The photocytotoxicity of different lights on mammalian cells in interior lighting system.

PubMed

Song, Jiayin; Gao, Tingting; Ye, Maole; Bi, Hongtao; Liu, Gang

2012-12-05

In the present paper, two light sources commonly used in interior lighting system: incandescent light and light emitting diode (LED) were chosen to evaluate their influences on three kinds of mammalian cells, together with UVA and UVB, and the mechanism of the photocytotoxicity was investigated in terms of intracellular ROS production, lipid peroxidation, SOD activity and GSH level assays. The results showed that LED and incandescent light both had some photocytotoxicities. In the interior lighting condition (100lx-250lx), the cytotoxicities of LED and incandescent lamp on RF/6A cells (rhesus retinal pigment epithelium cell line) were stronger than that on two fibroblast cell lines, while the cytotoxicity of UVA and UVB on HS68 cells (fibroblast cell line) was highest in the tests. The mechanism analysis revealed that the photocytotoxicities of LED and incandescent lamp were both caused by cell lipid peroxidation. LED and incandescent light could promote the production of ROS, raise lipid peroxidation level and lower the activity of the antioxidant key enzymes in mammalian cells, and finally cause a number of cells death. However, the negative function of LED was significantly smaller than incandescent light and ultraviolet in daily interior lighting condition. And the significantly lower photocytotoxicity of LED might be due to the less existence of ultraviolet. Therefore, LED is an efficient and relative safe light source in interior lighting system, which should be widely used instead of traditional light source. Copyright © 2012 Elsevier B.V. All rights reserved.

Modular design of the LED vehicle projector headlamp system.

PubMed

Hsieh, Chi-Chang; Li, Yan-Huei; Hung, Chih-Ching

2013-07-20

A well designed headlamp for a vehicle lighting system is very important as it provides drivers with safe and comfortable driving conditions at night or in dark places. With the advances of the semiconductor technology, the LED has become the fourth generation lighting source in the auto industry. In this study, we will propose a LED vehicle projector headlamp system. This headlamp system contains several LED headlamp modules, and every module of it includes four components: focused LEDs, asymmetric metal-based plates, freeform surfaces, and condenser lenses. By optimizing the number of LED headlamp modules, the proposed LED vehicle projector headlamp system has only five LED headlamp modules. It not only provides the low-beam cutoff without a shield, but also meets the requirements of the ECE R112 regulation. Finally, a prototype of the LED vehicle projector headlamp system was assembled and fabricated to create the correct light pattern.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tracy, Jennifer; Mills, Evan

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 halfmore » 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 kerosene lighting, reduced crowding which in turn created a less stressful environment for the chickens. The far higher levels of illumination also created a better environment for the workers, while eliminating the time required for obtaining fuel and maintaining kerosene lanterns. An additional advantage of the LED system relative to the solar fluorescent system was that the former does not require a skilled technician to carry out the installation. The portable LED system lighting layout is also more easily adjusted than that of the hardwired fluorescent systems. Furthermore, switching to the LED system avoids over one metric ton of carbon dioxide emissions per house on an annual basis compared to kerosene. There is high potential for replication of this particular LED lighting strategy in the developing world. In order to estimate the scale of kerosene use and the potential for savings, more information is needed on the numbers of chickens produced off-grid, as well as lighting uses for other categories of poultry production (egg layers, indigenous broilers ). Our discovery that weight gain did not slow in the solar-fluorescent house after it experienced extended lighting outages beginning on day 14 of the 35-day study suggests that conventional farming practices in Kenyan broiler operations may call for more hours of lighting than is needed to achieve least-cost production.« less

Life of LED-Based White Light Sources

NASA Astrophysics Data System (ADS)

Narendran, Nadarajah; Gu, Yimin

2005-09-01

Even though light-emitting diodes (LEDs) may have a very long life, poorly designed LED lighting systems can experience a short life. Because heat at the p-n-junction is one of the main factors that affect the life of the LED, by knowing the relationship between life and heat, LED system manufacturers can design and build long-lasting systems. In this study, several white LEDs from the same manufacturer were subjected to life tests at different ambient temperatures. The exponential decay of light output as a function of time provided a convenient method to rapidly estimate life by data extrapolation. The life of these LEDs decreases in an exponential manner with increasing temperature. In a second experiment,several high-power white LEDs from different manufacturers were life-tested under similar conditions. Results show that the different products have significantly different life values.

Medical lighting composed of LED arrays for surgical operation

NASA Astrophysics Data System (ADS)

Shimada, Junichi; Kawakami, Yoichi; Fujita, Shigeo

2001-05-01

Everywhere in the world, the highest quality and quantity of lighting is required during the surgical operations. However, the surgical approach has had many types and various angles, common ceiling surgical halogen lighting system cannot provide an adequate amount of beams because the surgeons' heads hinder the illuminations from reaching the operation field. Here, we newly design surgical lighting system composed of white LEDs equipped on both sides of goggles, which controls the lighting beams to the gazing point. With this system, it is just needed for surgeons to wear light plastic goggles with high quality LEDs made by Nichia. In fact, we have succeeded in the first internal shunt operation in the left forearm using the surgical LED lighting system on 11th Sept 2000. The electrical power for the system was supplied from lithium-ion battery for 2 hours. Since the white LEDs used were composed of InGaN- blue-emitters and YAG-yellow-phosphors, the color rendering property was not sufficient in the reddish colors. Therefore, in the next approach, it is very important to develop the spectral distribution of white LED to render inherent color of raw flesh such as skin, blood, fat tissue and internal organs.

High-output LED-based light engine for profile lighting fixtures with high color uniformity using freeform reflectors.

PubMed

Gadegaard, Jesper; Jensen, Thøger Kari; Jørgensen, Dennis Thykjær; Kristensen, Peter Kjær; Søndergaard, Thomas; Pedersen, Thomas Garm; Pedersen, Kjeld

2016-02-20

In the stage lighting and entertainment market, light engines (LEs) for lighting fixtures are often based on high-intensity discharge (HID) bulbs. Switching to LED-based light engines gives possibilities for fast switching, additive color mixing, a longer lifetime, and potentially, more energy-efficient systems. The lumen output of a single LED is still not sufficient to replace an HID source in high-output profile fixtures, but combining multiple LEDs can create an LE with a similar output, but with added complexity. This paper presents the results of modeling and testing such a light engine. Custom ray-tracing software was used to design a high-output red, green and blue LED-based light engine with twelve CBT-90 LEDs using a dual-reflector principle. The simulated optical system efficiency was 0.626 with a perfect (R=1) reflector coating for light delivered on a target surface through the entire optical system. A profile lighting fixture prototype was created, and provided an output of 6744 lumen and an efficiency of 0.412. The lower efficiency was mainly due to a non-optimal reflector coating, and the optimized design is expected to reach a significantly higher efficiency.

Improving Light Distribution by Zoom Lens for Electricity Savings in a Plant Factory with Light-Emitting Diodes.

PubMed

Li, Kun; Li, Zhipeng; Yang, Qichang

2016-01-01

The high energy consumption of a plant factory is the biggest issue in its rapid expansion, especially for lighting electricity, which has been solved to a large extent by light-emitting diodes (LED). However, the remarkable potential for further energy savings remains to be further investigated. In this study, an optical system applied just below the LED was designed. The effects of the system on the growth and photosynthesis of butterhead lettuce (Lactuca sativa var. capitata) were examined, and the performance of the optical improvement in energy savings was evaluated by comparison with the traditional LED illumination mode. The irradiation patterns used were LED with zoom lenses (Z-LED) and conventional non-lenses LED (C-LED). The seedlings in both treatments were exposed to the same light environment over the entire growth period. The improvement saved over half of the light source electricity, while prominently lowering the temperature. Influenced by this, the rate of photosynthesis sharply decreased, causing reductions in plant yield and nitrate content, while having no negative effects on morphological parameters and photosynthetic pigment contents. Nevertheless, the much higher light use efficiency of Z-LEDs makes this system a better approach to illumination in a plant factory with artificial lighting.

Improving Light Distribution by Zoom Lens for Electricity Savings in a Plant Factory with Light-Emitting Diodes

PubMed Central

Li, Kun; Li, Zhipeng; Yang, Qichang

2016-01-01

The high energy consumption of a plant factory is the biggest issue in its rapid expansion, especially for lighting electricity, which has been solved to a large extent by light-emitting diodes (LED). However, the remarkable potential for further energy savings remains to be further investigated. In this study, an optical system applied just below the LED was designed. The effects of the system on the growth and photosynthesis of butterhead lettuce (Lactuca sativa var. capitata) were examined, and the performance of the optical improvement in energy savings was evaluated by comparison with the traditional LED illumination mode. The irradiation patterns used were LED with zoom lenses (Z-LED) and conventional non-lenses LED (C-LED). The seedlings in both treatments were exposed to the same light environment over the entire growth period. The improvement saved over half of the light source electricity, while prominently lowering the temperature. Influenced by this, the rate of photosynthesis sharply decreased, causing reductions in plant yield and nitrate content, while having no negative effects on morphological parameters and photosynthetic pigment contents. Nevertheless, the much higher light use efficiency of Z-LEDs makes this system a better approach to illumination in a plant factory with artificial lighting. PMID:26904062

Kansas highway LED illumination manual : a guide for the use of LED lighting systems.

DOT National Transportation Integrated Search

2015-12-01

The research project was aimed to assist the Kansas Department of Transportation (KDOT) in the development of a Highway LED Illumination Manual for guiding the upcoming implementation of successful LED roadway lighting systems in Kansas to replace th...

Analysis of condition for uniform lighting generated by array of light emitting diodes with large view angle.

PubMed

Qin, Zong; Wang, Kai; Chen, Fei; Luo, Xiaobing; Liu, Sheng

2010-08-02

In this research, the condition for uniform lighting generated by array of LEDs with large view angle was studied. The luminous intensity distribution of LED is not monotone decreasing with view angle. A LED with freeform lens was designed as an example for analysis. In a system based on LEDs designed in house with a thickness of 20mm and rectangular arrangement, the condition for uniform lighting was derived and the analytical results demonstrated that the uniformity was not decreasing monotonously with the increasing of LED-to-LED spacing. The illuminance uniformities were calculated with Monte Carlo ray tracing simulations and the uniformity was found to increase with the increasing of certain LED-to-LED spacings anomalously. Another type of large view angle LED and different arrangements were discussed in addition. Both analysis and simulation results showed that the method is available for LED array lighting system design on the basis of large view angle LED..

Beacon system based on light-emitting diode sources for runways lighting

NASA Astrophysics Data System (ADS)

Montes, Mario González; Vázquez, Daniel; Fernandez-Balbuena, Antonio A.; Bernabeu, Eusebio

2014-06-01

New aeronautical ground lighting techniques are becoming increasingly important to ensure the safety and reduce the maintenance costs of the plane's tracks. Until recently, tracks had embedded lighting systems whose sources were based on incandescent lamps. But incandescent lamps have several disadvantages: high energy consumption and frequent breakdowns that result in high maintenance costs (lamp average life-time is ˜1500 operating hours) and the lamp's technology has a lack of new lighting functions, such as signal handling and modification. To solve these problems, the industry has developed systems based on light-emitting diode (LED) technology with improved features: (1) LED lighting consumes one tenth the power, (2) it improves preventive maintenance (an LED's lifetime range is between 25,000 and 100,000 hours), and (3) LED lighting technology can be controlled remotely according to the needs of the track configuration. LEDs have been in use for more than three decades, but only recently, around 2002, have they begun to be used as visual aids, representing the greatest potential change for airport lighting since their inception in the 1920s. Currently, embedded LED systems are not being broadly used due to the specific constraints of the rules and regulations of airports (beacon dimensions, power system technology, etc.). The fundamental requirements applied to embedded lighting systems are to be hosted on a volume where the dimensions are usually critical and also to integrate all the essential components for operation. An embedded architecture that meets the lighting regulations for airport runways is presented. The present work is divided into three main tasks: development of an optical system to optimize lighting according to International Civil Aviation Organization, manufacturing prototype, and model validation.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kinzey, B. R.; Davis, R. G.

2014-09-30

On the I-35W Bridge in Minneapolis, Minnesota, the GATEWAY program conducted a two-phase demonstration of LED roadway lighting on the main span, which is one of the country's oldest continuously operated exterior LED lighting installations. The Phase II report documents longer-term performance of the LED lighting system that was installed in 2008, and is the first report on the longer-term performance of LED lighting in the field.

Light-emitting diode-based multiwavelength diffuse optical tomography system guided by ultrasound

PubMed Central

Yuan, Guangqian; Alqasemi, Umar; Chen, Aaron; Yang, Yi; Zhu, Quing

2014-01-01

Abstract. Laser diodes are widely used in diffuse optical tomography (DOT) systems but are typically expensive and fragile, while light-emitting diodes (LEDs) are cheaper and are also available in the near-infrared (NIR) range with adequate output power for imaging deeply seated targets. In this study, we introduce a new low-cost DOT system using LEDs of four wavelengths in the NIR spectrum as light sources. The LEDs were modulated at 20 kHz to avoid ambient light. The LEDs were distributed on a hand-held probe and a printed circuit board was mounted at the back of the probe to separately provide switching and driving current to each LED. Ten optical fibers were used to couple the reflected light to 10 parallel photomultiplier tube detectors. A commercial ultrasound system provided simultaneous images of target location and size to guide the image reconstruction. A frequency-domain (FD) laser-diode-based system with ultrasound guidance was also used to compare the results obtained from those of the LED-based system. Results of absorbers embedded in intralipid and inhomogeneous tissue phantoms have demonstrated that the LED-based system provides a comparable quantification accuracy of targets to the FD system and has the potential to image deep targets such as breast lesions. PMID:25473884

IN VITRO STUDY OF THE PULP CHAMBER TEMPERATURE RISE DURING LIGHT-ACTIVATED BLEACHING

PubMed Central

Carrasco, Thaise Graciele; Carrasco-Guerisoli, Laise Daniela; Fröner, Izabel Cristina

2008-01-01

This study evaluated in vitro the pulp chamber temperature rise induced by the light-activated dental bleaching technique using different light sources. The root portions of 78 extracted sound human mandibular incisors were sectioned approximately 2 mm below the cementoenamel junction. The root cavities of the crowns were enlarged to facilitate the correct placing of the sensor into the pulp chamber. Half of specimens (n=39) was assigned to receive a 35% hydrogen peroxide gel on the buccal surface and the other halt (n=39) not to receive the bleaching agent. Three groups (n=13) were formed for each condition (bleach or no bleach) according to the use of 3 light sources recommended for dental bleaching: a light-emitting diode (LED)-laser system, a LED unit and a conventional halogen light. The light sources were positioned perpendicular to the buccal surface at a distance of 5 mm and activated during 30 s. The differences between the initial and the highest temperature readings for each specimen were obtained, and, from the temperature changes, the means for each specimen and each group were calculated. The values of temperature rise were compared using Kruskal-Wallis test at 1% significance level. Temperature rise varied significantly depending on the light-curing unit, with statistically significant differences (p<0.01) among the groups. When the bleaching agent was not applied, the halogen light induced the highest temperature rise (2.38±0.66°C). The LED unit produced the lowest temperature increase (0.29±0.13°C); but there was no significant difference between LED unit and LED-laser system (0.35±0.15°C) (p>0.01). When the bleaching agent was applied, there were significant differences among groups (p<0.01): halogen light induced the highest temperature rise (1.41±0.64°C), and LED-laser system the lowest (0.33±0.12°C); however, there was no difference between LED-laser system and LED unit (0.44±0.11°C). LED and LED-laser system did not differ significantly from each other regardless the temperature rise occurred with or without bleaching agent application. It may be concluded that during light-activated tooth bleaching, with or without the bleaching agent, halogen light promoted higher pulp chamber temperature rise than LED unit and LED-laser system. The tested light-curing units provided increases in the pulp chamber temperature that were compatible with pulpal health. PMID:19089234

White LED sources for vehicle forward lighting

NASA Astrophysics Data System (ADS)

Van Derlofske, John F.; McColgan, Michele W.

2002-11-01

Considerations for the use of white light emitting diode (LED) sources to produce illumination for automotive forward lighting is presented. Due to their reliability, small size, lower consumption, and lower heat generation LEDs are a natural choice for automotive lighting systems. Currently, LEDs are being sucessfully employed in most vehicle lighting applications. In these applications the light levels, distributions, and colors needed are achievable by present LED technologies. However, for vehicle white light illumination applications LEDs are now only being considered for low light level applications, such as back-up lamps. This is due to the relatively low lumen output that has been available up to now in white LEDs. With the advent of new higher lumen packages, and with the promise of even higher light output in the near future, the use of white LEDs sources for all vehicle forward lighting applications is beginning to be considered. Through computer modeling and photometric evaluation this paper examines the possibilities of using currently available white LED technology for vehicle headlamps. It is apparent that optimal LED sources for vehicle forward lighting applications will be constructed with hereto undeveloped technology and packaging configurations. However, the intent here in exploring currently available products is to begin the discussion on the design possibilities and significant issues surrounding LEDs in order to aid in the design and development of future LED sources and systems. Considerations such as total light output, physical size, optical control, power consumption, color appearance, and the effects of white LED spectra on glare and peripheral vision are explored. Finally, conclusions of the feasibility of current LED technology being used in these applications and recommendations of technology advancements that may need to occur are made.

Kansas highway LED illumination manual : a guide for the use of LED lighting systems : [technical summary].

DOT National Transportation Integrated Search

2015-12-01

The research project was aimed to assist the Kansas Department of Transportation (KDOT) in the development of a Highway LED Illumination Manual for guiding the upcoming implementation of successful LED roadway lighting systems in Kansas to replace th...

Visual color matching system based on RGB LED light source

NASA Astrophysics Data System (ADS)

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.

Surgical operation using lighting goggle composed of white LED arrays

NASA Astrophysics Data System (ADS)

Shimada, Junichi; Kawakami, Yoichi; Fujita, Shigeo

2001-12-01

Everywhere in the world, the highest quality and quantity of lighting is required during the surgical operations. However, the surgical approach has had many types and various angles, common ceiling surgical halogen lighting system cannot provide an adequate amount of beams because the surgeons' heads hinder the illuminations from reaching the operation field. Here, we newly design surgical lighting system composed of white LEDs equipped on both sides of goggles, which controls the lighting beams to the gazing point. With this system, it is just needed for surgeons to wear light plastic goggles with high quality LEDs made by Nichia. In fact, we have succeeded in the first internal shunt operation in the left forearm using the surgical LED lighting system on 11th Sept 2000. The electrical power for the system was supplied from lithium-ion battery for 2 hours. Since the white LEDs used were composed of InGaN-blue-emitters and YAG-yellow-phosphors, the color rendering property was not sufficient in the reddish colors. Therefore, in the next approach, it is very important to develop the spectral distribution of white LED to render inherent color of raw flesh such as skin, blood, fat tissue and internal organs. To improve the color rendering in red colors, some adjustments should be given in the fluorescents layers. Design of goggle is also very important for cutting into the real practical market of white LEDs.

Smart LED lighting for major reductions in power and energy use for plant lighting in space

NASA Astrophysics Data System (ADS)

Poulet, Lucie

Launching or resupplying food, oxygen, and water into space for long-duration, crewed missions to distant destinations, such as Mars, is currently impossible. Bioregenerative life-support systems under development worldwide involving photoautotrophic organisms offer a solution to the food dilemma. However, using traditional Earth-based lighting methods, growth of food crops consumes copious energy, and since sunlight will not always be available at different space destinations, efficient electric lighting solutions are badly needed to reduce the Equivalent System Mass (ESM) of life-support infrastructure to be launched and transported to future space destinations with sustainable human habitats. The scope of the present study was to demonstrate that using LEDs coupled to plant detection, and optimizing spectral and irradiance parameters of LED light, the model crop lettuce (Lactuca sativa L. cv. Waldmann's Green) can be grown with significantly lower electrical energy for plant lighting than using traditional lighting sources. Initial experiments aimed at adapting and troubleshooting a first-generation "smart" plant-detection system coupled to LED arrays resulted in optimizing the detection process for plant position and size to the limits of its current design. Lettuce crops were grown hydroponically in a growth chamber, where temperature, relative humidity, and CO2 level are controlled. Optimal irradiance and red/blue ratio of LED lighting were determined for plant growth during both lag and exponential phases of crop growth. Under optimizing conditions, the efficiency of the automatic detection system was integrated with LED switching and compared to a system in which all LEDs were energized throughout a crop-production cycle. At the end of each cropping cycle, plant fresh and dry weights and leaf area were measured and correlated with the amount of electrical energy (kWh) consumed. Preliminary results indicated that lettuce plants grown under optimizing conditions with red and blue LED lighting required 12 times less energy than with a traditional high-intensity discharge lighting system. This study paves the way for refinement of the smart lighting system and further, major reductions in ESM for space life-support systems and for ground-based controlled-environment agriculture. Project supported by NASA grant number NNX09AL99G.

Smooth light extraction in lighting optical fibre

NASA Astrophysics Data System (ADS)

Fernandez-Balbuena, A. A.; Vazquez-Molini, D.; Garcia-Botella, A.; Martinez-Anton, J. C.; Bernabeu, E.

2011-10-01

Recent advances in LED technology have relegated the use of optical fibre for general lighting, but there are several applications where it can be used as scanners lighting systems, daylight, cultural heritage lighting, sensors, explosion risky spaces, etc. Nowadays the use of high intensity LED to inject light in optical fibre increases the possibility of conjugate fibre + LED for lighting applications. New optical fibres of plastic materials, high core diameter up to 12.6 mm transmit light with little attenuation in the visible spectrum but there is no an efficient and controlled way to extract the light during the fibre path. Side extracting fibres extracts all the light on 2π angle so is not well suited for controlled lighting. In this paper we present an extraction system for mono-filament optical fibre which provides efficient and controlled light distribution. These lighting parameters can be controlled with an algorithm that set the position, depth and shape of the optical extraction system. The extraction system works by total internal reflection in the core of the fibre with high efficiency and low cost. A 10 m length prototype is made with 45° sectional cuts in the fibre core as extraction system. The system is tested with a 1W white LED illuminator in one side.

Projecting LED product life based on application

NASA Astrophysics Data System (ADS)

Narendran, Nadarajah; Liu, Yi-wei; Mou, Xi; Thotagamuwa, Dinusha R.; Eshwarage, Oshadhi V. Madihe

2016-09-01

LED products have started to displace traditional light sources in many lighting applications. One of the commonly claimed benefits for LED lighting products is their long useful lifetime in applications. Today there are many replacement lamp products using LEDs in the marketplace. Typically, lifetime claims of these replacement lamps are in the 25,000-hour range. According to current industry practice, the time for the LED light output to reach the 70% value is estimated according to IESNA LM-80 and TM-21 procedures and the resulting value is reported as the whole system life. LED products generally experience different thermal environments and switching (on-off cycling) patterns when used in applications. Current industry test methods often do not produce accurate lifetime estimates for LED systems because only one component of the system, namely the LED, is tested under a continuous-on burning condition without switching on and off, and because they estimate for only one failure type, lumen depreciation. The objective of the study presented in this manuscript was to develop a test method that could help predict LED system life in any application by testing the whole LED system, including on-off power cycling with sufficient dwell time, and considering both failure types, catastrophic and parametric. The study results showed for the LED A-lamps tested in this study, both failure types, catastrophic and parametric, exist. The on-off cycling encourages catastrophic failure, and maximum operating temperature influences the lumen depreciation rate and parametric failure time. It was also clear that LED system life is negatively affected by on-off switching, contrary to commonly held belief. In addition, the study results showed that most of the LED systems failed catastrophically much ahead of the LED light output reaching the 70% value. This emphasizes the fact that life testing of LED systems must consider catastrophic failure in addition to lumen depreciation, and the shorter of the two failure modes must be selected as the system life. The results of this study show a shorter time test procedure can be developed to accurately predict LED system life in any application by knowing the LED temperature and the switching cycle.

Implantable wireless powered light emitting diode (LED) for near-infrared photoimmunotherapy: device development and experimental assessment in vitro and in vivo.

PubMed

Nakajima, Kohei; Kimura, Toshihiro; Takakura, Hideo; Yoshikawa, Yasuo; Kameda, Atsushi; Shindo, Takayuki; Sato, Kazuhide; Kobayashi, Hisataka; Ogawa, Mikako

2018-04-13

The aim of this study was to develop and assess a novel implantable, wireless-powered, light-emitting diode (LED) for near-infrared photoimmunotherapy (NIR-PIT). NIR-PIT is a recently developed cancer therapy that uses NIR light and antibody-photosensitizer conjugates and is able to induce cancer-specific cell death. Due to limited light penetration depth it is currently unable to treat tumors in deep tissues. Use of implanted LED might potentially overcome this limitation. The wireless LED system was able to emit NIR light up to a distance of 20 cm from the transmitter coil by using low magnetic fields as compliant with limits for use in humans. Results indicated that the LED system was able to kill tumor cells in vitro and to suppress tumor growth in implanted tumor-bearing mice. Results indicated that the proposed implantable wireless LED system was able to suppress tumor growth in vivo . These results are encouraging as wireless LED systems such as the one here developed might be a possible solution to treat tumors in deep regions in humans. Further research in this area would be important. An implantable LED system was developed. It consisted of a LED capsule including two LED sources and a receiver coil coupled with an external coil and power source. Wireless power transmission was guaranteed by using electromagnetic induction. The system was tested in vitro by using EGFR-expressing cells and HER2-expressing cells. The system was also tested in vivo in tumor-bearing mice.

Effect of UV irradiation on the apoptosis and necrosis of Jurkat cells using UV LEDs

NASA Astrophysics Data System (ADS)

Inada, Shunko A.; Amano, Hiroshi; Akasaki, Isamu; Morita, Akimichi; Kobayashi, Keiko

2009-02-01

Phototherapy is a very effective method for treating most of the incurable skin diseases. A fluorescent light bulb is used as a conventional UV light source for this type of therapy. However, infrared radiation from the light source sometimes causes serious problems on patient's health. In addition, the normal part of the skin is irradiated when a large fluorescent light bulb is used. Moreover, a conventional UV irradiation system is heavy and has a short lifetime and a high electrical power consumption. Therefore, a new UV light source for solving the problems of phototherapy is required. To realize low-power-consumption, lightweight and long-lifetime systems, group III nitride-based UV-A1 light-emitting diodes (LEDs) were investigated. We examined the UV LED irradiation of Jurkat cell, which is a tumor cell and more sensitive to UV light than a healthy cell. The numbers of apoptotic and necrotic cells were confirmed to be the same using a UV LED and a conventional lamp system. The UV LED showed the possibility of realizing a new UV light source for phototherapy.

Efficient conceptual design for LED-based pixel light vehicle headlamps

NASA Astrophysics Data System (ADS)

Held, Marcel Philipp; Lachmayer, Roland

2017-12-01

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

Significant reduction in energy for plant-growth lighting in space using targeted LED lighting and spectral manipulation

NASA Astrophysics Data System (ADS)

Poulet, L.; Massa, G. D.; Morrow, R. C.; Bourget, C. M.; Wheeler, R. M.; Mitchell, C. A.

2014-07-01

Bioregenerative life-support systems involving photoautotrophic organisms will be necessary to sustain long-duration crewed missions at distant space destinations. Since sufficient sunlight will not always be available for plant growth at many space destinations, efficient electric-lighting solutions are greatly needed. The present study demonstrated that targeted plant lighting with light-emitting diodes (LEDs) and optimizing spectral parameters for close-canopy overhead LED lighting allowed the model crop leaf lettuce (Lactuca sativa L. cv. 'Waldmann's Green') to be grown using significantly less electrical energy than using traditional electric-lighting sources. Lettuce stands were grown hydroponically in a growth chamber controlling temperature, relative humidity, and CO2 level. Several red:blue ratios were tested for growth rate during the lag phase of lettuce growth. In addition, start of the exponential growth phase was evaluated. Following establishment of a 95% red + 5% blue spectral balance giving the best growth response, the energy efficiency of a targeted lighting system was compared with that of two total coverage (untargeted) LED lighting systems throughout a crop-production cycle, one using the same proportion of red and blue LEDs and the other using white LEDs. At the end of each cropping cycle, whole-plant fresh and dry mass and leaf area were measured and correlated with the amount of electrical energy (kWh) consumed for crop lighting. Lettuce crops grown with targeted red + blue LED lighting used 50% less energy per unit dry biomass accumulated, and the total coverage white LEDs used 32% less energy per unit dry biomass accumulated than did the total coverage red + blue LEDs. An energy-conversion efficiency of less than 1 kWh/g dry biomass is possible using targeted close-canopy LED lighting with spectral optimization. This project was supported by NASA grant NNX09AL99G.

Cost and energy-efficient (LED, induction and plasma) roadway lighting.

DOT National Transportation Integrated Search

2013-11-01

There is an increasing interest in using new lighting technologies such as light emitting diode (LED), Induction, and Plasma light sources : in roadway lighting. The most commonly claimed benefits of the new lighting systems include increased reliabi...

Monolithic LED arrays, next generation smart lighting sources

NASA Astrophysics Data System (ADS)

Lagrange, Alexandre; Bono, Hubert; Templier, François

2016-03-01

LED have become the main light sources of the future as they open the path for intelligent use of light in time, intensity and color. In many usages, strong energy economy is done by adjusting these properties. The smart lighting has three dimensions, energy efficiency brought by GaN blue emitting LEDs, integration of electronics, sensors, microprocessors in the lighting system and development of new functionalities and services provided by the light. Monolithic LED arrays allow two major innovations, the spatial control of light emission and the adjustment of the electrical properties of the source.

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

NASA Astrophysics Data System (ADS)

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.

Thermal management of LEDs: package to system

NASA Astrophysics Data System (ADS)

Arik, Mehmet; Becker, Charles A.; Weaver, Stanton E.; Petroski, James

2004-01-01

Light emitting diodes, LEDs, historically have been used for indicators and produced low amounts of heat. The introduction of high brightness LEDs with white light and monochromatic colors have led to a movement towards general illumination. The increased electrical currents used to drive the LEDs have focused more attention on the thermal paths in the developments of LED power packaging. The luminous efficiency of LEDs is soon expected to reach over 80 lumens/W, this is approximately 6 times the efficiency of a conventional incandescent tungsten bulb. Thermal management for the solid-state lighting applications is a key design parameter for both package and system level. Package and system level thermal management is discussed in separate sections. Effect of chip packages on junction to board thermal resistance was compared for both SiC and Sapphire chips. The higher thermal conductivity of the SiC chip provided about 2 times better thermal performance than the latter, while the under-filled Sapphire chip package can only catch the SiC chip performance. Later, system level thermal management was studied based on established numerical models for a conceptual solid-state lighting system. A conceptual LED illumination system was chosen and CFD models were created to determine the availability and limitations of passive air-cooling.

CMOS-compatible plenoptic detector for LED lighting applications.

PubMed

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

2015-09-07

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

Thermal Analysis of LED Phosphor Layer

NASA Astrophysics Data System (ADS)

Perera, Ukwatte Lokuliyanage Indika Upendra

Solid-state lighting technology has progressed to a level where light-emitting diode (LED) products are either on par or better than their traditional lighting technology counterparts with respect to efficacy and lifetime. At present, the most common method to create "white" light from LEDs for illumination applications is by using the LED primary radiation and wavelength-converting materials. In this method, the re-emission from the wavelength-converting materials excited by the LED primary radiation is combined with the LED primary radiation to create the "white" light. During this conversion process, heat is generated as a result of conversion inefficiencies and other loss mechanisms in the LED and the wavelength-converting materials. This generated heat, if not properly dissipated, increases the operating temperature, thereby increasing the light output degradation of the system over both the short and long term. The heat generation of the LED and thermal management of the LED have been studied extensively. Methods to effectively dissipate heat from the LEDs and maintain lower LED operating temperature are well understood. However, investigation of factors driving heat generation, the resulting temperature distribution in the phosphor layer, and the influence of the phosphor layer temperature on LED performance and reliability have not received the same focus. The goal of this dissertation was to understand the main factors driving heat and light generation and the transport of light and heat in the wavelength-converting layer of an LED system. Another goal was to understand the interaction between heat and light in the system and to develop and analyze a solution to reduce the wavelength-converting layer operating temperature, thereby improving light output and reliability. Even though past studies have explored generation and transfer separately for light and heat, to the best of the author's knowledge, this is the first study that has analyzed both factors simultaneously to optimize the performance of a phosphor-converted LED system, thus contributing new knowledge to the field. In this dissertation, a theoretical model was developed that modeled both light propagation and heat transfer in the wavelength-converting layer for identifying the factors influencing heat generation. This theoretical model included temperature-dependent phosphor efficiency and light absorption in the phosphor layer geometry. Experimental studies were used to validate the developed model. The model indicated good agreement with the experimental results. The developed theoretical model was then used to model experimental studies. These experiment results were compared with the model predicted results for total radiant power output of LED systems and phosphor layer surface temperature. These comparisons illustrated the effectiveness of a dedicated heat dissipation method in reducing the operating temperature of the wavelength-converting layer, and the contribution of different heat dissipation mechanisms were quantified using the developed numerical model. In addition to these short-term studies, an experiment was conducted to validate the effectiveness of the dedicated wavelength-converting heat sink design to improve system lifetime by reducing phosphor layer operating temperature. The proposed heat sink design decreased the operating temperature of the phosphor layer by ~10°C, improving lifetime by twofold. Finally, this dissertation investigated the potential of the developed theoretical model being used as a tool for prioritizing research tasks and as a design tool during the material selection and system configuration phases.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

2011-05-06

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilkerson, Andrea M.; McCullough, Jeffrey J.

The Yuma Sector Border Patrol Area is a high flux lighting application in a high temperature environment, presenting a formidable challenge for light-emitting diodes (LEDs). This retrofit is an Energy Savings Performance Contract ENABLE project under the U.S. Department of Energy (DOE) Federal Energy Management Program. If high flux LED technology performs well in a region with high ambient temperature and solar radiation, it can perform well in most outdoor environments. The design process for the Yuma retrofit has already provided valuable knowledge to CBP and DOE. The LED lighting system selected for the retrofit is expected to reduce energymore » consumption 69% compared to the incumbent quartz metal halide (QMH) lighting system. If the LED lighting system is installed, GATEWAY will continue to document and disseminate information regarding the installation and long-term performance so that others may also gain valuable knowledge from the Yuma Sector Border Patrol Area lighting retrofit.« less

Analysis of LED arrangement in an array with respect to lens geometry

NASA Astrophysics Data System (ADS)

Ley, Peer-Phillip; Held, Marcel Philipp; Lachmayer, Roland

2018-02-01

Highly adaptive light sources such as LED arrays have been surpassing conventional light sources (halogen, xenon) for automotive applications. Individual LED arrangements within the array, high durability and low energy consumption of the LEDs are some of the reasons. With the introduction of Audi's Matrix beam system, efforts to increase the quantity of pixels were already underway and the stage was practically set for pixel light systems. Current efforts are focused towards the exploration of an optimal LED array density and the use of spatial light modulators. In both cases, one question remains - What arrangement of LEDs is the most suitable in terms of light output efficiency for a given lens geometry? The radiation characteristics of an LED usually shows a Lambertian pattern. Following from the definition of luminous efficacy, this characteristic property of LEDs has a decisive impact on the lens geometry in a given array. Due to the proportional correlation between the lens diameter and the distance of LEDs emission surface to the lens surface. Assuming a constant viewing angle an increase of the distance leads to an increase of the lens diameter. In this paper, two different approaches for an optimized LED array with regards to the LED arrangement will be presented. The introduced designs result from one imaging and one non-imaging optical system, which will be investigated. The paper is concluded with a comparative analysis of the LED array design as a function of the LED pitch and the luminous efficacy.

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

NASA Astrophysics Data System (ADS)

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 characteristics of the head-mounted LED were evaluated.

Lighting theory and luminous characteristics of white light-emitting diodes

NASA Astrophysics Data System (ADS)

Uchida, Yuji; Taguchi, Tsunemasa

2005-12-01

A near-ultraviolet (UV)-based white light-emitting diode (LED) lighting system linked with a semiconductor InGaN LED and compound phosphors for general lighting applications is proposed. We have developed for the first time a novel type of high-color rendering index (Ra) white LED light source, which is composed of near-UV LED and multiphosphor materials showing orange (O), yellow (Y), green (G), and blue (B) emissions. The white LED shows the superior characteristics of luminous efficacy and high Ra to be about 40 lm/W and 93, respectively. Luminous and chromaticity characteristics, and their spectral distribution of the present white LED can be evaluated using the multipoint LED light source theory. It is revealed that the OYGB white LED can provide better irradiance properties than that of conventional white LEDs. Near-UV white LED technologies, in conjunction with phosphor blends, can offer superior color uniformity, high Ra, and excellent light quality. Consequently we are carrying out a "white LEDs for medical applications" program in the second phase of this national project from 2004 to 2009.

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

NASA Astrophysics Data System (ADS)

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

2014-02-01

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

Lifetime predictions for dimmable two-channel drivers for color tuning luminaires

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davis, Lynn; Smith, Aaron; Clark, Terry

Two-channel tunable white lighting (TWL) systems represent the next wave of solid-state lighting (SSL) systems and promise flexibility in light environment while maintaining the high reliability and luminous efficacy expected with SSL devices. TWL systems utilize LED assemblies consisting of two different LED spectra (i.e., often a warm white assembly and a cool white assembly) that are integrated into modules. While these systems provide the ability to adjust the lighting spectrum to match the physiology needs of the task at hand, they also are a potentially more complex lighting system from a performance and reliability perspective. We report an initialmore » study on the reliability performance of such lighting systems including an examination of the lumen maintenance and chromaticity stability of warm white and cool white LED assemblies and the multi-channel driver that provides power to the assemblies. Accelerated stress tests including operational bake tests conducted at 75°C and 95°C were used to age the LED modules, while more aggressive temperature and humidity tests were used for the drivers in this study. Small differences in the performance between the two LED assemblies were found and can be attributed to the different phosphor chemistries. The lumen maintenances of both LED assemblies were excellent. The warm white LED assemblies were found to shift slightly in the green color direction over time while the cool white LED assemblies shifted slightly in the yellow color direction. The net result of these chromaticity shifts is a small, barely perceptible reduction in the tuning range after 6,000 hours of exposure to an accelerating elevated temperature of 75°C.« less

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilkerson, Andrea; Sullivan, Gregory P.; Davis, Robert G.

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 themore » long-term performance of LED lighting systems in high-temperature environments.« less

Usability of light-emitting diodes in precision approach path indicator systems by individuals with marginal color vision.

DOT National Transportation Integrated Search

2014-05-01

To save energy, the FAA is planning to convert from incandescent lights to light-emitting diodes (LEDs) in : precision approach path indicator (PAPI) systems. Preliminary work on the usability of LEDs by color vision-waivered pilots (Bullough, Skinne...

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

NASA Astrophysics Data System (ADS)

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

2012-11-01

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

RGB LED with smart control in the backlight and lighting

NASA Astrophysics Data System (ADS)

Ku, Johnson C. S.; Lee, C. J.

2008-02-01

To improve the LED (Light Emitting Diode) efficacy is the major consideration when the backlight and lighting system are implemented. An important source of poor efficacy come from the chip process or heat dissipation. White LED used blue chip with phosphor is the current solution and inadequate for the tunable color temperature system. The use of RGB (Red, Green and Blue) LED with smart control is presented in this study. The resulting coupled optical and thermal shows the better performance when it is synthesized in conjunction with a degree of color mixing technology.

A sensor-less LED dimming system based on daylight harvesting with BIPV systems.

PubMed

Yoo, Seunghwan; Kim, Jonghun; Jang, Cheol-Yong; Jeong, Hakgeun

2014-01-13

Artificial lighting in office buildings typically requires 30% of the total energy consumption of the building, providing a substantial opportunity for energy savings. To reduce the energy consumed by indoor lighting, we propose a sensor-less light-emitting diode (LED) dimming system using daylight harvesting. In this study, we used light simulation software to quantify and visualize daylight, and analyzed the correlation between photovoltaic (PV) power generation and indoor illumination in an office with an integrated PV system. In addition, we calculated the distribution of daylight illumination into the office and dimming ratios for the individual control of LED lights. Also, we were able directly to use the electric power generated by PV system. As a result, power consumption for electric lighting was reduced by 40 - 70% depending on the season and the weather conditions. Thus, the dimming system proposed in this study can be used to control electric lighting to reduce energy use cost-effectively and simply.

Multiple LEDs luminous system in capsule endoscope

NASA Astrophysics Data System (ADS)

Mang, Ou-Yang; Huang, Shih-Wei; Lee, Hsin-Hung; Chen, Yung-Lin; Huang, Ko-Chih; Kuo, Yi-Ting

2007-02-01

Developing the luminous system in a capsule endoscope, it is difficult to obtain an uniform illumination[1] on the observed object because of several reasons: the light pattern of LED is sensitively depend on the driving current, location and projective angles; the optical path of LED light source is not parallel to the optical axis of the nearby imaging lenses; the strong reflection from the inner surface of the dome may saturate the CMOS sensors; the object plane of the observed intestine is not flat. Those reasons induce the over-blooming and deep-dark contrast in a picture and distort the original image strongly. The purpose of the article is to construct a photometric model to analyze the LED projection light pattern, and, furthermore, design a novel multiple LEDs luminous system for obtaining an uniform-brightness image. Several key parameters resulting as illumination uniformity has been taken under the model consideration and proven by experimental results. Those parameters include LED light pattern accuracy, choosing LED position relative to the imaging optical axis, LED numbers, arrangement, and the inner curvature of the dome. The novel structure improves the uniformity from 41% to 71% and reduces the light energy loss under 2%. The progress will help medical professionals to diagnose diseases and give treatment precisely based on the vivid image.

Emergency Lighting Technology Evolves To Save Lives.

ERIC Educational Resources Information Center

Gregory, Dennis

2001-01-01

Explores the benefits of including high-brightness Light Emitting Diodes (LEDs) for emergency systems and its use in residence halls. LED emergency lighting options and their qualifications are also highlighted.(GR)

Comparative clinical study using laser and LED-therapy for orofacial pain relief: dentin hypersensitivity and cervicogenic headache

NASA Astrophysics Data System (ADS)

Lizarelli, Rosane F. Z.; Pizzo, Renata C. A.; Florez, Fernando L. E.; Grecco, Clovis; Speciali, Jose G.; Bagnato, Vanderlei S.

2015-06-01

Considering several clinical situations, low intensity laser therapy has been widely applied in pain relief or analgesia mechanism. With the advent of new LED-based (light emitting diode) light sources, the need of further clinical experiments aiming to compare the effectiveness among them is paramount. The LED system therapeutic use can be denominated as LEDT - Light Emitting Diode Therapy. This study proposed two clinical evaluations of pain relief effect: to dentin hypersensitivity and to cervicogenic headache using different sources of lasers (low and high intensity) and light emitting diodes (LEDs), one emitting at the spectral band of red (630+/- 5nm) and the other one at infrared band (880+/- 5nm). Two different clinical studies were performed and presented interesting results. Considering dentin hypersensitivity, red and infrared led were so effective than the control group (high intensity laser system); by the other side, considering cervicogenic headache, control group (infrared laser) was the best treatment in comparison to red and infrared led system.

Effects of blue light on the circadian system and eye physiology.

PubMed

Tosini, Gianluca; Ferguson, Ian; Tsubota, Kazuo

2016-01-01

Light-emitting diodes (LEDs) have been used to provide illumination in industrial and commercial environments. LEDs are also used in TVs, computers, smart phones, and tablets. Although the light emitted by most LEDs appears white, LEDs have peak emission in the blue light range (400-490 nm). The accumulating experimental evidence has indicated that exposure to blue light can affect many physiologic functions, and it can be used to treat circadian and sleep dysfunctions. However, blue light can also induce photoreceptor damage. Thus, it is important to consider the spectral output of LED-based light sources to minimize the danger that may be associated with blue light exposure. In this review, we summarize the current knowledge of the effects of blue light on the regulation of physiologic functions and the possible effects of blue light exposure on ocular health.

Expeditionary Lighting Systems for Military Shelters

DTIC Science & Technology

2009-11-04

Lumiled LED Housing Nonimaging Beamformer Heat Sink Connector Retractable Cable O Transportation Configuration Physical Optics Corporation (POC) LED...New Lighting Technologies: • Technology: Light Emitting Diode (LED) o Physical Optics Corp [SBIR] o Techshot [SBIR] [Congressional Effort o Jameson LED...rugged and durable—no lamp to damage or replace • Custom designed optical diffuser prevents glare and “eye spots” • Operates on universal voltage, 90

Regression analysis for LED color detection of visual-MIMO system

NASA Astrophysics Data System (ADS)

Banik, Partha Pratim; Saha, Rappy; Kim, Ki-Doo

2018-04-01

Color detection from a light emitting diode (LED) array using a smartphone camera is very difficult in a visual multiple-input multiple-output (visual-MIMO) system. In this paper, we propose a method to determine the LED color using a smartphone camera by applying regression analysis. We employ a multivariate regression model to identify the LED color. After taking a picture of an LED array, we select the LED array region, and detect the LED using an image processing algorithm. We then apply the k-means clustering algorithm to determine the number of potential colors for feature extraction of each LED. Finally, we apply the multivariate regression model to predict the color of the transmitted LEDs. In this paper, we show our results for three types of environmental light condition: room environmental light, low environmental light (560 lux), and strong environmental light (2450 lux). We compare the results of our proposed algorithm from the analysis of training and test R-Square (%) values, percentage of closeness of transmitted and predicted colors, and we also mention about the number of distorted test data points from the analysis of distortion bar graph in CIE1931 color space.

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

NASA Astrophysics Data System (ADS)

Do, Trong Hop; Yoo, Myungsik

2018-01-01

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

Effects of melatonin injection or green-wavelength LED light on the antioxidant system in goldfish (Carassius auratus) during thermal stress.

PubMed

Jung, Seo Jin; Choi, Young Jae; Kim, Na Na; Choi, Ji Yong; Kim, Bong-Seok; Choi, Cheol Young

2016-05-01

We tested the mitigating effects of melatonin injections or irradiation from green-wavelength light-emitting diodes (LEDs) on goldfish (Carassius auratus) exposed to thermal stress (high water temperature, 30 °C). The effects of the two treatments were assessed by measuring the expression and activity levels of the antioxidant enzymes, superoxide dismutase and catalase, plasma hydrogen peroxide, lipid hydroperoxide, and lysozyme. In addition, a comet assay was conducted to confirm that high water temperature damaged nuclear DNA. The expression and activity of the antioxidant enzymes, plasma hydrogen peroxide, and lipid hydroperoxide were significantly higher after exposure to high temperature and were significantly lower in fish that received melatonin or LED light than in those that received no mitigating treatment. Plasma lysozyme was significantly lower after exposure to high temperature and was significantly higher after exposure to melatonin or LED light. The comet assay revealed that thermal stress caused a great deal of damage to nuclear DNA; however, treatment with melatonin or green-wavelength LED light prevented a significant portion of this damage from occurring. These results indicate that, although high temperatures induce oxidative stress and reduce immune system strength in goldfish, both melatonin and green-wavelength LED light inhibit oxidative stress and boost the immune system. LED treatment increased the antioxidant and immune system activity more significantly than did melatonin treatment. Copyright © 2016 Elsevier Ltd. All rights reserved.

Feasibility of light-emitting diode uses for annular reactor inner-coated with TiO2 or nitrogen-doped TiO2 for control of dimethyl sulfide.

PubMed

Jo, Wan-Kuen; Eun, Sung-Soo; Shin, Seung-Ho

2011-01-01

Limited environmental pollutants have only been investigated for the feasibility of light-emitting diodes (LED) uses in photocatalytic decomposition (PD). The present study investigated the applicability of LEDs for annular photocatalytic reactors by comparing PD efficiencies of dimethyl sulfide (DMS), which has not been investigated with any LED-PD system, between photocatalytic systems utilizing conventional and various LED lamps with different wavelengths. A conventional 8 W UV/TiO(2) system exhibited a higher DMS PD efficiency as compared with UV-LED/TiO(2) system. Similarly, a conventional 8 W visible-lamp/N-enhanced TiO(2) (NET) system exhibited a higher PD efficiency as compared with six visible-LED/NET systems. However, the ratios of PD efficiency to the electric power consumption were rather high for the photocatalytic systems using UV- or visible-LED lamps, except for two LED lamps (yellow- and red-LED lamps), compared to the photocatalytic systems using conventional lamps. For the photocatalytic systems using LEDs, lower flow rates and input concentrations and shorter hydraulic diameters exhibited higher DMS PD efficiencies. An Fourier-transformation infrared analysis suggested no significant absorption of byproducts on the catalyst surface. Consequently, it was suggested that LEDs can still be energy-efficiently utilized as alternative light sources for the PD of DMS, under the operational conditions used in this study. © 2011 The Authors. Photochemistry and Photobiology © 2011 The American Society of Photobiology.

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

PubMed

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.

The benefits of future-proof tunable white lighting in the classroom

DOE PAGES

Clark, Terry

2016-11-21

The biggest challenge affecting lighting decisions today is future-proofing. Choices made today will likely be choices that impact the next 20 or perhaps even 40 years. For example, we can expect the best LED lighting available today to maintain 90% of initial light output for 100,000 hours or more. Compare this to a fluorescent lighting system that needs regular maintenance after only 30,000 hours due to lamp burn-outs. The simple act of choosing a LED system over a fluorescent one alone can begin to reduce life cycle costs by saving future maintenance costs. However, the choice of LED over fluorescentmore » is just the beginning. Here, let’s look at other future-proofing decisions that should be considered when choosing your next lighting system.« less

Open-source products for a lighting experiment device.

PubMed

Gildea, Kevin M; Milburn, Nelda

2014-12-01

The capabilities of open-source software and microcontrollers were used to construct a device for controlled lighting experiments. The device was designed to ascertain whether individuals with certain color vision deficiencies were able to discriminate between the red and white lights in fielded systems on the basis of luminous intensity. The device provided the ability to control the timing and duration of light-emitting diode (LED) and incandescent light stimulus presentations, to present the experimental sequence and verbal instructions automatically, to adjust LED and incandescent luminous intensity, and to display LED and incandescent lights with various spectral emissions. The lighting device could easily be adapted for experiments involving flashing or timed presentations of colored lights, or the components could be expanded to study areas such as threshold light perception and visual alerting systems.

A comparative study of fluorescent and LED lighting in industrial facilities

NASA Astrophysics Data System (ADS)

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

2018-05-01

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

The potential influence of LED lighting on mental illness.

PubMed

Bauer, Michael; Glenn, Tasha; Monteith, Scott; Gottlieb, John F; Ritter, Philipp S; Geddes, John; Whybrow, Peter C

2018-02-01

Two recent scientific breakthroughs may alter the treatment of mental illness, as discussed in this narrative review. The first was the invention of white light-emitting diodes (LEDs), which enabled an ongoing, rapid transition to energy-efficient LEDs for lighting, and the use of LEDs to backlight digital devices. The second was the discovery of melanopsin-expressing photosensitive retinal ganglion cells, which detect environmental irradiance and mediate non-image forming (NIF) functions including circadian entrainment, melatonin secretion, alertness, sleep regulation and the pupillary light reflex. These two breakthroughs are interrelated because unlike conventional lighting, white LEDs have a dominant spectral wavelength in the blue light range, near the peak sensitivity for the melanopsin system. Pertinent articles were identified. Blue light exposure may suppress melatonin, increase alertness, and interfere with sleep in young, healthy volunteers and in animals. Areas of concern in mental illness include the influence of blue light on sleep, other circadian-mediated symptoms, prescribed treatments that target the circadian system, measurement using digital apps and devices, and adolescent sensitivity to blue light. While knowledge in both fields is expanding rapidly, future developments must address the potential impact of blue light on NIF functions for healthy individuals and those with mental illness.

Application of the light emitting diodes (LEDs) in optical measurements

NASA Astrophysics Data System (ADS)

Sabinin, Vladimir E.; Savelyev, Sergey K.; Solk, Sergey V.

2003-06-01

At current moment the Light Emitting Diodes (LED) have found a great amount of applications in different areas -- for location and communication systems, optical information systems, in architecture light decoration and advertising, traffic signals, etc. In current work we are making attempt to analyze some new possible fields of LED application. Among these may be build in systems of photometry control. Many different optic and optoelectronic systems are in need of such devices, able to operate for a long time in an autonomous regime. LED's and especially optocouples on their base can provide required time stability and spectral characteristics. The main drawback of such elements is the particularity of the emission diagram. In many case it has unpredictable form, but high reliability and very simple design may compensate many of LED's drawbacks. Below are analyzed the optical schemes enabling transformation of the semiconductor crystal in visible and IR ranges into the beams with angular divergence of 2 degrees. From one crystal, having diameter less than 1 mm was gained the axial light power exceeding 1000 cd and it is possible to form the light sources providing light power up to 50 - 100 W/str. If to take into account that LED have narrow spectral band and high stability of this spectral band, their small dimensions, rather high efficiency, a possibility of intensity modulation by supply current it is very promising to apply these devices for system of buid in control. Such possibility was not realized in full up till now.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clark, Terry

The biggest challenge affecting lighting decisions today is future-proofing. Choices made today will likely be choices that impact the next 20 or perhaps even 40 years. For example, we can expect the best LED lighting available today to maintain 90% of initial light output for 100,000 hours or more. Compare this to a fluorescent lighting system that needs regular maintenance after only 30,000 hours due to lamp burn-outs. The simple act of choosing a LED system over a fluorescent one alone can begin to reduce life cycle costs by saving future maintenance costs. However, the choice of LED over fluorescentmore » is just the beginning. Here, let’s look at other future-proofing decisions that should be considered when choosing your next lighting system.« less

Development of Radiation-Resistant In-Water Wireless Transmission System Using Light Emitting Diodes and Photo Diodes

NASA Astrophysics Data System (ADS)

Takeuchi, T.; Shibata, H.; Otsuka, N.; Uehara, T.; Tsuchiya, K.; Shibagaki, T.; Komanome, H.

2016-10-01

Several kinds of commercially available light emitting diodes (LED) and photo diodes (PD) were irradiated with 60Co gamma ray up to 1 MGy for development of a radiation-resistant in-water wireless transmission system using visible light. The lens parts of the LEDs turned brown by the irradiation and their colors became dark with the absorbed dose. The total luminous fluxes decreased with the absorbed dose and the LED with shorter emission wavelength had the higher decrease rate. Meanwhile, the current-voltage characteristics hardly changed. These results indicate that the decreases of the total luminous flux of the LEDs were mainly caused not by the degradation of the semiconductor parts but by the coloring of the lens parts by the irradiation. On the other hand, the light sensitivities of the PDs decreased with the absorbed dose. The PDs with the window part which turned a darker color had the higher decrease rate. These results indicate that the decreases of light sensitivities of the PDs were also mainly caused by the coloring of the resin parts by the irradiation. If the wireless transmission is performed using the candidate LED and PD between 5 meters in water, using a few LEDs and PDs, the PD's output current generated by the emission light of the LED is estimated to be detectable even considering the effects of the absorption of the light in water and the increased dark current by the irradiation. Therefore, a radiation resistant in-water transmission system can be constructed using commercially available LEDs and PDs in principle.

Longitudinal useful life analysis and replacement strategies for LED traffic indicators.

DOT National Transportation Integrated Search

2014-04-01

The application of Light Emitting Diode (LED) lighting systems has experienced significant gro : wth in the transportation : sector over the past : ten : years. LED indication lifespans have significantly greater durations than previous technologies,...

Longitudinal useful life analysis and replacement strategies for LED traffic indicators.

DOT National Transportation Integrated Search

2014-04-01

The application of Light Emitting Diode (LED) lighting systems has experienced significant growth in : the transportation sector over the past 10 years. LED indication lifespans have significantly greater durations than : previous technologies, howev...

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davis, Robert G.; Wilkerson, Andrea M.; Samla, Connie

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

Investigation of uniformity field generated from freeform lens with UV LED exposure system

NASA Astrophysics Data System (ADS)

Ciou, F. Y.; Chen, Y. C.; Pan, C. T.; Lin, P. H.; Lin, P. H.; Hsu, F. T.

2015-03-01

In the exposure process, the intensity and uniformity of light in the exposure area directly influenced the precision of products. UV-LED (Ultraviolet Light-Emitting Diode) exposure system was established to reduce the radiation leakage and increase the energy efficiency for energy saving. It is a trend that conventional mercury lamp could be replaced with UV-LED exposure system. This study was based on the law of conservation of energy and law of refraction of optical field distributing on the target plane. With these, a freeform lens with uniform light field of main exposure area could be designed. The light outside the exposure area could be concentrated into the area to improve the intensity of light. The refraction index and UV transmittance of Polydimethylsiloxane (PDMS) is 1.43 at 385 nm wavelength and 85-90%, respectively. The PDMS was used to fabricate the optics lens for UV-LEDs. The average illumination and the uniformity could be obtained by increasing the number of UV-LEDs and the spacing of different arrangement modes. After exposure process with PDMS lens, about 5% inaccuracy was obtained. Comparing to 10% inaccuracy of general exposure system, it shows that it is available to replace conventional exposure lamp with using UV-LEDs.

Shear bond strength of a bracket-bonding system cured with a light-emitting diode or halogen-based light-curing unit at various polymerization times

PubMed Central

Gupta, Sanjay Prasad; Shrestha, Basanta Kumar

2018-01-01

Purpose To determine and compare the shear bond strength (SBS) of bracket-bonding system cured with light-emitting diode (LED) and halogen-based light-curing unit at various polymerization times. Materials and methods Ninety six human maxillary premolar teeth extracted for orthodontic purpose were divided into four groups, according to the light-curing unit and exposure times used. In the halogen group, the specimens were light cured for 20 and 40 seconds. In the LED group, the specimens were light cured for 5 and 10 seconds. Stainless steel brackets were bonded with Enlight bonding system, stored in distilled water at 37°C for 24 hours and then submitted to SBS testing in a universal testing machine at a crosshead speed of 0.5 mm/minute. Adhesive remnant index (ARI) was used to evaluate the amount of adhesive remaining on the teeth determined by stereomicroscope at 10× magnification. Results The highest mean SBS was obtained with the halogen 40 seconds (18.27 MPa) followed by halogen 20 seconds (15.36 MPa), LED 10 seconds (14.60 MPa) and least with LED 5 seconds (12.49 MPa) group. According to analysis of variance (ANOVA) and Tukey’s multiple-comparison test, SBS of halogen 20 seconds group was not significantly different from halogen 40 seconds group, LED 5 seconds group and LED 10 seconds group, whereas halogen 40 seconds group was significantly different from LED 5 seconds and LED 10 seconds group. The method of light curing did not influence the ARI, with score 2 being predominant. Conclusion Polymerization with both halogen and LED resulted in SBS values that were clinically acceptable for orthodontic treatment in all groups. Hence, for bonding orthodontic brackets, photoactivation with halogen for 20 seconds and LED for 5 seconds is suggested. PMID:29692633

Effects of blue light on the circadian system and eye physiology

PubMed Central

Ferguson, Ian; Tsubota, Kazuo

2016-01-01

Light-emitting diodes (LEDs) have been used to provide illumination in industrial and commercial environments. LEDs are also used in TVs, computers, smart phones, and tablets. Although the light emitted by most LEDs appears white, LEDs have peak emission in the blue light range (400–490 nm). The accumulating experimental evidence has indicated that exposure to blue light can affect many physiologic functions, and it can be used to treat circadian and sleep dysfunctions. However, blue light can also induce photoreceptor damage. Thus, it is important to consider the spectral output of LED-based light sources to minimize the danger that may be associated with blue light exposure. In this review, we summarize the current knowledge of the effects of blue light on the regulation of physiologic functions and the possible effects of blue light exposure on ocular health. PMID:26900325

Modular, Microprocessor-Controlled Flash Lighting System

NASA Technical Reports Server (NTRS)

Kiefer, Dwayne; Gray, Elizabeth; Skupinski, Robert; Stachowicz, Arthur; Birchenough, William

2006-01-01

A microprocessor-controlled lighting system generates brief, precisely timed, high-intensity flashes of light for scientific imaging at frame rates up to about 1 kHz. The system includes an array of light-emitting diodes (LEDs) that are driven in synchronism with an externally generated timing signal (for example, a timing signal generated by a video camera). The light output can be varied in peak intensity, pulse duration, pulse delay, and pulse rate, all depending on the timing signal and associated externally generated control signals. The array of LEDs comprises as many as 16 LED panels that can be attached together. Each LED panel is a module consisting of a rectangular subarray of 10 by 20 LEDs of advanced design on a printed-circuit board in a mounting frame with a power/control connector. The LED panels are controlled by an LED control module that contains an AC-to-DC power supply, a control board, and 8 LED-panel driver boards. In prior LED panels, the LEDs are packaged at less than maximum areal densities in bulky metal housings that reduce effective active areas. In contrast, in the present LED panels, the LEDs are packed at maximum areal density so as to afford 100-percent active area and so that when panels are joined side by side to form the array, there are no visible seams between them and the proportion of active area is still 100 percent. Each panel produces an illuminance of .5 x 10( exp 4) lux at a distance of 5.8 in. (approx.1.6 cm). The LEDs are driven according to a pulse-width-modulation control scheme that makes it safe to drive the LEDs beyond their rated steady-state currents in order to generate additional light during short periods. The drive current and the pulse-width modulation for each LED panel can be controlled independently of those of the other 15 panels. The maximum allowable duration of each pulse of drive current is a function of the amount of overdrive, the total time to be spent in overdrive operation, and the limitations of the LEDs. The system is configured to limit the overdrive according to values specific to each type of LED in the array. These values are coded into firmware to prevent inadvertent damage to the LED panels.

Commerical Transition to LEDs: A Pathway to High-Value Products

NASA Technical Reports Server (NTRS)

Stutte, Gary W.

2015-01-01

The use of light-emitting diodes (LEDs) to support plant growth is a radical departure from use of gas-discharge lamps, which were developed in mid-19th and widely adopted by the industry during the 20th century. Initial investigation by the National Aeronautics and Space Administration (NASA) in the late 1980s on the use of LEDs to grow plant in space is resulting in an industry-wide transition from gas discharge to solid-state lighting systems. This global transformation is given urgency by national policies to reduce energy consumption and being facilitated by ready access to information on LEDs. The combination of research, government policy, and information technology has resulted in an exponential increase in research into the use and application of LED technology in horticulture. Commercial horticulture has identified the opportunities provided by LEDs to optimize light spectra to promote growth, regulate morphology, increase nutrient content, and reduce operating costs. LED-light technology is enabling the development of innovative lighting systems, and is being incorporated into large-scale plant factories for the production of edible, ornamental, and medicinal plants. An overview of prevalence of readily accessible information on LEDs and implications for future adoption in horticulture is discussed.

LIGHT-EMITTING DIODE TECHNOLOGY IMPROVES INSECT TRAPPING

PubMed Central

GILLEN, JONATHON I.; MUNSTERMANN, LEONARD E.

2008-01-01

In a climate of increased funding for vaccines, chemotherapy, and prevention of vector-borne diseases, fewer resources have been directed toward improving disease and vector surveillance. Recently developed light-emitting diode (LED) technology was applied to standard insect-vector traps to produce a more effective lighting system. This approach improved phlebotomine sand fly capture rates by 50%, and simultaneously reduced the energy consumption by 50–60%. The LEDs were incorporated into 2 lighting designs, 1) a LED combination bulb for current light traps and 2) a chip-based LED design for a modified Centers for Disease Control and Prevention light trap. Detailed descriptions of the 2 designs are presented. PMID:18666546

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

NASA Astrophysics Data System (ADS)

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.

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

NASA Astrophysics Data System (ADS)

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

2006-08-01

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

Sensitivity enhancement of fluorescence detection in CE by coupling and conducting excitation light with tapered optical fiber.

