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.

"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.

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

-inconstancy indices: 17.1 and 11.5 CIELAB units, under reference illuminants D65 and A, respectively. Colour contrasts in women's faces under CIE standard illuminants for outdoor and indoor conditions may be strongly altered by using specific white LEDs. More research needs to be done on the impact of spectral power distribution of light sources with high colour rendering indices on visual colour appearance of cosmetic products. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

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.

LED Uniform Illumination Using Double Linear Fresnel Lenses for Energy Saving

Directory of Open Access Journals (Sweden)

Ngoc Hai Vu

2017-12-01

Full Text Available We present a linear Fresnel lens design for light-emitting diode (LED uniform illumination applications. The LED source is an array of LEDs. An array of collimating lens is applied to collimate output from the LED array. Two linear Fresnel lenses are used to redistribute the collimated beam along two dimensions in the illumination area. Collimating lens and linear Fresnel lens surfaces are calculated by geometrical optics and nonimaging optics. The collimated beam output from the collimating lens array is divided into many fragments. Each fragment is refracted by a segment of Fresnel lens and distributed over the illumination area, so that the total beam can be distributed to the illumination target uniformly. The simulation results show that this design has a compact structure, high optical efficiency of 82% and good uniformity of 76.9%. Some consideration of the energy savings and optical performance are discussed by comparison with other typical light sources. The results show that our proposed LED lighting system can reduce energy consumption five-times in comparison to using a conventional fluorescent lamp. Our research is a strong candidate for low cost, energy savings for indoor and outdoor lighting applications.

Optical design and fabrication of palm/fingerprint uniform illumination system with a high-power near-infrared light-emitting diode.

Science.gov (United States)

Jing, Lei; Wang, Yao; Zhao, Huifu; Ke, Hongliang; Wang, Xiaoxun; Gao, Qun

2017-06-10

In order to meet the requirements of uniform illumination for optical palm/fingerprint instruments and overcome the shortcomings of the poor uniform illumination on the working plane of the optical palm/fingerprint prism, a novel secondary optical lens with a free-form surface, compact structure, and high uniformity is presented in this paper. The design of the secondary optical lens is based on emission properties of the near-infrared light-emitting diode (LED) and basic principles of non-imaging optics, especially considering the impact of the thickness of the prism in the design. Through the numerical solution of Snell's law in geometric optics, we obtain the profile of the free-form surface of the lens. Using the optical software TracePro, we trace and simulate the illumination system. The results show that the uniformity is 89.8% on the working plane of the prism, and the test results show that the actual uniformity reaches 85.7% in the experiment, which provides an effective way for realizing a highly uniform illumination system with high-power near-infrared LED.

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

Freeform lens design for LED collimating illumination.

Science.gov (United States)

Chen, Jin-Jia; Wang, Te-Yuan; Huang, Kuang-Lung; Liu, Te-Shu; Tsai, Ming-Da; Lin, Chin-Tang

2012-05-07

We present a simple freeform lens design method for an application to LED collimating illumination. The method is derived from a basic geometric-optics analysis and construction approach. By using this method, a highly collimating lens with LED chip size of 1.0 mm × 1.0 mm and optical simulation efficiency of 86.5% under a view angle of ± 5 deg is constructed. To verify the practical performance of the lens, a prototype of the collimator lens is also made, and an optical efficiency of 90.3% with a beam angle of 4.75 deg is measured.

An overview of LED applications for general illumination

Science.gov (United States)

Pelka, David G.; Patel, Kavita

2003-11-01

This paper begins by reviewing the current state of development of LEDs, their existing markets as well as their potential for energy conservation and their potential for gaining market share in the general illumination market. It discusses LED metrics such as chip size, lumens per watt, thermal resistance, and the recommended maximum current rating. The paper then goes on to consider the importance of non-imaging optics for both optically efficient and extremely compact LED lighting systems. Finally, microstructures useful for controlling the fields-of-view of LED lighting systems are considered and described in some detail. An extremely efficient and cost effective microstructure, called kinoform diffusers, is shown to have very unique properties that make this technology almost ideal for shaping the output beams of LED lighting systems. It concludes by illustrating some general illumination LED lighting systems

Optimal LED-based illumination control via distributed convex optimization

NARCIS (Netherlands)

Aslam, Muhammad; Hermans, R.M.; Pandharipande, A.; Lazar, M.; Boje, Edward; Xia, Xiaohua

2014-01-01

Achieving illumination and energy consumption targets is essential in indoor lighting design. The provision of localized illumination to occupants, and the utilization of natural light and energy-efficient light-emitting diode (LED) luminaires can help meet both objectives. Localized illumination

Effection of UV-LED Illuminant on the Curation of Photolatent-amidine Mixed with Bisphenol A Epoxy Acrylate under Printing Conditions

Directory of Open Access Journals (Sweden)

Duan Huawei

2016-01-01

Full Text Available In order to make photocuring ink or coating cured by UV-LED illuminant, we synthesized (4-((hexahydropyrrolo[1,2-a]pyrimidin-1 (2H-ylmethylphenyl(phenylmethanone(PL -DBN and (4-((octahydropyrimido[1,2-a]azepin-1(2H-ylmethylphenyl(phenylmet hanone(PL -DBU as photoinitiators. Different mass fraction of the photoinitiators was mixed with bisphenol A epoxy acrylate, cured by different wavelengths and power of UV-LED illuminant,and investigated the curing effects of photoinitiators on bisphenol A epoxy acrylate. The results show that the conversion of C=C double bonds of bisphenol A epoxy acrylate will increase as the mass fraction of the photoinitiators or the power of UV-LED illuminant increase. In the same conditions, the curing effect of using 365nm UV-LED illuminant on bisphenol A epoxy acrylate is better than using 395nm UV-LED illuminant. PL-DBU has a better curing effect on the bisphenol A epoxy acrylate rather than PL-DBN. When using the 8W/cm2 of 365nm UV-LED illuminant to cure a mixture of 3% PL-DBU and 97% bisphenol A epoxy acrylate, it will be dry completely in 2 seconds, moreover, the conversion reach 79%.

High Power UV LED Industrial Curing Systems

Energy Technology Data Exchange (ETDEWEB)

Karlicek, Robert, F., Jr; Sargent, Robert

2012-05-14

UV curing is a green technology that is largely underutilized because UV radiation sources like Hg Lamps are unreliable and difficult to use. High Power UV LEDs are now efficient enough to replace Hg Lamps, and offer significantly improved performance relative to Hg Lamps. In this study, a modular, scalable high power UV LED curing system was designed and tested, performing well in industrial coating evaluations. In order to achieve mechanical form factors similar to commercial Hg Lamp systems, a new patent pending design was employed enabling high irradiance at long working distances. While high power UV LEDs are currently only available at longer UVA wavelengths, rapid progress on UVC LEDs and the development of new formulations designed specifically for use with UV LED sources will converge to drive more rapid adoption of UV curing technology. An assessment of the environmental impact of replacing Hg Lamp systems with UV LED systems was performed. Since UV curing is used in only a small portion of the industrial printing, painting and coating markets, the ease of use of UV LED systems should increase the use of UV curing technology. Even a small penetration of the significant number of industrial applications still using oven curing and drying will lead to significant reductions in energy consumption and reductions in the emission of green house gases and solvent emissions.

Development of constant-power driving control for light-emitting-diode (LED) luminaire

KAUST Repository

Huang, Bin-Juine

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. © 2012 Elsevier Ltd. All rights reserved.

Uniform illumination rendering using an array of LEDs: a signal processing perspective

OpenAIRE

Yang, Hongming; Bergmans, J.W.M.; Schenk, T.C.W.; Linnartz, J.P.M.G.; Rietman, R.

2009-01-01

An array of a large number of LEDs will be widely used in future indoor illumination systems. In this paper, we investigate the problem of rendering uniform illumination by a regular LED array on the ceiling of a room. We first present two general results on the scaling property of the basic illumination pattern, i.e., the light pattern of a single LED, and the setting of LED illumination levels, respectively. Thereafter, we propose to use the relative mean squared error as the cost function ...

DMD-based LED-illumination super-resolution and optical sectioning microscopy.

Science.gov (United States)

Dan, Dan; Lei, Ming; Yao, Baoli; Wang, Wen; Winterhalder, Martin; Zumbusch, Andreas; Qi, Yujiao; Xia, Liang; Yan, Shaohui; Yang, Yanlong; Gao, Peng; Ye, Tong; Zhao, Wei

2013-01-01

Super-resolution three-dimensional (3D) optical microscopy has incomparable advantages over other high-resolution microscopic technologies, such as electron microscopy and atomic force microscopy, in the study of biological molecules, pathways and events in live cells and tissues. We present a novel approach of structured illumination microscopy (SIM) by using a digital micromirror device (DMD) for fringe projection and a low-coherence LED light for illumination. The lateral resolution of 90 nm and the optical sectioning depth of 120 μm were achieved. The maximum acquisition speed for 3D imaging in the optical sectioning mode was 1.6×10(7) pixels/second, which was mainly limited by the sensitivity and speed of the CCD camera. In contrast to other SIM techniques, the DMD-based LED-illumination SIM is cost-effective, ease of multi-wavelength switchable and speckle-noise-free. The 2D super-resolution and 3D optical sectioning modalities can be easily switched and applied to either fluorescent or non-fluorescent specimens.

New reversing freeform lens design method for LED uniform illumination with extended source and near field

Science.gov (United States)

Zhao, Zhili; Zhang, Honghai; Zheng, Huai; Liu, Sheng

2018-03-01

In light-emitting diode (LED) array illumination (e.g. LED backlighting), obtainment of high uniformity in the harsh condition of the large distance height ratio (DHR), extended source and near field is a key as well as challenging issue. In this study, we present a new reversing freeform lens design algorithm based on the illuminance distribution function (IDF) instead of the traditional light intensity distribution, which allows uniform LED illumination in the above mentioned harsh conditions. IDF of freeform lens can be obtained by the proposed mathematical method, considering the effects of large DHR, extended source and near field target at the same time. In order to prove the claims, a slim direct-lit LED backlighting with DHR equal to 4 is designed. In comparison with the traditional lenses, illuminance uniformity of LED backlighting with the new lens increases significantly from 0.45 to 0.84, and CV(RMSE) decreases dramatically from 0.24 to 0.03 in the harsh condition. Meanwhile, luminance uniformity of LED backlighting with the new lens is obtained as high as 0.92 at the condition of extended source and near field. This new method provides a practical and effective way to solve the problem of large DHR, extended source and near field for LED array illumination.

New illuminations approaches with single-use micro LEDs endoilluminators for the pars plana vitrectomy

Science.gov (United States)

Koelbl, Philipp Simon; Koch, Frank H. J.; Lingenfelder, Christian; Hessling, Martin

2018-02-01

The illumination of the intraocular space during pars plana vitrectomy always bears the risk of retina damage by irradiation. Conventional illumination systems consist of an external light source and an optical fiber to transfer the visible light (radiation) into the eye. Often xenon arc and halogen lamps are employed for this application with some disadvantageous properties like high phototoxicity and low efficiency. Therefore, we propose to generate the light directly within the eye by inserting a white micro LED with a diameter of 0.6 mm. The LED offers a luminous flux of 0.6 lm of white light with a blue peak @ 450 nm and a yellow peak @ 555 nm. The presented prototypes fit through a standard 23 G trocar and are the first intraocular light sources worldwide. Two different single-use approaches have already been developed: a handguided and a chandelier device. The hand-guided applicator enables a directly navigation and illumination up to a working distance of 6 mm. The chandelier device is much smaller and does not need an active navigation of the light cone. The brightness and homogeneity of the illumination of these LED devices have been successfully tested on porcine eyes. Presented measurements and calculations prove that even for high LED currents and small distances to the retina these intraocular micro LED devices expose the retina to less hazard than conventional illumination sources like fiber based xenon systems. Even under the worst circumstances application durations of 180 hours would be justifiable.

Observed Minimum Illuminance Threshold for Night Market Vendors in Kenya who use LED Lamps

Energy Technology Data Exchange (ETDEWEB)

Johnstone, Peter; Jacobson, Arne; Mills, Evan; Radecsky, Kristen

2009-03-21

Creation of light for work, socializing, and general illumination is a fundamental application of technology around the world. For those who lack access to electricity, an emerging and diverse range of LED based lighting products hold promise for replacing and/or augmenting their current fuel-based lighting sources that are costly and dirty. Along with analysis of environmental factors, economic models for total cost-ofownership of LED lighting products are an important tool for studying the impacts of these products as they emerge in markets of developing countries. One important metric in those models is the minimum illuminance demanded by end-users for a given task before recharging the lamp or replacing batteries. It impacts the lighting service cost per unit time if charging is done with purchased electricity, batteries, or charging services. The concept is illustrated in figure 1: LED lighting products are generally brightest immediately after the battery is charged or replaced and the illuminance degrades as the battery is discharged. When a minimum threshold level of illuminance is reached, the operational time for the battery charge cycle is over. The cost to recharge depends on the method utilized; these include charging at a shop at a fixed price per charge, charging on personal grid connections, using solar chargers, and purchasing dry cell batteries. This Research Note reports on the observed"charge-triggering" illuminance level threshold for night market vendors who use LED lighting products to provide general and task oriented illumination. All the study participants charged with AC power, either at a fixed-price charge shop or with electricity at their home.

High power blue LED development using different growth modes

Energy Technology Data Exchange (ETDEWEB)

Lee, Dong S.; Florescu, Doru I.; Ramer, Jeff C.; Merai, Vinod; Parekh, Aniruddh; Begarney, Michael J.; Armour, Eric A. [Veeco TurboDisc Operations, 394 Elizabeth Avenue, Somerset, NJ 08873 (United States); Lu Dong [Veeco TurboDisc Operations, 394 Elizabeth Avenue, Somerset, NJ 08873 (United States); School of Engineering, Rutgers University, Piscataway, NJ 08854 (United States)

2004-09-01

Blue high brightness light emitting diodes (HB-LEDs) have been developed using different growth modes in the active layers. Piezoelectric field engineering improves the optical output power in multiple quantum well (MQW) LEDs by inserting an optimized transitional superlattice (TSL) before the active MQW layers. Within single quantum well (SQW) LEDs, quasi-Quantum Dot (QD) growth for Indium localization has been realized. The SQW LED output power exceeds the strain engineered MQW LEDs. The experimental data indicates that Indium localization enhances overall quantum efficiency and results in increased output power for HB-LEDs. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

In vitro Evaluation of Magnification and LED Illumination for Detection of Occlusal Caries in Primary and Permanent Molars Using ICDAS Criteria

Directory of Open Access Journals (Sweden)

Timucin Ari

2013-09-01

Full Text Available Background: Early detection of occlusal caries in children is challenging for the dentists, because of the morphology of pit and fissures. Aim: The aim of the present study was to investigate the use of low-powered magnification (×2.5 and its association with LED headlight illumination for occlusal caries detection in primary and permanent molars using International Caries Detection and Assessment System (ICDAS criteria.Methods: The occlusal surfaces of 36 extracted teeth (n=18 primary molars, n=18 permanent molars were examined using ICDAS criteria with unaided visual examination, low-powered magnification and low-powered magnification plus LED headlight illumination. Three examiners evaluated one occlusal site per tooth twice independently with one week interval, using all methods. The teeth (n = 36 were sectioned and examined under light microscopy using Downer’s histological criteria as the gold standard. Results: The weighted kappa values for inter- and intraexaminer reproducibility for the ICDAS examinations were almost perfect (Kappa values 0.72–0.96 in all three examination methods. The correlation with histology and overall AUC performance (0.96–0.98 of low-powered magnification plus LED headlight illumination was statistically significant in permanent molars. In primary molars, both low-powered magnification (0.82–0.90 and low-powered magnification plus LED headlight illumination (0.87–0.93 showed statistically significant correlation with histology and good to excellent AUC performance than unaided examination. Conclusion: Visual aids have the potential to improve the performance of early caries detection and clinical diagnostics in children.

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

The effects of LED illumination spectra and intensity on carotenoid content in Brassicaceae microgreens.

Science.gov (United States)

Brazaitytė, Aušra; Sakalauskienė, Sandra; Samuolienė, Giedrė; Jankauskienė, Julė; Viršilė, Akvilė; Novičkovas, Algirdas; Sirtautas, Ramūnas; Miliauskienė, Jurga; Vaštakaitė, Viktorija; Dabašinskas, Laurynas; Duchovskis, Pavelas

2015-04-15

The objective of this study was to evaluate the effects of irradiance levels and spectra produced by solid-state light-emitting diodes (LEDs) on carotenoid content and composition changes in Brassicaceae microgreens. A system of five high-power, solid-state lighting modules with standard 447-, 638-, 665-, and 731-nm LEDs was used in the experiments. Two experiments were performed: (1) evaluation of LED irradiance levels of 545, 440, 330, 220, and 110 μmol m(-2) s(-1) photosynthetically active flux density (PPFD) and (2) evaluation of the effects of 520-, 595-, and 622-nm LEDs supplemental to the standard set of LEDs. Concentrations of various carotenoids in red pak choi and tatsoi were higher under illumination of 330-440 μmol m(-2) s(-1) and at 110-220 μmol m(-2) s(-1) in mustard. All supplemental wavelengths increased total carotenoid content in mustard but decreased it in red pak choi. Carotenoid content increased in tatsoi under supplemental yellow light. Copyright © 2014 Elsevier Ltd. All rights reserved.

High-power light-emitting diode based facility for plant cultivation

Energy Technology Data Exchange (ETDEWEB)

Tamulaitis, G [Institute of Materials Science and Applied Research, Vilnius University, Sauletekio al. 9-III, LT-10222 Vilnius (Lithuania); Duchovskis, P [Lithuanian Institute of Horticulture, Babtai, LT-54333 Kaunas District (Lithuania); Bliznikas, Z [Institute of Materials Science and Applied Research, Vilnius University, Sauletekio al. 9-III, LT-10222 Vilnius (Lithuania); Breive, K [Institute of Materials Science and Applied Research, Vilnius University, Sauletekio al. 9-III, LT-10222 Vilnius (Lithuania); Ulinskaite, R [Lithuanian Institute of Horticulture, Babtai, LT-54333 Kaunas District (Lithuania); Brazaityte, A [Lithuanian Institute of Horticulture, Babtai, LT-54333 Kaunas District (Lithuania); Novickovas, A [Institute of Materials Science and Applied Research, Vilnius University, Sauletekio al. 9-III, LT-10222 Vilnius (Lithuania); Zukauskas, A [Institute of Materials Science and Applied Research, Vilnius University, Sauletekio al. 9-III, LT-10222 Vilnius (Lithuania)

2005-09-07

Based on perspectives of the development of semiconductor materials systems for high-power light-emitting diodes (LEDs), an illumination facility for greenhouse plant cultivation was designed with the dominating 640 nm photosynthetically active component delivered by AlGaInP LEDs and supplementary components from AlGaN (photothropic action, 455 nm) and AlGaAs (photosynthetic 660 nm and photomorphogenetic 735 nm) LEDs. Photosynthesis intensity, photosynthetic productivity and growth morphology as well as chlorophyll and phytohormone concentrations were investigated in radish and lettuce grown in phytotron chambers under the LED-based illuminators and under high-pressure sodium (HPS) lamps with an equivalent photon flux density. Advantages of the high-power LED-based illuminators over conventional HPS lamps, applicability of AlGaInP LEDs for photosynthesis and control of plant growth by circadian manipulation of a relatively weak far-red component were demonstrated.

High-power light-emitting diode based facility for plant cultivation

International Nuclear Information System (INIS)

Tamulaitis, G; Duchovskis, P; Bliznikas, Z; Breive, K; Ulinskaite, R; Brazaityte, A; Novickovas, A; Zukauskas, A

2005-01-01

Based on perspectives of the development of semiconductor materials systems for high-power light-emitting diodes (LEDs), an illumination facility for greenhouse plant cultivation was designed with the dominating 640 nm photosynthetically active component delivered by AlGaInP LEDs and supplementary components from AlGaN (photothropic action, 455 nm) and AlGaAs (photosynthetic 660 nm and photomorphogenetic 735 nm) LEDs. Photosynthesis intensity, photosynthetic productivity and growth morphology as well as chlorophyll and phytohormone concentrations were investigated in radish and lettuce grown in phytotron chambers under the LED-based illuminators and under high-pressure sodium (HPS) lamps with an equivalent photon flux density. Advantages of the high-power LED-based illuminators over conventional HPS lamps, applicability of AlGaInP LEDs for photosynthesis and control of plant growth by circadian manipulation of a relatively weak far-red component were demonstrated

Uniform illumination rendering using an array of LEDs: a signal processing perspective

NARCIS (Netherlands)

Yang, Hongming; Bergmans, J.W.M.; Schenk, T.C.W.; Linnartz, J.P.M.G.; Rietman, R.

2009-01-01

An array of a large number of LEDs will be widely used in future indoor illumination systems. In this paper, we investigate the problem of rendering uniform illumination by a regular LED array on the ceiling of a room. We first present two general results on the scaling property of the basic

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%.

Inactivation and changes in metabolic profile of selected foodborne bacteria by 460 nm LED illumination.

Science.gov (United States)

Kumar, Amit; Ghate, Vinayak; Kim, Min-Jeong; Zhou, Weibiao; Khoo, Gek Hoon; Yuk, Hyun-Gyun

2017-05-01

The objective of this study was to investigate the effect of 460 nm light-emitting diode (LED) on the inactivation of foodborne bacteria. Additionally, the change in the endogenous metabolic profile of LED illuminated cells was analyzed to understand the bacterial response to the LED illumination. Six different species of bacteria (Bacillus cereus, Listeria monocytogenes, Staphylococcus aureus, Escherichia coli O157:H7, Pseudomonas aeruginosa and Salmonella Typhimurium) were illuminated with 460 nm LED to a maximum dose of 4080 J/cm 2 at 4, 10 and 25 °C. Inactivation curves were modeled using Hom model. Metabolic profiling of the non-illuminated and illuminated cells was performed using a Liquid chromatography-mass spectrometry system. Results indicate that the 460 nm LED significantly (p illuminated cells indicated that several metabolites e.g. 11-deoxycortisol, actinonin, coformycin, tyramine, chitobiose etc. were regulated during LED illumination. These results elucidate the effectiveness of 460 nm LED against foodborne bacteria and hence, its suitability as a novel antimicrobial control method to ensure food safety. Copyright © 2016 Elsevier Ltd. All rights reserved.

Investigation of illumination efficiency on the LED therapy with different array types

Science.gov (United States)

Chen, Hsi-Chao; Liou, Cheng-Jyun

2009-08-01

Light-emitting diodes (LEDs) are a major discovery in twenty-one century for its advantages including small size, long lifetime, low voltage, high response and good mechanical properties. It is an environment-friendly product and maybe becomes a lighting source in future. In the other way LED lighting also is used for the lighting source of cosmetology. LED phototherapy provided medicine with a new tool capable of delivering light deep into tissues of the body, at wavelengths that are biologically optimal for pain treatment and holistic healing. The illumination efficiency is one of the key indexes for the LED phototherapy. LEDs were arranged on a disk of diameter of 100mm with different array types: a radial, a rhombus, an octagon, and a square. Then the LEDs with view angle of 120 degree were used for the lighting sources. Trace-Pro software was used for the optical simulation. The array types of radial and square were better than those of rhombus and octagon for illumination efficiency. In the mixture efficiency of a radial array was observed by different distances from 1mm to 100mm. However lighting could reach the well mixture after the treatment distance of 30mm by optical simulation. The view angle could reach +/-60 degree at the treatment distance of 50 mm for the LED phototherapy mockup.

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

Application of Wireless Intelligent Control System for HPS Lamps and LEDs Combined Illumination in Road Tunnel

Science.gov (United States)

Lai, Jinxing; Qiu, Junling; Chen, Jianxun; Wang, Yaqiong; Fan, Haobo

2014-01-01

Because of the particularity of the environment in the tunnel, the rational tunnel illumination system should be developed, so as to optimize the tunnel environment. Considering the high cost of traditional tunnel illumination system with high-pressure sodium (HPS) lamps as well as the effect of a single light source on tunnel entrance, the energy-saving illumination system with HPS lamps and LEDs combined illumination in road tunnel, which could make full use of these two kinds of lamps, was proposed. The wireless intelligent control system based on HPS lamps and LEDs combined illumination and microcontrol unit (MCU) Si1000 wireless communication technology was designed. And the remote monitoring, wireless communication, and PWM dimming module of this system were designed emphatically. Intensity detector and vehicle flow detector can be configured in wireless intelligent control system, which gather the information to the master control unit, and then the information is sent to the monitoring center through the Ethernet. The control strategies are got by the monitoring center according to the calculated results, and the control unit wirelessly sends parameters to lamps, which adjust the luminance of each segment of the tunnel and realize the wireless intelligent control of combined illumination in road tunnel. PMID:25587266

Many-junction photovoltaic device performance under non-uniform high-concentration illumination

Science.gov (United States)

Valdivia, Christopher E.; Wilkins, Matthew M.; Chahal, Sanmeet S.; Proulx, Francine; Provost, Philippe-Olivier; Masson, Denis P.; Fafard, Simon; Hinzer, Karin

2017-09-01

A parameterized 3D distributed circuit model was developed to calculate the performance of III-V solar cells and photonic power converters (PPC) with a variable number of epitaxial vertically-stacked pn junctions. PPC devices are designed with many pn junctions to realize higher voltages and to operate under non-uniform illumination profiles from a laser or LED. Performance impacts of non-uniform illumination were greatly reduced with increasing number of junctions, with simulations comparing PPC devices with 3 to 20 junctions. Experimental results using Azastra Opto's 12- and 20-junction PPC illuminated by an 845 nm diode laser show high performance even with a small gap between the PPC and optical fiber output, until the local tunnel junction limit is reached.

Development of constant-power driving control for light-emitting-diode (LED) luminaire

KAUST Repository

Huang, Bin-Juine; Chen, Chun-Wei; Ong, Chin-Dian; Du, Bo-Han; Hsu, Po-Chien

2013-01-01

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

Daylight integrated illumination control of LED systems based on enhanced presence sensing

NARCIS (Netherlands)

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

2011-01-01

Light emitting diodes (LEDs) are considered to become the dominant source of illumination in the future, offering long life times, energy efficiency and flexible tunability. The flexibility of adapting LED parameters offers multiple degrees of freedom in designing LED based lighting systems. In this

Direct illumination LED calibration for telescope photometry

International Nuclear Information System (INIS)

Barrelet, E.; Juramy, C.

2008-01-01

A calibration method for telescope photometry, based on the direct illumination of a telescope with a calibrated light source regrouping multiple LEDs, is proposed. Its purpose is to calibrate the instrument response. The main emphasis of the proposed method is the traceability of the calibration process and a continuous monitoring of the instrument in order to maintain a 0.2% accuracy over a period of years. Its specificity is to map finely the response of the telescope and its camera as a function of all light ray parameters. This feature is essential to implement a computer model of the instrument representing the variation of the overall light collection efficiency of each pixel for various filter configurations. We report on hardware developments done for SNDICE, the first application of this direct illumination calibration system which will be installed in Canada France Hawaii telescope (CFHT) for its leading supernova experiment (SNLS)

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.

Pulsed operation of high-power light emitting diodes for imaging flow velocimetry

International Nuclear Information System (INIS)

Willert, C; Klinner, J; Moessner, S; Stasicki, B

2010-01-01

High-powered light emitting diodes (LED) are investigated for possible uses as light sources in flow diagnostics, in particular, as an alternative to laser-based illumination in particle imaging flow velocimetry in side-scatter imaging arrangements. Recent developments in solid state illumination resulted in mass-produced LEDs that provide average radiant power in excess of 10 W. By operating these LEDs with short duration, pulsed currents that are considerably beyond their continuous current damage threshold, light pulses can be generated that are sufficient to illuminate and image micron-sized particles in flow velocimetry. Time-resolved PIV measurements in water at a framing rate of 2kHz are presented. The feasibility of LED-based PIV measurements in air is also demonstrated

P1-16: The Effect of Visual Stimuli of LED Lighting by Color Temperature and Illuminance Control on Attention and Meditation Level of Mind

Directory of Open Access Journals (Sweden)

Chan-Su Lee

2012-10-01

Full Text Available Recently LED (Lighting Emitting Diode lighting sources are applied not only for displays like LED BLU (back light unit TV but also for general lighting like LED lamps for home and office. The color temperature, or chromaticity, and brightness of LED lighting can be easily controlled. Preferred combinations between illuminance and color temperature of lighting depend on daily living activities (Oi et al., 2007 Symposium on Design of Artificial Environments 214–215. Changes in intensity can be more easily detected than color changes (Almeida et al., 2009 Perception 38 1109–1117. We investigated whether the illumination stimuli of LED lighting can enhance attention and relaxation level by controlling color temperature and illuminance according to activities. EEG signals are used to estimate attention and relaxation levels of human subjects under different lighting conditions. Nine participants with normal eye sight and color vision participated in the experiments with four different activities under different illumination conditions. LED lighting with color temperature 3600 K in 240 lux is used for relaxation activities, and LED lighting with 6600 K in 794 lux is used for the task which requires attention. These lighting conditions are compared with conventional lighting condition with 4600 K in 530 lux. Preliminary experiment results show that low color temperature with low illumination intensity of LED lighting enhances relaxation level and high color temperature with high illuminance improves attention level compared with conventional lighting environment without illuminance and color temperature changes.

High-power UV-LED degradation: Continuous and cycled working condition influence

Science.gov (United States)

Arques-Orobon, F. J.; Nuñez, N.; Vazquez, M.; Segura-Antunez, C.; González-Posadas, V.

2015-09-01

High-power (HP) UV-LEDs can replace UV lamps for real-time fluoro-sensing applications by allowing portable and autonomous systems. However, HP UV-LEDs are not a mature technology, and there are still open issues regarding their performance evolution over time. This paper presents a reliability study of 3 W UV-LEDs, with special focus on LED degradation for two working conditions: continuous and cycled (30 s ON and 30 s OFF). Accelerated life tests are developed to evaluate the influence of temperature and electrical working conditions in high-power LEDs degradation, being the predominant failure mechanism the degradation of the package. An analysis that includes dynamic thermal and optical HP UV-LED measurements has been performed. Static thermal and stress simulation analysis with the finite element method (FEM) identifies the causes of package degradation. Accelerated life test results prove that HP UV-LEDs working in cycled condition have a better performance than those working in continuous condition.

Integrated LED/Imaging Illumination Panels Demonstrated within a Small Plant Growth Chamber Project

Data.gov (United States)

National Aeronautics and Space Administration — LED light sources are ideal for plant growth systems. However, commercially available multi-color LED illumination panels are designed and manufactured to produce a...

Advanced illumination control algorithm for medical endoscopy applications

Science.gov (United States)

Sousa, Ricardo M.; Wäny, Martin; Santos, Pedro; Morgado-Dias, F.

2015-05-01

CMOS image sensor manufacturer, AWAIBA, is providing the world's smallest digital camera modules to the world market for minimally invasive surgery and one time use endoscopic equipment. Based on the world's smallest digital camera head and the evaluation board provided to it, the aim of this paper is to demonstrate an advanced fast response dynamic control algorithm of the illumination LED source coupled to the camera head, over the LED drivers embedded on the evaluation board. Cost efficient and small size endoscopic camera modules nowadays embed minimal size image sensors capable of not only adjusting gain and exposure time but also LED illumination with adjustable illumination power. The LED illumination power has to be dynamically adjusted while navigating the endoscope over changing illumination conditions of several orders of magnitude within fractions of the second to guarantee a smooth viewing experience. The algorithm is centered on the pixel analysis of selected ROIs enabling it to dynamically adjust the illumination intensity based on the measured pixel saturation level. The control core was developed in VHDL and tested in a laboratory environment over changing light conditions. The obtained results show that it is capable of achieving correction speeds under 1 s while maintaining a static error below 3% relative to the total number of pixels on the image. The result of this work will allow the integration of millimeter sized high brightness LED sources on minimal form factor cameras enabling its use in endoscopic surgical robotic or micro invasive surgery.

Design of a novel freeform lens for LED uniform illumination and conformal phosphor coating.

Science.gov (United States)

Hu, Run; Luo, Xiaobing; Zheng, Huai; Qin, Zong; Gan, Zhiqiang; Wu, Bulong; Liu, Sheng

2012-06-18

A conformal phosphor coating can realize a phosphor layer with uniform thickness, which could enhance the angular color uniformity (ACU) of light-emitting diode (LED) packaging. In this study, a novel freeform lens was designed for simultaneous realization of LED uniform illumination and conformal phosphor coating. The detailed algorithm of the design method, which involves an extended light source and double refractions, was presented. The packaging configuration of the LED modules and the modeling of the light-conversion process were also presented. Monte Carlo ray-tracing simulations were conducted to validate the design method by comparisons with a conventional freeform lens. It is demonstrated that for the LED module with the present freeform lens, the illumination uniformity and ACU was 0.89 and 0.9283, respectively. The present freeform lens can realize equivalent illumination uniformity, but the angular color uniformity can be enhanced by 282.3% when compared with the conventional freeform lens.

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%.

LED-Based High-Voltage Lines Warning System

Directory of Open Access Journals (Sweden)

Eldar MUSA

2013-04-01

Full Text Available LED-based system, running with the current of high-voltage lines and converting the current flowing through the line into the light by using a toroid transformer, has been developed. The transformer’s primary winding is constituted by the high voltage power line. Toroidal core consists of two equal parts and the secondary windings are evenly placed on these two parts. The system is mounted on the high-voltage lines as a clamp. The secondary winding ends are connected in series by the connector on the clamp. LEDs are supplied by the voltage at the ends of secondary. Current flowing through highvoltage transmission lines is converted to voltage by the toroidal transformer and the light emitting LEDs are supplied with this voltage. The theory of the conversion of the current flowing through the line into the light is given. The system, running with the current of the line and converting the current into the light, has been developed. System has many application areas such as warning high voltage lines (warning winches to not hinder the high-voltage lines when working under the lines, warning planes to not touch the high-voltage lines, remote measurement of high-voltage line currents, and local illumination of the line area

Microfluidic mixing triggered by an external LED illumination.

Science.gov (United States)

Venancio-Marques, Anna; Barbaud, Fanny; Baigl, Damien

2013-02-27

The mixing of confined liquids is a central yet challenging operation in miniaturized devices. Microfluidic mixing is usually achieved with passive mixers that are robust but poorly flexible, or active mixers that offer dynamic control but mainly rely on electrical or mechanical transducers, which increase the fragility, cost, and complexity of the device. Here, we describe the first remote and reversible control of microfluidic mixing triggered by a light illumination simply provided by an external LED illumination device. The approach is based on the light-induced generation of water microdroplets acting as reversible stirrers of two continuous oil phase flows containing samples to be mixed. We demonstrate many cycles of reversible photoinduced transitions between a nonmixing behavior and full homogenization of the two oil phases. The method is cheap, portable, and adaptable to many device configurations, thus constituting an essential brick for the generation of future all-optofluidic chip.

A thermosyphon heat pipe cooler for high power LEDs cooling

Science.gov (United States)

Li, Ji; Tian, Wenkai; Lv, Lucang

2016-08-01

Light emitting diode (LED) cooling is facing the challenge of high heat flux more seriously with the increase of input power and diode density. The proposed unique thermosyphon heat pipe heat sink is particularly suitable for cooling of high power density LED chips and other electronics, which has a heat dissipation potential of up to 280 W within an area of 20 mm × 22 mm (>60 W/cm2) under natural air convection. Meanwhile, a thorough visualization investigation was carried out to explore the two phase flow characteristics in the proposed thermosyphon heat pipe. Implementing this novel thermosyphon heat pipe heat sink in the cooling of a commercial 100 W LED integrated chip, a very low apparent thermal resistance of 0.34 K/W was obtained under natural air convection with the aid of the enhanced boiling heat transfer at the evaporation side and the enhanced natural air convection at the condensation side.

Optical design of a LED searchlight system

Science.gov (United States)

Gong, Chen; Xu, Haiping; Liang, Jinhua; Liu, Yunfei; Yuan, Zengquan

2018-01-01

A 1200m visible searchlight system is designed based on photometry and application of geometric optics. To generate intensity distribution of this relatively powerful light beam we propose to use a high power LED and several refractive optical elements, which are composed of two plane-convex lenses and a conventional Fresnel lens. Two plane-convex lenses enable refraction of the side rays from the LED to the front direction which incident on the Fresnel lens. Fresnel lens, in its turn, concentrate the light flux and provide a nearly collimated beam to meet the requirement of forming a well-illuminated area across the road in the far field. Simulation data shows that this searchlight allow generating an appropriate illumination distribution for the long range requirements. A proof-of-concept prototype producing acceptable illuminance is developed.

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.

Investigations on LED illumination for micro-PIV including a novel front-lit configuration

DEFF Research Database (Denmark)

Hagsäter, Melker; Bruus, Henrik; Kutter, Jörg Peter

2008-01-01

In this study, we provide a general investigation on micro-PIV with LED illumination. A number of improvements over previous LED-based systems are suggested, in particular, we present a novel front-lit configuration. As a demonstration of its versatility we have used this front-lit configuration...

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.

Random laser illumination: an ideal source for biomedical polarization imaging?

Science.gov (United States)

Carvalho, Mariana T.; Lotay, Amrit S.; Kenny, Fiona M.; Girkin, John M.; Gomes, Anderson S. L.

2016-03-01

Imaging applications increasingly require light sources with high spectral density (power over spectral bandwidth. This has led in many cases to the replacement of conventional thermal light sources with bright light-emitting diodes (LEDs), lasers and superluminescent diodes. Although lasers and superluminescent diodes appear to be ideal light sources due to their narrow bandwidth and power, however, in the case of full-field imaging, their spatial coherence leads to coherent artefacts, such as speckle, that corrupt the image. LEDs, in contrast, have lower spatial coherence and thus seem the natural choice, but they have low spectral density. Random Lasers are an unconventional type of laser that can be engineered to provide low spatial coherence with high spectral density. These characteristics makes them potential sources for biological imaging applications where specific absorption and reflection are the characteristics required for state of the art imaging. In this work, a Random Laser (RL) is used to demonstrate speckle-free full-field imaging for polarization-dependent imaging in an epi-illumination configuration. We compare LED and RL illumination analysing the resulting images demonstrating that the RL illumination produces an imaging system with higher performance (image quality and spectral density) than that provided by LEDs.

Lunar South Pole Illumination: Review, Reassessment, and Power System Implications

Science.gov (United States)

Fincannon, James

2007-01-01

This paper reviews past analyses and research related to lunar south pole illumination and presents results of independent illumination analyses using an analytical tool and a radar digital elevation model. The analysis tool enables assessment at most locations near the lunar poles for any time and any year. Average illumination fraction, energy storage duration, solar/horizon terrain elevation profiles and illumination fraction profiles are presented for various highly illuminated sites which have been identified for manned or unmanned operations. The format of the data can be used by power system designers to develop mass optimized solar and energy storage systems. Data are presented for the worse case lunar day (a critical power planning bottleneck) as well as three lunar days during lunar south pole winter. The main site under consideration by present lunar mission planners (on the Crater Shackleton rim) is shown to have, for the worse case lunar day, a 0.71 average illumination fraction and 73 to 117 hours required for energy storage (depending on power system type). Linking other sites and including towers at either site are shown to not completely eliminate the need for energy storage.

Design of multisegmented freeform lens for LED fishing/working lamp with high efficiency.

