematic diagram of the lamp, the main technical characteristics of the lamp power supply, the peculiarities of developed design of LED modules are described.

  6. Technology Analysis of Global Smart Light Emitting Diode (LED Development Using Patent Data

    Directory of Open Access Journals (Sweden)

    Sangsung Park

    2017-08-01

    Full Text Available Technological developments related to smart light emitting diode (LED systems have progressed rapidly in recent years. In this paper, patent documents related to smart LED technology are collected and analyzed to understand the technology development of smart LED systems. Most previous studies of the technology were dependent on the knowledge and experience of domain experts, using techniques such as Delphi surveys or technology road-mapping. These approaches may be subjective and lack robustness, because the results can vary according to the selected expert groups. We therefore propose a new technology analysis methodology based on statistical modeling to obtain objective and relatively stable results. The proposed method consists of visualization based on Bayesian networks and a linear count model to analyze patent documents related to smart LED technology. Combining these results, a global hierarchical technology structure is created that can enhance the sustainability in smart LED system technology. In order to show how this methodology could be applied to real-world problems, we carry out a case study on the technology analysis of smart LED systems.

  7. Mercury in canned tuna: white versus light and temporal variation

    International Nuclear Information System (INIS)

    Burger, Joanna; Gochfeld, Michael

    2004-01-01

    There are abundant data and advisories for mercury levels in wild fish, but far fewer for commercial fish that compose a large majority of the fish most people eat. Until recently, relatively little attention has been devoted to examining mercury in canned tuna, despite its great importance in human diets. There is substantial media coverage of the benefits and risk from fish consumption, but few peer-reviewed data on canned tuna, the most commonly consumed fish in the United States. In this paper, we examine the levels of total mercury in canned tuna obtained from a New Jersey grocery store from 1998 to 2003, looking for temporal consistency within this data set and particularly for comparison with the Food and Drug Administration's 1991 study. We analyzed 168 cans individually for total mercury. All values are reported as parts per million (=μg/g) on a wet weight basis. In a subset of samples analyzed for total and inorganic mercury, the inorganic mercury was below detection levels; hence at least 89% of the mercury can be considered methylmercury. We found that white-style tuna had significantly more total mercury (mean 0.407 ppm) than light-style tuna (mean 0.118 ppm), presumably reflecting that 'white' tuna is albacore, a species relatively larger than the skipjack tuna, which is commonly available as 'light' or 'chunk light'. The maximum mercury in a can was 0.997 ppm, but 25% of white tuna samples exceeded 0.5 ppm. Data suggest a slight increase in levels since 1991, and mercury levels were significantly higher in 2001 than in other years. The mean level of mercury in white tuna (mean 0.407 ppm) was significantly higher than the mean value of 0.17 ppm currently used by the U.S. Food and Drug Administration (FDA) in its risk assessment and public information. There were no significant differences in mercury levels in tuna packed in oil compared to water. Draining contents had no effect on mercury levels, and the fluid, both oil and water, contained little

  8. Efficient white organic light emission by single emitting layer

    Energy Technology Data Exchange (ETDEWEB)

    Ko, Young Wook; Chung, Choong-Heui; Lee, Jin Ho; Kim, Yong-Hae; Sohn, Choong-Yong; Kim, Bong-Chul; Hwang, Chi-Sun; Song, Yoon-Ho; Lim, Jongtae; Ahn, Young-Joo; Kang, Gi-Wook; Lee, Namheon; Lee, Changhee

    2003-02-24

    Stable organic white light-emitting diodes are successfully fabricated by a single organic white emitting layer, which is Bis (2-methyl-8-quinolinato) (triphenylsiloxy) aluminum (III) (SAlq) doped red fluorescent dye of 4-(dicyanomethylene)-2-tert-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)- 4H-pyran (DCJTB). The incomplete energy transfer from blue-emitting SAlq to red-emitting DCJTB enables to obtain a stable white balanced light-emission by the DCJTB doping concentration of 0.5%. A device with the structure of ITO/TPD (50 nm)/SAlq:DCJTB (30 nm, 0.5%)/Alq{sub 3} (20 nm)/LiF (0.5 nm)/Al (110 nm) shows maximum luminance of 20 400 cd/m{sup 2} at 810 mA/cm{sup 2}, external quantum efficiency of 2% at 200 cd/m{sup 2} ({approx}3 mA/cm{sup 2}), power efficiency of 2.3 lm/W at 67 cd/m{sup 2} ({approx}1 mA/cm{sup 2}), and a Commission Internationale de l'Eclairage chromaticity coordinates of (0.34, 0.39) at 1.8 mA/cm{sup 2} to (0.31, 0.38) at 36 mA/cm{sup 2}.

  9. The influence of LED lighting on task accuracy: time of day, gender and myopia effects

    Science.gov (United States)

    Rao, Feng; Chan, A. H. S.; Zhu, Xi-Fang

    2017-07-01

    In this research, task errors were obtained during performance of a marker location task in which the markers were shown on a computer screen under nine LED lighting conditions; three illuminances (100, 300 and 500 lx) and three color temperatures (3000, 4500 and 6500 K). A total of 47 students participated voluntarily in these tasks. The results showed that task errors in the morning were small and nearly constant across the nine lighting conditions. However in the afternoon, the task errors were significantly larger and varied across lighting conditions. The largest errors for the afternoon session occurred when the color temperature was 4500 K and illuminance 500 lx. There were significant differences between task errors in the morning and afternoon sessions. No significant difference between females and males was found. Task errors for high myopia students were significantly larger than for the low myopia students under the same lighting conditions. In summary, the influence of LED lighting on task accuracy during office hours was not gender dependent, but was time of day and myopia dependent.

  10. An Investigation of LED Street Lighting's Impact on Sky Glow

    Energy Technology Data Exchange (ETDEWEB)

    Kinzey, Bruce R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Perrin, Tess E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Miller, Naomi J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Kocifaj, Miroslav [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Aube, Martin [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lamphar, Hector A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2017-04-25

    A significant amount of public attention has recently focused on perceived impacts of converting street lighting from incumbent lamp-based products to LED technology. Much of this attention pertains to the higher content of short wavelength light (commonly referred to as "blue light") of LEDs and its attendant influences on sky glow (a brightening of the night sky that can interfere with astronomical observation and may be associated with a host of other issues). The complexity of this topic leads to common misunderstandings and misperceptions among the public, and for this reason the U.S. Department of Energy Solid-State Lighting Program embarked on a study of sky glow using a well-established astronomical model to investigate some of the primary factors influencing sky glow. This report details the results of the investigation and attempts to present those results in terms accessible to the general lighting community. The report also strives to put the results into a larger context, and help educate interested readers on various topics relevant to the issues being discussed.

  11. GATEWAY Report Brief: Evaluating Tunable LED Lighting in the Swedish Medical Behavioral Health Unit

    Energy Technology Data Exchange (ETDEWEB)

    None, None

    2017-08-23

    Summary of a GATEWAY report evaluation of a tunable LED lighting system installed in the new Swedish Medical Behavioral Health Unit in Seattle that incorporates color-tunable luminaires in common areas, and uses advanced controls for dimming and color tuning, with the goal of providing a better environment for staff and patients. The report reviews the design of the tunable lighting system, summarizes two sets of measurements, and discusses the circadian, energy, and commissioning implications as well as lessons learned from the project.

  12. LED arrays as cost effective and efficient light sources for widefield microscopy.

    Directory of Open Access Journals (Sweden)

    Dinu F Albeanu

    Full Text Available New developments in fluorophores as well as in detection methods have fueled the rapid growth of optical imaging in the life sciences. Commercial widefield microscopes generally use arc lamps, excitation/emission filters and shutters for fluorescence imaging. These components can be expensive, difficult to maintain and preclude stable illumination. Here, we describe methods to construct inexpensive and easy-to-use light sources for optical microscopy using light-emitting diodes (LEDs. We also provide examples of its applicability to biological fluorescence imaging.

  13. Ca8NaY(PO4)6F2:Eu2+,Mn2+: a potential color-tunable phosphor for white LEDs applications

    International Nuclear Information System (INIS)

    Fen, Zhang; Wanjun, Tang

    2015-01-01

    Eu 2+ - and/or Mn 2+ -activated Ca 8 NaY(PO 4 ) 6 F 2 phosphors have been prepared via a combustion-assisted synthesis route. The powder X-ray diffraction measurement revealed that Ca 8 NaY(PO 4 ) 6 F 2 crystallized in a hexagonal crystal system with the space group P6 3 /m (176). The photoluminescence spectrum of the Eu 2+ single-doped phosphor shows a broad blue emission band peaking at 451 nm under the excitation of UV irradiation. The Eu 2+ -/Mn 2+ -codoped phosphors show a blue emission band and an orange emission band, and the corresponding CIE coordinates intuitively indicate the tunable colors from blue to yellow area. The energy transfer from the Eu 2+ to Mn 2+ ions is demonstrated to be a quadrupole-quadrupole mechanism in terms of the experimental results and analysis of PL spectra and decay curves of the phosphors. The developed phosphors can be efficiently excited in the UV region and exhibit a tunable white-light emission, making them attractive as single-component white-light-emitting conversion phosphors for UV-based white LEDs. (orig.)

  14. LED Lighting System Reliability Modeling and Inference via Random Effects Gamma Process and Copula Function

    Directory of Open Access Journals (Sweden)

    Huibing Hao

    2015-01-01

    Full Text Available Light emitting diode (LED lamp has attracted increasing interest in the field of lighting systems due to its low energy and long lifetime. For different functions (i.e., illumination and color, it may have two or more performance characteristics. When the multiple performance characteristics are dependent, it creates a challenging problem to accurately analyze the system reliability. In this paper, we assume that the system has two performance characteristics, and each performance characteristic is governed by a random effects Gamma process where the random effects can capture the unit to unit differences. The dependency of performance characteristics is described by a Frank copula function. Via the copula function, the reliability assessment model is proposed. Considering the model is so complicated and analytically intractable, the Markov chain Monte Carlo (MCMC method is used to estimate the unknown parameters. A numerical example about actual LED lamps data is given to demonstrate the usefulness and validity of the proposed model and method.

  15. Tuning the light in senior care: Evaluating a trial LED lighting system at the ACC Care Center in Sacramento, CA

    Energy Technology Data Exchange (ETDEWEB)

    Davis, Robert G.; Wilkerson, Andrea M.; Samla, Connie; Bisbee, Dave

    2016-08-31

    This report summarizes the results from a trial installation of light-emitting diode (LED) lighting systems in several spaces within the ACC Care Center in Sacramento, CA. The Sacramento Municipal Utility District (SMUD) coordinated the project and invited the U.S. Department of Energy (DOE) to document the performance of the LED lighting systems as part of a GATEWAY evaluation. DOE tasked the Pacific Northwest National Laboratory (PNNL) to conduct the investigation. SMUD and ACC staff coordinated and completed the design and installation of the LED systems, while PNNL and SMUD staff evaluated the photometric performance of the systems. ACC staff also track behavioral and health measures of the residents; some of those results are reported here, although PNNL staff were not directly involved in collecting or interpreting those data. The trial installation took place in a double resident room and a single resident room, and the corridor that connects those (and other) rooms to the central nurse station. Other spaces in the trial included the nurse station, a common room called the family room located near the nurse station, and the ACC administrator’s private office.

  16. Solid State pH Sensor Based on Light Emitting Diodes (LED As Detector Platform

    Directory of Open Access Journals (Sweden)

    Dermot Diamond

    2006-08-01

    Full Text Available A low-power, high sensitivity, very low-cost light emitting diode (LED-baseddevice developed for low-cost sensor networks was modified with bromocresol greenmembrane to work as a solid-state pH sensor. In this approach, a reverse-biased LEDfunctioning as a photodiode is coupled with a second LED configured in conventionalemission mode. A simple timer circuit measures how long (in microsecond it takes for thephotocurrent generated on the detector LED to discharge its capacitance from logic 1 ( 5 Vto logic 0 ( 1.7 V. The entire instrument provides an inherently digital output of lightintensity measurements for a few cents. A light dependent resistor (LDR modified withsimilar sensor membrane was also used as a comparison method. Both the LED sensor andthe LDR sensor responded to various pH buffer solutions in a similar way to obtainsigmoidal curves expected of the dye. The pKa value obtained for the sensors was found toagree with the literature value.

  17. The nanorod approach: GaN NanoLEDs for solid state lighting

    Energy Technology Data Exchange (ETDEWEB)

    Waag, Andreas; Wang, Xue; Fuendling, Soenke; Ledig, Johannes; Erenburg, Milena; Neumann, Richard; Al Suleiman, Mohamed; Merzsch, Stephan; Wei, Jiandong; Li, Shunfeng; Wehmann, Hergo H. [Institut fuer Halbleitertechnik, TU Braunschweig, Hans-Sommer-Strasse 66, 38106 Braunschweig (Germany); Bergbauer, Werner; Strassburg, Martin [OSRAM Opto Semiconductors GmbH, Leibnizstr. 4, 93055 Regensburg (Germany); Trampert, Achim; Jahn, Uwe; Riechert, Henning [Paul-Drude-Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany)

    2011-07-15

    Vertically aligned GaN nanorods have recently obtained substantial interest as a new approach to solid state lighting. In comparison to conventional planar LEDs, 3D NanoLEDs are expected to offer substantial advantageous: very low defect density, quasi free-standing, no strain due to mismatch of thermal expansion coefficients, no substrate bending even when grown on large area silicon. Core-shell strategies are another very interesting aspect. The active LED surface per wafer could be increased by more than one order of magnitude. However, most of these advantages have not yet been proven in real devices, which would include a quantitative comparison of light emission. Related to the 3D character, there are also technological risks. In the following we will discuss the main developments which have paved the way up to this point, including a detailed discussion of possible benefits and risks connected with the NanoLED approach (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. Color optimization of conjugated-polymer/InGaN hybrid white light emitting diodes by incomplete energy transfer

    International Nuclear Information System (INIS)

    Chang, Chi-Jung; Lai, Chun-Feng; Madhusudhana Reddy, P.; Chen, Yung-Lin; Chiou, Wei-Yung; Chang, Shinn-Jen

    2015-01-01

    By using the wavelength conversion method, white light emitting diodes (WLEDs) were produced by applying mixtures of polysiloxane and fluorescent polymers on InGaN based light emitting diodes. UV curable organic–inorganic hybrid materials with high refractive index (1.561), compromised optical, thermal and mechanical properties was used as encapsulants. Red light emitting fluorescent FABD polymer (with 9,9-dioctylfluorene (F), anthracene (A) and 2,1,3-benzothiadiazole (B), and 4,7-bis(2-thienyl)-2,1,3-benzothiadiazole (D) repeating units) and green light emitting fluorescent FAB polymer were used as wavelength converters. The encapsulant/fluorescent polymer mixture and InGaN produce the white light by incomplete energy transfer mechanism. WLEDs with high color rendering index (CRI, about 93), and tunable correlated color temperature (CCT) properties can be produced by controlling the composition and chemical structures of encapsulating polymer and fluorescent polymer in hybrid materials, offering cool-white and neutral-white LEDs. - Highlights: • Highly efficient white light-emitting diodes (WLEDs) were produced. • Conjugated-polymer/InGaN hybrid WLEDs by incomplete energy transfer mechanism. • WLEDs with high color-rendering index and tunable correlated color temperature. • Polysiloxane encapsulant with superior optical, mechanical and thermal properties

  19. Development and future of ultraviolet light-emitting diodes: UV-LED will replace the UV lamp

    Science.gov (United States)

    Muramoto, Yoshihiko; Kimura, Masahiro; Nouda, Suguru

    2014-06-01

    Ultraviolet light-emitting diodes (UV-LEDs) have started replacing UV lamps. The power per LED of high-power LED products has reached 12 W (14 A), which is 100 times the values observed ten years ago. In addition, the cost of these high-power LEDs has been decreasing. In this study, we attempt to understand the technologies and potential of UV-LEDs.

  20. Development and future of ultraviolet light-emitting diodes: UV-LED will replace the UV lamp

    International Nuclear Information System (INIS)

    Muramoto, Yoshihiko; Kimura, Masahiro; Nouda, Suguru

    2014-01-01

    Ultraviolet light-emitting diodes (UV-LEDs) have started replacing UV lamps. The power per LED of high-power LED products has reached 12 W (14 A), which is 100 times the values observed ten years ago. In addition, the cost of these high-power LEDs has been decreasing. In this study, we attempt to understand the technologies and potential of UV-LEDs. (invited article)

  1. Dy:Eu doped CaBAl glasses for white light applications

    Science.gov (United States)

    Lodi, T. A.; Sandrini, M.; Medina, A. N.; Barboza, M. J.; Pedrochi, F.; Steimacher, A.

    2018-02-01

    The combination of Eu3+ and Dy3+ in co-doped glassy materials provides interesting applicability for white light emission devices. In this work, Dy:Eu doped Calcium Boroaluminate (CaBAl) glasses were prepared by conventional melting quenching, with 3 wt% of Dy2O3 and Eu2O3 content varying from 0 to 3 wt%, and results of absorption spectra, photoluminescence and photoluminescence lifetime are discussed in terms of Eu2O3 content. The photoluminescence of the samples was studied under excitation of 365 and 405 nm light source. The 365 nm excitation shows favor to the Dy3+ ion emission. The results of photoluminescence lifetime at 575 nm (Dy3+) shows a decrease due to Eu2O3 addition, which suggests an energy transfer from Dy3+ (donor) to the Eu3+ (acceptor). On the other hand, under excitation of 405 nm, the photoluminescence lifetime at 575 nm (Dy3+) shows no significant changes due to Eu2O3 amount, which indicates that the energy transfer from Dy3+ to Eu3+ (under λexc = 405 nm) is negligible. However, the results of photoluminescence under 405 nm excitation present a white yellowish emission in the CIE diagram, which shifts to red with Eu2O3 addition. The combination of a Blue LED (BL) emission with the emission of the samples was also studied in the CIE diagram, in order to improve light emission and to obtain ideal White Light (WL). The results show that by modifying the emission intensity of BL, it is possible to achieve a route for smart lighting, close to the circadian light cycle.