PubMed

Yang, Xiupei; Huo, Feng; Yuan, Hongyan; Zhang, Bo; Xiao, Dan; Choi, Martin M F

2011-01-01

This paper reports the enhancement of sensitivity of detection for in-column fiber optic-induced fluorescence detection system in CE by tapered optical fiber (TOF). Two types of optical fiber, TOF and conventional cylindrical optical fiber (COF), were employed to construct the CE (TOF-CE and COF-CE) and were compared for sensitivity to riboflavin (RF). The fluorescence intensities from a RF sample with excitation light sources and fibers at various coupling angles were investigated. The fluorescence signal from TOF-CE was ca. ten times that of COF-CE. In addition, the detection performance of four excitation light source-fiber configurations including Laser-TOF, Laser-COF, LED-TOF, and LED-COF were compared. The LODs for RF were 0.21, 0.82, 0.80, and 7.5 nM, respectively, for the four excitation light source-fiber configurations. The results demonstrate that the sensitivity obtained by LED-TOF is close to that of Laser-COF. Both Laser-TOF and LED-TOF can greatly improve the sensitivity of detection in CE. TOF has the major attribute of collecting and focusing the excitation light intensity. Thus, the sensitivity obtained by LED-TOF without focusing lens is just same as that of LED-COF with a focusing lens. This demonstrates that the CE system can be further simplified by eliminating the focusing lens for excitation light. LED-TOF-CE and LED-COF-CE system were applied to the separation and determination of RF in real sample (green tea), respectively. The tapered fiber optic-induced fluorescence detection system in CE is an ideal tool for trace analysis. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Linear CCD attitude measurement system based on the identification of the auxiliary array CCD

NASA Astrophysics Data System (ADS)

Hu, Yinghui; Yuan, Feng; Li, Kai; Wang, Yan

2015-10-01

Object to the high precision flying target attitude measurement issues of a large space and large field of view, comparing existing measurement methods, the idea is proposed of using two array CCD to assist in identifying the three linear CCD with multi-cooperative target attitude measurement system, and to address the existing nonlinear system errors and calibration parameters and more problems with nine linear CCD spectroscopic test system of too complicated constraints among camera position caused by excessive. The mathematical model of binocular vision and three linear CCD test system are established, co-spot composition triangle utilize three red LED position light, three points' coordinates are given in advance by Cooperate Measuring Machine, the red LED in the composition of the three sides of a triangle adds three blue LED light points as an auxiliary, so that array CCD is easier to identify three red LED light points, and linear CCD camera is installed of a red filter to filter out the blue LED light points while reducing stray light. Using array CCD to measure the spot, identifying and calculating the spatial coordinates solutions of red LED light points, while utilizing linear CCD to measure three red LED spot for solving linear CCD test system, which can be drawn from 27 solution. Measured with array CCD coordinates auxiliary linear CCD has achieved spot identification, and has solved the difficult problems of multi-objective linear CCD identification. Unique combination of linear CCD imaging features, linear CCD special cylindrical lens system is developed using telecentric optical design, the energy center of the spot position in the depth range of convergence in the direction is perpendicular to the optical axis of the small changes ensuring highprecision image quality, and the entire test system improves spatial object attitude measurement speed and precision.

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

PubMed Central

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

2016-01-01

Present study introduced a new method to manipulate broiler chicken growth and metabolism by mixing the growth-advantage LED. We found that the green/blue LED mixed light system (G-B and G × B) have the similar stimulatory effect on chick body weight with single green light and single blue light (G and B), compared with normal artificial light (P = 0.028). Moreover, the percentage of carcass was significantly greater in the mixed light (G × B) when compared with the single light (P = 0.003). Synchronized with body weight, the mixed light (G-B and G × B) had a significant improved influence on the feed conversion of birds compared with normal light (P = 0.002). A significant improvement in feed conversion were found in mixed light (G × B) compared with single LED light (P = 0.037). G group resulted in a greater high-density lipoprotein cholesterol level than B group (P = 0.002), whereas B group resulted in a greater low-density lipoprotein cholesterol level than G group (P = 0.017). The mixed light significantly increased the birds’ glucose level in comparison with the single light (P = 0.003). This study might establish an effective strategy for maximizing growth of chickens by mixed LED technology. PMID:27170597

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

PubMed

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

2016-05-12

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

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

NASA Astrophysics Data System (ADS)

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

2016-05-01

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

Adapting radio technology to LED feedback systems

NASA Astrophysics Data System (ADS)

Salsbury, Marc; Ashdown, Ian

2007-09-01

Superheterodyne techniques were originally developed for radio transmission and reception nearly a century ago. In this paper we explore the adaptation of this technology to the problem of simultaneously monitoring the intensities of multiple LED channels with a single photosensor. The use of superheterodyne techniques obviates the need for multiple photosensors filters and tristimulus color filters to monitor the relative intensities of red, green, and blue LEDs. In addition, they alleviate the problems of electrical and optical noise, as well as the influence of ambient illumination on the photosensors. They can also be used to advantage with phosphor-coated white light LEDs in solid state lighting systems. Taking a broader view, the use of such techniques demonstrates the value of looking outside the realm of conventional LED power and control technologies when designing solid state lighting systems.

Progress in extremely high brightness LED-based light sources

NASA Astrophysics Data System (ADS)

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.

An inter-lighting interference cancellation scheme for MISO-VLC systems

NASA Astrophysics Data System (ADS)

Kim, Kyuntak; Lee, Kyujin; Lee, Kyesan

2017-08-01

In this paper, we propose an inter-lighting interference cancellation (ILIC) scheme to reduce the interference between adjacent light-emitting diodes (LEDs) and enhance the transmission capacity of multiple-input-single-output (MISO)-visible light communication (VLC) systems. In indoor environments, multiple LEDs have normally been used as lighting sources, allowing the design of MISO-VLC systems. To enhance the transmission capacity, different data should be simultaneously transmitted from each LED; however, that can lead to interference between adjacent LEDs. In that case, relatively low-received power signals are subjected to large interference because wireless optical systems generally use intensity modulation and direct detection. Thus, only the signal with the highest received power can be detected, while the other received signals cannot be detected. To solve this problem, we propose the ILIC scheme for MISO-VLC systems. The proposed scheme preferentially detects the highest received power signal, and this signal is referred as interference signal by an interference component generator. Then, relatively low-received power signal can be detected by cancelling the interference signal from the total received signals. Therefore, the performance of the proposed scheme can improve the total average bit error rate and throughput of a MISO-VLC system.

Photomorphogenesis, photosynthesis, and seed yield of wheat plants grown under red light-emitting diodes (LEDs) with and without supplemental blue lighting

NASA Technical Reports Server (NTRS)

Goins, G. D.; Yorio, N. C.; Sanwo, M. M.; Brown, C. S.; Sager, J. C. (Principal Investigator)

1997-01-01

Red light-emitting diodes (LEDs) are a potential light source for growing plants in spaceflight systems because of their safety, small mass and volume, wavelength specificity, and longevity. Despite these attractive features, red LEDs must satisfy requirements for plant photosynthesis and photomorphogenesis for successful growth and seed yield. To determine the influence of gallium aluminium arsenide (GaAlAs) red LEDs on wheat photomorphogenesis, photosynthesis, and seed yield, wheat (Triticum aestivum L., cv. 'USU-Super Dwarf') plants were grown under red LEDs and compared to plants grown under daylight fluorescent (white) lamps and red LEDs supplemented with either 1% or 10% blue light from blue fluorescent (BF) lamps. Compared to white light-grown plants, wheat grown under red LEDs alone demonstrated less main culm development during vegetative growth through preanthesis, while showing a longer flag leaf at 40 DAP and greater main culm length at final harvest (70 DAP). As supplemental BF light was increased with red LEDs, shoot dry matter and net leaf photosynthesis rate increased. At final harvest, wheat grown under red LEDs alone displayed fewer subtillers and a lower seed yield compared to plants grown under white light. Wheat grown under red LEDs+10% BF light had comparable shoot dry matter accumulation and seed yield relative to wheat grown under white light. These results indicate that wheat can complete its life cycle under red LEDs alone, but larger plants and greater amounts of seed are produced in the presence of red LEDs supplemented with a quantity of blue light.

Theoretical and experimental luminous characteristics of white LEDs composed of multiphosphors and near-UV LED for lighting

NASA Astrophysics Data System (ADS)

Uchida, Yuji; Taguchi, Tsunemasa

2003-07-01

We have performed theoretical studies on the luminous characeristics of white LED light source which composed of multi phosphors and near ultraviolet (UV) LED for general lighting. White LED source for general lighting applications requires the conditions that have high-flux, high luminous efficacy of radiation (> 100 lm/W) in addition to high color rendering index (Ra > 90) and variable color temperatures. Recently, we have proposed a novel type white LED based on multi phosphors and near UV LED system in order to high-Ra (>93). We will describe the excellent luminescence properties of white LED consisting of orange (O), yellow (Y), green (G) and blue (B) phosphor materials, and near UV LED. The color spectral contributions of individual phosphor-coated LED are theoretically analyzed using our multi LED lighting theory calculated the maximum luminous efficacy can be estimated to be approximately 300 lm/W having a high Ra of about 90 taking into account individual radiation spectrum. Illuminance distribution of white LED is in fairly good agreement with the experimental data.

LED Context Lighting System in Residential Areas

PubMed Central

Im, Kyoung-Mi

2014-01-01

As issues of environment and energy draw keen interest around the globe due to such problems as global warming and the energy crisis, LED with high optical efficiency is brought to the fore as the next generation lighting. In addition, as the national income level gets higher and life expectancy is extended, interest in the enhancement of life quality is increasing. Accordingly, the trend of lightings is changing from mere adjustment of light intensity to system lighting in order to enhance the quality of one's life as well as reduce energy consumption. Thus, this study aims to design LED context lighting system that automatically recognizes the location and acts of a user in residential areas and creates an appropriate lighting environment. The proposed system designed in this study includes three types of processing: first, the creation of a lighting environment index suitable for the user's surroundings and lighting control scenarios and second, it measures and analyzes the optical characteristics that change depending on the dimming control of lighting and applies them to the index. Lastly, it adopts PIR, piezoelectric, and power sensor to grasp the location and acts of the user and create a lighting environment suitable for the current context. PMID:25101325

Evaluating white LEDs for outdoor landscape lighting application

NASA Astrophysics Data System (ADS)

Shakir, Insiya; Narendran, Nadarajah

2002-11-01

A laboratory experiment was conducted to understand the acceptability of different white light emitting diodes (LEDs) for outdoor landscape lighting. The study used a scaled model setup. The scene was designed to replicate the exterior of a typical upscale suburban restaurant including the exterior facade of the building, an approach with steps, and a garden. The lighting was designed to replicate light levels commonly found in nighttime outdoor conditions. The model had a central dividing partition with symmetrical scenes on both sides for side-by-side evaluations of the two scenes with different light sources. While maintaining equal luminance levels and distribution between the two scenes, four types of light sources were evaluated. These include, halogen, phosphor white LED, and two white light systems using RGB LEDs. These light sources were tested by comparing two sources at a time placed side-by-side and by individual assessment of each lighting condition. The results showed that the RGB LEDs performed equal or better than the most widely used halogen light source in this given setting. A majority of the subjects found slightly dimmer ambient lighting to be more typical for restaurants and therefore found RGB LED and halogen light sources to be more inviting. The phosphor white LEDs made the space look brighter, however a majority of the subjects disliked them.

Dome diagnostics system of optical parameters and characteristics of LEDs

NASA Astrophysics Data System (ADS)

Peretyagin, Vladimir S.; Pavlenko, Nikita A.

2017-09-01

Scientific and technological progress of recent years in the production of the light emitting diodes (LEDs) has led to the expansion of areas of their application from the simplest systems to high precision lighting devices used in various fields of human activity. However, development and production (especially mass production) of LED lighting devices are impossible without a thorough analysis of its parameters and characteristics. There are many ways and devices for analysis the spatial, energy and colorimetric parameters of LEDs. The most methods are intended for definition only one parameter (for example, luminous flux) or one characteristic (for example, the angular distribution of energy or the spectral characteristics). Besides, devices used these methods are intended for measuring parameters in only one point or plane. This problem can be solved by using a dome diagnostics system of optical parameters and characteristics of LEDs, developed by specialists of the department OEDS chair of ITMO University in Russia. The paper presents the theoretical aspects of the analysis of LED's spatial (angular), energy and color parameters by using mentioned of diagnostics system. The article also presents the results of spatial), energy and color parameters measurements of some LEDs brands.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

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

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davis, Robert G.; Wilkerson, Andrea

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

Influence of reverse bias on the LEDs properties used as photo-detectors in VLC systems

NASA Astrophysics Data System (ADS)

Kowalczyk, Marcin; Siuzdak, Jerzy

2015-09-01

Continuous increasing share of light emitting diodes (LEDs) in a lighting market, which we observe during the last couple years, opens new possibilities. Especially, when we talk about practical realization the concept of visible light communications (VLC), which gains on popularity recently. The VLC concept presupposes utilization of illumination systems for a purpose of data transmission. It means, the emitters, in this case the LEDs, will not of a light source only, but also the data transmitters. Currently, most of the conducted researches in this area is concentrated on achievement of effective transmission methods. It means a transmission only in one direction. This is not enough, when we talk about the fully functional transmission system. Ensuring of feedback transmission channel is a necessary also. One of the ideas, which was postulated by authors of this article, is using for this purpose the LEDs in a double role. A utilization of LEDs as photo-detectors requires a reverse polarization, in contrast to a forward bias, which has a place when they work as light emitters. Ensuring of proper polarization get significant meaning. The article presents the investigations results on the influence of reverse bias on photo-receiving properties of LEDs used as light detectors. The conducted research proved that an improvement of sensitivity and bandwidth parameters are possible by application of appropriate value of the reverse voltage in a receiver.

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

NASA Astrophysics Data System (ADS)

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

In controlled-environment crop production such as will be practiced at the lunar outpost and Mars base, the single most energy-demanding aspect is electric lighting for plant growth, including energy costs for energizing lamps as well as for removing excess heat. For a variety of reasons, sunlight may not be a viable option as the main source of crop lighting off-Earth and traditional electric lamps for crop lighting have numerous drawbacks for use in a space environment. A collaborative research venture between the Advanced Life Support Crops Group at Purdue University and the Orbital Technologies Corporation (ORBITEC) has led to the development of efficient, reconfigurable LED lighting technologies for crop growth in an ALSS. The light sources use printed-circuit red and blue LEDs, which are individually tunable for a range of photosynthetic photon fluxes and photomorphogenic plant responses. Initial lighting arrays have LEDs that can be energized from the bottom upward when deployed in a vertical, intracanopy configuration, allowing the illumination to be tailored for stand height throughout the cropping cycle. Preliminary testing with the planophile crop cowpea (Vigna unguiculata L. Walp, breeding line IT87D-941-1), resulted in optimizing internal reflectance of growth compartments by lining walls, floor, and a movable ceiling with white Poly film, as well as by determining optimal planting density and plant positioning. Additionally, these light strips, called "lightsicles", can be configured into an overhead plane of light engines. When intracanopy and overhead-LED-lit cowpea crop production was compared, cowpea plants grown with intracanopy lighting had much greater understory leaf retention and produced more dry biomass per kilowatt-hour of lighting energy than did overhead-lit plants. The efficiency of light capture is reduced in overhead-lit scenarios due to mutual shading of lower leaves by upper leaves in closed canopies leading to premature abscission of lower leaves. One system modification has led to lightsicles of different lengths, allowing a wider array of intracanopy lighting configurations. Another development is an adaptive system in which each light engine can be operated independently, and photodiodes can detect reflectance patterns off of leaves from flashing green LEDs, thereby indicating positions of leaves within the foliar canopy relative to any given light engine on a lightsicle. When this advanced hardware is coupled to tailored software, the reflectance can be used to auto-detect changes in plant growth and adjust the lighting accordingly. These lighting systems have been tested with cowpea, pepper (Capsicum annuum L. cv. Triton) and Lettuce (Lactuca sativa L. cv. Waldmanns Green) with limited testing of other ALS candidate crop species. The versatility of these LED lighting systems will allow energy-efficient light delivery to a wide variety of crops with different growth habits, including planophile, erectophile, and rosette species. This research has been supported by NASA grants NAG5-12686 (NSCORT) and NNK05OA20C (SBIR Phase 1) and NNK06OM01C (SBIR Phase 2).

A Probability-Based Algorithm Using Image Sensors to Track the LED in a Vehicle Visible Light Communication System.

PubMed

Huynh, Phat; Do, Trong-Hop; Yoo, Myungsik

2017-02-10

This paper proposes a probability-based algorithm to track the LED in vehicle visible light communication systems using a camera. In this system, the transmitters are the vehicles' front and rear LED lights. The receivers are high speed cameras that take a series of images of the LEDs. ThedataembeddedinthelightisextractedbyfirstdetectingthepositionoftheLEDsintheseimages. Traditionally, LEDs are detected according to pixel intensity. However, when the vehicle is moving, motion blur occurs in the LED images, making it difficult to detect the LEDs. Particularly at high speeds, some frames are blurred at a high degree, which makes it impossible to detect the LED as well as extract the information embedded in these frames. The proposed algorithm relies not only on the pixel intensity, but also on the optical flow of the LEDs and on statistical information obtained from previous frames. Based on this information, the conditional probability that a pixel belongs to a LED is calculated. Then, the position of LED is determined based on this probability. To verify the suitability of the proposed algorithm, simulations are conducted by considering the incidents that can happen in a real-world situation, including a change in the position of the LEDs at each frame, as well as motion blur due to the vehicle speed.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davis, Robert G.; Wilkerson, Andrea M.

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

Effects of colored light-emitting diode illumination on behavior and performance of laying hens.

PubMed

Huber-Eicher, B; Suter, A; Spring-Stähli, P

2013-04-01

The best method for lighting poultry houses has been an issue for many decades, generating much interest in any new systems that become available. Poultry farmers are now increasingly using colored LED (light-emitting diodes) to illuminate hen houses (e.g., in Germany, Austria, the Netherlands, and England). In Switzerland all newly installed systems are now equipped with LED, preferably green ones. The LED give monochromatic light from different wavelengths and have several advantages over conventional illuminants, including high energy efficiency, long life, high reliability, and low maintenance costs. The following study examines the effects of illumination with white, red, and green LED on behavior and production parameters of laying hens. Light intensities in the 3 treatments were adjusted to be perceived by hens as equal. Twenty-four groups of 25 laying hens were kept in identical compartments (5.0 × 3.3 m) equipped with a litter area, raised perches, feed and drinking facilities, and nest boxes. Initially, they were kept under white LED for a 2-wk adaptation period. For the next 4 wk, 8 randomly chosen compartments were lit with red LED (640 nm) and 8 others with green LED (520 nm). Behavior was monitored during the last 2 wk of the trial. Additionally weight gain, feed consumption, onset of lay, and laying performance were recorded. The results showed minor effects of green light on explorative behavior, whereas red light reduced aggressiveness compared with white light. The accelerating effect of red light on sexual development of laying hens was confirmed, and the trial demonstrated that this effect was due to the specific wavelength and not the intensity of light. However, an additional effect of light intensity may exist and should not be excluded.

Skyglow changes over Tucson, Arizona, resulting from a municipal LED street lighting conversion

NASA Astrophysics Data System (ADS)

Barentine, John C.; Walker, Constance E.; Kocifaj, Miroslav; Kundracik, František; Juan, Amy; Kanemoto, John; Monrad, Christian K.

2018-06-01

The transition from earlier lighting technologies to white light-emitting diodes (LEDs) is a significant change in the use of artificial light at night. LEDs emit considerably more short-wavelength light into the environment than earlier technologies on a per-lumen basis. Radiative transfer models predict increased skyglow over cities transitioning to LED unless the total lumen output of new lighting systems is reduced. The City of Tucson, Arizona (U.S.), recently converted its municipal street lighting system from a mixture of fully shielded high- and low-pressure sodium (HPS/LPS) luminaires to fully shielded 3000 K white LED luminaires. The lighting design intended to minimize increases to skyglow in order to protect the sites of nearby astronomical observatories without compromising public safety. This involved the migration of over 445 million fully shielded HPS/LPS lumens to roughly 142 million fully shielded 3000 K white LED lumens and an expected concomitant reduction in the amount of visual skyglow over Tucson. SkyGlow Simulator models predict skyglow decreases on the order of 10-20% depending on whether fully shielded or partly shielded lights are in use. We tested this prediction using visual night sky brightness estimates and luminance-calibrated, panchromatic all-sky imagery at 15 locations in and near the city. Data were obtained in 2014, before the LED conversion began, and in mid-2017 after approximately 95% of ∼ 18,000 luminaires was converted. Skyglow differed marginally, and in all cases with valid data changed by < ± 20%. Over the same period, the city's upward-directed optical radiance detected from Earth orbit decreased by approximately 7%. While these results are not conclusive, they suggest that LED conversions paired with dimming can reduce skyglow over cities.

Tuning the light in senior care: Evaluating a trial LED lighting system at the ACC Care Center in Sacramento, CA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davis, Robert G.; Wilkerson, Andrea M.

This report summarizes the results from a trial installation of light-emitting diode (LED) lighting systems in several spaces within the ACC Care Center in Sacramento, CA. The Sacramento Municipal Utility District (SMUD) coordinated the project and invited the U.S. Department of Energy (DOE) to document the performance of the LED lighting systems as part of a GATEWAY evaluation. DOE tasked the Pacific Northwest National Laboratory (PNNL) to conduct the investigation. SMUD and ACC staff coordinated and completed the design and installation of the LED systems, while PNNL and SMUD staff evaluated the photometric performance of the systems. ACC staff alsomore » track behavioral and health measures of the residents; some of those results are reported here, although PNNL staff were not directly involved in collecting or interpreting those data. The trial installation took place in a double resident room and a single resident room, and the corridor that connects those (and other) rooms to the central nurse station. Other spaces in the trial included the nurse station, a common room called the family room located near the nurse station, and the ACC administrator’s private office.« less

Evaluation of an LED Retrofit Project at Princeton University's Carl Icahn Laboratory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davis, Robert; Murphy, Arthur; Perrin, Tess

At Princeton University’s Carl Icahn Laboratory, DOE’s Commercial Buildings Integration Program documented the implementation of LED retrofit products for recessed troffers, linear cove lighting, and downlights – as part of Princeton’s first building-wide interior LED project. The conversion to LED enables more extensive use of lighting controls to tailor the lighting to the task and limit the operating hours based on occupancy, and the estimated energy savings including controls is 62% compared to the incumbent system.

Analysis of energy efficient highway lighting retrofits.

DOT National Transportation Integrated Search

2015-06-01

Solid state lighting technology is advancing rapidly to a point where light emitting diode (LED) lighting : systems can be viable replacements for existing lighting systems using high pressure sodium (HPS). The : present report summarizes analyses co...

The possible ocular hazards of LED dental illumination applications.

PubMed

Stamatacos, Catherine; Harrison, Janet L

2014-04-01

The use of high-intensity illumination via Light-Emitting Diode (LED) headlamps is gaining in popularity with dentists and student dentists. Practitioners are using LED headlamps together with magnifying loupes, overhead LED illumination and fiber-optic dental handpieces for long periods of time. Although most manufacturers of these LED illuminators advertise that their devices emit "white" light, these still consist of two spectral bands - the blue spectral band, with its peak at 445 nm, and the green with its peak at 555 nm. While manufacturers suggest that their devices emit "white" light, spectral components of LED lights from different companies are significantly different. Dental headlamp manufacturers strive to create a white LED, and they advertise that this type of light emitted from their product offers bright white-light illumination. However, the manufacturing of a white LED light is done through selection of a white LED-type based on the peak blue strength in combination with the green peak strength and thus creating a beam-forming optic, which determines the beam quality. Some LED illuminators have a strong blue-light component versus the green-light component. Blue-light is highly energized and is close in the color spectrum to ultraviolet-light. The hazards of retinal damage with the use of high-intensity blue-lights has been well-documented. There is limited research regarding the possible ocular hazards of usage of high-intensity illuminating LED devices. Furthermore, the authors have found little research, standards, or guidelines examining the possible safety issues regarding the unique dental practice setting consisting of the combined use of LED illumination systems. Another unexamined component is the effect of high-intensity light reflective glare and magnification back to the practitioner's eyes due to the use of water during dental procedures. Based on the result of Dr. Janet Harrison's observations of beginning dental students in a laboratory setting, the aim of this review is to raise awareness of the potential risk for eye damage when singular or combinations of LED illumination are used.

The possible ocular hazards of LED dental illumination applications.

PubMed

Stamatacos, Catherine; Harrison, Janet L

2013-01-01

The use of high-intensity illumination via Light-Emitting Diode (LED) headlamps is gaining in popularity with dentists and student dentists. Practitioners are using LED headlamps together with magnifying loupes, overhead LED illumination and fiber-optic dental handpieces for long periods of time. Although most manufacturers of these LED illuminators advertise that their devices emit "white" light, these still consist of two spectral bands--the blue spectral band, with its peak at 445 nm, and the green with its peak at 555 nm. While manufacturers suggest that their devices emit "white" light, spectral components of LED lights from different companies are significantly different. Dental headlamp manufacturers strive to create a white LED, and they advertise that this type of light emitted from their product offers bright white-light illumination. However, the manufacturing of a white LED light is done through selection of a white LED-type based on the peak blue strength in combination with the green peak strength and thus creating a beam-forming optic, which determines the beam quality. Some LED illuminators have a strong blue-light component versus the green-light component. Blue-light is highly energized and is close in the color spectrum to ultraviolet-light. The hazards of retinal damage with the use of high-intensity blue-lights has been well-documented. There is limited research regarding the possible ocular hazards of usage of high-intensity illuminating LED devices. Furthermore, the authors have found little research, standards, or guidelines examining the possible safety issues regarding the unique dental practice setting consisting of the combined use of LED illumination systems. Another unexamined component is the effect of high-intensity light reflective glare and magnification back to the practitioner's eyes due to the use of water during dental procedures. Based on the result of Dr. Janet Harrison's observations of beginning dental students in a laboratory setting, the aim of this review is to raise awareness of the potential risk for eye damage when singular or combinations of LED illumination are used.

Design, fabrication, and packaging of an integrated, wirelessly-powered optrode array for optogenetics application

PubMed Central

Kwon, Ki Yong; Lee, Hyung-Min; Ghovanloo, Maysam; Weber, Arthur; Li, Wen

2015-01-01

The recent development of optogenetics has created an increased demand for advancing engineering tools for optical modulation of neural circuitry. This paper details the design, fabrication, integration, and packaging procedures of a wirelessly-powered, light emitting diode (LED) coupled optrode neural interface for optogenetic studies. The LED-coupled optrode array employs microscale LED (μLED) chips and polymer-based microwaveguides to deliver light into multi-level cortical networks, coupled with microelectrodes to record spontaneous changes in neural activity. An integrated, implantable, switched-capacitor based stimulator (SCS) system provides high instantaneous power to the μLEDs through an inductive link to emit sufficient light and evoke neural activities. The presented system is mechanically flexible, biocompatible, miniaturized, and lightweight, suitable for chronic implantation in small freely behaving animals. The design of this system is scalable and its manufacturing is cost effective through batch fabrication using microelectromechanical systems (MEMS) technology. It can be adopted by other groups and customized for specific needs of individual experiments. PMID:25999823

Temperature analysis during bonding of brackets using LED or halogen light base units.

PubMed

Silva, Paulo César Gomes; De Fátima Zanirato Lizarelli, Rosane; Moriyama, Lílian Tan; De Toledo Porto Neto, Sizenando; Bagnato, Vanderlei Salvador

2005-02-01

The purpose of our investigation is to compare the intrapulpal temperature changes following blue LED system and halogen lamp irradiation at the enamel surface of permanent teeth. The fixation of brackets using composite resin is more comfortable and faster when using a photo-curable composite. Several light sources can be used: halogens, arc plasma, lasers, and recently blue LED systems. An important aspect to be observed during such a procedures is the temperature change. In this study, we have used nine human extracted permanent teeth: three central incisors, three lateral incisors, and three canines. Teeth were exposed to two light sources: blue LED system (preliminary commercial model LEC 470-II) and halogen lamp (conventional photo-cure equipment). The surface of teeth was exposed for 20, 40, and 60 sec at the buccal and lingual enamel surface with an angle of 45 degrees. Temperature values measured by a thermistor placed at pulpar chamber were read in time intervals of 1 sec. We obtained plots showing the temperature evolution as a function of time for each experiment. There is a correlation between heating quantity and exposition time of light source: with increasing exposition time, heating increases into the pulpal chamber. The halogen lamp showed higher heating than the LED system, which showed a shorter time of cooling than halogen lamp. The blue LED system seems like the indicated light source for photo-cure of composite resin during the bonding of brackets. The fixation of brackets using composite resin is more comfortable and faster when using a photo-curable composite. Blue LED equipment did not heat during its use. This could permit a shorter clinical time of operation and better performance.

LEDs on the threshold for use in projection systems: challenges, limitations and applications

NASA Astrophysics Data System (ADS)

Moffat, Bryce Anton

2006-02-01

The use of coloured LEDs as light sources in digital projectors depends on an optimal combination of optical, electrical and thermal parameters to meet the performance and cost targets needed to enable these products to compete in the marketplace. This paper describes the system design methodology for a digital micromirror display (DMD) based optical engine using LEDs as the light source, starting at the basic physical and geometrical parameters of the DMD and other optical elements through characterization of the LEDs to optimizing the system performance by determining optimal driving conditions. The main challenge in using LEDs is the luminous flux density, which is just at the threshold of acceptance in projection systems and thus only a fully optimized optical system with a uniformly bright set of LEDs can be used. As a result of this work we have developed two applications: a compact pocket projector and a rear projection television.

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

NASA Astrophysics Data System (ADS)

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

2015-07-01

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

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kinzey, B. R.; Rosinbum, T.

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

A design of LED adaptive dimming lighting system based on incremental PID controller

NASA Astrophysics Data System (ADS)

He, Xiangyan; Xiao, Zexin; He, Shaojia

2010-11-01

As a new generation energy-saving lighting source, LED is applied widely in various technology and industry fields. The requirement of its adaptive lighting technology is more and more rigorous, especially in the automatic on-line detecting system. In this paper, a closed loop feedback LED adaptive dimming lighting system based on incremental PID controller is designed, which consists of MEGA16 chip as a Micro-controller Unit (MCU), the ambient light sensor BH1750 chip with Inter-Integrated Circuit (I2C), and constant-current driving circuit. A given value of light intensity required for the on-line detecting environment need to be saved to the register of MCU. The optical intensity, detected by BH1750 chip in real time, is converted to digital signal by AD converter of the BH1750 chip, and then transmitted to MEGA16 chip through I2C serial bus. Since the variation law of light intensity in the on-line detecting environment is usually not easy to be established, incremental Proportional-Integral-Differential (PID) algorithm is applied in this system. Control variable obtained by the incremental PID determines duty cycle of Pulse-Width Modulation (PWM). Consequently, LED's forward current is adjusted by PWM, and the luminous intensity of the detection environment is stabilized by self-adaptation. The coefficients of incremental PID are obtained respectively after experiments. Compared with the traditional LED dimming system, it has advantages of anti-interference, simple construction, fast response, and high stability by the use of incremental PID algorithm and BH1750 chip with I2C serial bus. Therefore, it is suitable for the adaptive on-line detecting applications.

The cinema LED lighting system design based on SCM

NASA Astrophysics Data System (ADS)

En, De; Wang, Xiaobin

2010-11-01

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

Energy efficient lighting and communications

NASA Astrophysics Data System (ADS)

Zhou, Z.; Kavehrad, M.; Deng, P.

2012-01-01

As Light-Emitting Diode (LED)'s increasingly displace incandescent lighting over the next few years, general applications of Visible Light Communication (VLC) technology are expected to include wireless internet access, vehicle-to-vehicle communications, broadcast from LED signage, and machine-to-machine communications. An objective in this paper is to reveal the influence of system parameters on the power distribution and communication quality, in a general plural sources VLC system. It is demonstrated that sources' Half-Power Angles (HPA), receivers' Field-Of Views (FOV), sources layout and the power distribution among sources are significant impact factors. Based on our findings, we developed a method to adaptively change working status of each LED respectively according to users' locations. The program minimizes total power emitted while simultaneously ensuring sufficient light intensity and communication quality for each user. The paper also compares Orthogonal Frequency-Division Multiplexing (OFDM) and On-Off Keying (OOK) signals performance in indoor optical wireless communications. The simulation is carried out for different locations where different impulse response distortions are experienced. OFDM seems a better choice than prevalent OOK for indoor VLC due to its high resistance to multi-path effect and delay spread. However, the peak-to-average power limitations of the method must be investigated for lighting LEDs.

Status of Solid State Lighting Product Development and Future Trends for General Illumination.

PubMed

Katona, Thomas M; Pattison, P Morgan; Paolini, Steve

2016-06-07

After decades of research and development on fabrication of efficient light-emitting diodes (LEDs) throughout the visible spectrum, LED-based lighting has reached unparalleled performance with respect to energy efficiency and has become the light source for virtually all new lighting products being designed today. The development of the core light sources and their subsequent integration into lighting systems continue to present unique challenges and opportunities for product designers. We review these systems and the current development status, as well as provide context for the trends in solid state lighting that are leading to the development of value-added lighting solutions that extend the domain of lighting beyond light generation, into fields as diverse as communications, healthcare, and agricultural production.

Evaluation of light-emitting diodes for signage applications

NASA Astrophysics Data System (ADS)

Freyssinier, Jean Paul; Zhou, Yutao; Ramamurthy, Vasudha; Bierman, Andrew; Bullough, John D.; Narendran, Nadarajah

2004-01-01

This paper outlines two parts of a study designed to evaluate the use of light-emitting diodes (LEDs) in channel-letter signs. The first part of the study evaluated the system performance of red LED signs and white LED signs against reference neon and cold-cathode signs. The results show a large difference between the actual performance and potential savings from red and white LEDs. Depending on the configuration, a red LED sign could use 20% to 60% less power than a neon sign at the same light output. The light output of the brightest white LED sign tested was 15% lower than the cold-cathode reference, but its power was 53% higher. It appears from this study that the most efficient white LED system is still 40% less efficient than the cold-cathode system tested. One area that offers a great potential for further energy savings is the acrylic diffuser of the signs. The acrylic diffusers measured absorb between 60% and 66% of the light output produced by the sign. Qualitative factors are also known to play an important role in signage systems. One of the largest issues with any new lighting technology is its acceptance by the end user. Consistency of light output and color among LEDs, even from the same manufacturing batch, and over time, are two of the major issues that also could affect the advantages of LEDs for signage applications. To evaluate different signage products and to identify the suitability of LEDs for this application, it is important to establish a criterion for brightness uniformity. Building upon this information, the second part of the study used human factors evaluations to determine a brightness-uniformity criterion for channel-letter signs. The results show that the contrast modulation between bright and dark areas within a sign seems to elicit the strongest effect on how people perceive uniformity. A strong monotonic relationship between modulation and acceptability was found in this evaluation. The effect of contrast seems to be stronger than that of spatial frequency or background luminance, particularly for contrast modulation values of less than 0.20 or greater than 0.60. A sign with luminance variations of less than 20% would be accepted by at least 80% of the population in any given context.

Design considerations for highly effective fluorescence excitation and detection optical systems for molecular diagnostics

NASA Astrophysics Data System (ADS)

Kasper, Axel; Van Hille, Herbert; Kuk, Sola

2018-02-01

Modern instruments for molecular diagnostics are continuously optimized for diagnostic accuracy, versatility and throughput. The latest progress in LED technology together with tailored optics solutions allows developing highly efficient photonics engines perfectly adapted to the sample under test. Super-bright chip-on-board LED light sources are a key component for such instruments providing maximum luminous intensities in a multitude of narrow spectral bands. In particular the combination of white LEDs with other narrow band LEDs allows achieving optimum efficiency outperforming traditional Xenon light sources in terms of energy consumption, heat dissipation in the system, and switching time between spectral channels. Maximum sensitivity of the diagnostic system can only be achieved with an optimized optics system for the illumination and imaging of the sample. The illumination beam path must be designed for optimum homogeneity across the field while precisely limiting the angular distribution of the excitation light. This is a necessity for avoiding spill-over to the detection beam path and guaranteeing the efficiency of the spectral filtering. The imaging optics must combine high spatial resolution, high light collection efficiency and optimized suppression of excitation light for good signal-to-noise ratio. In order to achieve minimum cross-talk between individual wells in the sample, the optics design must also consider the generation of stray light and the formation of ghost images. We discuss what parameters and limitations have to be considered in an integrated system design approach covering the full path from the light source to the detector.

Disinfection of Spacecraft Potable Water Systems by Photocatalytic Oxidation Using UV-A Light Emitting Diodes

NASA Technical Reports Server (NTRS)

Birmele, Michele N.; O'Neal, Jeremy A.; Roberts, Michael S.

2011-01-01

Ultraviolet (UV) light has long been used in terrestrial water treatment systems for photodisinfection and the removal of organic compounds by several processes including photoadsorption, photolysis, and photocatalytic oxidation/reduction. Despite its effectiveness for water treatment, UV has not been explored for spacecraft applications because of concerns about the safety and reliability of mercury-containing UV lamps. However, recent advances in ultraviolet light emitting diodes (UV LEDs) have enabled the utilization of nanomaterials that possess the appropriate optical properties for the manufacture of LEDs capable of producing monochromatic light at germicidal wavelengths. This report describes the testing of a commercial-off-the-shelf, high power Nichia UV-A LED (250mW A365nnJ for the excitation of titanium dioxide as a point-of-use (POD) disinfection device in a potable water system. The combination of an immobilized, high surface area photocatalyst with a UV-A LED is promising for potable water system disinfection since toxic chemicals and resupply requirements are reduced. No additional consumables like chemical biocides, absorption columns, or filters are required to disinfect and/or remove potentially toxic disinfectants from the potable water prior to use. Experiments were conducted in a static test stand consisting of a polypropylene microtiter plate containing 3mm glass balls coated with titanium dioxide. Wells filled with water were exposed to ultraviolet light from an actively-cooled UV-A LED positioned above each well and inoculated with six individual challenge microorganisms recovered from the International Space Station (ISS): Burkholderia cepacia, Cupriavidus metallidurans, Methylobacterium fujisawaense, Pseudomonas aeruginosa, Sphingomonas paucimobilis and Wautersia basilensis. Exposure to the Nichia UV-A LED with photocatalytic oxidation resulted in a complete (>7-log) reduction of each challenge bacteria population in <180 minutes of contact time. With continued advances in the design and manufacture of UV-A LEDs and semi-conducting photocatalysts, LED activated photochemical process technology promises to extend its application to spacecraft environmental systems.

Multi-LED parallel transmission for long distance underwater VLC system with one SPAD receiver

NASA Astrophysics Data System (ADS)

Wang, Chao; Yu, Hong-Yi; Zhu, Yi-Jun; Wang, Tao; Ji, Ya-Wei

2018-03-01

In this paper, a multiple light emitting diode (LED) chips parallel transmission (Multi-LED-PT) scheme for underwater visible light communication system with one photon-counting single photon avalanche diode (SPAD) receiver is proposed. As the lamp always consists of multi-LED chips, the data rate could be improved when we drive these multi-LED chips parallel by using the interleaver-division-multiplexing technique. For each chip, the on-off-keying modulation is used to reduce the influence of clipping. Then a serial successive interference cancellation detection algorithm based on ideal Poisson photon-counting channel by the SPAD is proposed. Finally, compared to the SPAD-based direct current-biased optical orthogonal frequency division multiplexing system, the proposed Multi-LED-PT system could improve the error-rate performance and anti-nonlinearity performance significantly under the effects of absorption, scattering and weak turbulence-induced channel fading together.

Light use efficiency for vegetables production in protected and indoor environments

NASA Astrophysics Data System (ADS)

Cocetta, Giacomo; Casciani, Daria; Bulgari, Roberta; Musante, Fulvio; Kołton, Anna; Rossi, Maurizio; Ferrante, Antonio

2017-01-01

In recent years, there is a growing interest for vegetables production in indoor or disadvantaged climatic zones by using greenhouses. The main problem of crop growing indoor or in environment with limited light availability is the correct choice of light source and the quality of lighting spectrum. In greenhouse and indoor cultivations, plant density is higher than in the open field and plants have to compete for light and nutrients. Nowadays, advanced systems for indoor horticulture use light emitting diodes (LED) for improving crop growth, enhancing the plant productivity and favouring the best nutritional quality formation. In closed environments, as indoor growing modules, the lighting system represents the only source of light and its features are fundamental for obtaining the best lighting performances for plant and the most efficient solution. LED lighting engines are more efficient compared to the lighting sources used traditionally in horticulture and allow light spectrum and intensity modulations to enhance the light use efficiency for plants. The lighting distribution and the digital controls are fundamental for tailoring the spectral distribution on each plant in specific moments of its growth and play an important role for optimizing growth and produce high-quality vegetables. LED lights can increase plant growth and yield, but also nutraceutical quality, since some light intensities increase pigments biosynthesis and enhance the antioxidants content of leaves or fruits: in this regards the selection of LED primary light sources in relation to the peaks of the absorbance curve of the plants is important.

Light-emitting diodes (LED) for domestic lighting: any risks for the eye?

PubMed

Behar-Cohen, F; Martinsons, C; Viénot, F; Zissis, G; Barlier-Salsi, A; Cesarini, J P; Enouf, O; Garcia, M; Picaud, S; Attia, D

2011-07-01

Light-emitting diodes (LEDs) are taking an increasing place in the market of domestic lighting because they produce light with low energy consumption. In the EU, by 2016, no traditional incandescent light sources will be available and LEDs may become the major domestic light sources. Due to specific spectral and energetic characteristics of white LEDs as compared to other domestic light sources, some concerns have been raised regarding their safety for human health and particularly potential harmful risks for the eye. To conduct a health risk assessment on systems using LEDs, the French Agency for Food, Environmental and Occupational Health & Safety (ANSES), a public body reporting to the French Ministers for ecology, for health and for employment, has organized a task group. This group consisted physicists, lighting and metrology specialists, retinal biologist and ophthalmologist who have worked together for a year. Part of this work has comprised the evaluation of group risks of different white LEDs commercialized on the French market, according to the standards and found that some of these lights belonged to the group risk 1 or 2. This paper gives a comprehensive analysis of the potential risks of white LEDs, taking into account pre-clinical knowledge as well as epidemiologic studies and reports the French Agency's recommendations to avoid potential retinal hazards. Copyright © 2011. Published by Elsevier Ltd.

High-power LED package requirements

NASA Astrophysics Data System (ADS)

Wall, Frank; Martin, Paul S.; Harbers, Gerard

2004-01-01

Power LEDs have evolved from simple indicators into illumination devices. For general lighting applications, where the objective is to light up an area, white LED arrays have been utilized to serve that function. Cost constraints will soon drive the industry to provide a discrete lighting solution. Early on, that will mean increasing the power densities while quantum efficiencies are addressed. For applications such as automotive headlamps & projection, where light needs to be tightly collimated, or controlled, arrays of die or LEDs will not be able to satisfy the requirements & limitations defined by etendue. Ultimately, whether a luminaire requires a small source with high luminance, or light spread over a general area, economics will force the evolution of the illumination LED into a compact discrete high power package. How the customer interfaces with this new package should be an important element considered early on in the design cycle. If an LED footprint of adequate size is not provided, it may prove impossible for the customer, or end user, to get rid of the heat in a manner sufficient to prevent premature LED light output degradation. Therefore it is critical, for maintaining expected LED lifetime & light output, that thermal performance parameters be defined, by design, at the system level, which includes heat sinking methods & interface materials or methdology.

Hierarchical scheme for detecting the rotating MIMO transmission of the in-door RGB-LED visible light wireless communications using mobile-phone camera

NASA Astrophysics Data System (ADS)

Chen, Shih-Hao; Chow, Chi-Wai

2015-01-01

Multiple-input and multiple-output (MIMO) scheme can extend the transmission capacity for the light-emitting-diode (LED) based visible light communication (VLC) systems. The MIMO VLC system that uses the mobile-phone camera as the optical receiver (Rx) to receive MIMO signal from the n×n Red-Green-Blue (RGB) LED array is desirable. The key step of decoding this signal is to detect the signal direction. If the LED transmitter (Tx) is rotated, the Rx may not realize the rotation and transmission error can occur. In this work, we propose and demonstrate a novel hierarchical transmission scheme which can reduce the computation complexity of rotation detection in LED array VLC system. We use the n×n RGB LED array as the MIMO Tx. In our study, a novel two dimensional Hadamard coding scheme is proposed. Using the different LED color layers to indicate the rotation, a low complexity rotation detection method can be used for improving the quality of received signal. The detection correction rate is above 95% in the indoor usage distance. Experimental results confirm the feasibility of the proposed scheme.

LEDs Illuminate Bulbs for Better Sleep, Wake Cycles

NASA Technical Reports Server (NTRS)

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.

Matrix light and pixel light: optical system architecture and requirements to the light source

NASA Astrophysics Data System (ADS)

Spinger, Benno; Timinger, Andreas L.

2015-09-01

Modern Automotive headlamps enable improved functionality for more driving comfort and safety. Matrix or Pixel light headlamps are not restricted to either pure low beam functionality or pure high beam. Light in direction of oncoming traffic is selectively switched of, potential hazard can be marked via an isolated beam and the illumination on the road can even follow a bend. The optical architectures that enable these advanced functionalities are diverse. Electromechanical shutters and lens units moved by electric motors were the first ways to realize these systems. Switching multiple LED light sources is a more elegant and mechanically robust solution. While many basic functionalities can already be realized with a limited number of LEDs, an increasing number of pixels will lead to more driving comfort and better visibility. The required optical system needs not only to generate a desired beam distribution with a high angular dynamic, but also needs to guarantee minimal stray light and cross talk between the different pixels. The direct projection of the LED array via a lens is a simple but not very efficient optical system. We discuss different optical elements for pre-collimating the light with minimal cross talk and improved contrast between neighboring pixels. Depending on the selected optical system, we derive the basic light source requirements: luminance, surface area, contrast, flux and color homogeneity.

GATEWAY Demonstrations: Tuning Hospital Lighting: Evaluating Tunable LED Lighting at the Swedish Hospital Behavioral Health Unit in Seattle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilkerson, Andrea; Davis, Robert G.; Clark, Edward

The GATEWAY program evaluated a tunable LED lighting system installed in the new Swedish Medical Behavioral Health Unit in Seattle that incorporates color-tunable luminaires in common areas, and uses advanced controls for dimming and color tuning, with the goal of providing a better environment for staff and patients. The report reviews the design of the tunable lighting system, summarizes two sets of measurements, and discusses the circadian, energy, and commissioning implications as well as lessons learned from the project.

Enhanced Automated Guidance System for Horizontal Auger Boring Based on Image Processing.

PubMed

Wu, Lingling; Wen, Guojun; Wang, Yudan; Huang, Lei; Zhou, Jiang

2018-02-15

Horizontal auger boring (HAB) is a widely used trenchless technology for the high-accuracy installation of gravity or pressure pipelines on line and grade. Differing from other pipeline installations, HAB requires a more precise and automated guidance system for use in a practical project. This paper proposes an economic and enhanced automated optical guidance system, based on optimization research of light-emitting diode (LED) light target and five automated image processing bore-path deviation algorithms. An LED light target was optimized for many qualities, including light color, filter plate color, luminous intensity, and LED layout. The image preprocessing algorithm, direction location algorithm, angle measurement algorithm, deflection detection algorithm, and auto-focus algorithm, compiled in MATLAB, are used to automate image processing for deflection computing and judging. After multiple indoor experiments, this guidance system is applied in a project of hot water pipeline installation, with accuracy controlled within 2 mm in 48-m distance, providing accurate line and grade controls and verifying the feasibility and reliability of the guidance system.

Design and analysis of reflector for uniform light-emitting diode illuminance.

PubMed

Tsai, Chung-Yu

2013-05-01

A light-emitting diode (LED) projection system is proposed, composed of an LED chip and a variable-focus-parabolic (VFP) reflector, in which the focal length varies as a function of the vertical displacement of the incidence point relative to the horizontal centerline of the LED chip. The light-ray paths within the projection system are analyzed using an exact analytical model and a skew-ray tracing approach. The profile of the proposed VFP reflector and the position of the LED chip are then optimized in such a way as to enhance the uniformity of the illuminance distribution on the target region of the image plane. The validity of the optimized design is demonstrated by means of ZEMAX simulations. It is shown that the optimized VFP projector system yields a significant improvement in illuminance uniformity compared to conventional spherical and parabolic projectors and therefore minimizes the glare effect.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kinzey, Bruce

The City of Detroit is in the midst of a comprehensive restoration of its street lighting system that includes transitioning the existing HPS sources to LED. This report provides an objective review of the circumstances surrounding the system restoration, the processes undertaken and decisions made, and the results so far — and contains useful information about issues that arise during large-scale LED street lighting projects.

An inexpensive Arduino-based LED stimulator system for vision research.

PubMed

Teikari, Petteri; Najjar, Raymond P; Malkki, Hemi; Knoblauch, Kenneth; Dumortier, Dominique; Gronfier, Claude; Cooper, Howard M

2012-11-15

Light emitting diodes (LEDs) are being used increasingly as light sources in life sciences applications such as in vision research, fluorescence microscopy and in brain-computer interfacing. Here we present an inexpensive but effective visual stimulator based on light emitting diodes (LEDs) and open-source Arduino microcontroller prototyping platform. The main design goal of our system was to use off-the-shelf and open-source components as much as possible, and to reduce design complexity allowing use of the system to end-users without advanced electronics skills. The main core of the system is a USB-connected Arduino microcontroller platform designed initially with a specific emphasis on the ease-of-use creating interactive physical computing environments. The pulse-width modulation (PWM) signal of Arduino was used to drive LEDs allowing linear light intensity control. The visual stimulator was demonstrated in applications such as murine pupillometry, rodent models for cognitive research, and heterochromatic flicker photometry in human psychophysics. These examples illustrate some of the possible applications that can be easily implemented and that are advantageous for students, educational purposes and universities with limited resources. The LED stimulator system was developed as an open-source project. Software interface was developed using Python with simplified examples provided for Matlab and LabVIEW. Source code and hardware information are distributed under the GNU General Public Licence (GPL, version 3). Copyright © 2012 Elsevier B.V. All rights reserved.

Development of OSL system using two high-density blue LEDs equipped with liquid light guides

NASA Astrophysics Data System (ADS)

Choi, J. H.; Kim, M. J.; Cheong, C. S.; Hong, D. G.

2014-03-01

In recent years, considerable developments in optically stimulated luminescence (OSL) have been made in the fields of radiation dosimetry, age determination, and medical applications. A compact and economical OSL system comprising a precision x-y-z stage for loading 12 samples, a small X-ray generator for radiation dosing, and two powerful blue light emitting diodes (LEDs) for optical stimulation equipped with VIS liquid light guides (VIS-LLGs) has been developed. This paper describes the principal features of the system along with the examples of measurements performed by the system.

Application of 3D printing to prototype and develop novel plant tissue culture systems.

PubMed

Shukla, Mukund R; Singh, Amritpal S; Piunno, Kevin; Saxena, Praveen K; Jones, A Maxwell P

2017-01-01

Due to the complex process of designing and manufacturing new plant tissue culture vessels through conventional means there have been limited efforts to innovate improved designs. Further, development and availability of low cost, energy efficient LEDs of various spectra has made it a promising light source for plant growth in controlled environments. However, direct replacement of conventional lighting sources with LEDs does not address problems with uniformity, spectral control, or the challenges in conducting statistically valid experiments to assess the effects of light. Prototyping using 3D printing and LED based light sources could help overcome these limitations and lead to improved culture systems. A modular culture vessel design in which the fluence rate and spectrum of light are independently controlled was designed, prototyped using 3D printing, and evaluated for plant growth. This design is compatible with semi-solid and liquid based culture systems. Observations on morphology, chlorophyll content, and chlorophyll fluorescence based stress parameters from in vitro plants cultured under different light spectra with similar overall fluence rate indicated different responses in Nicotiana tabacum and Artemisia annua plantlets. This experiment validates the utility of 3D printing to design and test functional vessels and demonstrated that optimal light spectra for in vitro plant growth is species-specific. 3D printing was successfully used to prototype novel culture vessels with independently controlled variable fluence rate/spectra LED lighting. This system addresses several limitations associated with current lighting systems, providing more uniform lighting and allowing proper replication/randomization for experimental plant biology while increasing energy efficiency. A complete procedure including the design and prototyping of a culture vessel using 3D printing, commercial scale injection molding of the prototype, and conducting a properly replicated experiment are discussed. This open source design has the scope for further improvement and adaptation and demonstrates the power of 3D printing to improve the design of culture systems.

340nm UV LED excitation in time-resolved fluorescence system for europium-based immunoassays detection

NASA Astrophysics Data System (ADS)

Rodenko, Olga; Fodgaard, Henrik; Tidemand-Lichtenberg, Peter; Pedersen, Christian

2017-02-01

In immunoassay analyzers for in-vitro diagnostics, Xenon flash lamps have been widely used as excitation light sources. Recent advancements in UV LED technology and its advantages over the flash lamps such as smaller footprint, better wall-plug efficiency, narrow emission spectrum, and no significant afterglow, have made them attractive light sources for gated detection systems. In this paper, we report on the implementation of a 340 nm UV LED based time-resolved fluorescence system based on europium chelate as a fluorescent marker. The system performance was tested with the immunoassay based on the cardiac marker, TnI. The same signal-to-noise ratio as for the flash lamp based system was obtained, operating the LED below specified maximum current. The background counts of the system and its main contributors were measured and analyzed. The background of the system of the LED based unit was improved by 39% compared to that of the Xenon flash lamp based unit, due to the LEDs narrower emission spectrum and longer pulse width. Key parameters of the LED system are discussed to further optimize the signal-to-noise ratio and signal-to-background, and hence the sensitivity of the instrument.

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

NASA Astrophysics Data System (ADS)

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.

LED traffic signal management system : tech summary.

DOT National Transportation Integrated Search

2016-06-01

The light source of a signal module is comprised of an array of multiple individual light emitting diodes (LEDs). : Fading of the array over its operational life is a serious concern of traffic engineers throughout the nation. The : Institute of Tran...

Nighttime Supplemental LED Inter-lighting Improves Growth and Yield of Single-Truss Tomatoes by Enhancing Photosynthesis in Both Winter and Summer.

PubMed

Tewolde, Fasil T; Lu, Na; Shiina, Kouta; Maruo, Toru; Takagaki, Michiko; Kozai, Toyoki; Yamori, Wataru

2016-01-01

Greenhouses with sophisticated environmental control systems, or so-called plant factories with solar light, enable growers to achieve high yields of produce with desirable qualities. In a greenhouse crop with high planting density, low photosynthetic photon flux density (PPFD) at the lower leaves tends to limit plant growth, especially in the winter when the solar altitude and PPFD at the canopy are low and day length is shorter than in summer. Therefore, providing supplemental lighting to the lower canopy can increase year-round productivity. However, supplemental lighting can be expensive. In some places, the cost of electricity is lower at night, but the effect of using supplemental light at night has not yet been examined. In this study, we examined the effects of supplemental LED inter-lighting (LED inter-lighting hereafter) during the daytime or nighttime on photosynthesis, growth, and yield of single-truss tomato plants both in winter and summer. We used LED inter-lighting modules with combined red and blue light to illuminate lower leaves right after the first anthesis. The PPFD of this light was 165 μmol m(-2) s(-1) measured at 10 cm from the LED module. LED inter-lighting was provided from 4:00 am to 4:00 pm for the daytime treatments and from 10:00 pm to 10:00 am for the nighttime treatments. Plants exposed only to solar light were used as controls. Daytime LED inter-lighting increased the photosynthetic capacity of middle and lower canopy leaves, which significantly increased yield by 27% in winter; however, photosynthetic capacity and yield were not significantly increased during summer. Nighttime LED inter-lighting increased photosynthetic capacity in both winter and summer, and yield increased by 24% in winter and 12% in summer. In addition, nighttime LED inter-lighting in winter significantly increased the total soluble solids and ascorbic acid content of the tomato fruits, by 20 and 25%, respectively. Use of nighttime LED inter-lighting was also more cost-effective than daytime inter-lighting. Thus, nighttime LED inter-lighting can effectively improve tomato plant growth and yield with lower energy cost compared with daytime both in summer and winter.

Nighttime Supplemental LED Inter-lighting Improves Growth and Yield of Single-Truss Tomatoes by Enhancing Photosynthesis in Both Winter and Summer

PubMed Central

Tewolde, Fasil T.; Lu, Na; Shiina, Kouta; Maruo, Toru; Takagaki, Michiko; Kozai, Toyoki; Yamori, Wataru

2016-01-01

Greenhouses with sophisticated environmental control systems, or so-called plant factories with solar light, enable growers to achieve high yields of produce with desirable qualities. In a greenhouse crop with high planting density, low photosynthetic photon flux density (PPFD) at the lower leaves tends to limit plant growth, especially in the winter when the solar altitude and PPFD at the canopy are low and day length is shorter than in summer. Therefore, providing supplemental lighting to the lower canopy can increase year-round productivity. However, supplemental lighting can be expensive. In some places, the cost of electricity is lower at night, but the effect of using supplemental light at night has not yet been examined. In this study, we examined the effects of supplemental LED inter-lighting (LED inter-lighting hereafter) during the daytime or nighttime on photosynthesis, growth, and yield of single-truss tomato plants both in winter and summer. We used LED inter-lighting modules with combined red and blue light to illuminate lower leaves right after the first anthesis. The PPFD of this light was 165 μmol m-2 s-1 measured at 10 cm from the LED module. LED inter-lighting was provided from 4:00 am to 4:00 pm for the daytime treatments and from 10:00 pm to 10:00 am for the nighttime treatments. Plants exposed only to solar light were used as controls. Daytime LED inter-lighting increased the photosynthetic capacity of middle and lower canopy leaves, which significantly increased yield by 27% in winter; however, photosynthetic capacity and yield were not significantly increased during summer. Nighttime LED inter-lighting increased photosynthetic capacity in both winter and summer, and yield increased by 24% in winter and 12% in summer. In addition, nighttime LED inter-lighting in winter significantly increased the total soluble solids and ascorbic acid content of the tomato fruits, by 20 and 25%, respectively. Use of nighttime LED inter-lighting was also more cost-effective than daytime inter-lighting. Thus, nighttime LED inter-lighting can effectively improve tomato plant growth and yield with lower energy cost compared with daytime both in summer and winter. PMID:27092163

NDIR gas sensing using high performance AlInSb mid-infrared LEDs as light source

NASA Astrophysics Data System (ADS)

Camargo, E. G.; Goda, Y.; Morohara, O.; Fujita, H.; Geka, H.; Ueno, K.; Shibata, Y.; Kuze, N.

2017-08-01

In this paper, we report the performance of room temperature operated mid-infrared light emitting diode (LED) with an InSb buffer layer and AlInSb active/barrier layers, which showed to be suitable for non-dispersive infrared (NDIR) gas sensing. Characterization of the LED was performed and we found that good carrier confinement and crystalline quality was responsible for its high performance. High efficiency light extraction was obtained by adopting backside emission architecture together with surface roughening treatment and TiO2 anti-reflection coating. The fabricated AlInSb LED showed 75% higher power conversion efficiency when compared with a commercially available device. The developed LED, together with a commercially available infrared (IR) detector equipped with band-pass optical filter (AK9710, manufactured by Asahi Kasei Microdevices) were coupled into a mirror system forming a light path length of 80 mm, which was tested for CO2 gas sensing. For a non-absorbing environment, sensor output of 8 nA was obtained by driving the LED with peak current of 100 mA and, by exposing the system at CO2 concentration of 1000 ppm signal reduction due to absorbance around 12% was obtained.

Improving the uniformity of luminous system in radial imaging capsule endoscope system

NASA Astrophysics Data System (ADS)

Ou-Yang, Mang; Jeng, Wei-De

2013-02-01

This study concerns the illumination system in a radial imaging capsule endoscope (RICE). Uniformly illuminating the object is difficult because the intensity of the light from the light emitting diodes (LEDs) varies with angular displacement. When light is emitted from the surface of the LED, it first encounters the cone mirror, from which it is reflected, before directly passing through the lenses and complementary metal oxide semiconductor (CMOS) sensor. The light that is strongly reflected from the transparent view window (TVW) propagates again to the cone mirror, to be reflected and to pass through the lenses and CMOS sensor. The above two phenomena cause overblooming on the image plane. Overblooming causes nonuniform illumination on the image plane and consequently reduced image quality. In this work, optical design software was utilized to construct a photometric model for the optimal design of the LED illumination system. Based on the original RICE model, this paper proposes an optimal design to improve the uniformity of the illumination. The illumination uniformity in the RICE is increased from its original value of 0.128 to 0.69, greatly improving light uniformity.

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

PubMed Central

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 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. PMID:28066690

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

PubMed

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.

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

NASA Astrophysics Data System (ADS)

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.

Active tracking system for visible light communication using a GaN-based micro-LED and NRZ-OOK.

PubMed

Lu, Zhijian; Tian, Pengfei; Chen, Hong; Baranowski, Izak; Fu, Houqiang; Huang, Xuanqi; Montes, Jossue; Fan, Youyou; Wang, Hongyi; Liu, Xiaoyan; Liu, Ran; Zhao, Yuji

2017-07-24

Visible light communication (VLC) holds the promise of a high-speed wireless network for indoor applications and competes with 5G radio frequency (RF) system. Although the breakthrough of gallium nitride (GaN) based micro-light-emitting-diodes (micro-LEDs) increases the -3dB modulation bandwidth exceptionally from tens of MHz to hundreds of MHz, the light collected onto a fast photo receiver drops dramatically, which determines the signal to noise ratio (SNR) of VLC. To fully implement the practical high data-rate VLC link enabled by a GaN-based micro-LED, it requires focusing optics and a tracking system. In this paper, we demonstrate an active on-chip tracking system for VLC using a GaN-based micro-LED and none-return-to-zero on-off keying (NRZ-OOK). Using this novel technique, the field of view (FOV) was enlarged to 120° and data rates up to 600 Mbps at a bit error rate (BER) of 2.1×10 -4 were achieved without manual focusing. This paper demonstrates the establishment of a VLC physical link that shows enhanced communication quality by orders of magnitude, making it optimized for practical communication applications.

Clinical study on orofacial photonic hydration using phototherapy and biomaterials

NASA Astrophysics Data System (ADS)

Lizarelli, Rosane F. Z.; Grandi, Natália D. P.; Florez, Fernando L. E.; Grecco, Clovis; Lopes, Luciana A.

2015-06-01

Skin hydration is important to prevent aging and dysfunction of orofacial system. Nowadays, it is known that cutaneous system is linked to muscle system, then every dentist need to treat healthy facial skin, as lips, keeping orofacial functions healthy. Thirty-two patients were treated using laser and led therapy single or associated to biomaterials (dermo-cosmetics) searching for the best protocol to promote skin hydration. Using a peace of equipment to measure electric impedance, percentage of water and oil from skin, before and after different treatments were analyzed. Statistic tests using 5% and 0.1% of significance were applied and results showed that light could improve hydration of epidermis layer of facial skin. Considering just light effect, using infrared laser followed by blue led system is more effective to hydration than just blue led system application. Considering dermo-cosmetic and light, the association between both presented the best result.

A perspective perception on the applications of light-emitting diodes.

PubMed

Nair, Govind B; Dhoble, S J

2015-12-01

Light-emitting diodes (LEDs) continue to penetrate the global market; their pervasiveness clearly being felt in such diverse fields as technological, socio-economic and commercial interests. The multi-billion dollar LED market is shared by various segments, including office and household lighting, street lighting, the automobile industry, traffic signals, backlighting for hand-held devices, indoor and outdoor signs and indicators, medicine, communication systems, crop cultivation using artificial light and many more. The technological development of LEDs has undergone many phases in different parts of the world. From the early discovery of luminescence to the invention of highly efficient organic LEDs, researchers have worked with the prime purpose of improving the performance of luminaires. The need to infuse the market with more efficient and cheaper products has been prevalent from the start. LEDs are a result of this uncontrolled desire of researchers to develop superior products that would displace existing products in the market. To understand what led to the current prominence of LEDs, we give a brief historical overview of the field followed by a thorough discussion of the positive features of LEDs. This work includes the basic requirements, advantages and disadvantages of LEDs in a variety of applications. A brief description of the diverse applications of LED in fields such as lighting, indicators and displays, farming, medicine and communication is given. Considerable importance is placed on discussing the possible difficulties that must be overcome before using LEDs in commercial applications. Copyright © 2015 John Wiley & Sons, Ltd.