Science.gov (United States)

Lai, Min-Feng; Anh, Nguyen Doan Quoc; Gao, Jia-Zhi; Ma, Hsin-Yi; Lee, Hsiao-Yi

2015-10-01

A novel LED fishing/working light is proposed to enhance the lighting efficiency of a fishing boat. The study is focused on the freeform secondary lens design so as to create a lamp that attracts fish and sheds light on the deck for the crew's work. The experimental results show that the proposed multisegmented freeform lens can deliver the proposed aim, giving 3 times as much illuminating power as the traditional high-intensity discharge fishing lamp does with the same input of electrical power.

A self-calibrating led-based solar test platform

DEFF Research Database (Denmark)

Krebs, Frederik C; Sylvester-Hvid, Kristian O.; Jørgensen, Mikkel

2011-01-01

A compact platform for testing solar cells is presented. The light source comprises a multi-wavelength high-power LED (light emitting diode) array allowing the homogenous illumination of small laboratory solar cell devices (substrate size 50 × 25 mm) within the 390–940 nm wavelength range......, it is possible to perform all the commonly employed measurements on the solar cell at very high speed without moving the sample. In particular, the LED-based illumination system provides an alternative to light-biased incident photon-to-current efficiency measurement to be performed which we demonstrate. Both...

Tunable output-frequency filter algorithm for imaging through scattering media under LED illumination

Science.gov (United States)

Zhou, Meiling; Singh, Alok Kumar; Pedrini, Giancarlo; Osten, Wolfgang; Min, Junwei; Yao, Baoli

2018-03-01

We present a tunable output-frequency filter (TOF) algorithm to reconstruct the object from noisy experimental data under low-power partially coherent illumination, such as LED, when imaging through scattering media. In the iterative algorithm, we employ Gaussian functions with different filter windows at different stages of iteration process to reduce corruption from experimental noise to search for a global minimum in the reconstruction. In comparison with the conventional iterative phase retrieval algorithm, we demonstrate that the proposed TOF algorithm achieves consistent and reliable reconstruction in the presence of experimental noise. Moreover, the spatial resolution and distinctive features are retained in the reconstruction since the filter is applied only to the region outside the object. The feasibility of the proposed method is proved by experimental results.

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

Highly sensitive time resolved singlet oxygen luminescence detection using LEDs as the excitation source

International Nuclear Information System (INIS)

Hackbarth, S; Schlothauer, J; Preuss, A; Röder, B

2013-01-01

For the first time singlet oxygen luminescence kinetics in living cells were detected at high precision using LED light for excitation. As LED technology evolves, the light intensity emitted by standard LEDs allows photosensitized singlet oxygen luminescence detection in solution and cell suspensions. We present measurements superior to those of most actual laser powered setups regarding precision of singlet oxygen kinetics in solutions and cell suspensions. Data presented here show that LED based setups allow the determination of the photosensitizer triplet and singlet oxygen decay times in vitro with an accuracy of 0.1 μs. This enables monitoring of the photosensitizer efficiency and interaction with the cellular components using illumination doses small enough not to cause cell death. (letter)

‘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...

Mono- and dichromatic LED illumination leads to enhanced growth and energy conversion for high-efficiency cultivation of microalgae for application in space.

Science.gov (United States)

Wagner, Ines; Steinweg, Christian; Posten, Clemens

2016-08-01

Illumination with red and blue photons is known to be efficient for cultivation of higher plants. For microalgae cultivation, illumination with specific wavelengths rather than full spectrum illumination can be an alternative where there is a lack of knowledge about achievable biomass yields. This study deals with the usage of color LED illumination to cultivate microalgae integrated into closed life support systems for outer space. The goal is to quantify biomass yields using color illumination (red, blue, green and mixtures) compared to white light. Chlamydomonas reinhardtii was cultivated in plate reactors with color compared to white illumination regarding PCE, specific pigment concentration and cell size. Highest PCE values were achieved under low PFDs with a red/blue illumination (680 nm/447 nm) at a 90 to 10% molar ratio. At higher PFDs saturation effects can be observed resulting from light absorption characteristics and the linear part of PI curve. Cell size and aggregation are also influenced by the applied light color. Red/blue color illumination is a promising option applicable for microalgae-based modules of life support systems under low to saturating light intensities and double-sided illumination. Results of higher PCE with addition of blue photons to red light indicate an influence of sensory pigments. Copyright © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Numerical analysis of lateral illumination lightpipes using elliptical grooves

Science.gov (United States)

Sánchez-Guerrero, Guillermo E.; Viera-González, Perla M.; Martínez-Guerra, Edgar; Ceballos-Herrera, Daniel E.

2017-09-01

Lightpipes are used for illumination in applications such as back-lighting or solar cell concentrators due to the high irradiance uniformity, but its optimal design requires several parameters. This work presents a procedure to design a square lightpipe to control the light-extraction on its lateral face using commercial LEDs placed symmetrically in the lightpipe frontal face. We propose the use of grooves using total internal reflection placed successively in the same face of extraction to control the area of emission. The LED area of emission is small compared with the illuminated area, and, as expected, the lateral face total power is attenuated. These grooves reduce the optical elements in the system and can control areas of illumination. A mathematical and numerical analysis are presented to determine the dependencies on the light-extraction.

Bridgeless SEPIC PFC Converter for Multistring LED Driver

Science.gov (United States)

Jha, Aman; Singh, Bhim

2018-05-01

This paper deals with Power Factor Correction (PFC) in Low Voltage High Current (LVHC) multi-string light emitting diode (LED) using a bridgeless (BL) single ended primary inductance converter (SEPIC). This application is designed for large area LED lighting with illumination control. A multi-mode LED dimming technique is used for the lighting control. The BL-SEPIC PFC converter is used as a load emulator for high power factor. The regulated low voltage from flyback converter is a source power to the synchronous buck converters for multi-string LED driver and forced cooling system for LED junction. The BL-SEPIC PFC converter inductor design is based on Discontinuous Inductor Current Modes (DICM) which provides good PFC at low cost. Test results are found quite satisfactory for universal input AC (90-265 V). There is significant improvement in the power factor and input current Total Harmonic Distortion (THD) with good margin of harmonic limits for lighting IEC 61000-3-2 Class C.

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....

Effects of illuminants and illumination time on lettuce growth, yield and nutritional quality in a controlled environment

Science.gov (United States)

Shen, Y. Z.; Guo, S. S.; Ai, W. D.; Tang, Y. K.

2014-07-01

Effects of illuminants and illumination time on the growth of lettuce were researched. Red-blue light-emitting diodes (LEDs, 90% red light +10% blue light) and white light fluorescent (WF) lamps were compared as the illuminants for plant cultivation. Under each type of illuminant, lettuce was grown at 4 illumination times: 12 h, 16 h, 20 h and 24 h, with the same light intensity of 600 μmolm-2s-1. The leaf net photosynthetic rate (Pn) under the two illuminants was comparable but the shape of lettuce was obviously affected by the illuminant. The WF lamps produced more compact plant, while red-blue LED resulted in less but longer leaves. However, the total leaf area was not significantly affected by the illuminant. The red-blue LED produced nearly same aboveground biomass with far less energy consumption relative to WF lamps. The underground biomass was lowered under red-blue LED in comparison with WF lamps. Red-blue LED could improve the nutritional quality of lettuce by increasing the concentration of soluble sugar and vitamin C (VC) and reducing the concentration of nitrate. Under each type of illuminant, longer illumination time resulted in higher Pn, more leaves and larger leaf area. The total chlorophyll concentration increased while the concentration ratio of chlorophyll a/b decreased with the extension of illumination time. Illumination time had highly significant positive correlation with biomass. Moreover, when total daily light input was kept the same, longer illumination time increased the biomass significantly as well. In addition, longer illumination time increased the concentration of crude fiber, soluble sugar and VC and reduced the concentration of nitrate. In summary, red-blue LEDs and 24 h illumination time were demonstrated to be more suitable for lettuce cultivation in the controlled environment.

Photoreceptor spectral sensitivity of the compound eyes of black soldier fly (Hermetia illucens) informing the design of LED-based illumination to enhance indoor reproduction.

Science.gov (United States)

Oonincx, D G A B; Volk, N; Diehl, J J E; van Loon, J J A; Belušič, G

2016-12-01

Mating in the black soldier fly (BSF) is a visually mediated behaviour that under natural conditions occurs in full sunlight. Artificial light conditions promoting mating by BSF were designed based on the spectral characteristics of the compound eye retina. Electrophysiological measurements revealed that BSF ommatidia contained UV-, blue- and green-sensitive photoreceptor cells, allowing trichromatic vision. An illumination system for indoor breeding based on UV, blue and green LEDs was designed and its efficiency was compared with illumination by fluorescent tubes which have been successfully used to sustain a BSF colony for five years. Illumination by LEDs and the fluorescent tubes yielded equal numbers of egg clutches, however, the LED illumination resulted in significantly more larvae. The possibilities to optimize the current LED illumination system to better approximate the skylight illuminant and potentially optimize the larval yield are discussed. Copyright © 2016 Elsevier Ltd. All rights reserved.

A Single-Stage High-Power-Factor Light-Emitting Diode (LED Driver with Coupled Inductors for Streetlight Applications

Directory of Open Access Journals (Sweden)

Chun-An Cheng

2017-02-01

Full Text Available This paper presents and implements a single-stage high-power-factor light-emitting diode (LED driver with coupled inductors, suitable for streetlight applications. The presented LED driver integrates an interleaved buck-boost power factor correction (PFC converter with coupled inductors and a half-bridge-type series-resonant converter cascaded with a full-bridge rectifier into a single-stage power conversion circuit. Coupled inductors inside the interleaved buck-boost PFC converter sub-circuit are designed to operate in discontinuous conduction mode (DCM for achieving input-current shaping, and the half-bridge-type series resonant converter cascaded with a full-bridge rectifier is designed for obtaining zero-voltage switching (ZVS on two power switches to reduce their switching losses. Analysis of operational modes and design equations for the presented LED driver are described and included. In addition, the presented driver features a high power factor, low total harmonic distortion (THD of input current, and soft switching. Finally, a prototype driver is developed and implemented to supply a 165-W-rated LED streetlight module with utility-line input voltages ranging from 210 to 230 V. Experimental results demonstrate that high power factor (>0.99, low utility-line current THD (<7%, low-output voltage ripples (<1%, low-output current ripples (<10%, and high circuit efficiency (>90% are obtained in the presented single-stage driver for LED streetlight applications.

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.

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

Tolerancing a lens for LED uniform illumination

Science.gov (United States)

Ryu, Jieun; Sasian, Jose

2017-08-01

A method to evaluate tolerance sensitivities for lenses used to produce uniform illumination is presented. Closed form surfaces are used to define optical surfaces and relative illumination is calculated from light etendue considerations.

Highly efficient and reliable high power LEDs with patterned sapphire substrate and strip-shaped distributed current blocking layer

Energy Technology Data Exchange (ETDEWEB)

Zhou, Shengjun [School of Power and Mechanical Engineering, Wuhan University, Wuhan 430072 (China); State Key Laboratory of Mechanical System and Vibration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Yuan, Shu; Liu, Yingce [Quantum Wafer Inc., Foshan 528251 (China); Guo, L. Jay [Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109 (United States); Liu, Sheng, E-mail: victor_liu63@126.com [School of Power and Mechanical Engineering, Wuhan University, Wuhan 430072 (China); Ding, Han [State Key Laboratory of Mechanical System and Vibration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China)

2015-11-15

Graphical abstract: - Highlights: • TEM is used to characterize threading dislocation existing in GaN epitaxial layer. • Effect of threading dislocation on optical and electrical of LEDs is discussed. • Strip-shaped SiO{sub 2} DCBL is designed to improve current spreading performance of LEDs. - Abstract: We demonstrated that the improvement in optical and electrical performance of high power LEDs was achieved using cone-shaped patterned sapphire substrate (PSS) and strip-shaped SiO{sub 2} distributed current blocking layer (DCBL). We found through transmission electron microscopy (TEM) observation that densities of both the screw dislocation and edge dislocation existing in GaN epitaxial layer grown on PSS were much less than that of GaN epitaxial layer grown on flat sapphire substrate (FSS). Compared to LED grown on FSS, LED grown on PSS showed higher sub-threshold forward-bias voltage and lower reverse leakage current, resulting in an enhancement in device reliability. We also designed a strip-shaped SiO{sub 2} DCBL beneath a strip-shaped p-electrode, which prevents the current from being concentrated on regions immediately adjacent the strip-shaped p-electrode, thereby facilitating uniform current spreading into the active region. By implementing strip-shaped SiO{sub 2} DCBL, light output power of high power PSS-LED chip could be further increased by 13%.

Forward Conduction Mode Controlled Piezoelectric Transformer-Based PFC LED Drive

DEFF Research Database (Denmark)

Roedgaard, M. S.; Weirich, M.; Andersen, M. A. E.

2013-01-01

Light-emitting diode (LED) illumination is getting more and more common; as LED's performance is rising, the price is falling and is getting competitive. Some of the challenges of ac mains supplied illumination are the requirement of power factor correction (PFC) and the competitiveness of a low...... priced market. In this paper, a new forward conduction mode (FCM) control method for piezoelectric transformer (PT)-based power converters is proposed. A PT-based LED drive facilitating passive PFC is developed, utilizing and validating the FCM control method. The drive utilizes an inductorless half...... LED drive has been developed, supplied from 230-V 50-Hz ac mains, achieving a power factor of 0.96....

Dynamic Control Based Photovoltaic Illuminating System

Directory of Open Access Journals (Sweden)

Zhang Chengkai

2016-01-01

Full Text Available Smart LED illumination system can use the power from whether the photovoltaic cell or the power grid automatically based on the SOC (State Of Charge of the photovoltaic cell. This paper proposes a feedback control of the photovoltaic cells and a dynamic control strategy for the Energy system. The dynamic control strategy is used to determine the switching state of the photovoltaic cell based on the illumination load in the past one hour and the battery capacity. These controls are manifested by experimental prototype that the control scheme is correct and effective.

Development of a High Irradiance LED Configuration for Small Field of View Motion Estimation of Fertilizer Particles

Directory of Open Access Journals (Sweden)

Simon Cool

2015-11-01

Full Text Available Better characterization of the fertilizer spreading process, especially the fertilizer pattern distribution on the ground, requires an accurate measurement of individual particle properties and dynamics. Both 2D and 3D high speed imaging techniques have been developed for this purpose. To maximize the accuracy of the predictions, a specific illumination level is required. This paper describes the development of a high irradiance LED system for high speed motion estimation of fertilizer particles. A spectral sensitivity factor was used to select the optimal LED in relation to the used camera from a range of commercially available high power LEDs. A multiple objective genetic algorithm was used to find the optimal configuration of LEDs resulting in the most homogeneous irradiance in the target area. Simulations were carried out for different lenses and number of LEDs. The chosen configuration resulted in an average irradiance level of 452 W/m2 with coefficient of variation less than 2%. The algorithm proved superior and more flexible to other approaches reported in the literature and can be used for various other applications.

Temperature increase inside LED-based illuminators for in vitro aPDT photodamage studies

Science.gov (United States)

Battisti, A.; Morici, P.; Tortora, G.; Menciassi, A.; Checcucci, G.; Ghetti, F.; Sgarbossa, A.

2018-06-01

Antimicrobial PhotoDynamic Therapy (aPDT) is an emerging strategy aimed at the eradication of bacterial infections, with a special focus on antibiotic-resistant bacteria. This method is easy to apply, not expensive and particularly interesting in case of bacteria that spontaneously produce the required photosensitizers. In the framework of a project aimed at the development of an ingestible pill for the application of aPDT to gastric infections by Helicobacter pylori, a LED-based illuminating prototype (LED-BIP) was purposely designed in order to evaluate the photodamage induced by light of different wavelengths on porphyrin-producing bacteria. This short paper reports about temperature tests performed to assess the maximum exposure time and light dose that can be administered to bacterial cultures inside LED-BIP without reaching temperatures exceeding the physiological range.

Light-controlled microwave whispering-gallery-mode quasi-optical resonators at 50W LED array illumination

Directory of Open Access Journals (Sweden)

V. B. Yurchenko

2015-08-01

Full Text Available We present experimental observations of light-controlled resonance effects in microwave whispering-gallery-mode quasi-optical dielectric-semiconductor disk resonators in the frequency band of 5 GHz to 20 GHz arising due to illumination from a light emitting diode (LED of 50W power range. We obtain huge enhancement of photo-sensitivity (growing with the resonator Q-factor that makes light-microwave interaction observable with an ordinary light (no laser at conventional brightness (like an office lighting in quasi-optical microwave structures at rather long (centimeter-scale wavelength. We also demonstrate non-conventional photo-response of Fano resonances when the light suppresses one group of resonances and enhances another group. The effects could be used for the optical control and quasi-optical switching of microwave propagation through either one or another frequency channel.

Numerical simulation and experimental research of the integrated high-power LED radiator

Science.gov (United States)

Xiang, J. H.; Zhang, C. L.; Gan, Z. J.; Zhou, C.; Chen, C. G.; Chen, S.

2017-01-01

The thermal management has become an urgent problem to be solved with the increasing power and the improving integration of the LED (light emitting diode) chip. In order to eliminate the contact resistance of the radiator, this paper presented an integrated high-power LED radiator based on phase-change heat transfer, which realized the seamless connection between the vapor chamber and the cooling fins. The radiator was optimized by combining the numerical simulation and the experimental research. The effects of the chamber diameter and the parameters of fin on the heat dissipation performance were analyzed. The numerical simulation results were compared with the measured values by experiment. The results showed that the fin thickness, the fin number, the fin height and the chamber diameter were the factors which affected the performance of radiator from primary to secondary.

Design of a lighting system with high-power LEDs, large area electronics, and light management structure in the LUMENTILE European project

Science.gov (United States)

Carraro, L.; Simonetta, M.; Benetti, G.; Tramonte, A.; Capelli, G.; Benedetti, M.; Randone, E. M.; Ylisaukko-oja, A.; Keränen, K.; Facchinetti, T.; Giuliani, G.

2017-02-01

LUMENTILE (LUMinous ElectroNic TILE) is a project funded by the European Commission with the goal of developing a luminous tile with novel functionalities, capable of changing its color and interact with the user. Applications include interior/exterior tile for walls and floors covering, high-efficiency luminaries, and advertising under the form of giant video screens. High overall electrical efficiency of the tile is mandatory, as several millions of square meters are foreseen to be installed each year. Demand is for high uniformity of the illumination of the top tile surface, and for high optical extraction efficiency. These features are achieved by smart light management, using a new approach based on light guiding slab and spatially selective light extraction obtained using both diffusion and/or reflection from the top and bottom interfaces of the optical layer. Planar and edge configurations for the RGB LEDs are considered and compared. A square shape with side length from 20cm to 60cm is considered for the tiles. The electronic circuit layout must optimize the electrical efficiency, and be compatible with low-cost roll-to-roll production on flexible substrates. LED heat management is tackled by using dedicated solutions that allow operation in thermally harsh environment. An approach based on OLEDs has also been considered, still needing improvement on emitted power and ruggedness.

Solid-state semiconductors are better alternatives to arc-lamps for efficient and uniform illumination in minimal access surgery.

Science.gov (United States)

Lee, Alex C H; Elson, Daniel S; Neil, Mark A; Kumar, Sunil; Ling, Bingo W; Bello, Fernando; Hanna, George B

2009-03-01

Current arc-lamp illumination systems have a number of technical and ergonomic limitations. White light-emitting diodes (LEDs) are energy-efficient solid-state lighting devices which are small, durable and inexpensive. Their use as an alternative to arc-lamp light sources in minimal access surgery has not been explored. This study aims to develop an LED-based endo-illuminator and to determine its lighting characteristics for use in minimal access surgery. We developed an LED endo-illuminator using a white LED mounted at the tip of a steel rod. Offline image analysis was carried out to compare the illuminated field using the LED endo-illuminator or an arc-lamp based endoscope in terms of uniformity, shadow sharpness and overall image intensity. Direct radiometric power measurements in light intensity and stability were obtained. Visual perception of fine details at the peripheral endoscopic field was assessed by 13 subjects using the different illumination systems. Illumination from the LED endo-illuminator was more uniform compared to illumination from an arc-lamp source, especially at the closer distance of 4 cm (0.0006 versus 0.0028 arbitrary units--lower value indicates more uniform illumination). The shadows were also sharper (edge widths of 16 versus 44 pixels for the first edge and 15 versus 61 pixels for the second edge). The overall mean image intensity was higher (127 versus 100 arbitrary units) when using the autoshutter mode despite the lower direct radiometric power, about one tenth of the arc-lamp endoscopic system. The illumination was also more stable with less flickering (0.02% versus 5% of total power in non-DC components). Higher median scores on visual perception was also obtained (237 versus 157, p arc-lamp-based system currently used.

LED lamp power management system and method

Science.gov (United States)

Gaines, James; Clauberg, Bernd; Van Erp, Josephus A. M.

2013-03-19

An LED lamp power management system and method including an LED lamp having an LED controller 58; a plurality of LED channels 60 operably connected to the LED controller 58, each of the plurality of LED channels 60 having a channel switch 62 in series with at least one shunted LED circuit 83, the shunted LED circuit 83 having a shunt switch 68 in parallel with an LED source 80. The LED controller 58 reduces power loss in one of the channel switch 62 and the shunt switch 68 when LED lamp electronics power loss (P.sub.loss) exceeds an LED lamp electronics power loss limit (P.sub.lim); and each of the channel switches 62 receives a channel switch control signal 63 from the LED controller 58 and each of the shunt switches 68 receives a shunt switch control signal 69 from the LED controller 58.

Ultraviolet excitation of remote phosphor with symmetrical illumination used in dual-sided liquid-crystal display.

Science.gov (United States)

Huang, Hsin-Tao; Tsai, Chuang-Chuang; Huang, Yi-Pai

2010-08-01

The UV-excited flat lighting (UFL) technique differs from conventional fluorescent lamp or LED illumination. It involves using a remote phosphor film to convert the wavelength of UV light to visible light, achieving high brightness and planar and uniform illumination. In particular, UFL can accomplish compact size, low power consumption, and symmetrical dual-sided illumination. Additionally, UFL utilizes a thermal radiation mechanism to release the large amount of heat that is generated upon illumination without thermal accumulation. These characteristics of the UFL technique can motivate a wide range of lighting applications in thin-film transistor LCD backlighting or general lighting.

The improvement of photocatalytic processes: Design of a photoreactor using high-power LEDs

Directory of Open Access Journals (Sweden)

Marzieh Khademalrasool

2016-09-01

Full Text Available This paper is an attempt to survey the benefits of a well-designed photoreactor containing just 6 ultraviolet (UV high power light emitting diodes (HPLEDs; the power and wavelength of each UV HPLED are 1 W and 365 nm, respectively, the latter being an efficient source for photocatalytic studies. Although the experiment with the 365-nm LEDs is reported here, other LEDs were predicted for conducting similar experiments including green photocatalytic ones. We installed diodes with respect to the luminescence intensity distribution curves (LIDCs or intensity patterns. Then, in order to compare the efficiency of the UV-HPLEDs of the HP-LED photoreactor (HPLED-PhR with that of traditional UV lamps which are extensively used in photocatalytic processes, a set of UV HPLEDs was designed and made up. Next, the performance of HPLED-PhR was compared with that of a traditional fluorescent lamp photoreactor (FL-PhR. As a typical photocatalytic experiment, Zinc Oxide (ZnO nanoparticles were synthesized via co-precipitation method and used as photocatalyst for purification of water polluted with the reactive blue dye (RB, under UV irradiation in two photoreactors. The results showed that the rate of photocatalytic reaction under the UV-LEDs was two times greater than the rate under the traditional fluorescent UV lamps, while both electrical power consumption and manufacturing cost of the HPLED-PhR were less than a quarter of them for the FL-PhR.

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.

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...

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.

High-efficiency VCSEL arrays for illumination and sensing in consumer applications

Science.gov (United States)

Seurin, Jean-Francois; Zhou, Delai; Xu, Guoyang; Miglo, Alexander; Li, Daizong; Chen, Tong; Guo, Baiming; Ghosh, Chuni

2016-03-01

There has been increased interest in vertical-cavity surface-emitting lasers (VCSELs) for illumination and sensing in the consumer market, especially for 3D sensing ("gesture recognition") and 3D image capture. For these applications, the typical wavelength range of interest is 830~950nm and power levels vary from a few milli-Watts to several Watts. The devices are operated in short pulse mode (a few nano-seconds) with fast rise and fall times for time-of-flight applications (ToF), or in CW/quasi-CW for structured light applications. In VCSELs, the narrow spectrum and its low temperature dependence allows the use of narrower filters and therefore better signal-to-noise performance, especially for outdoor applications. In portable devices (mobile devices, wearable devices, laptops etc.) the size of the illumination module (VCSEL and optics) is a primary consideration. VCSELs offer a unique benefit compared to other laser sources in that they are "surface-mountable" and can be easily integrated along with other electronics components on a printed circuit board (PCB). A critical concern is the power-conversion efficiency (PCE) of the illumination source operating at high temperatures (>50 deg C). We report on various VCSEL based devices and diffuser-integrated modules with high efficiency at high temperatures. Over 40% PCE was achieved in broad temperature range of 0-70 °C for either low power single devices or high power VCSEL arrays, with sub- nano-second rise and fall time. These high power VCSEL arrays show excellent reliability, with extracted mean-time-to-failure (MTTF) of over 500 years at 60 °C ambient temperature and 8W peak output.

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 �

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.

Diffuse-Illumination Systems for Growing Plants

Science.gov (United States)

May, George; Ryan, Robert

2010-01-01

Agriculture in both terrestrial and space-controlled environments relies heavily on artificial illumination for efficient photosynthesis. Plant-growth illumination systems require high photon flux in the spectral range corresponding with plant photosynthetic active radiation (PAR) (400 700 nm), high spatial uniformity to promote uniform growth, and high energy efficiency to minimize electricity usage. The proposed plant-growth system takes advantage of the highly diffuse reflective surfaces on the interior of a sphere, hemisphere, or other nearly enclosed structure that is coated with highly reflective materials. This type of surface and structure uniformly mixes discrete light sources to produce highly uniform illumination. Multiple reflections from within the domelike structures are exploited to obtain diffuse illumination, which promotes the efficient reuse of photons that have not yet been absorbed by plants. The highly reflective surfaces encourage only the plant tissue (placed inside the sphere or enclosure) to absorb the light. Discrete light sources, such as light emitting diodes (LEDs), are typically used because of their high efficiency, wavelength selection, and electronically dimmable properties. The light sources are arranged to minimize shadowing and to improve uniformity. Different wavelengths of LEDs (typically blue, green, and red) are used for photosynthesis. Wavelengths outside the PAR range can be added for plant diagnostics or for growth regulation

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

Infrared Illuminated CdZnTe detectors with improved performance

International Nuclear Information System (INIS)

Ivanov, V.; Loutchanski, A.; Dorogov, P.; Khinoverov, S.

2013-06-01

It was found that IR illumination of a properly chosen wavelength and intensity can significantly improve spectrometric characteristics of CdZnTe quasi-hemispherical detectors [1]. Improving of the spectrometric characteristics is due to improvement of uniformity of charge collection by the detector volume. For operation at room temperature the optimal wavelength of IR illumination is about 940 nm, but for operation at lower temperature of -20 deg. C the optimal wavelengths of IR illumination is about 1050 nm. Infrared illumination can be performed using conventional low-power IR LEDs. Application of SMD LEDs allows produce miniature detection probes with IR illuminated CdZnTe detectors. We have fabricated and tested a variety of detection probes with CdZnTe quasi-hemispherical detectors from the smallest with volumes of 1-5 mm 3 to larger with volumes of 1.5 cm 3 and 4.0 cm 3 . The use of IR illumination significantly improves spectrometric characteristics of the probes operating at room temperature, especially probes with detectors of large volumes. The probe with the detector of 4 cm 3 without IR illumination had energy resolution of 24.2 keV at 662 keV and of 12.5 keV with IR illumination. (authors)

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.

High-efficiency silicon solar cells for low-illumination applications

OpenAIRE

Glunz, S.W.; Dicker, J.; Esterle, M.; Hermle, M.; Isenberg, J.; Kamerewerd, F.; Knobloch, J.; Kray, D.; Leimenstoll, A.; Lutz, F.; Oßwald, D.; Preu, R.; Rein, S.; Schäffer, E.; Schetter, C.

2002-01-01

At Fraunhofer ISE the fabrication of high-efficiency solar cells was extended from a laboratory scale to a small pilot-line production. Primarily, the fabricated cells are used in small high-efficiency modules integrated in prototypes of solar-powered portable electronic devices such as cellular phones, handheld computers etc. Compared to other applications of high-efficiency cells such as solar cars and planes, the illumination densities found in these mainly indoor applications are signific...

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.

Experimental investigation of a PCM-HP heat sink on its thermal performance and anti-thermal-shock capacity for high-power LEDs

International Nuclear Information System (INIS)

Wu, Yuxuan; Tang, Yong; Li, Zongtao; Ding, Xinrui; Yuan, Wei; Zhao, Xuezhi; Yu, Binhai

2016-01-01

Highlights: • A phase-change material (PCM) base heat pipe heat sink (PCM-HP heat sink) is designed. • The PCM-HP heat sink can significantly lower the LED heating rate and temperature. • The PCM-HP heat sink achieves a best anti-thermal-shock capacity in LED cyclic working modes. - Abstract: High-power LEDs demonstrate a number of benefits compared with conventional incandescent lamps and fluorescent lamps, including a longer lifetime, higher brightness and lower power consumption. However, owing to their severe high heat flux, it is difficult to develop effective thermal management of high-power LEDs, especially under cyclic working modes, which cause serious periodic thermal stress and limit further development. Focusing on the above problem, this paper designed a phase-change material (PCM) base heat pipe heat sink (PCM-HP heat sink) that consists of a PCM base, adapter plate, heat pipe and finned radiator. Different parameters, such as three types of interior materials to fill the heat sink, three LED power inputs and eight LED cyclic working modes, were separately studied to investigate the thermal performance and anti-thermal-shock capacity of the PCM-HP heat sink. The results show that the PCM-HP heat sink possesses remarkable thermal performance owing to the reduction of the LED heating rate and peak temperature. More importantly, an excellent anti-thermal-shock capacity of the PCM-HP heat sink is also demonstrated when applied in LED cyclic working modes, and this capacity demonstrates the best range.

BInGaN alloys nearly lattice-matched to GaN for high-power high-efficiency visible LEDs

Science.gov (United States)

Williams, Logan; Kioupakis, Emmanouil

2017-11-01

InGaN-based visible light-emitting diodes (LEDs) find commercial applications for solid-state lighting and displays, but lattice mismatch limits the thickness of InGaN quantum wells that can be grown on GaN with high crystalline quality. Since narrower wells operate at a higher carrier density for a given current density, they increase the fraction of carriers lost to Auger recombination and lower the efficiency. The incorporation of boron, a smaller group-III element, into InGaN alloys is a promising method to eliminate the lattice mismatch and realize high-power, high-efficiency visible LEDs with thick active regions. In this work, we apply predictive calculations based on hybrid density functional theory to investigate the thermodynamic, structural, and electronic properties of BInGaN alloys. Our results show that BInGaN alloys with a B:In ratio of 2:3 are better lattice matched to GaN compared to InGaN and, for indium fractions less than 0.2, nearly lattice matched. Deviations from Vegard's law appear as bowing of the in-plane lattice constant with respect to composition. Our thermodynamics calculations demonstrate that the solubility of boron is higher in InGaN than in pure GaN. Varying the Ga mole fraction while keeping the B:In ratio constant enables the adjustment of the (direct) gap in the 1.75-3.39 eV range, which covers the entire visible spectrum. Holes are strongly localized in non-bonded N 2p states caused by local bond planarization near boron atoms. Our results indicate that BInGaN alloys are promising for fabricating nitride heterostructures with thick active regions for high-power, high-efficiency LEDs.

Development of flying spot illumination system for stage lighting

Science.gov (United States)

Asakawa, Hisashi; Ishii, Katsunori; Koshiro, Hikari; Baba, Junko; Wakaki, Moriaki

2014-02-01

The system to control the area of illumination is important for the luminaires used for stages and TV studios. Presently the methods to change the distance between a lamp and lenses, or to use a zooming projection of the aperture illuminated by the lamp are used to control the area. However, these methods require many optical components or mechanical components. Moreover, the energy of the light source is partially consumed by the absorption of the shutter on adjusting the illumination area. On the other hand, the control of the illuminance over the illuminated area is not possible by the methods. In this study, we developed the lighting system which enables to control both the illuminated area and the illuminance distribution within the area by scanning the beam from a LED array light source. The area of illumination was expanded along one dimension by scanning the LED beam using a rotating polygon mirror. The selection of the illuminated width and the control of the illuminance distribution were achieved by synchronizing the pulse width modulation (PWM) control of the LED with the rotation of the mirror using a time sharing control. As a result, various illuminance distributions can be realized at real time by using software control for the luminaire. The developed system has the merits of compact and high efficiency.

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....

Improving InGaN-LED performance by optimizing the patterned sapphire substrate shape

International Nuclear Information System (INIS)

Huang Xiao-Hui; Liu Jian-Ping; Fan Ya-Ming; Kong Jun-Jie; Yang Hui; Wang Huai-Bing

2012-01-01

The epitaxial growths of GaN films and GaN-based LEDs on various patterned sapphire substrates (PSSes) with different values of fill factor (f) and slanted angle (θ) are investigated in detail. The threading dislocation (TD) density is lower in the film grown on the PSS with a smaller fill factor, resulting in a higher internal quantum efficiency (IQE). Also the ability of the LED to withstand the electrostatic discharge (ESD) increases as the fill factor decreases. The illumination output power of the LED is affected by both θ and f. It is found that the illumination output power of the LED grown on the PSS with a lower production of tan θ and f is higher than that with a higher production of tan θ and f. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

High-aggregate-capacity visible light communication links using stacked multimode polymer waveguides and micro-pixelated LED arrays

Science.gov (United States)

Bamiedakis, N.; McKendry, J. J. D.; Xie, E.; Gu, E.; Dawson, M. D.; Penty, R. V.; White, I. H.

2018-02-01

In recent years, light emitting diodes (LEDs) have gained renewed interest for use in visible light communication links (VLC) owing to their potential use as both high-quality power-efficient illumination sources as well as low-cost optical transmitters in free-space and guided-wave links. Applications that can benefit from their use include optical wireless systems (LiFi and Internet of Things), in-home and automotive networks, optical USBs and short-reach low-cost optical interconnects. However, VLC links suffer from the limited LED bandwidth (typically 100 MHz). As a result, a combination of novel LED devices, advanced modulation formats and multiplexing methods are employed to overcome this limitation and achieve high-speed (>1 Gb/s) data transmission over such links. In this work, we present recent advances in the formation of high-aggregate-capacity low cost guided wave VLC links using stacked polymer multimode waveguides and matching micro-pixelated LED (μLED) arrays. μLEDs have been shown to exhibit larger bandwidths (>200 MHz) than conventional broad-area LEDs and can be formed in large array configurations, while multimode polymer waveguides enable the formation of low-cost optical links onto standard PCBs. Here, three- and four-layered stacks of multimode waveguides, as well as matching GaN μLED arrays, are fabricated in order to generate high-density yet low-cost optical interconnects. Different waveguide topologies are implemented and are investigated in terms of loss and crosstalk performance. The initial results presented herein demonstrate good intrinsic crosstalk performance and indicate the potential to achieve >= 0.5 Tb/s/mm2 aggregate interconnection capacity using this low-cost technology.

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

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.

Electrical Power and Illumination Systems. Energy Technology Series.

Science.gov (United States)

Center for Occupational Research and Development, Inc., Waco, TX.

This course in electrical power and illumination systems is one of 16 courses in the Energy Technology Series developed for an Energy Conservation-and-Use Technology curriculum. Intended for use in two-year postsecondary technical institutions to prepare technicians for employment, the courses are also useful in industry for updating employees in…

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

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.

A review of passive thermal management of LED module

NARCIS (Netherlands)

Ye, H.; Sau, K.; Zeijl, H. van; Gielen, A.W.J.; Zhang, G.

2011-01-01

Recently, the high-brightness LEDs have begun to be designed for illumination application. The increased electrical currents used to drive LEDs lead to thermal issues. Thermal management for LED module is a key design parameter as high operation temperature directly affects their maximum light

New developments in illumination, heating and cooling technologies for energy-efficient buildings

International Nuclear Information System (INIS)

Han, H.J.; Jeon, Y.I.; Lim, S.H.; Kim, W.W.; Chen, K.

2010-01-01

This paper gives a concise review of new designs and developments of illumination, heating and air-conditioning systems and technologies for energy-efficient buildings. Important breakthroughs in these areas include high-efficiency and/or reduced cost solar system components, LED lamps, smart windows, computer-controlled illumination systems, compact combined heat-power generation systems, and so on. To take advantage of these new technologies, hybrid or cascade energy systems have been proposed and/or investigated. A survey of innovative architectural and building envelope designs that have the potential to considerably reduce the illumination and heating and cooling costs for office buildings and residential houses is also included in the review. In addition, new designs and ideas that can be easily implemented to improve the energy efficiency and/or reduce greenhouse gas emissions and environmental impacts of new or existing buildings are proposed and discussed.

Color Calibration for Colorized Vision System with Digital Sensor and LED Array Illuminator

Directory of Open Access Journals (Sweden)

Zhenmin Zhu

2016-01-01

Full Text Available Color measurement by the colorized vision system is a superior method to achieve the evaluation of color objectively and continuously. However, the accuracy of color measurement is influenced by the spectral responses of digital sensor and the spectral mismatch of illumination. In this paper, two-color vision system illuminated by digital sensor and LED array, respectively, is presented. The Polynomial-Based Regression method is applied to solve the problem of color calibration in the sRGB and CIE  L⁎a⁎b⁎ color spaces. By mapping the tristimulus values from RGB to sRGB color space, color difference between the estimated values and the reference values is less than 3ΔE. Additionally, the mapping matrix ΦRGB→sRGB has proved a better performance in reducing the color difference, and it is introduced subsequently into the colorized vision system proposed for a better color measurement. Necessarily, the printed matter of clothes and the colored ceramic tile are chosen as the application experiment samples of our colorized vision system. As shown in the experimental data, the average color difference of images is less than 6ΔE. It indicates that a better performance of color measurement is obtained via the colorized vision system proposed.

Test and Control System for Chlorophyll Fluorescence Parameters Using LED as Excitation Source

Directory of Open Access Journals (Sweden)

Zou Qiuying

2014-05-01

Full Text Available A new scheme on test and control system for chlorophyll fluorescence is presented in this work, which uses light-emitting diode (LED excitation by means of measuring the fluorescence parameter fpsII. The system takes programmable power supply as LEDs illumination drive power with high sensitivity and signal-to-noise ratio. MINIPAM is used to measure fluorescence parameter fpsII and keeps communication with upper PC by serial port. The upper PC can control the power supply and process the data received from MINIPAM by software which is programmed in VB6. The results show that the system has a lot of advantages such as high accuracy and convenience. The effect of environmental factors on fluorescence parameters is analyzed comprehensively. It will be a practical measurement and control system for photosynthetic ability and have wide application foreground.

Direct design of achromatic lens for Lambertian sources in collimating illumination

Science.gov (United States)

Yin, Peng; Xu, Xiping; Jiang, Zhaoguo; Wang, Hongshu

2017-10-01

Illumination design used to redistribute the spatial energy distribution of light source is a key technique in lighting applications. However, there is still no effective illumination design method for the removing of the chromatic dispersion. What we present here is an achromatic lens design to enhance the efficiency and uniform illumination of white light-emitting diode (LED) with diffractive optical element (DOE). We employ the chromatic aberration value (deg) to measure the degree of chromatic dispersion in illumination systems. Monte Carlo ray tracing simulation results indicate that the chromatic dispersion of the modified achromatic collimator significantly decreases from 0.5 to 0.1 with LED chip size of 1.0mm×1.0mm and simulation efficiency of 90.73%, compared with the traditional collimator. Moreover, with different corrected wavelengths we compared different chromatic aberration values that followed with the changing pupil percent. The achromatic collimator provided an effective way to achieve white LED with low chromatic dispersion at high efficiency and uniform illumination.