  2. Fish freshness estimation using eye image processing under white and UV lightings

    Science.gov (United States)

    Kanamori, Katsuhiro; Shirataki, Yuri; Liao, Qiuhong; Ogawa, Yuichi; Suzuki, Tetsuhito; Kondo, Naoshi

    2017-05-01

    A non-destructive method of estimating the freshness of fish is required for appropriate price setting and food safety. In particular, for determining the possibility of eating raw fish (sashimi), freshness estimation is critical. We studied such an estimation method by capturing images of fish eyes and performing image processing using the temporal changes of the luminance of pupil and iris. To detect subtle non-visible changes of these features, we used UV (375 nm) light illumination in addition to visible white light illumination. Polarization and two-channel LED techniques were used to remove strong specular reflection from the cornea of the eye and from clear-plastic wrap used to cover the fish to maintain humidity. Pupil and iris regions were automatically detected separately by image processing after the specular reflection removal process, and two types of eye contrast were defined as the ratio of mean and median pixel values of each region. Experiments using 16 Japanese dace (Tribolodon hakonensis) at 23° and 85% humidity for 24 hours were performed. The eye contrast of raw fish increase non-linearly in the initial period and then decreased; however, that of frozen-thawed fish decreased linearly throughout 24 hours, regardless of the lighting. Interestingly, the eye contrast using UV light showed a higher correlation with time than that using white light only in the case of raw fish within the early 6- hour period postmortem. These results show the possibility of estimating fish freshness in the initial stage when fish are eaten raw using white and UV lightings.

  3. White organic light-emitting diodes from three emitter layers

    Energy Technology Data Exchange (ETDEWEB)

    Kim, M.S. [Department of Advanced Materials Science and Engineering, SungKyunKwan University, Suwon, Gyonggi-Do, 440-746 (Korea, Republic of); Lim, J.T. [Department of Advanced Materials Science and Engineering, SungKyunKwan University, Suwon, Gyonggi-Do, 440-746 (Korea, Republic of); Jeong, C.H. [Department of Advanced Materials Science and Engineering, SungKyunKwan University, Suwon, Gyonggi-Do, 440-746 (Korea, Republic of); Lee, J.H. [Department of Advanced Materials Science and Engineering, SungKyunKwan University, Suwon, Gyonggi-Do, 440-746 (Korea, Republic of); Yeom, G.Y. [Department of Advanced Materials Science and Engineering, SungKyunKwan University, Suwon, Gyonggi-Do, 440-746 (Korea, Republic of)]. E-mail: gyyeom@skku.edu

    2006-11-23

    Three-wavelength white organic light-emitting diodes (WOLEDs) were fabricated using two doped layers, which were obtained by separating the recombination zones into three emitter layers. A sky blue emission originated from the 4,4'-bis(2,2'-diphenylethen-1-yl)biphenyl (DPVBi) layer. A green emission originated from a tris(8-quinolinolato)aluminum (III) (Alq{sub 3}) host doped with a green fluorescent 10-(2-benzothiazolyl)-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H,11H-[1] benz opyrano [6,7,8-ij]-quinolizin-11-one (C545T) dye. An orange emission was obtained from the N,N'-bis(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (NPB) host doped with a red fluorescent dye, 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4 H-pyran (DCJTB). A white light resulted from the partial excitations of these three emitter layers by controlling the layer thickness and concentration of the fluorescent dyes in each emissive layer simultaneously. The electroluminescent spectrum of the device was not sensitive to the driving voltage of the device. The white light device showed a maximum luminance of approximately 53,000 cd/m{sup 2}. The external quantum and power efficiency at a luminance of approximately 100 cd/m{sup 2} were 2.62% and 3.04 lm/W, respectively.

  4. Donor doping process and white light generation in CaMoO4 powders with multivalence Pr codoping

    International Nuclear Information System (INIS)

    Zhu Fang; Xiao Zhisong; Zhang Feng; Yan Lu; Huang Anping

    2011-01-01

    Both trivalent praseodymium (Pr 3+ ) and quadrivalent praseodymium (Pr 4+ ) were doped in molybdate powders. Visible emission from matrix was enhanced by multivalent Pr codoping. It was proposed that Pr 3+ ions was donor and supplied quasi-free electron when Pr 3+ took place the Pr 4+ sites. The result showed that multivalence codoping would be an effective way to enhance emission of CaMoO 4 . White light can be generated from Ca 0.98 Pr 0.02 MoO 4 powder via combination of broadband emissions originated from CaMoO 4 matrix and radiative transition of Pr 3+ . It showed warm white light with T c of 3450 K that implies promising application in white light emitting diodes (LEDs).

  5. Testing the stationarity of white dwarf light-curves

    International Nuclear Information System (INIS)

    Molnar, L; Kollath, Z; Plachy, E; Paparo, M

    2009-01-01

    Long period white dwarfs show changes in their frequency spectra from one observing season to another, i.e. their light-curves cannot be considered as stationary multiperiodic variations on long timescales. However, due to the complex frequency spectra of these stars and the narrow frequency spacing, it is still unknown, what the shortest time scale is, where real physical modulation exists. We present tests on artificial data, resembling the observations, using time-frequency distributions (TFDs), Fourier-analysis and the analytical signal method.

  6. Capturing triplet emission in white organic light emitting devices

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Jai [Faculty of EHSE, School of Engineering and IT, B-purple-12, Charles Darwin University, Darwin, NT 0909 (Australia)

    2011-08-15

    The state-of-the art in the white organic light emitting devices (WOLEDs) is reviewed for further developments with a view to enhance the capture of triplet emission. In particular, applying the new exciton-spin-orbit-photon interaction operator as a perturbation, rates of spontaneous emission are calculated in a few phosphorescent materials and compared with experimental results. For iridium based phosphorescent materials the rates agree quite well with the experimental results. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  7. Spectral confocal reflection microscopy using a white light source

    Science.gov (United States)

    Booth, M.; Juškaitis, R.; Wilson, T.

    2008-08-01

    We present a reflection confocal microscope incorporating a white light supercontinuum source and spectral detection. The microscope provides images resolved spatially in three-dimensions, in addition to spectral resolution covering the wavelength range 450-650nm. Images and reflection spectra of artificial and natural specimens are presented, showing features that are not normally revealed in conventional microscopes or confocal microscopes using discrete line lasers. The specimens include thin film structures on semiconductor chips, iridescent structures in Papilio blumei butterfly scales, nacre from abalone shells and opal gemstones. Quantitative size and refractive index measurements of transparent beads are derived from spectral interference bands.

  8. Improvements of phosphorescent white OLEDs performance for lighting application.

    Science.gov (United States)

    Lee, Jonghee; Chu, Hye Yong; Lee, Jeong-Ik; Song, Ki-Im; Lee, Su Jin

    2008-10-01

    We developed white OLED device with high power efficiency, in which blue and orange phosphorescent emitters were used. By introduction of multi-functional interlayer which has partial doping of orange dopant inside EBL, we report WOLEDs with peak external efficiencies up to (14.1% EQE, 31.3 Im/W) without light out-coupling technique. At 1000 cd/m2, the performance achieved was 11.9% EQE, 18.7 Im/W with CIE = (0.39, 0.44). We also found that WOLED performances are related with doping ratio of the orange dopant that was inserted inside EBL.

  9. Interaction of LED light with coinitiator-containing composite resins: effect of dual peaks.

    Science.gov (United States)

    Sim, Jae-Seong; Seol, Hyo-Joung; Park, Jeong-Kil; Garcia-Godoy, Franklin; Kim, Hyung-Il; Kwon, Yong Hoon

    2012-10-01

    Recently the colour stability of composite resins has been an issue due to the emphasis on the aesthetics of restored teeth. The purpose of the present study was to investigate how dual-peak LED units affect the polymerization of coinitiator-containing composite resins. Five composite resins [coinitiator-containing: Aelite LS Posterior (AL), Tetric EvoCeram (TE), and Vit-l-escence (VI); only CQ-containing: Grandio (GD) and Filtek Z350 (Z3)] were light cured using four different light-curing units (LCUs). Among them, Bluephase G2 (BP) and G-light (GL) were dual-peak LED LCUs. Microhardness, polymerization shrinkage, flexural, and compressive properties were measured. BP and GL had no consistent effect on the microhardness of AL, TE, and VI on the top and bottom surfaces of resin specimens. Among the specimens, AL and VI showed the least (9.86-10.41 μm) and greatest (17.58-19.21 μm) polymerization shrinkage, respectively. However, the effect of BP and GL on the shrinkage of specimens was not consistent. Among the specimens, GD showed the greatest flexural properties [strength (FS) and modulus (FM)] and TE showed the lowest flexural and compressive properties [strength (CS) and modulus (CM)]. In same resin product, maximum FS and CS differences due to the different LCUs were 10.3-21.0% and 3.6-9.2%, respectively. Furthermore, the influences of BP and GL on FS and CS were not consistent. The tested dual-peak LED LCUs had no consistent synergic effect on the polymerization of coinitiator-containing composite resins as compared with QTH and single-peak LED LCUs. The dual-peak LED LCUs achieve a similar degree of polymerization in coinitiator-composite resins as QTH and single-peak LED LCUs did. Choice of LCU does not appear to be a determinant of the light curing of coinitiator-composite resins. Copyright © 2012 Elsevier Ltd. All rights reserved.

  10. Research on the Effect of Electrical Signals on Growth of Sansevieria under Light-Emitting Diode (LED Lighting Environment.

    Directory of Open Access Journals (Sweden)

    Liguo Tian

    Full Text Available The plant electrical signal has some features, e.g. weak, low-frequency and time-varying. To detect changes in plant electrical signals, LED light source was used to create a controllable light environment in this study. The electrical signal data were collected from Sansevieria leaves under the different illumination conditions, and the data was analyzed in time domain, frequency domain and time-frequency domain, respectively. These analyses are helpful to explore the relationship between changes in the light environment and electrical signals in Sansevieria leaves. The changes in the plant electrical signal reflected the changes in the intensity of photosynthesis. In this study, we proposed a new method to express plant photosynthetic intensity as a function of the electrical signal. That is, the plant electrical signal can be used to describe the state of plant growth.

  11. Research on the Effect of Electrical Signals on Growth of Sansevieria under Light-Emitting Diode (LED) Lighting Environment

    Science.gov (United States)

    Tian, Liguo; Meng, Qinghao; Wang, Liping; Dong, Jianghui; Wu, Hai

    2015-01-01

    The plant electrical signal has some features, e.g. weak, low-frequency and time-varying. To detect changes in plant electrical signals, LED light source was used to create a controllable light environment in this study. The electrical signal data were collected from Sansevieria leaves under the different illumination conditions, and the data was analyzed in time domain, frequency domain and time–frequency domain, respectively. These analyses are helpful to explore the relationship between changes in the light environment and electrical signals in Sansevieria leaves. The changes in the plant electrical signal reflected the changes in the intensity of photosynthesis. In this study, we proposed a new method to express plant photosynthetic intensity as a function of the electrical signal. That is, the plant electrical signal can be used to describe the state of plant growth. PMID:26121469

  12. Stress relaxed nanoepitaxy GaN for growth of phosphor-free indium-rich nanostructures incorporated in apple-white LEDs

    Energy Technology Data Exchange (ETDEWEB)

    Soh, C.B.; Liu, W.; Ang, N.S.S.; Yong, A.M.; Lai, S.C.; Teng, J.H. [Institute of Materials Research and Engineering, Agency for Science, Technology and Research, 3 Research Link, Singapore 117602 (Singapore); Chua, S.J. [Institute of Materials Research and Engineering, Agency for Science, Technology and Research, 3 Research Link, Singapore 117602 (Singapore); Singapore-MIT Alliance, 4 Engineering Drive 3, Singapore 117576 (Singapore)

    2010-06-15

    Phosphor-free apple-white light emitting diodes (LEDs) have been fabricated using dual stacked InGaN/GaN multiple quantum wells (MQWs) comprising a lower set of long wavelength emitting indium rich nanostructures incorporated in MQWs with an upper set of cyan-green emitting MQWs. The LEDs were grown on nano-epitaxial lateral overgrown (ELO) GaN template formed by regrowth of GaN over SiO{sub 2} film patterned using an anodic alumina oxide mask with holes of {proportional_to}125 nm diameter and a period of 250 nm. The MQWs grown on the nano-ELO GaN templates show stronger photoluminescence intensity and a higher activation energy for their peak emission. A minimal shift in the electroluminescence (EL) spectra with higher injection current applied for LEDs grown on ELO-GaN compared to conventional GaN template, suggests a reduction in strain of the quantum well layers on the nano-ELO GaN template. An enhancement in the light extraction efficiency is also achieved with multiple scattering via the embedded SiO{sub 2} mask. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  13. A controlled trial of the Litebook light-emitting diode (LED light therapy device for treatment of Seasonal Affective Disorder (SAD

    Directory of Open Access Journals (Sweden)

    Telner John

    2007-08-01

    Full Text Available Abstract Background Recent research has emphasized that the human circadian rhythm system is differentially sensitive to short wavelength light. Light treatment devices using efficient light-emitting diodes (LEDs whose output is relatively concentrated in short wavelengths may enable a more convenient effective therapy for Seasonal Affective Disorder (SAD. Methods The efficacy of a LED light therapy device in the treatment of SAD was tested in a randomized, double-blind, placebo-controlled, multi-center trial. Participants aged 18 to 65 with SAD (DSM-IV major depression with seasonal pattern were seen at Baseline and Randomization visits separated by 1 week, and after 1, 2, 3 and 4 weeks of treatment. Hamilton Depression Rating Scale scores (SIGH-SAD were obtained at each visit. Participants with SIGH-SAD of 20 or greater at Baseline and Randomization visits were randomized to active or control treatment: exposure to the Litebook LED treatment device (The Litebook Company Ltd., Alberta, Canada which delivers 1,350 lux white light (with spectral emission peaks at 464 nm and 564 nm at a distance of 20 inches or to an inactivated negative ion generator at a distance of 20 inches, for 30 minutes a day upon awakening and prior to 8 A.M. Results Of the 26 participants randomized, 23 completed the trial. Mean group SIGH-SAD scores did not differ significantly at randomization. At trial end, the proportions of participants in remission (SIGH-SAD less than 9 were significantly greater (Fisher's exact test, and SIGH-SAD scores, as percent individual score at randomization, were significantly lower (t-test, with active treatment than with control, both in an intent-to-treat analysis and an observed cases analysis. A longitudinal repeated measures ANOVA analysis of SIGH-SAD scores also indicated a significant interaction of time and treatment, showing superiority of the Litebook over the placebo condition. Conclusion The results of this pilot study support

  14. True Yellow Light-Emitting Diodes as Phosphor for Tunable Color-Rendering Index Laser-Based White Light

    KAUST Repository

    Janjua, Bilal; Ng, Tien Khee; Zhao, Chao; Prabaswara, Aditya; Consiglio, Giuseppe Bernardo; Priante, Davide; Shen, Chao; Elafandy, Rami T.; Anjum, Dalaver H.; Alhamoud, Abdullah A.; Alatawi, Abdullah A.; Yang, Yang; Alyamani, Ahmed Y.; El-Desouki, Munir M.; Ooi, Boon S.

    2016-01-01

    An urgent challenge for the lighting research community is the lack of efficient optical devices emitting in between 500 and 600 nm, resulting in the “green-yellow gap”. In particular, true green (∼555 nm) and true yellow (∼590 nm), along with blue and red, constitute four technologically important colors. The III-nitride material system, being the most promising choice of platform to bridge this gap, still suffers from high dislocation density and poor crystal quality in realizing high-power, efficient devices. Particularly, the high polarization fields in the active region of such 2D quantum confined structures prevent efficient recombination of carriers. Here we demonstrate a true yellow nanowire (NW) light emitting diode (LED) with peak emission of 588 nm at 29.5 A/cm2 (75 mA in a 0.5 × 0.5 mm2 device) and a low turn-on voltage of ∼2.5 V, while having an internal quantum efficiency of 39%, and without “efficiency droop” up to an injection current density of 29.5 A/cm2. By mixing yellow light from a NW LED in reflective configuration with that of a red, green, and blue laser diode (LD), white light with a correlated color temperature of ∼6000 K and color-rendering index of 87.7 was achieved. The nitride-NW-based device offers a robust, long-term stability for realizing yellow light emitters for tunable color-rendering index solid-state lighting, on a scalable, low-cost, foundry-compatible titanium/silicon substrate, suitable for industry uptake.

  15. True Yellow Light-Emitting Diodes as Phosphor for Tunable Color-Rendering Index Laser-Based White Light

    KAUST Repository

    Janjua, Bilal

    2016-10-11

    An urgent challenge for the lighting research community is the lack of efficient optical devices emitting in between 500 and 600 nm, resulting in the “green-yellow gap”. In particular, true green (∼555 nm) and true yellow (∼590 nm), along with blue and red, constitute four technologically important colors. The III-nitride material system, being the most promising choice of platform to bridge this gap, still suffers from high dislocation density and poor crystal quality in realizing high-power, efficient devices. Particularly, the high polarization fields in the active region of such 2D quantum confined structures prevent efficient recombination of carriers. Here we demonstrate a true yellow nanowire (NW) light emitting diode (LED) with peak emission of 588 nm at 29.5 A/cm2 (75 mA in a 0.5 × 0.5 mm2 device) and a low turn-on voltage of ∼2.5 V, while having an internal quantum efficiency of 39%, and without “efficiency droop” up to an injection current density of 29.5 A/cm2. By mixing yellow light from a NW LED in reflective configuration with that of a red, green, and blue laser diode (LD), white light with a correlated color temperature of ∼6000 K and color-rendering index of 87.7 was achieved. The nitride-NW-based device offers a robust, long-term stability for realizing yellow light emitters for tunable color-rendering index solid-state lighting, on a scalable, low-cost, foundry-compatible titanium/silicon substrate, suitable for industry uptake.

  16. Steering and filtering white light with resonant waveguide gratings

    Science.gov (United States)

    Quaranta, Giorgio; Basset, Guillaume; Martin, Olivier J. F.; Gallinet, Benjamin

    2017-08-01

    A novel thin-film single-layer structure based on resonant waveguide gratings (RWGs) allows to engineer selective color filtering and steering of white light. The unit cell of the structure consists of two adjacent finite-length and cross-talking RWGs, where the former acts as in-coupler and the latter acts as out-coupler. The structure is made by only one nano-imprint lithography replication and one thin film layer deposition, making it fully compatible with up-scalable fabrication processes. We characterize a fabricated optical security element designed to work with the flash and the camera of a smartphone in off-axis light steering configuration, where the pattern is revealed only by placing the smartphone in the proper position. Widespread applications are foreseen in a variety of fields, such as multifocal or monochromatic lenses, solar cells, biosensors, security devices and seethrough optical combiners for near-eye displays.