Evaluation of inorganic and organic light-emitting diode displays for signage application

NASA Astrophysics Data System (ADS)

Sharma, Pratibha; Kwok, Harry

2006-08-01

High-brightness, inorganic light-emitting diodes (LEDs) have been successfully utilized for edge-lighting of large displays for signage. Further interest in solid-state lighting technology has been fueled with the emergence of small molecule and polymer-based organic light-emitting diodes (OLEDs). In this paper, edgelit inorganic LED-based displays and state-of-the-art OLED-based displays are evaluated on the basis of electrical and photometric measurements. The reference size for a signage system is assumed to be 600 mm x 600mm based on the industrial usage. With the availability of high power light-emitting diodes, it is possible to develop edgelit signage systems of the standard size. These displays possess an efficacy of 18 lm/W. Although, these displays are environmentally friendly and efficient, they suffer from some inherent limitations. Homogeneity of displays, which is a prime requirement for illuminated signs, is not accomplished. A standard deviation of 3.12 lux is observed between the illuminance values on the surface of the display. In order to distribute light effectively, reflective gratings are employed. Reflective gratings aid in reducing the problem but fail to eliminate it. In addition, the overall cost of signage is increased by 50% with the use of these additional components. This problem can be overcome by the use of a distributed source of light. Hence, the organic-LEDs are considered as a possible contender. In this paper, we experimentally determine the feasibility of using OLEDs for signage applications and compare their performance with inorganic LEDs. Passive matrix, small-molecule based, commercially available OLEDs is used. Design techniques for implementation of displays using organic LEDs are also discussed. It is determined that tiled displays based on organic LEDs possess better uniformity than the inorganic LED-based displays. However, the currently available OLEDs have lower light-conversion efficiency and higher costs than the conventional, inorganic LEDs. But, signage panels based on OLEDs can be made cheaper by avoiding the use of acrylic sheet and reflective gratings. Moreover, the distributed light output and light weight of OLEDs and the potential to be built inexpensively on flexible substrates can make OLEDs more beneficial for future signage applications than the inorganic LEDs.

Survey of on-road image projection with pixel light systems

NASA Astrophysics Data System (ADS)

Rizvi, Sadiq; Knöchelmann, Marvin; Ley, Peer-Phillip; Lachmayer, Roland

2017-12-01

HID, LED and laser-based high resolution automotive headlamps, as of late known as `pixel light systems', are at the forefront of the developing technologies paving the way for autonomous driving. In addition to light distribution capabilities that outperform Adaptive Front Lighting and Matrix Beam systems, pixel light systems provide the possibility of image projection directly onto the street. The underlying objective is to improve the driving experience, in any given scenario, in terms of safety, comfort and interaction for all road users. The focus of this work is to conduct a short survey on this state-of-the-art image projection functionality. A holistic research regarding the image projection functionality can be divided into three major categories: scenario selection, technological development and evaluation design. Consequently, the work presented in this paper is divided into three short studies. Section 1 provides a brief introduction to pixel light systems and a justification for the approach adopted for this study. Section 2 deals with the selection of scenarios (and driving maneuvers) where image projection can play a critical role. Section 3 discusses high power LED and LED array based prototypes that are currently under development. Section 4 demonstrates results from an experiment conducted to evaluate the illuminance of an image space projected using a pixel light system prototype developed at the Institute of Product Development (IPeG). Findings from this work can help to identify and advance future research work relating to: further development of pixel light systems, scenario planning, examination of optimal light sources, behavioral response studies etc.

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

NASA Astrophysics Data System (ADS)

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

2017-06-01

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

Visible light communication applications in healthcare.

PubMed

Muhammad, Shoaib; Qasid, Syed Hussain Ahmed; Rehman, Shafia; Rai, Aitzaz Bin Sulltan

2016-01-01

With the development in science, methods of communication are also improved, replacing old ones with new advanced ways in an attempt to make data transfer more secure, safer for health, and time as well as cost efficient. One of such methods is Visible Light Communication, as the name implies data is transferred through a light equipment such as incandescent or florescent bulb having speed of 10 Kb/s or LEDs approaching speed of 500 Mb/s [1]. VLC uses visible light between 384 and 789 THz [2,3]. Though range is limitation of VLC, however data transfer up-to distance of 1 to 2 km although at lower transfer rate has been reached.The VLC system comprises of light source like LED and receiver equipment, however, with advancement, now LEDs are used for both sending and receiving data. LED remains on all the time, and there is no change in brightness level during the whole process, making it safe for eyes. Currently, VLC system is facing some serious technical challenges before it could be applied in daily life.

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

NASA Astrophysics Data System (ADS)

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.

Short-wavelength light beam in situ monitoring growth of InGaN/GaN green LEDs by MOCVD

PubMed Central

2012-01-01

In this paper, five-period InGaN/GaN multiple quantum well green light-emitting diodes (LEDs) were grown by metal organic chemical vapor deposition with 405-nm light beam in situ monitoring system. Based on the signal of 405-nm in situ monitoring system, the related information of growth rate, indium composition and interfacial quality of each InGaN/GaN QW were obtained, and thus, the growth conditions and structural parameters were optimized to grow high-quality InGaN/GaN green LED structure. Finally, a green LED with a wavelength of 509 nm was fabricated under the optimal parameters, which was also proved by ex situ characterization such as high-resolution X-ray diffraction, photoluminescence, and electroluminescence. The results demonstrated that short-wavelength in situ monitoring system was a quick and non-destroyed tool to provide the growth information on InGaN/GaN, which would accelerate the research and development of GaN-based green LEDs. PMID:22650991

A wirelessly controlled implantable LED system for deep brain optogenetic stimulation

PubMed Central

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

A new light emitting diode-light emitting diode portable carbon dioxide gas sensor based on an interchangeable membrane system for industrial applications.

PubMed

de Vargas-Sansalvador, I M Pérez; Fay, C; Phelan, T; Fernández-Ramos, M D; Capitán-Vallvey, L F; Diamond, D; Benito-Lopez, F

2011-08-12

A new system for CO(2) measurement (0-100%) based on a paired emitter-detector diode arrangement as a colorimetric detection system is described. Two different configurations were tested: configuration 1 (an opposite side configuration) where a secondary inner-filter effect accounts for CO(2) sensitivity. This configuration involves the absorption of the phosphorescence emitted from a CO(2)-insensitive luminophore by an acid-base indicator and configuration 2 wherein the membrane containing the luminophore is removed, simplifying the sensing membrane that now only contains the acid-base indicator. In addition, two different instrumental configurations have been studied, using a paired emitter-detector diode system, consisting of two LEDs wherein one is used as the light source (emitter) and the other is used in reverse bias mode as the light detector. The first configuration uses a green LED as emitter and a red LED as detector, whereas in the second case two identical red LEDs are used as emitter and detector. The system was characterised in terms of sensitivity, dynamic response, reproducibility, stability and temperature influence. We found that configuration 2 presented a better CO(2) response in terms of sensitivity. Copyright © 2011 Elsevier B.V. All rights reserved.

Leveraging accelerated testing of LED drivers to model the reliability of two-stage and multi-channel drivers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davis, Lynn; Perkins, Curtis; Smith, Aaron

The next wave of LED lighting technology is likely to be tunable white lighting (TWL) devices which can adjust the colour of the emitted light between warm white (~ 2700 K) and cool white (~ 6500 K). This type of lighting system uses LED assemblies of two or more colours each controlled by separate driver channels that independently adjust the current levels to achieve the desired lighting colour. Drivers used in TWL devices are inherently more complex than those found in simple SSL devices, due to the number of electrical components in the driver required to achieve this level ofmore » control. The reliability of such lighting systems can only be studied using accelerated stress tests (AST) that accelerate the aging process to time frames that can be accommodated in laboratory testing. This paper describes AST methods and findings developed from AST data that provide insights into the lifetime of the main components of one-channel and multi-channel LED devices. The use of AST protocols to confirm product reliability is necessary to ensure that the technology can meet the performance and lifetime requirements of the intended application.« less

Plant Atrium System for Food Production in NASA's Deep Space Habitat Tests

NASA Technical Reports Server (NTRS)

Massa, Gioia D.; Simpson, Morgan; Wheeler, Raymond M.; Newsham, Gerald; Stutte, Gary W.

2013-01-01

In preparation for future human exploration missions to space, NASA evaluates habitat concepts to assess integration issues, power requirements, crew operations, technology, and system performance. The concept of a Food Production System utilizes fresh foods, such as vegetables and small fruits, harvested on a continuous basis, to improve the crew's diet and quality of life. The system would need to fit conveniently into the habitat and not interfere with other components or operations. To test this concept, a plant growing "atrium" was designed to surround the lift between the lower and upper modules of the Deep Space Habitat and deployed at NASA Desert Research and Technology Studies (DRATS) test site in 2011 and at NASA Johnson Space Center in 2012. With this approach, no-utilized volume provided an area for vegetable growth. For the 2011 test, mizuna, lettuce, basil, radish and sweetpotato plants were grown in trays using commercially available red I blue LED light fixtures. Seedlings were transplanted into the atrium and cared for by the. crew. Plants were then harvested two weeks later following completion of the test. In 2012, mizuna, lettuce, and radish plants were grown similarly but under flat panel banks of white LEDs. In 2012, the crew went through plant harvesting, including sanitizing tlie leafy greens and radishes, which were then consumed. Each test demonstrated successful production of vegetables within a functional hab module. The round red I blue LEDs for the 2011 test lighting cast a purple light in the hab, and were less uniformly distributed over the plant trays. The white LED panels provided broad spectrum light with more uniform distribution. Post-test questionnaires showed that the crew enjoyed tending and consuming the plants and that the white LED light in 2012 provided welcome extra light for the main HAB AREA.

A color management system for multi-colored LED lighting

NASA Astrophysics Data System (ADS)

Chakrabarti, Maumita; Thorseth, Anders; Jepsen, Jørgen; Corell, Dennis D.; Dam-Hansen, Carsten

2015-09-01

A new color control system is described and implemented for a five-color LED light engine, covering a wide white gamut. The system combines a new way of using pre-calibrated lookup tables and a rule-based optimization of chromaticity distance from the Planckian locus with a calibrated color sensor. The color sensor monitors the chromaticity of the mixed light providing the correction factor for the current driver by using the generated lookup table. The long term stability and accuracy of the system will be experimentally investigated with target tolerance within a circle radius of 0.0013 in the uniform chromaticity diagram (CIE1976).

A short-range optical wireless transmission method based on LED

NASA Astrophysics Data System (ADS)

Miao, Meiyuan; Chen, Ailin; Zhu, Mingxing; Li, Ping; Gao, Yingming; Zou, Nianyu

2016-10-01

As to electromagnetic wave interfere and only one to one transmission problem of Bluetooth, a short-range LED optical wireless transmission method is proposed to be complementary technology in this paper. Furthermore achieved image transmission through this method. The system makes C52 to be the mater controller, transmitter got data from terminals by USB and sends modulated signals with LED. Optical signal is detected by PD, through amplified, filtered with shaping wave from, and demodulated on receiver. Then send to terminals like PC and reverted back to original image. Analysis the performance from peak power and average power, power consumption of transmitter, relationship of bit error rate and modulation mode, and influence of ambient light, respectively. The results shows that image can be received accurately which uses this method. The most distant transmission distance can get to 1m with transmitter LED source of 1w, and the transfer rate is 14.4Kbit/s with OOK modulation mode on stabilization system, the ambient light effect little to LED transmission system in normal light environment. The method is a convenient to carry LED wireless short range transmission for mobile transmission equipment as a supplement of Bluetooth short-range transmission for its ISM band interfere, and the analysis method in this paper can be a reference for other similar systems. It also proves the system is feasibility for next study.

Optimization approach to LED crop illumination inside a controlled ecological life support system

NASA Astrophysics Data System (ADS)

Avercheva, Olga; Berkovich, Yuliy A.; Bassarskaya, Elizaveta; Zhigalova, Tatiana; Smolyanina, Svetlana O.; Kochetova, Galina; Konovalova, Irina

Artificial lighting sources for growing plants can be efficiently used to control gas exchange and preserve the necessary closure of internal matter turnover in the atmosphere of a controlled ecological life support system (CELSS). However, the lighting sources contribute strongly to the equivalent mass of a CELSS. Thus, the choice of an optimal plant lighting regime largely determines the efficiency of the artificial ecosystem. Lighting systems based on light-emitting diodes (LEDs) are now considered the most promising for space applications (Massa et al., 2006). Many types of LEDs have been developed in recent years. Because of this, the problem of optimizing a lighting source for space vegetation chambers has become more difficult: we need to optimize more parameters (such as emission spectrum, light intensity, frequency of light pulses and the shape of the lighting field inside a vegetation chamber), and in a wider range of values. In this presentation we discuss approaches to optimizing the emission spectrum of a lighting source for the use in space applications, including CELSS. One of the benefits of LEDs is their narrow-band emission spectrum, which allows us to construct a lighting source with an optimal spectrum for plant growth and production. A number of experiments have shown that the reaction of plants to a narrow-band emission spectrum of LEDs is highly species-specific and affects many processes in plants. Adding a small amount of far red light to red and blue quanta increased biomass in radish and lettuce (Tamulaitis et al., 2005). Adding blue and near UV light of different wavelengths to red light decreased total sugar content in lettuce (Urbonavičiūtė et al., 2007) and Chinese cabbage (Avercheva et al., 2009). Supplemental green light improved the nutrition quality of some lettuce varieties: decreased nitrate content and increased ascorbic acid content (Samuoliene et al., 2012). It has also been shown that changes in lighting spectrum can lead to changes in hormone content in plant tissues, and to changes in the ratio of active and inactive forms of hormones (Golovatskaya, 2005; Tamulaitis et al., 2005; Minich et al., 2006). This, in turn, may lead to changes in plant growth and biomass composition. Thus, we should vary the emission spectrum of a lighting source to improve both the productivity (i.e. gas exchange) and nutrition quality of plants growing inside a CELSS. However, it is hard to find a universal spectrum for all plants and all applications. Fundamental studies of the finer effects of narrow-band light on plant growth and metabolism may be beneficial to explain these effects. On the basis of these studies, we may be able to formulate recommendations to optimize lighting sources for different plant species. One optimization approach to LED crop illumination inside CELSS could be use of white LEDs with proper addition of red LEDs. A more difficult approach is to construct lighting sources with a multiband spectrum to adjust it for specific applications experimentally.

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

PubMed

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 < 0.001). The LED endo-illuminator provides more uniform illumination with sharper shadows, less flickering and better illumination for visual perception than the arc-lamp-based system currently used.

Low-picomolar limits of detection using high-power light-emitting diodes for fluorescence.

PubMed

de Jong, Ebbing P; Lucy, Charles A

2006-05-01

Fluorescence detectors are ever more frequently being used with light-emitting diodes (LEDs) as the light source. Technological advances in the solid-state lighting industry have produced LEDs which are also suitable tools in analytical measurements. LEDs are now available which deliver 700 mW of radiometric power. While this greater light power can increase the fluorescence signal, it is not trivial to make proper use of this light. This new generation of LEDs has a large emitting area and a highly divergent beam. This presents a classic problem in optics where one must choose between either a small focused light spot, or high light collection efficiency. We have selected for light collection efficiency, which yields a light spot somewhat larger than the emitting area of the LED. This light is focused onto a flow cell. Increasing the detector cell internal diameter (i.d.) produces gains in (sensitivity)3. However, since the detector cell i.d. is smaller than the LED spot size, scattering of excitation light towards the detector remains a significant source of background signal. This can be minimized through the use of spectral filters and spatial filters in the form of pinholes. The detector produced a limit of detection (LOD) of 3 pM, which is roughly three orders of magnitude lower than other reports of LED-based fluorescence detectors. Furthermore, this LOD comes within a factor of six of much more expensive laser-based fluorescence systems. This detector has been used to monitor a separation from a gel filtration column of fluorescently labeled BSA from residual labeling reagent. The LOD of fluorescently labeled BSA is 25 pM.

Effect of various visible light photoinitiators on the polymerization and color of light-activated resins.

PubMed

Arikawa, Hiroyuki; Takahashi, Hideo; Kanie, Takahito; Ban, Seiji

2009-07-01

The purpose of this study was to investigate effects of various visible light photoinitiators on the polymerization efficiency and color of the light-activated resins. Four photoinitiators, including camphorquinone, phenylpropanedione, monoacrylphosphine oxide (TPO), and bisacrylphosphine oxide (Ir819), were used. Each photoinitiator was dissolved in a Bis-GMA and TEGDMA monomer mixture. Materials were polymerized using dental quartz-tungsten halogen lamp (QTH), plasma-ark lamp and blue LED light-curing units, and a custom-made violet LED light unit. The degree of monomer conversion and CIE L*a*b* color values of the resins were measured using a FTIR and spectral transmittance meter. The degree of monomer conversions of TPO- and Ir819-containing resins polymerized with the violet-LED unit were higher than camphorquinone-containing resin polymerized with the QTH light-curing unit. The lowest color values were observed for the TPO-containing resin. Our results indicate that the TPO photoinitiator and the violet-LED light unit may provide a useful and improved photopolymerization system for dental light-activated resins.

LED luminaire longevity strategy models comparison

NASA Astrophysics Data System (ADS)

Lemieux, Hugo; Thibault, Simon; Martel, Alain A.

2010-08-01

As energy efficiency becomes more and more important, light-emitting diodes (LEDs) are a promising alternative to traditional lighting. Indeed, the energy efficiency of LEDs is still improving as their luminosity is modulated by current. Moreover, for applications such as exterior lamp posts, their small size, directionality, colors and high frequency response allow to combine them and provide design possibilities which are impossible with any other light source. However, as any lamp, LEDs have a lumen depreciation which is a function of both current and temperature. Thus, to take advantage of the full characteristics of LEDs, LED luminaire longevity strategies must be carefully studied and planned, especially since the IES and CIE guidelines state clearly that the luminaire must maintain the rated recommended light level until the end of the system's operating life. The recommended approach for LED luminaire specification is therefore to use the end-of-life light level when evaluating the luminaire. Different power supply strategies have been simulated to determine which one maximizes energy saving and lifetime. With these results, it appears that active control can save at least 25% in energy, but the best strategy cannot be determined because of uncertainties in luminosity degradation models.

Characteristics of white LED transmission through a smoke screen

NASA Astrophysics Data System (ADS)

Zheng, Yunfei; Yang, Aiying; Feng, Lihui; Guo, Peng

2018-01-01

The characteristics of white LED transmission through a smoke screen is critical for visible light communication through a smoke screen. Based on the Mie scattering theory, the Monte Carlo transmission model is established. Based on the probability density function, the white LED sampling model is established according to the measured spectrum of a white LED and the distribution angle of the lambert model. The sampling model of smoke screen particle diameter is also established according to its distribution. We simulate numerically the influence the smoke thickness, the smoke concentration and the angle of irradiance of white LED on transmittance of the white LED. We construct a white LED smoke transmission experiment system. The measured result on the light transmittance and the smoke concentration agreed with the simulated result, and demonstrated the validity of simulation model for visible light transmission channel through a smoke screen.

The LED and fiber based calibration system for the photomultiplier array of SNO+

NASA Astrophysics Data System (ADS)

Seabra, L.; Alves, R.; Andringa, S.; Bradbury, S.; Carvalho, J.; Clark, K.; Coulter, I.; Descamps, F.; Falk, L.; Gurriana, L.; Kraus, C.; Lefeuvre, G.; Maio, A.; Maneira, J.; Mottram, M.; Peeters, S.; Rose, J.; Sinclair, J.; Skensved, P.; Waterfield, J.; White, R.; Wilson, J.; SNO+ Collaboration

2015-02-01

A new external LED/fiber light injection calibration system was designed for the calibration and monitoring of the photomultiplier array of the SNO+ experiment at SNOLAB. The goal of the calibration system is to allow an accurate and regular measurement of the photomultiplier array's performance, while minimizing the risk of radioactivity ingress. The choice in SNO+ was to use a set of optical fiber cables to convey into the detector the light pulses produced by external LEDs. The quality control was carried out using a modified test bench that was used in QC of optical fibers for TileCal/ATLAS. The optical fibers were characterized for transmission, timing and angular dispersions. This article describes the setups used for the characterization and quality control of the system based on LEDs and optical fibers and their results.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davis, Lynn; Arquit Niederberger, Anne

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

Orthodontic brackets removal under shear and tensile bond strength resistance tests - a comparative test between light sources

NASA Astrophysics Data System (ADS)

Silva, P. C. G.; Porto-Neto, S. T.; Lizarelli, R. F. Z.; Bagnato, V. S.

2008-03-01

We have investigated if a new LEDs system has enough efficient energy to promote efficient shear and tensile bonding strength resistance under standardized tests. LEDs 470 ± 10 nm can be used to photocure composite during bracket fixation. Advantages considering resistance to tensile and shear bonding strength when these systems were used are necessary to justify their clinical use. Forty eight human extracted premolars teeth and two light sources were selected, one halogen lamp and a LEDs system. Brackets for premolar were bonded through composite resin. Samples were submitted to standardized tests. A comparison between used sources under shear bonding strength test, obtained similar results; however, tensile bonding test showed distinct results: a statistical difference at a level of 1% between exposure times (40 and 60 seconds) and even to an interaction between light source and exposure time. The best result was obtained with halogen lamp use by 60 seconds, even during re-bonding; however LEDs system can be used for bonding and re-bonding brackets if power density could be increased.

Bridgeless SEPIC PFC Converter for Multistring LED Driver

NASA Astrophysics Data System (ADS)

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.

GATEWAY Report Brief: Evaluating Tunable LED Lighting in the Swedish Medical Behavioral Health Unit

DOE Office of Scientific and Technical Information (OSTI.GOV)

None, None

Summary of a GATEWAY report evaluation of a tunable LED lighting system installed in the new Swedish Medical Behavioral Health Unit in Seattle that incorporates color-tunable luminaires in common areas, and uses advanced controls for dimming and color tuning, with the goal of providing a better environment for staff and patients. The report reviews the design of the tunable lighting system, summarizes two sets of measurements, and discusses the circadian, energy, and commissioning implications as well as lessons learned from the project.

Scalable Light Module for Low-Cost, High-Efficiency Light- Emitting Diode Luminaires

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tarsa, Eric

2015-08-31

During this two-year program Cree developed a scalable, modular optical architecture for low-cost, high-efficacy light emitting diode (LED) luminaires. Stated simply, the goal of this architecture was to efficiently and cost-effectively convey light from LEDs (point sources) to broad luminaire surfaces (area sources). By simultaneously developing warm-white LED components and low-cost, scalable optical elements, a high system optical efficiency resulted. To meet program goals, Cree evaluated novel approaches to improve LED component efficacy at high color quality while not sacrificing LED optical efficiency relative to conventional packages. Meanwhile, efficiently coupling light from LEDs into modular optical elements, followed by optimallymore » distributing and extracting this light, were challenges that were addressed via novel optical design coupled with frequent experimental evaluations. Minimizing luminaire bill of materials and assembly costs were two guiding principles for all design work, in the effort to achieve luminaires with significantly lower normalized cost ($/klm) than existing LED fixtures. Chief project accomplishments included the achievement of >150 lm/W warm-white LEDs having primary optics compatible with low-cost modular optical elements. In addition, a prototype Light Module optical efficiency of over 90% was measured, demonstrating the potential of this scalable architecture for ultra-high-efficacy LED luminaires. Since the project ended, Cree has continued to evaluate optical element fabrication and assembly methods in an effort to rapidly transfer this scalable, cost-effective technology to Cree production development groups. The Light Module concept is likely to make a strong contribution to the development of new cost-effective, high-efficacy luminaries, thereby accelerating widespread adoption of energy-saving SSL in the U.S.« less

Thermal management of the remote phosphor layer in LED systems

NASA Astrophysics Data System (ADS)

Perera, Indika U.; Narendran, Nadarajah

2013-09-01

Generally in a white light-emitting diode (LED), a phosphor slurry is placed around the semiconductor chip or the phosphor is conformally coated over the chip to covert the narrowband, short-wavelength radiation to a broadband white light. Over the past few years, the remote-phosphor method has provided significant improvement in overall system efficiency by reducing the photons absorbed by the LED chip and reducing the phosphor quenching effects. However, increased light output and smaller light engine requirements are causing high radiant energy density on the remotephosphor plates, thus heating the phosphor layer. The phosphor layer temperature rise increases when the phosphor material conversion efficiency decreases. Phosphor layer heating can negatively affect performance in terms of luminous efficacy, color shift, and life. In such cases, the performance of remote-phosphor LED lighting systems can be improved by suitable thermal management to reduce the temperature of the phosphor layer. To verify this hypothesis and to understand the factors that influence the reduction in temperature, a phosphor layer was embedded in a perforated metal heatsink to remove the heat; the parameters that influence the effectiveness of heat extraction were then studied. These parameters included the heatsink-to-phosphor layer interface area and the thermal conductivity of the heatsink. The temperature of the remote-phosphor surface was measured using IR thermography. The results showed that when the heat conduction area of the heatsink increased, the phosphor layer temperature decreased, but at the same time the overall light output of the remote phosphor light engine used in this study decreased due to light absorption by the metal areas.

Integrated photocatalytic filtration array for indoor air quality control.

PubMed

Denny, Frans; Permana, Eric; Scott, Jason; Wang, Jing; Pui, David Y H; Amal, Rose

2010-07-15

Photocatalytic and filtration technologies were integrated to develop a hybrid system capable of removing and oxidizing organic pollutants from an air stream. A fluidized bed aerosol generator (FBAG) was adapted to prepare TiO(2)-loaded ventilation filters for the photodegradation of gas phase ethanol. Compared to a manually loaded filter, the ethanol photodegradation rate constant for the FBAG coated filter increased by 361%. Additionally, the presence of the photogenerated intermediate product, acetaldehyde, was reduced and the time for mineralization to CO(2) was accelerated. These improvements were attributed to the FBAG system providing a more uniform distribution of TiO(2) particles across the filter surface leading to greater accessibility by the UV light. A dual-UV-lamp system, as opposed to a single-lamp system, enhanced photocatalytic filter performance demonstrating the importance of high light irradiance and light distribution across the filter surface. Substituting the blacklight blue lamps with a UV-light-emitting-diode (UV-LED) array led to further improvement as well as suppressed the electrical energy per order (EE/O) by a factor of 6. These improvements derived from the more uniform distribution of light irradiance as well as the higher efficiency of UV-LEDs in converting electrical energy to photons.

Intelligent Luminance Control of Lighting Systems Based on Imaging Sensor Feedback

PubMed Central

Liu, Haoting; Zhou, Qianxiang; Yang, Jin; Jiang, Ting; Liu, Zhizhen; Li, Jie

2017-01-01

An imaging sensor-based intelligent Light Emitting Diode (LED) lighting system for desk use is proposed. In contrast to the traditional intelligent lighting system, such as the photosensitive resistance sensor-based or the infrared sensor-based system, the imaging sensor can realize a finer perception of the environmental light; thus it can guide a more precise lighting control. Before this system works, first lots of typical imaging lighting data of the desk application are accumulated. Second, a series of subjective and objective Lighting Effect Evaluation Metrics (LEEMs) are defined and assessed for these datasets above. Then the cluster benchmarks of these objective LEEMs can be obtained. Third, both a single LEEM-based control and a multiple LEEMs-based control are developed to realize a kind of optimal luminance tuning. When this system works, first it captures the lighting image using a wearable camera. Then it computes the objective LEEMs of the captured image and compares them with the cluster benchmarks of the objective LEEMs. Finally, the single LEEM-based or the multiple LEEMs-based control can be implemented to get a kind of optimal lighting effect. Many experiment results have shown the proposed system can tune the LED lamp automatically according to environment luminance changes. PMID:28208781

Intelligent Luminance Control of Lighting Systems Based on Imaging Sensor Feedback.

PubMed

Liu, Haoting; Zhou, Qianxiang; Yang, Jin; Jiang, Ting; Liu, Zhizhen; Li, Jie

2017-02-09

An imaging sensor-based intelligent Light Emitting Diode (LED) lighting system for desk use is proposed. In contrast to the traditional intelligent lighting system, such as the photosensitive resistance sensor-based or the infrared sensor-based system, the imaging sensor can realize a finer perception of the environmental light; thus it can guide a more precise lighting control. Before this system works, first lots of typical imaging lighting data of the desk application are accumulated. Second, a series of subjective and objective Lighting Effect Evaluation Metrics (LEEMs) are defined and assessed for these datasets above. Then the cluster benchmarks of these objective LEEMs can be obtained. Third, both a single LEEM-based control and a multiple LEEMs-based control are developed to realize a kind of optimal luminance tuning. When this system works, first it captures the lighting image using a wearable camera. Then it computes the objective LEEMs of the captured image and compares them with the cluster benchmarks of the objective LEEMs. Finally, the single LEEM-based or the multiple LEEMs-based control can be implemented to get a kind of optimal lighting effect. Many experiment results have shown the proposed system can tune the LED lamp automatically according to environment luminance changes.

White light emitting diode as potential replacement of tungsten-halogen lamp for visible spectroscopy system: a case study in the measurement of mango qualities

NASA Astrophysics Data System (ADS)

Chiong, W. L.; Omar, A. F.

2017-07-01

Non-destructive technique based on visible (VIS) spectroscopy using light emitting diode (LED) as lighting was used for evaluation of the internal quality of mango fruit. The objective of this study was to investigate feasibility of white LED as lighting in spectroscopic instrumentation to predict the acidity and soluble solids content of intact Sala Mango. The reflectance spectra of the mango samples were obtained and measured in the visible range (400-700 nm) using VIS spectroscopy illuminated under different white LEDs and tungsten-halogen lamp (pro lamp). Regression models were developed by multiple linear regression to establish the relationship between spectra and internal quality. Direct calibration transfer procedure was then applied between master and slave lighting to check on the acidity prediction results after transfer. Determination of mango acidity under white LED lighting was successfully performed through VIS spectroscopy using multiple linear regression but otherwise for soluble solids content. Satisfactory results were obtained for calibration transfer between LEDs with different correlated colour temperature indicated this technique was successfully used in spectroscopy measurement between two similar light sources in prediction of internal quality of mango.

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

PubMed

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 over the pars-plana and the distance to the retina is reduced. Only a part of the light reaches the retina and the fraction of short wavelength becomes very small. Increased safety of the system results from now being able to increase the exposure time and reduce phototoxic stress to the retina.

Flicker Vision of Selected Light Sources

NASA Astrophysics Data System (ADS)

Otomański, Przemysław; Wiczyński, Grzegorz; Zając, Bartosz

2017-10-01

The results of the laboratory research concerning a dependence of flicker vision on voltage fluctuations are presented in the paper. The research was realized on a designed measuring stand, which included an examined light source, a voltage generator with amplitude modulation supplying the light source and a positioning system of the observer with respect to the observed surface. In this research, the following light sources were used: one incandescent lamp and four LED luminaires by different producers. The research results formulate a conclusion concerning the description of the influence of voltage fluctuations on flicker viewing for selected light sources. The research results indicate that LED luminaires are less susceptible to voltage fluctuations than incandescent bulbs and that flicker vision strongly depends on the type of LED source.

Virtual reality to simulate large lighting with high efficiency LEDs

NASA Astrophysics Data System (ADS)

Blandet, Thierry; Coutelier, Gilles; Meyrueis, Patrick

2011-05-01

When a city or a local authority wishes to emphasize its historical heritage, for the lighting of its streets, setting up lights during the festive season, they call upon the skills of a lighting designer. The lighting designer proposes concepts, ideas, lighting, and to be able to present them, he makes use of simulation. On the other hand lighting technologies are evolving very rapidly and new lighting systems offer features that lighting designers are now integrating their projects. The street lights consume lot of energy; light projects are now taking into account the energy saving aspect. Lighting systems based on LEDs today provide good lighting needs, taking into account sustainable development issues while enabling new creative dimension. The lighting simulation can handle these parameters. Images or video simulation are no longer sufficient: stereoscopy and virtual reality techniques allow better communication and better understanding of projects. Virtual reality offers new possibilities of interaction, the freedom of movement in a scene, the presentation of variants or interactive simulations.

Monolithic photonic integrated circuit with a GaN-based bent waveguide

NASA Astrophysics Data System (ADS)

Cai, Wei; Qin, Chuan; Zhang, Shuai; Yuan, Jialei; Zhang, Fenghua; Wang, Yongjin

2018-06-01

Integration of a transmitter, waveguide and receiver into a single chip can generate a multicomponent system with multiple functionalities. Here, we fabricate and characterize a GaN-based photonic integrated circuit (PIC) on a GaN-on-silicon platform. With removal of the silicon and back wafer thinning of the epitaxial film, ultrathin membrane-type devices and highly confined suspended GaN waveguides were formed. Two suspended-membrane InGaN/GaN multiple-quantum-well diodes (MQW-diodes) served as an MQW light-emitting diode (MQW-LED) to emit light and an MQW photodiode (MQW-PD) to sense light. The optical interconnects between the MQW-LED and MQW-PD were achieved using the GaN bent waveguide. The GaN-based PIC consisting of an MQW-LED, waveguides and an MQW-PD forms an in-plane light communication system with a data transmission rate of 70 Mbps.

Enhanced Automated Guidance System for Horizontal Auger Boring Based on Image Processing

PubMed Central

Wu, Lingling; Wen, Guojun; Wang, Yudan; Huang, Lei; Zhou, Jiang

2018-01-01

Horizontal auger boring (HAB) is a widely used trenchless technology for the high-accuracy installation of gravity or pressure pipelines on line and grade. Differing from other pipeline installations, HAB requires a more precise and automated guidance system for use in a practical project. This paper proposes an economic and enhanced automated optical guidance system, based on optimization research of light-emitting diode (LED) light target and five automated image processing bore-path deviation algorithms. An LED target was optimized for many qualities, including light color, filter plate color, luminous intensity, and LED layout. The image preprocessing algorithm, feature extraction algorithm, angle measurement algorithm, deflection detection algorithm, and auto-focus algorithm, compiled in MATLAB, are used to automate image processing for deflection computing and judging. After multiple indoor experiments, this guidance system is applied in a project of hot water pipeline installation, with accuracy controlled within 2 mm in 48-m distance, providing accurate line and grade controls and verifying the feasibility and reliability of the guidance system. PMID:29462855

Deep ultraviolet semiconductor light sources for sensing and security

NASA Astrophysics Data System (ADS)

Shatalov, Max; Bilenko, Yuri; Yang, Jinwei; Gaska, Remis

2009-09-01

III-Nitride based deep ultraviolet (DUV) light emitting diodes (LEDs) rapidly penetrate into sensing market owing to several advantages over traditional UV sources (i.e. mercury, xenon and deuterium lamps). Small size, a wide choice of peak emission wavelengths, lower power consumption and reduced cost offer flexibility to system integrators. Short emission wavelength offer advantages for gas detection and optical sensing systems based on UV induced fluorescence. Large modulation bandwidth for these devices makes them attractive for frequency-domain spectroscopy. We will review present status of DUV LED technology and discuss recent advances in short wavelength emitters and high power LED lamps.

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

NASA Astrophysics Data System (ADS)

Saati, Ferina; Arik, Mehmet

2018-02-01

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

[Visual hygiene in LED lighting. Modern scientific imaginations].

PubMed

Deynego, V N; Kaptsov, V A

2014-01-01

There are considered a classic and modern paradigm of perception of light and its impact on human health. To consider the perception of light as a complex self-organizing synergistic system of compression of information in the process of its sequencing was supposed. This allowed to develop a complex of interrelated measures, which may become the basis for modern hygiene, and determine requirements for the led lamp with biologically adequate spectrum of the light, for which there were obtained patents in Russia, Europe and USA.

Optimized lighting method of applying shaped-function signal for increasing the dynamic range of LED-multispectral imaging system

NASA Astrophysics Data System (ADS)

Yang, Xue; Hu, Yajia; Li, Gang; Lin, Ling

2018-02-01

This paper proposes an optimized lighting method of applying a shaped-function signal for increasing the dynamic range of light emitting diode (LED)-multispectral imaging system. The optimized lighting method is based on the linear response zone of the analog-to-digital conversion (ADC) and the spectral response of the camera. The auxiliary light at a higher sensitivity-camera area is introduced to increase the A/D quantization levels that are within the linear response zone of ADC and improve the signal-to-noise ratio. The active light is modulated by the shaped-function signal to improve the gray-scale resolution of the image. And the auxiliary light is modulated by the constant intensity signal, which is easy to acquire the images under the active light irradiation. The least square method is employed to precisely extract the desired images. One wavelength in multispectral imaging based on LED illumination was taken as an example. It has been proven by experiments that the gray-scale resolution and the accuracy of information of the images acquired by the proposed method were both significantly improved. The optimum method opens up avenues for the hyperspectral imaging of biological tissue.

Optimized lighting method of applying shaped-function signal for increasing the dynamic range of LED-multispectral imaging system.

PubMed

Yang, Xue; Hu, Yajia; Li, Gang; Lin, Ling

2018-02-01

This paper proposes an optimized lighting method of applying a shaped-function signal for increasing the dynamic range of light emitting diode (LED)-multispectral imaging system. The optimized lighting method is based on the linear response zone of the analog-to-digital conversion (ADC) and the spectral response of the camera. The auxiliary light at a higher sensitivity-camera area is introduced to increase the A/D quantization levels that are within the linear response zone of ADC and improve the signal-to-noise ratio. The active light is modulated by the shaped-function signal to improve the gray-scale resolution of the image. And the auxiliary light is modulated by the constant intensity signal, which is easy to acquire the images under the active light irradiation. The least square method is employed to precisely extract the desired images. One wavelength in multispectral imaging based on LED illumination was taken as an example. It has been proven by experiments that the gray-scale resolution and the accuracy of information of the images acquired by the proposed method were both significantly improved. The optimum method opens up avenues for the hyperspectral imaging of biological tissue.

Comparison between Different Types of Sensors Used in the Real Operational Environment Based on Optical Scanning System.

PubMed

Flores-Fuentes, Wendy; Miranda-Vega, Jesús Elías; Rivas-López, Moisés; Sergiyenko, Oleg; Rodríguez-Quiñonez, Julio C; Lindner, Lars

2018-05-24

The present paper describes the experimentation in a controlled environment and a real environment using different photosensors, such as infrared light emitting diode (IRLED-as receiver), photodiode, light dependent resistor (LDR), and blue LED for the purpose of selecting those devices, which can be employed in adverse conditions, such as sunlight or artificial sources. The experiments that are described in this paper confirmed that the blue LED and phototransistor could be used as a photosensor of an Optical Scanning System (OSS), because they were less sensitive to sunlight radiation. Moreover, they are appropriate as reference sources that are selected for the experiment (blue LED flashlight and light bulb). The best experimental results that were obtained contained a digital filter that was applied to the output of the photosensor, which reduced the standard deviation for the best case for the phototransistor LED from 100.26 to 0.15. For the best case, using the blue LED, the standard deviation was reduced from 86.08 to 0.11. Using these types of devices the cost of the Optical Scanning System can be reduced and a considerable increase in resolution and accuracy.

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

PubMed Central

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

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

PubMed

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

2016-02-26

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.

A lamp light-emitting diode-induced fluorescence detector for capillary electrophoresis.

PubMed

Xu, Jing; Xiong, Yan; Chen, Shiheng; Guan, Yafeng

2008-07-15

A light-emitting diode-induced fluorescence detector (LED-FD) for capillary electrophoresis was constructed and evaluated. A lamp LED with an enhanced emission spectrum and a band pass filter was used as the excitation light source. Refractive index matching fluid (RIMF) was used in the detection cell to reduce scattering light and the noise level. The limit of detection (LOD) for fluorescein was 1.5 nM (SNR=3). The system exhibited linear responses in the range of 1 x 10(-8) to 5 x 10(-6)M (R=0.999). Application of the lamp LED-FD for the analysis of FITC-labeled ephedra herb extract by capillary electrophoresis was demonstrated.

Calculation comparison of an additive and subtractive light modulator for high-resolution pixellight headlamps

NASA Astrophysics Data System (ADS)

Held, Marcel Philipp; Ley, Peer-Phillip; Lachmayer, Roland

2018-02-01

High-resolution vehicle headlamps represent a future-oriented technology that increases traffic safety and driving comfort in the dark. A further development to current matrix beam headlamps are LED-based pixellight systems which enable additional lighting functions (e.g. the projection of navigation information on the road) to be activated for given driving scenarios. The image generation is based on spatial light modulators (SLM) such as digital micromirror devices (DMD), liquid crystal displays (LCD), liquid crystal on silicon (LCoS) devices or LED arrays. For DMD-, LCD- and LCoSbased headlamps, the optical system uses illumining optics to ensure a precise illumination of the corresponding SLM. LED arrays, however, have to use imaging optics to project the LED die onto an intermediate image plane and thus create the light distribution via an apposition of gapless juxtapositional LED die images. Nevertheless, the lambertian radiation characteristics complex the design of imaging optics regarding a highefficiency setup with maximum resolution and luminous flux. Simplifying the light source model and its emitting characteristics allows to determine a balanced setup between these parameters by using the Etendue and to ´ calculate the maximum possible efficacy and luminous flux for each technology in an early designing stage. Therefore, we present a calculation comparison of how simplifying the light source model can affect the Etendue ´ conservation and the setup design for two high-resolution technologies. The shown approach is evaluated and compared to simulation models to show the occurring deviation and its applicability.

Hybrid time-frequency domain equalization for LED nonlinearity mitigation in OFDM-based VLC systems.

PubMed

Li, Jianfeng; Huang, Zhitong; Liu, Xiaoshuang; Ji, Yuefeng

2015-01-12

A novel hybrid time-frequency domain equalization scheme is proposed and experimentally demonstrated to mitigate the white light emitting diode (LED) nonlinearity in visible light communication (VLC) systems based on orthogonal frequency division multiplexing (OFDM). We handle the linear and nonlinear distortion separately in a nonlinear OFDM system. The linear part is equalized in frequency domain and the nonlinear part is compensated by an adaptive nonlinear time domain equalizer (N-TDE). The experimental results show that with only a small number of parameters the nonlinear equalizer can efficiently mitigate the LED nonlinearity. With the N-TDE the modulation index (MI) and BER performance can be significantly enhanced.

A review of gallium nitride LEDs for multi-gigabit-per-second visible light data communications

NASA Astrophysics Data System (ADS)

Rajbhandari, Sujan; McKendry, Jonathan J. D.; Herrnsdorf, Johannes; Chun, Hyunchae; Faulkner, Grahame; Haas, Harald; Watson, Ian M.; O'Brien, Dominic; Dawson, Martin D.

2017-02-01

The field of visible light communications (VLC) has gained significant interest over the last decade, in both fibre and free-space embodiments. In fibre systems, the availability of low cost polymer optical fibre (POF) that is compatible with visible data communications has been a key enabler. In free-space applications, the availability of hundreds of THz of the unregulated spectrum makes VLC attractive for wireless communications. This paper provides an overview of the recent developments in VLC systems based on gallium nitride (GaN) light-emitting diodes (LEDs), covering aspects from sources to systems. The state-of-the-art technology enabling bandwidth of GaN LEDs in the range of >400 MHz is explored. Furthermore, advances in key technologies, including advanced modulation, equalisation, and multiplexing that have enabled free-space VLC data rates beyond 10 Gb s-1 are also outlined.

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

NASA Astrophysics Data System (ADS)

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

2014-09-01

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

Strobe Traffic Lights Warn of Approaching Emergency Vehicles

NASA Technical Reports Server (NTRS)

Bachelder, Aaron

2004-01-01

Strobe-enhanced traffic signals have been developed to aid in the preemption of road intersections for emergency vehicles. The strobe-enhanced traffic signals can be incorporated into both new and pre-existing traffic-control systems in which the traffic-signal heads are of a relatively new type based on arrays of light-emitting diodes (LEDs). The strobe-enhanced traffic signals offer a less expensive, less complex alternative to a recently developed system of LED-based warning signs placed next to traffic signals. Because of its visual complexity, the combination of traffic signals and warning signs is potentially confusing to motorists. The strobe-enhanced traffic signals present less visual clutter. In a given traffic-signal head, the strobe-enhanced traffic signal is embedded in the red LED array of the stop signal. Two strobe LED strips one horizontal and one vertical are made capable of operating separately from the rest of the red LED matrix. When no emergency vehicle is approaching, the red LED array functions as a normal stop signal: all the red LEDs are turned on and off together. When the intersection is to be preempted for an approaching emergency vehicle, only the LEDs in one of the strobe strips are lit, and are turned on in a sequence that indicates the direction of approach. For example (see figure), if an emergency vehicle approaches from the right, the strobe LEDs are lit in a sequence moving from right to left. Important to the success of strobe-enhanced traffic signals is conformance to city ordinances and close relation to pre-existing traffic standards. For instance, one key restriction is that new icons must not include arrows, so that motorists will not confuse new icons with conventional arrows that indicate allowed directions of movement. It is also critical that new displays like strobe-enhanced traffic signals be similar to displays used in traffic-control systems in large cities. For example, Charleston, South Carolina uses horizontal strobes on red traffic lights to alert motorists and thereby help motorists not to miss red lights. The one significant potential disadvantage of strobe-enhanced traffic lights is initial unfamiliarity on the part of motorists.

A MISO UCA Beamforming Dimmable LED System for Indoor Positioning

PubMed Central

Taparugssanagorn, Attaphongse; Siwamogsatham, Siwaruk; Pomalaza-Ráez, Carlos

2014-01-01

The use of a multiple input single output (MISO) transmit beamforming system using dimmable light emitting arrays (LEAs) in the form of a uniform circular array (UCA) of transmitters is proposed in this paper. With this technique, visible light communications between a transmitter and a receiver (LED reader) can be achieved with excellent performance and the receiver's position can be estimated. A hexagonal lattice alignment of LED transmitters is deployed to reduce the coverage holes and the areas of overlapping radiation. As a result, the accuracy of the position estimation is better than when using a typical rectangular grid alignment. The dimming control is done with pulse width modulation (PWM) to obtain an optimal closed loop beamforming and minimum energy consumption with acceptable lighting. PMID:24481234

Materials and Designs for High-Efficacy LED Light Engines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ibbetson, James; Gresback, Ryan

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 tomore » 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.« less

Testing a high-power LED based light source for hyperspectral imaging microscopy

NASA Astrophysics Data System (ADS)

Klomkaew, Phiwat; Mayes, Sam A.; Rich, Thomas C.; Leavesley, Silas J.

2017-02-01

Our lab has worked to develop high-speed hyperspectral imaging systems that scan the fluorescence excitation spectrum for biomedical imaging applications. Hyperspectral imaging can be used in remote sensing, medical imaging, reaction analysis, and other applications. Here, we describe the development of a hyperspectral imaging system that comprised an inverted Nikon Eclipse microscope, sCMOS camera, and a custom light source that utilized a series of high-power LEDs. LED selection was performed to achieve wavelengths of 350-590 nm. To reduce scattering, LEDs with low viewing angles were selected. LEDs were surface-mount soldered and powered by an RCD. We utilized 3D printed mounting brackets to assemble all circuit components. Spectraradiometric calibration was performed using a spectrometer (QE65000, Ocean Optics) and integrating sphere (FOIS-1, Ocean Optics). Optical output and LED driving current were measured over a range of illumination intensities. A normalization algorithm was used to calibrate and optimize the intensity of the light source. The highest illumination power was at 375 nm (3300 mW/cm2), while the lowest illumination power was at 515, 525, and 590 nm (5200 mW/cm2). Comparing the intensities supplied by each LED to the intensities measured at the microscope stage, we found there was a great loss in power output. Future work will focus on using two of the same LEDs to double the power and finding more LED and/or laser diodes and chips around the range. This custom hyperspectral imaging system could be used for the detection of cancer and the identification of biomolecules.

Wired.

ERIC Educational Resources Information Center

Conklin, Aaron R.

1998-01-01

Discusses technology's impact on scoreboard design: the development of the light-emitting diode (LED) display. How the LED system works is explained, as are the advantages and disadvantages of LED compared with incandescent lamp boards. Final comments address deciding on materials for scoreboard casings. (GR)

The Endockscope Using Next Generation Smartphones: "A Global Opportunity".

PubMed

Tse, Christina; Patel, Roshan M; Yoon, Renai; Okhunov, Zhamshid; Landman, Jaime; Clayman, Ralph V

2018-06-02

The Endockscope combines a smartphone, a battery powered flashlight and a fiberoptic cystoscope allowing for mobile videocystoscopy. We compared conventional videocystoscopy to the Endockscope paired with next generation smartphones in an ex-vivo porcine bladder model to evaluate its image quality. The Endockscope consists of a three-dimensional (3D) printed attachment that connects a smartphone to a flexible fiberoptic cystoscope plus a 1000 lumen light-emitting diode (LED) cordless light source. Video recordings of porcine cystoscopy with a fiberoptic flexible cystoscope (Storz) were captured for each mobile device (iPhone 6, iPhone 6S, iPhone 7, Samsung S8, and Google Pixel) and for the high-definition H3-Z versatile camera (HD) set-up with both the LED light source and the xenon light (XL) source. Eleven faculty urologists, blinded to the modality used, evaluated each video for image quality/resolution, brightness, color quality, sharpness, overall quality, and acceptability for diagnostic use. When comparing the Endockscope coupled to an Galaxy S8, iPhone 7, and iPhone 6S with the LED portable light source to the HD camera with XL, there were no statistically significant differences in any metric. 82% and 55% of evaluators considered the iPhone 7 + LED light source and iPhone 6S + LED light, respectively, appropriate for diagnostic purposes as compared to 100% who considered the HD camera with XL appropriate. The iPhone 6 and Google Pixel coupled with the LED source were both inferior to the HD camera with XL in all metrics. The Endockscope system with a LED light source when coupled with either an iPhone 7 or Samsung S8 (total cost: $750) is comparable to conventional videocystoscopy with a standard camera and XL light source (total cost: $45,000).

Plant lighting system with five wavelength-band light-emitting diodes providing photon flux density and mixing ratio control

PubMed Central

2012-01-01

Background Plant growth and development depend on the availability of light. Lighting systems therefore play crucial roles in plant studies. Recent advancements of light-emitting diode (LED) technologies provide abundant opportunities to study various plant light responses. The LED merits include solidity, longevity, small element volume, radiant flux controllability, and monochromaticity. To apply these merits in plant light response studies, a lighting system must provide precisely controlled light spectra that are useful for inducing various plant responses. Results We have developed a plant lighting system that irradiated a 0.18 m2 area with a highly uniform distribution of photon flux density (PFD). The average photosynthetic PFD (PPFD) in the irradiated area was 438 micro-mol m–2 s–1 (coefficient of variation 9.6%), which is appropriate for growing leafy vegetables. The irradiated light includes violet, blue, orange-red, red, and far-red wavelength bands created by LEDs of five types. The PFD and mixing ratio of the five wavelength-band lights are controllable using a computer and drive circuits. The phototropic response of oat coleoptiles was investigated to evaluate plant sensitivity to the light control quality of the lighting system. Oat coleoptiles irradiated for 23 h with a uniformly distributed spectral PFD (SPFD) of 1 micro-mol m–2 s–1 nm–1 at every peak wavelength (405, 460, 630, 660, and 735 nm) grew almost straight upwards. When they were irradiated with an SPFD gradient of blue light (460 nm peak wavelength), the coleoptiles showed a phototropic curvature in the direction of the greater SPFD of blue light. The greater SPFD gradient induced the greater curvature of coleoptiles. The relation between the phototropic curvature (deg) and the blue-light SPFD gradient (micro-mol m–2 s–1 nm–1 m–1) was 2 deg per 1 micro-mol m–2 s–1 nm–1 m–1. Conclusions The plant lighting system, with a computer with a graphical user interface program, can control the PFD and mixing ratios of five wavelength-band lights. A highly uniform PFD distribution was achieved, although an intentionally distorted PFD gradient was also created. Phototropic responses of oat coleoptiles to the blue light gradient demonstrated the merit of fine controllability of this plant lighting system. PMID:23173915

Study of Selecting on Light Source Used for Micro-algae Cultivation in Space

NASA Astrophysics Data System (ADS)

Ai, Weidang; Ai, Weidang; Guo, Shuang-Sheng; Gao, Feng; Tang, Yong-Kang; Qin, Li-Feng

To select suitable light source for micro-algae cultivation in future space station, the selected Spirulina plastensis(No.7) were cultured under different lightening qualities, including six light sources that were made up of different combinations of red and blue light-emitting diode(LED). The growth, photosynthetic efficiency and nutrition quality of the Spirulina, were analyzed. From the experiments, the red light may promote the cumulation of biomass of the Spirulina, and the cumulating rate was the highest under all red light source, but the syntheses of protein, phycobiliprotein, β-carotene, VE and other nutrients needs a certain portion of blue light; yet, the complete blue light condition is not favorable to the growth of Spirulina, and may bring pollution by chlorella and other kinds of micro-algae. It is concluded that the LEDs can be used as the light resource of micro-algae cultivation. The normal growth and development of microalgae need two light sources of both red and blue LEDs. The comprehensive analyses of the various factors that affect the growth of Spirulina, such as nutrition quality and photosynthetic activities, etc., showed that the combination of 80% red and 20% blue LED is the optimum one among those tested combinations. Key word: light-emitting diode; micro-algae; controlled ecological life support system (CELSS); space cultivation

Characterization of an LED based photoreactor to degrade 4-chlorophenol in an aqueous medium using coumarin (C-343) sensitized TiO2.

PubMed

Ghosh, Jyoti P; Langford, Cooper H; Achari, Gopal

2008-10-16

A detailed performance evaluation of a simple high intensity LED based photoreactor exploiting a narrow wavelength range of the LED to match the spectrum of a dye in a photocatalysis system is reported. A dye sensitized (coumarin-343, lambda max = 446 nm) TiO 2 photocatalyst was used for the degradation of 4-chlorophenol (4-CP) in an aqueous medium using the 436 nm LED based photoreactor. The LED reactor performed competitively with a conventional multilamp reactor and sunlight in the degradation of 4-CP. Light intensities entering the reaction vessel were measured by conventional ferrioxalate actinometry. The results can be fitted by approximate first order kinetic behavior in this system. Hydroxyl radicals were detected by spin trapping EPR, and effects of OH radical quenchers on kinetics suggest that the reaction is initiated by these radicals or their equivalents. LEDs operating at competitive intensities offer a number of advantages to the photochemist or the environmental engineer via long life, efficient current to light conversion, narrow bandwidth, forward directed output, and direct current power for remote operation. Matching light source spectrum to chromophore is a key.

Color coded multiple access scheme for bidirectional multiuser visible light communications in smart home technologies

NASA Astrophysics Data System (ADS)

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

2015-10-01

In optical wireless communications, multiple channel transmission is an attractive solution to enhancing capacity and system performance. A new modulation scheme called color coded multiple access (CCMA) for bidirectional multiuser visible light communications (VLC) is presented for smart home applications. The proposed scheme uses red, green and blue (RGB) light emitting diodes (LED) for downlink and phosphor based white LED (P-LED) for uplink to establish a bidirectional VLC and also employs orthogonal codes to support multiple users and devices. The downlink transmission for data user devices and smart home devices is provided using red and green colors from the RGB LEDs, respectively, while uplink transmission from both types of devices is performed using the blue color from P-LEDs. Simulations are conducted to verify the performance of the proposed scheme. It is found that the proposed bidirectional multiuser scheme is efficient in terms of data rate and performance. In addition, since the proposed scheme uses RGB signals for downlink data transmission, it provides flicker-free illumination that would lend itself to multiuser VLC system for smart home applications.

Modeling of light-emitting diode wavefronts for the optimization of transmission holograms.

PubMed

Karthaus, Daniela; Giehl, Markus; Sandfuchs, Oliver; Sinzinger, Stefan

2017-06-20

The objective of applying transmission holograms in automotive headlamp systems requires the adaptation of holograms to divergent and polychromatic light sources like light-emitting diodes (LEDs). In this paper, four different options to describe the scalar light waves emitted by a typical automotive LED are regarded. This includes a new approach to determine the LED's wavefront from interferometric measurements. Computer-generated holograms are designed considering the different LED approximations and recorded into a photopolymer. The holograms are reconstructed with the LED and the resulting images are analyzed to evaluate the quality of the wave descriptions. In this paper, we show that our presented new approach leads to better results in comparison to other wave descriptions. The enhancement is evaluated by the correlation between reconstructed and ideal images. In contrast to the next best approximation, a spherical wave, the correlation coefficient increased by 0.18% at 532 nm, 1.69% at 590 nm, and 0.75% at 620 nm.

The Effect of Spectral Quality on Daily Patterns of Gas Exchange, Biomass Gain, and Water-Use-Efficiency in Tomatoes and Lisianthus: An Assessment of Whole Plant Measurements

PubMed Central

Lanoue, Jason; Leonardos, Evangelos D.; Ma, Xiao; Grodzinski, Bernard

2017-01-01

Advancements in light-emitting diode (LED) technology have made them a viable alternative to current lighting systems for both sole and supplemental lighting requirements. Understanding how wavelength specific LED lighting can affect plants is thus an area of great interest. Much research is available on the wavelength specific responses of leaves from multiple crops when exposed to long-term wavelength specific lighting. However, leaf measurements do not always extrapolate linearly to the complexities which are found within a whole plant canopy, namely mutual shading and leaves of different ages. Taken together, both tomato (Solanum lycopersicum) leaves under short-term illumination and lisianthus (Eustoma grandiflorum) and tomato whole plant diurnal patterns of plants acclimated to specific lighting indicate wavelength specific responses of both H2O and CO2 gas exchanges involved in the major growth parameters of a plant. Tomato leaves grown under a white light source indicated an increase in transpiration rate and internal CO2 concentration and a subsequent decrease in water-use-efficiency (WUE) when exposed to a blue LED light source compared to a green LED light source. Interestingly, the maximum photosynthetic rate was observed to be similar. Using plants grown under wavelength specific supplemental lighting in a greenhouse, a decrease in whole plant WUE was seen in both crops under both red-blue (RB) and red-white (RW) LEDs when compared to a high pressure sodium (HPS) light. Whole plant WUE was decreased by 31% under the RB LED treatment for both crops compared to the HPS treatment. Tomato whole plant WUE was decreased by 25% and lisianthus whole plant WUE was decreased by 15% when compared to the HPS treatment when grown under RW LED. The understanding of the effects of wavelength specific lighting on both leaf and whole plant gas exchange has significant implications on basic academic research as well as commercial greenhouse production. PMID:28676816

The Effect of Spectral Quality on Daily Patterns of Gas Exchange, Biomass Gain, and Water-Use-Efficiency in Tomatoes and Lisianthus: An Assessment of Whole Plant Measurements.

PubMed

Lanoue, Jason; Leonardos, Evangelos D; Ma, Xiao; Grodzinski, Bernard

2017-01-01

Advancements in light-emitting diode (LED) technology have made them a viable alternative to current lighting systems for both sole and supplemental lighting requirements. Understanding how wavelength specific LED lighting can affect plants is thus an area of great interest. Much research is available on the wavelength specific responses of leaves from multiple crops when exposed to long-term wavelength specific lighting. However, leaf measurements do not always extrapolate linearly to the complexities which are found within a whole plant canopy, namely mutual shading and leaves of different ages. Taken together, both tomato ( Solanum lycopersicum ) leaves under short-term illumination and lisianthus ( Eustoma grandiflorum ) and tomato whole plant diurnal patterns of plants acclimated to specific lighting indicate wavelength specific responses of both H 2 O and CO 2 gas exchanges involved in the major growth parameters of a plant. Tomato leaves grown under a white light source indicated an increase in transpiration rate and internal CO 2 concentration and a subsequent decrease in water-use-efficiency (WUE) when exposed to a blue LED light source compared to a green LED light source. Interestingly, the maximum photosynthetic rate was observed to be similar. Using plants grown under wavelength specific supplemental lighting in a greenhouse, a decrease in whole plant WUE was seen in both crops under both red-blue (RB) and red-white (RW) LEDs when compared to a high pressure sodium (HPS) light. Whole plant WUE was decreased by 31% under the RB LED treatment for both crops compared to the HPS treatment. Tomato whole plant WUE was decreased by 25% and lisianthus whole plant WUE was decreased by 15% when compared to the HPS treatment when grown under RW LED. The understanding of the effects of wavelength specific lighting on both leaf and whole plant gas exchange has significant implications on basic academic research as well as commercial greenhouse production.

Miniaturized high throughput detection system for capillary array electrophoresis on chip with integrated light emitting diode array as addressed ring-shaped light source.

PubMed

Ren, Kangning; Liang, Qionglin; Mu, Xuan; Luo, Guoan; Wang, Yiming

2009-03-07

A novel miniaturized, portable fluorescence detection system for capillary array electrophoresis (CAE) on a microfluidic chip was developed, consisting of a scanning light-emitting diode (LED) light source and a single point photoelectric sensor. Without charge coupled detector (CCD), lens, fibers and moving parts, the system was extremely simplified. Pulsed driving of the LED significantly increased the sensitivity, and greatly reduced the power consumption and photobleaching effect. The highly integrated system was robust and easy to use. All the advantages realized the concept of a portable micro-total analysis system (micro-TAS), which could work on a single universal serial bus (USB) port. Compared with traditional CAE detecting systems, the current system could scan the radial capillary array with high scanning rate. An 8-channel CAE of fluorescein isothiocyanate (FITC) labeled arginine (Arg) on chip was demonstrated with this system, resulting in a limit of detection (LOD) of 640 amol.

A portable inspection system to estimate direct glare of various LED modules

NASA Astrophysics Data System (ADS)

Chen, Po-Li; Liao, Chun-Hsiang; Li, Hung-Chung; Jou, Shyh-Jye; Chen, Han-Ting; Lin, Yu-Hsin; Tang, Yu-Hsiang; Peng, Wei-Jei; Kuo, Hui-Jean; Sun, Pei-Li; Lee, Tsung-Xian

2015-07-01

Glare is caused by both direct and indirect light sources and discomfort glare produces visual discomfort, annoyance, or loss in visual performance and visibility. Direct glare is caused by light sources in the field of view whereas reflected glare is caused by bright reflections from polished or glossy surfaces that are reflected toward an individual. To improve visual comfort of our living environment, a portable inspection system to estimate direct glare of various commercial LED modules with the range of color temperature from 3100 K to 5300 K was developed in this study. The system utilized HDR images to obtain the illumination distribution of LED modules and was first calibrated for brightness and chromaticity and corrected with flat field, dark-corner and curvature by the installed algorithm. The index of direct glare was then automatically estimated after image capturing, and the operator can recognize the performance of LED modules and the possible effects on human being once the index was out of expecting range. In the future, we expect that the quick-response smart inspection system can be applied in several new fields and market, such as home energy diagnostics, environmental lighting and UGR monitoring and popularize it in several new fields.

Indoor high precision three-dimensional positioning system based on visible light communication using modified genetic algorithm

NASA Astrophysics Data System (ADS)

Chen, Hao; Guan, Weipeng; Li, Simin; Wu, Yuxiang

2018-04-01

To improve the precision of indoor positioning and actualize three-dimensional positioning, a reversed indoor positioning system based on visible light communication (VLC) using genetic algorithm (GA) is proposed. In order to solve the problem of interference between signal sources, CDMA modulation is used. Each light-emitting diode (LED) in the system broadcasts a unique identity (ID) code using CDMA modulation. Receiver receives mixed signal from every LED reference point, by the orthogonality of spreading code in CDMA modulation, ID information and intensity attenuation information from every LED can be obtained. According to positioning principle of received signal strength (RSS), the coordinate of the receiver can be determined. Due to system noise and imperfection of device utilized in the system, distance between receiver and transmitters will deviate from the real value resulting in positioning error. By introducing error correction factors to global parallel search of genetic algorithm, coordinates of the receiver in three-dimensional space can be determined precisely. Both simulation results and experimental results show that in practical application scenarios, the proposed positioning system can realize high precision positioning service.