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.

LED power efficiency of biomass, fatty acid, and carotenoid production in Nannochloropsis microalgae.

Science.gov (United States)

Ma, Ruijuan; Thomas-Hall, Skye R; Chua, Elvis T; Eltanahy, Eladl; Netzel, Michael E; Netzel, Gabriele; Lu, Yinghua; Schenk, Peer M

2018-03-01

The microalga Nannochloropsis produces high-value omega-3-rich fatty acids and carotenoids. In this study the effects of light intensity and wavelength on biomass, fatty acid, and carotenoid production with respect to light output efficiency were investigated. Similar biomass and fatty acid yields were obtained at high light intensity (150 μmol m -2  s -1 ) LEDs on day 7 and low light intensity (50 μmol m -2  s -1 ) LEDs on day 11 during cultivation, but the power efficiencies of biomass and fatty acid (specifically eicosapentaenoic acid) production were higher for low light intensity. Interestingly, low light intensity enhanced both, carotenoid power efficiency of carotenoid biosynthesis and yield. White LEDs were neither advantageous for biomass and fatty acid yields, nor the power efficiency of biomass, fatty acid, and carotenoid production. Noticeably, red LED resulted in the highest biomass and fatty acid power efficiency, suggesting that LEDs can be fine-tuned to grow Nannochloropsis algae more energy-efficiently. Copyright © 2017 Elsevier Ltd. All rights reserved.

MOSFET Loss Evaluation for a Low-Power Stand-Alone Photovoltaic-LED System

DEFF Research Database (Denmark)

Mira Albert, Maria del Carmen; Knott, Arnold; Andersen, Michael A. E.

2015-01-01

This paper presents a performance evaluation and comparison of state-of-the-art low voltage Si MOSFETs for a stand-alone photovoltaic-LED Light to Light (LtL) system. The complete system is formed by two cascaded converters that will be optimized for a determined solar irradiation and LED...... illumination profiles. The comparison is performed based on dynamic characterization and evaluation of the devices energy loss at different current levels....

Hybrid daylight/light-emitting diode illumination system for indoor lighting.

Science.gov (United States)

Ge, Aiming; Qiu, Peng; Cai, Jinlin; Wang, Wei; Wang, Junwei

2014-03-20

A hybrid illumination method using both daylight and light-emitting diodes (LEDs) for indoor lighting is presented in this study. The daylight can be introduced into the indoor space by a panel-integration system. The daylight part and LEDs are combined within a specific luminaire that can provide uniform illumination. The LEDs can be turned on and dimmed through closed-loop control when the daylight illuminance is inadequate. We simulated the illumination and calculated the indoor lighting efficiency of our hybrid daylight and LED lighting system, and compared this with that of LED and fluorescent lighting systems. Simulation results show that the efficiency of the hybrid daylight/LED illumination method is better than that of LED and traditional lighting systems, under the same lighting conditions and lighting time; the method has hybrid lighting average energy savings of T5 66.28%, and that of the LEDs is 41.62%.

Design of an elliptic spot illumination system in LED-based color filter-liquid-crystal-on-silicon pico projectors for mobile embedded projection.

Science.gov (United States)

Chen, Enguo; Yu, Feihong

2012-06-01

We present an elliptic spot illumination system for a color filter-liquid-crystal-on-silicon (CF-LCoS) pico projector employing a specifically designed free-form lens and a cylindrical lens to improve on previous designs in terms of optical efficiency while yielding an ultracompact and low-cost optical architecture. The detailed design description of the optical system is thoroughly investigated. Simulation results coincide well with the theoretical calculation. The single 1  mm×1  mm LED chip-powered optical engine, which employs a CF-LCoS panel with a diagonal of 0.28 in and an aspect ratio of 4:3, has an estimated output efficiency over 9.8% (11.8 lm@1 W) and an ANSI 9-point uniformity over 88.5%, with the ultrasmall volume 24  mm×19  mm×7  mm. Compared to the circular spot-illuminated projection system, a total increment of about 23% of system efficiency is available with this improved optical engine. It is believed that there would be a huge market potential to commercialize our design.

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%.

Micro-light-emitting-diode array with dual functions of visible light communication and illumination

International Nuclear Information System (INIS)

Huang Yong; Guo Zhi-You; Sun Hui-Qing; Huang Hong-Yong

2017-01-01

We demonstrate high-speed blue 4 × 4 micro-light-emitting-diode (LED) arrays with 14 light-emitting units (two light-emitting units are used as the positive and negative electrodes for power supply, respectively) comprising multiple quantum wells formed of GaN epitaxial layers grown on a sapphire substrate, and experimentally test their applicability for being used as VLC transmitters and illuminations. The micro-LED arrays provide a maximum −3-dB frequency response of 60.5 MHz with a smooth frequency curve from 1 MHz to 500 MHz for an optical output power of 165 mW at an injection current of 30 mA, which, to our knowledge, is the highest response frequency ever reported for blue GaN-based LEDs operating at that level of optical output power. The relationship between the frequency and size of the device single pixel diameter reveals the relationship between the response frequency and diffusion capacitance of the device. (paper)

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

Multispectral imaging of the ocular fundus using light emitting diode illumination.

Science.gov (United States)

Everdell, N L; Styles, I B; Calcagni, A; Gibson, J; Hebden, J; Claridge, E

2010-09-01

We present an imaging system based on light emitting diode (LED) illumination that produces multispectral optical images of the human ocular fundus. It uses a conventional fundus camera equipped with a high power LED light source and a highly sensitive electron-multiplying charge coupled device camera. It is able to take pictures at a series of wavelengths in rapid succession at short exposure times, thereby eliminating the image shift introduced by natural eye movements (saccades). In contrast with snapshot systems the images retain full spatial resolution. The system is not suitable for applications where the full spectral resolution is required as it uses discrete wavebands for illumination. This is not a problem in retinal imaging where the use of selected wavelengths is common. The modular nature of the light source allows new wavelengths to be introduced easily and at low cost. The use of wavelength-specific LEDs as a source is preferable to white light illumination and subsequent filtering of the remitted light as it minimizes the total light exposure of the subject. The system is controlled via a graphical user interface that enables flexible control of intensity, duration, and sequencing of sources in synchrony with the camera. Our initial experiments indicate that the system can acquire multispectral image sequences of the human retina at exposure times of 0.05 s in the range of 500-620 nm with mean signal to noise ratio of 17 dB (min 11, std 4.5), making it suitable for quantitative analysis with application to the diagnosis and screening of eye diseases such as diabetic retinopathy and age-related macular degeneration.

Evaluation of shear bond strength of orthodontic brackets using trans-illumination technique with different curing profiles of LED light-curing unit in posterior teeth.

Science.gov (United States)

Heravi, Farzin; Moazzami, Saied Mostafa; Ghaffari, Negin; Jalayer, Javad; Bozorgnia, Yasaman

2013-11-21

Although using light-cured composites for bonding orthodontic brackets has become increasingly popular, curing light cannot penetrate the metallic bulk of brackets and polymerization of composites is limited to the edges. Limited access and poor direct sight may be a problem in the posterior teeth. Meanwhile, effectiveness of the trans-illumination technique is questionable due to increased bucco-lingual thickness of the posterior teeth. Light-emitting diode (LED) light-curing units cause less temperature rise and lower risk to the pulpal tissue. The purpose of this study was to evaluate the clinical effectiveness of trans-illumination technique in bonding metallic brackets to premolars, using different light intensities and curing times of an LED light-curing unit. Sixty premolars were randomly divided into six groups. Bonding of brackets was done with 40- and 80-s light curing from the buccal or lingual aspect with different intensities. Shear bond strengths of brackets were measured using a universal testing machine. Data were analyzed by one-way analysis of variance test and Duncan's post hoc test. The highest shear bond belonged to group 2 (high intensity, 40 s, buccal) and the lowest belonged to group 3 (low intensity, 40 s, lingual). Bond strength means in control groups were significantly higher than those in experimental groups. In all experimental groups except group 6 (80 s, high intensity, lingual), shear bond strength was below the clinically accepted values. In clinical limitations where light curing from the same side of the bracket is not possible, doubling the curing time and increasing the light intensity during trans-illumination are recommended for achieving acceptable bond strengths.

Optimization of laboratory illumination in optical dating

DEFF Research Database (Denmark)

Sohbati, Reza; Murray, Andrew; Lindvold, Lars René

2017-01-01

As part of the development of new laboratory lighting, we present a methodological approach applicable to the characterization of any light source intended for illumination in optical dating laboratories. We derive optical absorption cross-sections for quartz and feldspar from published data......-emitting diodes (LEDs); this comparison demonstrates the significant advantage of the LED sources over the filtered light sources, because essentially all of the reduction of both OSL and IRSL signals by the LEDs occurs at wavelengths to which the human eye is most sensitive. We conclude that exposure of quartz...... and feldspar extracts from various samples to the light from an LED with emission peak at 594 nm results in a 1% OSL or IRSL signal loss for a 48-h exposure at a power density of ~0.2 mW.cm-2....

Infrared LED Array For Silicon Strip Detector Qualification

CERN Document Server

Dirkes, Guido; Hartmann, Frank; Heier, Stefan; Schwerdtfeger, Wolfgang; Waldschmitt, M; Weiler, K W; Weseler, Siegfried

2003-01-01

The enormous amount of silicon strip detector modules for the CMS tracker requires a test-sytem to allow qualification of each individual detector module and its front-end electronics within minutes. The objective is to test the detector with a physical signal. Signals are generated in the detector by illumination with lightpulses emitted by a LED at 950~nm and with a rise time of 10~ns. In order to avoid a detector moving, an array of 64 LEDs is used, overlaping the complete detector width. The total length of an array is 15~cm. The spot size of an individual LED is controlled by apertures to illuminate about 25 strips. Furthermore it is possible to simulate the high leakage current of irradiated sensors by constant illumination of the sensor. This provides an effective mean to identfy pinholes on a sensor.

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.

Improving high resolution retinal image quality using speckle illumination HiLo imaging.

Science.gov (United States)

Zhou, Xiaolin; Bedggood, Phillip; Metha, Andrew

2014-08-01

Retinal image quality from flood illumination adaptive optics (AO) ophthalmoscopes is adversely affected by out-of-focus light scatter due to the lack of confocality. This effect is more pronounced in small eyes, such as that of rodents, because the requisite high optical power confers a large dioptric thickness to the retina. A recently-developed structured illumination microscopy (SIM) technique called HiLo imaging has been shown to reduce the effect of out-of-focus light scatter in flood illumination microscopes and produce pseudo-confocal images with significantly improved image quality. In this work, we adopted the HiLo technique to a flood AO ophthalmoscope and performed AO imaging in both (physical) model and live rat eyes. The improvement in image quality from HiLo imaging is shown both qualitatively and quantitatively by using spatial spectral analysis.

Two-step design method for highly compact three-dimensional freeform optical system for LED surface light source.

Science.gov (United States)

Mao, Xianglong; Li, Hongtao; Han, Yanjun; Luo, Yi

2014-10-20

Designing an illumination system for a surface light source with a strict compactness requirement is quite challenging, especially for the general three-dimensional (3D) case. In accordance with the two key features of an expected illumination distribution, i.e., a well-controlled boundary and a precise illumination pattern, a two-step design method is proposed in this paper for highly compact 3D freeform illumination systems. In the first step, a target shape scaling strategy is combined with an iterative feedback modification algorithm to generate an optimized freeform optical system with a well-controlled boundary of the target distribution. In the second step, a set of selected radii of the system obtained in the first step are optimized to further improve the illuminating quality within the target region. The method is quite flexible and effective to design highly compact optical systems with almost no restriction on the shape of the desired target field. As examples, three highly compact freeform lenses with ratio of center height h of the lens and the maximum dimension D of the source ≤ 2.5:1 are designed for LED surface light sources to form a uniform illumination distribution on a rectangular, a cross-shaped and a complex cross pierced target plane respectively. High light control efficiency of η > 0.7 as well as low relative standard illumination deviation of RSD < 0.07 is obtained simultaneously for all the three design examples.

Ten Minutes of α-tACS and Ambient Illumination Independently Modulate EEG α-Power

Directory of Open Access Journals (Sweden)

Heiko I. Stecher

2017-05-01

Full Text Available Transcranial alternating current stimulation (tACS sees increased use in neurosciences as a tool for the exploration of brain oscillations. It has been shown that tACS stimulation in specific frequency bands can result in aftereffects of modulated oscillatory brain activity that persist after the stimulation has ended. The general relationship between persistency of the effect and duration of stimulation is sparsely investigated but previous research has shown that the occurrence of tACS aftereffects depends on the brain state before and during stimulation. Early alpha neurofeedback research suggests that particularly in the alpha band the responsiveness to a manipulation depends on the ambient illumination during measurement. Therefore, in the present study we assessed the brain’s susceptibility to tACS at the individual alpha frequency during darkness compared to ambient illumination. We measured alpha power after 10 min of stimulation in 30 participants while they continuously performed a visual vigilance task. Our results show that immediately after stimulation, the alpha power in the illumination condition for both the stimulated and sham group has increased by only about 7%, compared to about 20% in both groups in the ‘dark’ condition. For the group that did not receive stimulation, the power in darkness remained stable after stimulation, whereas the power in light increased by an additional 10% during the next 30 min. For the group that did receive stimulation, alpha power during these 30 min increased by another 11% in light and 22% in darkness. Since alpha power already increased by about 10% without stimulation, the effect of illumination does not seem to have interacted with the effect of stimulation. Instead, both effects seem to have added up linearly. Although our findings do not show that illumination-induced differences in oscillatory activity influence the susceptibility toward tACS, they stress the importance of

A wirelessly controlled implantable LED system for deep brain optogenetic stimulation

Science.gov (United States)

Rossi, Mark A.; Go, Vinson; Murphy, Tracy; Fu, Quanhai; Morizio, James; Yin, Henry H.

2015-01-01

In recent years optogenetics has rapidly become an essential technique in neuroscience. Its temporal and spatial specificity, combined with efficacy in manipulating neuronal activity, are especially useful in studying the behavior of awake behaving animals. Conventional optogenetics, however, requires the use of lasers and optic fibers, which can place considerable restrictions on behavior. Here we combined a wirelessly controlled interface and small implantable light-emitting diode (LED) that allows flexible and precise placement of light source to illuminate any brain area. We tested this wireless LED system in vivo, in transgenic mice expressing channelrhodopsin-2 in striatonigral neurons expressing D1-like dopamine receptors. In all mice tested, we were able to elicit movements reliably. The frequency of twitches induced by high power stimulation is proportional to the frequency of stimulation. At lower power, contraversive turning was observed. Moreover, the implanted LED remains effective over 50 days after surgery, demonstrating the long-term stability of the light source. Our results show that the wireless LED system can be used to manipulate neural activity chronically in behaving mice without impeding natural movements. PMID:25713516

High-performance LED luminaire for sports hall

Science.gov (United States)

Lee, Xuan-Hao; Yang, Jin-Tsung; Chien, Wei-Ting; Chang, Jung-Hsuan; Lo, Yi-Chien; Lin, Che-Chu; Sun, Ching-Cherng

2015-09-01

In this paper, we present a luminaire design with anti-glare and energy-saving effects for sports hall. Compared with traditional lamps using in a badminton court, the average illuminance on the ground of the proposed LED luminaire is enhanced about 300%. Besides, the uniformity is obviously enhanced and improved. The switch-on speed of lighting in sports hall is greatly reduced from 5-10 minutes to 1 second. The simulation analysis and the corresponding experiment results are demonstrated.

P1-15: Categorical Color Perception of LED Illuminant Color for Deuteranomals

Directory of Open Access Journals (Sweden)

Saeko Oishi

2012-10-01

Full Text Available Color information has great value in our everyday lives, but it is not mindful of people with color vision deficiency (CVD. We can choose several color names to categorize a lot of colors around us. Eleven color names (white, black, red, green, yellow, blue, brown, orange, pink, and gray are known as basic color categories, but people with CVD cannot necessarily describe colors as people who are color vision normal (CVN do. Previous studies showed that it was hard for people with CVD to discriminate illuminant color from object color, and their color perception changed largely depending on experimental conditions. In this study we investigated categorical color perception of illuminant color for deuteranomals, using a mixture of light which consists of a red, a green, and a blue LED as a test stimulus. We tested those stimuli with three luminance levels (180 cd/m2, 18 cd/m2, 1.8 cd/m2 and two visual angles (10 deg, 0.5 deg. Subjects were three deuteranomals and three people who are CVN. Our result showed that the categorical color of mild deuteranomals was similar to that of those who were CVN, but that of severe deuteranomals was not. Severe deuteranomals judged more low chromatic colors as achromatic colors than those who were CVN. The smaller visual angle or lower luminance level the test stimulus had, the more deuteranomals confused color. The results suggest that the effect of the Bezold-Brucke phenomenon is greater to deuteranomals than to those who are CVN. Furthermore, deuteranomals use not only chromatic information but also luminance information when they describe color.

LED-induced fluorescence diagnostics for turbine and combustion engine thermometry

International Nuclear Information System (INIS)

Allison, S.W.

2001-01-01

Fluorescence from phosphor coatings is the basis of an established technique for measuring temperature in a wide variety of turbine and combustion engine applications. Example surfaces include blades, vanes, combustors, intake valves, pistons, and rotors. Many situations that are remote and noncontact require the high intensity of a laser to illuminate the phosphor, especially if the surface is moving. Thermometric resolutions of 0.1 C are obtainable, and some laboratory versions of these systems have been calibrated against NIST standards to even higher precision. To improve the measurement signal-to-noise ratio, synchronous detection timing has been used to repeatedly interrogate the same blade in a high speed rotating turbine. High spatial resolution can be obtained by tightly focusing the interrogation beam in measurements of static surfaces, and by precise differential timing of the laser pulses on rotating surfaces. We report here the use of blue light emitting diodes (LEDs) as a n illumination source for producing useable fluorescence from phosphors for temperature measurements. An LED can excite most of the same phosphors used to cover the temperature range from 8 to 1400 C. The advantages of using LEDs are obvious in terms of size, power requirements, space requirements and cost. There can also be advantages associated with very long operating lifetimes, wide range of available colors, and their broader emission bandwidths as compared to laser diodes. Temperature may be inferred either from phase or time-decay determinations

Infrared LED Enhanced Spectroscopic CdZnTe Detector Working under High Fluxes of X-rays

Directory of Open Access Journals (Sweden)

Jakub Pekárek

2016-09-01

Full Text Available This paper describes an application of infrared light-induced de-polarization applied on a polarized CdZnTe detector working under high radiation fluxes. We newly demonstrate the influence of a high flux of X-rays and simultaneous 1200-nm LED illumination on the spectroscopic properties of a CdZnTe detector. CdZnTe detectors operating under high radiation fluxes usually suffer from the polarization effect, which occurs due to a screening of the internal electric field by a positive space charge caused by photogenerated holes trapped at a deep level. Polarization results in the degradation of detector charge collection efficiency. We studied the spectroscopic behavior of CdZnTe under various X-ray fluxes ranging between 5 × 10 5 and 8 × 10 6 photons per mm 2 per second. It was observed that polarization occurs at an X-ray flux higher than 3 × 10 6 mm − 2 ·s − 1 . Using simultaneous illumination of the detector by a de-polarizing LED at 1200 nm, it was possible to recover X-ray spectra originally deformed by the polarization effect.

THE PHOTODYNAMIC EFFECT OF LED-MAGNETIC EXPOSURE TO PHOTOINACTIVATION OF AEROBIC PHOTOSYNTETIC BACTERIA

Directory of Open Access Journals (Sweden)

Suryani Dyah Astuti

2014-01-01

Full Text Available All photosynthetic bacteria have a major pigment of bacteriochlorophyl and accessor pigment e.g. the carotenoids, which both have an important role in photosynthesis process. This study aim to explore the exogenous organic photosensitizer from photosyntetic bacteria for photodynamic therapy application. This study is an experimental research aiming to test the potential illumination ofLED with wavelength 409, 430, 528 and 629 nm, and power optimization and time exposure LED-magnetic for optimum photo activation Rhodococcus growth. The reseach design use a factorial completely randomized design with factor ofpower and exposure time. The number ofbacterial colonies grown measure using ofTotal Plate Count (TPC methods. The result ofanova test shows that irradiation treatment with LED 409 nm, 430 nm, 528 nm and 629 nm significantly affects on bacterial colony growth. LED 409 nm exposure has the greatest potential to boost the growth ofbacterial colonies by 77%. LED exposure and the addition of1.8 mT magnetic field increases bacterial colony growth by 98%. Results of optimization of LED and magnetic fields show power 46 mW and a 40 minute (energy dose 110 J/cm2 optimum growth ofbacterial colonies increase by 184%. So LED and magnetic illumination has potentially increased the viability ofan aerob photosyntetic bacteria colonies.

The High-efficiency LED Driver for Visible Light Communication Applications.

Science.gov (United States)

Gong, Cihun-Siyong Alex; Lee, Yu-Chen; Lai, Jyun-Liang; Yu, Chueh-Hao; Huang, Li Ren; Yang, Chia-Yen

2016-08-08

This paper presents a LED driver for VLC. The main purpose is to solve the low data rate problem used to be in switching type LED driver. The GaN power device is proposed to replace the traditional silicon power device of switching LED driver for the purpose of increasing switching frequency of converter, thereby increasing the bandwidth of data transmission. To achieve high efficiency, the diode-connected GaN power transistor is utilized to replace the traditional ultrafast recovery diode used to be in switching type LED driver. This work has been experimentally evaluated on 350-mA output current. The results demonstrate that it supports the data of PWM dimming level encoded in the PPM scheme for VLC application. The experimental results also show that system's efficiency of 80.8% can be achieved at 1-Mb/s data rate.

PV power system using hybrid converter for LED indictor applications

International Nuclear Information System (INIS)

Tseng, Sheng-Yu; Wang, Hung-Yuan; Chen, Chien-Chih

2013-01-01

Highlights: • This paper presents a LED indictor driving circuit with a PV arrays as its power source. • The perturb-and-observe method is adopted to extract the maximum power of PV arrays. • The proposed circuit structure has a less component counts and higher conversion efficiency. • A prototype of LED indictor driving circuit has been implemented to verify its feasibility. • The proposed hybrid converter is suitable for LED inductor applications. - Abstract: This paper presents a LED indictor driving circuit with a PV arrays as its power source. The LED indictor driving circuit includes battery charger and discharger (LED driving circuit). In this research, buck converter is used as a charger, and forward converter with active clamp circuit is adopted as a discharger to drive the LED indictor. Their circuit structures use switch integration technique to simplify them and to form the proposed hybrid converter, which has a less component counts, lighter weight, smaller size, and higher conversion efficiency. Moreover, the proposed hybrid converter uses a perturb-and-observe method to extract the maximum power from PV arrays. Finally, a prototype of an LED indictor driving circuit with output voltage of 10 V and output power of 20 W has been implemented to verify its feasibility. It is suitable for the LED inductor applications

Experimental study on the thermal management of high-power LED headlight cooling device integrated with thermoelectric cooler package

International Nuclear Information System (INIS)

Wang, Jing; Zhao, Xin-Jie; Cai, Yi-Xi; Zhang, Chun; Bao, Wei-Wei

2015-01-01

Highlights: • A novel TEC cooling system for multi-chip LED module was successfully developed. • Influences of liquid velocity on the system thermal performance were investigated. • TEC system is more sensitive to the input current than that of the mere air cooling. • The junction temperature can be maintained below 61.8 °C (liquid cooling & TEC). - Abstract: In view of the characteristics of high power light-emitting diodes (LEDs), such as strict junction temperature (T j ) control, the enhanced cooling models based on the thermoelectric cooler (TEC) were presented to meet the thermal demand of high-power LED headlight. The cooling performance of different devices (air cooling & TEC, liquid cooling & TEC) was evaluated and compared by measuring the LED case temperature. Details of the heat transfer performance, particularly, the start-up performances of the TEC cooler, as well as the influence of the fan rotate speed or liquid velocity on the system thermal performance were obtained. It was found that the thermal performance had been elevated dramatically due to the reduction of the hot side temperature, and the thermoelectric cooler was more sensitive to the external fan speed or liquid velocity than purely air cooling or liquid cooling. In addition, the optimal current for air cooling & TEC was 3A, and 5A for liquid cooling + TEC. Investigations of the simulated ambient temperature on junction temperature, forward voltage, and output light were conducted. Results indicated that the case temperature changed linear basically with the increase in heating power or the simulated ambient temperature. When the ambient temperature was within its severe level (60–65 °C), the junction temperature could be calculated to 59.5 °C, and the corresponding output light was 1607.3 lm

Inactivation/reactivation of antibiotic-resistant bacteria by a novel UVA/LED/TiO2 system.

Science.gov (United States)

Xiong, Pei; Hu, Jiangyong

2013-09-01

In this study, an effective photocatalytic disinfection system was established using the newly emerged high power UVA/LED lamp. Crystallizing dish coated with TiO2 was prepared by 32-times impregnation-drying processes, and served as the supporting container for water samples. This study focused on the application of this UVA/LED system for the photocatalytic disinfection of selected antibiotic-resistant bacteria, Escherichia coli ATCC 700891. The disinfection performances were studied under various light intensities and illumination modes. Results show that higher light intensity could reach more significant inactivation of E. coli ATCC 700891. With the same UV dose, log-removal of antibiotic-resistant bacteria decreased with circle time in the studied range, while increased with duty circle. A "residual disinfecting effect" was found in the following dark period for bacteria collected at different phases of photocatalytic process. Residual disinfecting effect was found not significant for bacteria with 30 min periodic illumination. While residual disinfecting effect could kill almost all bacteria after 90 min UV periodic illumination within the following 240 min dark period. Copyright © 2013 Elsevier Ltd. All rights reserved.

Monolayer graphene dispersion and radiative cooling for high power LED

Science.gov (United States)

Hsiao, Tun-Jen; Eyassu, Tsehaye; Henderson, Kimberly; Kim, Taesam; Lin, Chhiu-Tsu

2013-10-01

Molecular fan, a radiative cooling by thin film, has been developed and its application for compact electronic devices has been evaluated. The enhanced surface emissivity and heat dissipation efficiency of the molecular fan coating are shown to correlate with the quantization of lattice modes in active nanomaterials. The highly quantized G and 2D bands in graphene are achieved by our dispersion technique, and then incorporated in an organic-inorganic acrylate emulsion to form a coating assembly on heat sinks (for LED and CPU). This water-based dielectric layer coating has been formulated and applied on metal core printed circuit boards. The heat dissipation efficiency and breakdown voltage are evaluated by a temperature-monitoring system and a high-voltage breakdown tester. The molecular fan coating on heat dissipation units is able to decrease the equilibrium junction temperature by 29.1 ° C, while functioning as a dielectric layer with a high breakdown voltage (>5 kV). The heat dissipation performance of the molecular fan coating applied on LED devices shows that the coated 50 W LED gives an enhanced cooling of 20% at constant light brightness. The schematics of monolayer graphene dispersion, undispersed graphene platelet, and continuous graphene sheet are illustrated and discussed to explain the mechanisms of radiative cooling, radiative/non-radiative, and non-radiative heat re-accumulation.

Monolayer graphene dispersion and radiative cooling for high power LED

International Nuclear Information System (INIS)

Hsiao, Tun-Jen; Eyassu, Tsehaye; Henderson, Kimberly; Kim, Taesam; Lin, Chhiu-Tsu

2013-01-01

Molecular fan, a radiative cooling by thin film, has been developed and its application for compact electronic devices has been evaluated. The enhanced surface emissivity and heat dissipation efficiency of the molecular fan coating are shown to correlate with the quantization of lattice modes in active nanomaterials. The highly quantized G and 2D bands in graphene are achieved by our dispersion technique, and then incorporated in an organic-inorganic acrylate emulsion to form a coating assembly on heat sinks (for LED and CPU). This water-based dielectric layer coating has been formulated and applied on metal core printed circuit boards. The heat dissipation efficiency and breakdown voltage are evaluated by a temperature-monitoring system and a high-voltage breakdown tester. The molecular fan coating on heat dissipation units is able to decrease the equilibrium junction temperature by 29.1 ° C, while functioning as a dielectric layer with a high breakdown voltage (>5 kV). The heat dissipation performance of the molecular fan coating applied on LED devices shows that the coated 50 W LED gives an enhanced cooling of 20% at constant light brightness. The schematics of monolayer graphene dispersion, undispersed graphene platelet, and continuous graphene sheet are illustrated and discussed to explain the mechanisms of radiative cooling, radiative/non-radiative, and non-radiative heat re-accumulation. (paper)

Illumination influences working memory: an EEG study.

Science.gov (United States)

Park, Jin Young; Min, Byoung-Kyong; Jung, Young-Chul; Pak, Hyensou; Jeong, Yeon-Hong; Kim, Eosu

2013-09-05

Illumination conditions appear to influence working efficacy in everyday life. In the present study, we obtained electroencephalogram (EEG) correlates of working-memory load, and investigated how these waveforms are modulated by illumination conditions. We hypothesized that illumination conditions may affect cognitive performance. We designed an EEG study to monitor and record participants' EEG during the Sternberg working memory task under four different illumination conditions. Illumination conditions were generated with a factorial design of two color-temperatures (3000 and 7100 K) by two illuminance levels (150 and 700 lx). During a working memory task, we observed that high illuminance led to significantly lower frontal EEG theta activity than did low illuminance. These differences persisted despite no significant difference in task performance between illumination conditions. We found that the latency of an early event-related potential component, such as N1, was significantly modulated by the illumination condition. The fact that the illumination condition affects brain activity but not behavioral performance suggests that the lighting conditions used in the present study did not influence the performance stage of behavioral processing. Nevertheless, our findings provide objective evidence that illumination conditions modulate brain activity. Further studies are necessary to refine the optimal lighting parameters for facilitating working memory. Copyright © 2013 IBRO. Published by Elsevier Ltd. All rights reserved.

Head-mounted LED for optogenetic experiments of freely-behaving animal

Science.gov (United States)

Kwon, Ki Yong; Gnade, Andrew G.; Rush, Alexander D.; Patten, Craig D.

2016-03-01

Recent developments in optogenetics have demonstrated the ability to target specific types of neurons with sub-millisecond temporal precision via direct optical stimulation of genetically modified neurons in the brain. In most applications, the beam of a laser is coupled to an optical fiber, which guides and delivers the optical power to the region of interest. Light emitting diodes (LEDs) are an alternative light source for optogenetics and they provide many advantages over a laser based system including cost, size, illumination stability, and fast modulation. Their compact size and low power consumption make LEDs suitable light sources for a wireless optogenetic stimulation system. However, the coupling efficiency of an LED's output light into an optical fiber is lower than a laser due to its noncollimated output light. In typical chronic optogenetic experiment, the output of the light source is transmitted to the brain through a patch cable and a fiber stub implant, and this configuration requires two fiber-to-fiber couplings. Attenuation within the patch cable is potential source of optical power loss. In this study, we report and characterize a recently developed light delivery method for freely-behaving animal experiments. We have developed a head-mounted light source that maximizes the coupling efficiency of an LED light source by eliminating the need for a fiber optic cable. This miniaturized LED is designed to couple directly to the fiber stub implant. Depending on the desired optical power output, the head-mounted LED can be controlled by either a tethered (high power) or battery-powered wireless (moderate power) controller. In the tethered system, the LED is controlled through 40 gauge micro coaxial cable which is thinner, more flexible, and more durable than a fiber optic cable. The battery-powered wireless system uses either infrared or radio frequency transmission to achieve real-time control. Optical, electrical, mechanical, and thermal

The design of optical module of LED street lamp with non-axial symmetrical reflector

Science.gov (United States)

Lu, Ming-Jun; Chen, Chi-An; Chen, Yi-Yung; Whang, Allen Jong-Woei

2010-05-01

In recently, many research focus on the LED applications for environmental protection so a number of LED street lamps are presented. Although LED has many advantages for environmental protection, its special optical characteristics, such as intensity distribution, always limit the advantages in many applications. Therefore, we always need to do the secondary optical design for LED street lamp to replace the traditional optical designs that are designed for high-pressure sodium lamps and mercury lamps. According to the situation, we design an optical module of LED street lamp with LEDs and secondary optical design. First, the LEDs are placed on freeform reflector for the specific illuminated conditions. We design the optical module of street lamp with the two conditions that include the uniformity and the ratio of length to width in the illuminated area and without any light pollution. According to the simulation with the designed optical module, the uniformity in the illuminated area is about 0.6 that is better than the general condition, 0.3, and the ratio of length to width in the illuminated area is 3:1 in which the length is 30 meters and the width is 10 meters. Therefore, the design could let LED street lamp fits the two conditions, uniformity and ratio in the illuminated area.

Automatic residue removal for high-NA extreme illumination

Science.gov (United States)

Moon, James; Nam, Byong-Sub; Jeong, Joo-Hong; Kong, Dong-Ho; Nam, Byung-Ho; Yim, Dong Gyu

2007-10-01

An epidemic for smaller node has been that, as the device architecture shrinks, lithography process requires high Numerical Aperture (NA), and extreme illumination system. This, in turn, creates many lithography problems such as low lithography process margin (Depth of Focus, Exposure Latitude), unstable Critical Dimension (CD) uniformity and restricted guideline for device design rule and so on. Especially for high NA, extreme illumination such as immersion illumination systems, above all the related problems, restricted design rule due to forbidden pitch is critical and crucial issue. This forbidden pitch is composed of numerous optical effects but majority of these forbidden pitch compose of photo resist residue and these residue must be removed to relieve some room for already tight design rule. In this study, we propose automated algorithm to remove photo resist residue due to high NA and extreme illumination condition. This algorithm automatically self assembles assist patterns based on the original design layout, therefore insuring the safety and simplicity of the generated assist pattern to the original design and removes any resist residue created by extreme illumination condition. Also we tested our automated algorithm on full chip FLASH memory device and showed the residue removal effect by using commercial verification tools as well as on actual test wafer.

Light emitting diodes as an alternative ambient illumination source in photolithography environment

DEFF Research Database (Denmark)

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

2009-01-01

We explored an alternative light emitting diode (LED) - based solution to replace the existing yellow fluorescent light tubes (YFT) used in photolithography rooms. A no-blue LED lamp was designed and a prototype was fabricated. For both solutions, the spectral power distribution (SPD) was measured......, the colorimetric values were calculated, and a visual comparison using Gretagmacbeth colorcharts was performed. The visual comparison showed that the LED bulb was better to render colors despite a low color rendering index (CRI). Furthermore, the LED bulb was tested in a photolithography room...... and there was no exposure to the photoresist even after 168 hours illumination....

Scalable single point power extraction for compact mobile and stand-alone solar harvesting power sources based on fully printed organic photovoltaic modules and efficient high voltage DC/DC conversion

DEFF Research Database (Denmark)

Garcia Valverde, Rafael; Villarejo, José A.; Hösel, Markus

2015-01-01

(AM1.5G, 1000 W m−2). As a demonstration we present a scalable fully integrated and compact power unit for mobile applications comprising solar energy harvesting OPV modules, power conversion and storage. Applications possible include electrical charging of mobile devices, illumination using LED lamps...

Chromatic illumination discrimination ability reveals that human colour constancy is optimised for blue daylight illuminations.

Directory of Open Access Journals (Sweden)

Bradley Pearce

Full Text Available The phenomenon of colour constancy in human visual perception keeps surface colours constant, despite changes in their reflected light due to changing illumination. Although colour constancy has evolved under a constrained subset of illuminations, it is unknown whether its underlying mechanisms, thought to involve multiple components from retina to cortex, are optimised for particular environmental variations. Here we demonstrate a new method for investigating colour constancy using illumination matching in real scenes which, unlike previous methods using surface matching and simulated scenes, allows testing of multiple, real illuminations. We use real scenes consisting of solid familiar or unfamiliar objects against uniform or variegated backgrounds and compare discrimination performance for typical illuminations from the daylight chromaticity locus (approximately blue-yellow and atypical spectra from an orthogonal locus (approximately red-green, at correlated colour temperature 6700 K, all produced in real time by a 10-channel LED illuminator. We find that discrimination of illumination changes is poorer along the daylight locus than the atypical locus, and is poorest particularly for bluer illumination changes, demonstrating conversely that surface colour constancy is best for blue daylight illuminations. Illumination discrimination is also enhanced, and therefore colour constancy diminished, for uniform backgrounds, irrespective of the object type. These results are not explained by statistical properties of the scene signal changes at the retinal level. We conclude that high-level mechanisms of colour constancy are biased for the blue daylight illuminations and variegated backgrounds to which the human visual system has typically been exposed.

Simulation and comparison of the illuminance, uniformity, and efficiency of different forms of lighting used in basketball court illumination.

Science.gov (United States)

Sun, Wen-Shing; Tien, Chuen-Lin; Tsuei, Chih-Hsuan; Pan, Jui-Wen

2014-10-10

We simulate and compare the illuminance, uniformity, and efficiency of metal-halide lamps, white LED light sources, and hybrid light box designs combining sunlight and white LED lighting used for indoor basketball court illumination. According to the optical simulation results and our examination of real situations, we find that hybrid light box designs combining sunlight and white LEDs do perform better than either metal-halide lamps or white LED lights. An evaluation of the sunlight concentrator system used in our inverted solar cell shows that the energy consumption of stadium lighting can be reduced significantly.

Advanced laser architectures for high power eyesafe illuminators

Science.gov (United States)

Baranova, N.; Pati, B.; Stebbins, K.; Bystryak, I.; Rayno, M.; Ezzo, K.; DePriest, C.

2018-02-01

Q-Peak has demonstrated a novel pulsed eyesafe laser architecture operating with >50 mJ pulse energies at Pulse Repetition Frequencies (PRFs) as high as 320 Hz. The design leverages an Optical Parametric Oscillator (OPO) and Optical Parametric Amplifier (OPA) geometry, which provides the unique capability for high power in a comparatively compact package, while also offering the potential for additional eyesafe power scaling. The laser consists of a Commercial Off-the-Shelf (COTS) Q-switched front-end seed laser to produce pulse-widths around 10 ns at 1.06-μm, which is then followed by a pair of Multi-Pass Amplifier (MPA) architectures (comprised of side-pumped, multi-pass Nd:YAG slabs with a compact diode-pump-array imaging system), and finally involving two sequential nonlinear optical conversion architectures for transfer into the eyesafe regime. The initial seed beam is first amplified through the MPA, and then split into parallel optical paths. An OPO provides effective nonlinear conversion on one optical path, while a second MPA further amplifies the 1.06-μm beam for use in pumping an OPA on the second optical path. These paths are then recombined prior to seeding the OPA. Each nonlinear conversion subsystem utilizes Potassium Titanyl Arsenate (KTA) for effective nonlinear conversion with lower risk to optical damage. This laser architecture efficiently produces pulse energies of >50 mJ in the eyesafe band at PRFs as high as 320 Hz, and has been designed to fit within a volume of 4,500 in3 (0.074 m3 ). We will discuss theoretical and experimental details of the nonlinear optical system for achieving higher eyesafe powers.

Two phase interleaved buck converter for driving high power LEDs

DEFF Research Database (Denmark)

Beczkowski, Szymon; Munk-Nielsen, Stig

2011-01-01

The goal of this paper is to evaluate an interleaved buck topology for driving high current light-emitting diodes. Low output capacitor value allows the use of non-electrolytic capacitors extending the lifetime of the converter. Converter is operated as a constant, regulated current source which...... increases luminous efficacy of LED compared to PWM dimmed system. Because of the low dynamic resistance of LEDs the duty cycle of the converter does not change greatly with controlled current. By setting the input voltage of the buck converter to around twice the voltage of diode strings, converter can...