  17. Design method of freeform light distribution lens for LED automotive headlamp based on DMD

    Science.gov (United States)

    Ma, Jianshe; Huang, Jianwei; Su, Ping; Cui, Yao

    2018-01-01

    We propose a new method to design freeform light distribution lens for light-emitting diode (LED) automotive headlamp based on digital micro mirror device (DMD). With the Parallel optical path architecture, the exit pupil of the illuminating system is set in infinity. Thus the principal incident rays of micro lens in DMD is parallel. DMD is made of high speed digital optical reflection array, the function of distribution lens is to distribute the emergent parallel rays from DMD and get a lighting pattern that fully comply with the national regulation GB 25991-2010.We use DLP 4500 to design the light distribution lens, mesh the target plane regulated by the national regulation GB 25991-2010 and correlate the mesh grids with the active mirror array of DLP4500. With the mapping relations and the refraction law, we can build the mathematics model and get the parameters of freeform light distribution lens. Then we import its parameter into the three-dimensional (3D) software CATIA to construct its 3D model. The ray tracing results using Tracepro demonstrate that the Illumination value of target plane is easily adjustable and fully comply with the requirement of the national regulation GB 25991-2010 by adjusting the exit brightness value of DMD. The theoretical optical efficiencies of the light distribution lens designed using this method could be up to 92% without any other auxiliary lens.

  18. Efficient white organic light emitting devices with dual emitting layers

    International Nuclear Information System (INIS)

    Wu Yaoshan; Hwang Shiaowen; Chen Hsianhung; Lee Mengting; Shen Wenjian; Chen, C.H.

    2005-01-01

    In this paper, a new white organic light-emitting device (OLED) with the structure of indium tin oxide / CF x / 1,4-bis[N-(1-naphthyl)-N'-phenylamino]-biphenyl (NPB) (30 nm)/NPB: 2,8-di(t-butyl)-5,11-di[4-(t-butyl)phenyl]-6,12-diphenylnaphthacene (20 nm; 1.6 %) / 2-methyl-9,10-di(2-naphthyl) anthracene: p-bis(p-N,N-di-phenyl-aminostyryl)benzene (40 nm, 3%) / aluminum tris(8-hydroxyquinoline) (20 nm) / LiF (1 nm) / Al (200 nm) has been investigated. The device showed white emission with a high-luminous yield of 9.75 cd/A at 20 mA/cm 2 , but its Commission Internationale de l'Eclairage chromaticity coordinates appeared to change from (0.34, 0.42) at 6 mA/cm2 to (0.27, 0.37) at 200 mA/cm 2 due to the shift of recombination zone. The change of color with drive current was suppressed by introduction of an electron-blocking layer of NPB along with a hole-blocking layer of aluminum (III) bis(2-methyl-8-quinolinato)4-phenylphenolato to the white OLED which successfully confined the recombination site and achieved a luminous yield of 9.9 cd/A at 20 mA/cm 2

  19. Efficient white organic light emitting devices with dual emitting layers

    Energy Technology Data Exchange (ETDEWEB)

    Wu Yaoshan [Department of Applied Chemistry, National Chiao Tung University, Hsinchu, Taiwan, 30050 (China); Hwang Shiaowen [Display Institute, Microelectronics and Information Systems Research Center, National Chiao Tung University, Hsinchu, Taiwan, 30050 (China)]. E-mail: jesse@faculty.nctu.edu.tw; Chen Hsianhung [Department of Applied Chemistry, National Chiao Tung University, Hsinchu, Taiwan, 30050 (China); Lee Mengting [Department of Applied Chemistry, National Chiao Tung University, Hsinchu, Taiwan, 30050 (China); Shen Wenjian [Department of Applied Chemistry, National Chiao Tung University, Hsinchu, Taiwan, 30050 (China); Chen, C.H. [Display Institute, Microelectronics and Information Systems Research Center, National Chiao Tung University, Hsinchu, Taiwan, 30050 (China)

    2005-09-22

    In this paper, a new white organic light-emitting device (OLED) with the structure of indium tin oxide / CF {sub x} / 1,4-bis[N-(1-naphthyl)-N'-phenylamino]-biphenyl (NPB) (30 nm)/NPB: 2,8-di(t-butyl)-5,11-di[4-(t-butyl)phenyl]-6,12-diphenylnaphthacene (20 nm; 1.6 %) / 2-methyl-9,10-di(2-naphthyl) anthracene: p-bis(p-N,N-di-phenyl-aminostyryl)benzene (40 nm, 3%) / aluminum tris(8-hydroxyquinoline) (20 nm) / LiF (1 nm) / Al (200 nm) has been investigated. The device showed white emission with a high-luminous yield of 9.75 cd/A at 20 mA/cm{sup 2}, but its Commission Internationale de l'Eclairage chromaticity coordinates appeared to change from (0.34, 0.42) at 6 mA/cm2 to (0.27, 0.37) at 200 mA/cm{sup 2} due to the shift of recombination zone. The change of color with drive current was suppressed by introduction of an electron-blocking layer of NPB along with a hole-blocking layer of aluminum (III) bis(2-methyl-8-quinolinato)4-phenylphenolato to the white OLED which successfully confined the recombination site and achieved a luminous yield of 9.9 cd/A at 20 mA/cm{sup 2}.

  20. A white organic light emitting diode with improved stability

    International Nuclear Information System (INIS)

    Zhang Zhilin; Jiang Xueyin; Zhu Wenqing; Zhang Buxin; Xu Shaohong

    2001-01-01

    A white organic light emitting diode (OLED) has been constructed by employing a new blue material and a red dye directly doped in the blue emitting layer. For comparison, another white cell with a blocking layer has also been made. The configurations of the devices are ITO/CuPc/NPB/JBEM(P):DCJT/Alq/MgAg (device 1) and ITO/CuPc/NPB/TPBi:DCJT/Alq/MgAg (device 2) where copper phthalocyanine (CuPc) is the buffer layer, N,N'-bis-(1-naphthyl)-N,N'-diphenyl-1.1'bipheny1-4-4'-diamine (NPB) is the hole transporting layer, 9,10-bis(3'5'-diaryl)phenyl anthracene doped with perylene (JBEM(P)) is the new blue emitting material, N,arylbenzimidazoles (TPBi) is the hole blocking layer, tris(8-quinolinolato)aluminium complex (Alq) is the electron transporting layer, and DCJT is a red dye. A stable and current independent white OLED has been obtained in device 1, which has a maximum luminance of 14 850 cd m -2 , an efficiency of 2.88 Lm W -1 , Commission Internationale de l'Eclairage coordinates of x=0.32, y=0.38 between 4-200 mA cm -2 , and a half lifetime of 2860 h at the starting luminance of 100 cd m -2 . Device 1 has a stability more than 50 times better than that of device 2. (author)

  1. Bridging “green gap” of LEDs: Giant light output enhancement and directional control of LEDs via embedded nano-void photonic crystals

    KAUST Repository

    Tsai, Yu-Lin; Liu, Che-Yu; Krishnan, Chirenjeevi; Lin, Da-Wei; Chu, You-Chen; Chen, Tzu-Pei; Shen, Tien-Lin; Kao, Tsung-Sheng; Charlton, Martin; Yu, Peichen; Lin, Chien-Chung; Kuo, Hao-Chung; He, Jr-Hau

    2015-01-01

    Green LEDs do not show the same level of performance as their blue and red cousins, greatly hindering the solid-state lighting development, which is so-called “green gap”. In this work, nano-void photonic crystals (NVPCs) were fabricated to embed within the GaN/InGaN green LEDs by using epitaxial lateral overgrowth (ELO) and nano-sphere lithography techniques. The NVPCs act as an efficient scattering back-reflector to outcouple the guided and downward photons, which not only boosting light extraction efficiency of LEDs with an enhancement of 78% but also collimating the view angle of LEDs from 131.5゜to 114.0゜. This could be because the highly scattering nature of NVPCs which reduce the interference giving rise to Fabry-Perot resonance. Moreover, due to the threading dislocation suppression and strain relief by the NVPCs, the internal quantum efficiency was increased by 25% and droop behavior was reduced from 37.4% to 25.9%. The enhancement of light output power can be achieved as high as 151% at a driving current of 350 mA. Giant light output enhancement and directional control via NVPCs points the way towards a promising avenue of solid-state lighting.

  2. Bridging “green gap” of LEDs: Giant light output enhancement and directional control of LEDs via embedded nano-void photonic crystals

    KAUST Repository

    Tsai, Yu-Lin

    2015-11-23

    Green LEDs do not show the same level of performance as their blue and red cousins, greatly hindering the solid-state lighting development, which is so-called “green gap”. In this work, nano-void photonic crystals (NVPCs) were fabricated to embed within the GaN/InGaN green LEDs by using epitaxial lateral overgrowth (ELO) and nano-sphere lithography techniques. The NVPCs act as an efficient scattering back-reflector to outcouple the guided and downward photons, which not only boosting light extraction efficiency of LEDs with an enhancement of 78% but also collimating the view angle of LEDs from 131.5゜to 114.0゜. This could be because the highly scattering nature of NVPCs which reduce the interference giving rise to Fabry-Perot resonance. Moreover, due to the threading dislocation suppression and strain relief by the NVPCs, the internal quantum efficiency was increased by 25% and droop behavior was reduced from 37.4% to 25.9%. The enhancement of light output power can be achieved as high as 151% at a driving current of 350 mA. Giant light output enhancement and directional control via NVPCs points the way towards a promising avenue of solid-state lighting.

  3. White light generation tuned by dual hybridization of nanocrystals and conjugated polymers

    Energy Technology Data Exchange (ETDEWEB)

    Demir, Hilmi Volkan [Devices and Sensors Group and Nanotechnology Research Center, Bilkent University, Ankara 06800 (Turkey); Nizamoglu, Sedat [Devices and Sensors Group and Nanotechnology Research Center, Bilkent University, Ankara 06800 (Turkey); Ozel, Tuncay [Devices and Sensors Group and Nanotechnology Research Center, Bilkent University, Ankara 06800 (Turkey); Mutlugun, Evren [Devices and Sensors Group and Nanotechnology Research Center, Bilkent University, Ankara 06800 (Turkey); Huyal, Ilkem Ozge [Devices and Sensors Group and Nanotechnology Research Center, Bilkent University, Ankara 06800 (Turkey); Sari, Emre [Devices and Sensors Group and Nanotechnology Research Center, Bilkent University, Ankara 06800 (Turkey); Holder, Elisabeth [Functional Polymers Group and Institute of Polymer Technology, University of Wuppertal, Gaussstrasse 20, D-42097 Wuppertal (Germany); Tian Nan [Functional Polymers Group and Institute of Polymer Technology, University of Wuppertal, Gaussstrasse 20, D-42097 Wuppertal (Germany)

    2007-10-15

    Dual hybridization of highly fluorescent conjugated polymers and highly luminescent nanocrystals (NCs) is developed and demonstrated in multiple combinations for controlled white light generation with high color rendering index (CRI) (> 80) for the first time. The generated white light is tuned using layer-by-layer assembly of CdSe/ZnS core-shell NCs closely packed on polyfluorene, hybridized on near-UV emitting nitride-based light emitting diodes (LEDs). The design, synthesis, growth, fabrication and characterization of these hybrid inorganic-organic white LEDs are presented. The following experimental realizations are reported: (i) layer-by-layer hybridization of yellow NCs ({lambda}{sub PL}=580 nm) and blue polyfluorene ({lambda}{sub PL}=439 nm) with tristimulus coordinates of (x, y)=(0.31, 0.27), correlated color temperature of T{sub c}=6962 K and CRI of R{sub a}=53.4; (ii) layer-by-layer assembly of yellow and green NCs ({lambda}{sub PL}=580 and 540 nm) and blue polyfluorene ({lambda}{sub PL}=439 nm) with (x, y)=(0.23, 0.30), T{sub c}=14395 K and R{sub a}=65.7; and (iii) layer-by-layer deposition of yellow, green and red NCs ({lambda}{sub PL}=580, 540 and 620 nm) and blue polyfluorene ({lambda}{sub PL}=439 nm) with (x, y)=(0.38, 0.39), T{sub c}=4052 K and R{sub a}= 83.0. The CRI is demonstrated to be well controlled and significantly improved by increasing multi-chromaticity of the NC and polymer emitters.

  4. High color rendering index of remote-type white LEDs with multi-layered quantum dot-phosphor films and short-wavelength pass dichroic filters

    Science.gov (United States)

    Yoon, Hee Chang; Oh, Ji Hye; Do, Young Rag

    2014-09-01

    This paper introduces high color rendering index (CRI) white light-emitting diodes (W-LEDs) coated with red emitting (Sr,Ca)AlSiN3:Eu phosphors and yellowish-green emitting AgIn5S8/ZnS (AIS/ZS) quantum dots (QDs) on glass or a short-wavelength pass dichroic filter (SPDF), which transmit blue wavelength regions and reflect yellow wavelength regions. The red emitting (Sr,Ca)AlSiN3:Eu phosphor film is coated on glass and a SPDF using a screen printing method, and then the yellowish-green emitting AIS/ZS QDs are coated on the red phosphor (Sr,Ca)AlSiN3:Eu film-coated glass and SPDF using the electrospray (e-spray) method.To fabricate the red phosphor film, the optimum amount of phosphor is dispersed in a silicon binder to form a red phosphor paste. The AIS/ZS QDs are mixed with dimethylformamide (DMF), toluene, and poly(methyl methacrylate) (PMMA) for the e-spray coating. The substrates are spin-coated with poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) to fabricate a conductive surface. The CRI of the white LEDs is improved through inserting the red phosphor film between the QD layer and the glass substrate. Furthermore, the light intensities of the multi-layered phosphor films are enhanced through changing the glass substrate to the SPDF. The correlated color temperatures (CCTs) vary as a function of the phosphor concentration in the phosphor paste. The optical properties of the yellowish-green AIS/ZS QDs and red (Sr,Ca)AlSiN3:Eu phosphors are characterized using photoluminescence (PL), and the multi-layered QD-phosphor films are measured using electroluminescence (EL) with an InGaN blue LED (λmax = 450 nm) at 60 mA.

  5. Application of Photocatalysts and LED Light Sources in Drinking Water Treatment

    Directory of Open Access Journals (Sweden)

    Gopal Achari

    2013-09-01

    Full Text Available This study investigates a cross-section of TiO2 compositions for which existing evidence suggests the prospect of improved performance compared to standard Degussa P25. In the context of a program aimed toward a 365 nm LED based photo-reactor, the question is whether a distinctly superior photocatalyst composition for drinking water treatment is now available that would shape design choices. An answer was sought by synthesizing several photocatalysts with reported high reactivity in some context in the literature, and by performing photocatalysts reactivity tests using common pollutants of water system including Natural Organic Matter (NOM and Emerging Contaminants (ECs from the pesticide and pharmaceutical classes. 365 nm Light Emitting Diodes (LEDs were used as the irradiation source. Since LEDs are now available in the UV, we did not examine the TiO2 modifications that bring band gap excitation into the region beyond 400 nm. The results suggest that the choice of the photocatalyst should be best made to fit the reactor design and photocatalyst mounting constraints such as mass transport, reactive surface, and light field. No photocatalyst composition overall, superior for all classes emerged.

  6. Evaluation of wear rate of dental composites polymerized by halogen or LED light curing units

    Directory of Open Access Journals (Sweden)

    Alaghehmand H.

    2006-08-01

    Full Text Available Background and Aim: Sufficient polymerization is a critical factor to obtain optimum physical properties and clinical efficacy of resin restorations. The aim of this study was to evaluate wear rates of composite resins polymerized by two different systems Light Emitting Diodes (LED to and Halogen lamps. Materials and Methods: In this laboratory study, 20 specimens of A3 Tetric Ceram composite were placed in brass molds of 2*10*10 mm dimensions and cured for 40 seconds with 1 mm distance from surface. 10 specimens were cured with LED and the other 10 were cured with Halogen unit. A device with the ability to apply force was developed in order to test the wear of composites. After storage in distilled water for 10 days, the specimens were placed in the wear testing machine. A chrome cobalt stylus with 1.12 mm diameter was applied against the specimens surfaces with a load of 2 kg. The weight of each samples before and after 5000, 10000, 20000, 40000, 80000 and 120000 cycles was measured using an electronic balance with precision of 10-4 grams. Data were analyzed using t test and paired t test. P0.05. Conclusion: Based on the results of this study, LED and halogen light curing units resulted in a similar wear rate in composite resin restorations.

  7. Effects of LED or laser phototherapy on bone defects grafted with MTA and irradiated with laser or LED light: a comparative Raman spectroscopic study

    Science.gov (United States)

    Pinheiro, Antonio L. B.; Soares, Luiz G. P.; Barbosa, Artur Felipe S.; Silveira, Landulfo, Jr.

    2012-03-01

    We studied peaks of calcium hydroxyapatite - CHA on defects grafted with MTA, treated or not with Light Emitting Diode - LED or IR Laser. 54 rats were divided in 6 groups each subdivided into 3 subgroups (15,21,30d). LED (λ850 +/- 10nm) or IR Laser (λ850 nm) was applied over (LED) or in 4 points around the defect at 48 h intervals for 15 days. Raman readings were taken at the surface of the defect. The smaller overall intensity of the peak was found in Group MTA + Laser (1510.2 +/- 274.1) and the highest on Group LED (2322 +/- 715). There were no statistically significant differences between non-irradiated subjects on regards the CHA peaks. On the other hand, there were statistically significant differences between the Group Clot and LED, Clot and Laser, and Clot and MTA + Laser (p =0.01, p = 0.02, p = 0.003). There were no significant differences between Group MTA and MTA + LED (p=0.2) but significant differences were seen between Groups MTA and MTA + Laser (p=0.01). Significant differences were also observed between Groups LED and Laser (p <0.001) and between Groups MTA + LED and MTA + Laser (p=0.009). MTA, due to its characteristics, seemed to be directly affected by the light. However, the use of either phototherapy positively affected bone healing similarly as observed on different studies using other biomaterials. The overall analysis of our results indicated that the use of either light source resulted in a better, more advanced, and of quality bone repair.