Design and Implementation of a Smart LED Lighting System Using a Self Adaptive Weighted Data Fusion Algorithm

PubMed Central

Sung, Wen-Tsai; Lin, Jia-Syun

2013-01-01

This work aims to develop a smart LED lighting system, which is remotely controlled by Android apps via handheld devices, e.g., smartphones, tablets, and so forth. The status of energy use is reflected by readings displayed on a handheld device, and it is treated as a criterion in the lighting mode design of a system. A multimeter, a wireless light dimmer, an IR learning remote module, etc. are connected to a server by means of RS 232/485 and a human computer interface on a touch screen. The wireless data communication is designed to operate in compliance with the ZigBee standard, and signal processing on sensed data is made through a self adaptive weighted data fusion algorithm. A low variation in data fusion together with a high stability is experimentally demonstrated in this work. The wireless light dimmer as well as the IR learning remote module can be instructed directly by command given on the human computer interface, and the reading on a multimeter can be displayed thereon via the server. This proposed smart LED lighting system can be remotely controlled and self learning mode can be enabled by a single handheld device via WiFi transmission. Hence, this proposal is validated as an approach to power monitoring for home appliances, and is demonstrated as a digital home network in consideration of energy efficiency.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alstone, Peter; Jacobson, Arne; Mills, Evan

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 bymore » 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.« less

Ultraviolet light emitting diodes and bio-aerosol sensing

NASA Astrophysics Data System (ADS)

Davitt, Kristina M.

Recent interest in compact ultraviolet (UV) light emitters has produced advances in material quality and device performance from aluminum-rich alloys of the nitride semiconductor system. The epitaxial growth of device structures from this material poses remarkable challenges, and state-of-the-art in semiconductor UV light sources at wavelengths shorter than 350 nm is currently limited to LEDs. A portion of the work presented in this thesis involves the design and characterization of UV LED structures, with particular focus on sub-300 nm LEDs which have only been demonstrated within the last four years. Emphasis has been placed on the integration of early devices with modest efficiencies and output powers into a practical, fluorescence-based bio-sensing instrument. The quality of AlGaInN and AlGaN-based materials is characterized by way of the performance of 340 nm and 290 nm LEDs respectively. A competitive level of device operation is achieved, although much room remains for improvement in the efficiency of light emission from this material system. A preliminary investigation of 300 nm LEDs grown on bulk AIN shows promising electrical and optical characteristics, and illustrates the numerous advantages that this native substrate offers to the epitaxy of wide bandgap nitride semiconductors. The application of UV LEDs to the field of bio-aerosol sensing is pursued by constructing an on-the-fly fluorescence detection system. A linear array of UV LEDs is designed and implemented, and the capability of test devices to excite native fluorescence from bacterial spores is established. In order to fully capitalize on the reduction in size afforded by LEDs, effort is invested in re-engineering the remaining sensor components. Operation of a prototype system for physically sorting bio-aerosols based on fluorescence spectra acquired in real-time from single airborne particles excited by a UV-LED array is demonstrated using the bio-fluorophores NADH and tryptophan. Sensor performance is shown to be ultimately linked to the material quality of high aluminum fraction nitrides, and is expected to show progress as this field matures.

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

NASA Astrophysics Data System (ADS)

Kobashi, Katsuya; Taguchi, Tsunemasa

2005-03-01

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

Photosynthesis under artificial light: the shift in primary and secondary metabolism

PubMed Central

Darko, Eva; Heydarizadeh, Parisa; Schoefs, Benoît; Sabzalian, Mohammad R.

2014-01-01

Providing an adequate quantity and quality of food for the escalating human population under changing climatic conditions is currently a great challenge. In outdoor cultures, sunlight provides energy (through photosynthesis) for photosynthetic organisms. They also use light quality to sense and respond to their environment. To increase the production capacity, controlled growing systems using artificial lighting have been taken into consideration. Recent development of light-emitting diode (LED) technologies presents an enormous potential for improving plant growth and making systems more sustainable. This review uses selected examples to show how LED can mimic natural light to ensure the growth and development of photosynthetic organisms, and how changes in intensity and wavelength can manipulate the plant metabolism with the aim to produce functionalized foods. PMID:24591723

Modulation selection for visible light communications using lighting LEDs

NASA Astrophysics Data System (ADS)

Siuzdak, Jerzy

2015-09-01

The paper analyzes suitability of various spectrally efficient modulations (PAM, CAP, OFDM/DMT) in a VLC system using lighting LEDs as a transmitter. Although under ideal conditions all modulation have similar efficiency i.e. they produce similar throughputs with a given BER, their practical performances are different. For example, the level of nonlinear distortions generated by each modulation is the least for PAM and by far the greatest for OFDM/DMT locating CAP in the middle. The suitability of various OFDM/DMT variants in a VLC LED link was also analyzed proving that the asymmetrically clipped (ACO) OFDM has a worse performance as compared with DC biased (DCO) OFDM.

Multispectral imaging of the ocular fundus using light emitting diode illumination

NASA Astrophysics Data System (ADS)

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.

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

PubMed

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.

Solid-state turn coordinator display

NASA Technical Reports Server (NTRS)

Meredith, B. D.; Crouch, R. K.; Kelly, W. L., IV

1975-01-01

A solid state turn coordinator display which employs light emitting diodes (LED's) as the display medium was developed to demonstrate the feasibility of such displays for aircraft applications. The input to the display is supplied by a fluidic inertial rate sensor used in an aircraft wing leveler system. The display is composed of the LED radial display face and the electronics necessary to address and drive the individual lines of LED's. Three levels of brightness are provided to compensate for the different amounts of ambient light present in the cockpit.

Scientific Verification Test of Orbitec Deployable Vegetable Production System for Salad Crop Growth on ISS- Gas Exchange System design and function

NASA Technical Reports Server (NTRS)

Eldemire, Ashleigh

2007-01-01

The ability to produce and maintain salad crops during long term missions would be a great benefit to NASA; the renewable food supply would save cargo space, weight and money. The ambient conditions of previous ground controlled crop plant experiments do not reflect the microgravity and high CO2 concentrations present during orbit. It has been established that microgravity does not considerably alter plant growth. (Monje, Stutte, Chapman, 2005). To support plants in a space-craft environment efficient and effective lighting and containment units are necessary. Three lighting systems were previously evaluated for radish growth in ambient air; fluorescent lamps in an Orbitec Biomass Production System Educational (BPSE), a combination of red, blue, and green LED's in a Deployable Vegetable Production System (Veggie), and a combination of red and blue LED's in a Veggie. When mass measurements compared the entire possible growing area vs. power consumed by the respective units, the Veggies clearly exceeded the BPSE indicating that the LED units were a more resource efficient means of growing radishes under ambient conditions in comparison with fluorescent lighting. To evaluate the most productive light treatment system for a long term space mission a more closely simulated ISS environment is necessary. To induce a CO2 dense atmosphere inside the Veggie's and BPSE a gas exchange system has been developed to maintain a range of 1000-1200 ppm CO2 during a 21-day light treatment experiment. This report details the design and function of the gas exchange system. The rehabilitation, trouble shooting, maintenance and testing of the gas exchange system have been my major assignments. I have also contributed to the planting, daily measurements and harvesting of the radish crops 21-day light treatment verification test.

L70 life prediction for solid state lighting using Kalman Filter and Extended Kalman Filter based models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lall, Pradeep; Wei, Junchao; Davis, Lynn

2013-08-08

Solid-state lighting (SSL) luminaires containing light emitting diodes (LEDs) have the potential of seeing excessive temperatures when being transported across country or being stored in non-climate controlled warehouses. They are also being used in outdoor applications in desert environments that see little or no humidity but will experience extremely high temperatures during the day. This makes it important to increase our understanding of what effects high temperature exposure for a prolonged period of time will have on the usability and survivability of these devices. Traditional light sources “burn out” at end-of-life. For an incandescent bulb, the lamp life is definedmore » by B50 life. However, the LEDs have no filament to “burn”. The LEDs continually degrade and the light output decreases eventually below useful levels causing failure. Presently, the TM-21 test standard is used to predict the L70 life of LEDs from LM-80 test data. Several failure mechanisms may be active in a LED at a single time causing lumen depreciation. The underlying TM-21 Model may not capture the failure physics in presence of multiple failure mechanisms. Correlation of lumen maintenance with underlying physics of degradation at system-level is needed. In this paper, Kalman Filter (KF) and Extended Kalman Filters (EKF) have been used to develop a 70-percent Lumen Maintenance Life Prediction Model for LEDs used in SSL luminaires. Ten-thousand hour LM-80 test data for various LEDs have been used for model development. System state at each future time has been computed based on the state space at preceding time step, system dynamics matrix, control vector, control matrix, measurement matrix, measured vector, process noise and measurement noise. The future state of the lumen depreciation has been estimated based on a second order Kalman Filter model and a Bayesian Framework. The measured state variable has been related to the underlying damage using physics-based models. Life prediction of L70 life for the LEDs used in SSL luminaires from KF and EKF based models have been compared with the TM-21 model predictions and experimental data.« less

Design of LED projector based on gradient-index lens

NASA Astrophysics Data System (ADS)

Qian, Liyong; Zhu, Xiangbing; Cui, Haitian; Wang, Yuanhang

2018-01-01

In this study, a new type of projector light path is designed to eliminate the deficits of existing projection systems, such as complex structure and low collection efficiency. Using a three-color LED array as the lighting source, by means of the special optical properties of a gradient-index lens, the complex structure of the traditional projector is simplified. Traditional components, such as the color wheel, relay lens, and mirror, become unnecessary. In this way, traditional problems, such as low utilization of light energy and loss of light energy, are solved. With the help of Zemax software, the projection lens is optimized. The optimized projection lens, LED, gradient-index lens, and digital micromirror device are imported into Tracepro. The ray tracing results show that both the utilization of light energy and the uniformity are improved significantly.

LED backlight system with fiber-optic red, green, blue to white color combiner

NASA Astrophysics Data System (ADS)

Kim, Hye R.; Jeong, Yunsong; Lee, Jhang-Woo; Oh, Kyunghwan

2006-09-01

As an application in the backlight system of small LCD display, we realized a pure white light source by mixing red, green, blue (RGB) lights using a 3 X 3 Hard Plastic Cladding Fiber (HPCF) coupler. We also proposed the 0.44 inch LED backlight system with these fiber-optic pure white sources and characterized its illumination characteristics. Using optimized fusion-tapering technique, we fabricated HPCF coupler which combines three input lights over the circularly formed waist. HPCF has the core diameter of 200 μm and clad diameter of 230 μm. The fabricated 3 X 3 HPCF coupler has the perfect uniformity of about 0.3 dB, low insertion loss of 5.5 dB, and low excess loss of 0.8 dB, which shows excellent uniform power splitting ratio. In order to improve the transmission performance, The RGB chip LEDs were butt-coupled directly to the ferruled input ports of the coupler and packaged by TO46-can type. In the produced white color by HPCF coupler, the photometric brightness at the circular endface of outputs of HPCF coupler was in a rage of 10062 ~ 10094 cd/m2. The fiber optic white color combiner provides tunable white sources excluding heat source and having thickness of 200 μm. We also proposed a 0.44 inch LED backlight system with these fiber-optic pure white sources. With the proposed device, we obtain the improved uniformity in luminance distribution and wide color gamut by using the white light mixing red, green and blue lights.

The Use of NASA Light-Emitting Diode Near-Infrared Technology for Biostimulation

NASA Technical Reports Server (NTRS)

Whelan, Harry T.

2002-01-01

Studies on cells exposed to microgravity and hypergravity indicate that human cells need gravity to stimulate growth. As the gravitational force increases or decreases, the cell function responds in a linear fashion. This poses significant health risks for astronauts in long-term spaceflight. The application of light therapy with the use of NASA LEDs will significantly improve the medical care that is available to astronauts on long-term space missions. NASA LEDs stimulate the basic energy processes in the mitochondria (energy compartments) of each cell, particularly when near-infrared light is used to activate the color sensitive chemicals (chromophores, cytochrome systems) inside. Optimal LED wavelengths include 680, 730 and 880 nm and our laboratory has improved the healing of wounds in laboratory animals by using both NASA LED light and hyperbaric oxygen. Furthermore, DNA synthesis in fibroblasts and muscle cells has been quintupled using NASA LED light alone, in a single application combining 680, 730 and 880 nm each at 4 Joules per centimeter squared. Muscle and bone atrophy are well documented in astronauts, and various minor injuries occurring in space have been reported not to heal until landing on Earth. An LED blanket device may be used for the prevention of bone and muscle atrophy in astronauts. The depth of near-infrared light penetration into human tissue has been measured spectroscopically.

Computational Modeling to Limit the Impact Displays and Indicator Lights Have on Habitable Volume Operational Lighting Constraints

NASA Technical Reports Server (NTRS)

Clark, T. E.; Salazr, G. A; Brainard, G. C.

2016-01-01

The goal of this investigation is to determine design limitations and architectural solutions that limit the impact light from displays and indicator lamps have on the operational environment task lighting and lighting countermeasure spectrum constraints. It is concerning that this innovative architectural lighting system, could be compromised by spectrums from display systems, architectural materials, and structures that are not considered as part a full system design implementation. The introduction of many Commercial Off the Shelf (COTS) products to the spacecraft volume that contain LEDs, without consideration to the human factors and biological constraints, is another problem. Displays and indicators are a necessary part of the spacecraft and it is the goal of this research project to determine constraints and solutions that allow these systems to be integrated while minimizing how the lighting environment is modified by them. Due to the potentially broad scope of this endeavor, the project team developed constraints for the evaluation. The evaluation will be on a set of tasks that required significant exposure in the same environment while having a large chance of impacting the light spectrum the crew is expected to receive from the architectural lighting system. The team plans to use recent HRP research on "Net Habitable Volume" [1] to provide the boundary conditions for volume size. A Zemax ® lighting model was developed of a small enclosure that had high intensity overhead lighting and a standard intensity display with LED indicator arrays. The computer model demonstrated a work surface illuminated at a high level by the overhead light source compared to displays and indicators whose light is parallel to the work plane. The overhead lighting oversaturated spectral contributions from the display and indicator at the task work surface. Interestingly, when the observer looked at the displays and LEDs within the small enclosure, their spectral contribution was significant but could be reduced by reflecting overhead light from the wall(s) to the observer. Direct observation of displays and LEDs are an issue because the user's viewing area is a display, not an illuminated work surface. Since avionics command centers consume significant crew time, the tasks that seemed at higher risk for unwanted spectral contributions as an operational volume with significant quantity of displays and indicators that were either under direct observation of the crew or impacting a volume the crew may be required to sleep in.

Optical design of an in vivo laparoscopic lighting system

NASA Astrophysics Data System (ADS)

Liu, Xiaolong; Abdolmalaki, Reza Yazdanpanah; Mancini, Gregory J.; Tan, Jindong

2017-12-01

This paper proposes an in vivo laparoscopic lighting system design to address the illumination issues, namely poor lighting uniformity and low optical efficiency, existing in the state-of-the-art in vivo laparoscopic cameras. The transformable design of the laparoscopic lighting system is capable of carrying purposefully designed freeform optical lenses for achieving lighting performance with high illuminance uniformity and high optical efficiency in a desired target region. To design freeform optical lenses for extended light sources such as LEDs with Lambertian light intensity distributions, we present an effective and complete freeform optical design method. The procedures include (1) ray map computation by numerically solving a standard Monge-Ampere equation; (2) initial freeform optical surface construction by using Snell's law and a lens volume restriction; (3) correction of surface normal vectors due to accumulated errors from the initially constructed surfaces; and (4) feedback modification of the solution to deal with degraded illuminance uniformity caused by the extended sizes of the LEDs. We employed an optical design software package to evaluate the performance of our laparoscopic lighting system design. The simulation results show that our design achieves greater than 95% illuminance uniformity and greater than 89% optical efficiency (considering Fresnel losses) for illuminating the target surgical region.

LED-based endoscopic light source for spectral imaging

NASA Astrophysics Data System (ADS)

Browning, Craig M.; Mayes, Samuel; Favreau, Peter; Rich, Thomas C.; Leavesley, Silas J.

2016-03-01

Colorectal cancer is the United States 3rd leading cancer in death rates.1 The current screening for colorectal cancer is an endoscopic procedure using white light endoscopy (WLE). There are multiple new methods testing to replace WLE, for example narrow band imaging and autofluorescence imaging.2 However, these methods do not meet the need for a higher specificity or sensitivity. The goal for this project is to modify the presently used endoscope light source to house 16 narrow wavelength LEDs for spectral imaging in real time while increasing sensitivity and specificity. The process to do such was to take an Olympus CLK-4 light source, replace the light and electronics with 16 LEDs and new circuitry. This allows control of the power and intensity of the LEDs. This required a larger enclosure to house a bracket system for the solid light guide (lightpipe), three new circuit boards, a power source and National Instruments hardware/software for computer control. The results were a successfully designed retrofit with all the new features. The LED testing resulted in the ability to control each wavelength's intensity. The measured intensity over the voltage range will provide the information needed to couple the camera for imaging. Overall the project was successful; the modifications to the light source added the controllable LEDs. This brings the research one step closer to the main goal of spectral imaging for early detection of colorectal cancer. Future goals will be to connect the camera and test the imaging process.

Dual LED/incandescent security fixture

DOEpatents

Gauna, Kevin Wayne

2005-06-21

A dual LED and incandescent security lighting system uses a hybrid approach to LED illumination. It combines an ambient LED illuminator with a standard incandescent lamp on a motion control sensor. The LED illuminator will activate with the onset of darkness (daylight control) and typically remain on during the course of the night ("always on"). The LED illumination, typically amber, is sufficient to provide low to moderate level lighting coverage to the wall and ground area adjacent to and under the fixture. The incandescent lamp is integrated with a motion control circuit and sensor. When movement in the field of view is detected (after darkness), the incandescent lamp is switched on, providing an increased level of illumination to the area. Instead of an "always on" LED illuminator, the LEDs may also be switched off when the incandescent lamp is switched on.

A simple and cost-effective molecular diagnostic system and DNA probes synthesized by light emitting diode photolithography

NASA Astrophysics Data System (ADS)

Oleksandrov, Sergiy; Kwon, Jung Ho; Lee, Ki-chang; Sujin-Ku; Paek, Mun Cheol

2014-09-01

This work introduces a novel chip to be used in the future as a simple and cost-effective method for creating DNA arrays using light emission diode (LED) photolithography. The DNA chip platform contains 24 independent reaction sites, which allows for the testing of a corresponding amount of patients' samples in hospital. An array of commercial UV LEDs and lens systems was combined with a microfluidic flow system to provide patterning of 24 individual reaction sites, each with 64 independent probes. Using the LED array instead of conventional laser exposure systems or micro-mirror systems significantly reduces the cost of equipment. The microfluidic system together with microfluidic flow cells drastically reduces the amount of used reagents, which is important due to the high cost of commercial reagents. The DNA synthesis efficiency was verified by fluorescence labeling and conventional hybridization.

Illumination-parameter adjustable and illumination-distribution visible LED helmet for low-level light therapy on brain injury

NASA Astrophysics Data System (ADS)

Wang, Pengbo; Gao, Yuan; Chen, Xiao; Li, Ting

2016-03-01

Low-level light therapy (LLLT) has been clinically applied. Recently, more and more cases are reported with positive therapeutic effect by using transcranial light emitting diodes (LEDs) illumination. Here, we developed a LLLT helmet for treating brain injuries based on LED arrays. We designed the LED arrays in circle shape and assembled them in multilayered 3D printed helmet with water-cooling module. The LED arrays can be adjust to touch the head of subjects. A control circuit was developed to drive and control the illumination of the LLLT helmet. The software portion provides the control of on and off of each LED arrays, the setup of illumination parameters, and 3D distribution of LLLT light dose in human subject according to the illumination setups. This LLLT light dose distribution was computed by a Monte Carlo model for voxelized media and the Visible Chinese Human head dataset and displayed in 3D view at the background of head anatomical structure. The performance of the whole system was fully tested. One stroke patient was recruited in the preliminary LLLT experiment and the following neuropsychological testing showed obvious improvement in memory and executive functioning. This clinical case suggested the potential of this Illumination-parameter adjustable and illuminationdistribution visible LED helmet as a reliable, noninvasive, and effective tool in treating brain injuries.

Efficient resource allocation scheme for visible-light communication system

NASA Astrophysics Data System (ADS)

Kim, Woo-Chan; Bae, Chi-Sung; Cho, Dong-Ho; Shin, Hong-Seok; Jung, D. K.; Oh, Y. J.

2009-01-01

A visible-light communication utilizing LED has many advantagies such as visibility of information, high SNR (Signal to Noise Ratio), low installation cost, usage of existing illuminators, and high security. Furthermore, exponentially increasing needs and quality of LED have helped the development of visible-light communication. The visibility is the most attractive property in visible-light communication system, but it is difficult to ensure visibility and transmission efficiency simultaneously during initial access because of the small amount of initial access process signals. In this paper, we propose an efficient resource allocation scheme at initial access for ensuring visibility with high resource utilization rate and low data transmission failure rate. The performance has been evaluated through the numerical analysis and simulation results.

The quantitative models for broiler chicken response to monochromatic, combined, and mixed light-emitting diode light: A meta-analysis.

PubMed

Yang, Yefeng; Pan, Chenhao; Zhong, Renhai; Pan, Jinming

2018-06-01

Although many experiments have been conducted to clarify the response of broiler chickens to light-emitting diode (LED) light, those published results do not provide a solid scientific basis for quantifying the response of broiler chickens. This study used a meta-analysis to establish light spectral models of broiler chickens. The results indicated that 455 to 495 nm blue LED light produced the greatest positive response in body weight by 10.66% (BW; P < 0.001) and 515 to 560 nm green LED light increased BW by 6.27% (P < 0.001) when compared with white light. Regression showed that the wavelength (455 to 660 nm) was negatively related to BW change of birds, with a decrease of about 4.9% BW for each 100 nm increase in wavelength (P = 0.002). Further analysis suggested that a combination of the two beneficial light sources caused a synergistic effect. BW was further increased in birds transferred either from green LED light to blue LED light (17.23%; P < 0.001) or from blue LED light to green LED light (17.52%; P < 0.001). Moreover, birds raised with a mixture of green and blue LED light showed a greater BW promotion (10.66%; P < 0.001) than those raised with green LED light (6.27%). A subgroup analysis indicated that BW response to monochromatic LED light was significant regardless of the genetic strain, sex, control light sources, light intensity and regime of LED light, environmental temperature, and dietary ME and CP (P > 0.05). However, there was an interaction between the FCR response to monochromatic LED light with those covariant factors (P < 0.05). Additionally, green and yellow LED light played a role in affecting the meat color, quality, and nutrition of broiler chickens. The results indicate that the optimal ratio of green × blue of mixed LED light or shift to green-blue of combined LED light may produce the optimized production performance, whereas the optimal ratio of green/yellow of mixed or combined LED light may result in the optimized meat quality.

System and Method for Automated Rendezvous, Docking and Capture of Autonomous Underwater Vehicles

NASA Technical Reports Server (NTRS)

Clark, Evan (Inventor); Richmond, Kristof (Inventor); Paulus, Jeremy (Inventor); Kimball, Peter (Inventor); Scully, Mark (Inventor); Kapit, Jason (Inventor); Stone, William C. (Inventor)

2018-01-01

A system for automated rendezvous, docking, and capture of autonomous underwater vehicles at the conclusion of a mission comprising of comprised of a docking rod having lighted, pulsating (in both frequency and light intensity) series of LED light strips thereon, with the LEDs at a known spacing, and the autonomous underwater vehicle specially designed to detect and capture the docking rod and then be lifted structurally by a spherical end strop about which the vehicle can be pivoted and hoisted up (e.g., onto a ship). The method of recovery allows for very routine and reliable automated recovery of an unmanned underwater asset.

Fluorescence image excited by a scanning UV-LED light

NASA Astrophysics Data System (ADS)

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

2013-03-01

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

Light box for investigation of characteristics of optoelectronics detectors

NASA Astrophysics Data System (ADS)

Szreder, Agnieszka; Mazikowski, Adam

2017-09-01

In this paper, a light box for investigation of characteristics of optoelectronic detectors is described. The light box consists of an illumination device, an optical power sensor and a mechanical enclosure. The illumination device is based on four types of high-power light emitting diodes (LED): white light, red, green and blue. The illumination level can be varied for each LED independently by the driver and is measured by optical power sensor. The mechanical enclosure provides stable mounting points for the illumination device, sensor and the examined detector and protects the system from external light, which would otherwise strongly influence the measurement results. Uniformity of illumination distribution provided by the light box for all colors is good, making the measurement results less dependent on the position of the examined detector. The response of optoelectronic detectors can be investigated using the developed light box for each LED separately or for any combination of up to four LED types. As the red, green and blue LEDs are rather narrow bandwidth sources, spectral response of different detectors can be examined for these wavelength ranges. The described light box can be used for different applications. Its primary use is in a student laboratory setup for investigation of characteristics of optoelectronic detectors. Moreover, it can also be used in various colorimetric or photographic applications. Finally, it will be used as a part of demonstrations from the fields of vision and color, performed during science fairs and outreach activities increasing awareness of optics and photonics.

Economic analysis of greenhouse lighting: light emitting diodes vs. high intensity discharge fixtures.

PubMed

Nelson, Jacob A; Bugbee, Bruce

2014-01-01

Lighting technologies for plant growth are improving rapidly, providing numerous options for supplemental lighting in greenhouses. Here we report the photosynthetic (400-700 nm) photon efficiency and photon distribution pattern of two double-ended HPS fixtures, five mogul-base HPS fixtures, ten LED fixtures, three ceramic metal halide fixtures, and two fluorescent fixtures. The two most efficient LED and the two most efficient double-ended HPS fixtures had nearly identical efficiencies at 1.66 to 1.70 micromoles per joule. These four fixtures represent a dramatic improvement over the 1.02 micromoles per joule efficiency of the mogul-base HPS fixtures that are in common use. The best ceramic metal halide and fluorescent fixtures had efficiencies of 1.46 and 0.95 micromoles per joule, respectively. We also calculated the initial capital cost of fixtures per photon delivered and determined that LED fixtures cost five to ten times more than HPS fixtures. The five-year electric plus fixture cost per mole of photons is thus 2.3 times higher for LED fixtures, due to high capital costs. Compared to electric costs, our analysis indicates that the long-term maintenance costs are small for both technologies. If widely spaced benches are a necessary part of a production system, the unique ability of LED fixtures to efficiently focus photons on specific areas can be used to improve the photon capture by plant canopies. Our analysis demonstrates, however, that the cost per photon delivered is higher in these systems, regardless of fixture category. The lowest lighting system costs are realized when an efficient fixture is coupled with effective canopy photon capture.

Light intensity and quality from sole-source light-emitting diodes impact growth, morphology, and nutrient content of Brassica microgreens

USDA-ARS?s Scientific Manuscript database

Multi-layer vertical production systems using sole-source (SS) lighting can be used for microgreen production; however, traditional SS lighting can consume large amounts of electrical energy. Light-emitting diodes (LEDs) offer many advantages over conventional light sources including: high photoelec...

The study of LED light source illumination conditions for ideal algae cultivation

NASA Astrophysics Data System (ADS)

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.

Supplemental Upward Lighting from Underneath to Obtain Higher Marketable Lettuce (Lactuca sativa) Leaf Fresh Weight by Retarding Senescence of Outer Leaves.

PubMed

Zhang, Geng; Shen, Shanqi; Takagaki, Michiko; Kozai, Toyoki; Yamori, Wataru

2015-01-01

Recently, the so-called "plant factory with artificial lighting" (PFAL) approach has been developed to provide safe and steady food production. Although PFALs can produce high-yielding and high-quality plants, the high plant density in these systems accelerates leaf senescence in the bottom (or outer) leaves owing to shading by the upper (or inner) leaves and by neighboring plants. This decreases yield and increases labor costs for trimming. Thus, the establishment of cultivation methods to retard senescence of outer leaves is an important research goal to improve PFAL yield and profitability. In the present study, we developed an LED lighting apparatus that would optimize light conditions for PFAL cultivation of a leafy vegetable. Lettuce (Lactuca sativa L.) was hydroponically grown under white, red, or blue LEDs, with light provided from above (downward), with or without supplemental upward lighting from underneath the plant. White LEDs proved more appropriate for lettuce growth than red or blue LEDs, and the supplemental lighting retarded the senescence of outer leaves and decreased waste (i.e., dead or low-quality senescent leaves), leading to an improvement of the marketable leaf fresh weight.

Spectral quality affects disease development of three pathogens on hydroponically grown plants.

PubMed

Schuerger, A C; Brown, C S

1997-02-01

Plants were grown under light-emitting diode (LED) arrays with various spectra to determine the effects of light quality on the development of diseases caused by tomato mosaic virus (ToMV) on pepper (Capsicum annuum L.), powdery mildew [Sphaerotheca fuliginea (Schlectend:Fr.) Pollaci] on cucumber (Cucumis sativus L.), and bacterial wilt (Pseudomonas solanacearum Smith) on tomato (Lycopersicon esculentum Mill.). One LED (660) array supplied 99% red light at 660 nm (25 nm bandwidth at half-peak height) and 1% far-red light between 700 to 800 nm. A second LED (660/735) array supplied 83% red light at 660 nm and 17% far-red light at 735 nm (25 nm bandwidth at half-peak height). A third LED (660/BF) array supplied 98% red light at 660 nm, 1% blue light (BF) between 350 to 550 nm, and 1% far-red light between 700 to 800 nm. Control plants were grown under broad-spectrum metal halide (MH) lamps. Plants were grown at a mean photon flux (300 to 800 nm) of 330 micromoles m-2 s-1 under a 12-h day/night photoperiod. Spectral quality affected each pathosystem differently. In the ToMV/pepper pathosystem, disease symptoms developed slower and were less severe in plants grown under light sources that contained blue and UV-A wavelengths (MH and 660/BF treatments) compared to plants grown under light sources that lacked blue and UV-A wavelengths (660 and 660/735 LED arrays). In contrast, the number of colonies per leaf was highest and the mean colony diameters of S. fuliginea on cucumber plants were largest on leaves grown under the MH lamp (highest amount of blue and UV-A light) and least on leaves grown under the 660 LED array (no blue or UV-A light). The addition of far-red irradiation to the primary light source in the 660/735 LED array increased the colony counts per leaf in the S. fuliginea/cucumber pathosystem compared to the red-only (660) LED array. In the P. solanacearum/tomato pathosystem, disease symptoms were less severe in plants grown under the 660 LED array, but the effects of spectral quality on disease development when other wavelengths were included in the light source (MH-, 660/BF-, and 660/735-grown plants) were equivocal. These results demonstrate that spectral quality may be useful as a component of an integrated pest management program for future space-based controlled ecological life support systems.

Spectral quality affects disease development of three pathogens on hydroponically grown plants

NASA Technical Reports Server (NTRS)

Schuerger, A. C.; Brown, C. S.; Sager, J. C. (Principal Investigator)

1997-01-01

Plants were grown under light-emitting diode (LED) arrays with various spectra to determine the effects of light quality on the development of diseases caused by tomato mosaic virus (ToMV) on pepper (Capsicum annuum L.), powdery mildew [Sphaerotheca fuliginea (Schlectend:Fr.) Pollaci] on cucumber (Cucumis sativus L.), and bacterial wilt (Pseudomonas solanacearum Smith) on tomato (Lycopersicon esculentum Mill.). One LED (660) array supplied 99% red light at 660 nm (25 nm bandwidth at half-peak height) and 1% far-red light between 700 to 800 nm. A second LED (660/735) array supplied 83% red light at 660 nm and 17% far-red light at 735 nm (25 nm bandwidth at half-peak height). A third LED (660/BF) array supplied 98% red light at 660 nm, 1% blue light (BF) between 350 to 550 nm, and 1% far-red light between 700 to 800 nm. Control plants were grown under broad-spectrum metal halide (MH) lamps. Plants were grown at a mean photon flux (300 to 800 nm) of 330 micromoles m-2 s-1 under a 12-h day/night photoperiod. Spectral quality affected each pathosystem differently. In the ToMV/pepper pathosystem, disease symptoms developed slower and were less severe in plants grown under light sources that contained blue and UV-A wavelengths (MH and 660/BF treatments) compared to plants grown under light sources that lacked blue and UV-A wavelengths (660 and 660/735 LED arrays). In contrast, the number of colonies per leaf was highest and the mean colony diameters of S. fuliginea on cucumber plants were largest on leaves grown under the MH lamp (highest amount of blue and UV-A light) and least on leaves grown under the 660 LED array (no blue or UV-A light). The addition of far-red irradiation to the primary light source in the 660/735 LED array increased the colony counts per leaf in the S. fuliginea/cucumber pathosystem compared to the red-only (660) LED array. In the P. solanacearum/tomato pathosystem, disease symptoms were less severe in plants grown under the 660 LED array, but the effects of spectral quality on disease development when other wavelengths were included in the light source (MH-, 660/BF-, and 660/735-grown plants) were equivocal. These results demonstrate that spectral quality may be useful as a component of an integrated pest management program for future space-based controlled ecological life support systems.

Growth and photomorphogenesis of pepper plants under red light-emitting diodes with supplemental blue or far-red lighting

NASA Technical Reports Server (NTRS)

Brown, C. S.; Schuerger, A. C.; Sager, J. C.

1995-01-01

Light-emitting diodes (LEDs) are a potential irradiation source for intensive plant culture systems and photobiological research. They have small size, low mass, a long functional life, and narrow spectral output. In this study, we measured the growth and dry matter partitioning of 'Hungarian Wax' pepper (Capsicum annuum L.) plants grown under red LEDs compared with similar plants grown under red LEDs with supplemental blue or far-red radiation or under broad spectrum metal halide (MH) lamps. Additionally, we describe the thermal and spectral characteristics of these sources. The LEDs used in this study had a narrow bandwidth at half peak height (25 nm) and a focused maximum spectral output at 660 nm for the red and 735 nm for the far-red. Near infrared radiation (800 to 3000 nm) was below detection and thermal infrared radiation (3000 to 50,000 nm) was lower in the LEDs compared to the MH source. Although the red to far-red ratio varied considerably, the calculated phytochrome photostationary state (phi) was only slightly different between the radiation sources. Plant biomass was reduced when peppers were grown under red LEDs in the absence of blue wavelengths compared to plants grown under supplemental blue fluorescent lamps or MH lamps. The addition of far-red radiation resulted in taller plants with greater stem mass than red LEDs alone. There were fewer leaves under red or red plus far-red radiation than with lamps producing blue wavelengths. These results indicate that red LEDs may be suitable, in proper combination with other wavelengths of light, for the culture of plants in tightly controlled environments such as space-based plant culture systems.

Innovative Patient Room Lighting System with Integrated Spectrally Adaptive Control

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maniccia, Dorene A.; Rizzo, Patricia; Kim, James

In December of 2013, the U.S. Department of Energy’s SSL R&D Program released a Funding Opportunity Announcement (FOA), that for the first time, contained opportunities for comprehensive application-specific system development. The FOA included opportunities for two applications, one of which was a Patient Room. Philips Lighting Research North America, submitted a proposal for the Patient Room application, and was selected for the complete project award. The award amount was for $497,127, with a Philips Research co-funding commitment 165,709 dollars. The total project value was 662,836 dollars. This project sought to redefine lighting for the patient room application. The goal wasmore » to deliver an innovative LED patient suite (patient room and bathroom) lighting system solution that was 40% more energy-efficient than traditional fluorescent incumbent technologies, and would meet all the visual and non-visual needs of patients, caregivers and visitors, and improve the patient experience. State-of-the-art multichannel LED platforms and control technologies that would provide spectral tuning and become part of an intelligent, connected lighting system drove the solution. The project was scoped into four main task areas that included a) System Concept Creation, b) Identification of the Luminaire Portfolio, c) Development of the Connected Lighting Infrastructure, and d) System Performance Validation. Each of the four main tasks were completed and validated extensively over the course the 2 ½ year project. The system concept was created by first developing a lighting design that demonstrated best practices for patient room lighting – illuminance and uniformity for task performance, reduced glare, and convenient controls, in addition to giving patients control over the lighting in their environment. A framework was defined to deliver circadian support via software behaviors. Through that process luminaires were identified from the Philips portfolio that were adaptable – by their form, dimensions, and optical materials – to mix multicolor LED platforms uniformly and deliver target design lumen levels. The Blue Sky luminaire was selected for the patient bed area to give the illusion of skylight while providing white light on the patient bed. Luminaires used existing 2-channel tunable white LED boards, and newly developed 4-channel LED boards. Red-Orange, Blue, Green, and Blue-shifted Yellow LED chips were selected based on spectral characteristics and their ability to produce high quality white light. 4-channel Power over Ethernet (PoE) drivers were developed and firmware written so they would communicate with both 2- and 4-channel boards. These components formed the backbone of the connected lighting infrastructure. Software, flexible and nuanced in its complexity, was written to set behaviors for myriad lighting scenes in the room throughout the 24 hour day – and all could be overridden by manual controls. This included a dynamic tunable white program, three color changing automatic programs that simulated degrees of sunrise to sunset palettes, and an amber night lighting system that offered visual cues for postural stability to minimize the risk of falls. All programs were carefully designed to provide visual comfort for all occupants, support critical task performance for staff, and to support the patient’s 24hr rhythms. A full scale mockup room was constructed in the Philips Cambridge Lab. The lighting system was installed, tested and functionality demonstrated to ensure smooth operation of system components – luminaires, drivers, PoE switches, wall controls, patient remote, and daylight and occupancy sensors. How did the system perform? It met visual criteria, confirmed by calculations, simulations and measurements in the field. It met non-visual criteria, confirmed by setting circadian stimulus (CS) targets and performing calculations using the calculator developed by the Lighting Research Center. Finally, human factors validation studies were conducted to gain insight from real end users in the healthcare profession; surveys were administered, data analyzed, and audio comments captured. The general consensus was positive, with requests to pilot the system in their hospitals. The importance of the research completed under this grant is that it allowed the exploration and development of a unique lighting system, one that would deliver a blend of visual and non-visual criteria in patient room design for today’s healthcare environment. The research investigated the area of multichannel LED technology, multichannel Power over Ethernet (PoE) drivers and their integration with automatic and manual controls as a system – uncovering and meeting challenges along the way. It married visual needs of patients and staff with support for 24 hour rhythms, placing value on the wellbeing of the patient – while successfully saving energy over incumbent technologies. Indications are that the market is ready and willing to invest – multiple healthcare facilities are in line to pilot this system, recognizing its value beyond energy to patient and staff well-being. Its value to the public can best be expressed by a patient support coordinator who, after spending several hours in the room being immersed in the lighting, analyzing all its features, commented: “This re-writes lighting for healthcare”.« less

Green-light supplementation for enhanced lettuce growth under red- and blue-light-emitting diodes

NASA Technical Reports Server (NTRS)

Kim, Hyeon-Hye; Goins, Gregory D.; Wheeler, Raymond M.; Sager, John C.

2004-01-01

Plants will be an important component of future long-term space missions. Lighting systems for growing plants will need to be lightweight, reliable, and durable, and light-emitting diodes (LEDs) have these characteristics. Previous studies demonstrated that the combination of red and blue light was an effective light source for several crops. Yet the appearance of plants under red and blue lighting is purplish gray making visual assessment of any problems difficult. The addition of green light would make the plant leave appear green and normal similar to a natural setting under white light and may also offer a psychological benefit to the crew. Green supplemental lighting could also offer benefits, since green light can better penetrate the plant canopy and potentially increase plant growth by increasing photosynthesis from the leaves in the lower canopy. In this study, four light sources were tested: 1) red and blue LEDs (RB), 2) red and blue LEDs with green fluorescent lamps (RGB), 3) green fluorescent lamps (GF), and 4) cool-white fluorescent lamps (CWF), that provided 0%, 24%, 86%, and 51% of the total PPF in the green region of the spectrum, respectively. The addition of 24% green light (500 to 600 nm) to red and blue LEDs (RGB treatment) enhanced plant growth. The RGB treatment plants produced more biomass than the plants grown under the cool-white fluorescent lamps (CWF treatment), a commonly tested light source used as a broad-spectrum control.

Temperature issues with white laser diodes, calculation and approach for new packages

NASA Astrophysics Data System (ADS)

Lachmayer, Roland; Kloppenburg, Gerolf; Stephan, Serge

2015-01-01

Bright white light sources are of significant importance for automotive front lighting systems. Today's upper class systems mainly use HID or LED light sources. As a further step laser diode based systems offer a high luminance, efficiency and allow the realization of new dynamic and adaptive light functions and styling concepts. The use of white laser diode systems in automotive applications is still limited to laboratories and prototypes even though announcements of laser based front lighting systems have been made. But the environment conditions for vehicles and other industry sectors differ from laboratory conditions. Therefor a model of the system's thermal behavior is set up. The power loss of a laser diode is transported as thermal flux from the junction layer to the diode's case and on to the environment. Therefor its optical power is limited by the maximum junction temperature (for blue diodes typically 125 - 150 °C), the environment temperature and the diode's packaging with its thermal resistances. In a car's headlamp the environment temperature can reach up to 80 °C. While the difference between allowed case temperature and environment temperature is getting small or negative the relevant heat flux also becomes small or negative. In early stages of LED development similar challenges had to be solved. Adapting LED packages to the conditions in a vehicle environment lead to today's efficient and bright headlights. In this paper the need to transfer these results to laser diodes is shown by calculating the diodes lifetimes based on the presented model.

Advanced Solid State Lighting for AES Deep Space Hab Project

NASA Technical Reports Server (NTRS)

Holbert, Eirik

2015-01-01

The advanced Solid State Lighting (SSL) assemblies augmented 2nd generation modules under development for the Advanced Exploration Systems Deep Space Habitat in using color therapy to synchronize crew circadian rhythms. Current RGB LED technology does not produce sufficient brightness to adequately address general lighting in addition to color therapy. The intent is to address both through a mix of white and RGB LEDs designing for fully addressable alertness/relaxation levels as well as more dramatic circadian shifts.

Monolithic Flexible Vertical GaN Light-Emitting Diodes for a Transparent Wireless Brain Optical Stimulator.

PubMed

Lee, Han Eol; Choi, JeHyuk; Lee, Seung Hyun; Jeong, Minju; Shin, Jung Ho; Joe, Daniel J; Kim, DoHyun; Kim, Chang Wan; Park, Jung Hwan; Lee, Jae Hee; Kim, Daesoo; Shin, Chan-Soo; Lee, Keon Jae

2018-05-18

Flexible inorganic-based micro light-emitting diodes (µLEDs) are emerging as a significant technology for flexible displays, which is an important area for bilateral visual communication in the upcoming Internet of Things era. Conventional flexible lateral µLEDs have been investigated by several researchers, but still have significant issues of power consumption, thermal stability, lifetime, and light-extraction efficiency on plastics. Here, high-performance flexible vertical GaN light-emitting diodes (LEDs) are demonstrated by silver nanowire networks and monolithic fabrication. Transparent, ultrathin GaN LED arrays adhere to a human fingernail and stably glow without any mechanical deformation. Experimental studies provide outstanding characteristics of the flexible vertical μLEDs (f-VLEDs) with high optical power (30 mW mm -2 ), long lifetime (≈12 years), and good thermal/mechanical stability (100 000 bending/unbending cycles). The wireless light-emitting system on the human skin is successfully realized by transferring the electrical power f-VLED. Finally, the high-density GaN f-VLED arrays are inserted onto a living mouse cortex and operated without significant histological damage of brain. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Real-time time-division color electroholography using a single GPU and a USB module for synchronizing reference light.

PubMed

Araki, Hiromitsu; Takada, Naoki; Niwase, Hiroaki; Ikawa, Shohei; Fujiwara, Masato; Nakayama, Hirotaka; Kakue, Takashi; Shimobaba, Tomoyoshi; Ito, Tomoyoshi

2015-12-01

We propose real-time time-division color electroholography using a single graphics processing unit (GPU) and a simple synchronization system of reference light. To facilitate real-time time-division color electroholography, we developed a light emitting diode (LED) controller with a universal serial bus (USB) module and the drive circuit for reference light. A one-chip RGB LED connected to a personal computer via an LED controller was used as the reference light. A single GPU calculates three computer-generated holograms (CGHs) suitable for red, green, and blue colors in each frame of a three-dimensional (3D) movie. After CGH calculation using a single GPU, the CPU can synchronize the CGH display with the color switching of the one-chip RGB LED via the LED controller. Consequently, we succeeded in real-time time-division color electroholography for a 3D object consisting of around 1000 points per color when an NVIDIA GeForce GTX TITAN was used as the GPU. Furthermore, we implemented the proposed method in various GPUs. The experimental results showed that the proposed method was effective for various GPUs.

Accurate chromatic control and color rendering optimization in LED lighting systems using junction temperature feedback

NASA Astrophysics Data System (ADS)

Sisto, Marco Michele; Gauvin, Jonny

2014-09-01

Accurate color control of LED lighting systems is a challenging task: noticeable chromaticity shifts are commonly observed in mixed-color and phosphor converted LEDs due to intensity dimming. Furthermore, the emitted color varies with the LED temperature. We present a novel color control method for tri-chromatic and tetra-chromatic LEDs, which enable to set and maintain the LED emission at a target color, or combination of correlated color temperature (CCT) and intensity. The LED color point is maintained over variations in the LED junctions' temperatures and intensity dimming levels. The method does not require color feedback sensors, so to minimize system complexity and cost, but relies on estimation of the LED junctions' temperatures from the junction voltages. If operated with tetra-chromatic LEDs, the method allows meeting an additional optimization criterion: for example, the maximization of a color rendering metric like the Color Rendering Index (CRI) or the Color Quality Scale (CQS), thus providing a high quality and clarity of colors on the surface illuminated by the LED. We demonstrate the control of a RGBW LED at target D65 white point with CIELAB color difference metric triangle;a,bE < 1 for simultaneous variations of flux from approximately 30 lm to 100 lm and LED heat sink temperature from 25°C to 58°C. In the same conditions, we demonstrate a CCT error <1%. Furthermore, the method allows varying the LED CCT from 5500K to 8000K while maintaining luminance within 1% of target. Further work is ongoing to evaluate the stability of the method over LED aging.

An LED light source and novel fluorophore combinations improve fluorescence laparoscopic detection of metastatic pancreatic cancer in orthotopic mouse models.

PubMed

Metildi, Cristina A; Kaushal, Sharmeela; Lee, Claudia; Hardamon, Chanae R; Snyder, Cynthia S; Luiken, George A; Talamini, Mark A; Hoffman, Robert M; Bouvet, Michael

2012-06-01

The aim of this study was to improve fluorescence laparoscopy of pancreatic cancer in an orthotopic mouse model with the use of a light-emitting diode (LED) light source and optimal fluorophore combinations. Human pancreatic cancer models were established with fluorescent FG-RFP, MiaPaca2-GFP, BxPC-3-RFP, and BxPC-3 cancer cells implanted in 6-week-old female athymic mice. Two weeks postimplantation, diagnostic laparoscopy was performed with a Stryker L9000 LED light source or a Stryker X8000 xenon light source 24 hours after tail-vein injection of CEA antibodies conjugated with Alexa 488 or Alexa 555. Cancer lesions were detected and localized under each light mode. Intravital images were also obtained with the OV-100 Olympus and Maestro CRI Small Animal Imaging Systems, serving as a positive control. Tumors were collected for histologic analysis. Fluorescence laparoscopy with a 495-nm emission filter and an LED light source enabled real-time visualization of the fluorescence-labeled tumor deposits in the peritoneal cavity. The simultaneous use of different fluorophores (Alexa 488 and Alexa 555), conjugated to antibodies, brightened the fluorescence signal, enhancing detection of submillimeter lesions without compromising background illumination. Adjustments to the LED light source permitted simultaneous detection of tumor lesions of different fluorescent colors and surrounding structures with minimal autofluorescence. Using an LED light source with adjustments to the red, blue, and green wavelengths, it is possible to simultaneously identify tumor metastases expressing fluorescent proteins of different wavelengths, which greatly enhanced the signal without compromising background illumination. Development of this fluorescence laparoscopy technology for clinical use can improve staging and resection of pancreatic cancer. Copyright © 2012 American College of Surgeons. Published by Elsevier Inc. All rights reserved.

Modularized and water-cooled photo-catalyst cleaning devices for aquaponics based on ultraviolet light-emitting diodes

NASA Astrophysics Data System (ADS)

Yang, Henglong; Lung, Louis; Wei, Yu-Chien; Huang, Yi-Bo; Chen, Zi-Yu; Chou, Yu-Yang; Lin, Anne-Chin

2017-08-01

The feasibility of applying ultraviolet light-emitting diodes (UV-LED's) as triggering sources of photo-catalyst based on titanium dioxide (TiO2) nano-coating specifically for water-cleaning process in an aquaponics system was designed and proposed. The aquaponics system is a modern farming system to integrate aquaculture and hydroponics into a single system to establish an environmental-friendly and lower-cost method for farming fish and vegetable all together in urban area. Water treatment in an aquaponics system is crucial to avoid mutual contamination. we proposed a modularized watercleaning device composed of all commercially available components and parts to eliminate organic contaminants by using UV-LED's for TiO2 photo-catalyst reaction. This water-cleaning module consisted of two coaxial hollowed cylindrical pipes can be submerged completely in water for water treatment and cooling UV-LED's. The temperature of the UV-LED after proper thermal management can be reduced about 16% to maintain the optimal operation condition. Our preliminary experimental result by using Methylene Blue solution to simulate organic contaminants indicated that TiO2 photo-catalyst triggered by UV-LED's can effectively decompose organic compound and decolor Methylene Blue solution.

Experimentally comparing the attractiveness of domestic lights to insects: Do LEDs attract fewer insects than conventional light types?

PubMed

Wakefield, Andrew; Broyles, Moth; Stone, Emma L; Jones, Gareth; Harris, Stephen

2016-11-01

LED lighting is predicted to constitute 70% of the outdoor and residential lighting markets by 2020. While the use of LEDs promotes energy and cost savings relative to traditional lighting technologies, little is known about the effects these broad-spectrum "white" lights will have on wildlife, human health, animal welfare, and disease transmission. We conducted field experiments to compare the relative attractiveness of four commercially available "domestic" lights, one traditional (tungsten filament) and three modern (compact fluorescent, "cool-white" LED and "warm-white" LED), to aerial insects, particularly Diptera. We found that LEDs attracted significantly fewer insects than other light sources, but found no significant difference in attraction between the "cool-" and "warm-white" LEDs. Fewer flies were attracted to LEDs than alternate light sources, including fewer Culicoides midges (Diptera: Ceratopogonidae). Use of LEDs has the potential to mitigate disturbances to wildlife and occurrences of insect-borne diseases relative to competing lighting technologies. However, we discuss the risks associated with broad-spectrum lighting and net increases in lighting resulting from reduced costs of LED technology.

Retinal endoilluminator toxicity of xenon and light-emitting diode (LED) light source: rabbit model.

PubMed

Aydin, Bahri; Dinç, Erdem; Yilmaz, S Necat; Altiparmak, U Emrah; Yülek, Fatma; Ertekin, Sevda; Yilmaz, Mustafa; Yakın, Mehmet

2014-09-01

This study evaluates retinal toxicity due to endoillumination with the light-emitting diode (LED) light source in comparison to endoillumination with xenon light source. Twenty-five eyes of 14 New Zealand pigmented rabbits were used in the study. The LED light (Omesis Medical Systems, Turkey) group was composed of 7 right eyes, while the other 7 right eyes constituted the xenon group (420 nm filter, 357mW/cm(2)) (Bright Star; DORC, Zuidland, Netherlands). Eleven untreated left eyes composed the control group. Twenty gauge pars plana incision 1.5 mm behind the limbus was performed in the right eyes. Twenty gauge bullet type fiberoptic endoilluminator was inserted into the eye from the incision without any pars plana vitrectomy. Fiberoptic endoilluminator was placed in such a way that it was directed toward visual streak of the rabbit retina with a 5 mm distance to retinal surface. Endoillumination was then applied for 20 min with a maximum light intensity for LED and xenon light. In left control eyes, no surgical procedure and no endoillumination were performed. One week after the endoillumination procedure, both eyes of the rabbits were enucleated following electroretinography. Sections stained with hematoxylin and eosin to evaluate morphologic changes. Retina tissues were assessed by active caspase-3 staining. There was no difference in the shape of the waveforms recorded in the eyes endoilluminated with LED light and xenon light sources compared to control eyes both before and after endoillumination application (p > 0.05). Microscopic evaluation of the retinas with hematoxylin and eosin staining demonstrated that all study groups have normal histologic properties similar to control group. No apoptosis positive cells were found within all sections in all groups. When the LED light source is used with maximum power and limited duration for endoillumination in rabbit eyes it does not produce phototoxic effects that may be detectable by electrophysiology and histology similar to xenon light.

The extended Beer-Lambert theory for ray tracing modeling of LED chip-scaled packaging application with multiple luminescence materials

NASA Astrophysics Data System (ADS)

Yuan, Cadmus C. A.

2015-12-01

Optical ray tracing modeling applied Beer-Lambert method in the single luminescence material system to model the white light pattern from blue LED light source. This paper extends such algorithm to a mixed multiple luminescence material system by introducing the equivalent excitation and emission spectrum of individual luminescence materials. The quantum efficiency numbers of individual material and self-absorption of the multiple luminescence material system are considered as well. By this combination, researchers are able to model the luminescence characteristics of LED chip-scaled packaging (CSP), which provides simple process steps and the freedom of the luminescence material geometrical dimension. The method will be first validated by the experimental results. Afterward, a further parametric investigation has been then conducted.

Design of compact freeform lens for application specific Light-Emitting Diode packaging.

PubMed

Wang, Kai; Chen, Fei; Liu, Zongyuan; Luo, Xiaobing; Liu, Sheng

2010-01-18

Application specific LED packaging (ASLP) is an emerging technology for high performance LED lighting. We introduced a practical design method of compact freeform lens for extended sources used in ASLP. A new ASLP for road lighting was successfully obtained by integrating a polycarbonate compact freeform lens of small form factor with traditional LED packaging. Optical performance of the ASLP was investigated by both numerical simulation based on Monte Carlo ray tracing method and experiments. Results demonstrated that, comparing with traditional LED module integrated with secondary optics, the ASLP had advantages of much smaller size in volume (approximately 1/8), higher system lumen efficiency (approximately 8.1%), lower cost and more convenience for customers to design and assembly, enabling possible much wider applications of LED for general road lighting. Tolerance analyses were also conducted. Installation errors of horizontal and vertical deviations had more effects on the shape and uniformity of radiation pattern compared with rotational deviation. The tolerances of horizontal, vertical and rotational deviations of this lens were 0.11 mm, 0.14 mm and 2.4 degrees respectively, which were acceptable in engineering.

Colour gamut enhancement with remote light conversion mechanism

NASA Astrophysics Data System (ADS)

Koseoglu, D.; Sezer, Y. S.; Karsli, K.

2018-01-01

The backlight unit spectrum of liquid crystal displays (LCD) directly affects the colour gamut. With the invention of GaN based blue light emitting diodes (LED), phosphors and quantum dots (QD) have gained considerable scientific interest due to their broad range of applications especially in lighting and display technologies. These phosphors and QDs are used to convert the blue light of the LEDs into white in general lighting. On the other hand, in display systems, they are used to generate red and green bands. There are different application methods such as on-chip and remote configurations. In this study, we concentrate on remote phosphor and QD backlight configurations where the light conversion is done away from the chips. In our display designs, we used GaN based blue LED lateral chips as an excitation source, on the other hand, light conversion layers were placed in backlight units as a thin film for the emission of green and red bands. The mixing ratios of these composite layers were arranged to match the emission spectrum of the blue LEDs and the light conversion layer to the colour filters of the LCD, so that the green, blue, and red bands efficiently widens the colour space. The results were also compared with the on-chip phosphor arrangements.

Technology of Wide Color Gamut Backlight with Light-Emitting Diode for Liquid Crystal Display Television

NASA Astrophysics Data System (ADS)

Kakinuma, Koichiro

2006-05-01

The development of light-emitting diode (LED) backlight a wide-color-gamut and mercury-free has become active in liquid crystal display (LCD) industry. Reports on the development of backlights, such as a direct illumination-type back-light and a guided light illumination-type LED backlight were published. The fabrication of an actual commercial product has been progressing under this active development. Sony Corporation launched an LED-backlit LCD television (TV) model, dubbed QUALIA 005, the world’s first home-use television featuring LED backlighting. This product offers a very wide color reproduction range, delivering a color gamut of 150% of that typically achieved by conventional televisions. In this paper, the background of the development of the LED backlight system “TriluminosTM” and the technologies used to realize the wide color gamut are discussed. The main issues to be solved for the commercialization were how to reduce the brightness/color non uniformity of the backlight and how to treat heat generation from the LED. The standardization of wide color space definition xvYCC and LED backlight LCD television combination is expected to result in a more vivid and correct color expression, and a forecast that extends to the market in the future.

A portable system for noninvasive assessment of advanced glycation end-products using skin fluorescence and reflectance spectrum

NASA Astrophysics Data System (ADS)

Wang, Y. K.; Zhu, L.; Zhang, L.; Zhang, G.; Liu, Y.; Wang, A.

2012-07-01

An optical system has been developed for noninvasive assessment of skin advanced glycation end-products (AGEs). The system comprises mainly a high-power ultraviolet light emitting diode (LED) as an excitation source, an LED array for the reflectance measurement, a trifurcated fiber-optic probe for light transmitting and receiving, and a compact spectrometer for light detecting. Both skin fluorescence of a subject and the reflectance spectrum of the same site can be obtained in a single measurement with the system. Demonstrative measurements with the system have been conducted. Results indicate that the measured reflectance spectrum can be used to compensate for the distortion of AGEs fluorescence, which is caused by skin absorption and scattering. The system is noninvasive, portable, easy to operate, and has potential applications for clinical diagnosis of AGE-related diseases, especially diabetes mellitus.

Mapping algorithm for freeform construction using non-ideal light sources

NASA Astrophysics Data System (ADS)

Li, Chen; Michaelis, D.; Schreiber, P.; Dick, L.; Bräuer, A.

2015-09-01

Using conventional mapping algorithms for the construction of illumination freeform optics' arbitrary target pattern can be obtained for idealized sources, e.g. collimated light or point sources. Each freeform surface element generates an image point at the target and the light intensity of an image point is corresponding to the area of the freeform surface element who generates the image point. For sources with a pronounced extension and ray divergence, e.g. an LED with a small source-freeform-distance, the image points are blurred and the blurred patterns might be different between different points. Besides, due to Fresnel losses and vignetting, the relationship between light intensity of image points and area of freeform surface elements becomes complicated. These individual light distributions of each freeform element are taken into account in a mapping algorithm. To this end the method of steepest decent procedures are used to adapt the mapping goal. A structured target pattern for a optics system with an ideal source is computed applying corresponding linear optimization matrices. Special weighting factor and smoothing factor are included in the procedures to achieve certain edge conditions and to ensure the manufacturability of the freefrom surface. The corresponding linear optimization matrices, which are the lighting distribution patterns of each of the freeform surface elements, are gained by conventional raytracing with a realistic source. Nontrivial source geometries, like LED-irregularities due to bonding or source fine structures, and a complex ray divergence behavior can be easily considered. Additionally, Fresnel losses, vignetting and even stray light are taken into account. After optimization iterations, with a realistic source, the initial mapping goal can be achieved by the optics system providing a structured target pattern with an ideal source. The algorithm is applied to several design examples. A few simple tasks are presented to discussed the ability and limitation of the this mothed. It is also presented that a homogeneous LED-illumination system design, in where, with a strongly tilted incident direction, a homogeneous distribution is achieved with a rather compact optics system and short working distance applying a relatively large LED source. It is shown that the lighting distribution patterns from the freeform surface elements can be significantly different from the others. The generation of a structured target pattern, applying weighting factor and smoothing factor, are discussed. Finally, freeform designs for much more complex sources like clusters of LED-sources are presented.

LED Device Illuminates New Path to Healing

NASA Technical Reports Server (NTRS)

2008-01-01

Among NASA s research goals is increased understanding of factors affecting plant growth, including the effects of microgravity. Impeding such studies, traditional light sources used to grow plants on Earth are difficult to adapt to space flight, as they require considerable amounts of power and produce relatively large amounts of heat. As such, an optimized experimental system requires much less energy and reduces temperature variance without negatively affecting plant growth results. Ronald W. Ignatius, founder and chairman of the board at Quantum Devices Inc. (QDI), of Barneveld, Wisconsin, proposed using light-emitting diodes (LEDs) as the photon source for plant growth experiments in space. This proposition was made at a meeting held by the Wisconsin Center for Space Automation and Robotics, a NASA-sponsored research center that facilitates the commercialization of robotics, automation, and other advanced technologies. The Wisconsin group teamed with QDI to determine whether an LED system could provide the necessary wavelengths and intensities for photosynthesis, and the resultant system proved successful. The center then produced the Astroculture3, a plant growth chamber that successfully incorporated this LED light source, which has now flown on several space shuttle missions. NASA subsequently identified another need that could be addressed with the use of LEDs: astronaut health. A central concern in astronaut health is maintaining healthy growth of cells, including preventing bone and muscle loss and boosting the body s ability to heal wounds all adversely affected by prolonged weightlessness. Thus, having determined that LEDs can be used to grow plants in space, NASA decided to investigate whether LEDs might be used for photobiomodulation therapy (PBMT).

Performance of light sources and radiation sensors under low gravity realized by parabolic airplane flights

NASA Astrophysics Data System (ADS)

Hirai, Hiroaki; Kitaya, Yoshiaki; Hirai, Takehiro

A fundamental study was conducted to establish an experimental system for space farming. Since to ensure optimal light for plant cultivation in space is of grave importance, this study examined the performance of light sources and radiation sensors under microgravity conditions created during the parabolic airplane flight. Three kinds of light sources, a halogen bulb, a fluorescent tube, and blue and red LEDs, and ten models of radiation sensors available in the market were used for the experiment. Surface temperature of the light sources, output signals from the radiation sensors, spectroscopic characteristics were measured at the gravity levels of 0.01, 1.0 and 1.8 G for 20 seconds each during parabolic airplane flights. As a result, the performance of the halogen lamp was affected the most by the gravity level among the three light sources. Under the microgravity conditions which do not raise heat convection, the temperature of the halogen lamp rose and the output of the radiation sensors increased. Spectral distributions of the halogen lamp indicated that peak wavelength appeared the highest at the level of 0.01G, which contributed to the increase in light intensity. In the case of red and blue LEDs, which are promising light sources in space farming, the temperature of both LED chips rose but irradiance from red LED increased and that from blue LED decreased under microgravity conditions due to the different thermal characteristics.

Plastic cup traps equipped with light-emitting diodes for monitoring adult Bemisia tabaci (Homoptera: Aleyrodidae).

PubMed

Chu, Chang-Chi; Jackson, Charles G; Alexander, Patrick J; Karut, Kamil; Henneberry, Thomas J

2003-06-01

Equipping the standard plastic cup trap, also known as the CC trap, with lime-green light-emitting diodes (LED-plastic cup trap) increased its efficacy for catching Bemisia tabaci by 100%. Few Eretmocerus eremicus Rose and Zolnerowich and Encarsia formosa Gahan were caught in LED-plastic cup traps. The LED-plastic cup traps are less expensive than yellow sticky card traps for monitoring adult whiteflies in greenhouse crop production systems and are more compatible with whitefly parasitoids releases for Bemisia nymph control.

Optimizing illumination in the greenhouse using a 3D model of tomato and a ray tracer

PubMed Central

de Visser, Pieter H. B.; Buck-Sorlin, Gerhard H.; van der Heijden, Gerie W. A. M.