Antibacterial effect of light emitting diodes of visible wavelengths on selected foodborne pathogens at different illumination temperatures.

Science.gov (United States)

Ghate, Vinayak S; Ng, Kheng Siang; Zhou, Weibiao; Yang, Hyunsoo; Khoo, Gek Hoon; Yoon, Won-Byong; Yuk, Hyun-Gyun

2013-09-16

The antibacterial effect of light emitting diodes (LEDs) in the visible region (461, 521 and 642 nm) of the electromagnetic spectrum was investigated on Escherichia coli O157:H7, Salmonella typhimurium, Listeria monocytogenes and Staphylococcus aureus. The irradiances of the 461, 521 and 642 nm LEDs were 22.1, 16 and 25.4 mW/cm², respectively. Bacterial cultures suspended in tryptic soy broth were illuminated by 10-watt LEDs at a distance of 4.5 cm for 7.5h at 20, 15 and 10 °C. Regardless of the bacterial strains, bacterial inactivation was observed with the range of 4.6-5.2 logCFU/ml at 10 and 15 °C after illumination with the 461 nm LED, while illumination with the 521 nm LED resulted in only 1.0-2.0 log reductions after 7.5h. On the other hand, no antibacterial effect was observed using the 642 nm LED treatment. The photodynamic inactivation by 461 and 521 nm LEDs was found to be greater at the set temperatures of 10 and 15 °C than at 20 °C. The D-values for the four bacterial strains at 10 and 15 °C after the illumination of 461 nm LED ranged from 1.29 to 1.74 h, indicating that there was no significant difference in the susceptibility of the bacterial strains to the LED illumination between 10 and 15 °C, except for L. monocytogenes. Regardless of the illumination temperature, sublethal injury was observed in all bacterial strains during illumination with the 461 and the 521 nm LED and the percentage of injured cells increased as the treatment time increased. Thus, the results show that the antibacterial effect of the LEDs was highly dependent on the wavelength and the illumination temperature. This study suggests the potential of 461 and 521 nm LEDs in combination with chilling to be used as a novel food preservation technology. © 2013 Elsevier B.V. All rights reserved.

Design and implementation of a high dimming ratio LED drive controller

International Nuclear Information System (INIS)

Xu Xiaoru; Wu Xiaobo; Zhao Menglian; Yan Xiaolang

2009-01-01

This paper presents a high dimming ratio light emitting diode (LED) drive controller chip with digital mode dimming (DMD). The chip is composed of a boost power converter and a dimming control block. A novel constant on time (COT) control strategy is proposed for boost converter to achieve high dimming ratio. In addition, a fast enough load transient response of the converter power stage ensures its high dimming ratio. The COT control circuit operates mainly based on two current-capacitor timers and a finite state machine (FSM). The LED drive controller chip is designed and fabricated in 1.5 μm bipolar CMOS-DMOS (BCD) process with a die area of 1.31 x 1.43 mm 2 . Experimental results show that the proposed LED drive system works well. And, as expected, the minimum LED dimming on time of 1.0 μs and the corresponding dimming ratio of 1000:1 at 1 kHz dimming frequency are successfully achieved.

Analysis of the transient response of LED-illuminated diodes under heavy radiation damage

CERN Document Server

Passeri, D; Bilei, G M; Casse, G L; Lemeilleur, F

2000-01-01

The changes of the electrical properties induced by hadron irradiation on silicon detectors have been studied by using the device level simulator HFIELDS. The model of the radiation damage assumes the introduction of radiation-induced acceptor and donor "deep-levels". The electric field profile and the space charge region extension have been calculated for differently irradiated structures. The simulation has been carried out at different biases in order to study the evolution of the space charge region of irradiated detectors as a function of the applied voltages, below and above the full depletion. The time-dependent current responses and the charge collection properties of the structure illuminated by a red LED light have been calculated. The use of the red light results in a shallow (quasi-surface) generation of e-h pairs in silicon, which has been properly taken into account by the simulation. The results of the simulations have been compared to experimental measurements carried out at CERN on samples ir...

Implementation and Test of a LED-Based Lamp for a Lighthouse

Directory of Open Access Journals (Sweden)

Luca Mercatelli

2014-01-01

Full Text Available A novel sustainable source was developed for an existing Italian lighthouse, exploiting the light emitting diode (LED technology and the norms evolution. The research work started with the optical design of the device, while this work concerns the realization, installation, and test of the new LED lamp. The lamp recombines multiple separated LEDs, realizing a quasipunctual localized source. After installation in the lighthouse, specific photometric tests verified that the proposed power-saving source satisfied the illumination requirements of the marine signaling norms. The advantages of the LED-based lamp are reduced energy consumption, enhanced efficiency, longer life, decreased faults, slower aging, and lower maintenance costs. The obtained LED signalling device is more durable and reliable. In the future the application of these power-saving long-life sources could be extended to other maritime signaling devices or to other traffic signs.

Monolithic blue LED series arrays for high-voltage AC operation

Energy Technology Data Exchange (ETDEWEB)

Ao, Jin-Ping [Satellite Venture Business Laboratory, University of Tokushima, Tokushima 770-8506 (Japan); Sato, Hisao; Mizobuchi, Takashi; Morioka, Kenji; Kawano, Shunsuke; Muramoto, Yoshihiko; Sato, Daisuke; Sakai, Shiro [Nitride Semiconductor Co. Ltd., Naruto, Tokushima 771-0360 (Japan); Lee, Young-Bae; Ohno, Yasuo [Department of Electrical and Electronic Engineering, University of Tokushima, Tokushima 770-8506 (Japan)

2002-12-16

Design and fabrication of monolithic blue LED series arrays that can be operated under high ac voltage are described. Several LEDs, such as 3, 7, and 20, are connected in series and in parallel to meet ac operation. The chip size of a single device is 150 {mu}m x 120 {mu}m and the total size is 1.1 mm x 1 mm for a 40(20+20) LED array. Deep dry etching was performed as device isolation. Two-layer interconnection and air bridge are utilized to connect the devices in an array. The monolithic series array exhibit the expected operation function under dc and ac bias. The output power and forward voltage are almost proportional to LED numbers connected in series. On-wafer measurement shows that the output power is 40 mW for 40(20+20) LED array under ac 72 V. (Abstract Copyright [2002], Wiley Periodicals, Inc.)

Converting a conventional wired-halogen illuminated indirect ophthalmoscope to a wireless-light emitting diode illuminated indirect ophthalmoscope in less than 1000/- rupees

Directory of Open Access Journals (Sweden)

Mihir Kothari

2015-01-01

Full Text Available Aim: To report the "do it yourself" method of converting an existing wired-halogen indirect ophthalmoscope (IO to a wireless-light emitting diode (LED IO and report the preferences of the patients and the ophthalmologists. Subjects and Methods: In this prospective observational study, a conventional IO was converted to wireless-LED IO using easily available, affordable electrical components. Conventional and the converted IO were then used to perform photo-stress test and take the feedback of subjects and the ophthalmologists regarding its handling and illumination characteristics. Results: The cost of conversion to wireless-LED was 815/- rupees. Twenty-nine subjects, mean age 34.3 ΁ 10 years with normal eyes were recruited in the study. Between the two illumination systems, there was no statistical difference in the magnitude of the visual acuity loss and the time to recovery of acuity and the bleached vision on photo-stress test, although the visual recovery was clinically faster with LED illumination. The heat sensation was more with halogen illumination than the LED (P = 0.009. The ophthalmologists rated wireless-LED IO higher than wired-halogen IO on the handling, examination comfort, patient′s visual comfort and quality of the image. Twenty-two (81% ophthalmologists wanted to change over to wireless-LED IO. Conclusions: Converting to wireless-LED IO is easy, cost-effective and preferred over a wired-halogen indirect ophthalmoscope.

Converting a conventional wired-halogen illuminated indirect ophthalmoscope to a wireless-light emitting diode illuminated indirect ophthalmoscope in less than 1000/- rupees.

Science.gov (United States)

Kothari, Mihir; Kothari, Kedar; Kadam, Sanjay; Mota, Poonam; Chipade, Snehal

2015-01-01

To report the "do it yourself" method of converting an existing wired-halogen indirect ophthalmoscope (IO) to a wireless-light emitting diode (LED) IO and report the preferences of the patients and the ophthalmologists. In this prospective observational study, a conventional IO was converted to wireless-LED IO using easily available, affordable electrical components. Conventional and the converted IO were then used to perform photo-stress test and take the feedback of subjects and the ophthalmologists regarding its handling and illumination characteristics. The cost of conversion to wireless-LED was 815/- rupees. Twenty-nine subjects, mean age 34.3 [formula in text] 10 years with normal eyes were recruited in the study. Between the two illumination systems, there was no statistical difference in the magnitude of the visual acuity loss and the time to recovery of acuity and the bleached vision on photo-stress test, although the visual recovery was clinically faster with LED illumination. The heat sensation was more with halogen illumination than the LED (P = 0.009). The ophthalmologists rated wireless-LED IO higher than wired-halogen IO on the handling, examination comfort, patient's visual comfort and quality of the image. Twenty-two (81%) ophthalmologists wanted to change over to wireless-LED IO. Converting to wireless-LED IO is easy, cost-effective and preferred over a wired-halogen indirect ophthalmoscope.

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

Functional Analysis in Long-Term Operation of High Power UV-LEDs in Continuous Fluoro-Sensing Systems for Hydrocarbon Pollution

Science.gov (United States)

Arques-Orobon, Francisco Jose; Nuñez, Neftali; Vazquez, Manuel; Gonzalez-Posadas, Vicente

2016-01-01

This work analyzes the long-term functionality of HP (High-power) UV-LEDs (Ultraviolet Light Emitting Diodes) as the exciting light source in non-contact, continuous 24/7 real-time fluoro-sensing pollutant identification in inland water. Fluorescence is an effective alternative in the detection and identification of hydrocarbons. The HP UV-LEDs are more advantageous than classical light sources (xenon and mercury lamps) and helps in the development of a low cost, non-contact, and compact system for continuous real-time fieldwork. This work analyzes the wavelength, output optical power, and the effects of viscosity, temperature of the water pollutants, and the functional consistency for long-term HP UV-LED working operation. To accomplish the latter, an analysis of the influence of two types 365 nm HP UV-LEDs degradation under two continuous real-system working mode conditions was done, by temperature Accelerated Life Tests (ALTs). These tests estimate the mean life under continuous working conditions of 6200 h and for cycled working conditions (30 s ON & 30 s OFF) of 66,000 h, over 7 years of 24/7 operating life of hydrocarbon pollution monitoring. In addition, the durability in the face of the internal and external parameter system variations is evaluated. PMID:26927113

Method of controlling illumination device based on current-voltage model

DEFF Research Database (Denmark)

2013-01-01

The present invention relates to an illumination device comprising a number of LEDs, means for receiving an input signal, means for generating an activation signal for at least one of the LEDs based on the input signal. The illumination device comprises further means for obtaining the voltage...... and the colorimetric properties of said light emitted by LED. The present invention relates also to a method of controlling and a meted of calibrating such illumination device....... across and current through the LED and the means for generating the activation signal is adapted to generate the activating signal based on the voltage, the current and a current- voltage model related to LED. The current-voltage model defines a relationship between the current, the voltage...

Light-Emitting Diode-Based Illumination System for In Vitro Photodynamic Therapy

Directory of Open Access Journals (Sweden)

Defu Chen

2012-01-01

Full Text Available The aim of this study is to develop a light-emitting diode- (LED- based illumination system that can be used as an alternative light source for in vitro photodynamic therapy (PDT. This illumination system includes a red LED array composed of 70 LEDs centered at 643 nm, an air-cooling unit, and a specific-designed case. The irradiance as a function of the irradiation distance between the LED array and the sample, the homogeneity and stability of irradiation, and the effect of long-time irradiation on culture medium temperature were characterized. Furthermore, the survival rate of the CNE1 cells that sensitized with 5-aminolevulinic acid after PDT treatment was evaluated to demonstrate the efficiency of the new LED-based illumination system. The obtained results show that the LED-based illumination system is a promising light source for in vitro PDT that performed in standard multiwell plate.

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

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.

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.

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.

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.

LED-pumped Alexandrite laser oscillator and amplifier

Science.gov (United States)

Pichon, Pierre; Blanchot, Jean-Philippe; Balembois, François; Druon, Frédéric; Georges, Patrick

2018-02-01

In this paper, we report the first LED-pumped transition-metal-doped laser oscillator and amplifier based on an alexandrite crystal (Cr3+:BeAl2O4). A Ce:YAG luminescent concentrator illuminated by blue LEDs is used to reach higher pump powers than with LEDs alone. The luminescent 200-mm-long-composit luminescent concentrator involving 2240 LEDs can delivers up to 268 mJ for a peak irradiance of 8.5 kW/cm2. In oscillator configuration, an LED-pumped alexandrite laser delivering an energy of 2.9 mJ at 748 nm in free running operation is demonstrated. In the cavity, we measured a double pass small signal gain of 1.28, in good agreement with numerical simulations. As amplifier, the system demonstrated to boost a CW Ti:sapphire laser by a factor of 4 at 750 nm in 8 passes with a large tuning range from 710 nm to 800 nm.

Study on the Thermal Resistance of Multi-chip Module High Power LED Packaging Heat Dissipation System

Directory of Open Access Journals (Sweden)

Kailin Pan

2014-10-01

Full Text Available Thermal resistance is a key technical index which indicates the thermal management of multi-chip module high power LED (MCM-LED packaging heat dissipation system. In this paper, the prototype structure of MCM-LED packaging heat dissipation system is proposed to study the reliable thermal resistance calculation method. In order to analyze the total thermal resistance of the MCM-LED packaging heat dissipation system, three kinds of thermal resistance calculation method including theoretical calculation, experimental testing and finite element simulation are developed respectively. Firstly, based on the thermal resistance network model and the principle of steady state heat transfer, the theoretical value of total thermal resistance is 6.111 K/W through sum of the thermal resistance of every material layer in the major direction of heat flow. Secondly, the thermal resistance experiment is carried out by T3Ster to obtain the experimental result of total thermal resistance, and the value is 6.729 K/W. Thirdly, a three-dimensional finite element model of MCM-LED packaging heat dissipation system is established, and the junction temperature experiment is also performed to calculated the finite element simulated result of total thermal resistance, the value is 6.99 K/W. Finally, by comparing the error of all the three kinds of result, the error of total thermal resistance between the theoretical value and experimental result is 9.2 %, and the error of total thermal resistance between the experimental result and finite element simulation is only about -3.9 %, meanwhile, the main reason of each error is discussed respectively.

Notes on LED Installations in Street Illumination

Directory of Open Access Journals (Sweden)

Elisabeta Spunei

2014-09-01

Full Text Available The paper presents a study made on choosing LED street lighting installations, such that the quality requirements for exterior artificial lighting are fulfilled. We analyze two types of LED street lighting installations from a technical point of view, together with lighting level and brightness values obtained during the measurements. Following on the field measurements, the lighting quality parameters are calculated, and, for the lighting installation with the best performance, optimal mounting suggestions are made. The optimal quality parameters are calculated by simulations using the Dialux software. The same software and the same light sources we also compute an optimal street lighting by determining the size of the installation that provides the best lighting parameter values.

Improved power quality based high brightness LED lamp driver

African Journals Online (AJOL)

user

consists of a PFC Cuk DC-DC converter which operates in continuous conduction mode (CCM) to improve the ... In proposed LED driver as shown in Figure 1, a Cuk buck boost AC-DC converter ... Design and Analysis of Proposed LED Driver.

A filter bank approach for LED illumintaion sensing based on frequency division multiplexing

NARCIS (Netherlands)

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

2009-01-01

In this work, we consider illumination sensing in a light emitting diode (LED) based illumination system that normally consists of a large number of LEDs. Illumination sensing is used in order to facilitate the control of such system whose complexity, due to the large number of LEDs, can be quite

High-Power 365 nm UV LED Mercury Arc Lamp Replacement for Photochemistry and Chemical Photolithography.

Science.gov (United States)

Hölz, K; Lietard, J; Somoza, M M

2017-01-03

Ultraviolet light emitting diodes (UV LEDs) have become widespread in chemical research as highly efficient light sources for photochemistry and photopolymerization. However, in more complex experimental setups requiring highly concentrated light and highly spatially resolved patterning of the light, high-pressure mercury arc lamps are still widely used because they emit intense UV light from a compact arc volume that can be efficiently coupled into optical systems. Advances in the deposition and p -type doping of gallium nitride have recently permitted the manufacture of UV LEDs capable of replacing mercury arc lamps also in these applications. These UV LEDs exceed the spectral radiance of mercury lamps even at the intense I-line at 365 nm. Here we present the successful exchange of a high-pressure mercury arc lamp for a new generation UV LED as a light source in photolithographic chemistry and its use in the fabrication of high-density DNA microarrays. We show that the improved light radiance and efficiency of these LEDs offer substantial practical, economic and ecological advantages, including faster synthesis, lower hardware costs, very long lifetime, an >85-fold reduction in electricity consumption and the elimination of mercury waste and contamination.

Reliability test and failure analysis of high power LED packages

International Nuclear Information System (INIS)

Chen Zhaohui; Zhang Qin; Wang Kai; Luo Xiaobing; Liu Sheng

2011-01-01

A new type application specific light emitting diode (LED) package (ASLP) with freeform polycarbonate lens for street lighting is developed, whose manufacturing processes are compatible with a typical LED packaging process. The reliability test methods and failure criterions from different vendors are reviewed and compared. It is found that test methods and failure criterions are quite different. The rapid reliability assessment standards are urgently needed for the LED industry. 85 0 C/85 RH with 700 mA is used to test our LED modules with three other vendors for 1000 h, showing no visible degradation in optical performance for our modules, with two other vendors showing significant degradation. Some failure analysis methods such as C-SAM, Nano X-ray CT and optical microscope are used for LED packages. Some failure mechanisms such as delaminations and cracks are detected in the LED packages after the accelerated reliability testing. The finite element simulation method is helpful for the failure analysis and design of the reliability of the LED packaging. One example is used to show one currently used module in industry is vulnerable and may not easily pass the harsh thermal cycle testing. (semiconductor devices)

LEDs Illuminate Bulbs for Better Sleep, Wake Cycles

Science.gov (United States)

2015-01-01

Life on the International Space Station (ISS) wreaks havoc on an astronaut’s biological rhythms, and one way NASA mitigates the problem is through the use of LED lighting to alternately stimulate energy and focus and induce relaxation. Satellite Beach, Florida-based Lighting Science partnered with Kennedy Space Center to commercialize an LED system designed for the ISS, resulting in its DefinityDigital product line of light bulbs now used in numerous homes, hotel chains, and resorts.

Visual ergonomic evaluations on four different designs of LED traffic signs

Science.gov (United States)

Chen, Yi-Chun; Huang, Ting-Yuan; Lee, Tsung-Xian; Sun, Ching-Cherng

2017-08-01

To investigate the legibility and visual comfort of LED traffic signs, an ergonomic experiment is performed on four custom-designed LED traffic signs, including three self-luminous ones as LED lightbox, LED backlight and regional LED backlight, and one non-self-luminous sign with external LED lighting. The four signs are hanged side-by-side and evaluated by observers through questionnaires. The signage dimension is one-sixth of the real freeway traffic signs, and the observation distance is 25 m. The luminance of three self-luminous signs is 216 cd/m2. The illuminance of external LED lighting is 400 lux on the traffic sign. The ambient illuminance is 2.8 and 6.0 lux in two rounds. The results show that self-luminous traffic signs provide superior legibility, visual comfort and user preference than the non-self-luminous one. Among the three self-luminous signs, regional LED backlight is most susceptible to the ambient illumination. LED lightbox has significantly better preference score than LED backlight under darker ambient lighting. Only LED lightbox has significantly better visual comfort than external LED lighting in the brighter environment. Based on the four LED traffic signs evaluated in this study, we suggest LED lightbox as the prior choice. Further investigations on the effect of ambient illumination and other designs of self-luminous traffic signs are in progress.

Recycled Thermal Energy from High Power Light Emitting Diode Light Source.

Science.gov (United States)

Ji, Jae-Hoon; Jo, GaeHun; Ha, Jae-Geun; Koo, Sang-Mo; Kamiko, Masao; Hong, JunHee; Koh, Jung-Hyuk

2018-09-01

In this research, the recycled electrical energy from wasted thermal energy in high power Light Emitting Diode (LED) system will be investigated. The luminous efficiency of lights has been improved in recent years by employing the high power LED system, therefore energy efficiency was improved compared with that of typical lighting sources. To increase energy efficiency of high power LED system further, wasted thermal energy should be re-considered. Therefore, wasted thermal energy was collected and re-used them as electrical energy. The increased electrical efficiency of high power LED devices was accomplished by considering the recycled heat energy, which is wasted thermal energy from the LED. In this work, increased electrical efficiency will be considered and investigated by employing the high power LED system, which has high thermal loss during the operating time. For this research, well designed thermoelement with heat radiation system was employed to enhance the collecting thermal energy from the LED system, and then convert it as recycled electrical energy.

Effect of reduced exposure times on the cytotoxicity of resin luting cements cured by high-power led

Directory of Open Access Journals (Sweden)

Gulfem Ergun

2011-06-01

Full Text Available OBJECTIVE: Applications of resin luting agents and high-power light-emitting diodes (LED light-curing units (LCUs have increased considerably over the last few years. However, it is not clear whether the effect of reduced exposure time on cytotoxicity of such products have adequate biocompatibility to meet clinical success. This study aimed at assessing the effect of reduced curing time of five resin luting cements (RLCs polymerized by high-power LED curing unit on the viability of a cell of L-929 fibroblast cells. MATERIAL AND METHODS: Disc-shaped samples were prepared in polytetrafluoroethylene moulds with cylindrical cavities. The samples were irradiated from the top through the ceramic discs and acetate strips using LED LCU for 20 s (50% of the manufacturer's recommended exposure time and 40 s (100% exposure time. After curing, the samples were transferred into a culture medium for 24 h. The eluates were obtained and pipetted onto L-929 fibroblast cultures (3x10(4 per well and incubated for evaluating after 24 h. Measurements were performed by dimethylthiazol diphenyltetrazolium assay. Statistical significance was determined by two-way ANOVA and two independent samples were compared by t-test. RESULTS: Results showed that eluates of most of the materials polymerized for 20 s (except Rely X Unicem and Illusion reduced to a higher extent cell viability compared to samples of the same materials polymerized for 40 s. Illusion exhibited the least cytotoxicity for 20 s exposure time compared to the control (culture without samples followed by Rely X Unicem and Rely X ARC (90.81%, 88.90%, and 83.11%, respectively. For Rely X ARC, Duolink and Lute-It 40 s exposure time was better (t=-1.262 p=0,276; t=-9.399 p=0.001; and t=-20.418 p<0.001, respectively. CONCLUSION: The results of this study suggest that reduction of curing time significantly enhances the cytotoxicity of the studied resin cement materials, therefore compromising their clinical

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

. However, when the life-cycle costs from energy and maintenance were factored into the scenario, the LED system had lower costs at the end of a 10-year analysis period. The LED system had a 6.1 year payback compared to the 1000W PMH system and a 7.5 year payback versus the 400W PMH system. The costs reflect high initial cost for the LED luminaire, plus more luminaires and (subsequently) more poles for the LED system. The other major issue affecting cost effectiveness was that Leavenworth, Kansas has very low electricity costs. The melded rate for this site was $0.056 per kWh for electricity. However, if the national electricity rate of $0.1022/kWh was used the payback would change to between four and five years for the LED system. This demonstration met the GATEWAY requirements of saving energy, matching or improving illumination, and being cost effective. The project also demonstrated that the Commercial Building Energy Alliance (CBEA) specification works in practice. Walmart appreciated having an entire site lighted by LEDs to gain more experience with the technology. Walmart is reviewing the results of the demonstration as they consider their entire real estate portfolio.

Light-Emitting Diode-Based Illumination System for In Vitro Photodynamic Therapy

OpenAIRE

Defu Chen; Huifen Zheng; Zhiyong Huang; Huiyun Lin; Zhidong Ke; Shusen Xie; Buhong Li

2012-01-01

The aim of this study is to develop a light-emitting diode- (LED-) based illumination system that can be used as an alternative light source for in vitro photodynamic therapy (PDT). This illumination system includes a red LED array composed of 70 LEDs centered at 643 nm, an air-cooling unit, and a specific-designed case. The irradiance as a function of the irradiation distance between the LED array and the sample, the homogeneity and stability of irradiation, and the effect of long-time irrad...

Study on light and thermal energy of illumination device for plant factory design

Science.gov (United States)

Yoshida, A.; Moriuchi, K.; Ueda, Y.; Kinoshita, S.

2018-01-01

To investigate the effect of illumination devices on the yield of crops cultivated in a plant factory, it is necessary to measure the actual cultivation environmental factors related to the plant growth and understand the distribution ratio of light and thermal energy to the electrical energy injected into the illumination device. Based on cultivation results, we found that light intensity greatly affected the growth of plant weight. Regarding the selection of illumination device, its spectral components also affected the morphological change. Lighting experiments using a high frequency (Hf) fluorescent lamp and a light emitting diode (LED) bulb were performed. A certain difference was found in the distribution ratio of light energy to electrical energy between Hf and LED. It was showed that by placing the safety equipment or internal circuits outside the cultivated site, the air conditioning load could be reduced.

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.

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.

Wirelessly powered submerged-light illuminated photobioreactors for efficient microalgae cultivation

DEFF Research Database (Denmark)

Murray, Alexandra Marie; Fotidis, Ioannis; Isenschmid, Alex

2017-01-01

A novel submerged-light photobioreactor (SL-PBR) with free-floating, wireless internal light sources powered by near-field resonant inductive coupling was investigated using a quick (Chlorella vulgaris) and a slow (Haematococcus pluvialis) growing microalgal species. During testing of the SL......, respectively. Thus, the wireless internal light source was proven to be up to fivefold more effective light delivery system compared to the conventional illumination system. Meanwhile, it was discovered that some of the internal light sources had ceased to function, which might have caused underestimation...

Effect of different illumination sources on reading and visual performance

Directory of Open Access Journals (Sweden)

Male Shiva Ram

2018-01-01

Conclusion: This study demonstrates the influence of illumination on reading rate; there were no significant differences between males and females under different illuminations, however, males preferred CFL and females preferred FLUO for faster reading and visual comfort. Interestingly, neither preferred LED or TUNG. Although energy-efficient, visual performance under LED is poor; it is uncomfortable for prolonged reading and causes early symptoms of fatigue.

Extending Whole Slide Imaging: Color Darkfield Internal Reflection Illumination (DIRI for Biological Applications.

Directory of Open Access Journals (Sweden)

Yoshihiro Kawano

Full Text Available Whole slide imaging (WSI is a useful tool for multi-modal imaging, and in our work, we have often combined WSI with darkfield microscopy. However, traditional darkfield microscopy cannot use a single condenser to support high- and low-numerical-aperture objectives, which limits the modality of WSI. To overcome this limitation, we previously developed a darkfield internal reflection illumination (DIRI microscope using white light-emitting diodes (LEDs. Although the developed DIRI is useful for biological applications, substantial problems remain to be resolved. In this study, we propose a novel illumination technique called color DIRI. The use of three-color LEDs dramatically improves the capability of the system, such that color DIRI (1 enables optimization of the illumination color; (2 can be combined with an oil objective lens; (3 can produce fluorescence excitation illumination; (4 can adjust the wavelength of light to avoid cell damage or reactions; and (5 can be used as a photostimulator. These results clearly illustrate that the proposed color DIRI can significantly extend WSI modalities for biological applications.

Optical CAD Utilization for the Design and Testing of a LED Streetlamp.

Science.gov (United States)

Jafrancesco, David; Mercatelli, Luca; Fontani, Daniela; Sansoni, Paola

2017-08-24

The design and testing of LED lamps are vital steps toward broader use of LED lighting for outdoor illumination and traffic signalling. The characteristics of LED sources, in combination with the need to limit light pollution and power consumption, require a precise optical design. In particular, in every step of the process, it is important to closely compare theoretical or simulated results with measured data (obtained from a prototype). This work examines the various possibilities for using an optical CAD (Lambda Research TracePro ) to design and check a LED lamp for outdoor use. This analysis includes the simulations and testing on a prototype as an example; data acquired by measurement are inserted into the same simulation software, making it easy to compare theoretical and actual results.

Energy Savings Forecast of Solid-State Lighting in General Illumination Applications

Energy Technology Data Exchange (ETDEWEB)

none,

2014-08-29

With declining production costs and increasing technical capabilities, LED adoption has recently gained momentum in general illumination applications. This is a positive development for our energy infrastructure, as LEDs use significantly less electricity per lumen produced than many traditional lighting technologies. The U.S. Department of Energy’s Energy Savings Forecast of Solid-State Lighting in General Illumination Applications examines the expected market penetration and resulting energy savings of light-emitting diode, or LED, lamps and luminaires from today through 2030.

LED tests TTO 2010-2011. Focus on energy. Final report; LED Proeven TTO 2010-2011. Focus op energie. Eindverslag

Energy Technology Data Exchange (ETDEWEB)

Peekstok, T.; Duyvesteijn, R.; Persoon, S.; Sanders, J.; De Jong, A. [Tuinbouw Techniek Ontwikkeling TTO, Honselersdijk (Netherlands)

2011-07-15

An overview is given of research results of the application of LED in the horticulture, focusing on high-growing vegetable crops. In this report LED illuminance research for tomatoes is outlined. The project has been carried out from October 2010 to May 2011 in the demonstration nursery Westland. Also, briefly attention is paid to LED lighting tests, performed by TTO (Horticulture Technology Development) in 2008 and 2009 [Dutch] Een overzicht wordt gegeven van de onderzoeksresultaten in de toepassing van LED belichting in de glastuinbouw, met nadruk op hoogopgaande groentegewassen. In dit verslag wordt het onderzoek met LED belichting in tomaat van telersvereniging 'Tuinbouw Techniek Ontwikkeling' (TTO) uiteengezet. Dit project heeft plaatsgevonden vanaf oktober 2010 tot mei 2011 in de Demokwekerij Westland. Hiernaast worden de proeven met LED belichting, welke uitgevoerd zijn door TTO in 2008 en 2009, kort samengevat.

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.

Automatic illumination compensation device based on a photoelectrochemical biofuel cell driven by visible light

Science.gov (United States)

Yu, You; Han, Yanchao; Xu, Miao; Zhang, Lingling; Dong, Shaojun

2016-04-01

Inverted illumination compensation is important in energy-saving projects, artificial photosynthesis and some forms of agriculture, such as hydroponics. However, only a few illumination adjustments based on self-powered biodetectors that quantitatively detect the intensity of visible light have been reported. We constructed an automatic illumination compensation device based on a photoelectrochemical biofuel cell (PBFC) driven by visible light. The PBFC consisted of a glucose dehydrogenase modified bioanode and a p-type semiconductor cuprous oxide photocathode. The PBFC had a high power output of 161.4 μW cm-2 and an open circuit potential that responded rapidly to visible light. It adjusted the amount of illumination inversely irrespective of how the external illumination was changed. This rational design of utilizing PBFCs provides new insights into automatic light adjustable devices and may be of benefit to intelligent applications.Inverted illumination compensation is important in energy-saving projects, artificial photosynthesis and some forms of agriculture, such as hydroponics. However, only a few illumination adjustments based on self-powered biodetectors that quantitatively detect the intensity of visible light have been reported. We constructed an automatic illumination compensation device based on a photoelectrochemical biofuel cell (PBFC) driven by visible light. The PBFC consisted of a glucose dehydrogenase modified bioanode and a p-type semiconductor cuprous oxide photocathode. The PBFC had a high power output of 161.4 μW cm-2 and an open circuit potential that responded rapidly to visible light. It adjusted the amount of illumination inversely irrespective of how the external illumination was changed. This rational design of utilizing PBFCs provides new insights into automatic light adjustable devices and may be of benefit to intelligent applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00759g

Heat Transfer Characteristics in High Power LED Packaging

Directory of Open Access Journals (Sweden)

Chi-Hung Chung

2014-03-01

Full Text Available This study uses the T3Ster transient thermal resistance measuring device to investigate the effects to heat transfer performances from different LED crystal grains, packaging methods and heat-sink substrates through the experimental method. The experimental parameters are six different types of LED modules that are made alternatively with the crystal grain structure, the die attach method and the carrying substrate. The crystal grain structure includes the lateral type, flip chip type and vertical type. The die attach method includes silver paste and the eutectic structure. The carrying substrates are aluminum oxide (Alumina and aluminum nitride (AIN ceramic substrates and metal core PCB (MCPCB. The experimental results show that, under the conditions of the same crystal grain and die attach method, the thermal resistance values for the AIN substrate and the Alumina substrate are 2.1K/W and 5.1K/W, respectively and the total thermal resistance values are 7.3K/W and 10.8K/W. Compared to the Alumina substrate, the AIN substrate can effectively lower the total thermal resistance value by 32.4%. This is because the heat transfer coefficient of the AIN substrate is higher than that of the Alumina substrate, thus effectively increasing its thermal conductivity. In addition, under the conditions of the same crystal grain and the same substrate, the packaging methods are using silver paste and the eutectic structure for die attach. Their thermal resistance values are 5.7K/W and 2.7K/W, respectively, with a variance of 3K/W. Comparisons of the crystal grain structure show that the thermal resistance for the flip chip type is lower than that of the traditional lateral type by 0.9K/W. This is because the light emitting layer of the flip chip crystal grain is closer to the heat-sink substrate, shortening the heat dissipation route, and thus lowering the thermal resistance value. For the total thermal resistance, the crystal grain structure has a lesser

Fluorescence digital photography of acne using a light-emitting diode illuminator.

Science.gov (United States)

Ahn, Hyo Hyun; Kim, Soo Nam; Kye, Young Chul

2006-11-01

The fluorescence findings of several dermatological diseases, such as erythrasma, tinea versicolor, and acne are helpful for diagnosis and follow-up. However, many experience difficulty taking photographic images of fluorescence. The aim of this study was to develop a 405 nm light-emitting diode (LED) system for fluorescence digital photography of acne and to determine whether such a diode can be used to evaluate acne. Eight healthy acne patients were compared with controls by fluorescence digital photography using a digital camera equipped with a 405 nm LED illuminator. Digital photographs were taken by two different ways of exposure, i.e. appropriate exposure level and longer exposure. One side of the nose, cheek, and glabella was compared. The numbers and extents of fluorescence dots were counted and measured. As normal controls, seven individuals with apparent oiliness and no acne were enrolled. Red fluorescent facial dots were observed and photographed digitally using the 405 nm LED illuminator. These were more numerous and extensive on the glabella and cheeks of acne patients. Fluorescence digital photography of acne was successfully performed using a 405 nm LED illuminator. This illuminator could be used for acne evaluations.

Parallel hierarchical global illumination

Energy Technology Data Exchange (ETDEWEB)

Snell, Quinn O. [Iowa State Univ., Ames, IA (United States)

1997-10-08

Solving the global illumination problem is equivalent to determining the intensity of every wavelength of light in all directions at every point in a given scene. The complexity of the problem has led researchers to use approximation methods for solving the problem on serial computers. Rather than using an approximation method, such as backward ray tracing or radiosity, the authors have chosen to solve the Rendering Equation by direct simulation of light transport from the light sources. This paper presents an algorithm that solves the Rendering Equation to any desired accuracy, and can be run in parallel on distributed memory or shared memory computer systems with excellent scaling properties. It appears superior in both speed and physical correctness to recent published methods involving bidirectional ray tracing or hybrid treatments of diffuse and specular surfaces. Like progressive radiosity methods, it dynamically refines the geometry decomposition where required, but does so without the excessive storage requirements for ray histories. The algorithm, called Photon, produces a scene which converges to the global illumination solution. This amounts to a huge task for a 1997-vintage serial computer, but using the power of a parallel supercomputer significantly reduces the time required to generate a solution. Currently, Photon can be run on most parallel environments from a shared memory multiprocessor to a parallel supercomputer, as well as on clusters of heterogeneous workstations.

Efficient Disinfection of Tap and Surface Water with Single High Power 285 nm LED and Square Quartz Tube

Directory of Open Access Journals (Sweden)

Martin Hessling

2016-01-01

Full Text Available A small water disinfection system based on the combination of a strong single 25 mW LED with a wavelength of 285 nm and a short quartz tube with an outer rectangular cross section is presented. For the disinfection tests clear tap water and slightly turbid and yellow pond water are contaminated with high concentrations of Escherichia coli bacteria. These water samples are exposed to the germicidal 285 nm LED radiation while they flow through the quartz tube. The portion of surviving germs is determined by membrane filtration for different water qualities and flow rates. For clear tap water the bacteria concentration can be reduced by at least three orders of magnitude up to flow rates of about 20 L/h. In pond water the maximum flow rate for such a reduction is less than 3 L/h. These high disinfection capabilities and the small size of this system, allow its integration in medical systems for point of use disinfection or even its application in the Third World for decentralized water disinfection powered by small solar cells, because this disinfection capacity should be sufficient for small groups or families.

Estudo morfométrico da terapia LED de baixa potência em tendinite de ratos Morphometric study of low power LED therapy tendonitis in rats

Directory of Open Access Journals (Sweden)

José Mário Nunes da Silva

2011-12-01

Full Text Available A terapia LED de baixa potência possui efeitos analgésico e antiinflamatório. O objetivo desse estudo foi analisar a ação da terapia com LED de baixa potência na reparação tendínea por meio de histologia e histomorfometria. Foram usados 25 ratos Wistar, de 220 a 250 g, divididos em três grupos experimentais avaliados no 7º e 14º dia: A, tendinite induzida sem tratamento; B, tendinite induzida tratada com LED de baixa potência, densidade de energia 4 J/cm² por 120 segundos; e C, sem indução de tendinite. A histomorfometria mostrou-se altamente significativa (p0,05. As análises histológica e histomorfométrica demonstraram qualitativo e quantitativo aumento no número de fibroblastos aos sete dias de tratamento, e das fibras colágenas, aos 14 dias, para grupo tratado com LED de baixa potência em relação ao grupo sadio (C. O mesmo não foi percebido quando relacionado ao grupo tendinite (A14.The low power LED therapy has analgesic and anti-inflammatory effects. The objective of this study was to analyze the action of therapy with low power LED on the tendon repair, using histology and histomorphometry. Were used 25 Wistar rats, with 220 to 250 g, divided into three experimental groups (7 and 14 days: A7 and A14 induced tendonitis without treatment; B7 and B14, induced tendinitis treated with LED low power density energy 4 J /cm² for 120 seconds; and C, without induction of tendinitis. Histomorphometry was highly significant (p 0.05. Histology and histomorphometry analysis demonstrated qualitative and quantitative increase in the number of fibroblasts to seven days of treatment, and collagen fibers at 14 days for the group treated with LED low power compared to the healthy group (C. But it is unclear even when related to the tendinitis group (A14.

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...