  8. Synthesis and luminescence properties of glass ceramics containing MSiO3:Eu2+ (M=Ca, Sr, Ba) phosphors for white LED

    International Nuclear Information System (INIS)

    Cui Zhiguang; Jia Guohua; Deng Degang; Hua Youjie; Zhao Shilong; Huang Lihui; Wang Huanping; Ma Hongping; Xu Shiqing

    2012-01-01

    Eu 2+ doped silicate glasses were prepared of the system 52SiO 2 -48MO: xEu 2+ (in molar ratio, M=Ca, Sr, Ba; x=1, 3, 5, 7, 9) by a high temperature melt-quenching method in a reducing atmosphere. Glass ceramics containing MSiO 3 :Eu 2+ (M=Ca, Sr, Ba) nano-phosphors were obtained after the heat treatment of the glass samples. The excitation, emission spectra and lifetime decay curves of 4f 6 5d 1 →4f 7 of Eu 2+ were measured and interpreted with respect to their crystal structures and multi-site occupations of divalent europium in the hosts. Their excitation bands mainly extend from 450 to 250 nm, which is adaptable to the main emission region of the UV LED chip. With UV light excitation, the Eu 2+ emission in CaSiO 3 , SrSiO 3 and BaSiO 3 shows blue, green and yellow colors centered at 440, 505 and 555 nm, respectively. The critical Eu 2+ concentration was studied and determined to be x=5 for both CaSiO 3 and SrSiO 3 and x=7 for BaSiO 3 phosphors. The results show that the Eu 2+ doped glass ceramic phosphors containing MSiO 3 (M=Ca, Sr, Ba) nano-crystals can be used as potential matrix materials for a high power white LED pumped by the UV LED chip. - Highlights: → Glass ceramic containing MSiO 3 :Eu 2+ (M=Ca, Sr, Ba) phosphors prepared. → Derived phosphors emit intensively blue, green and yellow colors. → Their luminescence properties and crystal structures have been investigated. → Concentration quenching effects observed and analyzed. → Potential application for UV chip exciting white LED evaluated.

  9. Examination of the LED Source in Traffic Lights and the Effect of Airborne Dirt on its Performance

    Directory of Open Access Journals (Sweden)

    Amela Softić

    2017-05-01

    Full Text Available The performed evaluation consisted of two phases: measurement of the illumination levels of (new LED system and carrying out the public opinion poll on the subjective visual performance of LED in traffic lights. The results of the measured levels of illumination show that deposition of dirt considerably affects its values. The survey results confirm an overall positive impression on LED performances in traffic lights.

  10. Thermal, spectral, and surface properties of LED light-polymerized bulk fill resin composites.

    Science.gov (United States)

    Pişkin, Mehmet Burçin; Atalı, Pınar Yılmaz; Figen, Aysel Kantürk

    2015-02-01

    The aim of this study was to evaluate the thermal, spectral, and surface properties of four different bulk fill materials – SureFil SDR (SDR, Dentsplay DETREY), QuixFil (QF, Dentsplay DETREY), X-tra base (XB, Voco) X-tra fil (XF, Voco) – polymerized by light-emitting diode (LED). Resin matrix, filler type, size and amount, and photoinitiator types influence the degree of conversion. LED-cured bulk fill composites achieved sufficient polymerization. Scanning electron microscope (SEM) analysis revealed different patterns of surface roughness, depending on the composite material. Bulk fill materials showed surface characteristics similar to those of nanohybrid composites. Based on the thermal analysis results, glass transition (T(g)) and initial degradation (T(i)) temperatures changed depending on the bulk fill resin composites.

  11. Exposure of fluid milk to LED light negatively affects consumer perception and alters underlying sensory properties.

    Science.gov (United States)

    Martin, Nicole; Carey, Nancy; Murphy, Steven; Kent, David; Bang, Jae; Stubbs, Tim; Wiedmann, Martin; Dando, Robin

    2016-06-01

    Fluid milk consumption per capita in the United States has been steadily declining since the 1940s. Many factors have contributed to this decline, including the increasing consumption of carbonated beverages and bottled water. To meet the challenge of stemming the decline in consumption of fluid milk, the dairy industry must take a systematic approach to identifying and correcting for factors that negatively affect consumers' perception of fluid milk quality. To that end, samples of fluid milk were evaluated to identify factors, with a particular focus on light-emitting diode (LED) light exposure, which negatively affect the perceived sensory quality of milk, and to quantify their relative effect on the consumer's experience. Fluid milk samples were sourced from 3 processing facilities with varying microbial postprocessing contamination patterns based on historical testing. The effect of fat content, light exposure, age, and microbiological content were assayed across 23 samples of fluid milk, via consumer, descriptive sensory, and instrumental analyses. Most notably, light exposure resulted in a broad negative reaction from consumers, more so than samples with microbiological contamination exceeding 20,000 cfu/mL on days approaching code. The predominant implication of the study is that a component of paramount importance in ensuring the success of the dairy industry would be to protect fluid milk from all sources of light exposure, from processing plant to consumer. Copyright © 2016 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

  12. Three-peak standard white organic light-emitting devices for solid-state lighting

    Science.gov (United States)

    Guo, Kunping; Wei, Bin

    2014-12-01

    Standard white organic light-emitting device (OLED) lighting provides a warm and comfortable atmosphere and shows mild effect on melatonin suppression. A high-efficiency red OLED employing phosphorescent dopant has been investigated. The device generates saturated red emission with Commission Internationale de l'Eclairage (CIE) coordinates of (0.66, 0.34), characterized by a low driving voltage of 3.5 V and high external quantum efficiency of 20.1% at 130 cd m-2. In addition, we have demonstrated a two-peak cold white OLED by combining with a pure blue emitter with the electroluminescent emission of 464 nm, 6, 12-bis{[N-(3,4-dimethylpheyl)-N-(2,4,5-trimethylphenyl)]} chrysene (BmPAC). It was found that the man-made lighting device capable of yielding a relatively stable color emission within the luminance range of 1000-5000 cd m-2. And the chromaticity coordinates, varying from (0.25, 0.21) to (0.23, 0.21). Furthermore, an ultrathin layer of green-light-emitting tris (2-phenylpyridinato)iridium(Ⅲ) Ir(ppy)3 in the host material was introduced to the emissive region for compensating light. By appropriately controlling the layer thickness, the white light OLED achieved good performance of 1280 cd m-2 at 5.0 V and 5150 cd m-2 at 7.0 V, respectively. The CIE coordinates of the emitted light are quite stable at current densities from 759 cd m-2 to 5150 cd m-2, ranging from (0.34, 0.37) to (0.33, 0.33).

  13. OSL response bleaching of BeO samples, using fluorescent light and blue LEDs

    International Nuclear Information System (INIS)

    Groppo, Daniela Piai; Caldas, Linda V.E.

    2015-01-01

    The optically stimulated luminescence (OSL) is widely used as a dosimetric technique for many applications. In this work, the OSL response bleaching of BeO samples was studied. The samples were irradiated using a beta radiation source ( 90 Sr+ 90 Y); the bleaching treatments (fluorescent light and blue LEDs) were performed, and the results were compared. Various optical treatment time intervals were tested until reaching the complete bleaching of the OSL response. The best combination of the time interval and bleaching type was analyzed. (author)

  14. Perception of Human Skin in Street Lighting under Five Types of Led Spectra

    DEFF Research Database (Denmark)

    Fontoynont, Marc; Bruyère, Lucie; Blanc-Gonnet, Joachim

    2013-01-01

    A panel of observers has been invited to rate and compare the quality of 5 spectra of LED sources used for street lighting, on 30 subjects. Vertical illuminance on faces was 14 lx (+/- 3 lx) . All 30 subjects did not have the same type of skin. 60% were from the European Caucasian type (clear skin......). The xtreme stimuli (2200K and 4800K) were rejected by all participants. When presented in pairs (Thurstone protocole), 75% of observers preferred the 3200K stimulus, 61% the 4000 K stimulus, 59% preferred the 2700K stimulus. People with Asian skin was found to be preferred under CCT of 3200 K and below...

  15. OSL response bleaching of BeO samples, using fluorescent light and blue LEDs

    International Nuclear Information System (INIS)

    Groppo, D P; Caldas, L V E

    2016-01-01

    The optically stimulated luminescence (OSL) is widely used as a dosimetric technique for many applications. In this work, the OSL response bleaching of BeO samples was studied. The samples were irradiated using a beta radiation source ("9"0Sr+"9"0Y); the bleaching treatments (fluorescent light and blue LEDs) were performed, and the results were compared. Various optical treatment time intervals were tested until reaching the complete bleaching of the OSL response. The best combination of the time interval and bleaching type was analyzed. (paper)

  16. The Influence of Different Recycling Scenarios on the Mechanical Design of an LED Weatherproof Light Fitting

    Directory of Open Access Journals (Sweden)

    Víctor Camañes

    2014-08-01

    Full Text Available This paper analyzes the high relevance of material selection for the sustainable development of an LED weatherproof light fitting. The research reveals how this choice modifies current and future end of life scenarios and can reduce the overall environmental impact. This life cycle assessment has been carried out with Ecotool, a software program especially developed for designers to assess the environmental performance of their designs at the same time that they are working on them. Results show that special attention can be put on the recycling and reusing of the product from the initial stages of development.

  17. Very High Frequency Resonant DC/DC Converters for LED Lighting

    DEFF Research Database (Denmark)

    Madsen, Mickey Pierre; Knott, Arnold; Andersen, Michael A. E.

    2013-01-01

    This paper presents a very high frequency DC/DC converter for LED lighting. Several resonant topologies are compared and their usability discussed. At the end the resonant SEPIC converter is chosen based on the achievable power density and total bill of material. Simulations of a 51 MHz converter...... with 40 V input and 15 V output are made. The simulation shows possibility of achieving efficiency up to 87 % even with a HEXFET Power MOSFET. Three prototypes of the simulated converter are implemented showing good correlation with simulations. The prototypes have efficiencies up to 84 % and power...

  18. High-flux focusable color-tunable and efficient white-light-emitting diode light engine for stage lighting

    DEFF Research Database (Denmark)

    Chakrabarti, Maumita; Pedersen, Henrik Chresten; Petersen, Paul Michael

    2016-01-01

    colors through a microlens array(MA) at the gate of ∅50 mm. Hence, it produces homogeneous color-mixed tunable white light from 3000 to6000 K that can be adjustable from flood to spot position providing 10% translational loss, whereas the correspondingloss from the halogen–Fresnel spotlight is 37...

  19. LED Lighting in a Performing Arts Building at the University of Florida

    Energy Technology Data Exchange (ETDEWEB)

    Miller, Naomi J.; Kaye, Stan; Coleman, Patricia; Wilkerson, Andrea M.; Perrin, Tess E.; Sullivan, Gregory P.

    2014-07-01

    The U.S. DOE GATEWAY Demonstration Program supports demonstrations of high-performance solid-state lighting (SSL) products in order to develop empirical data and experience with the in-the-field applications of this advanced lighting technology. This report describes the process and results of the 2013 - 2014 GATEWAY demonstration of SSL technology in the Nadine McGuire Theatre and Dance Pavilion at the University of Florida, Gainesville, FL. The LED solutions combined with dimming controls utilized in four interior spaces - the Acting Studio, Dance Studio, Scene Shop, and Dressing Room - received high marks from instructors, students/performers, and reduced energy use in all cases. The report discusses in depth and detail of each project area including specifications, energy savings, and user observations. The report concludes with lessons learned during the demonstration.

  20. Supplemental Blue LED Lighting Array to Improve the Signal Quality in Hyperspectral Imaging of Plants

    Directory of Open Access Journals (Sweden)

    Anne-Katrin Mahlein

    2015-06-01

    Full Text Available Hyperspectral imaging systems used in plant science or agriculture often have suboptimal signal-to-noise ratio in the blue region (400–500 nm of the electromagnetic spectrum. Typically there are two principal reasons for this effect, the low sensitivity of the imaging sensor and the low amount of light available from the illuminating source. In plant science, the blue region contains relevant information about the physiology and the health status of a plant. We report on the improvement in sensitivity of a hyperspectral imaging system in the blue region of the spectrum by using supplemental illumination provided by an array of high brightness light emitting diodes (LEDs with an emission peak at 470 nm.

  1. Novel green-emitting Na2CaPO4F:Eu2+ phosphors for near-ultraviolet white light-emitting diodes

    International Nuclear Information System (INIS)

    Huang, Chien-Hao; Chen, Yen-Chi; Kuo, Te-Wen; Chen, Teng-Ming

    2011-01-01

    In this study, green-emitting Na 2 CaPO 4 F:Eu 2+ phosphors were synthesized by solid-state reactions. The excitation spectra of the phosphors showed a broad hump between 250 and 450 nm; the spectra match well with the near-ultraviolet (NUV) emission spectra of light-emitting diodes (LEDs). The emission spectrum showed an intense broad emission band centered at 506 nm. White LEDs were fabricated by integrating a 390 nm NUV chip comprising blue-emitting BaMgAl 10 O 17 :Eu 2+ , green-emitting Na 2 CaPO 4 F:0.02 Eu 2+ , and red-emitting CaAlSiN 3 :Eu 2+ phosphors into a single package; the white LEDs exhibited white light with a correlated color temperature of 5540 K, a color-rendering index of 90.75, and color coordinates (0.332, 0.365) close to those of ideal white light. - Highlights: → Novel green-emitting Na 2 CaPO 4 F:Eu 2+ phosphors were synthesized by solid-state reactions in this research. → White LEDs were fabricated by integrating a 390 nm NUV chip comprising blue-emitting BaMgAl 10 O 17 :Eu 2+ , green-emitting Na 2 CaPO 4 F:0.02Eu 2+ , and red-emitting CaAlSiN 3 :Eu 2+ phosphors into a single package. → The white LEDs exhibited white light with a correlated color temperature of 5540 K, a color-rendering index of 90.75, and color coordinates (0.332, 0.365) close to those of ideal white light.

  2. Luminescent properties of near UV excitable Ba2ZnS3 : Mn red emitting phosphor blend for white LED and display applications

    International Nuclear Information System (INIS)

    Thiyagarajan, P; Kottaisamy, M; Rao, M S Ramachandra

    2006-01-01

    A bright red colour emitting Mn doped Ba 2 ZnS 3 phosphor was prepared by an ecologically acceptable carbothermal reduction method without an inert gas or hazardous gas (H 2 S) environment. The phosphor can be excited with UV wavelength radiation to realize emission in the visible range. X-ray diffraction studies confirm an orthorhombic structure with phase group, pnam. The photoluminescence (PL) emission spectrum shows a broad band with emission maximum at 625 nm under the host excitation of 358 nm, which lies in the near UV region. The concentration of Mn was varied from 0.0025 to 0.20 mole with respect to Zn and the optimum PL emission intensity was obtained at the concentration of 0.01 mole of Mn. The CIE (Commission Internationale de l'Eclairage) colour coordinates measurement (x = 0.654 and y = 0.321) shows that the primary emission is in the red region. The triband phosphors blend containing Sr 5 (PO 4 ) 3 Cl : Eu 2+ (blue), ZnS : Cu,Al (green) and Ba 2 ZnS 3 : Mn (red) shows white light emission under 365 nm excitation having CIE chromaticity (x = 0.292 and y = 0.251). Since phosphor excitation lies in the near UV excitable region, giving a bright red emission, it can be used for applications in near UV phosphor converted white LED lighting and display devices

  3. Transforming White Light into Rainbows: Segmentation Strategies for Successful School Tax Elections

    Science.gov (United States)

    Senden, J. Bradford; Lifto, Don E.

    2009-01-01

    In the late 1600s, British physicist Sir Isaac Newton first demonstrated refraction and dispersion in a triangular prism. He discovered that a prism could decompose white light into a spectrum. Hold a prism up to the light at the correct angle and white light magically splits into vivid colors of the rainbow! So what do prisms and rainbows have to…

  4. Comparative Evaluation of Shear Bond Strength and Debonding Characteristics using Conventional Halogen Light Curing Unit and LED Light Curing Unit: An in vitro Study

    Directory of Open Access Journals (Sweden)

    Amit Bhardwaj

    2013-01-01

    Conclusion: The result of this study showed promise for the orthodontic application of LED as light curing units and 20 seconds of exposure time is adequate for both LED and Halogen light, since increasing the curing time to 40 seconds showed no significant difference.

  5. White-light full-field OCT resolution improvement by image sensor colour balance adjustment: numerical simulation

    International Nuclear Information System (INIS)

    Kalyanov, A L; Lychagov, V V; Ryabukho, V P; Smirnov, I V

    2012-01-01

    The possibility of improving white-light full-field optical coherence tomography (OCT) resolution by image sensor colour balance tuning is shown numerically. We calculated the full-width at half-maximum (FWHM) of a coherence pulse registered by a silicon colour image sensor under various colour balance settings. The calculations were made for both a halogen lamp and white LED sources. The results show that the interference pulse width can be reduced by the proper choice of colour balance coefficients. The reduction is up to 18%, as compared with a colour image sensor with regular settings, and up to 20%, as compared with a monochrome sensor. (paper)

  6. Investigations of white light emitting europium doped zinc oxide nanoparticles

    International Nuclear Information System (INIS)

    Ashtaputre, S S; Nojima, A; Marathe, S K; Matsumura, D; Ohta, T; Tiwari, R; Dey, G K; Kulkarni, S K

    2008-01-01

    Europium doped zinc oxide nanoparticles have been synthesized using a chemical route. The amount of doped europium was varied which shows the changes in the photoluminescence (PL) intensity. The post synthesis annealing effect on the properties of ZnO nanoparticles has also been investigated. In general, PL is broad and a white light is emitted which originates from ZnO and the intra-4f transitions of Eu 3+ ions. The x-ray diffraction patterns do not show any Eu-related peaks for as-synthesized ZnO nanoparticles as well as for annealed samples. X-ray absorption spectroscopy reveals that europium ions are present on the surface of the core of ZnO and inside the shell of zinc hydroxide [Zn(OH 2 )] after annealing

  7. A simple white noise analysis of neuronal light responses.

    Science.gov (United States)

    Chichilnisky, E J

    2001-05-01

    A white noise technique is presented for estimating the response properties of spiking visual system neurons. The technique is simple, robust, efficient and well suited to simultaneous recordings from multiple neurons. It provides a complete and easily interpretable model of light responses even for neurons that display a common form of response nonlinearity that precludes classical linear systems analysis. A theoretical justification of the technique is presented that relies only on elementary linear algebra and statistics. Implementation is described with examples. The technique and the underlying model of neural responses are validated using recordings from retinal ganglion cells, and in principle are applicable to other neurons. Advantages and disadvantages of the technique relative to classical approaches are discussed.

  8. Radio and white-light observations of coronal transients

    Science.gov (United States)

    Dulk, G. A.

    1980-01-01

    Optical, radio and X-ray evidence of violent mass motions in the corona has existed for some years but only recently have the form, nature, frequency and implication of the transients become obvious. In this paper the observed properties of coronal transients are reviewed, with concentration on the white-light and radio manifestations. The classification according to speeds seems to be meaningful, with the slow transients having thermal emissions at radio wavelengths and the fast ones nonthermal. The possible mechanisms involved in the radio bursts are then discussed and estimates of various forms of energy are reviewed. It appears that the magnetic energy transported from the sun by the transient exceeds that of any other form, and that magnetic forces dominate in the dynamics of the motions. The conversion of magnetic energy into mechanical energy, by expansion of the field, provides a possible driving force for the coronal and interplanetary shock waves.