2014-01-01

Reduction of energy use for assimilation lighting is one of the most urgent goals of current greenhouse horticulture in the Netherlands. In recent years numerous lighting systems have been tested in greenhouses, yet their efficiency has been very difficult to measure in practice. This simulation study evaluated a number of lighting strategies using a 3D light model for natural and artificial light in combination with a 3D model of tomato. The modeling platform GroIMP was used for the simulation study. The crop was represented by 3D virtual plants of tomato with fixed architecture. Detailed data on greenhouse architecture and lamp emission patterns of different light sources were incorporated in the model. A number of illumination strategies were modeled with the calibrated model. Results were compared to the standard configuration. Moreover, adaptation of leaf angles was incorporated for testing their effect on light use efficiency (LUE). A Farquhar photosynthesis model was used to translate the absorbed light for each leaf into a produced amount of carbohydrates. The carbohydrates produced by the crop per unit emitted light from sun or high pressure sodium lamps was the highest for horizontal leaf angles or slightly downward pointing leaves, and was less for more upward leaf orientations. The simulated leaf angles did not affect light absorption from inter-lighting LED modules, but the scenario with LEDs shining slightly upward (20°) increased light absorption and LUE relative to default horizontal beaming LEDs. Furthermore, the model showed that leaf orientation more perpendicular to the string of LEDs increased LED light interception. The combination of a ray tracer and a 3D crop model could compute optimal lighting of leaves by quantification of light fluxes and illustration by rendered lighting patterns. Results indicate that illumination efficiency increases when the lamp light is directed at most to leaves that have a high photosynthetic potential. PMID:24600461

Is light-emitting diode phototherapy (LED-LLLT) really effective?

PubMed Central

Kim, Won-Serk; Calderhead, R Glen

2011-01-01

Background: Low level light therapy (LLLT) has attracted attention in many clinical fields with a new generation of light-emitting diodes (LEDs) which can irradiate large targets. To pain control, the first main application of LLLT, have been added LED-LLLT in the accelerated healing of wounds, both traumatic and iatrogenic, inflammatory acne and the patient-driven application of skin rejuvenation. Rationale and Applications: The rationale behind LED-LLLT is underpinned by the reported efficacy of LED-LLLT at a cellular and subcellular level, particularly for the 633 nm and 830 nm wavelengths, and evidence for this is presented. Improved blood flow and neovascularization are associated with 830 nm. A large variety of cytokines, chemokines and macromolecules can be induced by LED phototherapy. Among the clinical applications, non-healing wounds can be healed through restoring the collagenesis/collagenase imbalance in such examples, and ‘normal’ wounds heal faster and better. Pain, including postoperative pain, postoperative edema and many types of inflammation can be significantly reduced. Experimental and clinical evidence: Some personal examples of evidence are offered by the first author, including controlled animal models demonstrating the systemic effect of 830 nm LED-LLLT on wound healing and on induced inflammation. Human patients are presented to illustrate the efficacy of LED phototherapy on treatment-resistant inflammatory disorders. Conclusions: Provided an LED phototherapy system has the correct wavelength for the target cells, delivers an appropriate power density and an adequate energy density, then it will be at least partly, if not significantly, effective. The use of LED-LLLT as an adjunct to conventional surgical or nonsurgical indications is an even more exciting prospect. LED-LLLT is here to stay. PMID:24155530

Optimization lighting layout based on gene density improved genetic algorithm for indoor visible light communications

NASA Astrophysics Data System (ADS)

Liu, Huanlin; Wang, Xin; Chen, Yong; Kong, Deqian; Xia, Peijie

2017-05-01

For indoor visible light communication system, the layout of LED lamps affects the uniformity of the received power on communication plane. In order to find an optimized lighting layout that meets both the lighting needs and communication needs, a gene density genetic algorithm (GDGA) is proposed. In GDGA, a gene indicates a pair of abscissa and ordinate of a LED, and an individual represents a LED layout in the room. The segmented crossover operation and gene mutation strategy based on gene density are put forward to make the received power on communication plane more uniform and increase the population's diversity. A weighted differences function between individuals is designed as the fitness function of GDGA for reserving the population having the useful LED layout genetic information and ensuring the global convergence of GDGA. Comparing square layout and circular layout, with the optimized layout achieved by the GDGA, the power uniformity increases by 83.3%, 83.1% and 55.4%, respectively. Furthermore, the convergence of GDGA is verified compared with evolutionary algorithm (EA). Experimental results show that GDGA can quickly find an approximation of optimal layout.

Prediction of L70 lumen maintenance and chromaticity for LEDs using extended Kalman filter models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lall, Pradeep; Wei, Junchao; Davis, Lynn

2013-09-30

Solid-state lighting (SSL) luminaires containing light emitting diodes (LEDs) have the potential of seeing excessive temperatures when being transported across country or being stored in non-climate controlled warehouses. They are also being used in outdoor applications in desert environments that see little or no humidity but will experience extremely high temperatures during the day. This makes it important to increase our understanding of what effects high temperature exposure for a prolonged period of time will have on the usability and survivability of these devices. Traditional light sources “burn out” at end-of-life. For an incandescent bulb, the lamp life is definedmore » by B50 life. However, the LEDs have no filament to “burn”. The LEDs continually degrade and the light output decreases eventually below useful levels causing failure. Presently, the TM-21 test standard is used to predict the L70 life of LEDs from LM-80 test data. Several failure mechanisms may be active in a LED at a single time causing lumen depreciation. The underlying TM-21 Model may not capture the failure physics in presence of multiple failure mechanisms. Correlation of lumen maintenance with underlying physics of degradation at system-level is needed. In this paper, Kalman Filter (KF) and Extended Kalman Filters (EKF) have been used to develop a 70-percent Lumen Maintenance Life Prediction Model for LEDs used in SSL luminaires. Ten-thousand hour LM-80 test data for various LEDs have been used for model development. System state at each future time has been computed based on the state space at preceding time step, system dynamics matrix, control vector, control matrix, measurement matrix, measured vector, process noise and measurement noise. The future state of the lumen depreciation has been estimated based on a second order Kalman Filter model and a Bayesian Framework. The measured state variable has been related to the underlying damage using physics-based models. Life prediction of L70 life for the LEDs used in SSL luminaires from KF and EKF based models have been compared with the TM-21 model predictions and experimental data.« less

Prediction of Lumen Output and Chromaticity Shift in LEDs Using Kalman Filter and Extended Kalman Filter Based Models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lall, Pradeep; Wei, Junchao; Davis, J Lynn

2014-06-24

Abstract— Solid-state lighting (SSL) luminaires containing light emitting diodes (LEDs) have the potential of seeing excessive temperatures when being transported across country or being stored in non-climate controlled warehouses. They are also being used in outdoor applications in desert environments that see little or no humidity but will experience extremely high temperatures during the day. This makes it important to increase our understanding of what effects high temperature exposure for a prolonged period of time will have on the usability and survivability of these devices. Traditional light sources “burn out” at end-of-life. For an incandescent bulb, the lamp life ismore » defined by B50 life. However, the LEDs have no filament to “burn”. The LEDs continually degrade and the light output decreases eventually below useful levels causing failure. Presently, the TM-21 test standard is used to predict the L70 life of LEDs from LM-80 test data. Several failure mechanisms may be active in a LED at a single time causing lumen depreciation. The underlying TM-21 Model may not capture the failure physics in presence of multiple failure mechanisms. Correlation of lumen maintenance with underlying physics of degradation at system-level is needed. In this paper, Kalman Filter (KF) and Extended Kalman Filters (EKF) have been used to develop a 70-percent Lumen Maintenance Life Prediction Model for LEDs used in SSL luminaires. Ten-thousand hour LM-80 test data for various LEDs have been used for model development. System state at each future time has been computed based on the state space at preceding time step, system dynamics matrix, control vector, control matrix, measurement matrix, measured vector, process noise and measurement noise. The future state of the lumen depreciation has been estimated based on a second order Kalman Filter model and a Bayesian Framework. Life prediction of L70 life for the LEDs used in SSL luminaires from KF and EKF based models have been compared with the TM-21 model predictions and experimental data.« less

Detection of ICG at low concentrations by photoacoustic imaging system using LED light source

NASA Astrophysics Data System (ADS)

Shigeta, Yusuke; Agano, Toshitaka; Sato, Naoto; Nakatsuka, Hitoshi; Kitagawa, Kazuo; Hanaoka, Takamitsu; Morisono, Koji; Tanaka, Chizuyo

2017-03-01

Recently, various type of photoacoustic imaging (PAI) that can visualize properties and distribution of light absorber have been researched. We developed PAI system using LED light source and evaluated characteristics of photoacoustic signal intensity versus Indocyanine Green (ICG) concentration. In this experiment, a linear type PZT array transducer (128-elements, 10.0MHz center frequency) was used to be able to transmit and receive ultrasound and also detect photoacoustic signal from the target object. The transducer was connected to the PAI system, and two sets of LED light source that had 850nm wavelength chip array were set to the both side of the transducer. The transducer head was placed at a distance of 20 mm from the target in the water bath. The target object was a tube filled with ICG in it. The tubes containing ICG at concentrations from 300nanomolar to 3millimolar were made by diluting original ICG solution. We measured the photoacoustic signal strength from RF signal generated from the ICG in the tube, and the results showed that the intensity of the signal was almost linear response to the concentration in log-log scale.

Multi-dimensional spatial light communication made with on-chip InGaN photonic integration

NASA Astrophysics Data System (ADS)

Yang, Yongchao; Zhu, Bingcheng; Shi, Zheng; Wang, Jinyuan; Li, Xin; Gao, Xumin; Yuan, Jialei; Li, Yuanhang; Jiang, Yan; Wang, Yongjin

2017-04-01

Here, we propose, fabricate and characterize suspended photonic integration of InGaN multiple-quantum-well light-emitting diode (MQW-LED), waveguide and InGaN MQW-photodetector on a single chip. The unique light emission property of InGaN MQW-LED makes it feasible to establish multi-dimensional spatial data transmission using visible light. The in-plane light communication system is comprised of InGaN MQW-LED, waveguide and InGaN MQW-photodetector, and the out-of-plane data transmission is realized by detecting the free-space light emission via a commercial photodiode module. Moreover, a full-duplex light communication is experimentally demonstrated at a data transmission rate of 50 Mbps when both InGaN MQW-diodes operate under simultaneous light emission and detection mode. The in-plane superimposed signals are able to be extracted through the self-interference cancellation method, and the out-of-plane superimposed signals are in good agreement with the calculated signals according to the extracted transmitted signals. These results are promising for the development of on-chip InGaN photonic integration for diverse applications.

Thermal and optical aspects of glob-top design for phosphor converted white LED light sources

NASA Astrophysics Data System (ADS)

Sommer, Christian; Fulmek, Paul; Nicolics, Johann; Schweitzer, Susanne; Nemitz, Wolfgang; Hartmann, Paul; Pachler, Peter; Hoschopf, Hans; Schrank, Franz; Langer, Gregor; Wenzl, Franz P.

2013-09-01

For a systematic approach to improve the white light quality of phosphor converted light-emitting diodes (LEDs) for general lighting applications it is imperative to get the individual sources of error for correlated color temperature (CCT) reproducibility and maintenance under control. In this regard, it is of essential importance to understand how geometrical, optical and thermal properties of the color conversion elements (CCE), which typically consist of phosphor particles embedded in a transparent matrix material, affect the constancy of a desired CCT value. In this contribution we use an LED assembly consisting of an LED die mounted on a printed circuit board by chip-on-board technology and a CCE with a glob-top configuration on the top of it as a model system and discuss the impact of the CCE shape and size on CCT constancy with respect to substrate reflectivity and thermal load of the CCEs. From these studies, some general conclusions for improved glob-top design can be drawn.

Supplemental Upward Lighting from Underneath to Obtain Higher Marketable Lettuce (Lactuca sativa) Leaf Fresh Weight by Retarding Senescence of Outer Leaves

PubMed Central

Zhang, Geng; Shen, Shanqi; Takagaki, Michiko; Kozai, Toyoki; Yamori, Wataru

2015-01-01

Recently, the so-called “plant factory with artificial lighting” (PFAL) approach has been developed to provide safe and steady food production. Although PFALs can produce high-yielding and high-quality plants, the high plant density in these systems accelerates leaf senescence in the bottom (or outer) leaves owing to shading by the upper (or inner) leaves and by neighboring plants. This decreases yield and increases labor costs for trimming. Thus, the establishment of cultivation methods to retard senescence of outer leaves is an important research goal to improve PFAL yield and profitability. In the present study, we developed an LED lighting apparatus that would optimize light conditions for PFAL cultivation of a leafy vegetable. Lettuce (Lactuca sativa L.) was hydroponically grown under white, red, or blue LEDs, with light provided from above (downward), with or without supplemental upward lighting from underneath the plant. White LEDs proved more appropriate for lettuce growth than red or blue LEDs, and the supplemental lighting retarded the senescence of outer leaves and decreased waste (i.e., dead or low-quality senescent leaves), leading to an improvement of the marketable leaf fresh weight. PMID:26697055

LED light design method for high contrast and uniform illumination imaging in machine vision.

PubMed

Wu, Xiaojun; Gao, Guangming

2018-03-01

In machine vision, illumination is very critical to determine the complexity of the inspection algorithms. Proper lights can obtain clear and sharp images with the highest contrast and low noise between the interested object and the background, which is conducive to the target being located, measured, or inspected. Contrary to the empirically based trial-and-error convention to select the off-the-shelf LED light in machine vision, an optimization algorithm for LED light design is proposed in this paper. It is composed of the contrast optimization modeling and the uniform illumination technology for non-normal incidence (UINI). The contrast optimization model is built based on the surface reflection characteristics, e.g., the roughness, the reflective index, and light direction, etc., to maximize the contrast between the features of interest and the background. The UINI can keep the uniformity of the optimized lighting by the contrast optimization model. The simulation and experimental results demonstrate that the optimization algorithm is effective and suitable to produce images with the highest contrast and uniformity, which is very inspirational to the design of LED illumination systems in machine vision.

Measuring the Photocatalytic Breakdown of Crystal Violet Dye using a Light Emitting Diode Approach

NASA Technical Reports Server (NTRS)

Ryan, Robert E.; Underwood, Lauren W.; O'Neal, Duane; Pagnutti, Mary; Davis, Bruce A.

2009-01-01

A simple method to estimate the photocatalytic reactivity performance of spray-on titanium dioxide coatings for transmissive glass surfaces was developed. This novel technique provides a standardized method to evaluate the efficiency of photocatalytic material systems over a variety of illumination levels. To date, photocatalysis assessments have generally been conducted using mercury black light lamps. Illumination levels for these types of lamps are difficult to vary, consequently limiting their use for assessing material performance under a diverse range of simulated environmental conditions. This new technique uses an ultraviolet (UV) gallium nitride (GaN) light emitting diode (LED) array instead of a traditional black light to initiate and sustain photocatalytic breakdown. This method was tested with a UV-resistant dye (crystal violet) applied to a titanium dioxide coated glass slide. Experimental control is accomplished by applying crystal violet to both titanium dioxide coated slides and uncoated control slides. A slide is illuminated by the UV LED array, at various light levels representative of outdoor and indoor conditions, from the dye side of the slide. To monitor degradation of the dye over time, a temperature-stabilized white light LED, whose emission spectrum overlaps with the dye absorption spectrum, is used to illuminate the opposite side of the slide. Using a spectrometer, the amount of light from the white light LED transmitted through the slide as the dye degrades is monitored as a function of wavelength and time and is subsequently analyzed. In this way, the rate of degradation for photocatalytically coated versus uncoated slide surfaces can be compared. Results demonstrate that the dye absorption decreased much more rapidly on the photocatalytically coated slides than on the control uncoated slides, and that dye degradation is dependent on illumination level. For photocatalytic activity assessment purposes, this experimental configuration and methodology minimizes many external variable effects and enables small changes in absorption to be measured. This research also compares the advantages of this innovative LED light source design over traditional mercury black light systems and non- LED lamp approaches. This novel technology begins to address the growing need for a standard method that can assess the performance of photocatalytic materials before deployment for large scale, real world use.

The Involvement of the Oxidative Stress in Murine Blue LED Light-Induced Retinal Damage Model.

PubMed

Nakamura, Maho; Kuse, Yoshiki; Tsuruma, Kazuhiro; Shimazawa, Masamitsu; Hara, Hideaki

2017-01-01

The aim of study was to establish a mouse model of blue light emitting diode (LED) light-induced retinal damage and to evaluate the effects of the antioxidant N-acetylcysteine (NAC). Mice were exposed to 400 or 800 lx blue LED light for 2 h, and were evaluated for retinal damage 5 d later by electroretinogram amplitude and outer nuclear layer (ONL) thickness. Additionally, we investigated the effect of blue LED light exposure on shorts-wave-sensitive opsin (S-opsin), and rhodopsin expression by immunohistochemistry. Blue LED light induced light intensity dependent retinal damage and led to collapse of S-opsin and altered rhodopsin localization from inner and outer segments to ONL. Conversely, NAC administered at 100 or 250 mg/kg intraperitoneally twice a day, before dark adaptation and before light exposure. NAC protected the blue LED light-induced retinal damage in a dose-dependent manner. Further, blue LED light-induced decreasing of S-opsin levels and altered rhodopsin localization, which were suppressed by NAC. We established a mouse model of blue LED light-induced retinal damage and these findings indicated that oxidative stress was partially involved in blue LED light-induced retinal damage.

Damage of photoreceptor-derived cells in culture induced by light emitting diode-derived blue light

PubMed Central

Kuse, Yoshiki; Ogawa, Kenjiro; Tsuruma, Kazuhiro; Shimazawa, Masamitsu; Hara, Hideaki

2014-01-01

Our eyes are increasingly exposed to light from the emitting diode (LED) light of video display terminals (VDT) which contain much blue light. VDTs are equipped with televisions, personal computers, and smart phones. The present study aims to clarify the mechanism underlying blue LED light-induced photoreceptor cell damage. Murine cone photoreceptor-derived cells (661 W) were exposed to blue, white, or green LED light (0.38 mW/cm2). In the present study, blue LED light increased reactive oxygen species (ROS) production, altered the protein expression level, induced the aggregation of short-wavelength opsins (S-opsin), resulting in severe cell damage. While, blue LED light damaged the primary retinal cells and the damage was photoreceptor specific. N-Acetylcysteine (NAC), an antioxidant, protected against the cellular damage induced by blue LED light. Overall, the LED light induced cell damage was wavelength-, but not energy-dependent and may cause more severe retinal photoreceptor cell damage than the other LED light. PMID:24909301

Energy Optimization on the Battlefield: How Integrating Energy Efficient Technologies at the Tactical Level Can Reduce Fuel Consumption and Lessen the Burden of Fuel Logistics

DTIC Science & Technology

2014-06-13

a kill zone. This also created maintenance issues including diesel soot buildup in the vehicles exhaust systems. Since it took three to four days to...cost savings when summed over the thousands of light fixtures used on bases and FOBs. Changing to LEDs in tents and installing motion sensors could...CFL systems. Motion sensors also aided in turning lights off when the tents 78 are not occupied. Both LEDs and motion sensors produced significant

An LED-based UV-B irradiation system for tiny organisms: System description and demonstration experiment to determine the hatchability of eggs from four Tetranychus spider mite species from Okinawa.

PubMed

Suzuki, Takeshi; Yoshioka, Yoshio; Tsarsitalidou, Olga; Ntalia, Vivi; Ohno, Suguru; Ohyama, Katsumi; Kitashima, Yasuki; Gotoh, Tetsuo; Takeda, Makio; Koveos, Dimitris S

2014-03-01

We developed a computer-based system for controlling the photoperiod and irradiance of UV-B and white light from a 5×5 light-emitting diode (LED) matrix (100×100mm). In this system, the LED matrix was installed in each of four irradiation boxes and controlled by pulse-width modulators so that each box can independently emit UV-B and white light at irradiances of up to 1.5 and 4.0Wm(-2), respectively, or a combination of both light types. We used this system to examine the hatchabilities of the eggs of four Tetranychus spider mite species (T. urticae, T. kanzawai, T. piercei and T. okinawanus) collected from Okinawa Island under UV-B irradiation alone or simultaneous irradiation with white light for 12hd(-1) at 25°C. Although no eggs of any species hatched under the UV-B irradiation, even when the irradiance was as low as 0.02Wm(-2), the hatchabilities increased to >90% under simultaneous irradiation with 4.0Wm(-2) white light. At 0.06Wm(-2) UV-B, T. okinawanus eggs hatched (15% hatchability) under simultaneous irradiation with white light, whereas other species showed hatchabilities <1%. These results suggest that photolyases activated by white light may reduce UV-B-induced DNA damage in spider mite eggs and that the greater UV-B tolerance of T. okinawanus may explain its dominance on plants in seashore environments, which have a higher risk of exposure to reflected UV-B even on the undersurface of leaves. Our system will be useful for further examination of photophysiological responses of tiny organisms because of its ability to precisely control radiation conditions. Copyright © 2014 Elsevier Ltd. All rights reserved.

Energy-Saving Tunnel Illumination System Based on LED's Intelligent Control

NASA Astrophysics Data System (ADS)

Guo, Shanshan; Gu, Hanting; Wu, Lan; Jiang, Shuixiu

2011-02-01

At present there is a lot of electric energy wastage in tunnel illumination, whose design is based on the maximum brightness outside and the maximum vehicle speed all year round. LED's energy consumption is low, and the control of its brightness is simple and effective. It can be quickly adjusted between 0-100% of its maximum brightness, and will not affect the service life. Therefore, using LED as tunnel's illumination source, we can achieve a good energy saving effect. According to real-time data acquisition of vehicle speed, traffic flow and brightness outside the tunnel, the auto real-time control of tunnel illumination can be achieved. And the system regulated the LED luminance by means of combination of LED power module and intelligent control module. The tunnel information was detected by inspection equipments, which included luminometer, vehicle detector, and received by RTU(Remote Terminal Unit), then synchronously transmitted to PC. After data processing, RTU emitted the dimming signal to the LED driver to adjust the brightness of LED. Despite the relatively high cost of high-power LED lights, the enormous energy-saving effect and the well-behaved controllability is beyond compare to other lighting devices.

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

DOT National Transportation Integrated Search

2011-02-01

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

LED traffic signal management system : final report.

DOT National Transportation Integrated Search

2016-06-01

This research originated from the opportunity to develop a methodology to assess when LED (Light Emitting Diode) traffic signal modules begin to fail to meet the Institute of Transportation Engineers (ITE) performance specification for luminous inten...

Optical design of an in vivo laparoscopic lighting system.

PubMed

Liu, Xiaolong; Abdolmalaki, Reza Yazdanpanah; Mancini, Gregory J; Tan, Jindong

2017-12-01

This paper proposes an in vivo laparoscopic lighting system design to address the illumination issues, namely poor lighting uniformity and low optical efficiency, existing in the state-of-the-art in vivo laparoscopic cameras. The transformable design of the laparoscopic lighting system is capable of carrying purposefully designed freeform optical lenses for achieving lighting performance with high illuminance uniformity and high optical efficiency in a desired target region. To design freeform optical lenses for extended light sources such as LEDs with Lambertian light intensity distributions, we present an effective and complete freeform optical design method. The procedures include (1) ray map computation by numerically solving a standard Monge-Ampere equation; (2) initial freeform optical surface construction by using Snell's law and a lens volume restriction; (3) correction of surface normal vectors due to accumulated errors from the initially constructed surfaces; and (4) feedback modification of the solution to deal with degraded illuminance uniformity caused by the extended sizes of the LEDs. We employed an optical design software package to evaluate the performance of our laparoscopic lighting system design. The simulation results show that our design achieves greater than 95% illuminance uniformity and greater than 89% optical efficiency (considering Fresnel losses) for illuminating the target surgical region. (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

Lighting the Way for Quicker, Safer Healing

NASA Technical Reports Server (NTRS)

2005-01-01

Who's to say that a little light can t go a long way? Tiny light-emitting diode (LED) chips used to grow plants in space are lighting the way for cancer treatment, wound healing, and chronic pain alleviation on Earth. In 1993, Quantum Devices, Inc. (QDI), of Barneveld, Wisconsin, began developing the HEALS (High Emissivity Aluminiferous Light-emitting Substrate) technology to provide high-intensity, solid-state LED lighting systems for NASA Space Shuttle plant growth experiments. The company evolved out of cooperative efforts with the Wisconsin Center for Space Automation and Robotics (WCSAR) at the University of Wisconsin-Madison a NASA center for the Commercial Development of Space. Ronald W. Ignatius, QDI s president and chairman, represented one of WCSAR s industrial partners at the time. WCSAR was conducting research on light sources for promoting food growth within closed environments where humans would be present for a long duration, such as the Space Shuttle and the International Space Station. With the support of WCSAR, Ignatius experimented with LEDs, which provide high-energy efficiency and virtually no heat, despite releasing waves of light 10 times brighter than the Sun. Ignatius admits that some scientists involved in the project were skeptical at first, thinking that the idea of using LEDs to promote plant growth was far-fetched. The experiments, however, demonstrated that red LED wavelengths could boost the energy metabolism of cells to advance plant growth and photosynthesis. This finding prompted Ignatius to develop a line of LED products that emit the exact wavelength of light that plants use in photosynthesis. Our company gives credit to Dr. Ray Bula, the director of WCSAR, for having the foresight to go against the prevailing dogma of the time and design the first plant experiment using monochromatic light to grow lettuce plants, Ignatius proclaims. In 1989, Ignatius formed QDI to bring the salt grain-sized LEDs to market, and in October 1995, the light sources made their Space Shuttle flight debut on the second U.S. Microgravity Laboratory Spacelab mission (STS-73, Columbia)

Efficient coding and detection of ultra-long IDs for visible light positioning systems.

PubMed

Zhang, Hualong; Yang, Chuanchuan

2018-05-14

Visible light positioning (VLP) is a promising technique to complement Global Navigation Satellite System (GNSS) such as Global positioning system (GPS) and BeiDou Navigation Satellite System (BDS) which features the advantage of low-cost and high accuracy. The situation becomes even more crucial for indoor environments, where satellite signals are weak or even unavailable. For large-scale application of VLP, there would be a considerable number of Light emitting diode (LED) IDs, which bring forward the demand of long LED ID detection. In particular, to provision indoor localization globally, a convenient way is to program a unique ID into each LED during manufacture. This poses a big challenge for image sensors, such as the CMOS camera in everybody's hands since the long ID covers the span of multiple frames. In this paper, we investigate the detection of ultra-long ID using rolling shutter cameras. By analyzing the pattern of data loss in each frame, we proposed a novel coding technique to improve the efficiency of LED ID detection. We studied the performance of Reed-Solomon (RS) code in this system and designed a new coding method which considered the trade-off between performance and decoding complexity. Coding technique decreases the number of frames needed in data processing, significantly reduces the detection time, and improves the accuracy of detection. Numerical and experimental results show that the detected LED ID can be much longer with the coding technique. Besides, our proposed coding method is proved to achieve a performance close to that of RS code while the decoding complexity is much lower.

[Energy saving and LED lamp lighting and human health].

PubMed

Deĭnego, V N; Kaptsov, V A

2013-01-01

The appearance of new sources of high-intensity with large proportion of blue light in the spectrum revealed new risks of their influence on the function of the eye and human health, especially for children and teenagers. There is an urgent need to reconsider the research methods of vision hygiene in conditions of energy-saving and LED bulbs lighting. On the basis of a systematic approach and knowledge of the newly discovered photosensitive receptors there was built hierarchical model of the interaction of "light environment - the eye - the system of formation of visual images - the hormonal system of the person - his psycho-physiological state." This approach allowed us to develop a range of risk for the negative impact of spectrum on the functions of the eye and human health, as well as to formulate the hygiene requirements for energy-efficient high-intensity light sources.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Perrin, Tess E.; Davis, Robert G.; Wilkerson, Andrea M.

This GATEWAY project evaluated four field installations to better understand the long-term performance of a number of LED products, which can hopefully stimulate improvements in designing, manufacturing, specifying, procuring, and installing LED products. Field studies provide the opportunity to discover and investigate issues that cannot be simulated or uncovered in a laboratory, but the installed performance over time of commercially available LED products has not been well documented. Improving long-term performance can provide both direct energy savings by reducing the need to over-light to account for light loss and indirect energy savings through better market penetration due to SSL’s competitivemore » advantages over less-efficient light source technologies. The projects evaluated for this report illustrate that SSL use is often motivated by advantages other than energy savings, including maintenance savings, easier integration with control systems, and improved lighting quality.« less

Solid state lighting component

DOEpatents

Yuan, Thomas; Keller, Bernd; Tarsa, Eric; Ibbetson, James; Morgan, Frederick; Dowling, Kevin; Lys, Ihor

2017-10-17

An LED component according to the present invention comprising an array of LED chips mounted on a submount with the LED chips capable of emitting light in response to an electrical signal. The array can comprise LED chips emitting at two colors of light wherein the LED component emits light comprising the combination of the two colors of light. A single lens is included over the array of LED chips. The LED chip array can emit light of greater than 800 lumens with a drive current of less than 150 milli-Amps. The LED chip component can also operate at temperatures less than 3000 degrees K. In one embodiment, the LED array is in a substantially circular pattern on the submount.

LED solution for E14 candle lamp

NASA Astrophysics Data System (ADS)

Li, Yun; Liu, Ye; Boonekamp, Erik P.; Shi, Lei; Mei, Yi; Jiang, Tan; Guo, Qing; Wu, Huarong

2009-08-01

On a short to medium term, energy efficient retrofit LED products can offer an attractive solution for traditional lamps replacement in existing fixtures. To comply with user expectations, LED retrofit lamps should not only have the same mechanical interface to fit (socket and shape), but also have the similar light effect as the lamps they replace. The decorative lighting segment shows the best conditions to meet these requirements on short term. In 2008, Philips Lighting Shanghai started with the development of an LED candle lamp for the replacement of a 15W Candle shape (B35 E14) incandescent bulb, which is used in e.g. chandeliers. In this decorative application the main objective is not to generate as much light as possible, but the application requires the lamp to have a comparable look and, primarily, the same light effect as the incandescent candle lamp. This effect can be described as sparkling light, and it has to be directed sufficiently downwards (i.e., in the direction of the base of the lamp). These requirements leave very limited room for optics, electronics, mechanics and thermal design to play with in the small outline of this lamp. The main voltage AC LED concept is chosen to save the space for driver electronics. However the size of the AC LED is relatively big, which makes the optical design challenging. Several optical solutions to achieve the required light effect, to improve the optical efficiency, and to simplify the system are discussed. A novel prismatic lens has been developed which is capable of transforming the Lambertian light emission from typical high power LEDs into a butter-fly intensity distribution with the desired sparkling light effect. Thanks to this lens no reflecting chamber is needed, which improves the optical efficiency up to 70%, while maintaining the compact feature of the original optics. Together with advanced driver solution and thermal solution, the resulting LED candle lamp operates at 230V, consumes 1.8W, and delivers about 55 lm at 3000K with the requested radiation pattern and sparkle effect. Some field tests were done with positive feedback.

Spectral imaging analysis for silkworm gender classification

NASA Astrophysics Data System (ADS)

Sumriddetchkajorn, Sarun; Kamtongdee, Chakkrit; Sa-Ngiamsak, Chiranut

2013-05-01

We examine the effect of different wavelength spectra in the performance of our optical penetration-based silkworm pupa sex identification system. With available low-cost light emitting diodes (LEDs), each emitting different wavelength spectra at 468 nm, 565 nm, 639 nm, 940 nm, and broad white light, we find that the body of the silkworm pupa can block blue and near infrared light while allowing green and red light pass through. In particular, the red light can clearly highlight an important organ called "chitin gland" of the female, leading to high accuracy of silkworm gender identification. In our experiment with 120 silkworm pupae, measured high average 92.8% and lower average 87.5% accuracies in identifying silkworm gender are obtained under red and white light LEDs, respectively.

Note: A portable, light-emitting diode-based ruby fluorescence spectrometer for high-pressure calibration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng Yejun

2011-04-15

Ruby (Al{sub 2}O{sub 3}, with {approx}0.5 wt. % Cr doping) is one of the most widely used manometers at the giga-Pascal scale. Traditionally, its fluorescence is excited with intense laser sources. Here, I present a simple, robust, and portable design that employs light-emitting diodes (LEDs) instead. This LED-based system is safer in comparison with laser-based ones.

Performance of a novel LED lamp arrangement to reduce SNR fluctuation for multi-user visible light communication systems.

PubMed

Wang, Zixiong; Yu, Changyuan; Zhong, Wen-De; Chen, Jian; Chen, Wei

2012-02-13

This paper investigates the performance of our recently proposed LED lamp arrangement to reduce the SNR fluctuation from different locations in the room for multi-user visible light communications. The LED lamp arrangement consists of 4 LED lamps positioned in the corners and 12 LED lamps spread evenly on a circle. Our studies show that the SNR fluctuation under such a LED lamp arrangement is reduced from 14.5 dB to 0.9 dB, which guarantees that users can obtain almost identical communication quality, regardless of their locations. After time domain zero-forcing (ZF) equalization, the BER performances and channel capacities of 100-Mbit/s and 200-Mbit/s bipolar on-off-keying (OOK) signal with most significant inter-symbol interference (ISI) are very close to that of the channel without any ISI caused by this LED lamp arrangement.

Investigation of thermal management technique in blue LED airport taxiway fixtures

NASA Astrophysics Data System (ADS)

Gu, Yimin; Baker, Alex; Narendran, Nadarajah

2007-09-01

On airport runways, blue light fixtures denote taxiways between the runway and the airport terminal. Blue optics transmit mostly short-wavelength radiation, which makes traditional incandescent lamps a poor choice of light source; the resulting fixture efficiency could be less than one percent. LEDs are replacing incandescent lamps in this application. But unlike incandescent sources, LEDs do not radiate enough heat to melt ice and snow from the fixture optics. To meet Federal Aviation Administration (FAA) regulations for weatherability, some LED-based fixtures incorporate electric heaters that, when switched on, nearly negate the energy-savings benefit of converting to LED sources. In this study, we explored methods for conduction and convection of LED junction heat to taxiway fixture optics for the purpose of minimizing snow and ice buildup. A more efficient LED-based system compared to incandescent that would require no additional heaters was demonstrated.

340 nm pulsed UV LED system for europium-based time-resolved fluorescence detection of immunoassays.

PubMed

Rodenko, Olga; Fodgaard, Henrik; Tidemand-Lichtenberg, Peter; Petersen, Paul Michael; Pedersen, Christian

2016-09-19

We report on the design, development and investigation of an optical system based on UV light emitting diode (LED) excitation at 340 nm for time-resolved fluorescence detection of immunoassays. The system was tested to measure cardiac marker Troponin I with a concentration of 200 ng/L in immunoassay. The signal-to-noise ratio was comparable to state-of-the-art Xenon flash lamp based unit with equal excitation energy and without overdriving the LED. We performed a comparative study of the flash lamp and the LED based system and discussed temporal, spatial, and spectral features of the LED excitation for time-resolved fluorimetry. Optimization of the suggested key parameters of the LED promises significant increase of the signal-to-noise ratio and hence of the sensitivity of immunoassay systems.

Study of LED layout in indoor visible light communication and performance analysis

NASA Astrophysics Data System (ADS)

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 the signal noise ratio distribution is decreased result of the reflection of the wall. It is found that the received optical power of circular layout is better than the received optical power distribution of rectangulr layout, and circular layout is a good solution that add the received optical power at the 4 corners of room, improve the system ability of communication, when making a contrast of rectangular lyout with circular layout,at the same time,the fluctuate of circular layout's signal to noise ratio of is smller than rectangular layuot.The radius of circular layout or the location of rectangular layout is keeping, the received optical power of receiving plane is increased, by adding the number of LED,in the meantime, the interference between LED light source also increase. But the increase of the circular layout radius when the number of LED remain the same is helpful to reduce the inter symbol interference that work out between LED each other, enhance the system signal noise ratio. In this paper, the results of the reaearch provides a new idea for indoor visible light communication with non-standard room (Size of room is not 5mX5mX3m), at the same time, provides guiding significance for future setting up the indoor visible light communication links.

Robotic Arm Camera on Mars with Lights On

NASA Technical Reports Server (NTRS)

2008-01-01

This image is a composite view of NASA's Phoenix Mars Lander's Robotic Arm Camera (RAC) with its lights on, as seen by the lander's Surface Stereo Imager (SSI). This image combines images taken on the afternoon of Phoenix's 116th Martian day, or sol (September 22, 2008). The RAC is about 8 centimeters (3 inches) tall.

The SSI took images of the RAC to test both the light-emitting diodes (LEDs) and cover function. Individual images were taken in three SSI filters that correspond to the red, green, and blue LEDs one at a time. When combined, it appears that all three sets of LEDs are on at the same time. This composite image is not true color. The streaks of color extending from the LEDs are an artifact from saturated exposure.

The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

Recent advances in the science and technology for solid state lighting

NASA Astrophysics Data System (ADS)

Munkholm, Anneli

2003-03-01

Recent development of high power light emitting diodes (LEDs) has enabled fabrication of solid state devices with efficiencies that surpass that of incandescent light, as well as providing a total light output significantly exceeding that of conventional indicator LEDs. This breakthrough in high flux is opening up new applications for use of high power LEDs, such as liquid crystal display backlighting and automotive headlights. Some of the key elements to this technological breakthrough are the flip-chip device design, power packaging and phosphor coating technology, which will be discussed. In addition to device design improvements, our fundamental knowledge of the III-nitride material system is improving and has resulted in higher internal quantum efficiencies. Strain plays a significant role in complex AlInGaN heterostructures used in current devices. Using a multi-beam optical strain sensor (MOSS) system to measure the wafer curvature in situ, we have characterized the strain during metal-organic chemical vapor deposition of III-nitrides. Strain measurements of InGaN, AlGaN and Si-doped GaN films on GaN will be presented.

Efficient Visible Light Communication Transmitters Based on Switching-Mode dc-dc Converters.

PubMed

Rodríguez, Juan; Lamar, Diego G; Aller, Daniel G; Miaja, Pablo F; Sebastián, Javier

2018-04-07

Visible light communication (VLC) based on solid-state lighting (SSL) is a promising option either to supplement or to substitute existing radio frequency (RF) wireless communication in indoor environments. VLC systems take advantage of the fast modulation of the visible light that light emitting diodes (LEDs) enable. The switching-mode dc-to-dc converter (SMC dc-dc ) must be the cornerstone of the LED driver of VLC transmitters in order to incorporate the communication functionality into LED lighting, keeping high power efficiency. However, the new requirements related to the communication, especially the high bandwidth that the LED driver must achieve, converts the design of the SMC dc-dc into a very challenging task. In this work, three different methods for achieving such a high bandwidth with an SMC dc-dc are presented: increasing the order of the SMC dc-dc output filter, increasing the number of voltage inputs, and increasing the number of phases. These three strategies are combinable and the optimum design depends on the particular VLC application, which determines the requirements of the VLC transmitter. As an example, an experimental VLC transmitter based on a two-phase buck converter with a fourth-order output filter will demonstrate that a bandwidth of several hundred kilohertz (kHz) can be achieved with output power levels close to 10 W and power efficiencies between 85% and 90%. In conclusion, the design strategy presented allows us to incorporate VLC into SSL, achieving high bit rates without damaging the power efficiency of LED lighting.

Efficient Visible Light Communication Transmitters Based on Switching-Mode dc-dc Converters

PubMed Central

2018-01-01

Visible light communication (VLC) based on solid-state lighting (SSL) is a promising option either to supplement or to substitute existing radio frequency (RF) wireless communication in indoor environments. VLC systems take advantage of the fast modulation of the visible light that light emitting diodes (LEDs) enable. The switching-mode dc-to-dc converter (SMCdc-dc) must be the cornerstone of the LED driver of VLC transmitters in order to incorporate the communication functionality into LED lighting, keeping high power efficiency. However, the new requirements related to the communication, especially the high bandwidth that the LED driver must achieve, converts the design of the SMCdc-dc into a very challenging task. In this work, three different methods for achieving such a high bandwidth with an SMCdc-dc are presented: increasing the order of the SMCdc-dc output filter, increasing the number of voltage inputs, and increasing the number of phases. These three strategies are combinable and the optimum design depends on the particular VLC application, which determines the requirements of the VLC transmitter. As an example, an experimental VLC transmitter based on a two-phase buck converter with a fourth-order output filter will demonstrate that a bandwidth of several hundred kilohertz (kHz) can be achieved with output power levels close to 10 W and power efficiencies between 85% and 90%. In conclusion, the design strategy presented allows us to incorporate VLC into SSL, achieving high bit rates without damaging the power efficiency of LED lighting. PMID:29642455

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

PubMed

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-Efficiency Nitride-Base Photonic Crystal Light Sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

James Speck; Evelyn Hu; Claude Weisbuch

2010-01-31

The research activities performed in the framework of this project represent a major breakthrough in the demonstration of Photonic Crystals (PhC) as a competitive technology for LEDs with high light extraction efficiency. The goals of the project were to explore the viable approaches to manufacturability of PhC LEDS through proven standard industrial processes, establish the limits of light extraction by various concepts of PhC LEDs, and determine the possible advantages of PhC LEDs over current and forthcoming LED extraction concepts. We have developed three very different geometries for PhC light extraction in LEDs. In addition, we have demonstrated reliable methodsmore » for their in-depth analysis allowing the extraction of important parameters such as light extraction efficiency, modal extraction length, directionality, internal and external quantum efficiency. The information gained allows better understanding of the physical processes and the effect of the design parameters on the light directionality and extraction efficiency. As a result, we produced LEDs with controllable emission directionality and a state of the art extraction efficiency that goes up to 94%. Those devices are based on embedded air-gap PhC - a novel technology concept developed in the framework of this project. They rely on a simple and planar fabrication process that is very interesting for industrial implementation due to its robustness and scalability. In fact, besides the additional patterning and regrowth steps, the process is identical as that for standard industrially used p-side-up LEDs. The final devices exhibit the same good electrical characteristics and high process yield as a series of test standard LEDs obtained in comparable conditions. Finally, the technology of embedded air-gap patterns (PhC) has significant potential in other related fields such as: increasing the optical mode interaction with the active region in semiconductor lasers; increasing the coupling of the incident light into the active region of solar cells; increasing the efficiency of the phosphorous light conversion in white light LEDs etc. In addition to the technology of embedded PhC LEDs, we demonstrate a technique for improvement of the light extraction and emission directionality for existing flip-chip microcavity (thin) LEDs by introducing PhC grating into the top n-contact. Although, the performances of these devices in terms of increase of the extraction efficiency are not significantly superior compared to those obtained by other techniques like surface roughening, the use of PhC offers some significant advantages such as improved and controllable emission directionality and a process that is directly applicable to any material system. The PhC microcavity LEDs have also potential for industrial implementation as the fabrication process has only minor differences to that already used for flip-chip thin LEDs. Finally, we have demonstrated that achieving good electrical properties and high fabrication yield for these devices is straightforward.« less

Light Emitting Diodes and Astronomy - a chance for restoration of the dark night sky - or for further loss

NASA Astrophysics Data System (ADS)

Wainscoat, Richard

2015-08-01

Across the planet, conventional light sources such as high pressure sodium, are rapidly being replaced by light emitting diodes (LEDs). As light fixtures are being replaced, there is a tremendous opportunity for restoration of dark night skies through replacement of poorly shielded fixtures by fully shielded fixtures. However, it is critically important to limit the amount of blue light from the LEDs.Sales people are strongly promoting LEDs with high correlated color temperature (CCT), such as 5000K. They are promoting them on energy efficiency grounds - higher energy efficiency is easier to sell. These LEDs have tremendous amounts of blue light near 450 nm. The photopic human eye is relatively insensitive to this blue light, but the dark adapted scotopic eye is much more sensitive, and CCDs are also very sensitive to this wavelength of light. As a consequence, both professional and amateur astronomers are very seriously impacted by high CCT LED lighting. The sodium lighting that the LEDs are replacing has relatively little blue light. Blue light is strongly scattered by air molecules in the atmosphere.Use of high CCT LED lighting will cause further deterioration of night sky quality.In contrast, use of LED lighting with low CCT (e.g., 2400K or 2700K), or use of filters to remove the blue light, can restore the dark night sky. LED lighting is much easier to direct, meaning that an area such as a roadway can be lit with many less lumens with LEDs compared to conventional lights such as high pressure sodium. And use of fully shielded fixtures will eliminate direct uplighting.It is therefore critically important at this time to require that all new LED lighting be fully shielded, and for strong limits to be placed the amount of blue light from LEDs. This is crucial near observatories, but is important everywhere.

Development of optics with micro-LED arrays for improved opto-electronic neural stimulation

NASA Astrophysics Data System (ADS)

Chaudet, Lionel; Neil, Mark; Degenaar, Patrick; Mehran, Kamyar; Berlinguer-Palmini, Rolando; Corbet, Brian; Maaskant, Pleun; Rogerson, David; Lanigan, Peter; Bamberg, Ernst; Roska, Botond

2013-03-01

The breakthrough discovery of a nanoscale optically gated ion channel protein, Channelrhodopsin 2 (ChR2), and its combination with a genetically expressed ion pump, Halorhodopsin, allowed the direct stimulation and inhibition of individual action potentials with light alone. This work reports developments of ultra-bright elec­ tronically controlled optical array sources with enhanced light gated ion channels and pumps for use in systems to further our understanding of both brain and visual function. This work is undertaken as part of the European project, OptoNeuro. Micro-LED arrays permit spatio-temporal control of neuron stimulation on sub-millisecond timescales. However they are disadvantaged by their broad spatial light emission distribution and low fill factor. We present the design and implementation of a projection and micro-optics system for use with a micro-LED array consisting of a 16x16 matrix of 25 μm diameter micro-LEDs with 150 μm centre-to-centre spacing and an emission spectrum centred at 470 nm overlapping the peak sensitivity of ChR2 and its testing on biological samples. The projection system images the micro-LED array onto micro-optics to improve the fill-factor from ~2% to more than 78% by capturing a larger fraction of the LED emission and directing it correctly to the sample plane. This approach allows low fill factor arrays to be used effectively, which in turn has benefits in terms of thermal management and electrical drive from CMOS backplane electronics. The entire projection system is integrated into a microscope prototype to provide stimulation spots at the same size as the neuron cell body (μ10 pm).

Fluorescent light induces neurodegeneration in the rodent nigrostriatal system but near infrared LED light does not.

PubMed

Romeo, Stefania; Vitale, Flora; Viaggi, Cristina; di Marco, Stefano; Aloisi, Gabriella; Fasciani, Irene; Pardini, Carla; Pietrantoni, Ilaria; Di Paolo, Mattia; Riccitelli, Serena; Maccarone, Rita; Mattei, Claudia; Capannolo, Marta; Rossi, Mario; Capozzo, Annamaria; Corsini, Giovanni U; Scarnati, Eugenio; Lozzi, Luca; Vaglini, Francesca; Maggio, Roberto

2017-05-01

We investigated the effects of continuous artificial light exposure on the mouse substantia nigra (SN). A three month exposure of C57Bl/6J mice to white fluorescent light induced a 30% reduction in dopamine (DA) neurons in SN compared to controls, accompanied by a decrease of DA and its metabolites in the striatum. After six months of exposure, neurodegeneration progressed slightly, but the level of DA returned to the basal level, while the metabolites increased with respect to the control. Three month exposure to near infrared LED light (∼710nm) did not alter DA neurons in SN, nor did it decrease DA and its metabolites in the striatum. Furthermore mesencephalic cell viability, as tested by [ 3 H]DA uptake, did not change. Finally, we observed that 710nm LED light, locally conveyed in the rat SN, could modulate the firing activity of extracellular-recorded DA neurons. These data suggest that light can be detrimental or beneficial to DA neurons in SN, depending on the source and wavelength. Copyright © 2017 Elsevier B.V. All rights reserved.

Investigation of pitch and angle in the gradual-triangle lenticular lens for point-blank LED fog lamp.

PubMed

Chen, Hsi-Chao; Yang, Chi-Hao

2014-05-10

The effects of different pitch and angle of gradual-triangle lenticular lens for the point-blank LED fog lamp were investigated under the standard of ECE R19. The novel LED fog lamp was assembled from a point-blank LED light source, a parabolic reflector, and a gradual-triangle lenticular lens. Light tracing analysis was used for the design of the gradual-triangle lenticular lens. The pitch, which varied from 1 to 6 mm, and the apex angle, which changed from 5 to 32 deg, were both investigated in regard to the gradual-triangle lenticular lens. The optimum pitch was 5 mm, and the efficiency of the lamp system and lenticular lens could reach 93% and 98.1% by simulation, respectively. The results of experiment had over 94%, which is similar to that of simulation by normalized cross correlation (NCC) for the light intensity.

Molecular Engineering of UV/Vis Light-Emitting Diode (LED)-Sensitive Donor-π-Acceptor-Type Sulfonium Salt Photoacid Generators: Design, Synthesis, and Study of Photochemical and Photophysical Properties.

PubMed

Wu, Xingyu; Jin, Ming; Xie, Jianchao; Malval, Jean-Pierre; Wan, Decheng

2017-11-07

A series of donor-π-acceptor-type sulfonium salt photoacid generators (PAGs) were designed and synthesized by systematically changing electron-donating groups, π-conjugated systems, electron-withdrawing groups, and the number of branches through molecular engineering. These PAGs can effectively decompose under UV/Vis irradiation from a light-emitting diode (LED) light source because of the matching absorption and emitting spectra of the LEDs. The absorption and acid-generation properties of these sulfonium salts were elucidated by UV/Vis spectroscopy and so forth. Results indicated that the PAG performance benefited from the introduction of strong electron-donating groups, specific π-conjugated structures, certain electron-withdrawing groups, or two-branched structures. Most sulfonium salts showed potential as photoinitiators under irradiation by a wide variety of UV and visible LEDs. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Polarization-multiplexed 2×2 phosphor-LED wireless light communication without using analog equalization and optical blue filter

NASA Astrophysics Data System (ADS)

Yeh, C. H.; Chen, H. Y.; Liu, Y. L.; Chow, C. W.

2015-01-01

We propose and experimentally demonstrate a 380 (2×190) Mbps phosphor-light-emitting-diode (LED) based visible light communication (VLC) system by using 2×2 polarization-multiplexing design for in-building access applications. To the best of our knowledge, this is the first time of employing polarization-multiplexing to achieve a high VLC transmission capacity by using phosphor-based white-LED without optical blue filter. Besides, utilizing the optimum resistor-inductor-capacity (RLC) bias-tee design, it can not only perform the function of combining the direct-current (DC) and the electrical data signal, but also act as a simple LED-Tx circuit. No optical blue filter and complicated post-equalization are required at the Rx. Here, the orthogonal-frequency-division-multiplexing (OFDM) quadrature-amplitude-modulation (QAM) with bit-loading is employed to enhance the transmission data rate.

Understanding possible underlying mechanism in declining germicidal efficiency of UV-LED reactor.

PubMed

Lee, Hyunkyung; Jin, Yongxun; Hong, Seungkwan

2018-06-07

Since ultraviolet light emitting diodes (UV-LEDs) have emerged as an alternative light source for UV disinfection systems, enhancement of reactor performance is a demanding challenge to promote its practical application in water treatment process. This study explored the underlying mechanism of the inefficiency observed in flow-through mode UV disinfection tests to improve the light utilization of UV-LED applications. In particular, the disinfection performance of UV-LED reactors was evaluated using two different flow channel types, reservoir and pathway systems, in order to elucidate the impact of physical circumstances on germicidal efficiency as the light profile was adjusted. Overall, a significant reduction in germicidal efficiency was observed when exposure time was prolonged or a mixing chamber was integrated. Zeta analysis revealed that the repulsion rate between microorganisms decreased with UV fluence transfer, and that change might cause the shielding effect of UV delivery to target microorganisms. In line with the above findings, the reduction in efficiency intensified when opportunities for microbial collision increased. Thus, UV induced microbial aggregation was implicated as being a disinfection hindering factor, exerting its effect through uneven UV illumination. Ultimately, the results refuted the prevailing belief that UV has a cumulative effect. We found that the reservoir system achieved worse performance than the pathway system despite it providing 15 times higher UV fluence: the differences in germicidal efficiency were 1-log, 1.4-log and 1.7-log in the cases of P.aeruginosa, E.coli and S.aureus, respectively. Copyright © 2018 Elsevier B.V. All rights reserved.

Materials for Space Exploration

NASA Technical Reports Server (NTRS)

Robertson, Luke B.; Williams, Martha

2010-01-01

Topics include a lab overview, testing and processing equipment, hemochromic hydrogen sensors, antimicrobial materials, wire system materials, CNT ink formulations, CNT ink dust screens, CNT ink printed circuitry, cryogenic materials development, fire and polymers, the importance of lighting, electric lighting systems, LED for plant growth, and carbon nanotube fiber filaments.

Innovative roadway light source and dye combinations to improve visibility and reduce environmental impacts.

DOT National Transportation Integrated Search

2013-04-01

Sky glow light pollution is caused largely by reflected light off of roadway and other surfaces. The : authors investigated the feasibility of a system consisting of a specialized LED streetlight and a dyebased : roadway surface coating that would re...

[LED LIGHTING AS A FACTOR FOR THE STIMULATION OF THE HORMONE SYSTEM].

PubMed

Deynego, V N; Kaptsov, V A

2015-01-01

There are considered questions of non-visual effects of blue LED light sources on hormonal systems (cortisol, glucose, insulin) providing the high human performance. In modern conditions hygiene strategy for child and adolescent health strategy was shown to be replaced by a strategy of light stimulation of the hormonal profile. There was performed a systematic analysis of the axis "light stimulus-hypothalamus-pituitary-adrenals-cortisol-glucose-insulin". The elevation of the content of cortisol leads to the increase of the glucose level in the blood and the stimulation of the production of insulin, which can, like excessive consumption of food, give rise to irreversible decline in the number of insulin receptors on the cell surface, and thus--to a steady reduction in the ability of cells to utilize glucose, i.e. to type 2 diabetes or its aggravation.

Development of a new water sterilization device with a 365 nm UV-LED.

PubMed

Mori, Mirei; Hamamoto, Akiko; Takahashi, Akira; Nakano, Masayuki; Wakikawa, Noriko; Tachibana, Satoko; Ikehara, Toshitaka; Nakaya, Yutaka; Akutagawa, Masatake; Kinouchi, Yohsuke

2007-12-01

Ultraviolet (UV) irradiation is an effective disinfection method. In sterilization equipment, a low-pressure mercury lamp emitting an effective germicidal UVC (254 nm) is used as the light source. However, the lamp, which contains mercury, must be disposed of at the end of its lifetime or following damage due to physical shock or vibration. We investigated the suitability of an ultraviolet light-emitting diode at an output wavelength of 365 nm (UVA-LED) as a sterilization device, comparing with the other wavelength irradiation such as 254 nm (a low-pressure mercury lam) and 405 nm (LED). We used a commercially available UVA-LED that emitted light at the shortest wavelength and at the highest output energy. The new sterilization system using the UVA-LED was able to inactivate bacteria, such as Escherichia coli DH5 alpha, Enteropathogenic E. coli, Vibrio parahaemolyticus, Staphylococcus aureus, and Salmonella enterica serovar Enteritidis. The inactivations of the bacteria were dependent on the accumulation of UVA irradiation. Taking advantage of the safety and compact size of LED devices, we expect that the UVA-LED sterilization device can be developed as a new type of water sterilization device.

Effect of radiant heat on conventional glass ionomer cements during setting by using a blue light diode laser system (445 nm).

PubMed

Dionysopoulos, Dimitrios; Tolidis, Kosmas; Strakas, Dimitrios; Gerasimou, Paris; Sfeikos, Thrasyvoulos; Gutknecht, Norbert

2017-04-01

The aim of this in vitro study was to evaluate the effect of radiant heat on surface hardness of three conventional glass ionomer cements (GICs) by using a blue diode laser system (445 nm) and a light-emitting diode (LED) unit. Additionally, the safety of the laser treatment was evaluated. Thirty disk-shaped specimens were prepared of each tested GIC (Equia Fil, Ketac Universal Aplicap and Riva Self Cure). The experimental groups (n = 10) of the study were as follows: group 1 was the control group of the study; in group 2, the specimens were irradiated for 60 s at the top surface using a LED light-curing unit; and in group 3, the specimens were irradiated for 60 s at the top surface using a blue light diode laser system (445 nm). Statistical analysis was performed using one-way ANOVA and Tukey post-hoc tests at a level of significance of a = 0.05. Radiant heat treatments, with both laser and LED devices, increased surface hardness (p < 0.05) but in different extent. Blue diode laser treatment was seemed to be more effective compared to LED treatment. There were no alterations in surface morphology or chemical composition after laser treatment. The tested radiant heat treatment with a blue diode laser may be advantageous for the longevity of GIC restorations. The safety of the use of blue diode laser for this application was confirmed.

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

NASA Astrophysics Data System (ADS)

Spanard, Jan-Marie

2017-10-01

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

Algorithm to illustrate context using dynamic lighting effects

NASA Astrophysics Data System (ADS)

John, Roshy M.; Balasubramanian, T.

2007-09-01

With the invention of Ultra-Bright LED, solid state lighting has come to something which is much more efficient and energy saving when compared to conventional incandescent or fluorescent lighting. With the use of proper driver electronics now a days it is possible to install solid state lighting systems with the cost same as that of any other lighting technology. This paper is a part of the research project we are doing in our lab, which deals with using ultra bright LEDs of different colors for lighting applications. The driver electronics are made in such a way that, the color and brightness of the lights will change according to context. For instance, if one of the users is reading a story or listening to music in a Personal Computer or in a hand held device such as a PDA, the lighting systems and the HVAC (Heating Ventilation Air-conditioning) systems will change dramatically according to the content of the story or the music. The vulnerability of solid-state lighting helps to accomplish such an effect. Such a type of system will help the reader to feel the story mentally and physically as well. We developed complete driver electronics for the system using multiple microcomputers and a full software suite which uses complex algorithms to decode the context from text or music and synchronize it to lighting and HVAC information. The paper also presents some case-study statistics which shows the advantage of using the system to teach kindergarten children, deaf and dumb children and for language learning classes.

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

NASA Astrophysics Data System (ADS)

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.

Optical Indoor Positioning System Based on TFT Technology.

PubMed

Gőzse, István

2015-12-24

A novel indoor positioning system is presented in the paper. Similarly to the camera-based solutions, it is based on visual detection, but it conceptually differs from the classical approaches. First, the objects are marked by LEDs, and second, a special sensing unit is applied, instead of a camera, to track the motion of the markers. This sensing unit realizes a modified pinhole camera model, where the light-sensing area is fixed and consists of a small number of sensing elements (photodiodes), and it is the hole that can be moved. The markers are tracked by controlling the motion of the hole, such that the light of the LEDs always hits the photodiodes. The proposed concept has several advantages: Apart from its low computational demands, it is insensitive to the disturbing ambient light. Moreover, as every component of the system can be realized by simple and inexpensive elements, the overall cost of the system can be kept low.

Seed-to-seed growth of superdwarf wheat and arabidopsis using red light-emitting diodes (LED's): A report on baseline tests conducted for NASA's proposed Plant Research Unit (PRU)

NASA Technical Reports Server (NTRS)

Goins, G. D.; Yorio, N. C.; Sanwo, M. M.; Brown, C. S.

1996-01-01

To determine the influence of narrow-spectrum red light-emitting diodes (LED's) on plant growth and seed production, wheat (Triticum aestivum L.cv Superdwarf) and Arabidopsis (Arabidopsis thaliana (L.) Heynh, race Columbia) plants were grown under red LED's (peak emission 660 nm) and compared to plants grown under daylight fluorescent (white) light and red LED's supplemented with either 1 percent or 10 percent blue fluorescent (BF) light. Wheat growth under red LED's alone appeared normal, whereas Arabidopsis under red LED's alone developed curled leaf margins and a spiraling growth pattern. Both wheat and Arabidopsis under red LED's alone or red LED's + 1 percent BF light had significantly lower seed yield than plants grown under white light. However, the addition of 10 percent BF light to red LED's partially alleviated the adverse effect of red LED's on yield. Irrespective of the light treatment, viable seeds were produced by wheat(75-92 percent germination rate) and Arabidopsis (85-100 percent germination rate). These results indicate that wheat, and to a lesser extent Arabidopsis, can be successfully grown under red LED's alone, but supplemental blue light is required with red LED's to sufficiently match the growth characteristics and seed yield associated with plants grown under white light.

GATEWAY Demonstrations: LED System Performance in a Trial Installation--Two Years Later, Yuma Border Patrol, Yuma, Arizona

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilkerson, Andrea M.; Sullivan, Gregory P.; Davis, Robert G.

Along the Yuma Sector Border Patrol Area in Yuma, Arizona, the GATEWAY program conducted a trial demonstration in which the incumbent quartz metal halide area lighting was replaced with LED at three pole locations at the Yuma Sector Border Patrol Area in Yuma, Arizona. The retrofit was documented to better understand LED technology performance in high-temperature environments. This report follows the GATEWAY Yuma Phase 1.1 Report and reflects LED system results documented two years after the demonstration began.

GATEWAY Demonstrations: LED System Performance in a Trial Installation--One Year Later, Yuma Border Patrol, Yuma, Arizona

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilkerson, A. M.; Davis, R. G.

Along the Yuma Sector Border Patrol Area in Yuma, Arizona, the GATEWAY program conducted a trial demonstration in which the incumbent quartz metal halide area lighting was replaced with LED at three pole locations at the Yuma Sector Border Patrol Area in Yuma, Arizona. The retrofit was documented to better understand LED technology performance in high-temperature environments. This report follows the GATEWAY Yuma Phase 1.0 Report and reflects LED system results documented one year after the demonstration began.

Optical signal processing for a smart vehicle lighting system using a-SiCH technology

NASA Astrophysics Data System (ADS)

Vieira, M. A.; Vieira, M.; Vieira, P.; Louro, P.

2017-05-01

We propose the use of Visible Light Communication (VLC) for vehicle safety applications, creating a smart vehicle lighting system that combines the functions of illumination and signaling, communications, and positioning. The feasibility of VLC is demonstrated by employing trichromatic Red-Green-Blue (RGB) LEDs as transmitters, since they offer the possibility of Wavelength Division Multiplexing (WDM), which can greatly increase the transmission data rate, when using SiC double p-i-n receivers to encode/decode the information. Trichromatic RGB Light Emitting Diodes (LED)s (RGB-LED) are used together for illumination proposes (headlamps) and individually, each chip, to transmit the driving range distance and data information. An on-off code is used to transmit the data. Free space is the transmission medium. The receivers consist of two stacked amorphous a-H:SiC cells. They combine the simultaneous demultiplexing operation with the photodetection and self-amplification. The proposed coding is based on SiC technology. Multiple Input Multi Output (MIMO) architecture is used. For data transmission, we propose the use of two headlights based on commercially available modulated white RGB-LEDs. For data receiving and decoding we use three a-SiC:H double pin/pin optical processors symmetrically distributed at the vehicle tail Moreover, we present a way to achieve vehicular communication using the parity bits. A representation with a 4 bit original string color message and the transmitted 7 bit string, the encoding and decoding accurate positional information processes and the design of SiC navigation system are discussed and tested. A visible multilateration method estimates the drive distance range by using the decoded information received from several non-collinear transmitters.

Baker-Barry Tunnel Lighting: Evaluation of a Potential GATEWAY Demonstrations Project

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tuenge, Jason R.