Broadband spectrally dynamic solid state illumination source

Energy Technology Data Exchange (ETDEWEB)

Nicol, David B; Asghar, Ali; Gupta, Shalini; Kang, Hun; Pan, Ming [Georgia Institute of Technology, School of Electrical and Computer Engineering, Atlanta, GA 30332-0250 (United States); Strassburg, Martin [Georgia Institute of Technology, School of Electrical and Computer Engineering, Atlanta, GA 30332-0250 (United States); Georgia State University, Department of Physics and Astronomy, Atlanta, GA 30302-4106 (United States); Summers, Chris; Ferguson, Ian T [Georgia Institute of Technology, School of Materials Science and Engineering, Atlanta, GA 30332 (United States)

2006-06-15

Solid state lighting has done well recently in niche markets such as signage and displays, however, no available SSL technologies incorporate all the necessary attributes for general illumination. Development of a novel solid state general illumination source is discussed here. Two LEDs emitting at two distinct wavelengths can be monolithically grown and used to excite two or more phosphors with varied excitation spectra. The combined phosphorescence spectrum can then be controlled by adjusting the relative intensities of the two LED emissions. Preliminary phosphor analysis shows such a scheme to be viable for use in a spectrally dynamic broadband general illumination source. A tunnel junction is envisioned as a means of current spreading in a buried layer for three terminal operation. However, tunnel junction properties in GaN based materials are not well understood, and require further optimization to be practical devices. Preliminary results on GaN tunnel junctions are presented here as well. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Extraction of diode parameters of silicon solar cells under high illumination conditions

International Nuclear Information System (INIS)

Khan, Firoz; Baek, Seong-Ho; Park, Yiseul; Kim, Jae Hyun

2013-01-01

Graphical abstract: We have developed an analytical method to determine the diode parameters of concentrator solar cells under high illumination conditions. The determined values of diode parameters have been used to compute the theoretical values of performance parameters. The computed values of the open circuit voltage, curve factor, and efficiency obtained using diode parameters determined with this method showed good agreement (<2% discrepancy) with their experimental values in the temperature range 298–323 K. Highlights: • An analytical method to extract the diode parameters of concentrated Si solar cells. • This method uses single I–V curve under high illumination conditions. • The theoretical values of performance parameters have been computed. • Theoretical values of parameters matched within 2% discrepancy limit. • This method gives best results among the methods used in this work. - Abstract: An analytical method has been developed to extract all four diode parameters, namely the shunt resistance, series resistance, diode ideality factor, and reverse saturation current density, using a single J–V curve, based on one exponential model of silicon solar cells under high illumination conditions. The slope of the J–V curve (dV/dJ) at a short circuit condition is used to determine the value of the shunt resistance. The slope of the J–V curve at an open circuit condition together with the short circuit current density, open circuit voltage, current density, and voltage at maximum power point have been used to determine the values of the series resistance, diode ideality factor, and reverse saturation current density. The determined values of the diode parameters have been used to compute the theoretical values of the open circuit voltage, curve factor, and efficiency of the solar cell. The theoretical J–V curves matched well with the corresponding experimental curves. This method is applied to determine the diode parameters of concentrator

An extraocular non-invasive transscleral LED-endoilluminator for eye speculum integration.

Science.gov (United States)

Kölbl, Philipp Simon; Lindner, Christoph; Lingenfelder, Christian; Deuchler, Svenja; Singh, Pankaj; Koch, Frank; Hessling, Martin

2015-09-01

Conventional chandelier-endoilluminators used for pars-plana vitrectomy consist of a light-emitting tip attached to an optical fibre. The tip requires introduction into the ocular space through an incision. To achieve complete illumination of the intraocular space, the introduction of more than just one tip is sometimes necessary. An extraocular vitreoretinal LED-endoilluminator discussed in this paper represents a new approach to illuminate the intraocular space. The light source is integrated into a speculum and firmly apposed to the sclera. This approach offers the advantage of effectively illuminating the interior of the eye even though the procedure is non-invasive. Furthermore, this approach significantly reduces the risk of damage to the retina by phototoxic effects. A round white LED was used as a light source. By integrating the light source into a speculum, the LED was firmly held against the sclera. Thus, the ocular space was illuminated transsclerally. As a result, indirect uniform illumination of the complete intraocular space was achieved. The prototype was developed considering the relevant international standards. Porcine eyes were used because their properties are similar to those of human eyes. Porcine eyes could be acceptably illuminated with the selected LED. The LED-endoilluminator conforms with international standards for endoillumination. Thus, possible photochemical and thermal risks are considered and reduced to a minimum. A novel LED-endoilluminator which can be attached to a speculum was developed. The system does not need any connection to an external light source and, consequently, also avoids usage of an optical fibre. Regular and uniform illumination of the intraocular space was achieved by transmitted and scattered visible irradiation, avoiding an incision. The duration of potential light exposure, compared to existing illumination systems, can be significantly increased. This is also true when the illuminator is not directly placed

Effects of illumination on image reconstruction via Fourier ptychography

Science.gov (United States)

Cao, Xinrui; Sinzinger, Stefan

2017-12-01

The Fourier ptychographic microscopy (FPM) technique provides high-resolution images by combining a traditional imaging system, e.g. a microscope or a 4f-imaging system, with a multiplexing illumination system, e.g. an LED array and numerical image processing for enhanced image reconstruction. In order to numerically combine images that are captured under varying illumination angles, an iterative phase-retrieval algorithm is often applied. However, in practice, the performance of the FPM algorithm degrades due to the imperfections of the optical system, the image noise caused by the camera, etc. To eliminate the influence of the aberrations of the imaging system, an embedded pupil function recovery (EPRY)-FPM algorithm has been proposed [Opt. Express 22, 4960-4972 (2014)]. In this paper, we study how the performance of FPM and EPRY-FPM algorithms are affected by imperfections of the illumination system using both numerical simulations and experiments. The investigated imperfections include varying and non-uniform intensities, and wavefront aberrations. Our study shows that the aberrations of the illumination system significantly affect the performance of both FPM and EPRY-FPM algorithms. Hence, in practice, aberrations in the illumination system gain significant influence on the resulting image quality.

Optical CAD Utilization for the Design and Testing of a LED Streetlamp

Directory of Open Access Journals (Sweden)

David Jafrancesco

2017-08-01

Full Text Available The design and testing of LED lamps are vital steps toward broader use of LED lighting for outdoor illumination and traffic signalling. The characteristics of LED sources, in combination with the need to limit light pollution and power consumption, require a precise optical design. In particular, in every step of the process, it is important to closely compare theoretical or simulated results with measured data (obtained from a prototype. This work examines the various possibilities for using an optical CAD (Lambda Research TracePro to design and check a LED lamp for outdoor use. This analysis includes the simulations and testing on a prototype as an example; data acquired by measurement are inserted into the same simulation software, making it easy to compare theoretical and actual results.

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...

Comparison of two structured illumination techniques based on different 3D illumination patterns

Science.gov (United States)

Shabani, H.; Patwary, N.; Doblas, A.; Saavedra, G.; Preza, C.

2017-02-01

Manipulating the excitation pattern in optical microscopy has led to several super-resolution techniques. Among different patterns, the lateral sinusoidal excitation was used for the first demonstration of structured illumination microscopy (SIM), which provides the fastest SIM acquisition system (based on the number of raw images required) compared to the multi-spot illumination approach. Moreover, 3D patterns that include lateral and axial variations in the illumination have attracted more attention recently as they address resolution enhancement in three dimensions. A threewave (3W) interference technique based on coherent illumination has already been shown to provide super-resolution and optical sectioning in 3D-SIM. In this paper, we investigate a novel tunable technique that creates a 3D pattern from a set of multiple incoherently illuminated parallel slits that act as light sources for a Fresnel biprism. This setup is able to modulate the illumination pattern in the object space both axially and laterally with adjustable modulation frequencies. The 3D forward model for the new system is developed here to consider the effect of the axial modulation due to the 3D patterned illumination. The performance of 3D-SIM based on 3W interference and the tunable system are investigated in simulation and compared based on two different criteria. First, restored images obtained for both 3D-SIM systems using a generalized Wiener filter are compared to determine the effect of the illumination pattern on the reconstruction. Second, the effective frequency response of both systems is studied to determine the axial and lateral resolution enhancement that is obtained in each case.

An LED Approach for Measuring the Photocatalytic Breakdown of Crystal Violet Dye

Science.gov (United States)

Ryan, Robert E.; Underwood, Lauren W.; ONeal, Duane; Pagnutti, Mary; Davis, Bruce A.

2009-01-01

A simple technique to assess the reactivity of photocatalytic coatings sprayed onto transmissive glass surfaces was developed. This new method uses ultraviolet (UV) gallium nitride (GaN) light-emitting diodes (LEDs) to drive a photocatalytic reaction (the photocatalytic breakdown of a UV-resistant dye applied to a surface coated with the semiconductor titanium dioxide); and then a combination of a stabilized white light LED and a spectrometer to track the dye degradation as a function of time. Simple, standardized evaluation techniques that assess photocatalytic materials over a variety of environmental conditions, including illumination level, are not generally available and are greatly needed prior to in situ application of photocatalytic technologies. To date, much research pertaining to this aspect of photocatalysis has been limited and has focused primarily on laboratory experiments using mercury lamps. Mercury lamp illumination levels are difficult to control over large ranges and are temporally modulated by line power, limiting their use in helping to understand and predict how photocatalytic materials will behave in natural environmental settings and conditions. The methodology described here, using steady-state LEDs and time series spectroradiometric techniques, is a novel approach to explore the effect of UV light on the photocatalytic degradation of a UV resistant dye (crystal violet). GaN UV LED arrays, centered around 365 nm with an adjustable DC power supply, are used to create a small, spatially uniform light field where the steady state light level can be varied over three to four orders of magnitude. For this study, a set of glass microscope slides was custom coated with a thinly sprayed layer of photocatalytic titanium dioxide. Crystal violet was then applied to these titanium-dioxide coated slides and to uncoated control slides. The slides were then illuminated at various light levels from the dye side of the slide by the UV LED array. To monitor

The effect of LED illumination on endodontic biofilms

DEFF Research Database (Denmark)

Markvart, Merete

Within endodontics photodynamic therapy (PDT) has been suggested as a disinfectant procedure during root canal treatment. A photoactive dye (photosensitizer), methylene blue or toluidine blue, are activated by a light source, usually lasers or light emitting diodes (LEDs), thereby forming free...

Biological Effects Of Artificial Illumination

Science.gov (United States)

Corth, Richard

1980-10-01

We are increasingly being warned of the possible effects of so called "polluted" light, that is light that differs in spectral content from that of sunlight. We should be concerned, we are told, because all animals and plants have evolved under this natural daylight and therefore any difference between that illuminant and the artificial illuminants that are on the market today, is suspect. The usual presentation of the differences between the sunlight and the artificial illuminants are as shown in Figure 1. Here we are shown the spectral power distribution of sunlight and Cool White fluorescent light. The spectral power distributions of each have been normalized to some convenient wavelength so that each can be seen and easily compared on the same figure. But this presentation is misleading for one does not experience artificial illuminants at the same intensity as one experiences sunlight. Sunlight intensities are ordinarily found to be in the 8000 to 10,000 footcandle range whereas artificial illuminants are rarely experienced at intensity levels greater than 100 footcandles. Therefore a representative difference between the two types of illumination conditions is more accurately represented as in Figure 2. Thus if evolutionary adaptations require that humans and other animals be exposed to sunlight to ensure wellbeing, it is clear that one must be exposed to sunlight intensities. It is not feasible to expect that artificially illuminated environments will be lit to the same intensity as sunlight

Injection molding of high precision optics for LED applications made of liquid silicone rubber

Energy Technology Data Exchange (ETDEWEB)

Hopmann, Christian; Röbig, Malte [Institute of Plastics Processing (IKV), RWTH Aachen University, Pontstraße 49, 52062 Aachen (Germany)

2016-03-09

Light Emitting Diodes (LED) conquer the growing global market of lighting technologies. Due to their advantages, they are increasingly used in consumer products, in lighting applications in the home and in the mobility sector as well as in industrial applications. Particularly, with regard to the increasing use of high-power LED (HP-LED) the materials in the surrounding area of the light emitting semiconductor chip are of utmost importance. While the materials behind the semiconductor chip are optimized for maximum heat dissipation, the materials currently used for the encapsulation of the semiconductor chip (primary optics) and the secondary optics encounter their limits due to the high temperatures. In addition certain amounts of blue UV radiation degrade the currently used materials such as epoxy resins or polyurethanes for primary optics. In the context of an ongoing joint research project with various partners from the industry, an innovative manufacturing method for high precision optics for LED applications made of liquid silicone rubber (LSR) is analyzed at the Institut of Plastics Processing (IKV), Aachen. The aim of this project is to utilize the material-specific advantages of high transparent LSR, especially the excellent high temperature resistance and the great freedom in design. Therefore, a high integrated injection molding process is developed. For the production of combined LED primary and secondary optics a LED board is placed in an injection mold and overmolded with LSR. Due to the integrated process and the reduction of subcomponents like the secondary optics the economics of the production process can be improved significantly. Furthermore combined LED optics offer an improved effectiveness, because there are no losses of the light power at the transition of the primary and secondary optics.

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.

Improving the Effectiveness of a Nutrient Removal System Composed of Microalgae and Daphnia by an Artificial Illumination

Directory of Open Access Journals (Sweden)

In-Ho Chang

2014-03-01

Full Text Available For determining the effect of illumination on nutrient removal in an artificial food web (AFW system, we launched a pilot continuous-flow system. The system consisted of a storage basin, a phytoplankton growth chamber, and a zooplankton growth chamber. A 25,000 Lux AFW-light emitting diode (LED on system and an AFW-LED off system were separately operated for 10 days. In the AFW-LED on system, the maximum chlorophyll-a concentration of the phytoplankton chamber was four times higher than that of the AFW-LED off system. With artificial nighttime illumination, the microalgae became both smaller and more nutritious; the microalgae became high quality food for the zooplankton, Daphnia magna. Consequently, this zooplankton became more efficient at extracting nutrients and grew more densely than in the AFW-LED off system condition. In the LED-on condition, the amounts of total nitrogen (TN and total phosphorus (TP flowing into the system for 10 days were 84.7 g and 20.4 g, and the amounts flowing out were 19.5 g (23% and 4.0 g (20%, respectively. In contrast, in the LED-off condition, 83.8 g and 20.6 g of TN and TP flowed into the system while 38.8 g (46% and 6.8 g (33% flowed out, respectively. Artificial illumination significantly improves the removal rate of nutrients in an AFW system.

[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.

Non-Destructive Quality Evaluation of Pepper (Capsicum annuum L. Seeds Using LED-Induced Hyperspectral Reflectance Imaging

Directory of Open Access Journals (Sweden)

Changyeun Mo

2014-04-01

Full Text Available In this study, we developed a viability evaluation method for pepper (Capsicum annuum L. seeds based on hyperspectral reflectance imaging. The reflectance spectra of pepper seeds in the 400–700 nm range are collected from hyperspectral reflectance images obtained using blue, green, and red LED illumination. A partial least squares–discriminant analysis (PLS-DA model is developed to classify viable and non-viable seeds. Four spectral ranges generated with four types of LEDs (blue, green, red, and RGB, which were pretreated using various methods, are investigated to develop the classification models. The optimal PLS-DA model based on the standard normal variate for RGB LED illumination (400–700 nm yields discrimination accuracies of 96.7% and 99.4% for viable seeds and nonviable seeds, respectively. The use of images based on the PLS-DA model with the first-order derivative of a 31.5-nm gap for red LED illumination (600–700 nm yields 100% discrimination accuracy for both viable and nonviable seeds. The results indicate that a hyperspectral imaging technique based on LED light can be potentially applied to high-quality pepper seed sorting.

On the illumination of neutron star accretion discs

Science.gov (United States)

Wilkins, D. R.

2018-03-01

The illumination of the accretion disc in a neutron star X-ray binary by X-rays emitted from (or close to) the neutron star surface is explored through general relativistic ray tracing simulations. The applicability of the canonical suite of relativistically broadened emission line models (developed for black holes) to discs around neutron stars is evaluated. These models were found to describe well emission lines from neutron star accretion discs unless the neutron star radius is larger than the innermost stable orbit of the accretion disc at 6 rg or the disc is viewed at high inclination, above 60° where shadowing of the back side of the disc becomes important. Theoretical emissivity profiles were computed for accretion discs illuminated by hotspots on the neutron star surfaces, bands of emission and emission by the entirety of the hot, spherical star surface and in all cases, the emissivity profile of the accretion disc was found to be well represented by a single power law falling off slightly steeper than r-3. Steepening of the emissivity index was found where the emission is close to the disc plane and the disc can appear truncated when illuminated by a hotspot at high latitude. The emissivity profile of the accretion disc in Serpens X-1 was measured and found to be consistent with a single unbroken power law with index q=3.5_{-0.4}^{+0.3}, suggestive of illumination by the boundary layer between the disc and neutron star surface.

High-speed photoacoustic imaging using an LED-based photoacoustic imaging system

Science.gov (United States)

Sato, Naoto; Kuniyil Ajith Singh, Mithun; Shigeta, Yusuke; Hanaoka, Takamitsu; Agano, Toshitaka

2018-02-01

Recently we developed a multispectral LED-based photoacoustic/ultrasound imaging system (AcousticX) and have been continuously working on its technical/functional improvements. AcousticX is a linear array ultrasound transducer (128 elements, 10 MHz)-based system in which LED arrays (selectable wavelengths, pulse repetition frequency: 4 kHz, pulse width: tunable from 40 - 100 ns) are fixed on both sides of the transducer to illuminate the tissue for photoacoustic imaging. The ultrasound/photoacoustic data from all 128 elements can be simultaneously acquired, processed and displayed. We already demonstrated our system's capability to perform photoacoustic/ultrasound imaging for dynamic imaging of the tissue at a frame rate of 10 Hz (for example to visualize the pulsation of arteries in vivo in human subjects). In this work, we present the development of a new high-speed imaging mode in AcousticX. In this mode, instead of toggling between ultrasound and photoacoustic measurements, it is possible to continuously acquire only photoacoustic data for 1.5 seconds with a time interval of 1 ms. With this improvement, we can record photoacoustic signals from the whole aperture (38 mm) at fast rate and can be reviewed later at different speeds for analyzing dynamic changes in the photoacoustic signals. We believe that AcousticX with this new high-speed mode opens up a feasible technical path for multiple dynamic studies, for example one which focus on imaging the response of voltage sensitive dyes. We envisage to improve the acquisition speed further in future for exploring ultra-high-speed applications.

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.

Pulsed laser illumination of photovoltaic cells

Science.gov (United States)

Yater, Jane A.; Lowe, Roland A.; Jenkins, Phillip P.; Landis, Geoffrey A.

1995-01-01

In future space missions, free electron lasers (FEL) may be used to illuminate photovoltaic receivers to provide remote power. Both the radio-frequency (RF) and induction FEL produce pulsed rather than continuous output. In this work we investigate cell response to pulsed laser light which simulates the RF FEL format. The results indicate that if the pulse repetition is high, cell efficiencies are only slightly reduced compared to constant illumination at the same wavelength. The frequency response of the cells is weak, with both voltage and current outputs essentially dc in nature. Comparison with previous experiments indicates that the RF FEL pulse format yields more efficient photovoltaic conversion than does an induction FEL format.

High power deep UV-LEDs for analytical optical instrumentation

Czech Academy of Sciences Publication Activity Database

Li, Y.; Dvořák, Miloš; Nesterenko, P. N.; Nuchtavorn, N.; Macka, M.

2018-01-01

Roč. 255, č. 2 (2018), s. 1238-1243 ISSN 0925-4005 Institutional support: RVO:68081715 Keywords : deep UV Light emitting diodes (LEDs) * optical detection * portable analytical instrumentation Subject RIV: CB - Analytical Chemistry, Separation OBOR OECD: Analytical chemistry Impact factor: 5.401, year: 2016

High Efficiency, Illumination Quality OLEDs for Lighting

Energy Technology Data Exchange (ETDEWEB)

Joseph Shiang; James Cella; Kelly Chichak; Anil Duggal; Kevin Janora; Chris Heller; Gautam Parthasarathy; Jeffery Youmans; Joseph Shiang

2008-03-31

The goal of the program was to demonstrate a 45 lumen per watt white light device based upon the use of multiple emission colors through the use of solution processing. This performance level is a dramatic extension of the team's previous 15 LPW large area illumination device. The fundamental material system was based upon commercial polymer materials. The team was largely able to achieve these goals, and was able to deliver to DOE a 90 lumen illumination source that had an average performance of 34 LPW a 1000 cd/m{sup 2} with peak performances near 40LPW. The average color temperature is 3200K and the calculated CRI 85. The device operated at a brightness of approximately 1000cd/m{sup 2}. The use of multiple emission colors particularly red and blue, provided additional degrees of design flexibility in achieving white light, but also required the use of a multilayered structure to separate the different recombination zones and prevent interconversion of blue emission to red emission. The use of commercial materials had the advantage that improvements by the chemical manufacturers in charge transport efficiency, operating life and material purity could be rapidly incorporated without the expenditure of additional effort. The program was designed to take maximum advantage of the known characteristics of these material and proceeded in seven steps. (1) Identify the most promising materials, (2) assemble them into multi-layer structures to control excitation and transport within the OLED, (3) identify materials development needs that would optimize performance within multilayer structures, (4) build a prototype that demonstrates the potential entitlement of the novel multilayer OLED architecture (5) integrate all of the developments to find the single best materials set to implement the novel multilayer architecture, (6) further optimize the best materials set, (7) make a large area high illumination quality white OLED. A photo of the final deliverable is shown

Design of a high-efficiency train headlamp with low power consumption using dual half-parabolic aluminized reflectors.

Science.gov (United States)

Liang, Wei-Lun; Su, Guo-Dung J

2018-02-20

We propose a train headlamp system using dual half-circular parabolic aluminized reflectors. Each half-circular reflector contains five high-efficiency and small-package light-emitting diode (LED) chips, and the halves are 180° rotationally symmetric. For traffic safety, the headlamp satisfies the Code of Federal Regulations. To predict the pattern of illumination, an analytical derivation is developed for the optical path of a ray that is perpendicular to and emitted from the center of an LED chip. This ray represents the main ray emitted from the LED chip and is located at the maximum illuminance of the spot projected by the LED source onto a screen. We then analyze the design systematically to determine the locations of the LED chips in the reflector that minimize electricity consumption while satisfying reliability constraints associated with traffic safety. Compared to a typical train headlamp system with an incandescent or halogen lamp needing several hundred watts, the proposed system only uses 20.18 W to achieve the luminous intensity requirements.

Utilization of multi-band OFDM modulation to increase traffic rate of phosphor-LED wireless VLC.

Science.gov (United States)

Yeh, Chien-Hung; Chen, Hsing-Yu; Chow, Chi-Wai; Liu, Yen-Liang

2015-01-26

To increase the traffic rate in phosphor-LED visible light communication (VLC), a multi-band orthogonal frequency division multiplexed (OFDM) modulation is first proposed and demonstrated. In the measurement, we do not utilize optical blue filter to increase modulation bandwidth of phosphor-LED in the VLC system. In this proposed scheme, different bands of OFDM signals are applied to different LED chips in a LED lamp, this can avoid the power fading and nonlinearity issue by applying the same OFDM signal to all the LED chips in a LED lamp. Here, the maximum increase percentages of traffic rates are 41.1%, 17.8% and 17.8% under received illuminations of 200, 500 and 1000 Lux, respectively, when the proposed three-band OFDM modulation is used in the VLC system. In addition, the analysis and verification by experiments are also performed.

The Photodynamic Effect of LED-Magnetic Exposure to Photoinactivation of Aerobic Photosyntetic Bacteria

OpenAIRE

Astuti, Suryani Dyah

2015-01-01

All photosynthetic bacteria have a major pigment of bacteriochlorophyl and accessor pigment e.g. the carotenoids, which both have an important role in photosynthesis process. This study aim to explore the exogenous organic photosensitizer from photosyntetic bacteria for photodynamic therapy application. This study is an experimental research aiming to test the potential illumination of LED with wavelength 409, 430, 528 and 629 nm, and power optimization and time exposure LED-magnetic for opti...

Noise tolerant illumination optimization applied to display devices

Science.gov (United States)

Cassarly, William J.; Irving, Bruce

2005-02-01

Display devices have historically been designed through an iterative process using numerous hardware prototypes. This process is effective but the number of iterations is limited by the time and cost to make the prototypes. In recent years, virtual prototyping using illumination software modeling tools has replaced many of the hardware prototypes. Typically, the designer specifies the design parameters, builds the software model, predicts the performance using a Monte Carlo simulation, and uses the performance results to repeat this process until an acceptable design is obtained. What is highly desired, and now possible, is to use illumination optimization to automate the design process. Illumination optimization provides the ability to explore a wider range of design options while also providing improved performance. Since Monte Carlo simulations are often used to calculate the system performance but those predictions have statistical uncertainty, the use of noise tolerant optimization algorithms is important. The use of noise tolerant illumination optimization is demonstrated by considering display device designs that extract light using 2D paint patterns as well as 3D textured surfaces. A hybrid optimization approach that combines a mesh feedback optimization with a classical optimizer is demonstrated. Displays with LED sources and cold cathode fluorescent lamps are considered.

Optimal colour quality of LED clusters based on memory colours.

Science.gov (United States)

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

2011-03-28

The spectral power distributions of tri- and tetrachromatic clusters of Light-Emitting-Diodes, composed of simulated and commercially available LEDs, were optimized with a genetic algorithm to maximize the luminous efficacy of radiation and the colour quality as assessed by the memory colour quality metric developed by the authors. The trade-off of the colour quality as assessed by the memory colour metric and the luminous efficacy of radiation was investigated by calculating the Pareto optimal front using the NSGA-II genetic algorithm. Optimal peak wavelengths and spectral widths of the LEDs were derived, and over half of them were found to be close to Thornton's prime colours. The Pareto optimal fronts of real LED clusters were always found to be smaller than those of the simulated clusters. The effect of binning on designing a real LED cluster was investigated and was found to be quite large. Finally, a real LED cluster of commercially available AlGaInP, InGaN and phosphor white LEDs was optimized to obtain a higher score on memory colour quality scale than its corresponding CIE reference illuminant.

Influence of dome phosphor particle concentration on mid-power LED thermal resistance

NARCIS (Netherlands)

Alexeev, A.; Martin, G.; Hildenbrand, V.D.; Bosschaart, K.J.

2016-01-01

The modern white mid-power LEDs usually contain phosphor particles encapsulated in silicone dome material. The particles convert the blue light emitted from the epitaxial layer and play significant role in thermal processes of LED packages. In this paper the influence of the phosphor particles

Natural light illumination system.

Science.gov (United States)

Whang, Allen Jong-Woei; Chen, Yi-Yung; Yang, Shu-Hua; Pan, Po-Hsuan; Chou, Kao-Hsu; Lee, Yu-Chi; Lee, Zong-Yi; Chen, Chi-An; Chen, Cheng-Nan

2010-12-10

In recent years, green energy has undergone a lot of development and has been the subject of many applications. Many research studies have focused on illumination with sunlight as a means of saving energy and creating healthy lighting. Natural light illumination systems have collecting, transmitting, and lighting elements. Today, most daylight collectors use dynamic concentrators; these include Sun tracking systems. However, this design is too expensive to be cost effective. To create a low-cost collector that can be easily installed on a large building, we have designed a static concentrator, which is prismatic and cascadable, to collect sunlight for indoor illumination. The transmission component uses a large number of optical fibers. Because optical fibers are expensive, this means that most of the cost for the system will be related to transmission. In this paper, we also use a prismatic structure to design an optical coupler for coupling n to 1. With the n-to-1 coupler, the number of optical fibers necessary can be greatly reduced. Although this new natural light illumination system can effectively guide collected sunlight and send it to the basement or to other indoor places for healthy lighting, previously there has been no way to manage the collected sunlight when lighting was not desired. To solve this problem, we have designed an optical switch and a beam splitter to control and separate the transmitted light. When replacing traditional sources, the lighting should have similar characteristics, such as intensity distribution and geometric parameters, to those of traditional artificial sources. We have designed, simulated, and optimized an illumination lightpipe with a dot pattern to redistribute the collected sunlight from the natural light illumination system such that it equals the qualities of a traditional lighting system. We also provide an active lighting module that provides lighting from the natural light illumination system or LED auxiliary

Side- and end-illumination of polymer optical fibers in the UV region

Science.gov (United States)

Eckhardt, Hanns-S.; Jungling, B.; Klein, Karl-Friedrich; Poisel, Hans

2003-07-01

Since more than 2 decades, the polymer optical fiber (POF) based on PMMA is well known. A lot of applications were studied and initiated: in addition to data transmission, the automotive, lighting and sensor applications are of main interest. Due to the spectral attenuation and applications, light-sources like broadband metal-halide lamps and halogen lamps, or LEDs and laser-diodes are mainly used. Due to improvement in manufacturing of the standard step-index POF, the variations of the spectral attenuation in the blue region have been reduced. Therefore, the losses are acceptable for short-length applications in the UV-A region. Using different light-sources like high-power Xenon-lamp, deuterium-lamp or UV-LEDs, the UV-damage is an important factor. In addition to the basic attenuation, the UV-induced losses will be determined by experiment, in the interesting UV-A region. The higher flexibilty of the thick-core POF is superior in comparison to silica or glass fibers with the same outer diameter. Therefore, the bending losses in the UV-region are important, too. For special applications in the medical field, side-illuminating fibers are highly accepted. The axial and spectral dependence on the lateral radiation pattern will be described, using a very thick fiber.

High speed low power optical detection of sub-wavelength scatterer

NARCIS (Netherlands)

Roy, S.; Bouwens, M.A.J.; Wei, L.; Pereira, S.F.; Urbach, H.P.; Walle, P. van der

2015-01-01

Optical detection of scatterers on a flat substrate, generally done using dark field microscopy technique, is challenging since it requires high power illumination to obtain sufficient SNR (Signal to Noise Ratio) to be able to detect sub-wavelength particles. We developed a bright field technique,

High power VCSELs for miniature optical sensors

Science.gov (United States)

Geske, Jon; Wang, Chad; MacDougal, Michael; Stahl, Ron; Follman, David; Garrett, Henry; Meyrath, Todd; Snyder, Don; Golden, Eric; Wagener, Jeff; Foley, Jason

2010-02-01

Recent advances in Vertical-cavity Surface-emitting Laser (VCSEL) efficiency and packaging have opened up alternative applications for VCSELs that leverage their inherent advantages over light emitting diodes and edge-emitting lasers (EELs), such as low-divergence symmetric emission, wavelength stability, and inherent 2-D array fabrication. Improvements in reproducible highly efficient VCSELs have allowed VCSELs to be considered for high power and high brightness applications. In this talk, Aerius will discuss recent advances with Aerius' VCSELs and application of these VCSELs to miniature optical sensors such as rangefinders and illuminators.

Multiple Primary LED Lamp Colour Controller with Inherent Brightness Limitation

NARCIS (Netherlands)

Barcena, R.; Ackermann, B.

2007-01-01

There is a strong interest in using LEDs for general illumination due to the potential they offer for energy saving, environmental friendliness, new opportunities in lighting design, and control of the intensity, colour, and spatial distribution of light. General illumination requires primarily

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

High to ultra-high power electrical energy storage.

Science.gov (United States)

Sherrill, Stefanie A; Banerjee, Parag; Rubloff, Gary W; Lee, Sang Bok

2011-12-14

High power electrical energy storage systems are becoming critical devices for advanced energy storage technology. This is true in part due to their high rate capabilities and moderate energy densities which allow them to capture power efficiently from evanescent, renewable energy sources. High power systems include both electrochemical capacitors and electrostatic capacitors. These devices have fast charging and discharging rates, supplying energy within seconds or less. Recent research has focused on increasing power and energy density of the devices using advanced materials and novel architectural design. An increase in understanding of structure-property relationships in nanomaterials and interfaces and the ability to control nanostructures precisely has led to an immense improvement in the performance characteristics of these devices. In this review, we discuss the recent advances for both electrochemical and electrostatic capacitors as high power electrical energy storage systems, and propose directions and challenges for the future. We asses the opportunities in nanostructure-based high power electrical energy storage devices and include electrochemical and electrostatic capacitors for their potential to open the door to a new regime of power energy.

Controlled structures in laterally patterned barrier discharges by illumination of the semiconductor electrode

International Nuclear Information System (INIS)

Wild, R; Schumann, T; Stollenwerk, L

2014-01-01

In this contribution, we present a possibility to actively control emerging patterns in laterally extended barrier discharges. One of the barriers is a high-ohmic semiconductive GaAs electrode. As the electrode is illuminated from its plasma-far side, the voltage inside the plasma gap is increased. If the gap voltage becomes higher than the ignition voltage of the gas, a discharge is started. A corresponding electrical model is given. The lateral resolution of control for a laterally homogeneous discharge is investigated. It is found that the luminescence of the discharge is controlled by both a variation of illumination power density and a variation of the applied voltage. However, during an increase in the applied voltage, the discharge may become larger than the area of illumination. Further, an investigation of the patterned discharge control shows that the number of current spots depends on the illumination power density and the area of illumination. The behaviour of current spot appearance suggests an inhibitory influence, preventing a discharge in its immediate surrounding and limiting the total number of current spots. (paper)

High performance 1.3 μm buried crescent lasers and LEDs for fiber optic links

International Nuclear Information System (INIS)

Fu, R.J.; Chan, E.Y.; Hong, C.S.

1989-01-01

Self-aligned buried crescent heterostructure (BCH) semiconductor lasers and LEDs have been successfully developed as superb light sources for fiber optic communications. The fabrication and performance characteristics of these InGaAsP/InP lasers and LEDs are described. For lasers, the threshold currents as low as 10 mA and differential quantum efficiencies as high as 50% are achieved. For LEDs, the output powers at 150 mA are higher than 1 mW. Good far field patterns are obtained in both the LEDs and lasers. Measured I-V, L-I, spectrum and far field patterns are presented

Optical design of high power excimer laser system

International Nuclear Information System (INIS)

Zhang Yongsheng; Zhao Jun; Ma Lianying; Yi Aiping; Liu Jingru

2011-01-01

Image relay and angular multiplexing,which should be considered together in the design of high power excimer laser system, is reviewed. It's important to select proper illumination setup and laser beam shaping techniques. Given the complex and special angular multiplexing scheme in high power excimer laser systems, some detailed conceptual layout schemes are given in the paper. After a brief description of lens array and reflective telescope objective, which combine the incoming beams to a common focus, a new schematic layout which uses the final targeting optics and one optical delay line array, to realize multiplexing and de-multiplexing simultaneously is first proposed in the paper. (authors)

Improved Performances of a Fluidized Bed Photo reactor by a Microscale Illumination System

International Nuclear Information System (INIS)

Ciambelli, P.; Sannino, D.; Palma, V.; Vaiano, V.; Mazzei, R.S.; Ciambelli, P.; Sannino, D.

2009-01-01

The performances of a gas-solid two-dimensional fluidized bed reactor in photo catalytic selective oxidation reactions, irradiated with traditional UV lamps or with a microscale illumination system based on UV emitting diodes (UV A-LEDs), have been compared. In the photo catalytic oxidative dehydrogenation of cyclohexane to benzene on MoOx/TiO 2 -A1 2 O 3 catalyst the use of UV A-LEDs modules allowed to achieve a cyclohexane conversion and benzene yield higher than those obtained with traditional UV lamps. The better performances with UV A-LEDs are due to the UV A-LEDs small dimensions and small-angle emittance, which allow photons beam be directed towards the photo reactor windows, reducing the dispersion outside of photo reactor or the optical path length. As a consequence, the effectively illuminated mass of catalyst is greater. We have found that this illumination system is efficient for photo-oxidative dehydrogenation of cyclohexane to cyclohexene on sulphated MoOx-A1 2 O 3 and ethanol to acetaldehyde on VOx/TiO 2 .

SPECIFIC FEATURES OF POWER CONSUMPTION OF LED DEVICES AND ACCOUNTING THEM IN CALCULATION OF ELECTRICAL NETWORKS

Directory of Open Access Journals (Sweden)

V. N. Radkevich

2016-01-01

Full Text Available The indicators of power consumption of lighting devices based on LEDs are studied depending on the supplied voltage. For the lamp and floodlight with LEDs active and reactive power, current and power factor as a function of voltage (which value changed in the range 200–245 V were experimentally determined. The analysis of experimental data demonstrated that due to the drivers in the specified voltage range the active power consumed by light devices remains practically unchanged. The reactive power of LED devices depends on the supplied voltage and is capacitive in its nature. In contrast with gas-discharge light sources the LED devices under study do not consume reactive power, but generate it. With the change of the supplied voltage from 200 to 245 V the value of the generated reactive power increases to 60 % for the floodlight and 50 % for the lamp. The LED floodlight has a low coefficient of active power. The current consumed by the floodlight has increased by 22 %, and by the lamp – by 13 %. The formulas for determining the maximum value of the length of the calculated section of single-phase group lines were developed, taking into account specific source data. LED light sources tend to feed by electric power by single-phase group lines. The number of lamps connected to single-phase lines is regulated by normative documents. Bearing this in mind as well as the small power of LED sources single-phase group lines are usually performed with conductors of the smallest possible cross section. The limit values of the length of the calculated section that correspond to a predetermined loss of voltage in line with ambient temperature from 15 to 60 °С were determined for them. The calculations demonstrated that for group lines that feed the LEDs, the choice of conductor cross-sections in accordance with permissible voltage loss is not critical. The determinant factor for the choice of the cross-section of the conductors of group electrical

High-Power 365 nm UV LED Mercury Arc Lamp Replacement for Photochemistry and Chemical Photolithography

OpenAIRE

H?lz, K.; Lietard, J.; Somoza, M. M.

2016-01-01

Ultraviolet light emitting diodes (UV LEDs) have become widespread in chemical research as highly efficient light sources for photochemistry and photopolymerization. However, in more complex experimental setups requiring highly concentrated light and highly spatially resolved patterning of the light, high-pressure mercury arc lamps are still widely used because they emit intense UV light from a compact arc volume that can be efficiently coupled into optical systems. Advances in the deposition...

Illumination Sufficiency Survey Techniques: In-situ Measurements of Lighting System Performance and a User Preference Survey for Illuminance in an Off-Grid, African Setting

Energy Technology Data Exchange (ETDEWEB)

Alstone, Peter; Jacobson, Arne; Mills, Evan

2010-08-26

Efforts to promote rechargeable electric lighting as a replacement for fuel-based light sources in developing countries are typically predicated on the notion that lighting service levels can be maintained or improved while reducing the costs and environmental impacts of existing practices. However, the extremely low incomes of those who depend on fuel-based lighting create a need to balance the hypothetically possible or desirable levels of light with those that are sufficient and affordable. In a pilot study of four night vendors in Kenya, we document a field technique we developed to simultaneously measure the effectiveness of lighting service provided by a lighting system and conduct a survey of lighting service demand by end-users. We took gridded illuminance measurements across each vendor's working and selling area, with users indicating the sufficiency of light at each point. User light sources included a mix of kerosene-fueled hurricane lanterns, pressure lamps, and LED lanterns.We observed illuminance levels ranging from just above zero to 150 lux. The LED systems markedly improved the lighting service levels over those provided by kerosene-fueled hurricane lanterns. Users reported that the minimum acceptable threshold was about 2 lux. The results also indicated that the LED lamps in use by the subjects did not always provide sufficient illumination over the desired retail areas. Our sample size is much too small, however, to reach any conclusions about requirements in the broader population. Given the small number of subjects and very specific type of user, our results should be regarded as indicative rather than conclusive. We recommend replicating the method at larger scales and across a variety of user types and contexts. Policymakers should revisit the subject of recommended illuminance levels regularly as LED technology advances and the price/service balance point evolves.