  9. Radio and white-light observations of coronal transients

    International Nuclear Information System (INIS)

    Dulk, G.A.

    1980-01-01

    Optical, radio and X-ray evidence of violent mass motions in the corona has existed for some years but only recently have the form, nature, frequency and implication of the transients become obvious. The author reviews the observed properties of coronal transients, concentrating on the white-light and radio manifestations. The classification according to speeds seems to be meaningful, with the slow transients having thermal emissions at radio wavelengths and the fast ones non-thermal. The possible mechanisms involved in the radio bursts are discussed and the estimates of various forms of energy are reviewed. It appears that the magnetic energy transported from the Sun by the transient exceeds that of any other form, and that magnetic forces dominate in the dynamics of the motions. The conversion of magnetic energy into mechanical energy, by expansion of the fields, provides a possible driving force for the coronal and interplanetary shock waves. (Auth.)

  10. Topology of White Stars in Relativistic Fragmentation of Light Nuclei

    CERN Document Server

    Andreeva, N P; Vokal, S; Vokalova, A; Gaitinov, A Sh; Gerassimov, S G; Goncharova, L A; Dronov, V A; Zarubin, P I; Zarubina, I G; Kovalenko, A D; Kravchakova, A; Larionova, V G; Levitskaja, O V; Lepehin, F G; Malakhov, A I; Moiseenko, A A; Orlova, G I; Peresadko, N G; Polukhina, N G; Rukojatkin, P A; Rusakova, V V; Salmanova, N A; Sarkisian, V R; Simonov, B B; Stan, E; Stanoeva, R; Chernyavsky, M M; Haidue, M; Kharlamov, S P; Tsakov, I; Shchedrina, T V

    2004-01-01

    In the present paper, experimental observation of the multifragmentation processes of light relativistic nuclei carried out by means of emulsions are reviewed. Events of the type of "white stars" in which the dissociation of relativistic nuclei is not accompanied by the production of mesons and the target-nucleus fragments are considered. A distinctive feature of the charge topology in the dissociation of the Ne, Mg, Si and S nuclei is an almost total suppression of the binary splitting of nuclei to fragments with charges higher than 2. The growth of the nuclear fragmentation degree is revealed in an increase in the multiplicity of singly and doubly charged fragments with decreasing charge of the main non-excited part of the fragmenting nucleus. The processes of dissociation of stable Li, Be, B, C, N, and O isotopes to charged fragments were used to study special features of the formation of systems consisting of the lightest nuclei - alpha, d and t. Clustering of the 3He nucleus can be detected in "white sta...

  11. Considerable photoluminescence enhancement of LiEu(MoO{sub 4}){sub 2} red phosphors via Bi and/or Si doping for white LEDs

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Qing-Feng [Department of Materials Science and Engineering, Harbin Institute of Technology Shenzhen Graduate School, Shenzhen, Guangdong 518055 (China); Department of Materials Science and Engineering, South University of Science and Technology of China, Shenzhen, Guangdong 518055 (China); Liu, Ying [Department of Materials Science and Engineering, South University of Science and Technology of China, Shenzhen, Guangdong 518055 (China); Wang, Yu [Department of Physics and Materials Science, City University of Hong Kong, Hong Kong Special Administrative Region (Hong Kong); Wang, Wenxi; Wan, Yi [Department of Materials Science and Engineering, South University of Science and Technology of China, Shenzhen, Guangdong 518055 (China); Wang, Gui-Gen [Department of Materials Science and Engineering, Harbin Institute of Technology Shenzhen Graduate School, Shenzhen, Guangdong 518055 (China); Lu, Zhou-Guang [Department of Materials Science and Engineering, South University of Science and Technology of China, Shenzhen, Guangdong 518055 (China)

    2015-03-15

    Graphical abstract: Doping of Bi and Si into the lattice leads to an considerable increase of the excitation efficiency and luminous intensity, and obvious movement of the CIE chromaticity coordinates to the NTSC standard values of the LiEu(MoO{sub 4}){sub 2}, a promising red phosphors suitable for near UV excited white-light emitting diodes. - Highlights: • High performance red phosphors for near UV light excited white LEDs. • Lithium lanthanide molybdate red phosphors. • Bi and Si substitution. • Considerable enhancement of luminescence intensity and excitation efficiency. • CIE chromaticity coordinates very close to the NTSC standard values. - Abstract: Novel Bi and/or Si substituted LiEu(MoO{sub 4}){sub 2} phosphors, where Bi was used as sensitizer to enhance the emission intensity and Si was used as substitution to improve the excitation efficiency, were prepared using the sol–gel method, and the photoluminescent properties of the resulting phosphors were intensively investigated. All samples can be excited efficiently by UV (395 nm) light and emit bright red light at 614 nm, which are coupled well with the characteristic emission from a UV-LED. In the Bi{sup 3+}-doped samples, the intensities of the main emission line ({sup 5}D{sub 0}–{sup 7}F{sub 2} transition at 614 nm) are strengthened because of the energy transition from Bi{sup 3+} to Eu{sup 3+}. With the substitution of Mo{sup 4+} by Si{sup 4+}, there are no significant changes in the emission peak positions, but the emission intensity was significantly enhanced under 395 nm excitation. Particularly, the LiEu{sub 0.9}Bi{sub 0.1}(Mo{sub 0.97}Si{sub 0.03}O{sub 4}){sub 2} phosphor doped with both Bi and Si demonstrates superior comprehensive photoluminescence properties with an excellent combination of easy excitation in the near UV range, bright emission intensity, high PL quantum efficiency as well as suitable decay time, which are very suitable for application as red phosphor for near UV

  12. LED Lighting – Modification of Growth, Metabolism, Yield and Flour Composition in Wheat by Spectral Quality and Intensity

    Directory of Open Access Journals (Sweden)

    István Monostori

    2018-05-01

    Full Text Available The use of light-emitting diode (LED technology for plant cultivation under controlled environmental conditions can result in significant reductions in energy consumption. However, there is still a lack of detailed information on the lighting conditions required for optimal growth of different plant species and the effects of light intensity and spectral composition on plant metabolism and nutritional quality. In the present study, wheat plants were grown under six regimens designed to compare the effects of LED and conventional fluorescent lights on growth and development, leaf photosynthesis, thiol and amino acid metabolism as well as grain yield and flour quality of wheat. Benefits of LED light sources over fluorescent lighting were manifested in both yield and quality of wheat. Elevated light intensities made possible with LEDs increased photosynthetic activity, the number of tillers, biomass and yield. At lower light intensities, blue, green and far-red light operated antagonistically during the stem elongation period. High photosynthetic activity was achieved when at least 50% of red light was applied during cultivation. A high proportion of blue light prolonged the juvenile phase, while the shortest flowering time was achieved when the blue to red ratio was around one. Blue and far-red light affected the glutathione- and proline-dependent redox environment in leaves. LEDs, especially in Blue, Pink and Red Low Light (RedLL regimens improved flour quality by modifying starch and protein content, dough strength and extensibility as demonstrated by the ratios of high to low molecular weight glutenins, ratios of glutenins to gliadins and gluten spread values. These results clearly show that LEDs are efficient for experimental wheat cultivation, and make it possible to optimize the growth conditions and to manipulate metabolism, yield and quality through modification of light quality and quantity.

  13. Noise analysis of a white-light supercontinuum light source for multiple wavelength confocal laser scanning fluorescence microscopy

    Energy Technology Data Exchange (ETDEWEB)

    McConnell, Gail [Centre for Biophotonics, Strathclyde Institute for Biomedical Sciences, University of Strathclyde, 27 Taylor Street, Glasgow, G4 0NR (United Kingdom)

    2005-08-07

    Intensity correlations of a Ti : sapphire, Kr/Ar and a white-light supercontinuum were performed to quantify the typical signal amplitude fluctuations and hence ascertain the comparative output stability of the white-light supercontinuum source for confocal laser scanning microscopy (CLSM). Intensity correlations across a two-pixel sample (n = 1000) of up to 98%, 95% and 94% were measured for the Ti : sapphire, Kr/Ar and white-light supercontinuum source, respectively. The white-light supercontinuum noise level is therefore acceptable for CLSM, with the added advantage of wider wavelength flexibility over traditional CLSM excitation sources. The relatively low-noise white-light supercontinuum was then used to perform multiple wavelength sequential CLSM of guinea pig detrusor to confirm the reliability of the system and to demonstrate system flexibility.

  14. Luminescence and the light emitting diode the basics and technology of leds and the luminescence properties of the materials

    CERN Document Server

    Williams, E W; Pamplin, BR

    2013-01-01

    Luminescence and the Light Emitting Diode: The Basics and Technology of LEDS and the Luminescence Properties of the Materials focuses on the basic physics and technology of light emitting diodes (LEDS) and pn junction lasers as well as their luminescence properties. Optical processes in semiconductors and the useful devices which can be made are discussed. Comprised of 10 chapters, this book begins with an introduction to the crystal structure and growth, as well as the optical and electrical properties of LED materials. The detailed fabrication of the LED is then considered, along with the lu

  15. A Complete MCDM Model for NPD Performance Assessment in an LED-Based Lighting Plant Factory

    Directory of Open Access Journals (Sweden)

    Wen-Chin Chen

    2018-01-01

    Full Text Available Globally, industries and economies have undergone rapid development and expansion over the last several decades. As a result, global warming and environmental contaminations have resulted in climate change and jeopardized food security. In many developing countries, already decreasing crop yields are threatened by extreme weather and soil damaged by genetically modified food, making environmental problems worse and increasing food and organic product prices. For these reasons, this study proposes a hybrid multicriteria decision-making (MCDM model for new product development (NPD in the light-emitting diode- (LED- based lighting plant factory. First, literature reviews and expert interviews are employed in constructing a list of decision-making objectives and criteria for new product development. Then, a fuzzy Delphi method (FDM is used to screen the elements of the objectives and criteria, while a fuzzy decision-making trial and evaluation laboratory (FDEMATEL is used to determine the relationships among the objectives and criteria. Finally, a fuzzy analytic network process (FANP and a composite priority vector (CPV are manipulated to determine the relative importance weights of the critical objectives and criteria. Results show that the proposed method can create a useful and assessable MCDM model for decision-making applications in new product development, and a case study is herein performed to validate the feasibility of the proposed model in a Taiwanese LED-based lighting plant factory, which not only provides the decision-makers with a feasible hierarchical data structure for decision-making guidance but also increases the competitive advantages of trade-offs on developing novel products.

  16. Infrared Video Pupillography Coupled with Smart Phone LED for Measurement of Pupillary Light Reflex.

    Science.gov (United States)

    Chang, Lily Yu-Li; Turuwhenua, Jason; Qu, Tian Yuan; Black, Joanna M; Acosta, Monica L

    2017-01-01

    Clinical assessment of pupil appearance and pupillary light reflex (PLR) may inform us the integrity of the autonomic nervous system (ANS). Current clinical pupil assessment is limited to qualitative examination, and relies on clinical judgment. Infrared (IR) video pupillography combined with image processing software offer the possibility of recording quantitative parameters. In this study we describe an IR video pupillography set-up intended for human and animal testing. As part of the validation, resting pupil diameter was measured in human subjects using the NeurOptics ™ (Irvine, CA, USA) pupillometer, to compare against that measured by our IR video pupillography set-up, and PLR was assessed in guinea pigs. The set-up consisted of a smart phone with a light emitting diode (LED) strobe light (0.2 s light ON, 5 s light OFF cycles) as the stimulus and an IR camera to record pupil kinetics. The consensual response was recorded, and the video recording was processed using a custom MATLAB program. The parameters assessed were resting pupil diameter (D1), constriction velocity (CV), percentage constriction ratio, re-dilation velocity (DV) and percentage re-dilation ratio. We report that the IR video pupillography set-up provided comparable results as the NeurOptics ™ pupillometer in human subjects, and was able to detect larger resting pupil size in juvenile male guinea pigs compared to juvenile female guinea pigs. At juvenile age, male guinea pigs also had stronger pupil kinetics for both pupil constriction and dilation. Furthermore, our IR video pupillography set-up was able to detect an age-specific increase in pupil diameter (female guinea pigs only) and reduction in CV (male and female guinea pigs) as animals developed from juvenile (3 months) to adult age (7 months). This technique demonstrated accurate and quantitative assessment of pupil parameters, and may provide the foundation for further development of an integrated system useful for clinical

  17. Broadcast of four HD videos with LED ceiling lighting: optical-wireless MAC

    Science.gov (United States)

    Bouchet, Olivier; Porcon, Pascal; Gueutier, Eric

    2011-09-01

    The European project "hOME Gigabit Access Network" (OMEGA) targeted various wireless and wired solutions for 1 Gbit/s connectivity in Home Area Networks (HANs). One objective was to evaluate the suitability of optical wireless technologies in two spectral regions: visible light (visible-light communications - VLC) and near infrared (infrared communications - IRC). Several demonstrators have been built, all of them largely relying on overthe- shelf components. The demonstrators included a "wide-area" VLC broadcast link based on LED ceiling lighting and a laser-based high-data-rate "wide-area" IRC prototype. In this paper we discuss an adapted optical-wireless media-access-control (OWMAC) sublayer, which was developed and implemented during the project. It is suitable for both IRC and VLC. The VLC prototype is based on DMT signal processing and provides broadcasting at { 100 Mbit/s over an area of approximately 5 m2. The IRC prototype provides {300 Mbit/s half-duplex communication over an area of approximately 30 m2. The IRC mesh network, composed of one base station and two terminals, is based on OOK modulation, multi-sector transceivers, and an ultra-fast sector switch. After a brief discussion about the design of the optical-wireless data link layer and the optical-wireless switch (OWS) card, we address the card development and implementation. We also present applications for the VLC and IRC prototypes and measurement results regarding the MAC layer.

  18. White light emitting diode as potential replacement of tungsten-halogen lamp for visible spectroscopy system: a case study in the measurement of mango qualities

    Science.gov (United States)

    Chiong, W. L.; Omar, A. F.

    2017-07-01

    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.

  19. White light emitting diode as potential replacement of tungsten-halogen lamp for visible spectroscopy system: a case study in the measurement of mango qualities

    International Nuclear Information System (INIS)

    Chiong, W.L.; Omar, A.F.

    2017-01-01

    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.

  20. Wideband perfect coherent absorber based on white-light cavity

    Science.gov (United States)

    Kotlicki, Omer; Scheuer, Jacob

    2015-03-01

    Coherent Perfect Absorbers (CPAs) are optical cavities which can be described as time-reversed lasers where light waves that enter the cavity, coherently interfere and react with the intra-cavity losses to yield perfect absorption. In contrast to lasers, which benefit from high coherency and narrow spectral linewidths, for absorbers these properties are often undesirable as absorption at a single frequency is highly susceptible to spectral noise and inappropriate for most practical applications. Recently, a new class of cavities, characterized by a spectrally wide resonance has been proposed. Such resonators, often referred to as White Light Cavities (WLCs), include an intra-cavity superluminal phase element, designed to provide a phase response with a slope that is opposite in sign and equal in magnitude to that of light propagation through the empty cavity. Consequently, the resonance phase condition in WLCs is satisfied over a band of frequencies providing a spectrally wide resonance. WLCs have drawn much attention due to their attractiveness for various applications such as ultra-sensitive sensors and optical buffering components. Nevertheless, WLCs exhibit inherent losses that are often undesirable. Here we introduce a simple wideband CPA device that is based on the WLC concept along with a complete analytical analysis. We present analytical and FDTD simulations of a practical, highly compact (12µm), Silicon based WLC-CPA that exhibits a flat and wide absorption profile (40nm) and demonstrate its usefulness as an optical pulse terminator (>35db isolation) and an all optical modulator that span the entire C-Band and exhibit high immunity to spectral noise.

  1. Tunable Eu.sup.2+./sup. emission in K.sub.x./sub.Na.sub.1./sub. − .sub.x./sub.LuS.sub.2./sub. phosphors for white LED application

    Czech Academy of Sciences Publication Activity Database

    Havlák, Lubomír; Jarý, Vítězslav; Bárta, Jan; Buryi, Maksym; Rejman, M.; Laguta, Valentyn; Nikl, Martin

    2016-01-01

    Roč. 106, Sep (2016), s. 363-370 ISSN 0264-1275 R&D Projects: GA MŠk LO1409; GA MŠk(CZ) LM2011029; GA TA ČR(CZ) TG02010056 Institutional support: RVO:68378271 Keywords : white LEDs * photoluminescence * Eu 2+ emission * circadian light sources * EPR Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 4.364, year: 2016

  2. Knoop hardness of ten resin composites irradiated with high-power LED and quartz-tungsten-halogen lights.

    Science.gov (United States)

    Price, Richard B T; Felix, Corey A; Andreou, Pantelis

    2005-05-01

    This study compared a high-power light-emitting-diode (LED) curing light (FreeLight 2, 3M ESPE) with a quartz-tungsten-halogen (QTH) light (TriLight, 3M ESPE) to determine which was the better at photo-polymerising 10 resin composites. Class I preparations were prepared 4-mm deep into human teeth and filled with 10 different composites. The composites were irradiated for 50% or 100% of their recommended times using the LED light, and for 100% of their recommended times with the QTH light on either the high or medium power setting. Fifteen minutes later, the Knoop hardness of the composites was measured to a depth of 3.5 mm from the surface. When irradiated by the LED light for their recommended curing times, the Knoop hardness of all 10 composites stayed above 80% of the maximum hardness of the composite to a depth of at least 1.5 mm; three composites maintained a Knoop hardness that was more than 80% of their maximum hardness to a depth of 3.5 mm. Repeated measurements analysis of variance indicated that all the two-way and three-way interactions between the curing light, depth, and composite were significant (p hardness values. The LED light, used for the composite manufacturer's recommended time, was ranked the best at curing the composites to a depth of 3mm (p power setting.

  3. Use of a supercontinuum white light in evaluating the spectral sensitivity of the pupil light reflex

    Science.gov (United States)

    Chin, Catherine; Leick, Lasse; Podoleanu, Adrian; Lall, Gurprit S.