2011-06-28

The U.S. Department of Energy is evaluating the Baker-Barry Tunnel as a potential GATEWAY Demonstrations project for deployment of solid-state lighting (SSL) technology. The National Park Service views this project as a possible proving ground and template for implementation of light-emitting diode (LED) luminaires in other tunnels, thereby expanding the estimated 40% energy savings from 132 MWh/yr to a much larger figure nationally. Most of the energy savings in this application is attributable to the instant-restrike capability of LED products and to their high tolerance for frequent on/off switching, used here to separately control either end of the tunnel duringmore » daytime hours. Some LED luminaires rival or outperform their high-intensity discharge (HID) counterparts in terms of efficacy, but options are limited, and smaller lumen packages preclude true one-for-one equivalence. However, LED products continue to improve in efficacy and affordability at a rate unmatched by other light source technologies; the estimated simple payback period of eight years (excluding installation costs and maintenance savings) can be expected to improve with time. The proposed revisions to the existing high-pressure sodium (HPS) lighting system would require slightly increased controls complexity and significantly increased luminaire types and quantities. In exchange, substantial annual savings (from reduced maintenance and energy use) would be complemented by improved quantity and quality of illumination. Although advanced lighting controls could offer additional savings, it is unclear whether such a system would prove cost-effective; this topic may be explored in future work.« less

Thermal characterizations analysis of high-power ThinGaN cool-white light-emitting diodes

NASA Astrophysics Data System (ADS)

Raypah, Muna E.; Devarajan, Mutharasu; Ahmed, Anas A.; Sulaiman, Fauziah

2018-03-01

Analysis of thermal properties plays an important role in the thermal management of high-power (HP) lighting-emitting diodes (LEDs). Thermal resistance, thermal capacitance, and thermal time constant are essential parameters for the optimal design of the LED device and system, particularly for dynamic performance study. In this paper, thermal characterization and thermal time constant of ThinGaN HP LEDs are investigated. Three HP cool-white ThinGaN LEDs from different manufacturers are used in this study. A forward-voltage method using thermal transient tester (T3Ster) system is employed to determine the LEDs' thermal parameters at various operating conditions. The junction temperature transient response is described by a multi-exponential function model to extract thermal time constants. The transient response curve is divided into three layers and expressed by three exponential functions. Each layer is associated with a particular thermal time constant, thermal resistance, and thermal capacitance. It is found that the thermal time constant of LED package is on the order of 22 to 100 ms. Comparison between the experimental results is carried out to show the design effects on thermal performance of the LED package.

Development of an antimicrobial blended white LED system containing pulsed 405nm LEDs for decontamination applications

NASA Astrophysics Data System (ADS)

Gillespie, Jonathan B.; Maclean, Michelle; Wilson, Mark P.; Given, Martin J.; MacGregor, Scott J.

2017-03-01

This study details the design, build and testing of a prototype antimicrobial blended white light unit containing pulsed red, yellow, green and 405nm LEDs. With a push for alternative methods of disinfection, optical methods have become a topic of interest. Ultra-violet (UV) light is widely known for its antimicrobial properties however; 405nm light has demonstrated significant antimicrobial properties against many common hospital acquired pathogens. In this study, a pulsed, blended, white-light prototype with a high content of 405 nm antimicrobial light, was designed, built and tested. Antimicrobial efficacy testing of the prototype was conducted using Staphylococcus aureus and Pseudomonas. aeruginosa, two bacteria which are common causes of hospital acquired infections. These were exposure to 3 different light outputs from the prototype and the surviving bacteria enumerated. Results showed that the mixed light output provided a much better CRI and light output under which to work. Also, the light output containing 405 nm light provided an antimicrobial effect, with decontamination of 103 CFUml-1 populations of both bacterial species. The other light content (red, yellow, green) had no beneficial or adverse effects on the antimicrobial properties of the 405nm light. The results suggest that with further development, it could be possible to produce an antimicrobial blended white light containing pulsed 405nm light that could supplement or even replace standard white lighting in certain environments.

Photosynthetically supplemental lighting for vegetable crop production with super-bright laser diode

NASA Astrophysics Data System (ADS)

Hu, Yongguang; Li, Pingping; Shi, Jintong

2007-02-01

Although many artificial light sources like high-pressure sodium lamp, metal halide lamp, fluorescent lamp and so on are commonly used in horticulture, they are not widely applied because of the disadvantages of unreasonable spectra, high cost and complex control. Recently new light sources of light-emitting diode (LED) and laser diode (LD) are becoming more and more popular in the field of display and illumination with the improvement of material and manufacturing, long life-span and increasingly low cost. A new type of super-bright red LD (BL650, central wavelength is 650 nm) was selected to make up of the supplemental lighting panel, on which LDs were distributed with regular hexagon array. Drive circuit was designed to power it and adjust light intensity. System performance including temperature rise and light intensity distribution under different vertical/horizontal distances were tested. Photosynthesis of sweet pepper and eggplant leaf under LD was measured with LI-6400 to show the supplemental lighting effects. The results show that LD system can supply the maximum light intensity of 180 μmol/m2 •s at the distance of 50 mm below the panel and the temperature rise is little within 1 °C. Net photosynthetic rate became faster when LD system increased light intensity. Compared with sunlight and LED supplemental lighting system, LD's promotion on photosynthesis is in the middle. Thus it is feasible for LD light source to supplement light for vegetable crops. Further study would focus on the integration of LD and other artificial light sources.

Supplemental blue LED lighting array to improve the signal quality in hyperspectral imaging of plants.

PubMed

Mahlein, Anne-Katrin; Hammersley, Simon; Oerke, Erich-Christian; Dehne, Heinz-Wilhelm; Goldbach, Heiner; Grieve, Bruce

2015-06-01

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.

LED lighting efficacy: Status and directions

DOE PAGES

Morgan Pattison, Paul; Hansen, Monica; Tsao, Jeffrey Y.

2017-12-28

A monumental shift from conventional lighting technologies (incandescent, fluorescent, high intensity discharge) to LED lighting is currently transpiring. The primary driver for this shift has been energy and associated cost savings. LED lighting is now more efficacious than any of the conventional lighting technologies with room to still improve. Near term, phosphor converted LED packages have the potential for efficacy improvement from 160 lm/W to 255 lm/W. Longer term, color-mixed LED packages have the potential for efficacy levels conceivably as high as 330 lm/W, though reaching these performance levels requires breakthroughs in green and amber LED efficiency. LED package efficacymore » sets the upper limit to luminaire efficacy, with the luminaire containing its own efficacy loss channels. In this paper, based on analyses performed through the U.S. Department of Energy Solid State Lighting Program, various LED and luminaire loss channels are elucidated, and critical areas for improvement identified. Beyond massive energy savings, LED technology enables a host of new applications and added value not possible or economical with previous lighting technologies. These include connected lighting, lighting tailored for human physiological responses, horticultural lighting, and ecologically conscious lighting. Finally, none of these new applications would be viable if not for the high efficacies that have been achieved, and are themselves just the beginning of what LED lighting can do.« less

LED lighting efficacy: Status and directions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morgan Pattison, Paul; Hansen, Monica; Tsao, Jeffrey Y.

A monumental shift from conventional lighting technologies (incandescent, fluorescent, high intensity discharge) to LED lighting is currently transpiring. The primary driver for this shift has been energy and associated cost savings. LED lighting is now more efficacious than any of the conventional lighting technologies with room to still improve. Near term, phosphor converted LED packages have the potential for efficacy improvement from 160 lm/W to 255 lm/W. Longer term, color-mixed LED packages have the potential for efficacy levels conceivably as high as 330 lm/W, though reaching these performance levels requires breakthroughs in green and amber LED efficiency. LED package efficacymore » sets the upper limit to luminaire efficacy, with the luminaire containing its own efficacy loss channels. In this paper, based on analyses performed through the U.S. Department of Energy Solid State Lighting Program, various LED and luminaire loss channels are elucidated, and critical areas for improvement identified. Beyond massive energy savings, LED technology enables a host of new applications and added value not possible or economical with previous lighting technologies. These include connected lighting, lighting tailored for human physiological responses, horticultural lighting, and ecologically conscious lighting. Finally, none of these new applications would be viable if not for the high efficacies that have been achieved, and are themselves just the beginning of what LED lighting can do.« less

Enhanced optical output power of blue light-emitting diodes with quasi-aligned gold nanoparticles.

PubMed

Jin, Yuanhao; Li, Qunqing; Li, Guanhong; Chen, Mo; Liu, Junku; Zou, Yuan; Jiang, Kaili; Fan, Shoushan

2014-01-06

The output power of the light from GaN-based light-emitting diodes (LEDs) was enhanced by fabricating gold (Au) nanoparticles on the surface of p-GaN. Quasi-aligned Au nanoparticle arrays were prepared by depositing Au thin film on an aligned suspended carbon nanotube thin film surface and then putting the Au-CNT system on the surface of p-GaN and thermally annealing the sample. The size and position of the Au nanoparticles were confined by the carbon nanotube framework, and no other additional residual Au was distributed on the surface of the p-GaN substrate. The output power of the light from the LEDs with Au nanoparticles was enhanced by 55.3% for an injected current of 100 mA with the electrical property unchanged compared with the conventional planar LEDs. The enhancement may originate from the surface plasmon effect and scattering effect of the Au nanoparticles.

White Light–Emitting Diodes (LEDs) at Domestic Lighting Levels and Retinal Injury in a Rat Model

PubMed Central

Shang, Yu-Man; Wang, Gen-Shuh; Sliney, David; Lee, Li-Ling

2013-01-01

Background: Light-emitting diodes (LEDs) deliver higher levels of blue light to the retina than do conventional domestic light sources. Chronic exposure to high-intensity light (2,000–10,000 lux) has previously been found to result in light-induced retinal injury, but chronic exposure to relatively low-intensity (750 lux) light has not been previously assessed with LEDs in a rodent model. Objective: We examined LED-induced retinal neuronal cell damage in the Sprague-Dawley rat using functional, histological, and biochemical measurements. Methods: We used blue LEDs (460 nm) and full-spectrum white LEDs, coupled with matching compact fluorescent lights, for exposures. Pathological examinations included electroretinogram, hematoxylin and eosin (H&E) staining, immunohistochemistry (IHC), and transmission electron microscopy (TEM). We also measured free radical production in the retina to determine the oxidative stress level. Results: H&E staining and TEM revealed apoptosis and necrosis of photoreceptors, which indicated blue-light induced photochemical injury of the retina. Free radical production in the retina was increased in LED-exposed groups. IHC staining demonstrated that oxidative stress was associated with retinal injury. Although we found serious retinal light injury in LED groups, the compact fluorescent lamp (CFL) groups showed moderate to mild injury. Conclusion: Our results raise questions about adverse effects on the retina from chronic exposure to LED light compared with other light sources that have less blue light. Thus, we suggest a precautionary approach with regard to the use of blue-rich “white” LEDs for general lighting. Citation: Shang YM, Wang GS, Sliney D, Yang CH, Lee LL. 2014. White light–emitting diodes (LEDs) at domestic lighting levels and retinal injury in a rat model. Environ Health Perspect 122:269–276; http://dx.doi.org/10.1289/ehp.1307294 PMID:24362357

Advanced Solid State Lighting for Human Evaluation Project

NASA Technical Reports Server (NTRS)

Zeitlin, Nancy; Holbert, Eirik

2015-01-01

Lighting intensity and color have a significant impact on human circadian rhythms. Advanced solid state lighting was developed for the Advanced Exploration System (AES) Deep Space Habitat(DSH) concept demonstrator. The latest generation of assemblies using the latest commercially available LED lights were designed for use in the Bigelow Aerospace Environmental Control and Life Support System (ECLSS) simulator and the University of Hawaii's Hawaii Space Exploration Analog and Simulation (Hi-SEAS) habitat. Agreements with both these organizations will allow the government to receive feedback on the lights and lighting algorithms from long term human interaction.

4.5-Gb/s RGB-LED based WDM visible light communication system employing CAP modulation and RLS based adaptive equalization.

PubMed

Wang, Yiguang; Huang, Xingxing; Tao, Li; Shi, Jianyang; Chi, Nan

2015-05-18

Inter-symbol interference (ISI) is one of the key problems that seriously limit transmission data rate in high-speed VLC systems. To eliminate ISI and further improve the system performance, series of equalization schemes have been widely investigated. As an adaptive algorithm commonly used in wireless communication, RLS is also suitable for visible light communication due to its quick convergence and better performance. In this paper, for the first time we experimentally demonstrate a high-speed RGB-LED based WDM VLC system employing carrier-less amplitude and phase (CAP) modulation and recursive least square (RLS) based adaptive equalization. An aggregate data rate of 4.5Gb/s is successfully achieved over 1.5-m indoor free space transmission with the bit error rate (BER) below the 7% forward error correction (FEC) limit of 3.8x10(-3). To the best of our knowledge, this is the highest data rate ever achieved in RGB-LED based VLC systems.

Comparative effectiveness of light emitting diodes (LEDs) and Lasers in near infrared photoimmunotherapy

PubMed Central

Sato, Kazuhide; Watanabe, Rira; Hanaoka, Hirofumi; Nakajima, Takahito; Choyke, Peter L.; Kobayashi, Hisataka

2016-01-01

Near infrared photoimmunotherapy (NIR-PIT) is a new cancer treatment that combines the specificity of antibodies for targeting tumors with the toxicity induced by photosensitizers after exposure to near infrared (NIR) light. Herein we compare two NIR-light sources; light emitting diodes (LEDs) and Lasers, for their effectiveness in NIR-PIT. A photosensitizer, IRDye-700DX, conjugated to panitumumab (pan-IR700), was incubated with EGFR-expressing A431 and MDA-MB-468-luc cells. NIR-light was provided by LEDs or Lasers at the same light dose. Laser-light produced more cytotoxicity and greater reductions in IR700-fluorescence intensity than LED-light. Laser-light also produced more cytotoxicity in vivo in both cell lines. Assessment of super-enhanced permeability and retention (SUPR) effects were stronger with Laser than LED. These results suggest that Laser-light produced significantly more cytotoxic effects compared to LEDs. Although LED is less expensive, Laser-light produces superior results in NIR-PIT. PMID:26885688

Comparative effectiveness of light emitting diodes (LEDs) and Lasers in near infrared photoimmunotherapy.

PubMed

Sato, Kazuhide; Watanabe, Rira; Hanaoka, Hirofumi; Nakajima, Takahito; Choyke, Peter L; Kobayashi, Hisataka

2016-03-22

Near infrared photoimmunotherapy (NIR-PIT) is a new cancer treatment that combines the specificity of antibodies for targeting tumors with the toxicity induced by photosensitizers after exposure to near infrared (NIR) light. Herein we compare two NIR-light sources; light emitting diodes (LEDs) and Lasers, for their effectiveness in NIR-PIT. A photosensitizer, IRDye-700DX, conjugated to panitumumab (pan-IR700), was incubated with EGFR-expressing A431 and MDA-MB-468-luc cells. NIR-light was provided by LEDs or Lasers at the same light dose. Laser-light produced more cytotoxicity and greater reductions in IR700-fluorescence intensity than LED-light. Laser-light also produced more cytotoxicity in vivo in both cell lines. Assessment of super-enhanced permeability and retention (SUPR) effects were stronger with Laser than LED. These results suggest that Laser-light produced significantly more cytotoxic effects compared to LEDs. Although LED is less expensive, Laser-light produces superior results in NIR-PIT.

LED Lighting Facts® Program Supports Accuracy in SSL Product Information

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

Fact sheet that provides a summary of LED Lighting Facts, a program to assure that LED lighting is accurately represented in the marketplace, illustrated by the LED Lighting Facts label to disclose product performance data.

Indoor visible light communication localization system utilizing received signal strength indication technique and trilateration method

NASA Astrophysics Data System (ADS)

Mousa, Farag I. K.; Almaadeed, Noor; Busawon, Krishna; Bouridane, Ahmed; Binns, Richard; Elliot, Ian

2018-01-01

Visible light communication (VLC) based on light-emitting diodes (LEDs) technology not only provides higher data rate for indoor wireless communications and offering room illumination but also has the potential for indoor localization. VLC-based indoor positioning using the received optical power levels from emitting LEDs is investigated. We consider both scenarios of line-of-sight (LOS) and LOS with non-LOS (LOSNLOS) positioning. The performance of the proposed system is evaluated under both noisy and noiseless channel as is the impact of different location codes on positioning error. The analytical model of the system with noise and the corresponding numerical evaluation for a range of signal-to-noise ratio (SNR) are presented. The results show that an accuracy of <10 cm on average is achievable at an SNR>12 dB.

Meeting the challenges of developing LED-based projection displays

NASA Astrophysics Data System (ADS)

Geißler, Enrico

2006-04-01

The main challenge in developing a LED-based projection system is to meet the brightness requirements of the market. Therefore a balanced combination of optical, electrical and thermal parameters must be reached to achieve these performance and cost targets. This paper describes the system design methodology for a digital micromirror display (DMD) based optical engine using LEDs as the light source, starting at the basic physical and geometrical parameters of the DMD and other optical elements through characterization of the LEDs to optimizing the system performance by determining optimal driving conditions. LEDs have a luminous flux density which is just at the threshold of acceptance in projection systems and thus only a fully optimized optical system with a matched set of LEDs can be used. This work resulted in two projection engines, one for a compact pocket projector and the other for a rear projection television, both of which are currently in commercialization.

Evidence-Based Recommendations for Optimizing Light in Day-to-Day Spaceflight Operations

NASA Technical Reports Server (NTRS)

Whitmire, Alexandra; Leveton, Lauren; Barger, Laura; Clark, Toni; Bollweg, Laura; Ohnesorge, Kristine; Brainard, George

2015-01-01

NASA Behavioral Health and Performance Element (BHP) personnel have previously reported on efforts to transition evidence-based recommendations for a flexible lighting system on the International Space Station (ISS). Based on these recommendations, beginning in 2016 the ISS will replace the current fluorescent-based lights with an LED-based system to optimize visual performance, facilitate circadian alignment, promote sleep, and hasten schedule shifting. Additional efforts related to lighting countermeasures in spaceflight operations have also been underway. As an example, a recent BHP research study led by investigators at Harvard Medical School and Brigham and Women's Hospital, evaluated the acceptability, feasibility, and effectiveness of blue-enriched light exposure during exercise breaks for flight controllers working the overnight shift in the Mission Control Center (MCC) at NASA Johnson Space Center. This effort, along with published laboratory studies that have demonstrated the effectiveness of appropriately timed light for promoting alertness, served as an impetus for new light options, and educational protocols for flight controllers. In addition, a separate set of guidelines related to the light emitted from electronic devices, were provided to the Astronaut Office this past year. These guidelines were based on an assessment led by NASA's Lighting Environment Test Facility that included measuring the spectral power distribution, irradiance, and radiance of light emitted from ISS-grade laptops and I-Pads, as well as Android devices. Evaluations were conducted with and without the use of off-the-shelf screen filters as well as a software application that touts minimizing the short-wave length of the visible light spectrum. This presentation will focus on the transition for operations process related to lighting countermeasures in the MCC, as well as the evidence to support recommendations for optimal use of laptops, I-Pads, and Android devices during all phases of spaceflight operations.

Improved InGaN LED System Efficacy and Cost via Droop Reduction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wildeson, Isaac

Efficiency droop is a non-thermal process intrinsic to indium gallium nitride light emitting diodes (LEDs) in which the external quantum efficiency (EQE) decreases with increasing drive current density. Mitigating droop would allow one to reduce the size of LEDs driven at a given current or to drive LEDs of given size at higher current while maintaining high efficiencies. In other words, droop mitigation can lead to significant gains in light output per dollar and/or light output per watt of input power. This project set an EQE improvement goal at high drive current density which was to be attained by improvingmore » the LED active region design and growth process following a droop mitigation strategy. The interactions between LED active region design parameters and efficiency droop were studied by modeling and experiments. The crystal defects that tend to form in more complex LED designs intended to mitigate droop were studied with advanced characterization methods that provided insight into the structural and electronic properties of the material. This insight was applied to improve the epitaxy process both in terms of active region design and optimization of growth parameters. The final project goals were achieved on schedule and an epitaxy process leading to LEDs with EQE exceeding the project target was demonstrated.« less

Spectral design flexibility of LED brings better life

NASA Astrophysics Data System (ADS)

Ou, Haiyan; Corell, Dennis; Ou, Yiyu; Poulsen, Peter B.; Dam-Hansen, Carsten; Petersen, Paul-Michael

2012-03-01

Light-emitting diodes (LEDs) are penetrating into the huge market of general lighting because they are energy saving and environmentally friendly. The big advantage of LED light sources, compared to traditional incandescent lamps and fluorescent light tubes, is the flexible spectral design to make white light using different color mixing schemes. The spectral design flexibility of white LED light sources will promote them for novel applications to improve the life quality of human beings. As an initial exploration to make use of the spectral design flexibility, we present an example: 'no blue' white LED light source for sufferers of disease Porphyria. An LED light source prototype, made of high brightness commercial LEDs applying an optical filter, was tested by a patient suffering from Porphyria. Preliminary results have shown that the sufferer could withstand the light source for much longer time than the standard light source. At last future perspectives on spectral design flexibility of LED light sources improving human being's life will be discussed, with focus on the light and health. The good health is ensured by the spectrum optimized so that vital hormones (melatonin and serotonin) are produced during times when they support human daily rhythm.

Aging characteristics of blue InGaN micro-light emitting diodes at an extremely high current density of 3.5 kA cm-2

NASA Astrophysics Data System (ADS)

Tian, Pengfei; Althumali, Ahmad; Gu, Erdan; Watson, Ian M.; Dawson, Martin D.; Liu, Ran

2016-04-01

The aging characteristics of blue InGaN micro-light emitting diodes (micro-LEDs) with different sizes have been studied at an extremely high current density 3.5 kA cm-2 for emerging micro-LED applications including visible light communication (VLC), micro-LED pumped organic lasers and optogenetics. The light output power of micro-LEDs first increases and then decreases due to the competition of Mg activation in p-GaN layer and defect generation in the active region. The smaller micro-LEDs show less light output power degradation compared with larger micro-LEDs, which is attributed to the lower junction temperature of smaller micro-LEDs. It is found that the high current density without additional junction temperature cannot induce significant micro-LED degradation at room temperature but the combination of the high current density and high junction temperature leads to strong degradation. Furthermore, the cluster LEDs, composed of a micro-LED array, have been developed with both high light output power and less light output degradation for micro-LED applications in solid state lighting and VLC.

Improving spinach, radish, and lettuce growth under red light-emitting diodes (LEDs) with blue light supplementation

NASA Technical Reports Server (NTRS)

Yorio, N. C.; Goins, G. D.; Kagie, H. R.; Wheeler, R. M.; Sager, J. C.

2001-01-01

Radish (Raphanus sativus L. cv. Cherriette), lettuce (Lactuca sativa L. cv. Waldmann's Green), and spinach (Spinacea oleracea L. cv. Nordic IV) plants were grown under 660-nm red light-emitting diodes (LEDs) and were compared at equal photosynthetic photon flux (PPF) with either plants grown under cool-white fluorescent lamps (CWF) or red LEDs supplemented with 10% (30 micromoles m-2 s-1) blue light (400-500 nm) from blue fluorescent (BF) lamps. At 21 days after planting (DAP), leaf photosynthetic rates and stomatal conductance were greater for plants grown under CWF light than for those grown under red LEDs, with or without supplemental blue light. At harvest (21 DAP), total dry-weight accumulation was significantly lower for all species tested when grown under red LEDs alone than when grown under CWF light or red LEDs + 10% BF light. Moreover, total dry weight for radish and spinach was significantly lower under red LEDs + 10% BF than under CWF light, suggesting that addition of blue light to the red LEDs was still insufficient for achieving maximal growth for these crops.

Optical design of a LED searchlight system

NASA Astrophysics Data System (ADS)

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.

Relationship between the change of ethological status and concentration of certain cytokines in blood in experimental desynchronosis under led lighting.

PubMed

Osikov, M V; Ogneva, O I

2016-01-01

Changing the natural rhythm of day and night leads to the development of DS, disruption of coordinated muscular activity, adequate behavioral activity, a decrease of attention in the performance of night work by experts in various fields. Changes ethological status may potentiate or weaken the changes in the indices of immune status, contribute to the formation of allostatic load at desynchronosis. To investigate the relationship between changes ethological status and concentration of certain cytokines in peripheral blood in experimental desynchronosis under LED lighting. The study was performed on 158 adult guinea pigs, which were randomly assigned into 2 groups: 1 group- animals in the conditions of standard fixed (12 h light / 12 h dark) LED lighting (SFSDO); 2 group- animals with jet lag in terms of LED lighting (DESSDO). Light desynchronosis created by keeping animals at clock coverage for 30 days. Behavioral activity was studied in the test «open field» cognitive function was assessed using aqueous «labyrinth» Morris. By ELISA was determined on the apparatus in the peripheral blood concentration of interleukin - 4 (IL-4), interferon-gamma (IFN-g), melatonin, cortisol via specific for guinea pig test systems. It was found that in animals of DS in terms of LED lighting in the dynamics of 10-30 days of observation show signs of anxiety, depression orienting-exploratory behavior, reduce the long-term memory and learning ability, spatial orientation disorders. It found that when a jet lag LED lighting conditions for 10 days, 20 days and 30 days in peripheral blood melatonin concentration decreases, the concentration of cortisol rises. In peripheral blood decreased IL-4 concentrations of 20 and 30 days, reducing the concentration of IFN-g at 30 days. Based on the results of correlation analysis, ethological change status and progress of cognitive function with a decrease in the blood concentration of IL-4 and IFN-g, the concentration of melatonin increase cortisol levels. The results indicate that in experimental conditions in desynchronosis LED lighting changes ethological status are associated with the progression of immune status changes.

Light emitting diode excitation emission matrix fluorescence spectroscopy.

PubMed

Hart, Sean J; JiJi, Renée D

2002-12-01

An excitation emission matrix (EEM) fluorescence instrument has been developed using a linear array of light emitting diodes (LED). The wavelengths covered extend from the upper UV through the visible spectrum: 370-640 nm. Using an LED array to excite fluorescence emission at multiple excitation wavelengths is a low-cost alternative to an expensive high power lamp and imaging spectrograph. The LED-EEM system is a departure from other EEM spectroscopy systems in that LEDs often have broad excitation ranges which may overlap with neighboring channels. The LED array can be considered a hybrid between a spectroscopic and sensor system, as the broad LED excitation range produces a partially selective optical measurement. The instrument has been tested and characterized using fluorescent dyes: limits of detection (LOD) for 9,10-bis(phenylethynyl)-anthracene and rhodamine B were in the mid parts-per-trillion range; detection limits for the other compounds were in the low parts-per-billion range (< 5 ppb). The LED-EEMs were analyzed using parallel factor analysis (PARAFAC), which allowed the mathematical resolution of the individual contributions of the mono- and dianion fluorescein tautomers a priori. Correct identification and quantitation of six fluorescent dyes in two to six component mixtures (concentrations between 12.5 and 500 ppb) has been achieved with root mean squared errors of prediction (RMSEP) of less than 4.0 ppb for all components.

Simple and cost-effective hardware and software for functional brain mapping using intrinsic optical signal imaging.

PubMed

Harrison, Thomas C; Sigler, Albrecht; Murphy, Timothy H

2009-09-15

We describe a simple and low-cost system for intrinsic optical signal (IOS) imaging using stable LED light sources, basic microscopes, and commonly available CCD cameras. IOS imaging measures activity-dependent changes in the light reflectance of brain tissue, and can be performed with a minimum of specialized equipment. Our system uses LED ring lights that can be mounted on standard microscope objectives or video lenses to provide a homogeneous and stable light source, with less than 0.003% fluctuation across images averaged from 40 trials. We describe the equipment and surgical techniques necessary for both acute and chronic mouse preparations, and provide software that can create maps of sensory representations from images captured by inexpensive 8-bit cameras or by 12-bit cameras. The IOS imaging system can be adapted to commercial upright microscopes or custom macroscopes, eliminating the need for dedicated equipment or complex optical paths. This method can be combined with parallel high resolution imaging techniques such as two-photon microscopy.

Piezo-Phototronic Effect Controlled Dual-Channel Visible light Communication (PVLC) Using InGaN/GaN Multiquantum Well Nanopillars.

PubMed

Du, Chunhua; Jiang, Chunyan; Zuo, Peng; Huang, Xin; Pu, Xiong; Zhao, Zhenfu; Zhou, Yongli; Li, Linxuan; Chen, Hong; Hu, Weiguo; Wang, Zhong Lin

2015-12-02

Visible light communication (VLC) simultaneously provides illumination and communication via light emitting diodes (LEDs). Keeping a low bit error rate is essential to communication quality, and holding a stable brightness level is pivotal for illumination function. For the first time, a piezo-phototronic effect controlled visible light communication (PVLC) system based on InGaN/GaN multiquantum wells nanopillars is demonstrated, in which the information is coded by mechanical straining. This approach of force coding is also instrumental to avoid LED blinks, which has less impact on illumination and is much safer to eyes than electrical on/off VLC. The two-channel transmission mode of the system here shows great superiority in error self-validation and error self-elimination in comparison to VLC. This two-channel PVLC system provides a suitable way to carry out noncontact, reliable communication under complex circumstances. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Compact light-emitting diode optical fiber immobilized TiO2 reactor for photocatalytic water treatment.

PubMed

O'Neal Tugaoen, Heather; Garcia-Segura, Sergi; Hristovski, Kiril; Westerhoff, Paul

2018-02-01

A key barrier to implementing photocatalysis is delivering light to photocatalysts that are in contact with aqueous pollutants. Slurry photocatalyst systems suffer from poor light penetration and require post-treatment to separate the catalyst. The alternative is to deposit photocatalysts on fixed films and deliver light onto the surface or the backside of the attached catalysts. In this study, TiO 2 -coated quartz optical fibers were coupled to light emitting diodes (OF/LED) to improve in situ light delivery. Design factors and mechanisms studied for OF/LEDs in a flow-through reactor included: (i) the influence of number of LED sources coupled to fibers and (ii) the use of multiple optical fibers bundled to a single LED. The light delivery mechanism from the optical fibers into the TiO 2 coatings is thoroughly discussed. To demonstrate influence of design variables, experiments were conducted in the reactor using the chlorinated pollutant para-chlorobenzoic acid (pCBA). From the degradation kinetics of pCBA, the quantum efficiencies (Φ) of oxidation and electrical energies per order (E EO ) were determined. The use of TiO 2 coated optical fiber bundles reduced the energy requirements to deliver photons and increased available surface area, which improved Φ and enhanced oxidative pollutant removal performance (E EO ). Copyright © 2017 Elsevier B.V. All rights reserved.

Portable LED-induced autofluorescence imager with a probe of L shape for oral cancer diagnosis

NASA Astrophysics Data System (ADS)

Huang, Ting-Wei; Lee, Yu-Cheng; Cheng, Nai-Lun; Yan, Yung-Jhe; Chiang, Hou-Chi; Chiou, Jin-Chern; Mang, Ou-Yang

2015-08-01

The difference of spectral distribution between lesions of epithelial cells and normal cells after excited fluorescence is one of methods for the cancer diagnosis. In our previous work, we developed a portable LED Induced autofluorescence (LIAF) imager contained the multiple wavelength of LED excitation light and multiple filters to capture ex-vivo oral tissue autofluorescence images. Our portable system for detection of oral cancer has a probe in front of the lens for fixing the object distance. The shape of the probe is cone, and it is not convenient for doctor to capture the oral image under an appropriate view angle in front of the probe. Therefore, a probe of L shape containing a mirror is proposed for doctors to capture the images with the right angles, and the subjects do not need to open their mouse constrainedly. Besides, a glass plate is placed in probe to prevent the liquid entering in the body, but the light reflected from the glass plate directly causes the light spots inside the images. We set the glass plate in front of LED to avoiding the light spots. When the distance between the glasses plate and the LED model plane is less than the critical value, then we can prevent the light spots caused from the glasses plate. The experiments show that the image captured with the new probe that the glasses plate placed in the back-end of the probe has no light spots inside the image.

LED Systems Target Plant Growth

NASA Technical Reports Server (NTRS)

2010-01-01

To help develop technologies for growing edible biomass (food crops) in space, Kennedy Space Center partnered with Orbital Technologies Corporation (ORBITEC), of Madison, Wisconsin, through the Small Business Innovation Research (SBIR) program. One result of this research was the High Efficiency Lighting with Integrated Adaptive Control (HELIAC) system, components of which have been incorporated into a variety of agricultural greenhouse and consumer aquarium lighting features. The new lighting systems can be adapted to a specific plant species during a specific growth stage, allowing maximum efficiency in light absorption by all available photosynthetic tissues.

Development and testing of a homogenous multi-wavelength LED light source

NASA Astrophysics Data System (ADS)

Bolton, Frank J.; Bernat, Amir; Jacques, Steven L.; Levitz, David

2017-03-01

Multispectral imaging of human tissue is a powerful method that allows for quantify scattering and absorption parameters of the tissue and differentiate tissue types or identify pathology. This method requires imaging at multiple wavelengths and then fitting the measured data to a model based on light transport theory. Earlier, a mobile phone based multi-spectral imaging system was developed to image the uterine cervix from the colposcopy geometry, outside the patient's body at a distance of 200-300 mm. Such imaging of a distance object has inherent challenges, as bright and homogenous illumination is required. Several solutions addressing this problem were developed, with varied degrees of success. In this paper, several multi-spectral illumination setups were developed and tested for brightness and uniformity. All setups were specifically designed with low cost in mind, utilizing a printed circuit board with surface-mounted LEDs. The three setups include: LEDs illuminating the target directly, LEDs illuminating focused by a 3D printed miniature lens array, and LEDs coupled to a mixing lens and focusing optical system. In order to compare the illumination uniformity and intensity performance two experiments were performed. Test results are presented, and various tradeoffs between the three system configurations are discussed. Test results are presented, and various tradeoffs between the three system configurations are discussed.

Adaptive 84.44-190 Mbit/s phosphor-LED wireless communication utilizing no blue filter at practical transmission distance.

PubMed

Yeh, C H; Chow, C W; Chen, H Y; Chen, J; Liu, Y L

2014-04-21

We propose and experimentally demonstrate a white-light phosphor-LED visible light communication (VLC) system with an adaptive 84.44 to 190 Mbit/s 16 quadrature-amplitude-modulation (QAM) orthogonal-frequency-division-multiplexing (OFDM) signal utilizing bit-loading method. Here, the optimal analogy pre-equalization design is performed at LED transmitter (Tx) side and no blue filter is used at the Rx side. Hence, the ~1 MHz modulation bandwidth of phosphor-LED could be extended to 30 MHz. In addition, the measured bit error rates (BERs) of < 3.8 × 10(-3) [forward error correction (FEC) threshold] at different measured data rates can be achieved at practical transmission distances of 0.75 to 2 m.

Modeling of photoluminescence in laser-based lighting systems

NASA Astrophysics Data System (ADS)

Chatzizyrli, Elisavet; Tinne, Nadine; Lachmayer, Roland; Neumann, Jörg; Kracht, Dietmar

2017-12-01

The development of laser-based lighting systems has been the latest step towards a revolution in illumination technology brought about by solid-state lighting. Laser-activated remote phosphor systems produce white light sources with significantly higher luminance than LEDs. The weak point of such systems is often considered to be the conversion element. The high-intensity exciting laser beam in combination with the limited thermal conductivity of ceramic phosphor materials leads to thermal quenching, the phenomenon in which the emission efficiency decreases as temperature rises. For this reason, the aim of the presented study is the modeling of remote phosphor systems in order to investigate their thermal limitations and to calculate the parameters for optimizing the efficiency of such systems. The common approach to simulate remote phosphor systems utilizes a combination of different tools such as ray tracing algorithms and wave optics tools for describing the incident and converted light, whereas the modeling of the conversion process itself, i.e. photoluminescence, in most cases is circumvented by using the absorption and emission spectra of the phosphor material. In this study, we describe the processes involved in luminescence quantum-mechanically using the single-configurational-coordinate diagram as well as the Franck-Condon principle and propose a simulation model that incorporates the temperature dependence of these processes. Following an increasing awareness of climate change and environmental issues, the development of ecologically friendly lighting systems featuring low power consumption and high luminous efficiency is imperative more than ever. The better understanding of laser-based lighting systems is an important step towards that aim as they may improve on LEDs in the near future.

On-chip integration of suspended InGaN/GaN multiple-quantum-well devices with versatile functionalities.

PubMed

Cai, Wei; Yang, Yongchao; Gao, Xumin; Yuan, Jialei; Yuan, Wei; Zhu, Hongbo; Wang, Yongjin

2016-03-21

We propose, fabricate and demonstrate on-chip photonic integration of suspended InGaN/GaN multiple quantum wells (MQWs) devices on the GaN-on-silicon platform. Both silicon removal and back wafer etching are conducted to obtain membrane-type devices, and suspended waveguides are used for the connection between p-n junction InGaN/GaN MQWs devices. As an in-plane data transmission system, the middle p-n junction InGaN/GaN MQWs device is used as a light emitting diode (LED) to deliver signals by modulating the intensity of the emitted light, and the other two devices act as photodetectors (PDs) to sense the light guided by the suspended waveguide and convert the photons into electrons, achieving 1 × 2 in-plane information transmission via visible light. Correspondingly, the three devices can function as independent PDs to realize multiple receivers for free space visible light communication. Further, the on-chip photonic platform can be used as an active electro-optical sensing system when the middle device acts as a PD and the other two devices serve as LEDs. The experimental results show that the auxiliary LED sources can enhance the amplitude of the induced photocurrent.

Long-range high-speed visible light communication system over 100-m outdoor transmission utilizing receiver diversity technology

NASA Astrophysics Data System (ADS)

Wang, Yiguang; Huang, Xingxing; Shi, Jianyang; Wang, Yuan-quan; Chi, Nan

2016-05-01

Visible light communication (VLC) has no doubt become a promising candidate for future wireless communications due to the increasing trends in the usage of light-emitting diodes (LEDs). In addition to indoor high-speed wireless access and positioning applications, VLC usage in outdoor scenarios, such as vehicle networks and intelligent transportation systems, are also attracting significant interest. However, the complex outdoor environment and ambient noise are the key challenges for long-range high-speed VLC outdoor applications. To improve system performance and transmission distance, we propose to use receiver diversity technology in an outdoor VLC system. Maximal ratio combining-based receiver diversity technology is utilized in two receivers to achieve the maximal signal-to-noise ratio. A 400-Mb/s VLC transmission using a phosphor-based white LED and a 1-Gb/s wavelength division multiplexing VLC transmission using a red-green-blue LED are both successfully achieved over a 100-m outdoor distance with the bit error rate below the 7% forward error correction limit of 3.8×10-3. To the best of our knowledge, this is the highest data rate at 100-m outdoor VLC transmission ever achieved. The experimental results clearly prove the benefit and feasibility of receiver diversity technology for long-range high-speed outdoor VLC systems.

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

NASA Technical Reports Server (NTRS)

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 dye degradation on the slides over time, a temperature-stabilized white light LED was used to illuminate the opposite side of the slides. As the dye degraded, the amount of light from the white light LED transmitted through the slide was monitored with a spectrometer and subsequently analyzed to determine and compare the rate of dye degradation for photocatalytically coated versus uncoated slide surfaces. The long-term stability of the spectrometer/white light LED combination, which required only a single reference spectra to be taken for a time series sequence of several hours, enabled accurate measurements of transmitted light over time. Time series transmission curves were generated and results demonstrated that over time the transmission increased much more rapidly on the coated slides than on the control slides. This experimental configuration and methodology for photocatalytic activity measurement minimizes many external variable effects and allows low light level studies to be performed. This study also compares the advantages of this novel LED light source design to traditional mercury lamp systems and non-LED lamp approaches that have conventionally been used. The methodology and experimental design research summarized in this abstract is partly funded by the Department of Homeland Security, Science and Technology Directorate, and by the NASA Stennis Space Center Innovative Partnerships Program.

On-off keying transmitter design for navigation by visible light communication

NASA Astrophysics Data System (ADS)

Louro, P.; Vieira, M.; Costa, J.; Vieira, M. A.

2018-02-01

White LEDS revolutionized the field of illumination technology mainly due to the energy saving effects. Besides lighting purposes LEDs can also be used in wireless communication systems when integrated in Visible Light Communication (VLC) systems. Indoor positioning for navigation in large buildings is currently under research to overcome the difficulties associated with the use of GPS in such environments. The motivation for this application is also supported by the possibility of taking advantage of an existing lighting and WiFi infrastructure. In this work it is proposed an indoor navigation system based on the use of VLC technology. The proposed system includes trichromatic white LEDs with the red and blue chips modulated at different frequencies and a pinpin photodetector with selective spectral sensitivity. Optoelectronic features of both optical sources and photodetector device are analyzed. The photodetector device consists two pin structures based on a-SiC:H and a-Si:H with geometrical configuration optimized for the detection of short and large wavelengths in the visible range. Its sensitivity is externally tuned by steady state optical bias. The localization algorithm makes use of the Fourier transform to identify the frequencies present in the photocurrent signal and the wavelength filtering properties of the sensor under front and back optical bias to detect the existing red and blue signals. The viability of the system was demonstrated through the implementation of an automatic algorithm to infer the photodetector cardinal direction. A capacitive optoelectronic model supports the experimental results and explains the device operation.

Light-emitting diode street lights reduce last-ditch evasive manoeuvres by moths to bat echolocation calls

PubMed Central

Wakefield, Andrew; Stone, Emma L.; Jones, Gareth; Harris, Stephen

2015-01-01

The light-emitting diode (LED) street light market is expanding globally, and it is important to understand how LED lights affect wildlife populations. We compared evasive flight responses of moths to bat echolocation calls experimentally under LED-lit and -unlit conditions. Significantly, fewer moths performed ‘powerdive’ flight manoeuvres in response to bat calls (feeding buzz sequences from Nyctalus spp.) under an LED street light than in the dark. LED street lights reduce the anti-predator behaviour of moths, shifting the balance in favour of their predators, aerial hawking bats. PMID:26361558

Imaging System and Method for Biomedical Analysis

DTIC Science & Technology

2013-03-11

biological particles and items of interest. Broadly, Padmanabhan et al. utilize the diffraction of a laser light source in flow cytometry to count...spread of light from multiple LED devices over the entire sample surface. Preferably, light source 308 projects a full spectrum white light. Light...for example, red blood cells, white blood cells (which may include lymphocytes which are relatively large and easily detectable), T-helper cells

Effect of LED irradiation on the ripening and nutritional quality of postharvest banana fruit.

PubMed

Huang, Jen-Yi; Xu, Fengying; Zhou, Weibiao

2018-04-24

With the ability to tailor wavelengths necessary to the photosynthetically active radiation spectrum of plant pigments, light-emitting diodes (LEDs) offer vast possibilities in horticultural lighting. The influence of LED light irradiation on major postharvest features of banana was investigated. Mature green bananas were treated daily with selected blue (464-474 nm), green (515-525 nm) and red (617-627 nm) LED lights for 8 days, and compared with non-illuminated control. The positive effect of LED lighting on the acceleration of ripening in bananas was greatest for blue, followed by red and green. Under the irradiation of LED lights, faster peel de-greening and flesh softening, and increased ethylene production and respiration rate in bananas were observed during storage. Furthermore, the accumulations of ascorbic acid, total phenols, and total sugars in banana fruit were enhanced by LED light exposure. LED light treatment can induce the ripening of bananas and improve their quality and nutrition potential. These findings might provide new chemical-free strategies to shorten the time to ripen banana after harvest by using LED light source. This article is protected by copyright. All rights reserved.

Light emitting diodes as a plant lighting source

NASA Technical Reports Server (NTRS)

Bula, R. J.; Tennessen, D. J.; Morrow, R. C.; Tibbitts, T. W.

1994-01-01

Electroluminescence in solid materials is defined as the generation of light by the passage of an electric current through a body of solid material under an applied electric field. A specific type of electroluminescence, first noted in 1923, involves the generation of photons when electrons are passed through a p-n junction of certain solid materials (junction of a n-type semiconductor, an electron donor, and a p-type semiconductor, an electron acceptor). The development of this light emitting semiconductor technology dates back less than 30 years. During this period of time, the LED has evolved from a rare and expensive light generating device to one of the most widely used electronic components. A number of LED characteristics are of considerable importance in selecting a light source for plant lighting in a controlled environment facility. Of particular importance is the characteristic that light is generated by an LED at a rate far greater than the corresponding thermal radiation predicted by the bulk temperature of the device as defined by Plank's radiation law. This is in sharp contrast to other light sources, such as an incandescent or high intensity discharge lamp. A plant lighting system for controlled environments must provide plants with an adequate flux of photosynthetically active radiation, plus providing photons in the spectral regions that are involved in the photomorphogenic and phototropic responses that result in normal plant growth and development. Use of light sources that emit photons over a broad spectral range generally meet these two lighting requirements. Since the LED's emit over specific spectral regions, they must be carefully selected so that the levels of photsynthetically active and photomorphogenic and phototropic radiation meet these plant requirements.

Effects of LED-backlit computer screen and emotional selfregulation on human melatonin production.

PubMed

Sroykham, Watchara; Wongsawat, Yodchanan

2013-01-01

Melatonin is a circadian hormone transmitted via suprachiasmatic nucleus (SCN) in the hypothalamus and sympathetic nervous system to the pineal gland. It is a hormone necessary to many human functions such as immune, cardiovascular, neuron and sleep/awake functions. Since melatonin enhancement or suppression is reported to be closely related to the photic information from retina, in this paper, we aim further to study both the lighting condition and the emotional self-regulation in different lighting conditions together with their effects on the production of human melatonin. In this experiment, five participants are in three light exposure conditions by LED backlit computer screen (No light, Red light (∼650nm) and Blue light (∼470nm)) for 30 minute (8-8:30pm), then they are collected saliva both before and after the experiments. After the experiment, the participants are also asked to answer the emotional self-regulation questionnaire of PANAS and BRUMS regarding each light exposure condition. These results show that positive mood mean difference of PANAS between no light and red light is significant with p=0.001. Tension, depression, fatigue, confusion and vigor from BRUMS are not significantly changed while we can observe the significant change in anger mood. Finally, we can also report that the blue light of LED-backlit computer screen significantly suppress melatonin production (91%) more than red light (78%) and no light (44%).

Plant Atrium System for Food Production in NASA's Deep Space Habitat Tests

NASA Technical Reports Server (NTRS)

Massa, Gioia; Simpson, Morgan S.; Newsham, Gerard; Stutte, Gary W.; Wheeler, Raymond M.

2012-01-01

In preparation for future human exploration missions to space, human habitat designs and concepts need to be tested to assess integration issues, power requirements, crew operations, and technology I subsystem performance. One potential subsystem for early habitats is supplemental food production. Fresh foods, such as vegetables and small fruits, could be harvested on a continuous basis to improve the diet and quality of life. The system would need to fit conveniently into the habitat and not interfere with other components or operations. To test this concept, a plant growing "atrium" was designed to surround the lift between the lower and upper modules of the Deep Space Habitat and deployed at NASA DRA TS test site in 2011 and at NASA's JSC in 20I2. With this approach, un-utilized volume provided an area for vegetable growth. For the 20 II test, mizuna, lettuce, basil, radish and sweetpotato plants were grown in trays using commercially available red I blue LED light fixtures. Seedlings were transplanted into the atrium and cared for by the crew. Plants were then harvested two weeks later following completion of the test. In 20I2, mizuna, lettuce, and radish plants were grown similarly but under flat panel banks of white LEDs. In 20 I2, the crew went through plant harvesting, including sanitizing the leafy greens and radishes, which were then consumed. Each test demonstrated successful production of vegetables within a functional hab module. The round red I blue LEDs for the 20Il test lighting cast a purple light in the hab, and were less uniformly distributed over the plant trays. The white LED panels provided broad spectrum light with more uniform distribution. Post-test questionnaires showed that the crew enjoyed tending and consuming the plants, and that the white LED light in 2012 provided welcome extra light for the main hab area.

Light-Emitting Diodes (LED) for Primary Animal Habitat Lighting in Highly Controlled Environments

NASA Technical Reports Server (NTRS)

Winget, C. M.; Syrkin, N.; Heeke, D.; Mele, G.; Holley, D. C.; Dalton, Bonnie P. (Technical Monitor)

1996-01-01

Significant alterations in Biological Clock responses have been reported following sidereal time changes (e.g., Jet-lag), and exposure to microgravity (e.g., daytime sleepiness). Additionally, light reduces circulating melatonin (spectral specificity greatest between 450-500 nm). It was hypothesized that LEDs can replace the current light sources used in zero gravity and terrestrial research laboratories because of their small size, low mass, low energy consumption and long functional life. This report evaluates the capacity of LEDs to entrain the circadian system of rats as judged by measurement of overt behavioral circadian rhythms (activity, feeding, drinking). These data were collected in highly controlled environments similar to the shuttle Animal Enclosure Modules. Two groups were compared: control - animals exposed to standard cool-white fluorescent lights, and test - animals exposed to LEDs with a spectral power distribution matching the fluorescent lights. Gross locomotor activity, feeding and drinking frequencies were continuously monitored and stored at 10 minute intervals. Animals were exposed to the following photoperiods: 28 days of 12L:12D, 19 days of 24L:0D and 16 days of 12L:12D. Light intensities tested varied between 0.1 to 100 lux. Rats received food and water ad libitum, and temperature and humidity were controlled throughout the study. The general health status of all rats was acceptable for each day of this study. No incidents of aggressive behavior were observed. Growth, locomotor activity, food and water consumption were comparable for all groups of animals, i.e, the circadian characteristics of the animals under these conditions were comparable. These results indicate that LED arrays are as effective in maintaining circadian rhythm stability as the commonly used cool-white fluorescent light sources. LEDs with their flexible spectrum, low energy requirements and minimal heat production have advantages for some chronopharmacology studies and for microgravity animal habitats.

Light-emitting device test systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

McCord, Mark; Brodie, Alan; George, James

Light-emitting devices, such as LEDs, are tested using a photometric unit. The photometric unit, which may be an integrating sphere, can measure flux, color, or other properties of the devices. The photometric unit may have a single port or both an inlet and outlet. Light loss through the port, inlet, or outlet can be reduced or calibrated for. These testing systems can provide increased reliability, improved throughput, and/or improved measurement accuracy.

Twin imaging phenomenon of integral imaging.

PubMed

Hu, Juanmei; Lou, Yimin; Wu, Fengmin; Chen, Aixi

2018-05-14

The imaging principles and phenomena of integral imaging technique have been studied in detail using geometrical optics, wave optics, or light filed theory. However, most of the conclusions are only suit for the integral imaging systems using diffused illumination. In this work, a kind of twin imaging phenomenon and mechanism has been observed in a non-diffused illumination reflective integral imaging system. Interactive twin images including a real and a virtual 3D image of one object can be activated in the system. The imaging phenomenon is similar to the conjugate imaging effect of hologram, but it base on the refraction and reflection instead of diffraction. The imaging characteristics and mechanisms different from traditional integral imaging are deduced analytically. Thin film integral imaging systems with 80μm thickness have also been made to verify the imaging phenomenon. Vivid lighting interactive twin 3D images have been realized using a light-emitting diode (LED) light source. When the LED is moving, the twin 3D images are moving synchronously. This interesting phenomenon shows a good application prospect in interactive 3D display, argument reality, and security authentication.

Use of Occupancy Sensors in LED Parking Lot and Garage Applications: Early Experiences

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kinzey, Bruce R.; Myer, Michael; Royer, Michael P.

2012-11-07

Occupancy sensor systems are gaining traction as an effective technological approach to reducing energy use in exterior commercial lighting applications. Done correctly, occupancy sensors can substantially enhance the savings from an already efficient lighting system. However, this technology is confronted by several potential challenges and pitfalls that can leave a significant amount of the prospective savings on the table. This report describes anecdotal experiences from field installations of occupancy sensor controlled light-emitting diode (LED) lighting at two parking structures and two parking lots. The relative levels of success at these installations reflect a marked range of potential outcomes: from anmore » additional 76% in energy savings to virtually no additional savings. Several issues that influenced savings were encountered in these early stage installations and are detailed in the report. Ultimately, care must be taken in the design, selection, and commissioning of a sensor-controlled lighting installation, else the only guaranteed result may be its cost.« less

Effects of wavelength mixing ratio and photoperiod on microalgal biomass and lipid production in a two-phase culture system using LED illumination.

PubMed

Sirisuk, Phunlap; Ra, Chae-Hun; Jeong, Gwi-Taek; Kim, Sung-Koo

2018-04-01

Blue and red light-emitting diodes (LEDs) were used to study the effects of wavelength mixing ratios, photoperiod regimes, and green wavelength stress on Nannochloropsis salina, Isochrysis galbana, and Phaeodactylum tricornutum cell biomass and lipid production. The maximum specific growth rates of I. galbana and P. tricornutum were obtained under a 50:50 mixing ratio of blue and red wavelength LEDs; that of N. salina was obtained under red LED. Maximum cell biomass for N. salina and P. tricornutum was 0.75 and 1.07 g dcw/L, respectively, obtained under a 24:0 h light/dark cycle. However, the maximum I. galbana biomass was 0.89 g dcw/L under an 18:6 h light/dark cycle. The maximum lipid contents for N. salina, I. galbana, and P. tricornutum were 49.4, 63.3 and 62.0% (w/w), respectively, after exposure to green LED. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were obtained 1% in P. tricornutum and 2% in I. galbana. Copyright © 2018 Elsevier Ltd. All rights reserved.

Mobile health-monitoring system through visible light communication.

PubMed

Tan, Yee-Yong; Chung, Wan-Young

2014-01-01

Promising development in the light emitting diode (LED) technology has spurred the interest to adapt LED for both illumination and data transmission. This has fostered the growth of interest in visible light communication (VLC), with on-going research to utilize VLC in various applications. This paper presents a mobile-health monitoring system, where healthcare information such as biomedical signals and patient information are transmitted via the LED lighting. A small and portable receiver module is designed and developed to be attached to the mobile device, providing a seamless monitoring environment. Three different healthcare information including ECG, PPG signals and HL7 text information is transmitted simultaneously, using a single channel VLC. This allows for a more precise and accurate monitoring and diagnosis. The data packet size is carefully designed, to transmit information in a minimal packet error rate. A comprehensive monitoring application is designed and developed through the use of a tablet computer in our study. Monitoring and evaluation such as heart rate and arterial blood pressure measurement can be performed concurrently. Real-time monitoring is demonstrated through experiment, where non-hazardous transmission method can be implemented alongside a portable device for better and safer healthcare service.

Spectral effects of light-emitting diodes on plant growth and development: The importance of green and blue light

NASA Astrophysics Data System (ADS)

Cope, K. R.; Bugbee, B.

2011-12-01

Light-emitting diodes (LEDs) are an emerging technology for plant growth lighting. Due to their narrow spectral output, colored LEDs provide many options for studying the spectral effects of light on plants. Early on, efficient red LEDs were the primary focus of photobiological research; however, subsequent studies have shown that normal plant growth and development cannot be achieved under red light without blue light supplementation. More recent studies have shown that red and blue (RB) LEDs supplemented with green light increase plant dry mass. This is because green light transmits more effectively through the leaf canopy than red and blue light, thus illuminating lower plant leaves and increasing whole-plant photosynthesis. Red, green and blue (RGB) light can be provided by either a conventional white light source (such as fluorescent lights), a combination of RGB LEDs, or from recently developed white LEDs. White LEDs exceed the efficiency of fluorescent lights and have a comparable broad spectrum. As such, they have the potential to replace fluorescent lighting for growth-chamber-based crop production both on Earth and in space. Here we report the results of studies on the effects of three white LED types (warm, neutral and cool) on plant growth and development compared to combinations of RB and RGB LEDs. Plants were grown under two constant light intensities (200 and 500 μmol m-2 s-1). Temperature, environmental conditions and root-zone environment were uniformly maintained across treatments. Phytochrome photoequilbria and red/far-red ratios were similar among treatments and were comparable to conventional fluorescent lights. Blue light had a significant effect on both plant growth (dry mass gain) and development (dry mass partitioning). An increase in the absolute amount (μmol m-2 s-1) of blue light from 0-80 μmol m-2 s-1 resulted in a decrease in stem elongation, independent of the light intensity. However, an increase in the relative amount (%) of blue light caused a decrease in specific leaf area (leaf area per unit leaf mass). As the relative amount of blue light increased, chlorophyll concentration per unit leaf area increased, but chlorophyll concentration per unit leaf mass remained constant. The relative amount of blue light increased total dry mass in some species while it remained constant in others. An increase in the fraction of green light increased dry mass in radish. Overall, white LEDs provided a more uniform spectral distribution, reduced stem elongation and leaf area, and maintained or increased dry mass as compared to RB and RGB LEDs. Cool white LEDs are more electrically efficient than the other two white LEDs and have sufficient blue light for normal plant growth and development at both high and low light intensities. Compared to sunlight, cool white LEDs are perhaps deficient in red light and may therefore benefit from supplementation with red LEDs. Future studies will be conducted to test this hypothesis. These results have significant implication for LADA growth chambers which are currently used for vegetable production on the International Space Station.

Fiber-array based optogenetic prosthetic system for stimulation therapy

NASA Astrophysics Data System (ADS)

Gu, Ling; Cote, Chris; Tejeda, Hector; Mohanty, Samarendra

2012-02-01

Recent advent of optogenetics has enabled activation of genetically-targeted neuronal cells using low intensity blue light with high temporal precision. Since blue light is attenuated rapidly due to scattering and absorption in neural tissue, optogenetic treatment of neurological disorders may require stimulation of specific cell types in multiple regions of the brain. Further, restoration of certain neural functions (vision, and auditory etc) requires accurate spatio-temporal stimulation patterns rather than just precise temporal stimulation. In order to activate multiple regions of the central nervous system in 3D, here, we report development of an optogenetic prosthetic comprising of array of fibers coupled to independently-controllable LEDs. This design avoids direct contact of LEDs with the brain tissue and thus does not require electrical and heat isolation, which can non-specifically stimulate and damage the local brain regions. The intensity, frequency, and duty cycle of light pulses from each fiber in the array was controlled independently using an inhouse developed LabView based program interfaced with a microcontroller driving the individual LEDs. While the temporal profile of the light pulses was controlled by varying the current driving the LED, the beam profile emanating from each fiber tip could be sculpted by microfabrication of the fiber tip. The fiber array was used to stimulate neurons, expressing channelrhodopsin-2, in different locations within the brain or retina. Control of neural activity in the mice cortex, using the fiber-array based prosthetic, is evaluated from recordings made with multi-electrode array (MEA). We also report construction of a μLED array based prosthetic for spatio-temporal stimulation of cortex.

LEDs for solid state lighting and other emerging applications: status, trends, and challenges

NASA Astrophysics Data System (ADS)

Craford, M. George

2005-09-01

LEDs have been commercially available since the 1960's, but in recent years there have been remarkable improvements in performance. These technology developments have enabled the use of LEDs in a variety of colored and white lighting applications. Colored LEDs have already become the technology of choice for traffic signals, much of interior and exterior vehicle lighting, signage of various types often as a replacement for neon, and other areas. LEDs are expected to become the dominant technology for most colored lighting applications. LEDs are beginning to penetrate white lighting markets such as flashlights and localized task lighting. With further improvement LEDs have the potential to become an important technology for large area general illumination. White LED products already have performance of over 30 lumens/watt which is nearly 3x better than incandescents. White LEDs with outputs of more than 100 lumens are already available commercially, and higher power devices can be expected in the near future. LEDs can be used as point sources, or can be used with light guides of various types to provide distributed illumination. Developments that will need to occur for LEDs to be viable for large area general illumination are discussed.

Light colour and intensity alters reproductive/seasonal responses in Japanese quail.

PubMed

Yadav, Suneeta; Chaturvedi, Chandra Mohini

2015-08-01

An extensive literature is available on the photoperiodic responses of avian species but studies on light colour and wavelength from light emitting diode (LED) sources on reproduction are limited. Hence, an experiment was designed to study the effect of different colours and intensities of light on the reproductive responses of Japanese quail. Three-week old quail were exposed to five different light conditions with a long photoperiod (LD 16:8): WT (white fluorescent light 100 lux as control), W LED (white light emitting diode, 30 lux), B LED (blue LED, 30 lux), G LED (green LED, 30 lux) and R-LED (red LED, 30 lux). The cloacal gland size, an indicator of androgenic activity, was monitored weekly. The results indicated an early initiation of gonadal growth in WT quail which continued and maintained a plateau throughout the period of study. On the other hand, in general low intensity light, there was a decreased amplitude of the reproductive cycle and the quail exposed to different colour lights (green, red and blue lights) used different incubation times to initiate their gonadal growth and exhibited a gonadal cycle of a different duration up to 15.5 weeks. Thereafter, the gonad of quail of all the LED groups started developing again (including the blue LED exposed quail which remained undeveloped until this age) and attained the increased degree of growth until 26.5 weeks of age. During the second cycle, gonads of green and red light exposed quail continued to increase and maintained a plateau of development similar to WT exposed control while white and blue LED exposed quail exhibited spontaneous regression and attained complete sexual quiescence. Based on our study, it is suggested that long term exposure to blue LED light of low intensity may induce gonadal regression even under long-day conditions (LD 16:8), while exposure to green and red lights appears to maintain a constant photosensitivity after one complete gonadal cycle. Copyright © 2015 Elsevier Inc. All rights reserved.

Progress in LED technology for solid-state lighting

NASA Astrophysics Data System (ADS)

Bhardwaj, Jy; Guth, Greg; Cesaratto, John M.; Shchekin, Oleg B.; Soer, Wouter A.; Götz, Werner; Bonné, Ron; Song, Zhihua F.; den Breejen, Jeroen

2017-02-01

As solid-state lighting adoption moves from bulb socket replacement to lighting system engineering, luminaire manufacturers are beginning to actualize far greater cost savings through luminaire optimization rather than the simplistic process of component cost pareto management. Indeed, there are an increasing number of applications in which we see major shifts in the value chain in terms of increasing the L1 (LED) and L2 (LED array on PCB) value. The L1 value increase stems from a number of factors ranging from simply higher performing LEDs reducing the LED count, to L1 innovation such as high voltage LEDs, optimizing driver efficiency or to the use of high luminance LEDs enabling compact optics, allowing not only more design freedom but also cost reduction through space and weight savings. The L2 value increase is realized predominantly through increasing L2 performance with the use of algorithms that optimize L1 selection and placement and/or through L2 integration of drivers, control electronics, sensors, secondary lens and/or environmental protection, which is also initiating level collapse in the value chain. In this paper we will present the L1 and L2 innovations that are enabling this disruption as well as provide examples of fixture/luminaire level benefits.

Photodynamic action of LED-activated pyropheophorbide-α methyl ester in cisplatin-resistant human ovarian carcinoma cells

NASA Astrophysics Data System (ADS)

Tan, Y.; Xu, C. S.; Xia, X. S.; Yu, H. P.; Bai, D. Q.; He, Y.; Leung, A. W. N.

2009-04-01

Cisplatin-resistance is a major obstacle for the successful therapy to ovarian cancer, and exploring novel approach to deactivate cisplatin-resistant ovarian cells will improve the clinical outcomes. Our present study showed that there was no dark cytotoxicity of MPPa in the COC1/DDP cells at the dose of 0.25 - 4 μM, and LED-activated MPPa resulted in drug dose- and light-dependent cytotoxicity. Apoptotic rate 6 h after LED-activated MPPa (2 μM) increased to 16.71% under the light energy of 1 J/cm2. Confocal laser scanning microscopy showed that MPPa mainly localized in the intracellular membrane system, namely the endoplasmic reticulum, Golgi apparatus, lysosomes and mitochondria in the COC1/DDP cells. Mitochondrial membrane potential (ΔΨm) was collapsed when COC1/DDP cells were exposed to 2 μM MPPa for 20 h and then 1 J/cm2 irradiation of LED source. These data demonstrated that LED-activated MPPa significantly deactivated cisplatin-resistant ovarian cell line COC1/DDP cells and enhanced apoptosis and decreased ΔΨm, which suggests LED is an efficient light source for PDT and LED-activated MPPa can be developed as new modality for treating cisplatin-resistant ovarian.

The innovations with the medical applications of white LEDs and the breakthrough for new business

NASA Astrophysics Data System (ADS)

Shimada, Jun-ichi; Itoh, Kazuhiro; Nishimura, Motohiro; Kawakami, Youichi; Tsuji, Kiyotsugu

2006-02-01

The distance between the LED and the surface of the target organ is about 4-5 cm, and we think this will become the "ultimate super-localized LED lighting". In an experiment with swine, we placed a LED module at the tip of the retractor. When compared to endoscopic lighting, this method illuminated the entire thoracic cavity more brightly. Since the light is emitted from the cylinder-shaped camera component, the light is unidirectional, and the shadows from the surgical instruments are moved to the side of the incision. Retractor LED lights provided enough light in the thoracic cavity. we believe that "medical white LEDs" can contribute in clinical settings as a light source for performing safe operations with bright surgical fields in the near future. Also, we use our LEDs for new real business. In the summer of 2004, LED lighting was world first used in the 1200 year-old Gion Festival for the first time in history as "a lighting device that does not destroy cultural assets by light heat". And the next is "Lighting at the "Diva status at diva gate" and the "Thousand Armed Avalokiteshwara in innermost sanctuary in the main hall" at Kiyomizudera in Kyoto". It was a great success, and we were invited back in the spring of 2005 and for future applications. We think this is the first real application of LEDs as an outdoor lighting device. The number of people who visit Kiyomizudera is 4000,000 annually, and LEDs were adopted to illuminate the diva gate.