Evolution of Very High Frequency Power Supplies

DEFF Research Database (Denmark)

Knott, Arnold; Andersen, Toke Meyer; Kamby, Peter

2013-01-01

The ongoing demand for smaller and lighter power supplies is driving the motivation to increase the switching frequencies of power converters. Drastic increases however come along with new challenges, namely the increase of switching losses in all components. The application of power circuits used...... in radio frequency transmission equipment helps to overcome those. However those circuits were not designed to meet the same requirements as power converters. This paper summarizes the contributions in recent years in application of very high frequency (VHF) technologies in power electronics, shows results...... of the recent advances and describes the remaining challenges. The presented results include a self-oscillating gate-drive, air core inductor optimizations, an offline LED driver with a power density of 8.9 W/cm3 and a 120 MHz, 9 W DC powered LED driver with 89 % efficiency as well as a bidirectional VHF...

Éalonnage de sources lumineuses de type LED

DEFF Research Database (Denmark)

Durix, Bastien; Quéau, Yvain; Lucas, Tom

We describe three calibration methods of a LED (light-emitting diode), in order to apply photometric stereo to a scene illuminated by LEDs. The most accurate of these methods will allow us to obtain very realistic 3D models. Nevertheless, the scene must remain still during the whole shooting sequ...

Electrical efficiency and droop in MQW LEDs

Science.gov (United States)

Malyutenko, V. K.

2014-02-01

It is believed that low power conversion efficiency in commercial MQW LEDs occurs as a result of efficiency droop, current-induced dynamic degradation of the internal quantum efficiency, injection efficiency, and extraction efficiency. Broadly speaking, all these "quenching" mechanisms could be referred to as the optical losses. The vast advances of high-power InGaN and AlGaInP MQW LEDs have been achieved by addressing these losses. In contrast to these studies, in this paper we consider an alternative approach to make high-power LEDs more efficient. We identify current-induced electrical efficiency degradation (EED) as a strong limiting factor of power conversion efficiency. We found that EED is caused by current crowding followed by an increase in current-induced series resistance of a device. By decreasing the current spreading length, EED also causes the optical efficiency to degrade and stands for an important aspect of LED performance. This paper gives scientists the opportunity to look for different attributes of EED.

Preliminary investigations of piezoelectric based LED luminary

DEFF Research Database (Denmark)

Nielsen, Dennis; Andersen, Michael A. E.; Meyer, Kaspar Sinding

2011-01-01

, modulation schemes, LEDs and LED driving conditions are analyzed. A prototype radial mode PT optimized for ZVS (Zero Voltage Switching) is designed. FEM (Final Element Method) and measurements validates the PT design. A prototype PT based AC/DC converter operating from european mains is proposed......This paper presents a preliminary study of PT (Piezoelectric Transformer) based SMPS’s (Switch Mode Power Supplies) for LED luminary. The unique properties of PTs (efficiency, power density and EMI) make them highly suitable for this application. Power stage topologies, rectifiers circuits...

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

Spacing optimization of high power LED arrays for solid state lighting

Energy Technology Data Exchange (ETDEWEB)

Chan, Y. Sing; Lee, S. W. Ricky, E-mail: rickylee@ust.hk [Electronic Packaging Laboratory, Center for Advanced Microsystems Packaging, Hong Kong University of Science and Technology (Hong Kong)

2011-01-15

This paper provides an analytical approach to determine the optimum pitch by utilizing a thermal resistance network, under the assumption of constant luminous efficiency. This work allows an LED array design which is mounted on a printed circuit board (PCB) attached with a heat sink subject to the natural convection cooling. Being validated by finite element (FE) models, the current approach can be shown as an effective method for the determination of optimal component spacing in an LED array assembly for SSL. (semiconductor devices)

High energy, high average power solid state green or UV laser

Science.gov (United States)

Hackel, Lloyd A.; Norton, Mary; Dane, C. Brent

2004-03-02

A system for producing a green or UV output beam for illuminating a large area with relatively high beam fluence. A Nd:glass laser produces a near-infrared output by means of an oscillator that generates a high quality but low power output and then multi-pass through and amplification in a zig-zag slab amplifier and wavefront correction in a phase conjugator at the midway point of the multi-pass amplification. The green or UV output is generated by means of conversion crystals that follow final propagation through the zig-zag slab amplifier.

Generation of solar spectrum by using LEDs

Science.gov (United States)

Lu, Pengzhi; Yang, Hua; Pei, Yanrong; Li, Jing; Xue, Bin; Wang, Junxi; Li, Jinmin

2016-09-01

Light emitting diode (LED) has been recognized as an applicable light source for indoor and outdoor lighting, city beautifying, landscape facilities, and municipal engineering etc. Conventional LED has superior characteristics such as long life time, low power consumption, high contrast, and wide viewing angle. Recently, LED with high color-rendering index and special spectral characteristics has received more and more attention. This paper is intended to report a solar spectrum simulated by multichip LED light source. The typical solar spectrum of 5500k released by CIE was simulated as a reference. Four types of LEDs with different spectral power distributions would be used in the LED light source, which included a 430nm LED, a 480nm LED, a 500nm LED and a white LED. In order to obtain better simulation results, the white LED was achieved by a 450nm LED chip with the mixture of phosphor. The phosphor combination was prepared by mixing green phosphor, yellow phosphor and red phosphor in a certain proportion. The multichip LED light source could provide a high fidelity spectral match with the typical solar spectrum of 5500k by adjusting injection current to each device. The luminous flux, CIE chromaticity coordinate x, y, CCT, and Ra were 104.7 lm, 0.3337, 0.3681, 5460K, and 88.6, respectively. Because of high color-rendering index and highly match to the solar spectrum, the multichip LED light source is a competitive candidate for applications where special spectral is required, such as colorimetric measurements, visual inspection, gemstone identification and agriculture.

Advances in LEDs for automotive applications

Science.gov (United States)

Bhardwaj, Jy; Peddada, Rao; Spinger, Benno

2016-03-01

High power LEDs were introduced in automotive headlights in 2006-2007, for example as full LED headlights in the Audi R8 or low beam in Lexus. Since then, LED headlighting has become established in premium and volume automotive segments and beginning to enable new compact form factors such as distributed low beam and new functions such as adaptive driving beam. New generations of highly versatile high power LEDs are emerging to meet these application needs. In this paper, we will detail ongoing advances in LED technology that enable revolutionary styling, performance and adaptive control in automotive headlights. As the standards which govern the necessary lumens on the road are well established, increasing luminance enables not only more design freedom but also headlight cost reduction with space and weight saving through more compact optics. Adaptive headlighting is based on LED pixelation and requires high contrast, high luminance, smaller LEDs with high-packing density for pixelated Matrix Lighting sources. Matrix applications require an extremely tight tolerance on not only the X, Y placement accuracy, but also on the Z height of the LEDs given the precision optics used to image the LEDs onto the road. A new generation of chip scale packaged (CSP) LEDs based on Wafer Level Packaging (WLP) have been developed to meet these needs, offering a form factor less than 20% increase over the LED emitter surface footprint. These miniature LEDs are surface mount devices compatible with automated tools for L2 board direct attach (without the need for an interposer or L1 substrate), meeting the high position accuracy as well as the optical and thermal performance. To illustrate the versatility of the CSP LEDs, we will show the results of, firstly, a reflector-based distributed low beam using multiple individual cavities each with only 20mm height and secondly 3x4 to 3x28 Matrix arrays for adaptive full beam. Also a few key trends in rear lighting and impact on LED light

Die attach dimension and material on thermal conductivity study for high power COB LED

Science.gov (United States)

Sarukunaselan, K.; Ong, N. R.; Sauli, Z.; Mahmed, N.; Kirtsaeng, S.; Sakuntasathien, S.; Suppiah, S.; Alcain, J. B.; Retnasamy, V.

2017-09-01

High power LED began to gain popularity in the semiconductor market due to its efficiency and luminance. Nonetheless, along with the increased in efficiency, there was an increased in the junction temperature too. The alleviating junction temperature is undesirable since the performances and lifetime will be degraded over time. Therefore, it is crucial to solve this thermal problem by maximizing the heat dissipation to the ambience. Improvising the die attach (DA) layer would be the best option because this layer is sandwiched between the chip (heat source) and the substrate (channel to the ambient). In this paper, the impact of thickness and thermal conductivity onto the junction temperature and Von Mises stress is analyzed. Results obtained showed that the junction temperature is directly proportional to the thickness but the stress was inversely proportional to the thickness of the DA. The thermal conductivity of the materials did affect the junction temperature as there was not much changes once the thermal conductivity reached 20W/mK. However, no significant changes were observed on the Von Mises stress caused by the thermal conductivity. Material with the second highest thermal conductivity had the lowest stress, whereas the highest conductivity material had the highest stress value at 20 µm. Overall, silver sinter provided the best thermal dissipation compared to the other materials.

LED--panacea or marketing hype?

Science.gov (United States)

Baillie, Jonathan

2012-02-01

With energy efficiency and carbon reduction, and the importance of a relaxing, therapeutic patient environment, ever more in the spotlight, LED lighting's proponents claim the technology offers healthcare estates personnel many of the answers on both fronts. However some observers believe its benefits are being over-sold, often to the detriment of other high-performing types of more 'conventional lighting', and to a sometimes uninitiated audience too easily swayed by slick sales patter. HEJ editor Jonathan Baillie spoke to one highly experienced lighting professional, Nicholas Bukorović, a former employee of Thorn, Cooper, and Thorlux Lighting, and the principal author of the last CIBSE/Society of Light and Lighting (SLL) Guide LG2 on healthcare lighting, to seek some expert illumination.

High Flux Commercial Illumination Solution with Intelligent Controls

Energy Technology Data Exchange (ETDEWEB)

Camil Ghiu

2012-04-30

This report summarizes the work performed at OSRAM SYLVANIA under US Department of Energy contract DE-EE0003241 for developing a high efficiency LED-based luminaire. A novel light engine module (two versions: standard and super), power supply and luminaire mechanical parts were designed and tested. At steady-state, the luminaire luminous flux is 3156 lumens (lm), luminous efficacy 97.4 LPW and CRI (Ra) 88 at a correlated color temperature (CCT) of 3507K. When the luminaire is fitted with the super version of the light engine the efficacy reaches 130 LPW. In addition, the luminaire is provided with an intelligent control network capable of additional energy savings. The technology developed during the course of this project has been incorporated into a family of products. Recently, the first product in the family has been launched.

High-power, format-flexible, 885-nm vertical-cavity surface-emitting laser arrays

Science.gov (United States)

Wang, Chad; Talantov, Fedor; Garrett, Henry; Berdin, Glen; Cardellino, Terri; Millenheft, David; Geske, Jonathan

2013-03-01

High-power, format flexible, 885 nm vertical-cavity surface-emitting laser (VCSEL) arrays have been developed for solid-state pumping and illumination applications. In this approach, a common VCSEL size format was designed to enable tiling into flexible formats and operating configurations. The fabrication of a common chip size on ceramic submount enables low-cost volume manufacturing of high-power VCSEL arrays. This base VCSEL chip was designed to be 5x3.33 mm2, and produced up to 50 Watts of peak continuous wave (CW) power. To scale to higher powers, multiple chips can be tiled into a combination of series or parallel configurations tailored to the application driver conditions. In actively cooled CW operation, the VCSEL array chips were packaged onto a single water channel cooler, and we have demonstrated 0.5x1, 1x1, and 1x3 cm2 formats, producing 150, 250, and 500 Watts of peak power, respectively, in under 130 A operating current. In QCW operation, the 1x3 cm2 VCSEL module, which contains 18 VCSEL array chips packaged on a single water cooler, produced over 1.3 kW of peak power. In passively cooled packages, multiple chip configurations have been developed for illumination applications, producing over 300 Watts of peak power in QCW operating conditions. These VCSEL chips use a substrate-removed structure to allow for efficient thermal heatsinking to enable high-power operation. This scalable, format flexible VCSEL architecture can be applied to wavelengths ranging from 800 to 1100 nm, and can be used to tailor emission spectral widths and build high-power hyperspectral sources.

Nano-LED array fabrication suitable for future single photon lithography

International Nuclear Information System (INIS)

Mikulics, M; Hardtdegen, H

2015-01-01

We report on an alternative illumination concept for a future lithography based on single-photon emitters and important technological steps towards its implementation. Nano light-emitting diodes (LEDs) are chosen as the photon emitters. First, the development of their fabrication and their integration technology is presented, then their optical characteristics assessed. Last, size-controlled nano-LEDs, well positioned in an array, are electrically driven and utilized for illumination. Nanostructures are lithographically formed, demonstrating the feasibility of the approach. The potential of single-photon lithography to reach the ultimate scale limits in mass production is discussed. (paper)

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.

Investigation of interface property in Al/SiO2/ n-SiC structure with thin gate oxide by illumination

Science.gov (United States)

Chang, P. K.; Hwu, J. G.

2017-04-01

The reverse tunneling current of Al/SiO2/ n-SiC structure employing thin gate oxide is introduced to examine the interface property by illumination. The gate current at negative bias decreases under blue LED illumination, yet increases under UV lamp illumination. Light-induced electrons captured by interface states may be emitted after the light sources are off, leading to the recovery of gate currents. Based on transient characteristics of gate current, the extracted trap level is close to the light energy for blue LED, indicating that electron capture induced by lighting may result in the reduction of gate current. Furthermore, bidirectional C- V measurements exhibit a positive voltage shift caused by electron trapping under blue LED illumination, while a negative voltage shift is observed under UV lamp illumination. Distinct trapping and detrapping behaviors can be observed from variations in I- V and C- V curves utilizing different light sources for 4H-SiC MOS capacitors with thin insulators.

High Temperature, High Power Piezoelectric Composite Transducers

Science.gov (United States)

Lee, Hyeong Jae; Zhang, Shujun; Bar-Cohen, Yoseph; Sherrit, StewarT.

2014-01-01

Piezoelectric composites are a class of functional materials consisting of piezoelectric active materials and non-piezoelectric passive polymers, mechanically attached together to form different connectivities. These composites have several advantages compared to conventional piezoelectric ceramics and polymers, including improved electromechanical properties, mechanical flexibility and the ability to tailor properties by using several different connectivity patterns. These advantages have led to the improvement of overall transducer performance, such as transducer sensitivity and bandwidth, resulting in rapid implementation of piezoelectric composites in medical imaging ultrasounds and other acoustic transducers. Recently, new piezoelectric composite transducers have been developed with optimized composite components that have improved thermal stability and mechanical quality factors, making them promising candidates for high temperature, high power transducer applications, such as therapeutic ultrasound, high power ultrasonic wirebonding, high temperature non-destructive testing, and downhole energy harvesting. This paper will present recent developments of piezoelectric composite technology for high temperature and high power applications. The concerns and limitations of using piezoelectric composites will also be discussed, and the expected future research directions will be outlined. PMID:25111242

Low Cost Lithography Tool for High Brightness LED Manufacturing

Energy Technology Data Exchange (ETDEWEB)

Andrew Hawryluk; Emily True

2012-06-30

The objective of this activity was to address the need for improved manufacturing tools for LEDs. Improvements include lower cost (both capital equipment cost reductions and cost-ofownership reductions), better automation and better yields. To meet the DOE objective of $1- 2/kilolumen, it will be necessary to develop these highly automated manufacturing tools. Lithography is used extensively in the fabrication of high-brightness LEDs, but the tools used to date are not scalable to high-volume manufacturing. This activity addressed the LED lithography process. During R&D and low volume manufacturing, most LED companies use contact-printers. However, several industries have shown that these printers are incompatible with high volume manufacturing and the LED industry needs to evolve to projection steppers. The need for projection lithography tools for LED manufacturing is identified in the Solid State Lighting Manufacturing Roadmap Draft, June 2009. The Roadmap states that Projection tools are needed by 2011. This work will modify a stepper, originally designed for semiconductor manufacturing, for use in LED manufacturing. This work addresses improvements to yield, material handling, automation and throughput for LED manufacturing while reducing the capital equipment cost.

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.

Optimization of sampling pattern and the design of Fourier ptychographic illuminator.

Science.gov (United States)

Guo, Kaikai; Dong, Siyuan; Nanda, Pariksheet; Zheng, Guoan

2015-03-09

Fourier ptychography (FP) is a recently developed imaging approach that facilitates high-resolution imaging beyond the cutoff frequency of the employed optics. In the original FP approach, a periodic LED array is used for sample illumination, and therefore, the scanning pattern is a uniform grid in the Fourier space. Such a uniform sampling scheme leads to 3 major problems for FP, namely: 1) it requires a large number of raw images, 2) it introduces the raster grid artefacts in the reconstruction process, and 3) it requires a high-dynamic-range detector. Here, we investigate scanning sequences and sampling patterns to optimize the FP approach. For most biological samples, signal energy is concentrated at low-frequency region, and as such, we can perform non-uniform Fourier sampling in FP by considering the signal structure. In contrast, conventional ptychography perform uniform sampling over the entire real space. To implement the non-uniform Fourier sampling scheme in FP, we have designed and built an illuminator using LEDs mounted on a 3D-printed plastic case. The advantages of this illuminator are threefold in that: 1) it reduces the number of image acquisitions by at least 50% (68 raw images versus 137 in the original FP setup), 2) it departs from the translational symmetry of sampling to solve the raster grid artifact problem, and 3) it reduces the dynamic range of the captured images 6 fold. The results reported in this paper significantly shortened acquisition time and improved quality of FP reconstructions. It may provide new insights for developing Fourier ptychographic imaging platforms and find important applications in digital pathology.

Calculation of harmonic losses and ampacity in low-voltage power cables when used for feeding large LED lighting loads

Directory of Open Access Journals (Sweden)

N. J. Milardovich

2014-10-01

Full Text Available A numerical investigation on the harmonic disturbances in low-voltage cables feeding large LED loads is reported. A frequency domain analysis on several commercially-available LEDs was performed to investigate the signature of the harmonic current injected into the power system. Four-core cables and four single-core cable arrangements (three phases and neutral of small, medium, and large conductor cross sections, with the neutral conductor cross section approximately equal to the half of the phase conductors, were examined. The cables were modelled by using electromagnetic finite-element analysis software. High harmonic power losses (up to 2.5 times the value corresponding to an undistorted current of the same rms value of the first harmonic of the LED current were found. A generalized ampacity model was employed for re-rating the cables. It was found that the cross section of the neutral conductor plays an important role in the derating of the cable ampacity due to the presence of a high-level of triplen harmonics in the distorted current. The ampacity of the cables should be derated by about 40 %, almost independent of the conductor cross sections. The calculation have shown that an incoming widespread use of LED lamps in lighting could create significant additional harmonic losses in the supplying low-voltage lines, and thus more severely harmonic emission limits should be defined for LED lamps.

Evaluation of current and temperature effects on optical performance of InGaAlP thin-film SMD LED mounted on different substrate packages

International Nuclear Information System (INIS)

Raypah, Muna E.; Devarajan, Mutharasu; Sulaiman, Fauziah

2017-01-01

The relationship between the photometric, electric, and thermal parameters of light-emitting diodes (LEDs) is important for optimizing the LED illumination design. Indium gallium aluminium phosphide (InGaAlP)-based thin-film surface-mounted device (SMD) LEDs have attracted wide attention in research and development due to their portability and miniaturization. We report the optical characterization of InGaAlP thin-film SMD LED mounted on FR4, 2 W, and 5 W aluminum (Al) packages. The optical and thermal parameters of LED are determined at different injection currents and ambient temperatures by combining the T3ster (thermal transient tester) and TeraLED (thermal and radiometric characterization of power LEDs) systems. Analysis shows that LED on a 5 W Al substrate package obtains the highest luminous and optical efficiency. (paper)

BiliLED low cost neonatal phototherapy, from prototype to industry

Energy Technology Data Exchange (ETDEWEB)

Geido, Daniel; Failache, Horacio [Instituto de Fisica de la Facultad de Ingenieria - Universidad de la Republica, Montevideo (Uruguay); Simini, Franco [Nucleo de Ingenieria Biomedica de las Facultades de Medicina e Ingenieria (Uruguay); Hospital de ClInicas. Av Italia S/N. Piso 15 sala 2, 11600 Montevideo (Uruguay)

2007-11-15

BiliLED is a phototherapy instrument designed to reduce bilirrubin blood rates in new born babies with jaundice. The light source is centred at 470 nm with a bandwidth of 35 nm and includes a matrix of 196 (14x14) InGaN LEDs. The optical elements are designed to maximize the light intensity useful for treatment, with a small number of LEDs in a compact and low cost unit. The optic array is such that every LED illuminates all the treatment area, which ensures redundancy and, thus, a high reliability not to be found in single-lamp instruments. Thermal dissipation and cost of BiliLED are both an order-of-magnitude smaller than conventional therapy lamps. BiliLED adjusts coetaneous irradiation with a feedback loop to compensate the loss or aging of LEDs achieving a calibrated light source for over a decade of use. A clinical trial in 20 hyperbilirrubinaemia patients shows 16% bilirrubin degradation within 24 hours of treatment, higher than most lamp phototherapy instruments. The steps from prototype to commercial model are described.

BiliLED low cost neonatal phototherapy, from prototype to industry

Science.gov (United States)

Geido, Daniel; Failache, Horacio; Simini, Franco

2007-11-01

BiliLED is a phototherapy instrument designed to reduce bilirrubin blood rates in new born babies with jaundice. The light source is centred at 470 nm with a bandwidth of 35 nm and includes a matrix of 196 (14×14) InGaN LEDs. The optical elements are designed to maximize the light intensity useful for treatment, with a small number of LEDs in a compact and low cost unit. The optic array is such that every LED illuminates all the treatment area, which ensures redundancy and, thus, a high reliability not to be found in single-lamp instruments. Thermal dissipation and cost of BiliLED are both an order-of-magnitude smaller than conventional therapy lamps. BiliLED adjusts coetaneous irradiation with a feedback loop to compensate the loss or aging of LEDs achieving a calibrated light source for over a decade of use. A clinical trial in 20 hyperbilirrubinaemia patients shows 16% bilirrubin degradation within 24 hours of treatment, higher than most lamp phototherapy instruments. The steps from prototype to commercial model are described.

BiliLED low cost neonatal phototherapy, from prototype to industry

International Nuclear Information System (INIS)

Geido, Daniel; Failache, Horacio; Simini, Franco

2007-01-01

BiliLED is a phototherapy instrument designed to reduce bilirrubin blood rates in new born babies with jaundice. The light source is centred at 470 nm with a bandwidth of 35 nm and includes a matrix of 196 (14x14) InGaN LEDs. The optical elements are designed to maximize the light intensity useful for treatment, with a small number of LEDs in a compact and low cost unit. The optic array is such that every LED illuminates all the treatment area, which ensures redundancy and, thus, a high reliability not to be found in single-lamp instruments. Thermal dissipation and cost of BiliLED are both an order-of-magnitude smaller than conventional therapy lamps. BiliLED adjusts coetaneous irradiation with a feedback loop to compensate the loss or aging of LEDs achieving a calibrated light source for over a decade of use. A clinical trial in 20 hyperbilirrubinaemia patients shows 16% bilirrubin degradation within 24 hours of treatment, higher than most lamp phototherapy instruments. The steps from prototype to commercial model are described

High-Power Lasers for Science and Society

Energy Technology Data Exchange (ETDEWEB)

Siders, C. W. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Haefner, C. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2016-10-05

Since the first demonstration of the laser in 1960 by Theodore Maiman at Hughes Research Laboratories, the principal defining characteristic of lasers has been their ability to focus unprecedented powers of light in space, time, and frequency. High-power lasers have, over the ensuing five and a half decades, illuminated entirely new fields of scientific endeavor as well as made a profound impact on society. While the United States pioneered lasers and their early applications, we have been eclipsed in the past decade by highly effective national and international networks in both Europe and Asia, which have effectively focused their energies, efforts, and resources to achieve greater scientific and societal impact. This white paper calls for strategic investment which, by striking an appropriate balance between distributing our precious national funds and establishing centers of excellence, will ensure a broad pipeline of people and transformative ideas connecting our world-leading universities, defining flagship facilities stewarded by our national laboratories, and driving innovation across industry, to fully exploit the potential of high-power lasers.

Peer-led versus teacher-led AIDS education for female high-school students in Yazd, Islamic Republic of Iran.

Science.gov (United States)

Baghianimoghadam, M H; Forghani, H; Zolghadr, R; Rahaei, Z; Khani, P

2012-04-01

Peer-led programmes on AIDS prevention have shown a good level of effectiveness when tested among high-risk populations. This study compared peer-led and teacher-led methods of education about HIV/AIDS among female high-school students in Yazd city, Islamic Republic of Iran. In 2009 students in 3 high schools were trained by their classmates (peer-led), by the research team (teacher-led) or had no education (controls); 180 students completed a specially designed questionnaire based on the health belief model, before and after the intervention. Post-intervention mean knowledge scores increased 2-fold in the peer-led group, and this was significantly higher than the increase in the teacher-led group scores (1.5-fold). Control group scores were unchanged. In the peer-led programme all of the components of the model were significantly improved whereas in the teacher-led programme, only perceived severity and perceived barriers scored significantly higher after the intervention.

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.

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.

Optical characterization of ultrabright LEDs

International Nuclear Information System (INIS)

Benavides, Juan Manuel; Webb, Robert H.

2005-01-01

Ultrabright light emitting diodes (LEDs) are a new light source for visual psychophysics and microscopy. The new LEDs are intended primarily for room and exterior illumination, and the manufacturers' specifications are adequate for that. However, we use them as light sources in situations where a more complete characterization may be useful. For one set of LEDs we have measured the radiometric intensity and its distribution in space and wavelength, and we have tested for interactions of these variables and their dependence on driver configuration. We describe techniques for making these measurements and give a link to a simple calculator for converting among radiometric and photometric measures, as well as an evaluation of the safety considerations these very bright sources demand

Optical design applications for enhanced illumination performance

Science.gov (United States)

Gilray, Carl; Lewin, Ian

1995-08-01

Nonimaging optical design techniques have been applied in the illumination industry for many years. Recently however, powerful software has been developed which allows accurate simulation and optimization of illumination devices. Wide experience has been obtained in using such design techniques for practical situations. These include automotive lighting where safety is of greatest importance, commercial lighting systems designed for energy efficiency, and numerous specialized applications. This presentation will discuss the performance requirements of a variety of illumination devices. It will further cover design methodology and present a variety of examples of practical applications for enhanced system performance.

A spectral image processing algorithm for evaluating the influence of the illuminants on the reconstructed reflectance

Science.gov (United States)

Toadere, Florin

2017-12-01

A spectral image processing algorithm that allows the illumination of the scene with different illuminants together with the reconstruction of the scene's reflectance is presented. Color checker spectral image and CIE A (warm light 2700 K), D65 (cold light 6500 K) and Cree TW Series LED T8 (4000 K) are employed for scene illumination. Illuminants used in the simulations have different spectra and, as a result of their illumination, the colors of the scene change. The influence of the illuminants on the reconstruction of the scene's reflectance is estimated. Demonstrative images and reflectance showing the operation of the algorithm are illustrated.

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)

Measurement of the photometric characteristics of LEDs

International Nuclear Information System (INIS)

Nazarenko, L.A.; Zubkov, D.P.

2015-01-01

Proposed and implemented a method for measuring LEDs, which is based on self-calibration of the LED goniophotometer facility by using a trap-detector. Designed and manufactured automated goniophotometer, which provides a measurement of high power LEDs at a specified junction temperature. Designed and experimentally researched the photometer with a photometric sphere based diffuser, which meets all requirements of CIE for photometric measurements of LEDs

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.

Low light illumination study on commercially available homojunction photovoltaic cells

International Nuclear Information System (INIS)

Russo, Johnny; Ray, William; Litz, Marc S.

2017-01-01

Highlights: • COTS PV cells are tested under indoor and narrow light spectra. • InGaP is the most efficient under low light conditions (0.5–100 μW_o_p_t/cm"2). • InGaP is selected for isotope battery. • Optimal incident wavelength (614 nm) for InGaP is identified in model. - Abstract: Low illumination (10"−"4 suns) and indoor light energy harvesting is needed to meet the demands of zero net energy (ZNE) building, Internet of Things (IoT), and beta-photovoltaic energy harvesting systems to power remote sensors. Photovoltaic (PV) solar cells under low intensity and narrow (±40 nm) light spectrum conditions are not well characterized nor developed, especially for commercially available devices and scalable systems. PV operating characteristics under 1 sun illumination decrease at lower light intensity and narrow spectrum conditions (efficiency drops from ∼25% at 100 mW_o_p_t/cm"2 to 2% at 1 μW_o_p_t/cm"2). By choosing a PV with a bandgap that matches the light source operating wavelength, the total system efficiency can be improved. By quantifying losses on homojunction photovoltaics (thermalization and leakage current), we have determined the theoretical optimized efficiency for a set of PV material and a selected set of light sources. We measure single-junction solar cells’ parameters under three different light sources (indoor light and narrow spectrum LED sources) with light intensities ranging from 0.5 to 100 μW_o_p_t/cm"2. Measurements show that indium gallium phosphide (InGaP) PV has the highest surface power density and conversion efficiency (29% under ≈1 μW_o_p_t/cm"2 from a 523 nm central peak LED). A beta-photovoltaic experimental study identifies InGaP to be optimized for use with the ZnS:Cu, Al and tritium at STP. The results have guided the selection of PV material for scalable isotope batteries and other low-light energy harvesting systems.

A transmitting antenna with hexagon illumination shape for four-color VLC

Science.gov (United States)

Liu, Kexin; Zhang, Lijun; Hu, Shanshan; Xing, Jichuan; Li, Ping'an

2018-01-01

This paper demonstrated a compact white light transmitting antenna based on four-color VLC system, which included an integrating rod and a Fresnel lens system. This paper mainly analyzed the homogenizer: the hexagon integrating rod. After simulation and optimizing, the size of this rod is designed as 60mm (length) x 4.35mm (D). As a result of experiments, this antenna which mixes RGBY-LEDs' beam into white light with high uniformity (67.18%), and illuminate the area of 0.75m x 0.75m at 1.77m transmission distance. The color temperature of the detection surface is 5583K, the chromatic aberration is 0.0021, compared with light source E of standard illumination, less than eye solution (0.005). Also, we verified that this antenna could ensure a stable SNR in mobile communication.

Morphology Evolution and Degradation of CsPbBr3 Nanocrystals under Blue Light-Emitting Diode Illumination.

Science.gov (United States)

Huang, Shouqiang; Li, Zhichun; Wang, Bo; Zhu, Nanwen; Zhang, Congyang; Kong, Long; Zhang, Qi; Shan, Aidang; Li, Liang

2017-03-01

Under illumination of light-emitting diode (LED) or sunlight, the green color of all-inorganic CsPbBr 3 perovskite nanocrystals (CPB-NCs) often quickly changes to yellow, followed by large photoluminescence (PL) loss. To figure out what is happening on CPB-NCs during the color change process, the morphology, structure, and PL evolutions are systematically investigated by varying the influence factors of illumination, moisture, oxygen, and temperature. We find that the yellow color is mainly originated from the large CPB crystals formed in the illumination process. With maximized isolation of oxygen for the sandwiched film or the uncovered film stored in nitrogen, the color change can be dramatically slowed down whether there is water vapor or not. Under dark condition, the PL emissions are not significantly influenced by the varied relative humidity (RH) levels and temperatures up to 60 °C. Under the precondition of oxygen or air, color change and PL loss become more obvious when increasing the illumination power or RH level, and the large-sized cubic CPB crystals are further evolved into the oval-shaped crystals. We confirm that oxygen is the crucial factor to drive the color change, which has the strong synergistic effect with the illumination and moisture for the degradation of the CPB film. Meanwhile, the surface decomposition and the increased charge trap states occurred in the formed large CPB crystals play important roles for the PL loss.

CALiPER Application Summary Report 21. Linear (T8) LED Lamps

Energy Technology Data Exchange (ETDEWEB)

None

2014-03-01

This report focuses on the bare lamp performance of 31 linear LED lamps intended as an alternative to T8 fluorescent lamps. Data obtained in accordance with IES LM-79-08 indicated that the mean efficacy is similar to that of fluorescent lamps, but that lumen output is often much lower. This presents a situation where something must change in order for energy savings and equivalent illumination levels to be achieved simultaneously. In this case, the luminous intensity distribution of all the tested lamps was directional or semi-directional, rather than omnidirectional. Also discussed in this report are several issues related to the electrical configuration of the lamps, such as the required socket types and power feed location. While no configuration is necessarily better, the multitude of options can make specifying and installing linear LED lamps more difficult, with the potential for safety issues. Similarly, the variety of color and power quality attributes adds a layer of complexity to the specification process. Many products offered good or excellent quality attributes, but some did not and thus could be perceived as inferior to fluorescent lamps in some installations.

Yuma Border Patrol Area Lighting Retrofit LED System Performance in a Trial Installation – Two Years Later

Energy Technology Data Exchange (ETDEWEB)

Wilkerson, Andrea M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Sullivan, Gregory P. [Efficiency Solutions, Inc, Richland, WA (United States); Davis, Robert G. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

2016-05-21

Documentation of the Yuma Sector Border Patrol Area lighting LED trial demonstration continues to provide a better understanding of LED technology performance in a high ambient temperature and high solar radiation environment. Measured data at the project site showed illuminances changing more rapidly than anticipated. As previously predicted, the causes for these observed changes are mostly if not completely explained by dirt accumulation. The laboratory measurements showed not only the effect of dirt on lumen output, but also on the distribution of light exiting the luminaire.

Analysis of technology and seminar on economic trends about High-intensity LED

International Nuclear Information System (INIS)

2003-09-01

This is divided into two parts. Contents of this report in the first part are technical trends on high-intensity LED which reports introduction of LED as compound semiconductor, white LED? patent issues, review on technology of High-intensity LED and Reliability of High-intensity LED. The second part deals with economic tends about High-intensity LED. This seminar was held to report analysis and economical trends about High-intensity LED by Korea Industrial Education Institute in 2003.

Generation of realistic scene using illuminant estimation and mixed chromatic adaptation

Science.gov (United States)

Kim, Jae-Chul; Hong, Sang-Gi; Kim, Dong-Ho; Park, Jong-Hyun

2003-12-01

The algorithm of combining a real image with a virtual model was proposed to increase the reality of synthesized images. Currently, synthesizing a real image with a virtual model facilitated the surface reflection model and various geometric techniques. In the current methods, the characteristics of various illuminants in the real image are not sufficiently considered. In addition, despite the chromatic adaptation plays a vital role for accommodating different illuminants in the two media viewing conditions, it is not taken into account in the existing methods. Thus, it is hardly to get high-quality synthesized images. In this paper, we proposed the two-phase image synthesis algorithm. First, the surface reflectance of the maximum high-light region (MHR) was estimated using the three eigenvectors obtained from the principal component analysis (PCA) applied to the surface reflectances of 1269 Munsell samples. The combined spectral value, i.e., the product of surface reflectance and the spectral power distributions (SPDs) of an illuminant, of MHR was then estimated using the three eigenvectors obtained from PCA applied to the products of surface reflectances of Munsell 1269 samples and the SPDs of four CIE Standard Illuminants (A, C, D50, D65). By dividing the average combined spectral values of MHR by the average surface reflectances of MHR, we could estimate the illuminant of a real image. Second, the mixed chromatic adaptation (S-LMS) using an estimated and an external illuminants was applied to the virtual-model image. For evaluating the proposed algorithm, experiments with synthetic and real scenes were performed. It was shown that the proposed method was effective in synthesizing the real and the virtual scenes under various illuminants.

Novel technique for solar power illumination using plastic optical fibres

Science.gov (United States)

Munisami, J.; Kalymnios, D.

2008-09-01

Plastic Optical Fibres (POF) were developed almost 3 decades ago. They are mainly used for short haul data communications (up to 1 km with data rates up to 1 Gbps). Over the years, POF has found applications in many other areas including solar energy transport for illumination. In such an application, light is collected from the sun and is directed into a space which needs to be illuminated. The use of fibres and more specifically POF, in daylighting systems, started only a few years ago. Several approaches have been investigated and we have seen the development of a few commercial products. The market however, has not really taken off for these technologies simply because of their enormous price tags. It is important to note that the use of POF in these designs has been limited to the function of POF as the transmission medium only. We propose a novel solar illumination technique using POF as both the light collecting/concentrating mechanism and the transmission medium. By modifying the structure of the fibre, solar light can be directed into the fibre by using an analogous process to fibre side emission but, in the reverse. We shall report on the solar light capturing efficiency of POF as modified by several types of external imperfections introduced onto the fibre. One major advantage of our proposed approach lies in the fact that we aim to eliminate at least one of the two axes of sun tracking that is currently used in existing solar illumination systems.

Structural optimization of a microjet based cooling system for high power LEDs

Energy Technology Data Exchange (ETDEWEB)

Sheng Liu; Zhiyin Gan [Institute for Microsystems, School of Mechanical Engineering, Huazhong University of Science and Technology, Wuhan (China); Wuhan National Lab of Optoelectronics, Huazhong University of Science and Technology, Wuhan (China); Jianghui Yang [School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan (China); Xiaobing Luo [Wuhan National Lab of Optoelectronics, Huazhong University of Science and Technology, Wuhan (China); School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan (China)

2008-08-15

Based on the previous experiments and simulations reported by the present authors, it was found the cooling system could be optimized to obtain better performance. In this paper, the microjet cooling systems with three different microjet structures were numerically investigated. The numerical model was proven by the experiments. The optimization results demonstrate that the microjet structure with one single inlet but two outlets can achieve better cooling performance. The simulation results show that the maximum temperature of the LED substrate cooled by the optimized microjet cooling device was 23 K lower than that of the LED substrate cooled by the present experimental cooling system. (author)

The influence of sputtering power and O2/Ar flow ratio on the performance and stability of Hf-In-Zn-O thin film transistors under illumination

International Nuclear Information System (INIS)

Kim, Hyun-Suk; Park, Kyung-Bae; Son, Kyoung Seok; Park, Joon Seok; Maeng, Wan-Joo; Kim, Tae Sang; Lee, Kwang-Hee; Kim, Eok Su; Lee, Jiyoul; Suh, Joonki; Seon, Jong-Baek; Ryu, Myung Kwan; Lee, Sang Yoon; Lee, Kimoon; Im, Seongil

2010-01-01

The performance and stability of amorphous HfInZnO thin film transistors under visible light illumination were studied. The extent of device degradation upon negative bias stress with the presence of visible light is found to be strongly sensitive to the extent of photoelectric effect in the oxide semiconductor. Highly stable devices were fabricated by optimizing the deposition conditions of HfInZnO films, where the combination of high sputtering power and high O 2 /Ar gas flow ratio was found to result in the highest stability under bias stress experiments.

A Single-Stage LED Tube Lamp Driver with Power-Factor Corrections and Soft Switching for Energy-Saving Indoor Lighting Applications

Directory of Open Access Journals (Sweden)

Chun-An Cheng

2017-01-01

Full Text Available This paper presents a single-stage alternating current (AC/direct current (DC light-emitting diode (LED tube lamp driver for energy-saving indoor lighting applications; this driver features power-factor corrections and soft switching, and also integrates a dual buck-boost converter with coupled inductors and a half-bridge series resonant converter cascaded with a bridge rectifier into a single-stage power-conversion topology. The features of the presented driver are high efficiency (>91%, satisfying power factor (PF > 0.96, low input-current total-harmonic distortion (THD < 10%, low output voltage ripple factor (<7.5%, low output current ripple factor (<8%, and zero-voltage switching (ZVS obtained on both power switches. Operational principles are described in detail, and experimental results obtained from an 18 W-rated LED tube lamp for T8/T10 fluorescent lamp replacements with input utility-line voltages ranging from 100 V to 120 V have demonstrated the functionality of the presented driver suitable for indoor lighting applications.

Design and Fabrication of Air-core Inductors for Power Conversion

DEFF Research Database (Denmark)

Lê Thanh, Hoà; Mizushima, Io; Tang, Peter Torben

supply on chip (PwrSoC) [1]. Examples of PwrSoC applications are power adaptors for LED illumination and the “Internet of Things”. We report an air-core MEMS inductor. Our process is scalable and universal for making inductors with versatile geometries e.g. spiral, solenoid, toroid, and advanced...