    2018-03-01

    We assessed the spectral sensitivity of the pupillary light reflex in mice using a high power super continuum white light (SCWL) source in a dual wavelength configuration. This novel approach was compared to data collected from a more traditional setup using a Xenon arc lamp fitted with monochromatic interference filters. Irradiance response curves were constructed using both systems, with the added benefit of a two-wavelength, equivocal power, output using the SCWL. The variables applied to the light source were intensity, wavelength and stimulus duration through which the physiological output measured was the minimum pupil size attained under such conditions. We show that by implementing the SCWL as our novel stimulus we were able to dramatically increase the physiological usefulness of our pupillometry system.

  4. Fabrication of white light-emitting diodes based on UV light-emitting diodes with conjugated polymers-(CdSe/ZnS) quantum dots as hybrid phosphors.

    Science.gov (United States)

    Jung, Hyunchul; Chung, Wonkeun; Lee, Chang Hun; Kim, Sung Hyun

    2012-07-01

    White light-emitting diodes (LEDs) were fabricated using GaN-based 380-nm UV LEDs precoated with the composite of blue-emitting polymer (poly[(9,9-dihexylfluorenyl-2,7-diyl)-alt-co-(2-methoxy-5-{2-ethylhexyloxy)-1 ,4-phenylene)]), yellow green-emitting polymer (poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-benzo-{2,1',3}-thiadiazole)]), and 605-nm red-emitting quantum dots (QDs). CdSe cores were obtained by solvothermal route using CdO, Se precursors and ZnS shells were synthesized by using diethylzinc, and hexamethyldisilathiane precursors. The optical properties of CdSe/ZnS QDs were characterized by UV-visible and photoluminescence (PL) spectra. The structural data and composition of the QDs were transmission electron microscopy (TEM), and EDX technique. The quantum yield and size of the QDs were 58.7% and about 6.7 nm, respectively. Three-band white light was generated by hybridizing blue (430 nm), green (535 nm), and red (605 nm) emission. The color-rendering index (CRI) of the device was extremely improved by introducing the QDs. The CIE-1931 chromaticity coordinate, color temperature, and CRI of a white LED at 20 mA were (0.379, 0.368), 3969 K, and 90, respectively.

  5. Self-Excited Single-Stage Power Factor Correction Driving Circuit for LED Lighting

    Directory of Open Access Journals (Sweden)

    Yong-Nong Chang

    2014-01-01

    Full Text Available This pa\tper proposes a self-excited single-stage high power factor LED lighting driving circuit. Being featured with power factor correction capability without needing any control devices, the proposed circuit structure is with low cost and suitable for commercial production. The power factor correction function is accomplished by using inductor in combination with a half-bridge quasi resonant converter to achieve active switching and yield out voltage regulation according to load requirement. Furthermore, the zero-voltage switching in the half-bridge converter can be attained to promote the overall performance efficiency of the proposed circuit. Finally, the validity and production availability of the proposed circuit will be verified as well.

  6. Effect of Annealing Time of YAG:Ce3+ Phosphor on White Light Chromaticity Values

    Science.gov (United States)

    Abd, Husnen R.; Hassan, Z.; Ahmed, Naser M.; Almessiere, Munirah Abdullah; Omar, A. F.; Alsultany, Forat H.; Sabah, Fayroz A.; Osman, Ummu Shuhada

    2018-02-01

    Yttrium and aluminium nitrate phosphors doped with cerium nitrate and mixed with urea (fuel) are prepared by using microwave-induced combustion synthesis according to the formula Y(3-0.06)Al5O12:0.06Ce3+ (YAG:Ce3+) to produce white light emitting diodes by conversion from blue indium gallium nitride-light emitting diode chips. The sintering time with fixed temperature (1050°C) for phosphor powder was optimized and found to be 5 h. The crystallinity, structure, chemical composition, luminescent properties with varying currents densities and chromaticity were characterized by x-ray diffraction, field emission-scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, photoluminescence emission, electroluminescence and standard CIE 1931 chromaticity diagram, respectively. The energy levels of Ce3+ in YAG were discussed based on its absorption and excitation spectra. The results show that the obtained YAG:Ce3+ phosphor sintered for 5 h has good crystallinity with pure phase, low agglomerate with spherical shaped particles and strong yellow emission, offering cool-white LED with tuneable correlated color temperature and a good color rendering index compared to those prepared by sintering for 2 h and as-prepared phosphor powders.

  7. LED lighting and the Next Generation of Greenhouse for Tomatoes. Proof of Principle; LED belichting en Het Nieuwe Telen bij tomaat. Proof of Principle

    Energy Technology Data Exchange (ETDEWEB)

    Dueck, T.; Janse, J.; Eveleens, B. [Wageningen UR Glastuinbouw, Wageningen (Netherlands); Nieboer, S.; Valstar, W.; Grootscholten, M. [GreenQ Improvement Centre, Bleiswijk (Netherlands)

    2012-08-15

    In this Proof of Principle project a tomato crop was grown under artificial lighting with the aim of 30% energy saving at the same level of production. Tomatoes (cultivar Komeett) were illuminated with 110 {mu}mol m{sup -2} s{sup -1} HPS (High Pressure Sodium) above the crop and 85 {mu}mol m{sup -2} s{sup -1} LED interlighting. The LEDs hung in 2 rows, approximately 40 cm above the lower leaves and the second strand at 40 or 70 cm above that. There were two types of LEDs used: production LEDs (light efficiency 1.6 {mu}mol m{sup -2} s{sup -1}, 87% red/13% blue) and inter-lighting LEDs (light efficiency 1.9 {mu}mol m{sup -2} s{sup -1}, 95% red/5% blue), with the same light intensity. At the start, the crop was given as much light as it could handle, and because the crop developed so well, the stem density was increased relatively early. This resulted in high fruit load, while insufficient light was available to compensate for the low levels of sunlight in the winter. In the 192 cm row spacing system the plants were too close to each other. Additional problems occurred with trace elements, lesser bumble bee activity, and a moist greenhouse climate which weakened the crop in the winter. Thus Botrytis occurred on the leaves and stems. The crop struggled with its recovery until early spring with more sunlight. Compared to a reference crop with 79 kg m{sup -2} tomatoes, 75 kg m{sup -2} were produced under-production LEDs, and 80 kg m{sup -2} under the interlighting LEDs, mainly because latter LEDs were used longer during the summer. 30% of the energy for dehumidification and heat energy, and 27% of the electricity was saved, relative to the reference crop. Thus it appears possible to save 30% energy with a near identical production [Dutch] In dit Proof of Principle project is een belichte tomatenteelt geteeld met als doel 30% energiebesparing bij een gelijke productie. Tomaten van het ras Komeett werden belicht met 110 {mu}mol m{sup -2} s{sup -1} SON-T belichting boven

  8. Exposing broiler eggs to green, red and white light during incubation.

    Science.gov (United States)

    Archer, G S

    2017-07-01

    Previous work has shown that exposing broiler eggs to white light during incubation can improve hatchability and post-hatch animal welfare. It was hypothesized that due to how different wavelengths of light can affect avian physiology differently, and how pigmented eggshells filter light that different monochromatic wavelengths would have differential effects on hatchability and post-hatch animal welfare indicators. To determine, we incubated chicken eggs (n=6912) under either no light (dark), green light, red light or white light; the light level was 250 lux. White and red light were observed to increase hatch of fertile (P0.05). Fear response of during isolation and tonic immobility was reduced (P0.05) from dark incubated broilers. All light incubated broilers had lower (Phatchery efficiency and post-hatch animal welfare at the same time.

  9. Structured white light scanning of rabbit Achilles tendon.

    Science.gov (United States)

    Hayes, Alex; Easton, Katrina; Devanaboyina, Pavan Teja; Wu, Jian-Ping; Kirk, Thomas Brett; Lloyd, David

    2016-11-07

    The cross-sectional area (CSA) of a material is used to calculate stress under load. The mechanical behaviour of soft tissue is of clinical interest in the management of injury; however, measuring CSA of soft tissue is challenging as samples are geometrically irregular and may deform during measurement. This study presents a simple method, using structured light scanning (SLS), to acquire a 3D model of rabbit Achilles tendon in vitro for measuring CSA of a tendon. The Artec Spider™ 3D scanner uses structured light and stereophotogrammetry technologies to acquire shape data and reconstruct a 3D model of an object. In this study, the 3D scanner was integrated with a custom mechanical rig, permitting 360-degree acquisition of the morphology of six New Zealand White rabbit Achilles tendons. The reconstructed 3D model was then used to measure CSA of the tendon. SLS, together with callipers and micro-CT, was used to measure CSA of objects with a regular or complex shape, such as a drill flute and human cervical vertebra, for validating the accuracy and repeatability of the technique. CSA of six tendons was measured with a coefficient of variation of less than 2%. The mean CSA was 9.9±1.0mm 2 , comparable with those reported by other researchers. Scanning of phantoms demonstrated similar results to μCT. The technique developed in this study offers a simple and accurate method for effectively measuring CSA of soft tissue such as tendons. This allows for localised calculation of stress along the length, assisting in the understanding of the function, injury mechanisms and rehabilitation of tissue. Copyright © 2016 Elsevier Ltd. All rights reserved.

  10. Single-phased CaAl2Si2O8:Tm3+, Dy3+ white-light phosphors under ultraviolet excitation

    International Nuclear Information System (INIS)

    Yang, Penghui; Yu, Xue; Xu, Xuhui; Jiang, Tingming; Yu, Hongling; Zhou, Dacheng; Yang, Zhengwen; Song, Zhiguo; Qiu, Jianbei

    2013-01-01

    A novel white-light-emitting phosphor CaAl 2 Si 2 O 8 :Tm, Dy was synthesized in ambient atmosphere by solid-state reaction. The energy transfer from Tm 3+ to Dy 3+ ions via a dipole–quadrupole reaction was observed and investigated. Upon UV excitation, white light emission was achieved by integrating a blue emission band located at 455 nm and an orange one located at 574 nm attributed to Tm 3+ and Dy 3+ ions, respectively. In addition, the energy-transfer efficiency and critical distance were calculated. Results suggested that the phosphor might be promising as a single-phased white-light-emitting phosphor for UV white-light LED. - Graphical abstract: The results indicate the existence of energy transfer from Tm 3+ to Dy 3+ . By tuning the concentration of Dy 3+ , single-phased white light can be realized. - Highlights: ► Energy transfer from Tm 3+ to Dy 3+ was investigated. ► Color tunable from blue to white can be achieved. ► White light can be realized in CaAl 2 Si 2 O 8 :Tm 3+ , Dy 3+ phosphor

  11. Slow-mode degradation mechanism and its control in new bright and long-lived ZnSe white LEDs

    Energy Technology Data Exchange (ETDEWEB)

    Adachi, Masahiro [Venture Business Laboratory, Tottori University, 4-101 Koyama-Minami, Tottori 680-8552 (Japan); Ando, Koshi; Abe, Tomoki; Inoue, Noboru; Urata, Akihiro; Tsutsumi, Sueyuki; Hashimoto, Yutaka; Kasada, Hirofumi [Electrical and Electronic Department, Tottori University, 4-101 Koyama-Minami, Tottori 680-8552 (Japan); Katayama, Koji; Nakamura, Takao [Semiconductor Technologies R and D Laboratories, Sumitomo Electric Industries Ltd., 1-1-1 Koyakita, Itami, Hyogo, 665-0016 (Japan)

    2006-03-15

    This paper presents slow-mode degradation mechanism of ZnSe-based white LEDs. A systematic study has been made from a viewpoint of microscopic point defect reaction such as generation and migration in both device active layer (ZnCdSe/ZnSe MQW) and p-type ZnMgSSe cladding layer utilizing DLTS/ ICTS, SSRM (scanning spreading resistance microscope), and EL (electroluminescence)-imaging techniques, coupled with device aging experiments. We have found two different degradation stages (1st and 2nd stages) in the slow-mode degradation, which are caused by quite different microscopic point defect species. The 1st stage is induced by the long-diffusion of H0-center (nitrogen-complex deep hole trap in p-cladding layer), forming high-density dark-spots in the MQW active layer. This active center is generated only in the stress-stimulated condition such as thermal or device fabrication process. After controlling the initial concentration of the H0 center, we have observed no detectable new dark-spots during device operation, leading to fairly long device-lifetime ({proportional_to}1000 h). This 2nd stage has appeared as a carrier (hole) reduction in the p-type cladding layer. This final degradation stage is found to take place by an increase of shallow compensating donor-like centers in p-type cladding layer (ZnMgSSe). Based on these insights on the microscopic point defect reaction, we have developed (new) double cladding i-ZnMgBeSe/p-ZnMgSSe white-LEDs, which has exhibited long device lifetime of over 10000 h. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. WHITE-LIGHT FLARES ON CLOSE BINARIES OBSERVED WITH KEPLER

    International Nuclear Information System (INIS)

    Gao, Qing; Xin, Yu; Liu, Ji-Feng; Zhang, Xiao-Bin; Gao, Shuang

    2016-01-01

    Based on Kepler data, we present the results of a search for white light flares on 1049 close binaries. We identify 234 flare binaries, of which 6818 flares are detected. We compare the flare-binary fraction in different binary morphologies (“detachedness”). The result shows that the fractions in over-contact and ellipsoidal binaries are approximately 10%–20% lower than those in detached and semi-detached systems. We calculate the binary flare activity level (AL) of all the flare binaries, and discuss its variations along the orbital period ( P orb ) and rotation period ( P rot , calculated for only detached binaries). We find that the AL increases with decreasing P orb or P rot , up to the critical values at P orb ∼ 3 days or P rot ∼ 1.5 days, and thereafter the AL starts decreasing no matter how fast the stars rotate. We examine the flaring rate as a function of orbital phase in two eclipsing binaries on which a large number of flares are detected. It appears that there is no correlation between flaring rate and orbital phase in these two binaries. In contrast, when we examine the function with 203 flares on 20 non-eclipse ellipsoidal binaries, bimodal distribution of amplitude-weighted flare numbers shows up at orbital phases 0.25 and 0.75. Such variation could be larger than what is expected from the cross section modification.

  13. Performance evaluation of a vibration desensitized scanning white light interferometer

    International Nuclear Information System (INIS)

    Troutman, J; Evans, C J; Ganguly, V; Schmitz, T L

    2014-01-01

    Surface metrology instruments normally require thermal, seismic and acoustic isolation. Shop-floor metrology solutions offer reduced cost and process time. If they operate on the same principles as laboratory devices, an inherent sensitivity to vibration remains. This paper describes a methodology for evaluating ‘environmental tolerance’ and applying it to characterize a recently introduced ‘environmentally tolerant’ scanning white light interferometer (SWLI). Previously published measurements of replicated nickel reference standards on the new instrument and on a stylus profilometer showed good correlation. Surface topography repeatabilities (per ISO 25178-604:2013) were insignificantly different when evaluated on the SWLI instrument in a metrology laboratory and in a manufacturing area. Measurements of reference standards under forced vibration of the entire instrument show maximum ripple error and data dropout in regions of structural resonance. Measurements were performed with large forced horizontal and vertical sample oscillation beneath the objective, exhibiting maximum ripple error near odd integer multiples of half the instrument detector frequency. Error due to data dropout was also investigated. (paper)

  14. White electroluminescence from ZnO nanorods/p-GaN heterojunction light-emitting diodes under reverse bias

    International Nuclear Information System (INIS)

    Zhang, Lichun; Li, Qingshan; Qu, Chong; Zhang, Zhongjun; Huang, Ruizhi; Zhao, Fengzhou

    2013-01-01

    Heterojunction light-emitting diodes (LEDs) based on arrays of ZnO nanorods were fabricated on p-GaN films by the hydrothermal method. Without any phosphors, white-light electroluminescence (EL) from ZnO nanorods/p-GaN heterojunction LEDs operated at reverse breakdown bias was observed. The EL spectra are composed of an ultraviolet (UV) emission centered at 382 nm, a blue light located at 431 nm and a broadband yellow–green light at around 547 nm, which originated from band-edge emission in ZnO, the Mg acceptor levels in p-GaN and the deep-level states near the ZnO/GaN interface, respectively. The chromaticity coordinates of EL spectrum are very close to the (0.333, 0.333) of standard white light. The origin of these emissions has been discussed and the tunneling effect in the interface is probably the mechanism to explain EL emission. (paper)

  15. Artificial LED lighting enhances growth characteristics and total phenolic content of Ocimum basilicum, but variably affects transplant success

    NARCIS (Netherlands)

    Bantis, Filippos; Ouzounis, Theoharis; Radoglou, Kalliopi

    2016-01-01

    The morphological and phytochemical characteristics of two Ocimum basilicum cultivars (Lettuce Leaf, and Red Rubin-mountain Athos hybrid) under artificial lighting were investigated. Four LED light treatments [AP673L (high red and high red:far-red), G2 (high red and low red:far-red), AP67

  16. Off-grid energy services for the poor: Introducing LED lighting in the Millennium Villages Project in Malawi

    International Nuclear Information System (INIS)

    Adkins, Edwin; Eapen, Sandy; Kaluwile, Flora; Nair, Gautam; Modi, Vijay

    2010-01-01

    Lanterns that use light-emitting diodes (LEDs) powered by batteries, which are in turn charged by grid electricity or small solar panels, have emerged as a cost-competitive alternative to kerosene and other fuel-based lighting technologies, offering brighter light for longer duration at equal or lower cost over time. This paper presents lessons learned from the introduction of solar LED lanterns in rural Malawi. We discuss a market-based program using new and existing local commercial structures such as vendors and cooperatives to sell lanterns to village households without subsidy. The paper addresses issues of enterprise development, community interactions, and survey data on lighting use and expenditure patterns before and after LED lantern introduction. Households that purchased a lantern reported high levels of satisfaction with the LED lanterns as well as savings in annual kerosene expenditure comparable to the price of the lantern. These households also reported monthly incomes comparable to the price of the LED lanterns whereas non-adopters surveyed reported monthly incomes about half this level, suggesting a need for financing options to maximize adoption among poorer populations in rural areas. These results suggest that similar market based models of LED lighting technology dissemination have the potential to be replicated and scaled up in other off-grid regions in developing countries. However, viability of local cooperatives and supply chains for lantern products over the medium-to-long term remain to be assessed.