Changes in the quality of medicines during storage under LED lighting and consideration of countermeasures.

PubMed

Yamashita, Shuuji; Iguchi, Kazuhiro; Noguchi, Yoshihiro; Sakai, Chihiro; Yokoyama, Satoshi; Ino, Yoko; Hayashi, Hideki; Teramachi, Hitomi; Sako, Magoichi; Sugiyama, Tadashi

2018-01-01

In recent years, the popularity of LED lighting has rapidly increased, owing to its many advantages, including economic benefits. We examined the change in the quality of drugs during storage under LED and fluorescent lighting and found that some medicines exhibited a different degree of color change depending on the light source. The purpose of this study was to investigate the effects of different plastic storage bags on the color change over time when various medicines were stored under LED and fluorescent lighting conditions. Photostability tests were conducted on several types of target drugs. Subsequently, subjective evaluation by ten evaluators and objective evaluation by image analysis software were carried out regarding color change. A similar change in color tone was observed after all types of illumination. Subjective evaluation by 10 evaluators revealed that "change in color tone" occurred in the order of bulb-color LED lighting < daylight-color LED lighting < fluorescent lighting, regardless of the type of plastic bags. A similar tendency was observed also in objective evaluation. In this study, it was considered that a brown light-shielding plastic bag was more effective than a normal plastic bag for the prevention of the color change of medicines stored under LED lighting. The above results suggested that the most appropriate combination of plastic bag and light source for medicine storage was a brown light-shielding plastic bag and bulb-color LED lighting.

Performance evaluation of hybrid VLC using device cost and power over data throughput criteria

NASA Astrophysics Data System (ADS)

Lee, C. C.; Tan, C. S.; Wong, H. Y.; Yahya, M. B.

2013-09-01

Visible light communication (VLC) technology has attained its attention in both academic and industry lately. It is determined by the development of light emitting diode (LED) technology for solid-state lighting (SSL).It has great potential to gradually replace radio frequency (RF) wireless technology because it offers unregulated and unlicensed bandwidth to withstand future demand of indoor wireless access to real-time bandwidth-demanding applications. However, it was found to provide intrusive uplink channel that give rise to unpleasant irradiance from the user device which could interfere with the downlink channel of VLC and hence limit mobility to users as a result of small coverage (field of view of VLC).To address this potential problem, a Hybrid VLC system which integrates VLC (for downlink) and RF (for uplink) technology is proposed. It offers a non-intrusive RF back channel that provides high throughput VLC and maintains durability with conventional RF devices. To deploy Hybrid VLC system in the market, it must be energy and cost saving to attain its equivalent economical advantage by comparing to existing architecture that employs fluorescent or LED lights with RF technology. In this paper, performance evaluation on the proposed hybrid system was carried out in terms of device cost and power consumption against data throughput. Based on our simulation, Hybrid VLC system was found to reduce device cost by 3% and power consumption by 68% when compares to fluorescent lights with RF technology. Nevertheless, when it is compared to LED lights with RF technology, our proposed hybrid system is found to achieve device cost saving as high as 47% and reduced power consumption by 49%. Such promising results have demonstrated that Hybrid VLC system is a feasible solution and has paved the way for greater cost saving and energy efficient compares with the current RF architecture even with the increasing requirement of indoor area coverage.

Effects of Light Quality and Intensity on Diurnal Patterns and Rates of Photo-Assimilate Translocation and Transpiration in Tomato Leaves.

PubMed

Lanoue, Jason; Leonardos, Evangelos D; Grodzinski, Bernard

2018-01-01

Translocation of assimilates is a fundamental process involving carbon and water balance affecting source/sink relationships. Diurnal patterns of CO 2 exchange, translocation (carbon export), and transpiration of an intact tomato source leaf were determined during 14 CO 2 steady-state labeling under different wavelengths at three pre-set photosynthetic rates. Daily patterns showed that photosynthesis and export were supported by all wavelengths of light tested including orange and green. Export in the light, under all wavelengths was always higher than that at night. Export in the light varied from 65-83% of the total daily carbon fixed, depending on light intensity. Photosynthesis and export were highly correlated under all wavelengths ( r = 0.90-0.96). Export as a percentage of photosynthesis (relative export) decreased as photosynthesis increased by increasing light intensity under all wavelengths. These data indicate an upper limit for export under all spectral conditions. Interestingly, only at the medium photosynthetic rate, relative export under the blue and the orange light-emitting diodes (LEDs) were higher than under white and red-white LEDs. Stomatal conductance, transpiration rates, and water-use-efficiency showed similar daily patterns under all wavelengths. Illuminating tomato leaves with different spectral quality resulted in similar carbon export rates, but stomatal conductance and transpiration rates varied due to wavelength specific control of stomatal function. Thus, we caution that the link between transpiration and C-export may be more complex than previously thought. In summary, these data indicate that orange and green LEDs, not simply the traditionally used red and blue LEDs, should be considered and tested when designing lighting systems for optimizing source leaf strength during plant production in controlled environment systems. In addition, knowledge related to the interplay between water and C-movement within a plant and how they are affected by environmental stimuli, is needed to develop a better understanding of source/sink relationships.

Effects of Light Quality and Intensity on Diurnal Patterns and Rates of Photo-Assimilate Translocation and Transpiration in Tomato Leaves

PubMed Central

Lanoue, Jason; Leonardos, Evangelos D.; Grodzinski, Bernard

2018-01-01

Translocation of assimilates is a fundamental process involving carbon and water balance affecting source/sink relationships. Diurnal patterns of CO2 exchange, translocation (carbon export), and transpiration of an intact tomato source leaf were determined during 14CO2 steady-state labeling under different wavelengths at three pre-set photosynthetic rates. Daily patterns showed that photosynthesis and export were supported by all wavelengths of light tested including orange and green. Export in the light, under all wavelengths was always higher than that at night. Export in the light varied from 65–83% of the total daily carbon fixed, depending on light intensity. Photosynthesis and export were highly correlated under all wavelengths (r = 0.90–0.96). Export as a percentage of photosynthesis (relative export) decreased as photosynthesis increased by increasing light intensity under all wavelengths. These data indicate an upper limit for export under all spectral conditions. Interestingly, only at the medium photosynthetic rate, relative export under the blue and the orange light-emitting diodes (LEDs) were higher than under white and red-white LEDs. Stomatal conductance, transpiration rates, and water-use-efficiency showed similar daily patterns under all wavelengths. Illuminating tomato leaves with different spectral quality resulted in similar carbon export rates, but stomatal conductance and transpiration rates varied due to wavelength specific control of stomatal function. Thus, we caution that the link between transpiration and C-export may be more complex than previously thought. In summary, these data indicate that orange and green LEDs, not simply the traditionally used red and blue LEDs, should be considered and tested when designing lighting systems for optimizing source leaf strength during plant production in controlled environment systems. In addition, knowledge related to the interplay between water and C-movement within a plant and how they are affected by environmental stimuli, is needed to develop a better understanding of source/sink relationships. PMID:29915612

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

PubMed

Pawson, S M; Bader, M K-F

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

Phototaxis of Propsilocerus akamusi (Diptera: Chironomidae) From a Shallow Eutrophic Lake in Response to Led Lamps.

PubMed

Hirabayashi, Kimio; Nagai, Yoshinari; Mushya, Tetsuya; Higashino, Makoto; Taniguchi, Yoshio

2017-06-01

A study on the attraction of adult Propsilocerus akamusi midges to different-colored light traps was carried out from October 21 to November 15, 2013. The 6 colored lights used in light-emitting diode (LED) lamps were white, green, red, blue, amber, and ultraviolet (UV). The UV lamp attracted the most P. akamusi, followed by green, white, blue, amber, and red. A white pulsed LED light attracted only half the number of midges as did a continuous-emission white LED light. The result indicated that manipulation of light color, considering that the red LED light and/or pulsed LED light are not as attractive as the other colors, may be appropriate for the development of an overall integrated strategy to control nuisance P. akamusi in the Lake Suwa area.

A brief history of LED photopolymerization.

PubMed

Jandt, Klaus D; Mills, Robin W

2013-06-01

The majority of modern resin-based oral restorative biomaterials are cured via photopolymerization processes. A variety of light sources are available for this light curing of dental materials, such as composites or fissure sealants. Quartz-tungsten-halogen (QTH) light curing units (LCUs) have dominated light curing of dental materials for decades and are now almost entirely replaced by modern light emitting diode light curing units (LED LCUs). Exactly 50 years ago, visible LEDs were invented. Nevertheless, it was not before the 1990s that LEDs were seriously considered by scientists or manufactures of commercial LCUs as light sources to photopolymerize dental composites and other dental materials. The objective of this review paper is to give an overview of the scientific development and state-of-the-art of LED photopolymerization of oral biomaterials. The materials science of LED LCU devices and dental materials photopolymerized with LED LCU, as well as advantages and limits of LED photopolymerization of oral biomaterials, are discussed. This is mainly based on a review of the most frequently cited scientific papers in international peer reviewed journals. The developments of commercial LED LCUs as well as aspects of their clinical use are considered in this review. The development of LED LCUs has progressed in steps and was made possible by (i) the invention of visible light emitting diodes 50 years ago; (ii) the introduction of high brightness blue light emitting GaN LEDs in 1994; and (iii) the creation of the first blue LED LCUs for the photopolymerization of oral biomaterials. The proof of concept of LED LCUs had to be demonstrated by the satisfactory performance of resin based restorative dental materials photopolymerized by these devices, before LED photopolymerization was generally accepted. Hallmarks of LED LCUs include a unique light emission spectrum, high curing efficiency, long life, low energy consumption and compact device form factor. By understanding the physical principles of LEDs, the development of LED LCUs, their strengths and limitations and the specific benefits of LED photopolymerization will be better appreciated. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

New Carrollton Federal Building Lighting Retrofit Captures Cool Savings

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

2017-01-01

Case study describes how the U.S. General Services Administration cut a $291,000 annual lighting electric bill to an estimated $53,500 by upgrading their fluorescent lighting to a new LED troffer lighting and controls system in the New Carrollton Federal Building in Lanham, Maryland. The lighting project yielded an 82% reduction in energy use and earned GSA two awards for exemplary performance from the Interior Lighting Campaign in 2016.

Design of a detection system of highlight LED arrays' effect on the human organization

NASA Astrophysics Data System (ADS)

Chen, Shuwang; Shi, Guiju; Xue, Tongze; Liu, Yanming

2009-05-01

LED (Light Emitting Diode) has many advantages in the intensity, wavelength, practicality and price, so it is feasible to apply in biomedicine engineering. A system for the research on the effect of highlight LED arrays to human organization is designed. The temperature of skin surface can rise if skin and organization are in irradiation by highlight LED arrays. The metabolism and blood circulation of corresponding position will be quicker than those not in the shine, so the surface temperature will vary in different position of skin. The structure of LED source arrays system is presented and a measure system for studying LED's influence on human organization is designed. The temperature values of shining point are detected by infrared temperature detector. Temperature change is different according to LED parameters, such as the number, irradiation time and luminous intensity of LED. Experimental device is designed as an LED arrays pen. The LED arrays device is used to shine the points of human body, then it may effect on personal organization as well as the acupuncture. The system is applied in curing a certain skin disease, such as age pigment, skin cancer and fleck.

Laser Based Phosphor Converted Solid State White Light Emitters

NASA Astrophysics Data System (ADS)

Cantore, Michael

Artificial lighting and as a consequence the ability to be productive when the sun does not shine may be a profound achievement in society that is largely taken for granted. As concerns arise due to our dependence on energy sources with finite lifespan or environmentally negative effects, efforts to reduce energy consumption and create clean renewable alternatives has become highly valued. In the scope of artificial lighting, the use of incandescent lamps has shifted to more efficient light sources. Fluorescent lighting made the first big gains in efficiency over incandescent lamps with peak efficiency for mature designs reaching luminous efficacy of approximately 90 lm/W; more than three times as efficient as an incandescent lamp. Lamps based on light emitting diodes (LEDs) which can produce light at even greater efficiency, color quality and without the potential for hazardous chemical release from lamp failure. There is a significant challenge with LED based light sources. Their peak efficiency occurs at low current densities and then droops as the current density increases. Laser diodes (LDs) do not suffer from decreasing efficiency due to increased current. An alternative solid state light source using LDs has potential to make further gains in efficiency as well as allow novel illuminant designs which may be impractical or even impossible even with LED or other conventional sources. While similar to LEDS, the use of LDs does present new challenges largely due to the increased optical power density which must be accommodated in optics and phosphor materials. Single crystal YAG:Ce has been shown to be capable of enduring this more extreme operating environment while retaining the optical and fluorescing qualities desired for use as a wavelength converter in phosphor converted LD based white emitting systems. The incorporation of this single crystal phosphor in a system with a commercial laser diode with peak wall plug efficiency of 31% resulted in emission of white light with a luminous efficacy of 86.7 lm/W at a current of 1.4A. A total luminous flux of 1100 lm with luminous efficacy of 76 lm/W at 3.0 A current was achieved. Simulations have been conducted which show that as the InGaN LD technology matures towards the efficiencies of about 75%, which has been observed in the GaAs material system, luminous efficacy of similar blue LD with single crystal YAG:Ce systems will exceed 200 lm/W.

Effect of LED light stimulation on sleep latency in night shift people

NASA Astrophysics Data System (ADS)

Wu, Jih-Huah; Chang, Yang-Chyuan; Chiu, Hui-Ling; Fang, Wei; Shan, Yi-Chia; Chen, Ming-Jie; Chang, Yu-Ting

2014-05-01

Sleep problems are getting worse and worse in modern world. They have a severe impact on psychological and physical health, as well as social performances. From our previous study, the brainwave α rhythm, θ wave and β wave were affected by radiating the palm of the subjects with low-level laser array. In addition, from other study, the LED array stimulator (LEDAS) also has the similar effects. In the present study, LED light was used to radiate the left palm of the subjects too, and the effects were assessed with the multiple sleep latency test (MSLT) and heart-rate variability (HRV) analysis. The results revealed that it doesn't have significant meaning between these two groups. However, the tendency of the sleep latency (SL) in the LED group was shorter than that in the control group. In addition, the autonomic nervous system (ANS) analysis showed that the sympathetic nervous system was getting larger in the LED group than that in the control group, and total ANS activity were mainly getting larger in the LED group. We infer that this LED stimulation could reduce SL and balance ANS activity of the night-shift people. In the future, the further study will be conducted on normal subjects.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tracy, Jennifer; Alstone, Peter; Jacobson, Arne

In this study, we performed a market trial of off-grid LED lighting products in Maai Mahiu, arural Kenyan town. Our goals were to assess consumer demand and consumer preferences with respect to off-grid lighting systems and to gain feedback from off-grid lighting users at the point of purchase and after they have used to products for some time.

Color separation system with angularly positioned light source module for pixelized backlighting.

PubMed

Chen, Po-Chou; Lin, Hui-Hsiung; Chen, Cheng-Huan; Lee, Chi-Hung; Lu, Mao-Hong

2010-01-18

A color-separation system that angularly positions color LEDs to produce color separation and a lens array to focus this light onto the pixels is proposed. The LED rays from different incident angles are mapped into corresponding sub-pixel positions to efficiently display color image, which can be used to replace the absorbing color filter in the conventional liquid crystal layer. In this paper, the prototype backlight has been designed, fabricated and characterized. The measurement results of this module showed that a gain factor of transmission efficiency three times more than that of conventional color filters efficiency improvement and a larger color gamut are expected.

Advanced Plant Habitat

NASA Image and Video Library

2018-03-12

The first growth test of crops in the Advanced Plant Habitat aboard the International Space Station yielded great results. Arabidopsis seeds – small flowering plants related to cabbage and mustard – grew for about six weeks and the dwarf wheat for five weeks. The APH is now ready to support large plant testing on ISS. APH is a fully enclosed, closed-loop system with an environmentally controlled growth chamber. It uses red, blue and green LED lights, and broad spectrum white LED lights. The system's more than 180 sensors will relay real-time information, including temperature, oxygen content and moisture levels back to the team at Kennedy Space Center.

Using affordable LED arrays for photo-stimulation of neurons.

PubMed

Valley, Matthew; Wagner, Sebastian; Gallarda, Benjamin W; Lledo, Pierre-Marie

2011-11-15

Standard slice electrophysiology has allowed researchers to probe individual components of neural circuitry by recording electrical responses of single cells in response to electrical or pharmacological manipulations(1,2). With the invention of methods to optically control genetically targeted neurons (optogenetics), researchers now have an unprecedented level of control over specific groups of neurons in the standard slice preparation. In particular, photosensitive channel rhodopsin-2 (ChR2) allows researchers to activate neurons with light(3,4). By combining careful calibration of LED-based photostimulation of ChR2 with standard slice electrophysiology, we are able to probe with greater detail the role of adult-born interneurons in the olfactory bulb, the first central relay of the olfactory system. Using viral expression of ChR2-YFP specifically in adult-born neurons, we can selectively control young adult-born neurons in a milieu of older and mature neurons. Our optical control uses a simple and inexpensive LED system, and we show how this system can be calibrated to understand how much light is needed to evoke spiking activity in single neurons. Hence, brief flashes of blue light can remotely control the firing pattern of ChR2-transduced newborn cells.

Experimental Study on Active Cooling Systems Used for Thermal Management of High-Power Multichip Light-Emitting Diodes

PubMed Central

2014-01-01

The objective of this study was to develop suitable cooling systems for high-power multichip LEDs. To this end, three different active cooling systems were investigated to control the heat generated by the powering of high-power multichip LEDs in two different configurations (30 and 2 × 15 W). The following cooling systems were used in the study: an integrated multi-fin heat sink design with a fan, a cooling system with a thermoelectric cooler (TEC), and a heat pipe cooling device. According to the results, all three systems were observed to be sufficient for cooling high-power LEDs. Furthermore, it was observed that the integrated multifin heat sink design with a fan was the most efficient cooling system for a 30 W high-power multichip LED. The cooling system with a TEC and 46 W input power was the most efficient cooling system for 2 × 15 W high-power multichip LEDs. PMID:25162058

Binning and filtering: the six-color solution

NASA Astrophysics Data System (ADS)

Ashdown, Ian; Robinson, Shane; Salsbury, Marc

2006-08-01

The use of LED backlighting for LCD displays requires careful binning of red, green, and blue LEDs by dominant wavelength to maintain the color gamuts as specified by NTSC, SMPTE, and EBU/ITU standards. This problem also occurs to a lesser extent with RGB and RGBA assemblies for solid-state lighting, where color gamut consistency is required for color-changing luminaires. In this paper, we propose a "six-color solution," based on Grassman's laws, that does not require color binning, but nevertheless guarantees a fixed color gamut that subsumes the color gamuts of carefully-binned RGB assemblies. A further advantage of this solution is that it solves the problem of peak wavelength shifts with varying junction temperatures. The color gamut can thus remain fixed over the full range of LED intensities and ambient temperatures. A related problem occurs with integrated circuit (IC) colorimeters used for optical feedback with LED backlighting and RGB(A) solid-state lighting, wherein it can be difficult to distinguish between peak wavelength shifts and changes in LED intensity. We apply our six-color solution to the design of a novel colorimeter for LEDs that independently measures changes in peak wavelength and intensity. The design is compatible with current manufacturing techniques for tristimulus colorimeter ICs. Together, the six-color solution for LEDs and colorimeters enables less expensive LED backlighting and solid-state lighting systems with improved color stability.

Investigation of self-adaptive LED surgical lighting based on entropy contrast enhancing method

NASA Astrophysics Data System (ADS)

Liu, Peng; Wang, Huihui; Zhang, Yaqin; Shen, Junfei; Wu, Rengmao; Zheng, Zhenrong; Li, Haifeng; Liu, Xu

2014-05-01

Investigation was performed to explore the possibility of enhancing contrast by varying the spectral distribution (SPD) of the surgical lighting. The illumination scenes with different SPDs were generated by the combination of a self-adaptive white light optimization method and the LED ceiling system, the images of biological sample are taken by a CCD camera and then processed by an 'Entropy' based contrast evaluation model which is proposed specific for surgery occasion. Compared with the neutral white LED based and traditional algorithm based image enhancing methods, the illumination based enhancing method turns out a better performance in contrast enhancing and improves the average contrast value about 9% and 6%, respectively. This low cost method is simple, practicable, and thus may provide an alternative solution for the expensive visual facility medical instruments.

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

NASA Astrophysics Data System (ADS)

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

2017-04-01

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

Controllable spectrum artificial sunlight source system using LEDs with 32 different peak wavelengths of 385-910 nm.

PubMed

Fujiwara, Kazuhiro; Yano, Akira

2011-04-01

This study developed a lighting system that produces an approximate spectral irradiance (SI) of ground level sunlight in the wavelength range of 385-910 nm (GLS₃₈₅₋₉₁₀) using 547 light-emitting diodes (LEDs) with 32 different peak wavelengths. The produced SI can be modified over an arbitrary wavelength band. The SI at the light outlet reached up to 1/2 of the GLS₃₈₅₋₉₁₀ of a sunny April day, although the produced SI deviated from the GLS₃₈₅₋₉₁₀ at some wavelengths. For subsequent experiments, the reference SI was defined as 1/4 GLS₃₈₅₋₉₁₀ of a sunny April day. The SI produced from the lighting system was adjusted to approximate the reference SI. The ratios of the produced SI and the reference SI were within 0.72-1.28. As an application of the lighting system for biological studies, the transmitted SI of a green leaf of perilla (Perilla frutescens L.) was investigated. The curve shape of the transmitted SI, which had characteristically low transmission percentages of blue and red light, reflected the characteristics of the absorption spectra of chlorophylls. The lighting system is therefore potentially beneficial for use in diagnosing physiological conditions of plant leaves, although its application is not limited to plant physiological studies. Copyright © 2010 Wiley-Liss, Inc.

Effect of light-emitting diode vs. fluorescent lighting on laying hens in aviary hen houses: Part 1 - Operational characteristics of lights and production traits of hens.

PubMed

Long, H; Zhao, Y; Wang, T; Ning, Z; Xin, H

2016-01-01

Light-emitting diode (LED) lights are becoming more affordable for agricultural applications. Despite many lab-scale studies concerning impact of LED on poultry, little research has been documented under field production conditions, especially for laying hens. This 15-month field study was carried out to evaluate the effects of LED vs. fluorescent (FL) lights on laying hens (Dekalb white breed) using 4 (2 pairs) aviary hen houses each at a nominal capacity of 50,000 hens. The evaluation was done regarding operational characteristics of the lights and hen production traits. The results show that spatial distribution of the LED light was less uniform than that of the FL light. Light intensity of the LED light decreased by 27% after 3,360 h use but remained quite steady from 3,360 to 5,760 h use. Eleven out of 762 (1.44%) LED lamps (new at onset of the study) in the 2 houses failed during the 15-month experiment period. The neck area of the LED lamp was hottest, presumably the primary reason for the lamp failure as cracks were noticed in the neck region of all failed LED lamps. No differences were observed in egg weight, hen-day egg production, feed use, and mortality rate between LED and FL regimens. However, hens under the FL had higher eggs per hen housed and better feed conversion than those under the LED during 20 to 70 wk production (P < 0.05). Hens under the LED tended to have less feather uniformity and insulation than those under the FL (P < 0.05). Moreover, hens under the LED showed a larger median avoidance distance than those under the FL at 36 wk age (P < 0.05), indicating that hens under the LED were more alert; but no difference at 60 wk age. More comparative research to quantify behavioral and production responses of different breeds of hens to LED vs. FL lighting seems warranted. © 2015 Poultry Science Association Inc.

Experimental investigation of analog and digital dimming techniques on photometric performance of an indoor Visible Light Communication (VLC) system

NASA Astrophysics Data System (ADS)

Zafar, Fahad; Kalavally, Vineetha; Bakaul, Masuduzzaman; Parthiban, R.

2015-09-01

For making commercial implementation of light emitting diode (LED) based visible light communication (VLC) systems feasible, it is necessary to incorporate it with dimming schemes which will provide energy savings, moods and increase the aesthetic value of the places using this technology. There are two general methods which are used to dim LEDs commonly categorized as analog and digital dimming. Incorporating fast data transmission with these techniques is a key challenge in VLC. In this paper, digital and analog dimming for a 10 Mb/s non return to zero on-off keying (NRZ-OOK) based VLC system is experimentally investigated considering both photometric and communicative parameters. A spectrophotometer was used for photometric analysis and a line of sight (LOS) configuration in the presence of ambient light was used for analyzing communication parameters. Based on the experimental results, it was determined that digital dimming scheme is preferable for use in indoor VLC systems requiring high dimming precision and data transmission at lower brightness levels. On the other hand, analog dimming scheme is a cost effective solution for high speed systems where dimming precision is insignificant.

Light-emitting diodes for analytical chemistry.

PubMed

Macka, Mirek; Piasecki, Tomasz; Dasgupta, Purnendu K

2014-01-01

Light-emitting diodes (LEDs) are playing increasingly important roles in analytical chemistry, from the final analysis stage to photoreactors for analyte conversion to actual fabrication of and incorporation in microdevices for analytical use. The extremely fast turn-on/off rates of LEDs have made possible simple approaches to fluorescence lifetime measurement. Although they are increasingly being used as detectors, their wavelength selectivity as detectors has rarely been exploited. From their first proposed use for absorbance measurement in 1970, LEDs have been used in analytical chemistry in too many ways to make a comprehensive review possible. Hence, we critically review here the more recent literature on their use in optical detection and measurement systems. Cloudy as our crystal ball may be, we express our views on the future applications of LEDs in analytical chemistry: The horizon will certainly become wider as LEDs in the deep UV with sufficient intensity become available.

Comparative studies on dimming capabilities of retrofit LED lamps

NASA Astrophysics Data System (ADS)

Ionescu, Ciprian; Vasile, Alexandru; Codreanu, Norocel; Negroiu, Rodica

2016-12-01

These days many variants for lighting systems are available on the market, and new solutions are about to emerge. Most of the new lamps are offered in form to be retrofitted to existing sockets and luminaires. In this paper, are presented some systematically investigations on different lamps as LEDs, Compact Fluorescent Lamps (CFLs), tungsten, and new available Cold Cathode Fluorescent Lamps (CCFLs), regarding the light level, dimming performances and also the resulting flicker and power distortion performances. The light level was expressed by the illuminance level, measured for all lamps in the same conditions, at the same distance and on the same surface represented by the photometer probe.

Absorbance Based Light Emitting Diode Optical Sensors and Sensing Devices

PubMed Central

O'Toole, Martina; Diamond, Dermot

2008-01-01

The ever increasing demand for in situ monitoring of health, environment and security has created a need for reliable, miniaturised sensing devices. To achieve this, appropriate analytical devices are required that possess operating characteristics of reliability, low power consumption, low cost, autonomous operation capability and compatibility with wireless communications systems. The use of light emitting diodes (LEDs) as light sources is one strategy, which has been successfully applied in chemical sensing. This paper summarises the development and advancement of LED based chemical sensors and sensing devices in terms of their configuration and application, with the focus on transmittance and reflectance absorptiometric measurements. PMID:27879829

Analysis and Design of Phase Change Thermal Control for Light Emitting Diode (LED) Spacesuit Helmet Lights

NASA Technical Reports Server (NTRS)

Bue, Grant C.; Nguyen, Hiep X.; Keller, John R.

2010-01-01

LED Helmet Extravehicular Activity Helmet Interchangeable Portable (LEHIP) lights for the Extravehicular Mobility Unit (EMU) have been built and tested and are currently being used on the International Space Station. A design is presented of the passive thermal control system consisting of a chamber filled with aluminum foam and wax. A thermal math model of LEHIP was built and correlated by test to show that the thermal design maintains electronic components within hot and cold limits for a 7 hour spacewalk in the most extreme EVA average environments, and do not pose a hazard to the crew or to components of the EMU.

Absorbance Based Light Emitting Diode Optical Sensors and Sensing Devices.

PubMed

O'Toole, Martina; Diamond, Dermot

2008-04-07

The ever increasing demand for in situ monitoring of health, environment and security has created a need for reliable, miniaturised sensing devices. To achieve this, appropriate analytical devices are required that possess operating characteristics of reliability, low power consumption, low cost, autonomous operation capability and compatibility with wireless communications systems. The use of light emitting diodes (LEDs) as light sources is one strategy, which has been successfully applied in chemical sensing. This paper summarises the development and advancement of LED based chemical sensors and sensing devices in terms of their configuration and application, with the focus on transmittance and reflectance absorptiometric measurements.

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

Treesearch

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

2013-01-01

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

Optical Indoor Positioning System Based on TFT Technology

PubMed Central

Gőzse, István

2015-01-01

A novel indoor positioning system is presented in the paper. Similarly to the camera-based solutions, it is based on visual detection, but it conceptually differs from the classical approaches. First, the objects are marked by LEDs, and second, a special sensing unit is applied, instead of a camera, to track the motion of the markers. This sensing unit realizes a modified pinhole camera model, where the light-sensing area is fixed and consists of a small number of sensing elements (photodiodes), and it is the hole that can be moved. The markers are tracked by controlling the motion of the hole, such that the light of the LEDs always hits the photodiodes. The proposed concept has several advantages: Apart from its low computational demands, it is insensitive to the disturbing ambient light. Moreover, as every component of the system can be realized by simple and inexpensive elements, the overall cost of the system can be kept low. PMID:26712753

Development of a Novel Optical Biosensor for Detection of Organophoshorus Pesticides Based on Methyl Parathion Hydrolase Immobilized by Metal-Chelate Affinity

PubMed Central

Lan, Wensheng; Chen, Guoping; Cui, Feng; Tan, Feng; Liu, Ran; Yushupujiang, Maolidan

2012-01-01

We have developed a novel optical biosensor device using recombinant methyl parathion hydrolase (MPH) enzyme immobilized on agarose by metal-chelate affinity to detect organophosphorus (OP) compounds with a nitrophenyl group. The biosensor principle is based on the optical measurement of the product of OP catalysis by MPH (p-nitrophenol). Briefly, MPH containing six sequential histidines (6× His tag) at its N-terminal was bound to nitrilotriacetic acid (NTA) agarose with Ni ions, resulting in the flexible immobilization of the bio-reaction platform. The optical biosensing system consisted of two light-emitting diodes (LEDs) and one photodiode. The LED that emitted light at the wavelength of the maximum absorption for p-nitrophenol served as the signal light, while the other LED that showed no absorbance served as the reference light. The optical sensing system detected absorbance that was linearly correlated to methyl parathion (MP) concentration and the detection limit was estimated to be 4 μM. Sensor hysteresis was investigated and the results showed that at lower concentration range of MP the difference got from the opposite process curves was very small. With its easy immobilization of enzymes and simple design in structure, the system has the potential for development into a practical portable detector for field applications. PMID:23012501

[Psychophysiological research of changes of the functional condition of the neuro-psychic sphere of younger schoolchildren during the school day at luminescent and LED lighting in the classroom].

PubMed

Teksheva, L M; Nadezhdin, D S

2014-01-01

The purpose of the study is to test the hypothesis that the LED lighting (LL) in training class does not have a negative impact on the change in the functional state of the neuro-psychiatric sphere in pupils by the end of the school day, if compared with traditional for schools fluorescent lighting (FL). With the help of specially matched methods for psychophysiological examination there was performed the testing of changes in the functional state of the neuro-psychiatric in pupils during the school day and there was made an analysis of these changes in dependence on the type of lighting the classroom. LL, if compared to FL, was established to lead to a significant weakening of the negative changes of functional lability of the visual analyzer, the power of excitation of the nervous system and cognitive functions, as well as to an increase in positive changes in psychomotorics. The data obtained allow us to recommend the use of LED lighting equipment in modern schools.

The involvement of ATF4 and S-opsin in retinal photoreceptor cell damage induced by blue LED light.

PubMed

Ooe, Emi; Tsuruma, Kazuhiro; Kuse, Yoshiki; Kobayashi, Saori; Shimazawa, Masamitsu; Hara, Hideaki

2017-01-01

Blue light is a high-energy emitting light with a short wavelength in the visible light spectrum. Blue light induces photoreceptor apoptosis and causes age-related macular degeneration or retinitis pigmentosa. In the present study, we investigated the roles of endoplasmic reticulum (ER) stress induced by blue light-emitting diode (LED) light exposure in murine photoreceptor cells. The murine photoreceptor cell line was incubated and exposed to blue LED light (464 nm blue LED light, 450 lx, 3 to 24 h). The expression of the factors involved in the unfolded protein response pathway was examined using quantitative real-time reverse transcription (RT)-PCR and immunoblot analysis. The aggregation of short-wavelength opsin (S-opsin) in the murine photoreceptor cells was observed with immunostaining. The effect of S-opsin knockdown on ATF4 expression in the murine photoreceptor cell line was also investigated. Exposure to blue LED light increased the bip , atf4 , and grp94 mRNA levels, induced the expression of ATF4 protein, and increased the levels of ubiquitinated proteins. Exposure to blue LED light in combination with ER stress inducers (tunicamycin and dithiothreitol) induced the aggregation of S-opsin. S-opsin mRNA knockdown prevented the induction of ATF4 expression in response to exposure to blue LED light. These findings indicate that the aggregation of S-opsin induced by exposure to blue LED light causes ER stress, and ATF4 activation in particular.

Pulp Chamber Heating: An In Vitro Study Evaluating Different Light Sources and Resin Composite Layers.

PubMed

Andreatta, Lígia Maria Lima; Furuse, Adilson Yoshio; Prakki, Anuradha; Bombonatti, Juliana Fraga Soares; Mondelli, Rafael Francisco Lia

2016-01-01

The aim of the present in vitro study was to evaluate the temperature variation inside the pulp chamber during light-activation of the adhesive and resin composite layers with different light sources. Cavities measuring 8x10 mm were prepared on the buccal surface of bovine incisors, leaving a remaining dentin thickness of 1 mm. Specimens were placed in a 37±1 °C water bath to standardize the temperature. The temperature in the pulp chamber was measured every 10 s during 40 s of light activation of the adhesive system (SBMP-3M/ESPE) and in the three consecutive 1-mm-thick layers of resin composite (Z250-3M/ESPE). Three light source devices were evaluated: Elipar 2500 (QTH), LD Max (LED low irradiance) and VALO (LED high irradiance). The results were submitted to one-way ANOVA with repeated measures and Tukey's test, both with p<0.001. The exothermic reaction warming was observed in the Z250 increments, but not in the SBMP. The high irradiance LED showed a higher temperature average (42.7±1.56 °C), followed by the quartz-tungsten-halogen light (40.6±0.67 °C) and the lower irradiance LED (37.8±0.12 °C). Higher temperature increases were observed with the adhesive and the first resin composite increment light-activation, regardless of the employed light source. From the second increment of Z250, the restorative material acted as a dispersive structure of heat, reducing temperature increases. Regardless the light source and restorative step, the temperature increased with the irradiation time. It may be concluded that the light source, irradiation time and resin composite thickness interfered in the temperature variation inside the pulp chamber.

Spectral sensitivity of the circadian system

NASA Astrophysics Data System (ADS)

Figueiro, Mariana G.; Bullough, John D.; Rea, Mark S.

2004-01-01

Light exposure regulates several circadian functions in normal humans including the sleep-wake cycle. Individuals with Alzheimer"s Disease (AD) often do not have regular patterns of activity and rest, but, rather, experience random periods of sleep and agitation during both day and night. Bright light during the day and darkness at night has been shown to consolidate activity periods during the day and rest periods at night in AD patients. The important characteristics of bright light exposure (quantity, spectrum, distribution, timing and duration) for achieving these results in AD patients is not yet understood. Recent research has shown that moderate (~18 lx at the cornea) blue (~470 nm) light is effective at suppressing melatonin in normal humans. It was hypothesized that blue light applied just before AD patients retire to their beds for the night would have a measurable impact on their behavior. A pilot study was conducted for 30 days in a senior health care facility using four individuals diagnosed with mild to moderate levels of dementia. Four AD patients were exposed to arrays of blue light from light emitting diodes (max wavelength = 470 nm) in two-hour sessions (18:00 to 20:00 hours) for 10 days. As a control, they were exposed to red light (max wavelength = 640 nm) in two-hour sessions for 10 days prior to the blue light exposure. Despite the modest sample size, exposure to blue LEDs has shown to affect sleep quality and median body temperature peak of these AD patients. Median body temperature peak was delayed by approximately 2 hours after exposure to blue LEDs compared to exposure to red LEDs and sleep quality was improved. This pilot study demonstrated that light, especially LEDs, can be an important contribution to helping AD patients regulate their circadian functions.

Enhanced optical output power of blue light-emitting diodes with quasi-aligned gold nanoparticles

PubMed Central

2014-01-01

The output power of the light from GaN-based light-emitting diodes (LEDs) was enhanced by fabricating gold (Au) nanoparticles on the surface of p-GaN. Quasi-aligned Au nanoparticle arrays were prepared by depositing Au thin film on an aligned suspended carbon nanotube thin film surface and then putting the Au-CNT system on the surface of p-GaN and thermally annealing the sample. The size and position of the Au nanoparticles were confined by the carbon nanotube framework, and no other additional residual Au was distributed on the surface of the p-GaN substrate. The output power of the light from the LEDs with Au nanoparticles was enhanced by 55.3% for an injected current of 100 mA with the electrical property unchanged compared with the conventional planar LEDs. The enhancement may originate from the surface plasmon effect and scattering effect of the Au nanoparticles. PMID:24393473

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

NASA Astrophysics Data System (ADS)

Grandjean, N.

2010-09-01

Generating white light from electricity with maximum efficacy has been a long quest since the first incandescent lamp was invented by Edison at the end of the 19th century. Nowadays, semiconductors are making reality the holy grail of converting electrons into photons with 100% efficiency and with colours that can be mixed for white light illumination. The revolution in solid-state lighting (SSL) dates to 1994 when Nakamura reported the first high-brightness blue LED based on GaN semiconductors. Then, white light was produced by simply combining a blue dye with a yellow phosphor. After more than a decade of intensive research the performance of white LEDs is quite impressive, beating by far the luminous efficacy of compact fluorescent lamps. We are likely close to replacing our current lighting devices by SSL lamps. However, there are still technological and fabrication cost issues that could delay large market penetration of white LEDs. Interestingly, SSL may create novel ways of using light that could potentially limit electricity saving. Whatever the impact of SSL, it will be significant on our daily life. The purpose of this special cluster issue is to produce a snapshot of the current situation of SSL from different viewing angles. In an introductory paper, Tsao and co-workers from Sandia National Laboratories, present an energy-economics perspective of SSL considering societal changes and SSL technology evolution. In a second article, Narukawa et al working at Nichia Corporation—the pioneer and still the leading company in SSL—describe the state of the art of current research products. They demonstrate record performance with white LEDs exhibiting luminous efficacy of 183 lm W-1 at high-current injection. Then, a series of topical papers discuss in detail various aspects of the physics and technology of white LEDs Carrier localization in InGaN quantum wells has been considered the key to white LEDs' success despite the huge density of defects. A comprehensive review of the different localization mechanisms and their implication for internal quantum efficiency (IQE) is proposed by Oliver and co-workers from Cambridge University. When discussing IQE in InGaN-based LEDs, the efficiency droop at high-current injection always emerges, which is a major concern for the future of SSL technology. Here, a collaborative work between Samsung and the Gwangju Institute of Science and Technology (Korea) proves that a specific design of the active region can limit this detrimental effect. Once the issue of the IQE is solved, one still has to let the photons out of the chip. Matioli and Weisbuch from the University of California at Santa Barbara introduce the use of photonic crystals (PhCs) to improve light extraction efficiency. They describe different approaches to overcoming the main limitation of LEDs when implementing surface PhCs. The technology of SSL, and in particular of colour rendering, is tackled by Zukauskas et al who studied in detail different white light sources. They show that extreme colour-fidelity indices need to cover the entire spectrum, with a broad-band at 530-610 nm and a component beyond 610 nm. Then, the reliability of GaN-based LEDs is discussed in the paper of Meneghesso and co-workers. The authors consider the most important physical mechanisms that are (i) the degradation of the active layer of LEDs, (ii) the degradation of the package/phosphor system, (iii) the failure of GaN-based LEDs against electrostatic discharge. Finally, GaN LEDs on silicon developed in the group of Egawa at the Nagoya Institute of Technology are presented. This technology could allow a significant decrease in the fabrication cost of white LEDs.

Effects of white light-emitting diode (LED) light exposure with different correlated color temperatures (CCTs) on human lens epithelial cells in culture.

PubMed

Xie, Chen; Li, Xiuyi; Tong, Jianping; Gu, Yangshun; Shen, Ye

2014-01-01

Cataract is the major cause for legal blindness in the world. Oxidative stress on the lens epithelial cells (hLECs) is the most important factor in cataract formation. Cumulative light-exposure from widely used light-emitting diodes (LEDs) may pose a potential oxidative threat to the lens epithelium, due to the high-energy blue light component in the white-light emission from diodes. In the interest of perfecting biosafety standards for LED domestic lighting, this study analyzed the photobiological effect of white LED light with different correlated color temperatures (CCTs) on cultured hLECs. The hLECs were cultured and cumulatively exposed to multichromatic white LED light with CCTs of 2954, 5624, and 7378 K. Cell viability of hLECs was measured by Cell Counting Kit-8 (CCK-8) assay. DNA damage was determined by alkaline comet assay. Intracellular reactive oxygen species (ROS) generation, cell cycle, and apoptosis were quantified by flow cytometry. Compared with 2954 and 5624 K LED light, LED light having a CCT of 7378 K caused overproduction of intracellular ROS and severe DNA damage, which triggered G2 /M arrest and apoptosis. These results indicate that white LEDs with a high CCT could cause significant photobiological damage to hLECs. © 2014 The American Society of Photobiology.

Permanent transparent color-warming glazes for dimmable and non-dimmable LED bulbs

NASA Astrophysics Data System (ADS)

Spanard, Jan-Marie A.

2014-02-01

Illuminant metameric failure is frequently experienced when viewing material samples under LED generated light vs. traditional incandescent light. LED light temperatures can be improved with phosphor coatings, but long-wave red light is still generally absent in LED "warm-white" light, resulting in metameric failure of orange-to-red objects. Drawing on techniques developed for the architectural restoration of stained glass, we find that transparent, heat-resistant, permanent, pigmented coatings can be applied to any glass, aluminum or plastic surface of an LED bulb, including the phosphor plate, dome or envelope, to produce warmer visible light than in current warm-light LED bulbs. These glazes can be applied in combination with existing technologies to better tune the LED emitted light or they may be used alone. These pigmented coatings include, but are not limited to, those made by suspending inorganic materials in potassium silicates or durable transparent pigmented resins. The pigmented resin glazes may be produced in either a clear gloss vehicle or an iridescent, light diffusing transparent base. Further, a graduated density of the tinted glazes on dimmable bulbs allow the light to change color as wattage is diminished. The glazes may be applied in the manufacturing of the bulb or marketed to current bulb owners as an after-market product to better tune the thousands of LED light bulbs currently in use.

Sensitive determination of sulfonamides in environmental water by capillary electrophoresis coupled with both silvering detection window and in-capillary optical fiber light-emitting diode-induced fluorescence detector.

PubMed

Ji, Hongyun; Wu, Yu; Duan, Zhijuan; Yang, Feng; Yuan, Hongyan; Xiao, Dan

2017-02-01

A new detector, silvering detection window and in-capillary optical fiber light-emitting diode-induced fluorescence detector (SDW-ICOF-LED-IFD), is introduced for capillary electrophoresis (CE). The strategy of the work was that half surface of the detection window was coated with silver mirror, which could reflect the undetected fluorescence to the photomultiplier tube to be detected, consequently enhancing the detection sensitivity. Sulfonamides (SAs) are important antibiotics that achieved great applications in many fields. However, they pose a serious threat on the environment and human health when they enter into the environment. The SDW-ICOF-LED-IFD-CE system was used to determine fluorescein isothiocyanate (FITC)-labeled sulfadoxine (SDM), sulfaguanidine (SGD) and sulfamonomethoxine sodium (SMM-Na) in environmental water. The detection results obtained by the SDW-ICOF-LED-IFD-CE system were compared to those acquired by the CE with in-capillary optical fiber light-emitting diode-induced fluorescence detection (ICOF-LED-IFD-CE). The limits of detection (LODs) of SDW-ICOF-LED-IFD-CE and ICOF-LED-IFD-CE were 1.0-2.0 nM and 2.5-7.7 nM (S/N = 3), respectively. The intraday (n = 6) and interday (n = 6) precision of migration time and corresponding peak area for both types of CE were all less than 0.86% and 3.68%, respectively. The accuracy of the proposed method was judged by employing standard addition method, and recoveries obtained were in the range of 92.5-102.9%. The results indicated that the sensitivity of the SDW-ICOF-LED-IFD-CE system was improved, and that its reproducibility and accuracy were satisfactory. It was successfully applied to analyze SAs in environmental water. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

None, None

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

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

NASA Astrophysics Data System (ADS)

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.

Low cost batch fabrication of microdevices using ultraviolet light-emitting diode photolithography technique

NASA Astrophysics Data System (ADS)

Lee, Neam Heng; Swamy, Varghese; Ramakrishnan, Narayanan

2016-01-01

Solid-state technology has enabled the use of light-emitting diodes (LEDs) in lithography systems due to their low cost, low power requirement, and higher efficiency relative to the traditional mercury lamp. Uniform irradiance distribution is essential for photolithography to ensure the critical dimension (CD) of the feature fabricated. However, light illuminated from arrays of LEDs can have nonuniform irradiance distribution, which can be a problem when using LED arrays as a source to batch-fabricate multiple devices on a large wafer piece. In this study, the irradiance distribution of an UV LED array was analyzed, and the separation distance between light source and mask optimized to obtain maximum irradiance uniformity without the use of a complex lens. Further, employing a diffuser glass enhanced the fabrication process and the CD loss was minimized to an average of 300 nm. To assess the performance of the proposed technology, batch fabrication of surface acoustic wave devices on lithium niobate substrate was carried out, and all the devices exhibited identical insertion loss of -18 dB at a resonance frequency of 39.33 MHz. The proposed low-cost UV lithography setup can be adapted in academic laboratories for research and teaching on microdevices.

A wearable infrared video pupillography with multi-stimulation of consistent illumination for binocular pupil response

NASA Astrophysics Data System (ADS)

Mang, Ou-Yang; Ko, Mei Lan; Tsai, Yi-Chun; Chiou, Jin-Chern; Huang, Ting-Wei

2016-03-01

The pupil response to light can reflect various kinds of diseases which are related to physiological health. Pupillary abnormalities may be influenced on people by autonomic neuropathy, glaucoma, diabetes, genetic diseases, and high myopia. In the early stage of neuropathy, it is often asymptomatic and difficulty detectable by ophthalmologists. In addition, the position of injured nerve can lead to unsynchronized pupil response for human eyes. In our study, we design the pupilometer to measure the binocular pupil response simultaneously. It uses the different wavelength of LEDs such as white, red, green and blue light to stimulate the pupil and record the process. Therefore, the pupilometer mainly contains two systems. One is the image acquisition system, it use the two cameras modules with the same external triggered signal to capture the images of the pupil simultaneously. The other one is the illumination system. It use the boost converter ICs and LED driver ICs to supply the constant current for LED to maintain the consistent luminance in each experiments for reduced experimental error. Furthermore, the four infrared LEDs are arranged nearby the stimulating LEDs to illuminate eyes and increase contrast of image for image processing. In our design, we success to implement the function of synchronized image acquisition with the sample speed in 30 fps and the stable illumination system for precise measurement of experiment.

Skin photosensitivity as a model in photodynamic therapy

NASA Astrophysics Data System (ADS)

Richter, Anna M.; Jain, Ashok K.; Canaan, Alice J.; Meadows, Howard; Levy, Julia G.

1996-01-01

Skin photosensitivity is the most common side effect of photodynamic therapy (PDT) and in clinical situations needs to be avoided or at least minimized. However, because of the accessibility of skin tissue, skin photosensitivity represents a useful test system in vivo for evaluation of the pharmacokinetics of photosensitizers and light sources. Pig skin resembles in many aspects human skin and, therefore, is most suitable for these tests. Using pig skin photosensitivity as an end point, we evaluate the effect of cell loading with a photosensitizer, benzoporphyrin derivative (BPD verteporfin) following its intravenous administration either as a rapid bolus or slow infusion. Skin response to light activation indicated a very similar cell content of BPD. These results were in agrement with those obtained in an in vitro model. In addition, in the same pig skin photosensitivity model we compared the efficiency of activation of BPD with either laser (690 plus or minus 3 nm) or light-emitting diode (LED; 690 plus or minus 12 nm) light. Results indicated the equivalency of the two light sources in this test system, with LED light being slightly more efficient, due possibly to a fluence rate lower than laser light.

830 nm light-emitting diode low level light therapy (LED-LLLT) enhances wound healing: a preliminary study.

PubMed

Min, Pok Kee; Goo, Boncheol Leo

2013-01-01

The application of light-emitting diodes in a number of clinical fields is expanding rapidly since the development in the late 1990s of the NASA LED. Wound healing is one field where low level light therapy with LEDs (LED-LLLT) has attracted attention for both accelerating wound healing and controlling sequelae. The present study evaluated LED-LLLT in 5 wounds of various etiologies. There were 5 patients with ages ranging from 7 to 54 years, comprising 2 males and 3 females. The study followed 5 wounds, namely 2 acute excoriation wounds; 1 acute/subacute dog bite with infection; 1 subacute post-filler ulcerated wound with necrotic ischemic tissue and secondary infection; and 1 subacute case of edema and infection of the lips with herpes simplex involvement after an illegal cosmetic tattoo operation. All patients were in varying degrees of pain. All wounds were treated with multiple sessions (daily, every other day or twice weekly) using an LED-LLLT system (830 nm, CW, irradiance of 100 mW/cm(2) and fluence of 60 J/cm(2)) till improvement was achieved. Full wound healing and control of infection and discomfort were achieved in all patients, with wound condition-mediated treatment periods ranging from 1 to 8 weeks. No recurrence of the herpes simplex case was seen in a 4-month follow-up. 830 nm LED-LLLT successfully brought about accelerated healing in wounds of different etiologies and at different stages, and successfully controlled secondary infection. LED-LLLT was easy and pain-free to apply, and was well-tolerated by all patients. The good results warrant the design of controlled studies with a larger patient population.

830 nm light-emitting diode low level light therapy (LED-LLLT) enhances wound healing: a preliminary study

PubMed Central

Min, Pok Kee; Goo, Boncheol Leo

2013-01-01

Background and aims: The application of light-emitting diodes in a number of clinical fields is expanding rapidly since the development in the late 1990s of the NASA LED. Wound healing is one field where low level light therapy with LEDs (LED-LLLT) has attracted attention for both accelerating wound healing and controlling sequelae. The present study evaluated LED-LLLT in 5 wounds of various etiologies. Subjects and methods: There were 5 patients with ages ranging from 7 to 54 years, comprising 2 males and 3 females. The study followed 5 wounds, namely 2 acute excoriation wounds; 1 acute/subacute dog bite with infection; 1 subacute post-filler ulcerated wound with necrotic ischemic tissue and secondary infection; and 1 subacute case of edema and infection of the lips with herpes simplex involvement after an illegal cosmetic tattoo operation. All patients were in varying degrees of pain. All wounds were treated with multiple sessions (daily, every other day or twice weekly) using an LED-LLLT system (830 nm, CW, irradiance of 100 mW/cm2 and fluence of 60 J/cm2) till improvement was achieved. Results: Full wound healing and control of infection and discomfort were achieved in all patients, with wound condition-mediated treatment periods ranging from 1 to 8 weeks. No recurrence of the herpes simplex case was seen in a 4-month follow-up. Conclusions: 830 nm LED-LLLT successfully brought about accelerated healing in wounds of different etiologies and at different stages, and successfully controlled secondary infection. LED-LLLT was easy and pain-free to apply, and was well-tolerated by all patients. The good results warrant the design of controlled studies with a larger patient population. PMID:24155549

Improved Heat Dissipation of High-Power LED Lighting by a Lens Plate with Thermally-Conductive Plastics.

PubMed

Lee, Dong Kyu; Park, Hyun Jung; Cha, Yu-Jung; Kim, Hyeong Jin; Kwak, Joon Seop

2018-03-01

The junction temperature of high-power LED lighting was reduced effectively using a lens plate made from a thermally-conductive plastics (TCP). TCP has an excellent thermal conductivity, approximately 5 times that of polymethylmethacrylate (PMMA). Two sets of high-power LED lighting were designed using a multi array LED package with a lens plate for thermal simulation. The difference between two models was the materials of the lens plate. The lens plates of first and second models were fabricated by PMMA (PMMA lighting) and TCP (TCP lighting), respectively. At the lens plate, the simulated temperature of the TCP lighting was higher than that of the PMMA lighting. Near the LED package, the temperature of the TCP lighting was 2 °C lower than that of the PMMA lighting. This was well matched with the measured temperature of the fabricated lighting with TCP and PMMA.

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

Case study describes how the Byron G. Rogers Federal Building replaced existing T12 and T8 luminaires with LED dedicated troffers with advanced controls. Together these measures cut lighting energy use by nearly 60% in the 18-story, 791,000-square-foot facility. The new lighting control system provides automated dimming of lights down to 0% output when daylight provides adequate light levels. The project earned GSA an award for exemplary performance from the Interior Lighting Campaign in 2016.

Low level light therapy by LED of different wavelength induces angiogenesis and improves ischemic wound healing.

PubMed

Dungel, Peter; Hartinger, Joachim; Chaudary, Sidrah; Slezak, Paul; Hofmann, Anna; Hausner, Thomas; Strassl, Martin; Wintner, Ernst; Redl, Heinz; Mittermayr, Rainer

2014-12-01

Low-level light therapy (LLLT) has been revealed as a potential means to improve wound healing. So far, most studies are being performed with irradiation in the red to near-infrared spectra. Recently, we showed that blue light (470 nm) can significantly influence biological systems such as nitric oxide (NO) metabolism and is able to release NO from nitrosyl-hemoglobin or mitochondrial protein complexes. Therefore, the aim of this study was to evaluate and compare the therapeutic value of blue or red light emitting diodes (LEDs) on wound healing in an ischemia disturbed rodent flap model. An abdominal flap was rendered ischemic by ligation of one epigastric bundle and subjected to LED illumination with a wavelength of 470 nm (blue, n = 8) or 629 nm (red, n = 8) each at 50 mW/cm(2) and compared to a non-treated control group (n = 8). Illumination was performed for 10 minutes on five consecutive days. LED therapy with both wavelengths significantly increased angiogenesis in the sub-epidermal layer and intramuscularly (panniculus carnosus muscle) which was associated with significantly improved tissue perfusion 7 days after the ischemic insult. Accordingly, tissue necrosis was significantly reduced and shrinkage significantly less pronounced in the LED-treated groups of both wavelengths. LED treatment of ischemia challenged tissue improved early wound healing by enhancing angiogenesis irrespective of the wavelength thus delineating this noninvasive means as a potential, cost effective tool in complicated wounds. © 2014 Wiley Periodicals, Inc.

LED lamp

DOEpatents

Galvez, Miguel; Grossman, Kenneth; Betts, David

2013-11-12

There is herein described a lamp for providing white light comprising a plurality of light sources positioned on a substrate. Each of said light sources comprises a blue light emitting diode (LED) and a dome that substantially covers said LED. A first portion of said blue light from said LEDs is transmitted through said domes and a second portion of said blue light is converted into a red light by a first phosphor contained in said domes. A cover is disposed over all of said light sources that transmits at least a portion of said red and blue light emitted by said light sources. The cover contains a second phosphor that emits a yellow light in response to said blue light. The red, blue and yellow light combining to form the white light and the white light having a color rendering index (CRI) of at least about 80.

The application of UV LEDs for differential optical absorption spectroscopy

NASA Astrophysics Data System (ADS)

Geiko, Pavel P.; Smirnov, Sergey S.; Samokhvalov, Ignatii V.

2018-04-01

Modern UV LEDs represent a potentially very advantageous alternative to thermal light sources, in particular xenon arc lamps, which are the most common light sources in trace gas-analyzers. So, the light-emitting diodes are very attractive for use of as light sources for Long Path Differential Optical Absorption Spectroscopy (DOAS) measurements of trace gases in the open atmosphere. Recent developments in fibre-coupling telescope technology and the availability of ultraviolet light emitting diodes have now allowed us to construct a portable, long path DOAS instrument for use at remote locations and specifically for measuring degassing from active volcanic systems. First of all, we are talking about the measurement of sulphur dioxide, carbon disulphide and, oxides of chlorine and bromine. The parallel measurements of sulfur dioxide using a certified gas analyzer, were conducted and showed good correlation.

Significant growth in. LED use predicted.

PubMed

Simpson, Mike

2012-03-01

Although LED lighting has its critics, a number of whom (see article 'LED--panacea or marketing hype', HEJ--February 2012) are concerned about what they claim are some manufacturers' 'exaggerated claims' about lighting efficiency and lamp lifetime, Philips Lighting believes that, such are the advances being made in this innovative lighting technology, that LED's overall share of the European lighting market will have risen from around 7% in 2008 to 25% by 2020 and that, a decade later, it will account for a remarkable 75% of lighting sales. In the UK, Philips' technical and design director for Lighting, Mike Simpson, told HEJ editor, Jonathan Baillie, healthcare estates and facilities managers are increasingly recognising the potential to save energy, reduce carbon emissions, and cut maintenance costs, using LED.

Complete solid state lighting (SSL) line at CEA LETI

NASA Astrophysics Data System (ADS)

Robin, I. C.; Ferret, P.; Dussaigne, A.; Bougerol, C.; Salomon, D.; Chen, X. J.; Charles, M.; Tchoulfian, P.; Gasse, A.; Lagrange, A.; Consonni, M.; Bono, H.; Levy, F.; Desieres, Y.; Aitmani, A.; Makram-Matta, S.; Bialic, E.; Gorrochategui, P.; Mendizabal, L.

2014-09-01

With a long experience in optoelectronics, CEA-LETI has focused on Light Emitting Diode (LED) lighting since 2006. Today, all the technical challenges in the implementation of GaN LED based solid state lighting (SSL) are addressed at CEA-LETI who is now an RandD player throughout the entire value chain of LED lighting. The SSL Line at CEA-LETI first deals with the simulation of the active structures and LED devices. Then the growth is addressed in particular 2D growth on 200 mm silicon substrates. Then, technological steps are developed for the fabrication of LED dies with innovative architectures. For instance, Versatile LED Array Devices are currently being developed with a dedicated μLED technology. The objective in this case is to achieve monolithical LED arrays reported and interconnected through a silicon submount. In addition to the required bonding and 3D integration technologies, new solutions for LED chip packaging, thermal management of LED lamps and luminaires are also addressed. LETI is also active in Smart Lighting concepts which offer the possibility of new application fields for SSL technologies. An example is the recent development at CEA LETI of Visible Light Communication Technology also called LiFi. With this technology, we demonstrated a transmission rate up to 10 Mb/s and real time HD-Video transmission.

[Methodological approaches to the hygienic evaluation of total artificial lighting of classrooms with different light sources on the basis of the response of the cardiovascular system of schoolchildren].

PubMed

Teksheva, L M; Zvezdina, I V

2014-01-01

Hygienic evaluation of innovative equipment in educational institutions requires the use of appropriate methods permitting to establish valuable criterias for the effectiveness of the application of new technologies. The study of the response of the cardiovascular system of schoolchildren under using different light sources allowed to establish the increase in adaptive capacities and the improvement of the functional state of the organism in LED in comparison with fluorescent lighting.

Enhanced light extraction from a GaN-based green light-emitting diode with hemicylindrical linear grating structure.

PubMed

Jin, Yuanhao; Yang, Fenglei; Li, Qunqing; Zhu, Zhendong; Zhu, Jun; Fan, Shoushan

2012-07-02

Significant enhancement in the light output from GaN-based green light-emitting diodes (LEDs) was achieved with a hemicylindrical grating structure on the top layer of the diodes. The grating structure was first optimized by the finite-difference time-domain (FDTD) method, which showed that the profile of the grating structure was critical for light extraction efficiency. It was found that the transmission efficiency of the 530 nm light emitted from the inside of the GaN LED increased for incidence angles between 23.58° and 60°. Such a structure was fabricated by electron-beam lithography and an etching method. The light output power from the LED was increased approximately 4.7 times compared with that from a conventional LED. The structure optimization is the key to the great increase in transmission efficiency. Furthermore, the light emitted from the edge of the LED units could be collected and extracted by the grating structures in adjacent LED units, thus enhancing the performance of the whole LED chip.

Light-Emitting Diodes and Cool White Fluorescent Light Similarly Suppress Pineal Gland Melatonin and Maintain Retinal Function and Morphology in the Rat. Part 1

NASA Technical Reports Server (NTRS)

Holley, Daniel C.; Heeke, D.; Mele, G.

1999-01-01

Currently, the light sources most commonly used in animal habitat lighting are cool white fluorescent or incandescent lamps. We evaluated a novel light-emitting diode (LED) light source for use in animal habitat lighting by comparing its effectiveness to cool white fluorescent light (CWF) in suppressing pineal gland melatonin and maintaining normal retinal physiology and morphology in the rat. Results of pineal melatonin suppression experiments showed equal suppression of pineal melatonin concentrations for LED light and CWF light at five different light illuminances (100, 40, 10, 1 and 0.1 lux). There were no significant differences in melatonin suppression between LED and CWF light when compared to unexposed controls. Retinal physiology was evaluated using electroretinography. Results show no differences in a-wave implicit times and amplitudes or b-wave implicit times and amplitudes between 100-lux LED-exposed rats and 100-lux CWF-exposed rats. Results of retinal histology assessment show no differences in retinal thickness rod outer segment length and number of rod nuclei between rats exposed to 100-lux LED and 100-lux CWF for days. Furthermore, the retinal pigmented epithelium and rod outer segments of all eyes observed were in good condition and of normal thickness. This study indicates that LED light does not cause retinal damage and can suppress pineal melatonin at similar intensities as a conventional CWF light source. These data suggest that LED light sources may be suitable replacements for conventional light sources used in the lighting of rodent vivariums while providing many mechanical and economical advantages.

Efficient calculation of luminance variation of a luminaire that uses LED light sources

NASA Astrophysics Data System (ADS)

Goldstein, Peter

2007-09-01

Many luminaires have an array of LEDs that illuminate a lenslet-array diffuser in order to create the appearance of a single, extended source with a smooth luminance distribution. Designing such a system is challenging because luminance calculations for a lenslet array generally involve tracing millions of rays per LED, which is computationally intensive and time-consuming. This paper presents a technique for calculating an on-axis luminance distribution by tracing only one ray per LED per lenslet. A multiple-LED system is simulated with this method, and with Monte Carlo ray-tracing software for comparison. Accuracy improves, and computation time decreases by at least five orders of magnitude with this technique, which has applications in LED-based signage, displays, and general illumination.

Efficient perovskite light-emitting diodes featuring nanometre-sized crystallites

NASA Astrophysics Data System (ADS)

Xiao, Zhengguo; Kerner, Ross A.; Zhao, Lianfeng; Tran, Nhu L.; Lee, Kyung Min; Koh, Tae-Wook; Scholes, Gregory D.; Rand, Barry P.