Off-axis low coherence digital holographic interferometry for quantitative phase imaging with an LED

Science.gov (United States)

Guo, Rongli; Wang, Fan; Hu, Xiaoying; Yang, Wenqian

2017-11-01

Off-axis digital holographic interferometry with the light source of a light emitting diode (LED) is presented and its application for quantitative phase imaging in a large range with low noise is demonstrated. The scheme is implemented in a grating based Mach-Zehnder interferometer. To achieve off-axis interferometry, firstly, the collimated beam emitted from an LED is diffracted into multiple orders by a grating and they are split into two copies by a beam splitter; secondly, in the object arm the zero order of one copy is filtered in the Fourier plane and is reshaped to illuminate the sample, while in the reference arm one of its first order of another copy is selected to serve as the reference beam, and then an off-axis hologram can be obtained at the image plane. The main advantage stemming from an LED illumination is its high spatial phase resolution, due to the subdued speckle effect. The off-axis geometry enables one-shot recording of the hologram in the millisecond scale. The utility of the proposed setup is illustrated with measurements of a resolution target and part of a wing of green-lacewing, and dynamic evaporation process of an ethanol film.

The relationship between ambient illumination and psychological factors in viewing of display Images

Science.gov (United States)

Iwanami, Takuya; Kikuchi, Ayano; Kaneko, Takashi; Hirai, Keita; Yano, Natsumi; Nakaguchi, Toshiya; Tsumura, Norimichi; Yoshida, Yasuhiro; Miyake, Yoichi

2009-01-01

In this paper, we have clarified the relationship between ambient illumination and psychological factors in viewing of display images. Psychological factors were obtained by the factor analysis with the results of the semantic differential (SD) method. In the psychological experiments, subjects evaluated the impressions of displayed images with changing ambient illuminating conditions. The illumination conditions were controlled by a fluorescent ceiling light and a color LED illumination which was located behind the display. We experimented under two kinds of conditions. One was the experiment with changing brightness of the ambient illumination. The other was the experiment with changing the colors of the background illumination. In the results of the experiment, two factors "realistic sensation, dynamism" and "comfortable," were extracted under different brightness of the ambient illumination of the display surroundings. It was shown that the "comfortable" was improved by the brightness of display surroundings. On the other hand, when the illumination color of surroundings was changed, three factors "comfortable," "realistic sensation, dynamism" and "activity" were extracted. It was also shown that the value of "comfortable" and "realistic sensation, dynamism" increased when the display surroundings were illuminated by the average color of the image contents.

Advanced imaging techniques III: a scalable and modular dome illumination system for scientific microphotography on a budget

Science.gov (United States)

A scalable and modular LED illumination dome for microscopic scientific photography is described and illustrated, and methods for constructing such a dome are detailed. Dome illumination for insect specimens has become standard practice across the field of insect systematics, but many dome designs ...

Illumination invariant feature point matching for high-resolution planetary remote sensing images

Science.gov (United States)

Wu, Bo; Zeng, Hai; Hu, Han

2018-03-01

Despite its success with regular close-range and remote-sensing images, the scale-invariant feature transform (SIFT) algorithm is essentially not invariant to illumination differences due to the use of gradients for feature description. In planetary remote sensing imagery, which normally lacks sufficient textural information, salient regions are generally triggered by the shadow effects of keypoints, reducing the matching performance of classical SIFT. Based on the observation of dual peaks in a histogram of the dominant orientations of SIFT keypoints, this paper proposes an illumination-invariant SIFT matching method for high-resolution planetary remote sensing images. First, as the peaks in the orientation histogram are generally aligned closely with the sub-solar azimuth angle at the time of image collection, an adaptive suppression Gaussian function is tuned to level the histogram and thereby alleviate the differences in illumination caused by a changing solar angle. Next, the suppression function is incorporated into the original SIFT procedure for obtaining feature descriptors, which are used for initial image matching. Finally, as the distribution of feature descriptors changes after anisotropic suppression, and the ratio check used for matching and outlier removal in classical SIFT may produce inferior results, this paper proposes an improved matching procedure based on cross-checking and template image matching. The experimental results for several high-resolution remote sensing images from both the Moon and Mars, with illumination differences of 20°-180°, reveal that the proposed method retrieves about 40%-60% more matches than the classical SIFT method. The proposed method is of significance for matching or co-registration of planetary remote sensing images for their synergistic use in various applications. It also has the potential to be useful for flyby and rover images by integrating with the affine invariant feature detectors.

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...

MECHANISMS OF MELATONIN EFFECTS UPON IMMUNE STATE IN EXPERIMENTAL DESYNCHRONOSES PRODUCED UNDER THE LED ILLUMINATION CONDITIONS

Directory of Open Access Journals (Sweden)

M. V. Osikov

2015-01-01

Full Text Available Disorders of immune state in desynchronosis may be associated with reduced concentrations of melatonin in blood, thus being a prerequisite for pharmacological correction of appropriate homeostatic changes. The purpose of this work was to explore some mechanisms of exogenous melatonin actions upon parameters of innate and adaptive immunity in experimental model of desynchronosis under the conditions of LED illumination. The study was performed with 196 adult guinea pigs. Light desynchronosis was produced by day-and-night illumination of the animals having been continued for 30 days. Melatonin was administered applied per os daily at the total dose of 30 mg/kg. A solution of melatonin in isotonic NaCl solution was prepared from the Melaxen drug (INN: melatonin, “Unipharm Inc.,” USA ex tempore. To study innate immunity of blood cells, we determined leukocyte numbers, WBC differential counts, and functional activity of phagocytes, as spontaneous and induced NBT test, as well as engulfment of polystyrene latex particles. Th1-specific immune response was studied according to degree of delayed type hypersensitivity reaction; Th2-dependent response was assessed as the numbers of antibody-forming cells in the spleen of the animals after immunization with allogeneic erythrocytes. Serum concentrations of interleukin 4 (IL-4, interferon-gamma (IFNγ, melatonin, and cortisol were measured by enzyme immunoassay, using the “Immulayt 2000” (USA with guinea pigspecific test systems. It was found that experimental desynchronosis was associated with leukocytosis, lymphoand monocytopenia, activation of oxygen-dependent metabolism of blood phagocytes, suppression of Th1-and Th2-dependent immune response. Desynchronosis was also accompanied by decreased concentrations of serum melatonin, IFNγ and IL-4, along with increased cortisol concentrations. Reduced IFNγ and IL-4 amounts was associated with decreased melatonin concentrations

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.

Dynamic thermal model of photovoltaic cell illuminated by laser beam

Science.gov (United States)

Liu, Xiaoguang; Hua, Wenshen; Guo, Tong

2015-07-01

Photovoltaic cell is one of the most important components of laser powered unmanned aerial vehicle. Illuminated by high power laser beam, photovoltaic cell temperature increases significantly, which leads to efficiency drop, or even physical damage. To avoid such situation, the temperature of photovoltaic cell must be predicted precisely. A dynamic thermal model of photovoltaic cell is established in this paper, and the relationships between photovoltaic cell temperature and laser power, wind speed, ambient temperature are also analyzed. Simulation result indicates that illuminated by a laser beam, the temperature of photovoltaic cell rises gradually and reach to a constant maximum value. There is an approximately linear rise in photovoltaic cell temperature as the laser flux gets higher. The higher wind speed is, the stronger forced convection is, and then the lower photovoltaic cell temperature is. But the relationship between photovoltaic cell temperature and wind speed is not linear. Photovoltaic cell temperature is proportional to the ambient temperature. For each increase of 1 degree of ambient temperature, there is approximate 1 degree increase in photovoltaic cell temperature. The result will provide fundamentals to take reasonable measures to control photovoltaic cell temperature.

Colorimetric characterization of LED luminaires

International Nuclear Information System (INIS)

Costa, C L M; Vieira, R R; Pereira, R C; Silva, P V M; Oliveira, I A A; Sardinha, A S; Viana, D D; Barbosa, A H; Souza, L P; Alvarenga, A D

2015-01-01

The Optical Metrology Division of Inmetro – National Institute of Metrology, Quality and Technology has recently started the colorimetric characterization of lamps by implementing Correlated Color Temperature (CCT) and Color Rendering Index (CRI) measurements of incandescent lamps, followed by the CFL, and LED lamps and luminaires. Here we present the results for the verification of the color characterization of samples of SSL luminaires for public as well as indoor illumination that are sold in Brazil

Optimal sun-shading design for enhanced daylight illumination of subtropical classrooms

Energy Technology Data Exchange (ETDEWEB)

Ho, Ming-Chin [Architecture and Building Research Institute, MOI (China); Chiang, Che-Ming [Department of Architecture, National Cheng-Kung University, Tainan 701 (China); Chou, Po-Cheng [Department of Interior Design, Shu-Te University, No. 59 Hun-Shan Road, Yenchau 82445, Kaohsiung County (China); Chang, Kuei-Feng [Department of Real Estate Management, National Pingtung Institute of Commerce (China); Lee, Chia-Yen [Department of Mechanical and Automation Engineering, Da-Yeh University, Changhua 515 (China)

2008-07-01

This study investigates the feasibility of fitting windows with sun-shadings in order to minimize the lighting power costs in daylight-illuminated classrooms lit from a single side in subtropical regions. An IES-CPC model is created of a representative classroom in Taiwan, and a series of simulations is performed to determine the average illuminance value and the uniformity of the illuminance distribution in the classroom under various lighting conditions with no sun-shadings fitted to the window. The numerical results are found to be in good agreement with the experimental measurements obtained using an array of nine-channel photometers. Having confirmed the validity of the simulation scheme, the illumination properties of four different sun-shading designs are considered. The results show that a double-layered sun-shading represents the optimal sun-shading design in terms of achieving a uniform illumination distribution within the classroom. Given appropriate physical dimensions, this daylight access device achieves the minimum illuminance requirement of 500 lx and improves the lighting uniformity ratio from 0.25-0.35 to 0.40-0.42. Furthermore, using this sun-shading device, the required illuminance ratio of 0.5 can be obtained simply by switching on one of the three rows of lights in the classroom. Accordingly, the daylight access device not only improves the illuminance conditions within the classroom, but also reduces the lighting power cost by 71.5% compared to the case where all of the lights are turned on. (author)

A synthetic method of solar spectrum based on LED

Science.gov (United States)

Wang, Ji-qiang; Su, Shi; Zhang, Guo-yu; Zhang, Jian

2017-10-01

A synthetic method of solar spectrum which based on the spectral characteristics of the solar spectrum and LED, and the principle of arbitrary spectral synthesis was studied by using 14 kinds of LED with different central wavelengths.The LED and solar spectrum data were selected by Origin Software firstly, then calculated the total number of LED for each center band by the transformation relation between brightness and illumination and Least Squares Curve Fit in Matlab.Finally, the spectrum curve of AM1.5 standard solar spectrum was obtained. The results met the technical indexes of the solar spectrum matching with ±20% and the solar constant with >0.5.

Illumination Conditions of the Lunar Polar Regions Using LOLA Topography

Science.gov (United States)

Mazarico, E.; Neumann, G. A.; Smith, D. E.; Zuber, M. T.; Torrence, M. H.

2011-01-01

We use high-resolution altimetry data obtained by the Lunar Orbiter Laser Altimeter instrument onboard the Lunar Reconnaissance Orbiter to characterize present illumination conditions in the polar regions of the Moon. Compared to previous studies, both the spatial and temporal extent of the simulations are increased significantly, as well as the coverage (fill ratio) of the topographic maps used, thanks to the 28 Hz firing rate of the five-beam instrument. We determine the horizon elevation in a number of directions based on 240 m-resolution polar digital elevation models reaching down to 75 latitude. The illumination of both polar regions extending to 80 can be calculated for any geometry from those horizon longitudinal profiles. We validated our modeling with recent Lunar Reconnaissance Orbiter Wide-Angle Camera images. We assessed the extent of permanently shadowed regions (PSRs, defined as areas that never receive direct solar illumination), and obtained total areas generally larger than previous studies (12,866 and 16,055 km2, in the north and south respectively). We extended our direct illumination model to account for singly-scattered light, and found that every PSR does receive some amount of scattered light during the year. We conducted simulations over long periods (several 18.6-years lunar precession cycles) with a high temporal resolution (6 h), and identified the most illuminated locations in the vicinity of both poles. Because of the importance of those sites for exploration and engineering considerations, we characterized their illumination more precisely over the near future. Every year, a location near the Shackleton crater rim in the south polar region is sunlit continuously for 240 days, and its longest continuous period in total darkness is about 1.5 days. For some locations small height gains ( 10 m) can dramatically improve their average illumination and reduce the night duration, rendering some of those particularly attractive energy-wise as

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.

Refrigerating liquid prototype for LED's thermal management

International Nuclear Information System (INIS)

Faranda, Roberto; Guzzetti, Stefania; Lazaroiu, George Cristian; Leva, Sonia

2012-01-01

The heat management is the critical factor for high performance operation of LED. A new heat management application of refrigerating liquid integrated within a fabricated prototype is proposed and investigated. A series of experiments considering different heights of liquid level were performed to evaluate the heat dissipation performance and optical characteristics of the refrigerating liquid based prototype. The results reveal that the junction temperature decreases as the level of refrigerating liquid increases. The experimental results report that the refrigerating liquid reduces the junction temperature, and can positively influence the luminous radiation performances. An optimization investigation of the proposed solution was carried out to find an optimum thermal performance. The experiments indicated that refrigerating liquid cooling is a powerful way for heat dissipation of high power LEDs, and the fabrication of prototype was feasible and useful. - Highlights: ► New heat management application of refrigerating liquid on a fabricated LED prototype. ► Thermal models setup and comparison between the classical and the new solutions. ► The impact of refrigerating liquid level on LED thermal and luminous performances. ► The relationship between different levels of liquid with LED prototype performances.

Comparison of Square and Radial Geometries for High Intensity Laser Power Beaming Receivers

Science.gov (United States)

Raible, Daniel E.; Fast, Brian R.; Dinca, Dragos; Nayfeh, Taysir H.; Jalics, Andrew K.

2012-01-01

In an effort to further advance a realizable form of wireless power transmission (WPT), high intensity laser power beaming (HILPB) has been developed for both space and terrestrial applications. Unique optical-to-electrical receivers are employed with near infrared (IR-A) continuous-wave (CW) semiconductor lasers to experimentally investigate the HILPB system. In this paper, parasitic feedback, uneven illumination and the implications of receiver array geometries are considered and experimental hardware results for HILPB are presented. The TEM00 Gaussian energy profile of the laser beam presents a challenge to the effectiveness of the receiver to perform efficient photoelectric conversion, due to the resulting non-uniform illumination of the photovoltaic cell arrays. In this investigation, the geometry of the receiver is considered as a technique to tailor the receiver design to accommodate the Gaussian beam profile, and in doing so it is demonstrated that such a methodology is successful in generating bulk receiver output power levels reaching 25 W from 7.2 sq cm of photovoltaic cells. These results are scalable, and may be realized by implementing receiver arraying and utilizing higher power source lasers to achieve a 1.0 sq m receiver capable of generating over 30 kW of electrical power. This type of system would enable long range optical "refueling" of electric platforms, such as MUAV s, airships, robotic exploration missions and provide power to spacecraft platforms which may utilize it to drive electric means of propulsion. In addition, a smaller HILPB receiver aperture size could be utilized to establish a robust optical communications link within environments containing high levels of background radiance, to achieve high signal to noise ratios.

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.

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.

A Scalable and Modular Dome Illumination System for Scientific Microphotography on a Budget.

Directory of Open Access Journals (Sweden)

Ricardo Kawada

Full Text Available A scalable and modular LED illumination dome for microscopic scientific photography is described and illustrated, and methods for constructing such a dome are detailed. Dome illumination for insect specimens has become standard practice across the field of insect systematics, but many dome designs remain expensive and inflexible with respect to new LED technology. Further, a one-size-fits-all dome cannot accommodate the large breadth of insect size encountered in nature, forcing the photographer to adapt, in some cases, to a less than ideal dome design. The dome described here is scalable, as it is based on a isodecahedron, and the template for the dome is available as a downloaded file from the internet that can be printed on any printer, on the photographer's choice of media. As a result, a photographer can afford, using this design, to produce a series of domes of various sizes and materials, and LED ring lights of various sizes and color temperatures, depending on the need.

Museum lighting for golden artifacts, with low correlated color temperature, high color uniformity and high color rendering index, using diffusing color mixing of red, cyan, and white-light-emitting diodes

DEFF Research Database (Denmark)

Thorseth, Anders; Corell, Dennis Dan; Poulsen, Peter Behrensdorff

2012-01-01

at the Royal Danish Collection at Rosenborg Castle. Color mixing of red, cyan, and white LEDs was employed to achieve the spectral power distribution needed for the required CCT and a CRI above 90. Color uniformity is achieved by the use of a highly diffusing reflector. The system has shown energy saving above......Museum lighting presents challenges mainly due to the demand for precise color rendering and the damaging effects of radiation. Golden objects must normally be illuminated by the non-standard CCT of 2200 K. An LED system that conforms to these requirements has been developed and implemented...

Joint illumination and visible-light communication systems : data rates and extra power consumption

NARCIS (Netherlands)

Tsiatmas, Anagnostis; Willems, Frans; Linnartz, Jean-Paul; Baggen, C.P.M.J.; Bergmans, Jan

2015-01-01

Visible Light Communications (VLC) have been promoted as an energy-efficient Gb/s-technology for indoor settings, since VLC can be merged with the illumination functionality. As a result, Joint Illumination and visible-light Communication (JIC) systems are perceived as a green technology and the

Investigating the performance of reconstruction methods used in structured illumination microscopy as a function of the illumination pattern's modulation frequency

Science.gov (United States)

Shabani, H.; Sánchez-Ortiga, E.; Preza, C.

2016-03-01

Surpassing the resolution of optical microscopy defined by the Abbe diffraction limit, while simultaneously achieving optical sectioning, is a challenging problem particularly for live cell imaging of thick samples. Among a few developing techniques, structured illumination microscopy (SIM) addresses this challenge by imposing higher frequency information into the observable frequency band confined by the optical transfer function (OTF) of a conventional microscope either doubling the spatial resolution or filling the missing cone based on the spatial frequency of the pattern when the patterned illumination is two-dimensional. Standard reconstruction methods for SIM decompose the low and high frequency components from the recorded low-resolution images and then combine them to reach a high-resolution image. In contrast, model-based approaches rely on iterative optimization approaches to minimize the error between estimated and forward images. In this paper, we study the performance of both groups of methods by simulating fluorescence microscopy images from different type of objects (ranging from simulated two-point sources to extended objects). These simulations are used to investigate the methods' effectiveness on restoring objects with various types of power spectrum when modulation frequency of the patterned illumination is changing from zero to the incoherent cut-off frequency of the imaging system. Our results show that increasing the amount of imposed information by using a higher modulation frequency of the illumination pattern does not always yield a better restoration performance, which was found to be depended on the underlying object. Results from model-based restoration show performance improvement, quantified by an up to 62% drop in the mean square error compared to standard reconstruction, with increasing modulation frequency. However, we found cases for which results obtained with standard reconstruction methods do not always follow the same trend.

Modelling reverse characteristics of power LEDs with thermal phenomena taken into account

International Nuclear Information System (INIS)

Ptak, Przemysław; Górecki, Krzysztof

2016-01-01

This paper refers to modelling characteristics of power LEDs with a particular reference to thermal phenomena. Special attention is paid to modelling characteristics of the circuit protecting the considered device against the excessive value of the reverse voltage and to the description of the temperature influence on optical power. The network form of the worked out model is presented and some results of experimental verification of this model for the selected diodes operating at different cooling conditions are described. The very good agreement between the calculated and measured characteristics is obtained

Quality attributes of LED lighting. Current state-of-the-art , advantages, problem areas and potential for development - Final report; Qualitaetsmerkmale der LED-Beleuchtung. Aktueller Stand der Technik, Vorteile, Problempunkte und Entwicklungspotential - Schlussbericht

Energy Technology Data Exchange (ETDEWEB)

Gasser, S.

2009-09-15

radiation, instant start up, brilliant light). (iii) Street lighting: Today LED already is the best solution for a high number of applications (highly precise illumination of streets and walkways without diffused light, less light necessary thanks to better colour rendering). (author)

Optical enhancement of phosphor-converted wLEDs using glass beads

Science.gov (United States)

Güner, Tuğrul; Şentürk, Ufuk; Demir, Mustafa M.

2017-10-01

YAG:Ce3+ is a yellow-source compound commonly used in phosphor conversion layers for direct coating or remote phosphor configurations in LED illumination. This material, however, suffers from a high correlated color temperature, and low color-rendering index due to its deficiency in the red spectrum. In this study, glass beads (GB) with an average particle diameter of 10 μm were introduced to the conversion layer of a YAG:Ce3+ particulate-filled polydimethylsiloxane matrix composite structure and found to improve the optical features of the resulting composite.

Estimation of crosstalk in LED fNIRS by photon propagation Monte Carlo simulation

Science.gov (United States)

Iwano, Takayuki; Umeyama, Shinji

2015-12-01

fNIRS (functional near-Infrared spectroscopy) can measure brain activity non-invasively and has advantages such as low cost and portability. While the conventional fNIRS has used laser light, LED light fNIRS is recently becoming common in use. Using LED for fNIRS, equipment can be more inexpensive and more portable. LED light, however, has a wider illumination spectrum than laser light, which may change crosstalk between the calculated concentration change of oxygenated and deoxygenated hemoglobins. The crosstalk is caused by difference in light path length in the head tissues depending on wavelengths used. We conducted Monte Carlo simulations of photon propagation in the tissue layers of head (scalp, skull, CSF, gray matter, and white matter) to estimate the light path length in each layers. Based on the estimated path lengths, the crosstalk in fNIRS using LED light was calculated. Our results showed that LED light more increases the crosstalk than laser light does when certain combinations of wavelengths were adopted. Even in such cases, the crosstalk increased by using LED light can be effectively suppressed by replacing the value of extinction coefficients used in the hemoglobin calculation to their weighted average over illumination spectrum.

Predicting Ground Illuminance

Science.gov (United States)

Lesniak, Michael V.; Tregoning, Brett D.; Hitchens, Alexandra E.

2015-01-01

Our Sun outputs 3.85 x 1026 W of radiation, of which roughly 37% is in the visible band. It is directly responsible for nearly all natural illuminance experienced on Earth's surface, either in the form of direct/refracted sunlight or in reflected light bouncing off the surfaces and/or atmospheres of our Moon and the visible planets. Ground illuminance, defined as the amount of visible light intercepting a unit area of surface (from all incident angles), varies over 7 orders of magnitude from day to night. It is highly dependent on well-modeled factors such as the relative positions of the Sun, Earth, and Moon. It is also dependent on less predictable factors such as local atmospheric conditions and weather.Several models have been proposed to predict ground illuminance, including Brown (1952) and Shapiro (1982, 1987). The Brown model is a set of empirical data collected from observation points around the world that has been reduced to a smooth fit of illuminance against a single variable, solar altitude. It provides limited applicability to the Moon and for cloudy conditions via multiplicative reduction factors. The Shapiro model is a theoretical model that treats the atmosphere as a three layer system of light reflectance and transmittance. It has different sets of reflectance and transmittance coefficients for various cloud types.In this paper we compare the models' predictions to ground illuminance data from an observing run at the White Sands missile range (data was obtained from the United Kingdom's Meteorology Office). Continuous illuminance readings were recorded under various cloud conditions, during both daytime and nighttime hours. We find that under clear skies, the Shapiro model tends to better fit the observations during daytime hours with typical discrepancies under 10%. Under cloudy skies, both models tend to poorly predict ground illuminance. However, the Shapiro model, with typical average daytime discrepancies of 25% or less in many cases

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

Investigating Enhancement Mode Gallium Nitride Power FETs in High Voltage, High Frequency Soft Switching Converters

DEFF Research Database (Denmark)

Nour, Yasser; Knott, Arnold; Jørgensen, Ivan Harald Holger

2016-01-01

An increased attention has been detected to develop smaller and lighter high voltage power converters in the range of 50V to 400V domain. The main applications for these converters are mainly focused for Power over Ethernet (PoE), LED lighting and AC adapters. This work will discuss a study...

CALCULATION OF OPERATING PARAMETERS OF HIGH-VOLTAGE POWER TAKE-OFF SYSTEM FOR THE PHOTOVOLTAIC FACILITY

Directory of Open Access Journals (Sweden)

R.V. Zaitsev

2016-09-01

Full Text Available Purpose. To ensure maximum production of electric power by photovoltaic vacilities, in addition to using highly efficient photovoltaic modules equipped with solar radiation concentrators must use a highly effective power take-off system. This paper is inscribed to solving the problem of a highly efficient and economic power take-off system development. Methodology. To solving the problem, we implemented three stages. On the first stage examines the dependence of electrical power from the intensity of the incident solar radiation. Based on this, the second stage is calculated the DC-DC converter resonant circuit and its working parameters, and developed circuit diagram of DC-DC converter. On the third stage, we carry out an analysis of power take-off system with step up DC-DC converter working. Results. In this paper, we carry out the analysis of working efficiency for photovoltaic facility power take-off system with step-up boost converter. The result of such analysis show that the efficiency of such system in a wide range of photovoltaic energy module illumination power is at 0.92, whereas the efficiency of classic power take-off systems does not exceed 0.70. Achieved results allow designing a circuit scheme of a controlled bridge resonant step-up converter with digital control. Proposed scheme will ensure reliable operation, fast and accurate location point of maximum power and conversion efficiency up to 0.96. Originality. Novelty of proposed power take-off system solution constitute in implementation of circuit with DC-DC converters, which as it shown by results of carrying out modeling is the most effective. Practical value. Practical implementation of proposed power take-off system design will allow reducing losses in connective wires and increasing the efficiency of such a system up to 92.5% in wide range of photovoltaic energy modules illumination.

Fibre illumination system

DEFF Research Database (Denmark)

2012-01-01

Source: EP2426402A The invention relates to a fibre illumination module and system for the collection and delivery of daylight for illumination purposes. The fibre illumination module comprises a plurality of collector elements, each collector element comprising an input fibre having a first end......-directional arrangement. The fibre illumination system comprises a fibre illumination module of the above-mentioned type. By the invention, daylight may be exploited for the illumination of remote interior spaces of buildings in order to save energy, and improve the well-being of users in both housing and working...

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.

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

Effect of illumination on photoluminescence properties of porous silicon

International Nuclear Information System (INIS)

Naddaf, M.; Hamadeh, H.

2008-11-01

Porous silicon (PS) layers were formed by photo-electrochemical etching of both p-type and n-type single crystal wafers in HF based solution. During the etching process, the silicon wafer was illuminated by a halogen lamp light guided by an optical fiber through a monochromator or diode lasers at different power density and wavelengths (480,533,580 and 635 nm). The optical and structural properties of the prepared PS samples have been investigated by using temperature dependent photoluminescence (PL) spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, contact angle (CA) measurements, optical microscope and atomic force microscope (AFM). Beside the strong red-yellow PL band, a blue PL band has been observed only in the PS samples formed under the illumination with low power and short wavelengths (480-580 nm) light. In the near infrared (IR) spectral range, a new PL band at 850 nm was observed in p-type PS samples, which prepared under darkness or illumination with 635 nm of low power light. Temperature dependent PL measurements showed that, in contrast to the main IR PL band at around 1100 nm, the intensity of this new band increases on increasing the temperature. These changes in the PL properties was correlated with the illumination induced-structural and morphological modifications in the PS skeleton. In particular, the FTIR analysis showed that the chemical groups and bonds constituting the PS skeleton, such as, SiH, SiO bonds and silanol SiOH group play key role in deciding the PL emission intensity and blue shift. The study proved that the illumination parameters during the photo-electrochemical etching process can be utilized for tailoring a porous layer with novel optical and structural properties. (Authors)

Effect of illumination on photoluminescence properties of porous silicon

International Nuclear Information System (INIS)

Naddaf, M.; Hamadeh, H.

2009-01-01

Porous silicon (PS) layers were formed by photo-electrochemical etching of both p-type and n-type single crystal wafers in HF based solution. During the etching process, the silicon wafer was illuminated by a halogen lamp light guided by an optical fiber through a monochromator or diode lasers at different power density and wavelengths (480,533,580 and 635 nm). The optical and structural properties of the prepared PS samples have been investigated by using temperature dependent photoluminescence (PL) spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, contact angle (CA) measurements, optical microscope and atomic force microscope (AFM). Beside the strong red-yellow PL band, a blue PL band has been observed only in the PS samples formed under the illumination with low power and short wavelengths (480-580 nm) light. In the near infrared (IR) spectral range, a new PL band at 850 nm was observed in p-type PS samples, which prepared under darkness or illumination with 635 nm of low power light. Temperature dependent PL measurements showed that, in contrast to the main IR PL band at around 1100 nm, the intensity of this new band increases on increasing the temperature. These changes in the PL properties was correlated with the illumination induced-structural and morphological modifications in the PS skeleton. In particular, the FTIR analysis showed that the chemical groups and bonds constituting the PS skeleton, such as, SiH, SiO bonds and silanol SiOH group play key role in deciding the PL emission intensity and blue shift. The study proved that the illumination parameters during the photo-electrochemical etching process can be utilized for tailoring a porous layer with novel optical and structural properties. (Authors)

Multiobjective generalized extremal optimization algorithm for simulation of daylight illuminants

Science.gov (United States)

Kumar, Srividya Ravindra; Kurian, Ciji Pearl; Gomes-Borges, Marcos Eduardo

2017-10-01

Daylight illuminants are widely used as references for color quality testing and optical vision testing applications. Presently used daylight simulators make use of fluorescent bulbs that are not tunable and occupy more space inside the quality testing chambers. By designing a spectrally tunable LED light source with an optimal number of LEDs, cost, space, and energy can be saved. This paper describes an application of the generalized extremal optimization (GEO) algorithm for selection of the appropriate quantity and quality of LEDs that compose the light source. The multiobjective approach of this algorithm tries to get the best spectral simulation with minimum fitness error toward the target spectrum, correlated color temperature (CCT) the same as the target spectrum, high color rendering index (CRI), and luminous flux as required for testing applications. GEO is a global search algorithm based on phenomena of natural evolution and is especially designed to be used in complex optimization problems. Several simulations have been conducted to validate the performance of the algorithm. The methodology applied to model the LEDs, together with the theoretical basis for CCT and CRI calculation, is presented in this paper. A comparative result analysis of M-GEO evolutionary algorithm with the Levenberg-Marquardt conventional deterministic algorithm is also presented.

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

Application of a Compact High-Definition Exoscope for Illumination and Magnification in High-Precision Surgical Procedures.

Science.gov (United States)

Krishnan, Kartik G; Schöller, Karsten; Uhl, Eberhard

2017-01-01

The basic necessities for surgical procedures are illumination, exposure, and magnification. These have undergone transformation in par with technology. One of the recent developments is the compact magnifying exoscope system. In this report, we describe the application of this system for surgical operations and discuss its advantages and pitfalls. We used the ViTOM exoscope mounted on the mechanical holding arm. The following surgical procedures were conducted: lumbar and cervical spinal canal decompression (n = 5); laminotomy and removal of lumbar migrated disk herniations (n = 4); anterior cervical diskectomy and fusion (n = 1); removal of intraneural schwannomas (n = 2); removal of an acute cerebellar hemorrhage (n = 1); removal of a parafalcine atypical cerebral hematoma caused by a dural arteriovenous fistula (n = 1); and microsutures and anastomoses of a nerve (n = 1), an artery (n = 1), and veins (n = 2). The exoscope offered excellent, magnified, and brilliantly illuminated high-definition images of the surgical field. All surgical operations were successfully completed. The main disadvantage was the adjustment and refocusing using the mechanical holding arm. The time required for the surgical operation under the exoscope was slightly longer than the times required for a similar procedure performed using an operating microscope. The magnifying exoscope is an effective and nonbulky tool for surgical procedures. In visualization around the corners, the exoscope has better potential than a microscope. With technical and technologic modifications, the exoscope might become the next generation in illumination, visualization, exposure, and magnification for high-precision surgical procedures. Copyright © 2016 Elsevier Inc. All rights reserved.

Assessing resolution in live cell structured illumination microscopy

Science.gov (United States)

Pospíšil, Jakub; Fliegel, Karel; Klíma, Miloš

2017-12-01

Structured Illumination Microscopy (SIM) is a powerful super-resolution technique, which is able to enhance the resolution of optical microscope beyond the Abbe diffraction limit. In the last decade, numerous SIM methods that achieve the resolution of 100 nm in the lateral dimension have been developed. The SIM setups with new high-speed cameras and illumination pattern generators allow rapid acquisition of the live specimen. Therefore, SIM is widely used for investigation of the live structures in molecular and live cell biology. Quantitative evaluation of resolution enhancement in a real sample is essential to describe the efficiency of super-resolution microscopy technique. However, measuring the resolution of a live cell sample is a challenging task. Based on our experimental findings, the widely used Fourier ring correlation (FRC) method does not seem to be well suited for measuring the resolution of SIM live cell video sequences. Therefore, the resolution assessing methods based on Fourier spectrum analysis are often used. We introduce a measure based on circular average power spectral density (PSDca) estimated from a single SIM image (one video frame). PSDca describes the distribution of the power of a signal with respect to its spatial frequency. Spatial resolution corresponds to the cut-off frequency in Fourier space. In order to estimate the cut-off frequency from a noisy signal, we use a spectral subtraction method for noise suppression. In the future, this resolution assessment approach might prove useful also for single-molecule localization microscopy (SMLM) live cell imaging.

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.

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.

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.

Photocatalytic antibacterial activity of copper-based nanoparticles under visible light illumination

Science.gov (United States)

Wu, Zong-Yan; Abdullah, Hairus; Kuo, Dong-Hau

2018-04-01

Copper oxide and sulfide nanoparticles after annealing treatment at 400 °Chave been characterized and tested for their bactericidal properties toward Staphylococcus aureus and Escherichia coli under the dark and LED light illuminated conditions. It was found that the nanoparticles with the formation of CuS/Cu2S/CuO nanoheterostructuresexhibited a great capability of killing Staphylococcus aureus and Escherichia coli with or without light illumination. The antibacterial activity of the nanoparticles was demonstrated and simply observed with colony counting method. A mechanism of the antibacterial behaviour had been proposed and elucidated in this work.

Selective joining technique for high power electronics; Selektive Verbindungstechnik fuer die Leistungselektronik

Energy Technology Data Exchange (ETDEWEB)

Fehrenbach, Manfred [EUTECT GmbH, Dusslingen (Germany)

2012-11-01

Stringent demands are placed on the quality, reliability and workmanship of electronic components in modern automotive electronics, high-performance LEDs (HLEDs) and regenerative electrical power generation. Automated selective integrated circuit packaging processes are increasingly becoming irreplaceable. Integrated circuit packing can be performed by means of mini-wave, laser, iron or hot-bar soldering, as well as the micro welding process. In addition to the modification of existing technologies, this also requires new joining technologies and test strategies for quality assurance. Interdisciplinary expertise with regard to process technology and system function is therefore essential for sound process assurance, maximum effectiveness and added value in the joining process. This article addresses the processing of THT electronics assemblies in the areas of printed-circuit boards, LEDs, flex foils, leadframes, hybrids and special types. Using high-power LED processes as examples, integrated circuit packaging is described for IMS, Osram Philips, Samsung and further LED designs, as well as printed-circuit board, flex-foil and jumper connections to the associated LED heat sinks. (orig.)

The Design of Nanosecond Fast-switch Pulsed High Voltage Power Supply Based on Solid-state

International Nuclear Information System (INIS)

Chen Wenguang; Chen Wei; Rao Yihua

2009-01-01

The high voltage pulsed power supply is applied in the experiment of the nuclear science widely. It main consist of DC high-voltage power supply (HVPS) and pulse modulator. The high-frequency series-resonant inverter technology and IGBT series technology are used to design the HVPS and the modulator, respectively. The main circuit, control circuit, high voltage transformer and solid-state switch are illuminated in the paper. The apparatus can operate at a maximum output voltage of 6 kilovolt, which can be modulated single pulse and also be modulated by series pulse. A prototype is fabricated and tested, experimental results show that the pulsed power supply is well-designed and rising edge time to meet the nsclass; it can achieve the requirement of rapid modulation. (authors)

Pulsed power drivers for ICF and high energy density physics

International Nuclear Information System (INIS)

Ramirez, J.J.; Matzen, M.K.; McDaniel, D.H.

1995-01-01

Nanosecond Pulsed Power Science and Technology has its origins in the 1960s and over the past decade has matured into a flexible and robust discipline capable of addressing key physics issues of importance to ICF and high Energy Density Physics. The major leverage provided by pulsed power is its ability to generate and deliver high energy and high power at low cost and high efficiency. A low-cost, high-efficiency driver is important because of the very large capital investment required for multi-megajoule ignition-class systems. High efficiency is of additional importance for a commercially viable inertial fusion energy option. Nanosecond pulsed power has been aggressively and successfully developed at Sandia over the past twenty years. This effort has led to the development of unique multi-purpose facilities supported by highly capable diagnostic, calculational and analytic capabilities. The Sandia Particle-beam Fusion Program has evolved as part of an integrated national ICF Program. It applies the low-cost, high-efficiency leverage provided by nanosecond pulsed power systems to the longer-term goals of the national program, i.e., the Laboratory Microfusion Facility and Inertial Fusion Energy. A separate effort has led to the application of nanosecond pulsed power to the generation of intense, high-energy laboratory x-ray sources for application to x-ray laser and radiation effects science research. Saturn is the most powerful of these sources to date. It generates ∼500 kilojoules of x-rays from a magnetically driven implosion (Z-pinch). This paper describes results of x-ray physics experiments performed on Saturn, plans for a new Z-pinch drive capability for PBFA-II, and a design concept for the proposed ∼15 MJ Jupiter facility. The opportunities for ICF-relevant research using these facilities will also be discussed

Optimized optical wireless channel for indoor and intra-vehicle communications: power distribution and SNR analysis

Science.gov (United States)

Shaaban, Rana; Faruque, Saleh

2018-01-01

Light emitting diodes - LEDs are modernizing the indoor illumination and replacing current incandescent and fluorescent lamps rapidly. LEDs have multiple advantages such as extremely high energy efficient, longer lifespan, and lower heat generation. Due to the ability to switch to different light intensity at a very fast rate, LED has given rise to a unique communication technology (visible light communication - VLC) used for high speed data transmission. By studying various kinds of commonly used VLC channel analysis: diffuse and line of sight channels, we presented a simply improved indoor and intra-vehicle visible light communication transmission model. Employing optical wireless communications within the vehicle, not only enhance user mobility, but also alleviate radio frequency interference, and increase efficiency by lowering the complexity of copper cabling. Moreover, a solution to eliminate ambient noise caused by environmental conditions is examined by using optical differential receiver. The simulation results show the improved received power distribution and signal to noise ratio - SNR.

Optical Frequency Optimization of a High Intensity Laser Power Beaming System Utilizing VMJ Photovoltaic Cells

Science.gov (United States)

Raible, Daniel E.; Dinca, Dragos; Nayfeh, Taysir H.