  17. The performance of quantum dots-based white light-emitting diodes

    Science.gov (United States)

    Chen, Kuan-Lin; Chung, Shu-Ru

    2017-08-01

    Recently, the investigation of quantum dots (QDs) as a color converter for white light-emitting diodes (WLEDs) application has attracted a great deal of attention. Because the narrow emission wavelength of QDs can be controlled by their particle sizes and compositions, which is facilitated to improve the color gamut of display as well as color rendering index (CRI) and the correlated color temperature (CCT) of WLEDs. In a typical commercially available LCD display, the color gamut is approximately to 75 % which is defined by the National Television System Committee (NTSC). In order to enhance NTSC, the full width at half-maximum (FWHM) of color converter should be less than 30 nm. Therefore, the QDs are the best choice for display application due to the FWHM of QDs is meet the demand of display application. In this study, the hot injection method with one-pot process is used to synthesis of colloidal ternary ZnCdSe green (G-) and red-emission (R-) QDs with a narrow emission wavelength around 537 and 610 nm. By controlling the complex reagents-stearic acid (SA) and lauric acid (LA), high performance of G- and R-QDs can be prepared. The quantum yields (QYs), particle sizes and FWHM for G- and R-QDs are 70, 30 %, 3.2 +/- 0.5, 4.1 +/- 0.5 nm and 25, 26 nm, respectively. In order to explore the performance of QDs-based WLEDs, mixing ratios effect between G-QD and R-QD are studied and the WLED is packed as conformal-type. Different ratios of R-QD and G-QD (1:10, 1:20 and 1:30) are mixed and fill up the 3020 SMD blue-InGaN LED, and named as LED-10, LED-20 and LED-30. After that, UV curable gel is deposited on the top of QD layer to form WLED and named as LED-10*, LED-20* and LED-30*. The results show that the Commission International d'Eclairage (CIE) chromaticity coordinates, color rendering index (CRI), luminous efficacy of LED-10*, LED-20* and LED-30* are (0.27, 0.21), 53, 1.9 lm/W, (0.29, 0.30), 72, 3.3 lm/W and (0.25, 0.34), 45, 6.8 lm/W, respectively. We can find

  18. Luminescence properties and energy transfer of site-sensitive Ca(6-x-y)Mg(x-z)(PO(4))(4):Eu(y)(2+),Mn(z)(2+) phosphors and their application to near-UV LED-based white LEDs.

    Science.gov (United States)

    Kwon, Ki Hyuk; Im, Won Bin; Jang, Ho Seong; Yoo, Hyoung Sun; Jeon, Duk Young

    2009-12-21

    On the basis of the structural information that the host material has excellent charge stabilization, blue-emitting Ca(6-x-y)Mg(x)(PO(4))(4):Eu(y)(2+) (CMP:Eu(2+)) phosphors were synthesized and systematically optimized, and their photoluminescence (PL) properties were evaluated. Depending upon the amount of Mg added, the emission efficiency of the phosphors could be enhanced. The substitution of Eu(2+) affected their maximum wavelength (lambda(max)) and thermal stability because the substitution site of Eu(2+) could be varied. To obtain single-phase two-color-emitting phosphors, we incorporated Mn(2+) into CMP:Eu(2+) phosphors. Weak red emission resulting from the forbidden transition of Mn(2+) could be enhanced by the energy transfer from Eu(2+) to Mn(2+) that occurs because of the spectral overlap between the photoluminescence excitation (PLE) spectrum of Mn(2+) and the PL spectrum of Eu(2+). The energy transfer process was confirmed by the luminescence spectra, energy transfer efficiency, and decay curve of the phosphors. Finally, the optimized Ca(6-x-y)Mg(x-z)(PO(4))(4):Eu(y)(2+),Mn(z)(2+) (CMP:Eu(2+),Mn(2+)) phosphors were applied with green emitting Ca(2)MgSi(2)O(7):Eu(2+) (CMS:Eu(2+)) phosphors to ultraviolet (UV) light emitting diode (LED)-pumped white LEDs. The CMS:Eu(2+)-mixed CMP:Eu(2+), Mn(2+)-based white LEDs showed an excellent color rendering index (CRI) of 98 because of the broader emission band and more stable color coordinates than those of commercial Y(3)Al(5)O(12):Ce(3+) (YAG:Ce(3+))-based white LEDs under a forward bias current of 20 mA. The fabricated white LEDs showed very bright natural white light that had the color coordinate of (0.3288, 0.3401), and thus CMP:Eu(2+),Mn(2+) could be regarded as a good candidate for UV LED-based white LEDs.

  19. Non-doped-type white organic light-emitting diodes for lighting purpose

    Energy Technology Data Exchange (ETDEWEB)

    Zhu Jianzhuo [Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China); Graduate School of Chinese Academy of Sciences, Beijing 100039 (China); Li Wenlian, E-mail: wllioel@yahoo.com.c [Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China); Chu Bei, E-mail: beichu@163.co [Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China); Yan Fei; Yang Dongfang; Liu Huihui; Wang Junbo [Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China); Graduate School of Chinese Academy of Sciences, Beijing 100039 (China)

    2010-05-15

    We demonstrate a non-doped white organic light-emitting diode (WOLED) in which the blue-, green- and red-emissions are generated from 4,4'-bis(2,2'-diphenylvinyl)-1,1'-biphenyl, tris(8-hydroxyquinoline)aluminum (Alq) and 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyl-julolidyl 9-enyl)-4H-pyran (DCJTB), which is used as an ultrathin layer. The DCJTB ultrathin layer plays the chromaticity tuning role in optimizing the white spectral band by modulating the location of the DCJTB ultrathin layer in the green emissive Alq layer. The optimized WOLED gives the Commission Internationale de l'Eclairage-1931 xy coordinates of (0.319, 0.335), a color rendering index of 91.2 at 10 V, a maximum brightness of 21010 cd/m{sup 2} at 12 V and a maximum current efficiency of 5.17 cd/A at 6.6 V. The electroluminescence mechanism of the white device is also discussed.

  20. Green LED as an Effective Light Source for Curing Acrylate-Based Dental Resins in Combination with Irgacure 784

    Directory of Open Access Journals (Sweden)

    Katalin Bukovinszky

    2018-01-01

    Full Text Available Low intensity green light emitting diodes (LED were shown to be an effective light source to induce the photopolymerization of an acrylate-based photocurable dental restorative resin mixture of bisphenol A glycerolate dimethacrylate (BisGMA, triethylene glycol dimethacrylate (TEGDMA, and diurethane dimethacrylate (UDMA, in combination with fluorinated diaryl titanocene (Irgacure 784. Dental matrices were prepared by the LED light source at different intensities. The mechanical properties, such as Vickers microhardness, compressive strength, diametric tensile strength, flexural strength, and E-modulus of the created samples, were investigated. The kinetics of the photopolymerization was followed by Raman spectroscopy and conversion values were determined. It was found that, despite its narrow-emission range centered at a wavelength of 531 nm, the green LED light source is suitable for the preparation of dental matrices with good mechanical properties and high conversion values.

  1. Human phase response curve to a 1 h pulse of bright white light

    Science.gov (United States)

    St Hilaire, Melissa A; Gooley, Joshua J; Khalsa, Sat Bir S; Kronauer, Richard E; Czeisler, Charles A; Lockley, Steven W

    2012-01-01

    The phase resetting response of the human circadian pacemaker to light depends on the timing of exposure and is described by a phase response curve (PRC). The current study aimed to construct a PRC for a 1 h exposure to bright white light (∼8000 lux) and to compare this PRC to a dim background light PRC. These data were also compared to a previously completed 6.7 h bright white light PRC and a dim background light PRC constructed under similar conditions. Participants were randomized for exposure to 1 h of either bright white light (n= 18) or dim background light (n= 18) scheduled at 1 of 18 circadian phases. Participants completed constant routine (CR) procedures in dim light (light exposure to assess circadian phase. Phase shifts were calculated as the difference in timing of dim light melatonin onset (DLMO) during pre- and post-stimulus CRs. Exposure to 1 h of bright white light induced a Type 1 PRC with a fitted peak-to-trough amplitude of 2.20 h. No discernible PRC was observed in the dim background light PRC. The fitted peak-to-trough amplitude of the 1 h bright light PRC was ∼40% of that for the 6.7 h PRC despite representing only 15% of the light exposure duration, consistent with previous studies showing a non-linear duration–response function for the effects of light on circadian resetting. PMID:22547633

  2. Host sensitized novel red phosphor CaZrSi{sub 2}O{sub 7} : Eu{sup 3+} for near UV and blue LED-based white LEDs

    Energy Technology Data Exchange (ETDEWEB)

    Bandi, Vengala Rao; Jeong, Junho; Jang, Kiwan; Lee, Ho Sueb [Department of Physics, Changwon National University, Changwon 641-773 (Korea, Republic of); Jayasimhadri, M [Department of Applied Physics, Delhi Technological University, Delhi (India); Yi, Soung-Soo [Department of Photonics, Silla University, Busan (Korea, Republic of); Jeong, Jung-Hyun, E-mail: kwjang@changwon.ac.k [Department of Physics, Pukyong National University, Busan (Korea, Republic of)

    2010-10-06

    A series of red phosphors Ca{sub 1-x}ZrSi{sub 2}O{sub 7} : Eu{sub x} (x = 0.5,1,5,10,12 mol%) were prepared by a solid-state reaction technique at various temperatures and their structural and optical properties were investigated. The x-ray diffraction profiles showed that all peaks could be attributed to the monoclinic phase CaZrSi{sub 2}O{sub 7} doped with Eu{sup 3+}. SEM, FTIR, TG and DTA profiles have also been characterized to explore their structural properties. The luminescence properties of these resulting phosphors have been characterized by photoluminescence spectra. The host matrix itself has shown a strong blue emission which has its maximum intensity at 470 nm. The excitation spectra of CaZrSi{sub 2}O{sub 7} : Eu{sup 3+} revealed two excitation bands at 395 and 464 nm which correspond to the sharp {sup 7}F{sub 0}-{sup 5}L{sub 6} and {sup 7}F{sub 0}-{sup 5}D{sub 2} transitions of Eu{sup 3+} and matches well with the two popular emissions from n-UV/blue GaN-based LEDs. The prominent red emission was obtained at 615 nm by the excitation transitions {sup 5}L{sub 6}, {sup 5}D{sub 2} of Eu{sup 3+} through the non-radiative energy transfer process from the host to the Eu{sup 3+} ion. The effects of charge compensation by monovalent ions on the luminescence behaviour of a red emitting phosphor CaZrSi{sub 2}O{sub 7} : Eu{sup 3+} were investigated. The high colour saturation and the low thermal quenching effect of these phosphors make it a potential red component for white light emitting diodes (w-LEDs).

  3. White-emission in single-phase Ba2Gd2Si4O13:Ce3 +,Eu2 +,Sm3 + phosphor for white-LEDs

    Science.gov (United States)

    Jiang, Xiumin; Zhang, Yuqian; Zhang, Jia

    2018-03-01

    To develop new white-light-emitting phosphor, a series of Ce3 +-Eu2 +-Sm3 + doped Ba2Gd2Si4O13 (BGS) phosphors were prepared by the solid-state reaction method, and their photoluminescence properties were studied. The Ce3 + and Eu2 + single-doped BGS show broad emission bands around in the region of 350-550 and 420-650 nm, respectively. By co-doping Ce3 +-Eu2 + into BGS, the energy transfer (ET) from Ce3 + to Eu2 + is inefficient, which could be due to the competitive absorption between the two activator ions. The Sm3 +-activated BGS exhibits an orangey-red emission in the region of 550-750 nm. To achieve white emission, the BGS:0.06Ce3 +,0.04Eu2 +,ySm3 + (0 ≤ y ≤ 0.18) phosphors were designed, in which the ET from Ce3 +/Eu2 + to Sm3 + was observed. The emission color can be tuned by controlling the Sm3 + concentration, and white emission was obtained in the BGS:0.06Ce3 +,0.04Eu2 +,0.06Sm3 + sample. The investigation of thermal luminescence stability for the typical BGS:0.06Ce3 +,0.04Eu2 +,0.06Sm3 + sample reveals that the emission intensities of both Eu2 + and Sm3 + demonstrate continuous decrease but the Ce3 + emission is enhanced gradually with increasing temperature. The corresponding reason has been discussed.

  4. Disparity in Cutaneous Pigmentary Response to LED vs Halogen Incandescent Visible Light: Results from a Single Center, Investigational Clinical Trial Determining a Minimal Pigmentary Visible Light Dose.

    Science.gov (United States)

    Soleymani, Teo; Cohen, David E; Folan, Lorcan M; Okereke, Uchenna R; Elbuluk, Nada; Soter, Nicholas A

    2017-11-01

    Background: While most of the attention regarding skin pigmentation has focused on the effects of ultraviolet radiation, the cutaneous effects of visible light (400 to 700nm) are rarely reported. The purpose of this study was to investigate the cutaneous pigmentary response to pure visible light irradiation, examine the difference in response to different sources of visible light irradiation, and determine a minimal pigmentary dose of visible light irradiation in melanocompetent subjects with Fitzpatrick skin type III - VI. The study was designed as a single arm, non-blinded, split-side dual intervention study in which subjects underwent visible light irradiation using LED and halogen incandescent light sources delivered at a fluence of 0.14 Watts/cm2 with incremental dose progression from 20 J/cm2 to 320 J/cm2. Pigmentation was assessed by clinical examination, cross-polarized digital photography, and analytic colorimetry. Immediate, dose-responsive pigment darkening was seen with LED light exposure in 80% of subjects, beginning at 60 Joules. No pigmentary changes were seen with halogen incandescent light exposure at any dose in any subject. This study is the first to report a distinct difference in cutaneous pigmentary response to different sources of visible light, and the first to demonstrate cutaneous pigment darkening from visible LED light exposure. Our findings raise the concern that our increasing daily artificial light surroundings may have clandestine effects on skin biology. J Drugs Dermatol. 2017;16(11):1105-1110..

  5. High power light emitting diode (LED) arrays versus halogen light polymerization of oral biomaterials: Barcol hardness, compressive strength and radiometric properties.

    Science.gov (United States)

    Mills, Robin W; Uhl, Alexander; Blackwell, Gordon B; Jandt, Klaus D

    2002-07-01

    The clinical performance of light polymerized dental composites is greatly influenced by the quality of the light curing unit (LCU) used. Commonly used halogen LCUs have some specific drawbacks such as decreasing light output with time. This may result in a low degree of monomer conversion of the composites with negative clinical implications. Previous studies have shown that blue light emitting diode (LED) LCUs have the potential to polymerize dental composites without having the drawbacks of halogen LCUs. Since these studies were carried out LED technology has advanced significantly and commercial LED LCUs are now becoming available. This study investigates the Barcol hardness as a function of depth, and the compressive strength of dental composites that had been polymerized for 40 or 20s with two high power LED LCU prototypes, a commercial LED LCU, and a commercial halogen LCU. In addition the radiometric properties of the LCUs were characterized. The two high power prototype LED LCUs and the halogen LCU showed a satisfactory and similar hardness-depth performance whereas the hardness of the materials polymerized with the commercial LED LCU rapidly decreased with sample depth and reduced polymerization time (20 s). There were statistically significant differences in the overall compressive strengths of composites polymerized with different LCUs at the 95% significance level (p = 0.0016) with the two high power LED LCU prototypes and the halogen LCU forming a statistically homogenous group. In conclusion, LED LCU polymerization technology can reach the performance level of halogen LCUs. One of the first commercial LED LCUs however lacked the power reserves of the high power LED LCU prototypes.

  6. Green light drives leaf photosynthesis more efficiently than red light in strong white light: revisiting the enigmatic question of why leaves are green.

    Science.gov (United States)

    Terashima, Ichiro; Fujita, Takashi; Inoue, Takeshi; Chow, Wah Soon; Oguchi, Riichi

    2009-04-01

    The literature and our present examinations indicate that the intra-leaf light absorption profile is in most cases steeper than the photosynthetic capacity profile. In strong white light, therefore, the quantum yield of photosynthesis would be lower in the upper chloroplasts, located near the illuminated surface, than that in the lower chloroplasts. Because green light can penetrate further into the leaf than red or blue light, in strong white light, any additional green light absorbed by the lower chloroplasts would increase leaf photosynthesis to a greater extent than would additional red or blue light. Based on the assessment of effects of the additional monochromatic light on leaf photosynthesis, we developed the differential quantum yield method that quantifies efficiency of any monochromatic light in white light. Application of this method to sunflower leaves clearly showed that, in moderate to strong white light, green light drove photosynthesis more effectively than red light. The green leaf should have a considerable volume of chloroplasts to accommodate the inefficient carboxylation enzyme, Rubisco, and deliver appropriate light to all the chloroplasts. By using chlorophylls that absorb green light weakly, modifying mesophyll structure and adjusting the Rubisco/chlorophyll ratio, the leaf appears to satisfy two somewhat conflicting requirements: to increase the absorptance of photosynthetically active radiation, and to drive photosynthesis efficiently in all the chloroplasts. We also discuss some serious problems that are caused by neglecting these intra-leaf profiles when estimating whole leaf electron transport rates and assessing photoinhibition by fluorescence techniques.

  7. Energy transfer and colour tunability in UV light induced Tm3+/Tb3+/Eu3+: ZnB glasses generating white light emission.

    Science.gov (United States)

    Naresh, V; Gupta, Kiran; Parthasaradhi Reddy, C; Ham, Byoung S

    2017-03-15

    A promising energy transfer (Tm 3+ →Tb 3+ →Eu 3+ ) approach is brought forward to generate white light emission under ultraviolet (UV) light excitation for solid state lightening. Tm 3+ /Tb 3+ /Eu 3+ ions are combinedly doped in zinc borate glass system in view of understanding energy transfer process resulting in white light emission. Zinc borate (host) glass displayed optical and luminescence properties due to formation of Zn(II) x -[O(-II)] y centres in the ZnB glass matrix. At 360nm (UV) excitation, triply doped Tm 3+ /Tb 3+ /Eu 3+ : ZnB glasses simultaneously shown their characteristic emission bands in blue (454nm: 1 D 2 → 3 F 4 ), green (547nm: 5 D 4 → 7 F 5 ) and red (616nm: 5 D 0 → 7 F 2 ) regions. In triple ions doped glasses, energy transfer dynamics is discussed in terms of Forster-Dexter theory, excitation & emission profiles, lifetime curves and from partial energy level diagram of three ions. The role of Tb 3+ in ET from Tm 3+ →Eu 3+ was discussed using branch model. From emission decay analysis, energy transfer probability (P) and efficiency (η) were evaluated. Colour tunability from blue to white on varying (Tb 3+ , Eu 3+ ) content is demonstrated from Commission Internationale de L'Eclairage (CIE) chromaticity coordinates. Based on chromaticity coordinates, other colour related parameters like correlated colour temperature (CCT) and colour purity are also computed for the studied glass samples. An appropriate blending of such combination of rare earth ions could show better suitability as potential candidates in achieving multi-colour and warm/cold white light emission for white LEDs application in the field of solid state lightening. Copyright © 2016 Elsevier B.V. All rights reserved.