2017-01-01

Organic-inorganic hybrid perovskite materials are emerging as highly attractive semiconductors for use in optoelectronics. In addition to their use in photovoltaics, perovskites are promising for realizing light-emitting diodes (LEDs) due to their high colour purity, low non-radiative recombination rates and tunable bandgap. Here, we report highly efficient perovskite LEDs enabled through the formation of self-assembled, nanometre-sized crystallites. Large-group ammonium halides added to the perovskite precursor solution act as a surfactant that dramatically constrains the growth of 3D perovskite grains during film forming, producing crystallites with dimensions as small as 10 nm and film roughness of less than 1 nm. Coating these nanometre-sized perovskite grains with longer-chain organic cations yields highly efficient emitters, resulting in LEDs that operate with external quantum efficiencies of 10.4% for the methylammonium lead iodide system and 9.3% for the methylammonium lead bromide system, with significantly improved shelf and operational stability.

Solution-Grown ZnO Films toward Transparent and Smart Dual-Color Light-Emitting Diode.

PubMed

Huang, Xiaohu; Zhang, Li; Wang, Shijie; Chi, Dongzhi; Chua, Soo Jin

2016-06-22

An individual light-emitting diode (LED) capable of emitting different colors of light under different bias conditions not only allows for compact device integration but also extends the functionality of the LED beyond traditional illumination and display. Herein, we report a color-switchable LED based on solution-grown n-type ZnO on p-GaN/n-GaN heterojunction. The LED emits red light with a peak centered at ∼692 nm and a full width at half-maximum of ∼90 nm under forward bias, while it emits green light under reverse bias. These two lighting colors can be switched repeatedly by reversing the bias polarity. The bias-polarity-switched dual-color LED enables independent control over the lighting color and brightness of each emission with two-terminal operation. The results offer a promising strategy toward transparent, miniaturized, and smart LEDs, which hold great potential in optoelectronics and optical communication.

Integrated LED-based luminaire for general lighting

DOEpatents

Dowling, Kevin J.; Lys, Ihor A.; Williamson, Ryan C.; Roberge, Brian; Roberts, Ron; Morgan, Frederick; Datta, Michael Jay; Mollnow, Tomas Jonathan

2016-08-30

Lighting apparatus and methods employing LED light sources are described. The LED light sources are integrated with other components in the form of a luminaire or other general purpose lighting structure. Some of the lighting structures are formed as Parabolic Aluminum Reflector (PAR) luminaires, allowing them to be inserted into conventional sockets. The lighting structures display beneficial operating characteristics, such as efficient operation, high thermal dissipation, high output, and good color mixing.

Integrated LED-based luminare for general lighting

DOEpatents

Dowling, Kevin J.; Lys, Ihor A.; Roberge, Brian; Williamson, Ryan C.; Roberts, Ron; Datta, Michael; Mollnow, Tomas; Morgan, Frederick M.

2013-03-05

Lighting apparatus and methods employing LED light sources are described. The LED light sources are integrated with other components in the form of a luminaire or other general purpose lighting structure. Some of the lighting structures are formed as Parabolic Aluminum Reflector (PAR) luminaires, allowing them to be inserted into conventional sockets. The lighting structures display beneficial operating characteristics, such as efficient operation, high thermal dissipation, high output, and good color mixing.

Fully porous GaN p-n junction diodes fabricated by chemical vapor deposition.

PubMed

Bilousov, Oleksandr V; Carvajal, Joan J; Geaney, Hugh; Zubialevich, Vitaly Z; Parbrook, Peter J; Martínez, Oscar; Jiménez, Juan; Díaz, Francesc; Aguiló, Magdalena; O'Dwyer, Colm

2014-10-22

Porous GaN based LEDs produced by corrosion etching techniques demonstrated enhanced light extraction efficiency in the past. However, these fabrication techniques require further postgrown processing steps, which increases the price of the final system. Also, the penetration depth of these etching techniques is limited, and affects not only the semiconductor but also the other elements constituting the LED when applied to the final device. In this paper, we present the fabrication of fully porous GaN p-n junctions directly during growth, using a sequential chemical vapor deposition (CVD) process to produce the different layers that form the p-n junction. We characterized their diode behavior from room temperature to 673 K and demonstrated their ability as current rectifiers, thus proving the potential of these fully porous p-n junctions for diode and LEDs applications. The electrical and luminescence characterization confirm that high electronic quality porous structures can be obtained by this method, and we believe this investigation can be extended to other III-N materials for the development of white light LEDs, or to reduce reflection losses and narrowing the output light cone for improved LED external quantum efficiencies.

Tools for controlling protein interactions with light

PubMed Central

Tucker, Chandra L.; Vrana, Justin D.; Kennedy, Matthew J.

2014-01-01

Genetically-encoded actuators that allow control of protein-protein interactions with light, termed ‘optical dimerizers’, are emerging as new tools for experimental biology. In recent years, numerous new and versatile dimerizer systems have been developed. Here we discuss the design of optical dimerizer experiments, including choice of a dimerizer system, photoexcitation sources, and coordinate use of imaging reporters. We provide detailed protocols for experiments using two dimerization systems we previously developed, CRY2/CIB and UVR8/UVR8, for use controlling transcription, protein localization, and protein secretion with light. Additionally, we provide instructions and software for constructing a pulse-controlled LED light device for use in experiments requiring extended light treatments. PMID:25181301

Indoor positioning algorithm combined with angular vibration compensation and the trust region technique based on received signal strength-visible light communication

NASA Astrophysics Data System (ADS)

Wang, Jin; Li, Haoxu; Zhang, Xiaofeng; Wu, Rangzhong

2017-05-01

Indoor positioning using visible light communication has become a topic of intensive research in recent years. Because the normal of the receiver always deviates from that of the transmitter in application, the positioning systems which require that the normal of the receiver be aligned with that of the transmitter have large positioning errors. Some algorithms take the angular vibrations into account; nevertheless, these positioning algorithms cannot meet the requirement of high accuracy or low complexity. A visible light positioning algorithm combined with angular vibration compensation is proposed. The angle information from the accelerometer or other angle acquisition devices is used to calculate the angle of incidence even when the receiver is not horizontal. Meanwhile, a received signal strength technique with high accuracy is employed to determine the location. Moreover, an eight-light-emitting-diode (LED) system model is provided to improve the accuracy. The simulation results show that the proposed system can achieve a low positioning error with low complexity, and the eight-LED system exhibits improved performance. Furthermore, trust region-based positioning is proposed to determine three-dimensional locations and achieves high accuracy in both the horizontal and the vertical components.

LED roadway lighting, volume 2 : field evaluations and software comparisons.

DOT National Transportation Integrated Search

2012-10-01

The use of light-emitting diodes (LEDs) for roadway lighting can potentially save energy costs and reduce the frequency of maintenance. The objective of this study is to explore the current state of the art in LED roadway lighting technology. Three s...

Solid-state lighting life prediction using extended Kalman filter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lall, Pradeep; Wei, Junchao; Davis, Lynn

2013-07-16

Solid-state lighting (SSL) luminaires containing light emitting diodes (LEDs) have the potential of seeing excessive temperatures when being transported across country or being stored in non-climate controlled warehouses. They are also being used in outdoor applications in desert environments that see little or no humidity but will experience extremely high temperatures during the day. This makes it important to increase our understanding of what effects high temperature exposure for a prolonged period of time will have on the usability and survivability of these devices. The U.S. Department of Energy has made a long term commitment to advance the efficiency, understandingmore » and development of solid-state lighting (SSL) and is making a strong push for the acceptance and use of SSL products to reduce overall energy consumption attributable to lighting. Traditional light sources “burn out” at end-of-life. For an incandescent bulb, the lamp life is defined by B50 life. However, the LEDs have no filament to “burn”. The LEDs continually degrade and the light output decreases eventually below useful levels causing failure. Presently, the TM-21 test standard is used to predict the L70 life of SSL Luminaires from LM-80 test data. The TM-21 model uses an Arrhenius Equation with an Activation Energy, Pre-decay factor and Decay Rates. Several failure mechanisms may be active in a luminaire at a single time causing lumen depreciation. The underlying TM-21 Arrhenius Model may not capture the failure physics in presence of multiple failure mechanisms. Correlation of lumen maintenance with underlying physics of degradation at system-level is needed. In this paper, a Kalman Filter and Extended Kalman Filters have been used to develop a 70% Lumen Maintenance Life Prediction Model for a LEDs used in SSL luminaires. This model can be used to calculate acceleration factors, evaluate failure-probability and identify ALT methodologies for reducing test time. Ten-thousand hour LM-80 test data for various LEDs have been used for model development. System state has been described in state space form using the measurement of the feature vector, velocity of feature vector change and the acceleration of the feature vector change. System state at each future time has been computed based on the state space at preceding time step, system dynamics matrix, control vector, control matrix, measurement matrix, measured vector, process noise and measurement noise. The future state of the lumen depreciation has been estimated based on a second order Kalman Filter model and a Bayesian Framework. The measured state variable has been related to the underlying damage using physics-based models. Life prediction of L70 life for the LEDs used in SSL luminaires from KF and EKF based models have been compared with the TM-21 model predictions and experimental data.« less

Multispectral photoacoustic characterization of ICG and porcine blood using an LED-based photoacoustic imaging system

NASA Astrophysics Data System (ADS)

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

2018-02-01

Photoacoustic imaging is a hybrid biomedical imaging modality that has emerged over the last decade. In photoacoustic imaging, pulsed-light absorbed by the target emits ultrasound that can be detected using a conventional ultrasound array. This ultrasound data can be used to reconstruct the location and spatial details of the intrinsic/extrinsic light absorbers in the tissue. Recently we reported on the development of a multi-wavelength high frame-rate LED-based photoacoustic/ultrasound imaging system (AcousticX). In this work, we photoacoustically characterize the absorption spectrum of ICG and porcine blood using LED arrays with multiple wavelengths (405, 420, 470, 520, 620, 660, 690, 750, 810, 850, 925, 980 nm). Measurements were performed in a simple reflection mode configuration in which LED arrays where fixed on both sides of the linear array ultrasound probe. Phantom used consisted of micro-test tubes filled with ICG and porcine blood, which were placed in a tank filled with water. The photoacoustic spectrum obtained from our measurements matches well with the reference absorption spectrum. These results demonstrate the potential capability of our system in performing clinical/pre-clinical multispectral photoacoustic imaging.

A portable fluorescent sensing system using multiple LEDs

NASA Astrophysics Data System (ADS)

Shin, Young-Ho; Barnett, Jonathan Z.; Gutierrez-Wing, M. Teresa; Rusch, Kelly A.; Choi, Jin-Woo

2017-02-01

This paper presents a portable fluorescent sensing system that utilizes different light emitting diode (LED) excitation lights for multiple target detection. In order to identify different analytes, three different wavelengths (385 nm, 448 nm, and 590 nm) of excitation light emitting diodes were used to selectively stimulate the target analytes. A highly sensitive silicon photomultiplier (SiPM) was used to detect corresponding fluorescent signals from each analyte. Based on the unique fluorescent response of each analyte, it is possible to simultaneously differentiate one analyte from the other in a mixture of target analytes. A portable system was designed and fabricated consisting of a display module, battery, data storage card, and sample loading tray into a compact 3D-printed jig. The portable sensor system was demonstrated for quantification and differentiation of microalgae (Chlorella vulgaris) and cyanobacteria (Spirulina) by measuring fluorescent responses of chlorophyll a in microalgae and phycocyanin in cyanobacteria. Obtained results suggest that the developed portable sensor system could be used as a generic fluorescence sensor platform for on-site detection of multiple analytes of interest.

The effect of 580 nm-based-LED mixed light on growth, adipose deposition, skeletal development, and body temperature of chickens.

PubMed

Yang, Yefeng; Zhen, Chenghuang; Yang, Bo; Yu, Yonghua; Pan, Jinming

2018-06-01

Though previous study indicated that the 580 nm-yellow-LED-light showed an stimulating effect on growth of chickens, the low luminous efficiency of the yellow LED light cannot reflect the advantage of energy saving. In present study, the cool white LED chips and yellow LED chips have been combined to fabricate the white × yellow mixed LED light, with an enhanced luminous efficiency. A total 300 newly hatched chickens were reared under various mixed LED light. The results indicated that the white × yellow mixed LED light had "double-edged sword" effects on bird's body weight, bone development, adipose deposition, and body temperature, depending on variations in ratios of yellow component. Low yellow ratio of mixed LED light (Low group) inhibited body weight, whereas medium and high yellow ratio of mixed LED light (Medium and High groups) promoted body weight, compared with white LED light (White group). A progressive change in yellow component gave rise to consistent changes in body weight over the entire experiment. Moreover, a positive relationship was observed between yellow component and feed conversion ratio. High group-treated birds had greater relative abdominal adipose weight than Medium group-treated birds (P = 0.048), whereas Medium group-treated birds had greater relative abdominal adipose weight than Low group-treated birds (P = 0.044). We found that mixed light improved body weight by enhancing skeletal development (R 2  = 0.5023, P = 0.0001) and adipose deposition (R 2  = 0.6012, P = 0.0001). Birds in the Medium, High and Yellow groups attained significantly higher surface temperatures compared with the White group (P = 0.010). The results suggest that the application of the mixed light with high level of yellow component can be used successfully to improve growth and productive performance in broilers. Copyright © 2018. Published by Elsevier B.V.

Multicolor white light-emitting diodes for illumination applications

NASA Astrophysics Data System (ADS)

Chi, Solomon W. S.; Chen, Tzer-Perng; Tu, Chuan-Cheng; Chang, Chih-Sung; Tsai, Tzong-Liang; Hsieh, Mario C. C.

2004-01-01

Semiconductor light emitting diode (LED) has become a promising device for general-purpose illumination applications. LED has the features of excellent durability, long operation life, low power consumption, no mercury containing and potentially high efficiency. Several white LED technologies appear capable of meeting the technical requirements of illumination. In this paper we present a new multi-color white (MCW) LED as a high luminous efficacy, high color rendering index and low cost white illuminator. The device consists of two LED chips, one is AlInGaN LED for emitting shorter visible spectra, another is AlInGaP LED for emitting longer visible spectra. At least one chip in the MCW-LED has two or more transition energy levels used for emitting two or more colored lights. The multiple colored lights generated from the MCW-LED can be mixed into a full-spectral white light. Besides, there is no phosphors conversion layer used in the MCW-LED structure. Therefore, its color rendering property and illumination efficiency are excellent. The Correlated Color Temperature (CCT) of the MCW-LED may range from 2,500 K to over 10,000 K. The theoretical General Color Rendering Index (Ra) could be as high as 94, which is close to the incandescent and halogen sources, while the Ra of binary complementary white (BCW) LED is about 30 ~ 45. Moreover, compared to the expensive ternary RGB (Red AlInGaP + Green AlInGaN + Blue AlInGaN) white LED sources, the MCW-LED uses only one AlInGaN chip in combination with one cheap AlInGaP chip, to form a low cost, high luminous performance white light source. The MCW-LED is an ideal light source for general-purpose illumination applications.

The Switch from Low-Pressure Sodium to Light Emitting Diodes Does Not Affect Bat Activity at Street Lights

PubMed Central

Rowse, Elizabeth G.; Harris, Stephen; Jones, Gareth

2016-01-01

We used a before-after-control-impact paired design to examine the effects of a switch from low-pressure sodium (LPS) to light emitting diode (LED) street lights on bat activity at twelve sites across southern England. LED lights produce broad spectrum ‘white’ light compared to LPS street lights that emit narrow spectrum, orange light. These spectral differences could influence the abundance of insects at street lights and thereby the activity of the bats that prey on them. Most of the bats flying around the LPS lights were aerial-hawking species, and the species composition of bats remained the same after the switch-over to LED. We found that the switch-over from LPS to LED street lights did not affect the activity (number of bat passes), or the proportion of passes containing feeding buzzes, of those bat species typically found in close proximity to street lights in suburban environments in Britain. This is encouraging from a conservation perspective as many existing street lights are being, or have been, switched to LED before the ecological consequences have been assessed. However, lighting of all spectra studied to date generally has a negative impact on several slow-flying bat species, and LED lights are rarely frequented by these ‘light-intolerant’ bat species. PMID:27008274

The design of a wireless batteryless biflash installation with high power LEDs

NASA Astrophysics Data System (ADS)

Cappelle, J.; De Geest, W.; Hanselaer, P.

2011-05-01

Adding flashlights at crosswalks may make these weak traffic points safer. Unfortunately plugging in traffic lights into the electrical grid is expensive and complex. This paper reports about the energetic, the electronic and the optical design and building of a wireless and batteryless biflash installation in the framework of a flemish SME supporting program. The energy is supplied by a small solar panel and is buffered by supercapacitors instead of batteries. This has the advantage of being maintenance free: the number of charge-discharge cycles is almost unlimited because there is no chemical reaction involved in the storage mechanism. On the other hand the limited energy storage capacity of supercapacitors requires a new approach for the system design. Based on the EN-12352 standard for warning light devices, all design choices were filled in to be as energy efficient as possible. The duty cycle and the light output of the high power led flashlights are minimized. The components for the electronic circuits for the led driver, the control and the RF communication are selected based on their energy consumption and power management techniques are implemented. A lot of energy is saved by making the biflash system active. The leds are only flashing on demand or at preprogrammed moments. A biflash installation is typically installed at both sides of a crosswalk. A call at one of the sides should result in flashing at both sides. To maintain the drag and drop principle, a wireless RF communication system is designed.

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

DTIC Science & Technology

2017-11-01

sent from light-emitting diodes (LEDs) of 5 colors ( green , red, white, amber, and blue). Experiment 1 involved controlled laboratory measurements of...A-4 Red LED calibration curves and quadratic curve fits with R2 values . 37 Fig. A-5 Green LED calibration curves and quadratic curve fits with R2...36 Table A-4 Red LED calibration measurements ................................................... 36 Table A-5 Green LED

Reshaping Light-Emitting Diodes To Increase External Efficiency

NASA Technical Reports Server (NTRS)

Rogowski, Robert; Egalon, Claudio

1995-01-01

Light-emitting diodes (LEDs) reshaped, according to proposal, increasing amount of light emitted by decreasing fraction of light trapped via total internal reflection. Results in greater luminous output power for same electrical input power; greater external efficiency. Furthermore, light emitted by reshaped LEDs more nearly collimated (less diffuse). Concept potentially advantageous for conventional red-emitting LEDs. More advantageous for new "blue" LEDs, because luminous outputs and efficiencies of these devices very low. Another advantage, proposed conical shapes achieved relatively easily by chemical etching of semiconductor surfaces.

R&D100: LED Pulser

ScienceCinema

Pickett, Lyle; Manin, Julien; Eagle, Ethan

2018-06-12

A Sandia National Laboratories' light emitting diode (LED) driver is generating light pulses with shorter duration higher repetition frequency and higher brightness than anything on the market. The Sandia LED Pulser uses custom electronic circuitry to drive high-power LEDs to generate short, bright, high frequency light pulses. A single device can emit up to four different colors - each with independent pulse timing - crucial for light-beam forming in many optical applications and is more economical than current light sources such as lasers.

Pulp chamber temperature rise during curing of resin-based composites with different light-curing units.

PubMed

Durey, Kathryn; Santini, Ario; Miletic, Vesna

2008-01-01

The purpose of the present study was to measure the intrapulpal temperature rise occurring during polymerisation of different shades of resin-based composites (RBCs), and two light-emitting diode (LED) units. Seventy non-carious permanent molars, that had been extracted for orthodontic purposes and stored in 2% thymol for not more than four months, were selected. Patient age range was 11-18 years. Standard cavity preparation with standardised remaining dentine thickness and placement of thermocouples (TCs) was prepared using a novel split-tooth technique. Cavities were filled with one of two shades of RBC (A2 and C4, Filtek Z250, 3M ESPE, Seefeld, Germany), and cured with two LED high-intensity units (Elipar Freelight2, 3M ESPE, Seefeld, Germany; Bluephase, Ivoclar Vivadent, Schaan, Liechtenstein) and a conventional halogen light-curing unit (LCU) (Prismetics Lite 2, Dentsply, Weybridge, Surrey, UK) as a control. Pulp temperature rises during bonding [A2 results: H;2.67/0.48:E;5.24/1.32;B;5.99/1.61] were always greater than during RBC curing [A2 results: 2.44/0.63;E3.34/0.70;B3.38/0.60], and these were significant for both LED lights but not for the halogen control, irrespective of shade (Mann-Whitney test: 95% confidence limits). Temperature rises were at times in excess of the values normally quoted as causing irreversible pulp damage. Pulp temperature rises during bonding were higher with the LED lights than with the halogen control. There was no significant difference in temperature rise between the two LED lights when bonding but there was a significant difference between the two LED lights and the halogen control LCUs (Kruskal-Wallis Test: 95% confidence limits). The results support the view that there is a potential risk for heat-induced pulpal injury when light-curing RBCs. The risk is greater during bonding and with high energy, as compared to low-energy output systems. As the extent of tolerable thermal trauma by the pulp tissues is unknown, care and consideration should be given to the choice of LCU and the exposure time when curing RBCs, and especially during bonding.

Optical sectioning microscopes with no moving parts using a micro-stripe array light emitting diode.

PubMed

Poher, V; Zhang, H X; Kennedy, G T; Griffin, C; Oddos, S; Gu, E; Elson, D S; Girkin, M; French, P M W; Dawson, M D; Neil, M A

2007-09-03

We describe an optical sectioning microscopy system with no moving parts based on a micro-structured stripe-array light emitting diode (LED). By projecting arbitrary line or grid patterns onto the object, we are able to implement a variety of optical sectioning microscopy techniques such as grid-projection structured illumination and line scanning confocal microscopy, switching from one imaging technique to another without modifying the microscope setup. The micro-structured LED and driver are detailed and depth discrimination capabilities are measured and calculated.

Solution of multi-element LED light sources development automation problem

NASA Astrophysics Data System (ADS)

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.

Essentials for Successful and Widespread LED Lighting Adoption

NASA Astrophysics Data System (ADS)

Khan, Nisa

2011-03-01

Solid-state lighting (SSL), with light-emitting diodes (LEDs) as the light source, is a growing and essential field, particularly in regard to the heightened need for global energy efficiency. In recent years, SSL has experienced remarkable advances in efficiency, light output magnitude and quality. Thus such diverse applications as signage, message centers, displays, and special lighting are now adopting LEDs, taking 2010's market to 9.1 billion - 68% growth from the previous year! While this is promising, future growth in both display and lighting applications will rely upon unveiling deeper understanding and key innovations in LED lighting science and technologies. In this presentation, some LED lighting fundamentals, engineering challenges and novel solutions will be discussed to address reduction in efficiency (a.k.a. droop) at high currents, and to obtain uniform light distribution for overcoming LEDs' directional nature. The droop phenomenon has been a subject of much controversy in the industry and despite several studies and claims, a widely-accepted explanation still lacks because of counter arguments and experiments. Recently several research studies have identified that the droop behavior in nitride-based LEDs beyond certain current density ranges can only be comprehensively explained if the current leaking beyond the LED active region is included. Although such studies have identified a few useful current leakage mechanisms outside the active region, no one has included current leakage, due to non-ideal, 3-D device structures that create undesirable current distribution inside and outside the active region. This talk will address achieving desirable current distributions from optimized 3-D device structures that should reduce current leakage and hence the droop behavior. In addition to novel LED design solutions for droop reduction and uniform light distribution, the talk will address cost and yield concerns as they pertain to core material scarcity. Such solutions are expected to make LED lights more energy efficient, pleasant in appearance, longer-lasting, affordable, and thus suitable for green living.

Thioredoxin f1 and NADPH-Dependent Thioredoxin Reductase C Have Overlapping Functions in Regulating Photosynthetic Metabolism and Plant Growth in Response to Varying Light Conditions.

PubMed

Thormählen, Ina; Meitzel, Tobias; Groysman, Julia; Öchsner, Alexandra Bianca; von Roepenack-Lahaye, Edda; Naranjo, Belén; Cejudo, Francisco J; Geigenberger, Peter

2015-11-01

Two different thiol redox systems exist in plant chloroplasts, the ferredoxin-thioredoxin (Trx) system, which depends on ferredoxin reduced by the photosynthetic electron transport chain and, thus, on light, and the NADPH-dependent Trx reductase C (NTRC) system, which relies on NADPH and thus may be linked to sugar metabolism in the dark. Previous studies suggested, therefore, that the two different systems may have different functions in plants. We now report that there is a previously unrecognized functional redundancy of Trx f1 and NTRC in regulating photosynthetic metabolism and growth. In Arabidopsis (Arabidopsis thaliana) mutants, combined, but not single, deficiencies of Trx f1 and NTRC led to severe growth inhibition and perturbed light acclimation, accompanied by strong impairments of Calvin-Benson cycle activity and starch accumulation. Light activation of key enzymes of these pathways, fructose-1,6-bisphosphatase and ADP-glucose pyrophosphorylase, was almost completely abolished. The subsequent increase in NADPH-NADP(+) and ATP-ADP ratios led to increased nitrogen assimilation, NADP-malate dehydrogenase activation, and light vulnerability of photosystem I core proteins. In an additional approach, reporter studies show that Trx f1 and NTRC proteins are both colocalized in the same chloroplast substructure. Results provide genetic evidence that light- and NADPH-dependent thiol redox systems interact at the level of Trx f1 and NTRC to coordinately participate in the regulation of the Calvin-Benson cycle, starch metabolism, and growth in response to varying light conditions. © 2015 American Society of Plant Biologists. All Rights Reserved.

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

PubMed

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 © 2018 Elsevier Ltd. All rights reserved.

Impact of crystal orientation on the modulation bandwidth of InGaN/GaN light-emitting diodes

NASA Astrophysics Data System (ADS)

Monavarian, M.; Rashidi, A.; Aragon, A. A.; Oh, S. H.; Rishinaramangalam, A. K.; DenBaars, S. P.; Feezell, D.

2018-01-01

High-speed InGaN/GaN blue light-emitting diodes (LEDs) are needed for future gigabit-per-second visible-light communication systems. Large LED modulation bandwidths are typically achieved at high current densities, with reports close to 1 GHz bandwidth at current densities ranging from 5 to 10 kA/cm2. However, the internal quantum efficiency (IQE) of InGaN/GaN LEDs is quite low at high current densities due to the well-known efficiency droop phenomenon. Here, we show experimentally that nonpolar and semipolar orientations of GaN enable higher modulation bandwidths at low current densities where the IQE is expected to be higher and power dissipation is lower. We experimentally compare the modulation bandwidth vs. current density for LEDs on nonpolar (10 1 ¯ 0 ), semipolar (20 2 ¯ 1 ¯) , and polar (" separators="|0001 ) orientations. In agreement with wavefunction overlap considerations, the experimental results indicate a higher modulation bandwidth for the nonpolar and semipolar LEDs, especially at relatively low current densities. At 500 A/cm2, the nonpolar LED has a 3 dB bandwidth of ˜1 GHz, while the semipolar and polar LEDs exhibit bandwidths of 260 MHz and 75 MHz, respectively. A lower carrier density for a given current density is extracted from the RF measurements for the nonpolar and semipolar LEDs, consistent with the higher wavefunction overlaps in these orientations. At large current densities, the bandwidth of the polar LED approaches that of the nonpolar and semipolar LEDs due to coulomb screening of the polarization field. The results support using nonpolar and semipolar orientations to achieve high-speed LEDs at low current densities.

Operating scheme for the light-emitting diode array of a volumetric display that exhibits multiple full-color dynamic images

NASA Astrophysics Data System (ADS)

Hirayama, Ryuji; Shiraki, Atsushi; Nakayama, Hirotaka; Kakue, Takashi; Shimobaba, Tomoyoshi; Ito, Tomoyoshi

2017-07-01

We designed and developed a control circuit for a three-dimensional (3-D) light-emitting diode (LED) array to be used in volumetric displays exhibiting full-color dynamic 3-D images. The circuit was implemented on a field-programmable gate array; therefore, pulse-width modulation, which requires high-speed processing, could be operated in real time. We experimentally evaluated the developed system by measuring the luminance of an LED with varying input and confirmed that the system works appropriately. In addition, we demonstrated that the volumetric display exhibits different full-color dynamic two-dimensional images in two orthogonal directions. Each of the exhibited images could be obtained only from the prescribed viewpoint. Such directional characteristics of the system are beneficial for applications, including digital signage, security systems, art, and amusement.

Choosing surgical lighting in the LED era.

PubMed

Knulst, Arjan J; Stassen, Laurents P S; Grimbergen, Cornelis A; Dankelman, Jenny

2009-12-01

The aim of this study is to evaluate the illumination characteristics of LED lights objectively to ease the selection of surgical lighting. The illuminance distributions of 5 main and 4 auxiliary lights were measured in 8 clinically relevant scenarios. For each light and scenario, the maximum illuminance E(c) (klux) and the size of the light field d(10) (mm) were computed. The results showed: that large variations for both E(c) (25-160 klux) and d(10) (109-300 mm) existed; that using auxiliary lights reduced both E(c) and d(10) by up to 80% and 30%; that with segmented lights, uneven light distributions occurred; and that with colored LED lights shadow edges on the surgical field became colored. Objective illuminance measurements show a wide variation between lights and a superiority of main over auxiliary lights. Uneven light distributions and colored shadows indicate that LED lights still need to converge to an optimal design.

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

NASA Astrophysics Data System (ADS)

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

2017-11-01

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

Automated platform for determination of LEDs spatial radiation pattern

NASA Astrophysics Data System (ADS)

Vladescu, Marian; Vuza, Dan Tudor

2015-02-01

Nowadays technologies lead to remarkable properties of the light-emitting diodes (LEDs), making them attractive for more and more applications, such as: interior and exterior lighting, outdoor LED panels, traffic signals, automotive (tail and brake lights, backlighting in dashboard and switches), backlighting of display panels, LCD displays, symbols on switches, keyboards, graphic boards and measuring scales. Usually, LEDs are small light sources consisting of a chip placed into a package, which may bring additional optics to this encapsulated ensemble, resulting in a less or more complex spatial distribution of the light intensity, with particular radiation patterns. This paper presents an automated platform designed to allow a quick and accurate determination of the spatial radiation patterns of LEDs encapsulated in various packages. Keywords: LED, luminous

Evaluation of Metal Halide, Plasma, and LED Lighting Technologies for a Hydrogen Fuel Cell Mobile Light (H 2 LT)

DOE PAGES

Miller, L. B.; Donohoe, S. P.; Jones, M. H.; ...

2015-04-22

This article reports on the testing and comparison of a prototype hydrogen fuel cell light tower (H2LT) and a conventional diesel-powered metal halide light trailer for use in road maintenance and construction activities. The prototype was originally outfitted with plasma lights and then with light-emitting diode (LED) luminaires. Light output and distribution, lighting energy efficiency (i.e., efficacy), power source thermal efficiency, and fuel costs are compared. The metal halide luminaires have 2.2 and 3.1 times more light output than the plasma and LED luminaires, respectively, but they require more power/lumen to provide that output. The LED luminaires have 1.6 timesmore » better light efficacy than either the metal halide or plasma luminaires. The light uniformity ratios produced by the plasma and LED towers are acceptable. The fuel cell thermal efficiency at the power required to operate the plasma lights is 48%, significantly higher than the diesel generator efficiency of 23% when operating the metal halide lights. Due to the increased efficiency of the fuel cell and the LED lighting, the fuel cost per lumen-hour of the H2LT is 62% of the metal halide diesel light tower assuming a kilogram of hydrogen is twice the cost of a gallon of diesel fuel.« less

Pupil light reflex evoked by light-emitting diode and computer screen: Methodology and association with need for recovery in daily life.

PubMed

Wang, Yang; Zekveld, Adriana A; Wendt, Dorothea; Lunner, Thomas; Naylor, Graham; Kramer, Sophia E

2018-01-01

Pupil light reflex (PLR) has been widely used as a method for evaluating parasympathetic activity. The first aim of the present study is to develop a PLR measurement using a computer screen set-up and compare its results with the PLR generated by a more conventional setup using light-emitting diode (LED). The parasympathetic nervous system, which is known to control the 'rest and digest' response of the human body, is considered to be associated with daily life fatigue. However, only few studies have attempted to test the relationship between self-reported daily fatigue and physiological measurement of the parasympathetic nervous system. Therefore, the second aim of this study was to investigate the relationship between daily-life fatigue, assessed using the Need for Recovery scale, and parasympathetic activity, as indicated by the PLR parameters. A pilot study was conducted first to develop a PLR measurement set-up using a computer screen. PLRs evoked by light stimuli with different characteristics were recorded to confirm the influence of light intensity, flash duration, and color on the PLRs evoked by the system. In the subsequent experimental study, we recorded the PLR of 25 adult participants to light flashes generated by the screen set-up as well as by a conventional LED set-up. PLR parameters relating to parasympathetic and sympathetic activity were calculated from the pupil responses. We tested the split-half reliability across two consecutive blocks of trials, and the relationships between the parameters of PLRs evoked by the two set-ups. Participants rated their need for recovery prior to the PLR recordings. PLR parameters acquired in the screen and LED set-ups showed good reliability for amplitude related parameters. The PLRs evoked by both set-ups were consistent, but showed systematic differences in absolute values of all parameters. Additionally, higher need for recovery was associated with faster and larger constriction of the PLR. This study assessed the PLR generated by a computer screen and the PLR generated by a LED. The good reliability within set-ups and the consistency between the PLRs evoked by the set-ups indicate that both systems provides a valid way to evoke the PLR. A higher need for recovery was associated with faster and larger constricting PLRs, suggesting increased levels of parasympathetic nervous system activity in people experiencing higher levels of need for recovery on a daily basis.

Visible light communication technology for fine-grained indoor localization

NASA Astrophysics Data System (ADS)

Vieira, M.; Vieira, M. A.; Louro, P.; Fantoni, A.; Vieira, P.

2018-02-01

This paper focuses on designing and analysing a visible light based communication and positioning system. The indoor positioning system uses trichromatic white Light Emitting Diodes (LEDs), both for illumination purposes and as transmitters, and an optical processor, based on a-SiC:H technology, as mobile receiver. On-Off Keying (OOK) modulation scheme is used, proving a good trade-off between system performance and implementation complexity. In the following, the relationship between the transmitted data and the received output levels is decoded. LED bulbs work as transmitters, sending information together with different identifiers, IDs, related to their physical locations. Square and diamond topologies for the unit cell are analyzed, and a 2D localization design, demonstrated by a prototype implementation, is presented. Fine-grained indoor localization is tested. The received signal is used in coded multiplexing techniques for supporting communications and navigation concomitantly on the same channel. The location and motion information is found by mapping the position and estimating the location areas.

Solid state lighting component

DOEpatents

Yuan, Thomas; Keller, Bernd; Ibbetson, James; Tarsa, Eric; Negley, Gerald

2010-10-26

An LED component comprising an array of LED chips mounted on a planar surface of a submount with the LED chips capable of emitting light in response to an electrical signal. The LED chips comprise respective groups emitting at different colors of light, with each of the groups interconnected in a series circuit. A lens is included over the LED chips. Other embodiments can comprise thermal spreading structures included integral to the submount and arranged to dissipate heat from the LED chips.

Solid state lighting component

DOEpatents

Yuan, Thomas; Keller, Bernd; Ibbetson, James; Tarsa, Eric; Negley, Gerald

2015-07-07

An LED component comprising an array of LED chips mounted on a planar surface of a submount with the LED chips capable of emitting light in response to an electrical signal. The LED chips comprise respective groups emitting at different colors of light, with each of the groups interconnected in a series circuit. A lens is included over the LED chips. Other embodiments can comprise thermal spreading structures included integral to the submount and arranged to dissipate heat from the LED chips.

Solid state lighting component

DOEpatents

Keller, Bernd; Ibbetson, James; Tarsa, Eric; Negley, Gerald; Yuan, Thomas

2012-07-10

An LED component comprising an array of LED chips mounted on a planar surface of a submount with the LED chips capable of emitting light in response to an electrical signal. The LED chips comprise respective groups emitting at different colors of light, with each of the groups interconnected in a series circuit. A lens is included over the LED chips. Other embodiments can comprise thermal spreading structures included integral to the submount and arranged to dissipate heat from the LED chips.

LED lighting for use in multispectral and hyperspectral imaging

USDA-ARS?s Scientific Manuscript database

Lighting for machine vision and hyperspectral imaging is an important component for collecting high quality imagery. However, it is often given minimal consideration in the overall design of an imaging system. Tungsten-halogens lamps are the most common source of illumination for broad spectrum appl...

LED deep UV source for charge management of gravitational reference sensors

NASA Astrophysics Data System (ADS)

Sun, Ke-Xun; Allard, Brett; Buchman, Saps; Williams, Scott; Byer, Robert L.

2006-04-01

Proof mass electrical charge management is an important functionality for the ST-7-LTP technology demonstration flight and for LISA. Photoemission for charge control is accomplished by using deep ultraviolet (UV) light to excite photoelectron emission from an Au alloy. The conventional UV source is a mercury vapour lamp. We propose and demonstrate charge management using a deep UV light emitting diode (LED) source. We have acquired selected AlGaN UV LEDs, characterized their performance and successfully used them to realize charge management. The UV LEDs emit at a 257 nm central wavelength with a bandwidth of ~12 nm. The UV power for a free-space LED is ~120 µW, and after fibre coupling is ~16 µW, more than sufficient for LISA applications. We have directly observed the LED UV light-induced photocurrent response from an Au photocathode and an Au-coated GRS/ST-7 proof mass. We demonstrated fast switching of UV LEDs and associated fast changes in photocurrent. This allows modulation and continuous discharge to meet stringent LISA disturbance reduction requirements. We propose and demonstrate AC charge management outside the gravitational wave signal band. Further, the megahertz bandwidth for UV LED switching allows for up to six orders of magnitude dynamic power range and a number of novel modes of operations. The UV LED based charge management system offers the advantages of small-size, lightweight, fibre-coupled operation with very low power consumption. Presented at 'Amaldi6', Poster 73, Space Detector, 6th Edoardo Almadi Conference on Gravitational Waves, 20-24 June 2005.

A comprehensive comparable study of the physiological properties of four microalgal species under different light wavelength conditions.

PubMed

Zhong, Yu; Jin, Peng; Cheng, Jay J

2018-05-19

Microalgae treated with blue light have potential for production of human nutrition supplement and biofuel due to their higher biomass productivity and favorable fatty acid composition. Chlorella vulgaris, Chlorella pyrenoidosa, Scenedesmus quadricauda and Scenedesmus obliquus are representative green microalgae which are widely reported for algal production. In this study, we provide a systematic investigation of the biomass productivity, photosynthetic pigments, chlorophyll fluorescence and fatty acid content of the four green microalgae. The strains were grown in two primary monochromatic light wavelengths [red and blue LEDs (light emitting diode)], and in white LED conditions, respectively. Among them, blue LED light was determined as the best light for growth rate, followed by red LED and white LED. The chlorophyll generation was more sensitive to the monochromatic blue light. The polyunsaturated fatty acids (PUFAs) such as α-linolenic acid (18:3), which were perfect for human nutrition supplementation, showed high concentrations in these algae strains under blue LED. Collectively, the results indicate that the blue LED is suitable for various food, feed, and algal biofuel productions due to both biomass and fatty acid productivity.

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

NASA Astrophysics Data System (ADS)

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

2017-10-01

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

Developing a new supplemental lighting device with ultra-bright white LED for vegetables

NASA Astrophysics Data System (ADS)

Hu, Yongguang; Li, Pingping; Jiang, Jianghai

2007-02-01

It has been proved that monochromatic or compound light-emitting diode (LED) or laser diode (LD) can promote the photosynthesis of horticultural crops, but the promotion of polychromatic light like white LED is unclear. A new type of ultra-bright white LED (LUW56843, InGaN, \

Shelf life of fresh meat products under LED or fluorescent lighting.

PubMed

Steele, K S; Weber, M J; Boyle, E A E; Hunt, M C; Lobaton-Sulabo, A S; Cundith, C; Hiebert, Y H; Abrolat, K A; Attey, J M; Clark, S D; Johnson, D E; Roenbaugh, T L

2016-07-01

Enhanced pork loin chops, beef longissimus lumborum steaks, semimembranosus steaks (superficial and deep portions), ground beef, and ground turkey were displayed under light emitting diode (LED) and fluorescent (FLS) lighting in two multi-shelf, retail display cases with identical operating parameters. Visual and instrumental color, internal product temperature, case temperature, case cycling, thiobarbituric acid reactive substances (TBARS), and Enterobacteriaceae and aerobic plate counts were evaluated. Under LED, beef products (except the deep portion of beef semimembranosus steaks) showed less (P<0.05) visual discoloration. Pork loin chops had higher (P<0.05) L* values for LED lighting. Other than beef longissimus lumborum steaks, products displayed under LED lights had colder internal temperatures than products under FLS lights (P<0.05). Under LED, pork loin chops, ground turkey, and beef semimembranosus steaks had higher (P<0.05) values for TBARS. LED provides colder case and product temperatures, more case efficiency, and extended color life by at least 0.5d for longissimus and semimembranosus steaks; however, some LED cuts showed increased lipid oxidation. Copyright © 2016. Published by Elsevier Ltd.

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

ERIC Educational Resources Information Center

Jackson, David L.; And Others

1985-01-01

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

Design of LED fish lighting attractors using horizontal/vertical LIDC mapping method.

PubMed

Shen, S C; Huang, H J

2012-11-19

This study employs a sub-module concept to develop high-brightness light-emitting diode (HB-LED) fishing light arrays to replace traditional fishing light attractors. The horizontal/vertical (H/V) plane light intensity distribution curve (LIDC) of a LED light source are mapped to assist in the design of a non-axisymmetric lens with a fish-attracting light pattern that illuminates sufficiently large areas and alternates between bright and dark. These LED fishing light attractors are capable of attracting schools of fish toward the perimeter of the luminous zone surrounding fishing boats. Three CT2 boats (10 to 20 ton capacity) were recruited to conduct a field test for 1 y on the sea off the southwestern coast of Taiwan. Field tests show that HB-LED fishing light array installed 5 m above the boat deck illuminated a sea surface of 5 × 12 m and achieved an illuminance of 2000 lx. The test results show that the HB-LED fishing light arrays increased the mean catch of the three boats by 5% to 27%. In addition, the experimental boats consumed 15% to 17% less fuel than their counterparts.

Circadian Behavioral Study: LED vs Cool White Fluorescent - 0.1, 1, 10, 40, 80 lux. Part 2

NASA Technical Reports Server (NTRS)

Holley, Daniel C.; Syrkin, N.; Mele, G.

2000-01-01

Currently, the light source most commonly used in animal habitat lighting is cool white fluorescent (CWF) light. It was the objective of this study to evaluate a novel LED light source for use in animal habitat lighting by comparing its effectiveness to CWF light in producing and maintaining a normal circadian entrainment. The LED and CWF lights had similar spectral power distributions. Sprague-Dawley rats (175-350 g) were kept individually in metabolic cages, under a strict lighting control: 4 days of acclimation at 12:12 LD, 14 days of 12:12 LD, 14 days of 24:0 LD (free-run), and finally 12:12 LD. Food and water were provided ad libitum. Three behavioral parameters were monitored continuously: gross locomotor activity, drinking, and feeding. Combined mean free run periods (tau) were (mean +/- SEM): 24.6 +/- 0.1 and 24.7 +/- 0.2 at 0.1 lux, 25.5 +/- 0.1 and 25.7 +/- 0.1 at 1.0 lux, 25.3 +/- 0.2 and 25.4 +/- 0.2 at 10 lux, 25.8 +/- 0.1 and 25.9 +/- 0.1 at 40 lux, and 25.9 +/- 0.1 and 25.9 +/- 0.1 at 80 lux, CWF and LED respectively. ANOVA found a significant effect (p < 0.05) due to light level, but no difference in tau between rats exposed to constant CWF light and rats exposed to constant LED light. This study has shown that LED light can produce the same entrainment pattern as a conventional CWT light at similar intensities (0.1, 1, 10, 40, and 80 lux). LED light sources may be a suitable replacement for conventional light sources used in animal habitat lighting while providing many mechanical and economical advantages.

A lighting assembly based on red and blue light-emitting diodes as a lighting source for space agriculture

NASA Astrophysics Data System (ADS)

Avercheva, Olga; Berkovich, Yuliy A.; Smolyanina, Svetlana; Bassarskaya, Elizaveta; Zhigalova, Tatiana; Ptushenko, Vasiliy; Erokhin, Alexei

Light-emitting diodes (LEDs) are a promising lighting source for space agriculture due to their high efficiency, longevity, safety, and other factors. Assemblies based on red and blue LEDs have been recommended in literature, although not all plants show sufficient productivity in such lighting conditions. Adding of green LEDs proposed in some works was aimed at psychological support for the crew, and not at the improvement of plant growth. We studied the growth and the state of the photosynthetic apparatus in Chinese cabbage (Brassica chinensis L.) plants grown under red (650 nm) and blue (470 nm) light-emitting diodes (LEDs). Plants grown under a high-pressure sodium lamp (HPS lamp) were used as a control. The plants were illuminated with two photosynthetic photon flux levels: nearly 400 µE and about 100 µE. Plants grown under LEDs with 400 µE level, as compared to control plants, showed lower fresh weight, edible biomass, growth rate, and sugar content. The difference in fresh weight and edible biomass was even more pronounced in plants grown with 100 µE level; the data indicate that the adaptability of the test plants to insufficient lighting decreased. Under LEDs, we observed the decreasing of root growth and the absence of transition to the flowering stage, which points to a change in the hormonal balance in plants grown in such lighting conditions. We also found differences in the functioning of the photosynthetic apparatus and its reaction to a low lighting level. We have concluded that a lighting assembly with red and blue LEDs only is insufficient for the plant growth and productivity, and can bring about alterations in their adaptive and regulatory mechanisms. Further studies are needed to optimize the lighting spectrum for space agriculture, taking into account the photosynthetic, phototropic and regulatory roles of light. Using white LEDs or adding far-red and green LEDs might be a promising approach.

The influence of different light quality and benzene on gene expression and benzene degradation of Chlorophytum comosum.

PubMed

Setsungnern, Arnon; Treesubsuntorn, Chairat; Thiravetyan, Paitip

2017-11-01

Benzene, a carcinogenic compound, has been reported as a major indoor air pollutant. Chlorophytum comosum (C. comosum) was reported to be the highest efficient benzene removal plant among other screened plants. Our previous studies found that plants under light conditions could remove gaseous benzene higher than under dark conditions. Therefore, C. comosum exposure to airborne benzene was studied under different light quality at the same light intensity. C. comosum could remove 500 ppm gaseous benzene with the highest efficiency of 68.77% under Blue:Red = 1:1 LED treatments and the lowest one appeared 57.41% under white fluorescent treatment within 8 days. After benzene was uptaken by C. comosum, benzene was oxidized to be phenol in the plant cells by cytochrome P450 monooxygenase system. Then, phenol was catalyzed to be catechol that was confirmed by the up-regulation of phenol 2-monooxygenase (PMO) gene expression. After that, catechol was changed to cic, cis-muconic acid. Interestingly, cis,cis-muconic acid production was found in the plant tissues higher than phenol and catechol. The result confirmed that NADPH-cytochrome P450 reductase (CPR), cytochrome b5 (cyt b5), phenol 2-monooxygenase (PMO) and cytochrome P450 90B1 (CYP90B1) in plant cells were involved in benzene degradation or detoxification. In addition, phenol, catechol, and cis,cis-muconic acid production were found under the Blue-Red LED light conditions higher than under white fluorescent light conditions due to under LED light conditions gave higher NADPH contents. Hence, C. comosum under the Blue-Red LED light conditions had a high potential to remove benzene in a contaminated site. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Micogreens Experiment

NASA Image and Video Library

2018-03-13

Kennedy Space Center scientists worked with OSRAM to insert a smart horticulture lighting system prototype into a food production system. The Phytofy RL prototype LED provides similar wavelength capability to a plant growth system currently on orbit. Photofy RL provides another avenue for future investigators conducting flight experiments to perform ground tests prior to flight under similar lighting conditions. The Phytofy RLs have been used to successfully grow microgreens of Wasabi, Tokyo Bekana, Mizuna, Broccoli, Garnet Giant, and Cauliflower.

A LED-based phosphorimeter for measurement of microcirculatory oxygen pressure.

PubMed

Guerci, Philippe; Ince, Yasin; Heeman, Paul; Faber, Dirk; Ergin, Bulent; Ince, Can

2017-02-01

Quantitative measurements of microcirculatory and tissue oxygenation are of prime importance in experimental research. The noninvasive phosphorescence quenching method has given further insight into the fundamental mechanisms of oxygen transport to healthy tissues and in models of disease. Phosphorimeters are devices dedicated to the study of phosphorescence quenching. The experimental applications of phosphorimeters range from measuring a specific oxygen partial pressure (Po 2 ) in cellular organelles such as mitochondria, finding values of Po 2 distributed over an organ or capillaries, to measuring microcirculatory Po 2 changes simultaneously in several organ systems. Most of the current phosphorimeters use flash lamps as a light excitation source. However, a major drawback of flash lamps is their inherent plasma glow that persists for tens of microseconds after the primary discharge. This complex distributed excitation pattern generated by the flash lamp can lead to inaccurate Po 2 readings unless a deconvolution analysis is performed. Using light-emitting diode (LED), a rectangular shaped light pulse can be generated that provides a more uniformly distributed excitation signal. This study presents the design and calibration process of an LED-based phosphorimeter (LED-P). The in vitro calibration of the LED-P using palladium(II)-meso-tetra(4-carboxyphenyl)-porphyrin (Pd-TCCP) as a phosphorescent dye is presented. The pH and temperature were altered to assess whether the decay times of the Pd-TCCP measured by the LED-P were significantly influenced. An in vivo validation experiment was undertaken to measure renal cortical Po 2 in a rat subjected to hypoxic ventilation conditions and ischemia/reperfusion. The benefits of using LEDs as a light excitation source are presented. Copyright © 2017 the American Physiological Society.

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

PubMed

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.

ELiXIR—Solid-State Luminaire With Enhanced Light Extraction by Internal Reflection

NASA Astrophysics Data System (ADS)

Allen, Steven C.; Steckl, Andrew J.

2007-06-01

A phosphor-converted light-emitting diode (pcLED) luminaire featuring enhanced light extraction by internal reflection (ELiXIR) with efficacy of 60 lm/W producing 18 lumens of yellowish green light at 100 mA is presented. The luminaire consists of a commercial blue high power LED, a polymer hemispherical shell lens with interior phosphor coating, and planar aluminized reflector. High extraction efficiency of the phosphor-converted light is achieved by separating the phosphor from the LED and using internal reflection to steer the light away from lossy reflectors and the LED package and out of the device. At 10 and 500 mA, the luminaire produces 2.1 and 66 lumens with efficacies of 80 and 37 lm/W, respectively. Technological improvements over existing commercial LEDs, such as more efficient pcLED packages or, alternatively, higher efficiency green or yellow for color mixing, will be essential to achieving 150 200 lm/W solid-state lighting. Advances in both areas are demonstrated.

Thermal and optical design analyses, optimizations, and experimental verification for a novel glare-free LED lamp for household applications.

PubMed

Khan, M Nisa

2015-07-20

Light-emitting diode (LED) technologies are undergoing very fast developments to enable household lamp products with improved energy efficiency and lighting properties at lower cost. Although many LED replacement lamps are claimed to provide similar or better lighting quality at lower electrical wattage compared with general-purpose incumbent lamps, certain lighting characteristics important to human vision are neglected in this comparison, which include glare-free illumination and omnidirectional or sufficiently broad light distribution with adequate homogeneity. In this paper, we comprehensively investigate the thermal and lighting performance and trade-offs for several commercial LED replacement lamps for the most popular Edison incandescent bulb. We present simulations and analyses for thermal and optical performance trade-offs for various LED lamps at the chip and module granularity levels. In addition, we present a novel, glare-free, and production-friendly LED lamp design optimized to produce very desirable light distribution properties as demonstrated by our simulation results, some of which are verified by experiments.

Light-Emitting Diode (LED) Traps Improve the Light-Trapping of Anopheline Mosquitoes.

PubMed

Costa-Neta, B M; da Silva, A A; Brito, J M; Moraes, J L P; Rebêlo, J M M; Silva, F S

2017-11-07

Numerous advantages over the standard incandescent lamp favor the use of light-emitting diodes (LEDs) as an alternative and inexpensive light source for sampling medically important insects in surveillance studies. Previously published studies examined the response of mosquitoes to different wavelengths, but data on anopheline mosquito LED attraction are limited. Center for Disease Control and Prevention-type light traps were modified by replacing the standard incandescent lamp with 5-mm LEDs, one emitting at 520 nm (green) and the other at 470 nm (blue). To test the influence of moon luminosity on LED catches, the experiments were conducted during the four lunar phases during each month of the study period. A total of 1,845 specimens representing eight anopheline species were collected. Anopheles (Nyssorhynchus) evansae (35.2%) was the most frequently collected, followed by An. (Nys.) triannulatus (21.9%), An. (Nys.) goeldii (12.9%), and An. (Nys.) argyritarsis (11.5%). The green LED was the most attractive light source, accounting for 43.3% of the individuals collected, followed by the blue (31.8%) and control (24.9%) lights. The LED traps were significantly more attractive than the control, independent of the lunar phase. Light trapping of anopheline mosquitoes was more efficient when the standard incandescent lamp was replaced with LEDs, regardless of the moon phase. The efficiency of LEDs improves light trapping results, and it is suggested that the use of LEDs as an attractant for anopheline mosquitoes should be taken into consideration when sampling anopheline mosquitoes. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ton, My K.; Richman, Eric E.; Gilbride, Theresa L.

In August 2008 the Pacific Northwest National Laboratory (PNNL) conducted a light emitting diode (LED) residential lighting demonstration project for the U.S. Department of Energy (DOE), Office of Building Technologies, as part of DOE’s Solid State Lighting (SSL) Technology Demonstration Gateway Program. Two lighting technologies, an LED replacement for downlight lamps (bulbs) and an LED undercabinet lighting fixture, were tested in the demonstration which was conducted in two homes built for the 2008 Tour of Homes in Eugene, Oregon. The homes were built by the Lane County Home Builders Association (HBA), and Future B Homes. The Energy Trust of Oregonmore » (ETO) also participated in the demonstration project. The LED downlight product, the LR6, made by Cree LED Lighting Solutions acts as a screw-in replacement for incandescent and halogen bulbs in recessed can downlights. The second product tested is Phillips/Color Kinetics’ eW® Profile Powercore undercabinet fixture designed to mount under kitchen cabinets to illuminate the countertop and backsplash surfaces. Quantitative and qualitative measurements of light performance and electrical power usage were taken at each site before and after initially installed halogen and incandescent lamps were replaced with the LED products. Energy savings and simple paybacks were also calculated and builders who toured the homes were surveyed for their responses to the LED products. The LED downlight product drew 12 Watts of power, cutting energy use by 82% compared to the 65W incandescent lamp and by 84% compared to the 75W halogen lamp. The LED undercabinet fixture drew 10 watts, cutting energy use by 83% to 90% compared to the halogen product, which was tested at two power settings: a low power 60W setting and a high power 105W setting. The LED downlight consistently provided more light than the halogen and incandescent lamps in horizontal measurements at counter height and floor level. It also outperformed in vertical illuminance measurements taken on the walls, indicating better lateral dispersion of the light. The undercabinet fixture’s light output was midway between the low and high power halogen undercabinet fixture light outputs (35.8 foot candle versus 13.4 fc and 53.4 fc) but it produced a more uniform light (max/min ratio of 7.0 versus 10.8). The color correlated temperature (CCT, the blue or yellowness) of the LED light correlated well with the halogen and incandescent lights (2675 K vs 2700 K). The color rendering of the LED downlight also correlated well at 92 CRI compared to 100 CRI for the halogen and incandescent lamps. The LED undercabinet fixture had measures of 2880 K CCT and 71 CRI compared to the 2700 K and 100 CRI scores for the halogen undercabinet fixture. Builders who toured the homes were surveyed; they gave the LED downlight high marks for brightness, said the undercabinet improved shadows and glare and said both products improved overall visibility, home appearance, and home value. Paybacks on the LED downlight ranged from 7.6 years (assuming electricity cost of 11 c/kWh) to 13.5 years (at 5C/kWh). Paybacks on the LED undercabinet fixture in a new home ranged from 4.4 years (11c/kWh electricity) to 7.6 years (5c/kWh) based on product costs of $95 per LED downlight and $140 per LED undercabinet fixture at 3 hrs per day of usage for the downlight and 2 hrs per day for the undercabinet lighting.« less

Battery Charge Affects the Stability of Light Intensity from Light-emitting Diode Light-curing Units.

PubMed

Tongtaksin, A; Leevailoj, C

This study investigated the influence of battery charge levels on the stability of light-emitting diode (LED) curing-light intensity by measuring the intensity from fully charged through fully discharged batteries. The microhardness of resin composites polymerized by the light-curing units at various battery charge levels was measured. The light intensities of seven fully charged battery LED light-curing units-1) LY-A180, 2) Bluephase, 3) Woodpecker, 4) Demi Plus, 5) Saab II, 6) Elipar S10, and 7) MiniLED-were measured with a radiometer (Kerr) after every 10 uses (20 seconds per use) until the battery was discharged. Ten 2-mm-thick cylindrical specimens of A3 shade nanofilled resin composite (PREMISE, Kerr) were prepared per LED light-curing unit group. Each specimen was irradiated by the fully charged light-curing unit for 20 seconds. The LED light-curing units were then used until the battery charge fell to 50%. Specimens were prepared again as described above. This was repeated again when the light-curing units' battery charge fell to 25% and when the light intensity had decreased to 400 mW/cm 2 . The top/bottom surface Knoop hardness ratios of the specimens were determined. The microhardness data were analyzed by one-way analysis of variance with Tukey test at a significance level of 0.05. The Pearson correlation coefficient was used to determine significant correlations between surface hardness and light intensity. We found that the light intensities of the Bluephase, Demi Plus, and Elipar S10 units were stable. The intensity of the MiniLED unit decreased slightly; however, it remained above 400 mW/cm 2 . In contrast, the intensities of the LY-A180, Woodpecker, and Saab II units decreased below 400 mW/cm 2 . There was also a significant decrease in the surface microhardnesses of the resin composite specimens treated with MiniLED, LY-A180, Woodpecker, and Saab II. In conclusion, the light intensity of several LED light-curing units decreased as the battery was discharged, with a coincident reduction in the units' ability to polymerize resin composite. Therefore, the intensity of an LED light-curing unit should be evaluated during the life of its battery charge to ensure that sufficient light intensity is being generated.

LED Lighting – Modification of Growth, Metabolism, Yield and Flour Composition in Wheat by Spectral Quality and Intensity

PubMed Central

Monostori, István; Heilmann, Márk; Kocsy, Gábor; Rakszegi, Marianna; Ahres, Mohamed; Altenbach, Susan B.; Szalai, Gabriella; Pál, Magda; Toldi, Dávid; Simon-Sarkadi, Livia; Harnos, Noémi; Galiba, Gábor; Darko, Éva

2018-01-01

The use of light-emitting diode (LED) technology for plant cultivation under controlled environmental conditions can result in significant reductions in energy consumption. However, there is still a lack of detailed information on the lighting conditions required for optimal growth of different plant species and the effects of light intensity and spectral composition on plant metabolism and nutritional quality. In the present study, wheat plants were grown under six regimens designed to compare the effects of LED and conventional fluorescent lights on growth and development, leaf photosynthesis, thiol and amino acid metabolism as well as grain yield and flour quality of wheat. Benefits of LED light sources over fluorescent lighting were manifested in both yield and quality of wheat. Elevated light intensities made possible with LEDs increased photosynthetic activity, the number of tillers, biomass and yield. At lower light intensities, blue, green and far-red light operated antagonistically during the stem elongation period. High photosynthetic activity was achieved when at least 50% of red light was applied during cultivation. A high proportion of blue light prolonged the juvenile phase, while the shortest flowering time was achieved when the blue to red ratio was around one. Blue and far-red light affected the glutathione- and proline-dependent redox environment in leaves. LEDs, especially in Blue, Pink and Red Low Light (RedLL) regimens improved flour quality by modifying starch and protein content, dough strength and extensibility as demonstrated by the ratios of high to low molecular weight glutenins, ratios of glutenins to gliadins and gluten spread values. These results clearly show that LEDs are efficient for experimental wheat cultivation, and make it possible to optimize the growth conditions and to manipulate metabolism, yield and quality through modification of light quality and quantity. PMID:29780400

LED Lighting - Modification of Growth, Metabolism, Yield and Flour Composition in Wheat by Spectral Quality and Intensity.

PubMed

Monostori, István; Heilmann, Márk; Kocsy, Gábor; Rakszegi, Marianna; Ahres, Mohamed; Altenbach, Susan B; Szalai, Gabriella; Pál, Magda; Toldi, Dávid; Simon-Sarkadi, Livia; Harnos, Noémi; Galiba, Gábor; Darko, Éva

2018-01-01

The use of light-emitting diode (LED) technology for plant cultivation under controlled environmental conditions can result in significant reductions in energy consumption. However, there is still a lack of detailed information on the lighting conditions required for optimal growth of different plant species and the effects of light intensity and spectral composition on plant metabolism and nutritional quality. In the present study, wheat plants were grown under six regimens designed to compare the effects of LED and conventional fluorescent lights on growth and development, leaf photosynthesis, thiol and amino acid metabolism as well as grain yield and flour quality of wheat. Benefits of LED light sources over fluorescent lighting were manifested in both yield and quality of wheat. Elevated light intensities made possible with LEDs increased photosynthetic activity, the number of tillers, biomass and yield. At lower light intensities, blue, green and far-red light operated antagonistically during the stem elongation period. High photosynthetic activity was achieved when at least 50% of red light was applied during cultivation. A high proportion of blue light prolonged the juvenile phase, while the shortest flowering time was achieved when the blue to red ratio was around one. Blue and far-red light affected the glutathione- and proline-dependent redox environment in leaves. LEDs, especially in Blue, Pink and Red Low Light (RedLL) regimens improved flour quality by modifying starch and protein content, dough strength and extensibility as demonstrated by the ratios of high to low molecular weight glutenins, ratios of glutenins to gliadins and gluten spread values. These results clearly show that LEDs are efficient for experimental wheat cultivation, and make it possible to optimize the growth conditions and to manipulate metabolism, yield and quality through modification of light quality and quantity.

Light Converting Inorganic Phosphors for White Light-Emitting Diodes

PubMed Central

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

2010-01-01

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

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

2012-09-30

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

A Simple, Small-Scale Lego Colorimeter with a Light-Emitting Diode (LED) Used as Detector

ERIC Educational Resources Information Center

Asheim, Jonas; Kvittingen, Eivind V.; Kvittingen, Lise; Verley, Richard

2014-01-01

This article describes how to construct a simple, inexpensive, and robust colorimeter from a few Lego bricks, in which one light-emitting diode (LED) is used as a light source and a second LED as a light detector. The colorimeter is suited to various grades and curricula.

Sensitivity to Ethephon Degreening Treatment Is Altered by Blue LED Light Irradiation in Mandarin Fruit.

PubMed

Deng, Lili; Yuan, Ziyi; Xie, Jiao; Yao, Shixiang; Zeng, Kaifang

2017-08-02

Although citrus fruits are not climacteric, exogenous ethylene is widely used in the degreening treatment of citrus fruits. Irradiation with blue light-emitting diode (LED) light (450 nm) for 10 h can promote the formation of good coloration of ethephon-degreened fruit. This study evaluated the effect of blue LED light irradiation on the pigments contents of ethephon-degreened fruit and evaluated whether the blue LED light irradiation could influence the sensitivity of mandarin fruit to ethylene. The results indicated that blue light can accelerate the color change of ethephon-degreened fruit, accompanied by changes in plastid ultrastructure and chlorophyll and carotenoid contents. Ethephon-induced expressions of CitACS1, CitACO, CitETR1, CitEIN2, CitEIL1, and CitERF2 were enhanced by blue LED light irradiation, which increased the sensitivity to ethylene in ethephon-degreened fruits. These results indicate that blue LED light-induced changes in sensitivity to ethylene in mandarin fruit may be responsible for the improved coloration of ethephon-degreened mandarin fruits.