2012-01-01

An effective form of wireless power transmission (WPT) has been developed to enable extended mission durations, increased coverage and added capabilities for both space and terrestrial applications that may benefit from optically delivered electrical energy. The high intensity laser power beaming (HILPB) system enables long range optical 'refueling" of electric platforms such as micro unmanned aerial vehicles (MUAV), airships, robotic exploration missions and spacecraft platforms. To further advance the HILPB technology, the focus of this investigation is to determine the optimal laser wavelength to be used with the HILPB receiver, which utilizes vertical multi-junction (VMJ) photovoltaic cells. Frequency optimization of the laser system is necessary in order to maximize the conversion efficiency at continuous high intensities, and thus increase the delivered power density of the HILPB system. Initial spectral characterizations of the device performed at the NASA Glenn Research Center (GRC) indicate the approximate range of peak optical-to-electrical conversion efficiencies, but these data sets represent transient conditions under lower levels of illumination. Extending these results to high levels of steady state illumination, with attention given to the compatibility of available commercial off-the-shelf semiconductor laser sources and atmospheric transmission constraints is the primary focus of this paper. Experimental hardware results utilizing high power continuous wave (CW) semiconductor lasers at four different operational frequencies near the indicated band gap of the photovoltaic VMJ cells are presented and discussed. In addition, the highest receiver power density achieved to date is demonstrated using a single photovoltaic VMJ cell, which provided an exceptionally high electrical output of 13.6 W/sq cm at an optical-to-electrical conversion efficiency of 24 percent. These results are very promising and scalable, as a potential 1.0 sq m HILPB receiver of

Illuminating Everyday Performances of Privilege and Oppression

Science.gov (United States)

Heuman, Amy N.

2018-01-01

Courses: Intercultural Communication, Interracial Communication, Gender and Communication, Introduction to Communication Course (within a unit on culture), and any courses encouraging critical analyses of power. Objectives: This activity will: illuminate the ways in which everyday performances of privilege and resulting oppressions connect with…

Automated system for the determination of patterns of high-intensity LEDs

International Nuclear Information System (INIS)

Baly, L.; Bolaño, L.; Arteche, R.; Broco, Y.; Quesada, I.; Rodríguez, E.

2008-01-01

Determination of high-intensity LEDs lighting patterns is an important step for the simulation and planning of arrays of these devices configurations. Currently there are systems based on CCD cameras able to efficiently solve this problem, however the high cost of these is a limiting factor for use. Another limitation of CCD cameras, is that they are designed for light levels much lower than those produced by a high-intensity LED. In this paper we present an automated system for the determination of the intensity of LEDs based on the scan point to point patterns. The results of the analysis of a type of LED based on arrays of bars with built-in optical system is presented.

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.

Illuminance-based slat angle selection model for automated control of split blinds

Energy Technology Data Exchange (ETDEWEB)

Hu, Jia; Olbina, Svetlana [Rinker School of Building Construction, University of Florida, Gainesville, FL 32611-5703 (United States)

2011-03-15

Venetian blinds play an important role in controlling daylight in buildings. Automated blinds overcome some limitations of manual blinds; however, the existing automated systems mainly control the direct solar radiation and glare and cannot be used for controlling innovative blind systems such as split blinds. This research developed an Illuminance-based Slat Angle Selection (ISAS) model that predicts the optimum slat angles of split blinds to achieve the designed indoor illuminance. The model was constructed based on a series of multi-layer feed-forward artificial neural networks (ANNs). The illuminance values at the sensor points used to develop the ANNs were obtained by the software EnergyPlus trademark. The weather determinants (such as horizontal illuminance and sun angles) were used as the input variables for the ANNs. The illuminance level at a sensor point was the output variable for the ANNs. The ISAS model was validated by evaluating the errors in the calculation of the: 1) illuminance and 2) optimum slat angles. The validation results showed that the power of the ISAS model to predict illuminance was 94.7% while its power to calculate the optimum slat angles was 98.5%. For about 90% of time in the year, the illuminance percentage errors were less than 10%, and the percentage errors in calculating the optimum slat angles were less than 5%. This research offers a new approach for the automated control of split blinds and a guide for future research to utilize the adaptive nature of ANNs to develop a more practical and applicable blind control system. (author)

Establishment Of Illumination System For Investigation Of Monochromatic Lights Combination Effects On In Vitro Plant Growth

International Nuclear Information System (INIS)

Le Tien Thanh; Le Ngoc Trieu; Nguyen Tuong Mien; Huynh Thi Trung; Phan Quoc Minh

2014-01-01

Super blue and red light LEDs and other electric, electronic components are used to design and establish 11 independent illumination systems, each system can arbitrarily control to operate at 55 molarities of illumination which are different from together in monochromatic lights combination and total illumination intensity based on the microcontrollers. Programs for loading to microcontrollers were created to base on theoretical calculation and experimental correction. The illumination cycles can be controlled by setting the timer. These 11 systems and another fluorescent light illumination were used to execute the experiment for investigation the effects of monochromatic lights combination on in vitro shoot proliferation stage in Chrysanthemum and Phalaenopsis orchid. Results from this experiment showed that illumination intensity of 400 lux is suitable for chrysanthemum, 750 lux is suitable for Phalaenopsis orchid and rate of 70% red light-30% blue light are suitable for both kinds of these plants. (author)

Surface color perception under two illuminants: the second illuminant reduces color constancy

Science.gov (United States)

Yang, Joong Nam; Shevell, Steven K.

2003-01-01

This study investigates color perception in a scene with two different illuminants. The two illuminants, in opposite corners, simultaneously shine on a (simulated) scene with an opaque dividing wall, which controls how much of the scene is illuminated by each source. In the first experiment, the height of the dividing wall was varied. This changed the amount of each illuminant reaching objects on the opposite side of the wall. Results showed that the degree of color constancy decreased when a region on one side of the wall had cues to both illuminants, suggesting that cues from the second illuminant are detrimental to color constancy. In a later experiment, color constancy was found to improve when the specular highlight cues from the second illuminant were altered to be consistent with the first illuminant. This corroborates the influence of specular highlights in surface color perception, and suggests that the reduced color constancy in the first experiment is due to the inconsistent, though physically correct, cues from the two illuminants.

Optical Estimation of the 3D Shape of a Solar Illuminated, Reflecting Satellite Surface

Science.gov (United States)

Antolin, J.; Yu, Z.; Prasad, S.

2016-09-01

The spatial distribution of the polarized component of the power reflected by a macroscopically smooth but microscopically roughened curved surface under highly directional illumination, as characterized by an appropriate bi-directional reflectance distribution function (BRDF), carries information about the three-dimensional (3D) shape of the surface. This information can be exploited to recover the surface shape locally under rather general conditions whenever power reflectance data for at least two different illumination or observation directions can be obtained. We present here two different parametric approaches for surface reconstruction, amounting to the recovery of the surface parameters that are either the global parameters of the family to which the surface is known a priori to belong or the coefficients of a low-order polynomial that can be employed to characterize a smoothly varying surface locally over the observed patch.

Distributed illumination control with local sensing and actuation in networked lighting systems

NARCIS (Netherlands)

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

2013-01-01

We consider the problem of illumination control in a networked lighting system wherein luminaires have local sensing and actuation capabilities. Each luminaire (i) consists of a light emitting diode (LED) based light source dimmable by a local controller, (ii) is actuated based on sensing

[Hygienic and environmental problems of energy-saving illumination in urbanization of Crimea].

Science.gov (United States)

Deynego, V N; Elizarov, V B; Kaptsov, V A

The article considers the problems offloodlights pollution in the territory of Crimea due to the work of illumination led equipment of the key elements of the international transport artery "China-Europe". There was performed a qualitative assessment of characteristics of led floodlights pollution on the example of the sea surface of the transport crossing through the Kerch Strait. Ichthyologists and oceanographers were shown to estimate the amount of phytoplankton biomass based on sunlight illumination. The excess dose of blue light in the spectrum of led lighting was established to have an impact on phytoplankton greater than solar and lunar light, creating preconditions for the increase of biological mass of phytoplankton and consequently to the formation of the "stern stock". Arising from additional phytoplankton biomass can significantly influence on the schedule offish migration in waters of the Kerch Strait, the biomass of mosquitoes and midges, which are prey for amphibians and birds. The decline of the both light pollution and its negative impact on fauna andflora requires the development of semiconductor sources of white light with a biologically adequate spectrum in the framework of the "Lighting of the lighting equipment of Crimea".

Analysis of image plane's Illumination in Image-forming System

International Nuclear Information System (INIS)

Duan Lihua; Zeng Yan'an; Zhang Nanyangsheng; Wang Zhiguo; Yin Shiliang

2011-01-01

In the detection of optical radiation, the detecting accuracy is affected by optic power distribution of the detector's surface to a large extent. In addition, in the image-forming system, the quality of the image is greatly determined by the uniformity of the image's illumination distribution. However, in the practical optical system, affected by the factors such as field of view, false light and off axis and so on, the distribution of the image's illumination tends to be non uniform, so it is necessary to discuss the image plane's illumination in image-forming systems. In order to analyze the characteristics of the image-forming system at a full range, on the basis of photometry, the formulas to calculate the illumination of the imaging plane have been summarized by the numbers. Moreover, the relationship between the horizontal offset of the light source and the illumination of the image has been discussed in detail. After that, the influence of some key factors such as aperture angle, off-axis distance and horizontal offset on illumination of the image has been brought forward. Through numerical simulation, various theoretical curves of those key factors have been given. The results of the numerical simulation show that it is recommended to aggrandize the diameter of the exit pupil to increase the illumination of the image. The angle of view plays a negative role in the illumination distribution of the image, that is, the uniformity of the illumination distribution can be enhanced by compressing the angle of view. Lastly, it is proved that telecentric optical design is an effective way to advance the uniformity of the illumination distribution.

Low power wide spectrum optical transmitter using avalanche mode LEDs in SOI CMOS technology

NARCIS (Netherlands)

Agarwal, V.; Dutta, S; Annema, AJ; Hueting, RJE; Steeneken, P.G.; Nauta, B

2017-01-01

This paper presents a low power monolithically integrated optical transmitter with avalanche mode light emitting diodes in a 140 nm silicon-on-insulator CMOS technology. Avalanche mode LEDs in silicon exhibit wide-spectrum electroluminescence (400 nm < λ < 850 nm), which has a significant

Smartphone-Driven Low-Power Light-Emitting Device

Directory of Open Access Journals (Sweden)

Hea-Ja An

2017-01-01

Full Text Available Low-level light (laser therapy (LLLT has been widely researched in the recent past. Existing LLLT studies were performed based on laser. Recently, studies using LED have increased. This study presents a smartphone-driven low-power light-emitting device for use in colour therapy as an alternative medicine. The device consists of a control unit and a colour probe. The device is powered by and communicates with a smartphone using USB On-The-Go (OTG technology. The control unit controls emitting time and intensity of illumination with the configuration value of a smartphone application. Intensity is controlled by pulse width modulation (PWM without feedback. A calibration is performed to resolve a drawback of no feedback. To calibrate, intensity is measured in every 10 percent PWM output. PWM value is linearly calibrated to obtain accurate intensity. The device can control the intensity of illumination, and so, it can find application in varied scenarios.

3D-Printed, All-in-One Evaporator for High-Efficiency Solar Steam Generation under 1 Sun Illumination.

Science.gov (United States)

Li, Yiju; Gao, Tingting; Yang, Zhi; Chen, Chaoji; Luo, Wei; Song, Jianwei; Hitz, Emily; Jia, Chao; Zhou, Yubing; Liu, Boyang; Yang, Bao; Hu, Liangbing

2017-07-01

Using solar energy to generate steam is a clean and sustainable approach to addressing the issue of water shortage. The current challenge for solar steam generation is to develop easy-to-manufacture and scalable methods which can convert solar irradiation into exploitable thermal energy with high efficiency. Although various material and structure designs have been reported, high efficiency in solar steam generation usually can be achieved only at concentrated solar illumination. For the first time, 3D printing to construct an all-in-one evaporator with a concave structure for high-efficiency solar steam generation under 1 sun illumination is used. The solar-steam-generation device has a high porosity (97.3%) and efficient broadband solar absorption (>97%). The 3D-printed porous evaporator with intrinsic low thermal conductivity enables heat localization and effectively alleviates thermal dissipation to the bulk water. As a result, the 3D-printed evaporator has a high solar steam efficiency of 85.6% under 1 sun illumination (1 kW m -2 ), which is among the best compared with other reported evaporators. The all-in-one structure design using the advanced 3D printing fabrication technique offers a new approach to solar energy harvesting for high-efficiency steam generation. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Efficiency limits of laser power converters for optical power transfer applications

International Nuclear Information System (INIS)

Mukherjee, J; Jarvis, S; Sweeney, S J; Perren, M

2013-01-01

We have developed III–V-based high-efficiency laser power converters (LPCs), optimized specifically for converting monochromatic laser radiation at the eye-safe wavelength of 1.55 µm into electrical power. The applications of these photovoltaic cells include high-efficiency space-based and terrestrial laser power transfer and subsequent conversion to electrical power. In addition, these cells also find use in fibre-optic power delivery, remote powering of subcutaneous equipment and several other optical power delivery applications. The LPC design is based on lattice-matched InGaAsP/InP and incorporates elements for photon-recycling and contact design for efficient carrier extraction. Here we compare results from electro-optical design simulations with experimental results from prototype devices studied both in the lab and in field tests. We analyse wavelength and temperature dependence of the LPC characteristics. An experimental conversion efficiency of 44.6% [±1%] is obtained from the prototype devices under monochromatic illumination at 1.55 µm (illumination power density of 1 kW m −2 ) at room temperature. Further design optimization of our LPC is expected to scale the efficiency beyond 50% at 1 kW m −2 . (paper)

Efficiency limits of laser power converters for optical power transfer applications

Science.gov (United States)

Mukherjee, J.; Jarvis, S.; Perren, M.; Sweeney, S. J.

2013-07-01

We have developed III-V-based high-efficiency laser power converters (LPCs), optimized specifically for converting monochromatic laser radiation at the eye-safe wavelength of 1.55 µm into electrical power. The applications of these photovoltaic cells include high-efficiency space-based and terrestrial laser power transfer and subsequent conversion to electrical power. In addition, these cells also find use in fibre-optic power delivery, remote powering of subcutaneous equipment and several other optical power delivery applications. The LPC design is based on lattice-matched InGaAsP/InP and incorporates elements for photon-recycling and contact design for efficient carrier extraction. Here we compare results from electro-optical design simulations with experimental results from prototype devices studied both in the lab and in field tests. We analyse wavelength and temperature dependence of the LPC characteristics. An experimental conversion efficiency of 44.6% [±1%] is obtained from the prototype devices under monochromatic illumination at 1.55 µm (illumination power density of 1 kW m-2) at room temperature. Further design optimization of our LPC is expected to scale the efficiency beyond 50% at 1 kW m-2.

Assessment of LED Technology in Ornamental Post-Top Luminaires (Host Site: Sacramento, CA)

Energy Technology Data Exchange (ETDEWEB)

Tuenge, Jason R.

2011-12-01

The DOE Municipal Solid-State Street Lighting Consortium has evaluated four different LED replacements for existing ornamental post-top street lights in Sacramento, California. The project team was composed of the City and its consultant, PNNL (representing the Consortium), and the Sacramento Municipal Utility District. Product selection was finalized in March 2011, yielding one complete luminaire replacement and three lamp-ballast retrofit kits. Computer simulations, field measurements, and laboratory testing were performed to compare the performance and cost-effectiveness of the LED products relative to the existing luminaire with 100 W high-pressure sodium lamp. After it was confirmed the LED products were not equivalent to HPS in terms of initial photopic illumination, the following parameters were scaled proportionally to enable equitable (albeit hypothetical) comparisons: light output, input wattage, and pricing. Four replacement scenarios were considered for each LED product, incorporating new IES guidance for mesopic multipliers and lumen maintenance extrapolation, but life cycle analysis indicated cost effectiveness was also unacceptable. Although LED efficacy and pricing continue to improve, this project serves as a timely and objective notice that LED technology may not be quite ready yet for such applications.

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.

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)

Content adaptive illumination for Fourier ptychography.

Science.gov (United States)

Bian, Liheng; Suo, Jinli; Situ, Guohai; Zheng, Guoan; Chen, Feng; Dai, Qionghai

2014-12-01

Fourier ptychography (FP) is a recently reported technique, for large field-of-view and high-resolution imaging. Specifically, FP captures a set of low-resolution images, under angularly varying illuminations, and stitches them together in the Fourier domain. One of FP's main disadvantages is its long capturing process, due to the requisite large number of incident illumination angles. In this Letter, utilizing the sparsity of natural images in the Fourier domain, we propose a highly efficient method, termed adaptive Fourier ptychography (AFP), which applies content adaptive illumination for FP, to capture the most informative parts of the scene's spatial spectrum. We validate the effectiveness and efficiency of the reported framework, with both simulated and real experiments. Results show that the proposed AFP could shorten the acquisition time of conventional FP, by around 30%-60%.

Illumination compensation in ground based hyperspectral imaging

Science.gov (United States)

Wendel, Alexander; Underwood, James

2017-07-01

Hyperspectral imaging has emerged as an important tool for analysing vegetation data in agricultural applications. Recently, low altitude and ground based hyperspectral imaging solutions have come to the fore, providing very high resolution data for mapping and studying large areas of crops in detail. However, these platforms introduce a unique set of challenges that need to be overcome to ensure consistent, accurate and timely acquisition of data. One particular problem is dealing with changes in environmental illumination while operating with natural light under cloud cover, which can have considerable effects on spectral shape. In the past this has been commonly achieved by imaging known reference targets at the time of data acquisition, direct measurement of irradiance, or atmospheric modelling. While capturing a reference panel continuously or very frequently allows accurate compensation for illumination changes, this is often not practical with ground based platforms, and impossible in aerial applications. This paper examines the use of an autonomous unmanned ground vehicle (UGV) to gather high resolution hyperspectral imaging data of crops under natural illumination. A process of illumination compensation is performed to extract the inherent reflectance properties of the crops, despite variable illumination. This work adapts a previously developed subspace model approach to reflectance and illumination recovery. Though tested on a ground vehicle in this paper, it is applicable to low altitude unmanned aerial hyperspectral imagery also. The method uses occasional observations of reference panel training data from within the same or other datasets, which enables a practical field protocol that minimises in-field manual labour. This paper tests the new approach, comparing it against traditional methods. Several illumination compensation protocols for high volume ground based data collection are presented based on the results. The findings in this paper are

Influence of interconnection on the long-term reliability of UV LED packages

Science.gov (United States)

Nieland, S.; Mitrenga, D.; Karolewski, D.; Brodersen, O.; Ortlepp, T.

2017-02-01

High power LEDs have conquered the mass market in recent years. Besides the main development focus to achieve higher productivity in the field of visible semiconductor LED processing, the wavelength range is further enhanced by active research and development in the direction of UVA / UVB / UVC. UVB and UVC LEDs are new and promising due to their numerous advantages. UV LEDs emit in a near range of one single emission peak with a width (FWHM) below 15 nm compared to conventional mercury discharge lamps and xenon sources, which show broad spectrums with many emission peaks over a wide range of wavelengths. Furthermore, the UV LED size is in the range of a few hundred microns and offers a high potential of significant system miniaturization. Of course, LED efficiency, lifetime and output power have to be increased [1]. Lifetime limiting issues of UVB/UVC-LED are the very high thermal stress in the chip resulting from the higher forward voltages (6-10 V @ 350 mA), the lower external quantum efficiency, below 10 % (most of the power disappears as heat), and the thermal resistance Rth of conventional LED packages being not able to dissipate these large amounts of heat for spreading. Beside the circuit boards and submounts which should have maximum thermal conductivity, the dimension of contacts as well as the interconnection of UV LED to the submount/package determinates the resolvable amount of heat [2]. In the paper different innovative interconnection techniques for UVC-LED systems will be discussed focused on the optimization of thermal conductivity in consideration of the assembly costs. Results on thermal simulation for the optimal contact dimensions and interconnections will be given. In addition, these theoretical results will be compared with results on electrical characterization as well as IR investigations on real UV LED packages in order to give recommendations for optimal UV LED assembly.

High-power pulsed lasers

International Nuclear Information System (INIS)

Holzrichter, J.F.

1980-01-01

The ideas that led to the successful construction and operation of large multibeam fusion lasers at the Lawrence Livermore Laboratory are reviewed. These lasers are based on the use of Nd:glass laser materials. However, most of the concepts are applicable to any laser being designed for fusion experimentation. This report is a summary of lectures given by the author at the 20th Scottish University Summer School in Physics, on Laser Plasma Interaction. This report includes basic concepts of the laser plasma system, a discussion of lasers that are useful for short-pulse, high-power operation, laser design constraints, optical diagnostics, and system organization

Investigation of acoustic resonances in high-power lamps

International Nuclear Information System (INIS)

Kettlitz, M; Zalach, J; Rarbach, J

2011-01-01

High-power, medium-pressure, mercury-containing lamps are used as UV sources for many industrial applications. Lamps investigated in this paper are driven with an electronic ballast with a non-sinusoidal current waveform at a fixed frequency of 20 kHz and a maximum power output of 35 kW. Instabilities can occur if the input power is reduced below 50%. The reason is identified as acoustic resonances in the lamp. Comparison of calculated and measured resonance frequencies shows a good agreement and explains the observed lamp behaviour. This has led to the development of a new ballast prototype which is able to avoid instabilities by changing the driving frequency dependent on the applied power.

Re-designing illumination level in printing working area

Science.gov (United States)

Wahyuni, D.; Tambunan, M.; Panjaitan, N.; Budiman, I.

2018-02-01

This research was conducted in four printing business in Medan city. The illumination level on the research object is very low around 30 Lux far below the required value of government regulation at 200 Lux. Poor lighting has an impact on the number of defective products that pass the inspection, so we need to improve the workspace lighting to improve the quality of work. The method of determining the measuring point follows SNI 16-7062-2004, and the measuring instrument used is 4 in 1 Environment Meter. The results show that almost all workspaces under study require improved lighting, because the light bulbs used are not able to meet the lighting needs. This research recommends improving the workspace lighting using LED (Light Emitting Diode) lights because it has high energy efficiency and relatively more lifetime compared to the existing lamp.

High-density optical data storage based on grey level recording in photobleaching polymers using two-photon excitation under ultrashort pulse and continuous wave illumination

International Nuclear Information System (INIS)

Ganic, D.; Day, D.; Gu, M.

1999-01-01

Full text: Two-photon excitation has been employed in three-dimensional optical data storage by many researchers in an attempt to increase the storage density of a given material. The probability of two-photon excitation is proportional to the squared intensity of the incident light; this effect produces excitation only within a small region of the focus spot. Another advantage of two-photon excitation is the use of infrared illumination, which results in the reduction of scattering and enables the recording of layers at a deep depth in a thick material. The storage density thus obtained using multi-layered bit optical recording can be as high as Tbit/cm 3 . To increase this storage density even further, grey level recording can be employed. This method utilises variable exposure times of a laser beam focused into a photobleaching sample. As a result, the bleached area possesses a certain pixel value which depends upon the exposure time; this can increase the storage density many times depending upon the number of grey levels used. Our experiment shows that it is possible to attain grey level recording using both ultrashort pulsed and continuous-wave illumination. Although continuous wave illumination requires an average power of approximately 2 orders of magnitude higher than that for ultrashort pulsed illumination, it is a preferred method of recording due to its relatively low system cost and compactness. Copyright (1999) Australian Optical Society

Scanless functional imaging of hippocampal networks using patterned two-photon illumination through GRIN lenses

KAUST Repository

Moretti, Claudio

2016-09-12

Patterned illumination through the phase modulation of light is increasingly recognized as a powerful tool to investigate biological tissues in combination with two-photon excitation and light-sensitive molecules. However, to date two-photon patterned illumination has only been coupled to traditional microscope objectives, thus limiting the applicability of these methods to superficial biological structures. Here, we show that phase modulation can be used to efficiently project complex two-photon light patterns, including arrays of points and large shapes, in the focal plane of graded index (GRIN) lenses. Moreover, using this approach in combination with the genetically encoded calcium indicator GCaMP6, we validate our system performing scanless functional imaging in rodent hippocampal networks in vivo ~1.2 mm below the brain surface. Our results open the way to the application of patterned illumination approaches to deep regions of highly scattering biological tissues, such as the mammalian brain.

Very High Frequency Galvanic Isolated Offline Power Supply

DEFF Research Database (Denmark)

Pedersen, Jeppe Arnsdorf

During the last decades many researchers have turned their attention to raising the operation frequency of power converters to the very high frequency (VHF) range going from 30 MHz to 300 MHz. Increasing the operating frequency of a power converter leads to smaller energy storing components...... inverters with a single combined rectifier. The converter designed to deliver 9 W to a 60 V LED load and is achieving an efficiency of 89.4% and a power density of 2.14 W3 . The development of this converter proof that offline VHF converter can be implemented with high efficiencies even for low power applications...... are described together with the possibility of using capacitors as the power galvanic isolation, both methods of creating galvanic isolation are implemented in converters. Regarding EMC a series of converters with different filter implementations are examined. The results from the conducted mea-surement from 150...

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.

Comparative analysis of high pressure sodium vapor lamps and mercury vapor lamp with the solid state (LED) in the public lighting systems; Analise comparativa das lampadas de vapor de sodio a alta pressao e de vapor de mercurio com a lampada a estado solido (LED) em sistemas de iluminacao publica

Energy Technology Data Exchange (ETDEWEB)

Damato, J.C.; Bueno, J.E.; Astorga, O.A.M. [Universidade Estadual Paulista (LESIP/UNESP), Guaratingueta, SP (Brazil). Lab. de Eficiencia Energetica em Sistemas de Iluminacao Publica; Ricciulli, D.L.S. [Universidade Estadual Paulista (DEE/UNESP), Guaratingueta, SP (Brazil). Dept. de Engenharia Eletrica

2009-07-01

The necessity of energy conservation in Brazilian electric sector, with the intention to diminish the resources of generation investments, has going to use of electric energy conservation programs, being most important PROCEL - a national program of electric conservation energy by ELETROBRAS, and inside this, a national program for public illumination and efficient traffic signaling - named 'Reluz'. This program looks for a more efficient implantation of public lighting systems, that requires the use of lamp technologies that present a greater value in a relation between lumen/watt relation and then beyond providing economy, due to low consumption of electric energy. Besides technologies that are appearing, the inclusion of LED lamps, which offers a great application potential, comes blunting as improvement alternative, being that the next public illumination parks will be able count on these lamps associates to the high-pressure sodium lamps and other types currently used. (author)

A signal normalization technique for illumination-based synchronization of 1,000-fps real-time vision sensors in dynamic scenes.

Science.gov (United States)

Hou, Lei; Kagami, Shingo; Hashimoto, Koichi

2010-01-01

To acquire images of dynamic scenes from multiple points of view simultaneously, the acquisition time of vision sensors should be synchronized. In this paper, an illumination-based synchronization derived from the phase-locked loop (PLL) mechanism based on the signal normalization method is proposed and evaluated. To eliminate the system dependency due to the amplitude fluctuation of the reference illumination, which may be caused by the moving objects or relative positional distance change between the light source and the observed objects, the fluctuant amplitude of the reference signal is normalized framely by the estimated maximum amplitude between the reference signal and its quadrature counterpart to generate a stable synchronization in highly dynamic scenes. Both simulated results and real world experimental results demonstrated successful synchronization result that 1,000-Hz frame rate vision sensors can be successfully synchronized to a LED illumination or its reflected light with satisfactory stability and only 28-μs jitters.

A Signal Normalization Technique for Illumination-Based Synchronization of 1,000-fps Real-Time Vision Sensors in Dynamic Scenes

Directory of Open Access Journals (Sweden)

Koichi Hashimoto

2010-09-01

Full Text Available To acquire images of dynamic scenes from multiple points of view simultaneously, the acquisition time of vision sensors should be synchronized. In this paper, an illumination-based synchronization derived from the phase-locked loop (PLL mechanism based on the signal normalization method is proposed and evaluated. To eliminate the system dependency due to the amplitude fluctuation of the reference illumination, which may be caused by the moving objects or relative positional distance change between the light source and the observed objects, the fluctuant amplitude of the reference signal is normalized framely by the estimated maximum amplitude between the reference signal and its quadrature counterpart to generate a stable synchronization in highly dynamic scenes. Both simulated results and real world experimental results demonstrated successful synchronization result that 1,000-Hz frame rate vision sensors can be successfully synchronized to a LED illumination or its reflected light with satisfactory stability and only 28-μs jitters.

A Self-Powered and Flexible Organometallic Halide Perovskite Photodetector with Very High Detectivity

KAUST Repository

Leung, Siu

2018-01-10

Flexible and self-powered photodetectors (PDs) are highly desirable for applications in image sensing, smart building, and optical communications. In this paper, a self-powered and flexible PD based on the methylammonium lead iodide (CH3 NH3 PBI3 ) perovskite is demonstrated. Such a self-powered PD can operate even with irregular motion such as human finger tapping, which enables it to work without a bulky external power source. In addition, with high-quality CH3 NH3 PBI3 perovskite thin film fabricated with solvent engineering, the PD exhibits an impressive detectivity of 1.22 × 1013 Jones. In the self-powered voltage detection mode, it achieves a large responsivity of up to 79.4 V mW-1 cm-2 and a voltage response of up to ≈90%. Moreover, as the PD is made of flexible and transparent polymer films, it can operate under bending and functions at 360 ° of illumination. As a result, the self-powered, flexible, 360 ° omnidirectional perovskite PD, featuring high detectivity and responsivity along with real-world sensing capability, suggests a new direction for next-generation optical communications, sensing, and imaging applications.

A Novel Methodology for Measurements of an LED's Heat Dissipation Factor

Science.gov (United States)

Jou, R.-Y.; Haung, J.-H.

2015-12-01

Heat generation is an inevitable byproduct with high-power light-emitting diode (LED) lighting. The increase in junction temperature that accompanies the heat generation sharply degrades the optical output of the LED and has a significant negative influence on the reliability and durability of the LED. For these reasons, the heat dissipation factor, Kh, is an important factor in modeling and thermal design of LED installations. In this study, a methodology is proposed and experiments are conducted to determine LED heat dissipation factors. Experiments are conducted for two different brands of LED. The average heat dissipation factor of the Edixeon LED is 0.69, and is 0.60 for the OSRAM LED. By using the developed test method and comparing the results to the calculated luminous fluxes using theoretical equations, the interdependence of optical, electrical, and thermal powers can be predicted with a reasonable accuracy. The difference between the theoretical and experimental values is less than 9 %.

Advancements of ultra-high peak power laser diode arrays

Science.gov (United States)

Crawford, D.; Thiagarajan, P.; Goings, J.; Caliva, B.; Smith, S.; Walker, R.

2018-02-01

Enhancements of laser diode epitaxy in conjunction with process and packaging improvements have led to the availability of 1cm bars capable of over 500W peak power at near-infrared wavelengths (770nm to 1100nm). Advances in cooler design allow for multi-bar stacks with bar-to-bar pitches as low as 350μm and a scalable package architecture enabled a single diode assembly with total peak powers of over 1MegaWatt of peak power. With the addition of micro-optics, overall array brightness greater than 10kW/cm2 was achieved. Performance metrics of barbased diode lasers specifically engineered for high peak power and high brightness at wavelengths and pulse conditions commonly used to pump a variety of fiber and solid-state materials are presented.

Module Integrated GaN Power Stage for High Switching Frequency Operation

DEFF Research Database (Denmark)

Nour, Yasser; Knott, Arnold

2017-01-01

is integrated on a high glass transition temperature 0.4 mmthick FR4 substrate configured as a 70 pin ball grid arraypackage. The power stage is tested up to switching frequency of12 MHz. The power stage achieved 88.5 % peak efficiency whenconfigured as a soft switching buck converter operating at 7MHz......An increased attention has been detected todevelop smaller and lighter high voltage power converters in therange of 50 V to 400 V domains. The applications for theseconverters are mainly focused for Power over Ethernet (PoE),LED lighting and ac adapters. Design for high power density isone...... of the targets for next generation power converters. Thispaper presents an 80 V input capable multi-chip moduleintegration of enhancement mode gallium nitride (GaN) fieldeffect transistors (FETs) based power stage. The module design ispresented and validated through experimental results. The powerstage...

Videolaryngoscopes differ substantially in illumination of the oral cavity: A manikin study

Directory of Open Access Journals (Sweden)

Barbe MA Pieters

2016-01-01

Full Text Available Background and Aims: Insufficient illumination of the oral cavity during endotracheal intubation may result in suboptimal conditions. Consequently, suboptimal illumination and laryngoscopy may lead to potential unwanted trauma to soft tissues of the pharyngeal mucosa. We investigated illumination of the oral cavity by different videolaryngoscopes (VLS in a manikin model. Methods: We measured light intensity from the mouth opening of a Laerdal intubation trainer comparing different direct and indirect VLS at three occasions, resembling optimal to less-than-optimal intubation conditions; at the photographer′s dark room, in an operating theatre and outdoors in bright sunlight. Results: Substantial differences in luminance were detected between VLS. The use of LED light significantly improved light production. All VLS produced substantial higher luminance values in a well-luminated environment compared to the dark photographer′s room. The experiments outside-in bright sunlight-were interfered with by direct sunlight penetration through the synthetic material of the manikin, making correct measurement of luminance in the oropharynx invalid. Conclusion: Illumination of the oral cavity differs widely among direct and indirect VLS. The clinician should be aware of the possibility of suboptimal illumination of the oral cavity and the potential risk this poses for the patient.

Imaging of Phase Objects using Partially Coherent Illumination

Energy Technology Data Exchange (ETDEWEB)

Ravizza, F. L. [Univ. of Arizona, Tucson, AZ (United States)

2013-01-01

Screening high-power laser optics for light intensifying phase objects that cause laserinduced damage on downstream optics is critical to sustaining laser operation. Identifying such flaws on large-apertures is quite challenging since they are relatively small and invisible to conventional inspection methods. A Linescan Phase Differential Imaging (LPDI) system was developed to rapidly identify these flaws on large-aperture optics within a single full-aperture dark-field image. We describe a two-step production phase object screening process consisting of LPDI mapping and image analysis, followed by high-resolution interferometry and propagation based evaluation of the downstream damage potential of identified flaws. An image simulation code capable of modeling the LPDI partially coherent illumination was used to optimize its phase object sensitivity.

Design of Elliptic Reflective LED Surgical Shadowless Lamps Using Mathematical Optical Tracing Algorithms

Directory of Open Access Journals (Sweden)

Cheng-Tang Pan

2014-01-01

Full Text Available Traditional surgical shadowless halogen lamps are generally designed as projection type with many light bulbs, which can produce not only mercury pollution but also heat radiation that are serious problems to patient. The study utilized Runge-Kutta methods and mathematical algorithms to design and optimize the freeform lens. The LED (light-emitting diode was adopted to replace the traditional halogen lamp. A uniform lens was designed and fabricated based on the energy conservation. At first, the light field of LED is concentrated through the freeform lens to improve the optical efficiency. Second, the three-shell elliptic curves are applied to the reflective surgical shadowless lamps, where only few LED chips are needed. Light rays emitting from different directions to the target plane can achieve the goal of shadowless. In this study, the LED’s luminance flux is 1,895 lm. The shadow dilution on the target plane is 54%. Ec (central illuminance is 114,900 lux, and the d50/d10 is 57% which is higher than the regulation by 7%, whereas the power consumption is only 20 W. The energy of reflective surgical shadowless lamps can save more than 50%, compared with the traditional projective one.

Local and Global Illumination in the Volume Rendering Integral

Energy Technology Data Exchange (ETDEWEB)

Max, N; Chen, M

2005-10-21

This article is intended as an update of the major survey by Max [1] on optical models for direct volume rendering. It provides a brief overview of the subject scope covered by [1], and brings recent developments, such as new shadow algorithms and refraction rendering, into the perspective. In particular, we examine three fundamentals aspects of direct volume rendering, namely the volume rendering integral, local illumination models and global illumination models, in a wavelength-independent manner. We review the developments on spectral volume rendering, in which visible light are considered as a form of electromagnetic radiation, optical models are implemented in conjunction with representations of spectral power distribution. This survey can provide a basis for, and encourage, new efforts for developing and using complex illumination models to achieve better realism and perception through optical correctness.

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.

UV-LED Curing Efficiency of Wood Coatings

Directory of Open Access Journals (Sweden)

Véronic Landry

2015-12-01

Full Text Available Ultraviolet light emitting diodes (UV-LEDs have attracted great interest in recent years. They can be used to polymerize coatings, such as those used for prefinished wood flooring. In this project, two lamps were compared for their suitability to be used on a wood flooring finishing line: a UV-microwave and a UV-LED lamp. Low heat emission was found for the UV-LED lamp compared to the UV-microwave one. This study also reveals that the 4 W/cm2 UV-LED lamp used is not powerful enough to cure UV high solids acrylate coatings while satisfactory results can be obtained for UV water-based formulations. In fact, conversion percentages were found to be low for the high solids coatings, leaving the coatings tacky. Higher conversion percentages were obtained for the UV water-based formulations. As a result, mass loss, hardness, and scratch resistance found for the samples cured by UV-LED were closed to the ones found for the samples cured using the UV microwave lamp.

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.

Design of an Oximeter Based on LED-LED Configuration and FPGA Technology

Directory of Open Access Journals (Sweden)

Radovan Stojanovic

2013-01-01

Full Text Available A fully digital photoplethysmographic (PPG sensor and actuator has been developed. The sensing circuit uses one Light Emitting Diode (LED for emitting light into human tissue and one LED for detecting the reflectance light from human tissue. A Field Programmable Gate Array (FPGA is used to control the LEDs and determine the PPG and Blood Oxygen Saturation (SpO2. The configurations with two LEDs and four LEDs are developed for measuring PPG signal and Blood Oxygen Saturation (SpO2. N-LEDs configuration is proposed for multichannel SpO2 measurements. The approach resulted in better spectral sensitivity, increased and adjustable resolution, reduced noise, small size, low cost and low power consumption.

Design of an oximeter based on LED-LED configuration and FPGA technology.

Science.gov (United States)

Stojanovic, Radovan; Karadaglic, Dejan

2013-01-04

A fully digital photoplethysmographic (PPG) sensor and actuator has been developed. The sensing circuit uses one Light Emitting Diode (LED) for emitting light into human tissue and one LED for detecting the reflectance light from human tissue. A Field Programmable Gate Array (FPGA) is used to control the LEDs and determine the PPG and Blood Oxygen Saturation (S(p)O(2)). The configurations with two LEDs and four LEDs are developed for measuring PPG signal and Blood Oxygen Saturation (S(p)O(2)). N-LEDs configuration is proposed for multichannel S(p)O(2) measurements. The approach resulted in better spectral sensitivity, increased and adjustable resolution, reduced noise, small size, low cost and low power consumption.

High speed and high functional inverter power supplies for plasma generation and control, and their performance

International Nuclear Information System (INIS)

Uesugi, Yoshihiko; Razzak, Mohammad A.; Kondo, Kenji; Kikuchi, Yusuke; Takamura, Shuichi; Imai, Takahiro; Toyoda, Mitsuhiro

2003-01-01

The Rapid development of high power and high speed semiconductor switching devices has led to their various applications in related plasma fields. Especially, a high speed inverter power supply can be used as an RF power source instead of conventional linear amplifiers and a power supply to control the magnetic field in a fusion plasma device. In this paper, RF thermal plasma production and plasma heating experiments are described emphasis placed on using a static induction transistor inverter at a frequency range between 200 kHz and 2.5 MHz as an RF power supply. Efficient thermal plasma production is achieved experimentally by using a flexible and easily operated high power semiconductor inverter power supply. Insulated gate bipolar transistor (IGBT) inverter power supplies driven by a high speed digital signal processor are applied as tokamak joule coil and vertical coil power supplies to control plasma current waveform and plasma equilibrium. Output characteristics, such as the arbitrary bipolar waveform generation of a pulse width modulation (PWM) inverter using digital signal processor (DSP) can be successfully applied to tokamak power supplies for flexible plasma current operation and fast position control of a small tokamak. (author)