  8. Computer numerical control (CNC) lithography: light-motion synchronized UV-LED lithography for 3D microfabrication

    International Nuclear Information System (INIS)

    Kim, Jungkwun; Allen, Mark G; Yoon, Yong-Kyu

    2016-01-01

    This paper presents a computer-numerical-controlled ultraviolet light-emitting diode (CNC UV-LED) lithography scheme for three-dimensional (3D) microfabrication. The CNC lithography scheme utilizes sequential multi-angled UV light exposures along with a synchronized switchable UV light source to create arbitrary 3D light traces, which are transferred into the photosensitive resist. The system comprises a switchable, movable UV-LED array as a light source, a motorized tilt-rotational sample holder, and a computer-control unit. System operation is such that the tilt-rotational sample holder moves in a pre-programmed routine, and the UV-LED is illuminated only at desired positions of the sample holder during the desired time period, enabling the formation of complex 3D microstructures. This facilitates easy fabrication of complex 3D structures, which otherwise would have required multiple manual exposure steps as in the previous multidirectional 3D UV lithography approach. Since it is batch processed, processing time is far less than that of the 3D printing approach at the expense of some reduction in the degree of achievable 3D structure complexity. In order to produce uniform light intensity from the arrayed LED light source, the UV-LED array stage has been kept rotating during exposure. UV-LED 3D fabrication capability was demonstrated through a plurality of complex structures such as V-shaped micropillars, micropanels, a micro-‘hi’ structure, a micro-‘cat’s claw,’ a micro-‘horn,’ a micro-‘calla lily,’ a micro-‘cowboy’s hat,’ and a micro-‘table napkin’ array. (paper)

  9. Trivalent europium-doped strontium molybdate red phosphors in white light-emitting diodes: Synthesis, photophysical properties and theoretical calculations

    International Nuclear Information System (INIS)

    Yang, W.-Q.; Liu, H.-G.; Liu, G.-K.; Lin, Y.; Gao, M.; Zhao, X.-Y.; Zheng, W.-C.; Chen, Y.; Xu, J.; Li, L.-Z.

    2012-01-01

    Eu 3+ -doped strontium molybdate red phosphors (Sr 1−x MoO 4 :Eu x (x = 0.01–0.2)) for white light-emitting diodes (LED) were synthesized by the solid-state reaction method. The fluorescent intensities of the as-prepared phosphors were remarkably improved. The excitation and emission spectra demonstrate that these phosphors can be effectively excited by the near-UV light (395 nm) and blue light (466 nm). Their emitted red light peaks are located at 613 nm, and the highest quantum yield value (η) of the as-grown red phosphor, which is 95.85%, is much higher than that of commercial red phosphor (77.53%). These red phosphors plus commercial yellow powers (1:10) were successfully packaged with the GaN-based blue chips on a piranha frame by epoxy resins. The encapsulated white LED lamps show high performance of the CIE chromaticity coordinates and color temperatures. Moreover, to explain the fluorescent spectra of these phosphors, a complete 3003 × 3003 energy matrix was successfully built by an effective operator Hamiltonian including free ion and crystal field interactions. For the first time, the fluorescent spectra for Eu 3+ ion at the tetragonal (S 4 ) Sr 2+ site of SrMoO 4 crystal were calculated from a complete diagonalization (of energy matrix) method. The fitting values are close to the experimental results.

  10. Demonstration Assessment of Light-Emitting Diode (LED) Parking Lot Lighting at T.J.Maxx in Manchester, NH Phase I

    Energy Technology Data Exchange (ETDEWEB)

    Myer, Michael; Goettel, Russell T.

    2010-06-29

    A report describing the process and results of replacing existing parking lot lighting, looking at a LED option with occupancy sensors, and conventional alternates. Criteria include payback, light levels, occupant satisfaction. This report is Phase I of II. Phase I deals with initial installation.

  11. White organic light emitting diodes based on DCM dye sandwiched in 2-methyl-8-hydroxyquinolinolatolithium

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Amit [Center for Organic Electronics, Polymeric and Soft Materials Section, National Physical Laboratory (Council of Scientific and Industrial Research), Dr. K.S. Krishnan Road, New Delhi 110012 (India); Department of Chemistry, M.D. University, Rohtak, Haryana 124001 (India); Srivastava, Ritu, E-mail: ritu@mail.nplindia.ernet.i [Center for Organic Electronics, Polymeric and Soft Materials Section, National Physical Laboratory (Council of Scientific and Industrial Research), Dr. K.S. Krishnan Road, New Delhi 110012 (India); Bawa, Sukhwant S. [Center for Organic Electronics, Polymeric and Soft Materials Section, National Physical Laboratory (Council of Scientific and Industrial Research), Dr. K.S. Krishnan Road, New Delhi 110012 (India); Singh, Devender; Singh, Kapoor [Department of Chemistry, M.D. University, Rohtak, Haryana 124001 (India); Chauhan, Gayatri [Center for Organic Electronics, Polymeric and Soft Materials Section, National Physical Laboratory (Council of Scientific and Industrial Research), Dr. K.S. Krishnan Road, New Delhi 110012 (India); Singh, Ishwar [Department of Chemistry, M.D. University, Rohtak, Haryana 124001 (India); Kamalasanan, Modeeparampil N. [Center for Organic Electronics, Polymeric and Soft Materials Section, National Physical Laboratory (Council of Scientific and Industrial Research), Dr. K.S. Krishnan Road, New Delhi 110012 (India)

    2010-08-15

    Stable white electroluminescence (EL) has been achieved from organic LED, in which an ultrathin 4-(dicyanomethylene)-2-methyl-6-(p-dimethyl-aminostyryl)-4H-pyran (DCM) dye layer has been inserted in between two 2-methyl-8-hydroxyquinolinolatolithium [LiMeq] emitter layer and by optimizing the position of the DCM dye layer from the {alpha}-NPD/LiMeq interface. Electroluminescence spectra, current-voltage-luminescence (I-V-L) characteristics of the devices have been studied by changing the position of the dye layer. As the distance of DCM layer from {alpha}-NPD/LiMeq interface is increased, the intensity of host emission enhances rapidly. Introduction of thin layer of DCM in emissive layer increases the turn on voltage. The best Commission International de L' Eclairage (CIE) coordinates i.e. (0.32, 0.33) were obtained with device structure ITO/{alpha}-NPD(30 nm) /LiMeq(10 nm)/DCM(1 nm)/LiMeq(25 nm)/BCP(6 nm)/Alq{sub 3}(28 nm)/LiF(1 nm)/Al(100 nm). The EL spectrum covers the whole visible spectra range 400-700 nm. The color rendering index (CRI) for our best white light (Device 4) is 47.4. The device shows very good color stability in terms of CIE coordinates with voltages. The maximum luminescence 1240 cd/m{sup -2} has been achieved at 19 V.

  12. Thermal characterizations analysis of high-power ThinGaN cool-white light-emitting diodes

    Science.gov (United States)

    Raypah, Muna E.; Devarajan, Mutharasu; Ahmed, Anas A.; Sulaiman, Fauziah

    2018-03-01

    Analysis of thermal properties plays an important role in the thermal management of high-power (HP) lighting-emitting diodes (LEDs). Thermal resistance, thermal capacitance, and thermal time constant are essential parameters for the optimal design of the LED device and system, particularly for dynamic performance study. In this paper, thermal characterization and thermal time constant of ThinGaN HP LEDs are investigated. Three HP cool-white ThinGaN LEDs from different manufacturers are used in this study. A forward-voltage method using thermal transient tester (T3Ster) system is employed to determine the LEDs' thermal parameters at various operating conditions. The junction temperature transient response is described by a multi-exponential function model to extract thermal time constants. The transient response curve is divided into three layers and expressed by three exponential functions. Each layer is associated with a particular thermal time constant, thermal resistance, and thermal capacitance. It is found that the thermal time constant of LED package is on the order of 22 to 100 ms. Comparison between the experimental results is carried out to show the design effects on thermal performance of the LED package.

  13. Illuminating the Pecking Order in Off-Grid Lighting: A Demonstration of LED Lighting for Saving Energy in the Poultry Sector

    Energy Technology Data Exchange (ETDEWEB)

    Tracy, Jennifer; Mills, Evan

    2010-11-06

    The Lumina Project and Lighting Africa conducted a full-scale field test involving a switch from kerosene to solar-LED lighting for commercial broiler chicken production at an off-grid farm in Kenya. The test achieved lower operating costs, produced substantially more light, improved the working environment, and had no adverse effect on yields. A strategy using conventional solar-fluorescent lighting also achieved comparable yields, but entailed a six-fold higher capital cost and significantly higher recurring battery replacement costs. Thanks to higher energy and optical efficiencies, the LED system provided approximately twice the illumination to the chicken-production area and yet drew less than half the power.At the study farm, 3000 chickens were grown in each of three identical houses under kerosene, fluorescent, and LED lighting configurations. Under baseline conditions, a yearly expenditure of 1,200 USD is required to illuminate the three houses with kerosene. The LED system eliminates this fuel use and expense with a corresponding simple payback time of 1.5 years, while the solar-fluorescent system has a payback time of 9.3 years. The corresponding reduction in fuel expenditure in both cases represents a 15percent increase in after-tax net income (revenues minus expenses) across the entire business operation. The differential cost-effectiveness between the LED and fluorescent systems would be substantially greater if the fluorescent system were upsized to provide the same light as the LED system. Providing light with the fluorescent or LED systems is also far more economical than connecting to the grid in this case. The estimated grid-connection cost at this facility is 1.7 million Kenya Schillings (approximately 21,250 USD), which is nearly six-times the cost of the fluorescent system and 35-times the cost of the LED system.The LED system also confers various non-energy benefits. The relative uniformity of LED lighting, compared to the fluorescent or

  14. A new LED lamp for the collection of nocturnal Lepidoptera and a spectral comparison of light-trapping lamps

    OpenAIRE

    Brehm, Gunnar

    2017-01-01

    Most nocturnal Lepidoptera can be attracted to artificial light sources, particularly to those that emit a high proportion of ultraviolet radiation. Here, I describe a newly developed LED lamp set for the use in the field that is lightweight, handy, robust, and energy efficient. The emitted electromagnetic spectrum corresponds to the peak sensitivity in most Lepidoptera eye receptors (ultraviolet, blue and green). Power LEDs with peaks at 368 nm (ultraviolet), 450 nm (blue), 530 nm (green), a...

  15. Highly efficient white top-emitting organic light-emitting diodes with forward directed light emission

    Energy Technology Data Exchange (ETDEWEB)

    Freitag, Patricia; Reineke, Sebastian; Furno, Mauro; Luessem, Bjoern; Leo, Karl [Institut fuer Angewandte Photophysik, TU Dresden (Germany)

    2010-07-01

    The demand for highly efficient and energy saving illumination has increased considerably during the last decades. Organic light emitting diodes (OLEDs) are promising candidates for future lighting technologies. They offer high efficiency along with excellent color quality, allowing substantially lower power consumption than traditional illuminants. Recently, especially top-emitting devices have attracted high interest due to their compatibility with opaque substrates like metal sheets. In this contribution, we demonstrate top-emitting OLEDs with white emission spectra employing a multilayer hybrid cavity structure with two highly efficient phosphorescent emitter materials for orange-red (Ir(MDQ)2(acac)) and green (Ir(ppy)3) emission as well as the stable fluorescent blue emitter TBPe. To improve the OLED performance and modify the color quality, two different electron blocking layers and anode material combinations are tested. Compared to Lambertian emission, our devices show considerably enhanced forward emission, which is preferred for most lighting applications. Besides broadband emission and angle independent emission maxima, power efficiencies of 13.3 lm/W at 3 V and external quantum efficiencies of 5.3% are achieved. The emission shows excellent CIE coordinates of (0.420,0.407) at approx. 1000 cd/m{sup 2} and color rendering indices up to 77.

  16. In Depth Analyses of LEDs by a Combination of X-ray Computed Tomography (CT) and Light Microscopy (LM) Correlated with Scanning Electron Microscopy (SEM).

    Science.gov (United States)

    Meyer, Jörg; Thomas, Christian; Tappe, Frank; Ogbazghi, Tekie

    2016-06-16

    In failure analysis, device characterization and reverse engineering of light emitting diodes (LEDs), and similar electronic components of micro-characterization, plays an important role. Commonly, different techniques like X-ray computed tomography (CT), light microscopy (LM) and scanning electron microscopy (SEM) are used separately. Similarly, the results have to be treated for each technique independently. Here a comprehensive study is shown which demonstrates the potentials leveraged by linking CT, LM and SEM. In depth characterization is performed on a white emitting LED, which can be operated throughout all characterization steps. Major advantages are: planned preparation of defined cross sections, correlation of optical properties to structural and compositional information, as well as reliable identification of different functional regions. This results from the breadth of information available from identical regions of interest (ROIs): polarization contrast, bright and dark-field LM images, as well as optical images of the LED cross section in operation. This is supplemented by SEM imaging techniques and micro-analysis using energy dispersive X-ray spectroscopy.

  17. Enhanced light extraction from GaN-based LEDs with a bottom-up assembled photonic crystal

    International Nuclear Information System (INIS)

    Gong Haibo; Hao Xiaopeng; Wu Yongzhong; Cao Bingqiang; Xia Wei; Xu Xiangang

    2011-01-01

    Highlights: → Polystyrene (PS) microspheres were employed as a template. → A noninvasive photonic crystal was fabricated on the surface of GaN-based LED. → Periodic arrangement of bowl-like holes served as a photonic crystal with gradually changed fill factors. → The electroluminescence intensity of LED with a photonic crystal was significantly enhanced. - Abstract: Photonic crystal (PhC) structure is an efficient tool for light extraction from light-emitting diodes (LEDs). The fabrication of a large area PhC structure on the light output surface of LEDs often involves sophisticated equipments such as nanoimprint lithography machine. In this study a monolayer of polystyrene (PS) microspheres was employed as a template to fabricate a noninvasive photonic crystal of indium tin oxide (ITO) on the surface of GaN-based LED. PS spheres can help to form periodic arrangement of bowl-like holes, a photonic crystal with gradually changed fill factors. Importantly, the electroluminescence intensity of LED with a photonic crystal was significantly enhanced by 1.5 times compared to that of the conventional one under various forward injection currents.

  18. Enhanced light extraction from GaN-based LEDs with a bottom-up assembled photonic crystal

    Energy Technology Data Exchange (ETDEWEB)

    Gong Haibo [State Key Lab of Crystal Materials, Shandong University, Jinan, 250100 (China); School of Materials Science and Engineering, University of Jinan, Jinan, 250022 (China); Hao Xiaopeng, E-mail: xphao@sdu.edu.cn [State Key Lab of Crystal Materials, Shandong University, Jinan, 250100 (China); Wu Yongzhong [State Key Lab of Crystal Materials, Shandong University, Jinan, 250100 (China); Cao Bingqiang [School of Materials Science and Engineering, University of Jinan, Jinan, 250022 (China); Xia Wei [Shandong Huaguang Optoelectronics Company, Ltd., Jinan, 250101 (China); Xu Xiangang [State Key Lab of Crystal Materials, Shandong University, Jinan, 250100 (China); Shandong Huaguang Optoelectronics Company, Ltd., Jinan, 250101 (China)

    2011-08-15

    Highlights: > Polystyrene (PS) microspheres were employed as a template. > A noninvasive photonic crystal was fabricated on the surface of GaN-based LED. > Periodic arrangement of bowl-like holes served as a photonic crystal with gradually changed fill factors. > The electroluminescence intensity of LED with a photonic crystal was significantly enhanced. - Abstract: Photonic crystal (PhC) structure is an efficient tool for light extraction from light-emitting diodes (LEDs). The fabrication of a large area PhC structure on the light output surface of LEDs often involves sophisticated equipments such as nanoimprint lithography machine. In this study a monolayer of polystyrene (PS) microspheres was employed as a template to fabricate a noninvasive photonic crystal of indium tin oxide (ITO) on the surface of GaN-based LED. PS spheres can help to form periodic arrangement of bowl-like holes, a photonic crystal with gradually changed fill factors. Importantly, the electroluminescence intensity of LED with a photonic crystal was significantly enhanced by 1.5 times compared to that of the conventional one under various forward injection currents.

  19. Development of constant-power driving control for light-emitting-diode (LED) luminaire

    International Nuclear Information System (INIS)

    Huang, Bin-Juine; Chen, Chun-Wei; Ong, Chin-Dian; Du, Bo-Han; Hsu, Po-Chien

    2013-01-01

    The illumination of an LED may be affected by operating temperature even under constant-current condition. A constant-power driving technique is proposed in the present study for LED luminaire. A linear system dynamics model of LED luminaire is first derived and used in the design of the feedback control system. The PI controller was designed and tuned taking into account the control accuracy and robust properties with respect to plant uncertainty and variation of operating conditions. The control system was implemented on a microprocessor and used to control a 150W LED luminaire. The test result shows that the feedback system accurately controls the input power of LED luminaire to within 1.3 per cent error. As the ambient temperature changes from 0 to 40 °C, the LED illumination varies slightly (−1.7%) for constant-power driving, as compared to that of constant-current driving (−12%) and constant-voltage driving (+50%). The constant-power driving has revealed advantage in stabilizing the illumination of LED under large temperature variation. - Highlights: ► A constant-power driving technique is proposed for LED luminaire. ► A linear system dynamics model of LED luminaire is used in the control system design. ► The test shows that the feedback system accurately controls the input power. ► The LED illumination varies slightly (−1.7%) for constant-power driving.

  20. Large-signal modulation characteristics of a GaN-based micro-LED for Gbps visible-light communication

    Science.gov (United States)

    Tian, Pengfei; Wu, Zhengyuan; Liu, Xiaoyan; Fang, Zhilai; Zhang, Shuailong; Zhou, Xiaolin; Liu, Kefu; Liu, Ming-Gang; Chen, Shu-Jhih; Lee, Chia-Yu; Cong, Chunxiao; Hu, Laigui; Qiu, Zhi-Jun; Zheng, Lirong; Liu, Ran

    2018-04-01

    The large-signal modulation characteristics of a GaN-based micro-LED have been studied for Gbps visible-light communication. With an increasing signal modulation depth the modulation bandwidth decreases, which matches up with the increase in the sum of the signal rise time and fall time. By simulating the band diagram and the carrier recombination rate of the micro-LED under large-signal modulation, carrier recombination and the carrier sweep-out effect are analyzed and found to be the dominant mechanisms behind the variation of modulation bandwidth. These results give further insight into improving the modulation bandwidth for high-speed visible-light communication.