Main Light Source Research Articles

Automatic Control of a Sunlight Reflector Board for Achieving the Sunlight Intensity Set by the Greenhouse Operator

This article proposes an autonomous greenhouse system which has a sunlight Reflector Board (RB). In general, a greenhouse, which grows leafy vegetables, utilizes artificial light, such as LED light, as a supplementary source of light. However, artificial light cannot be used as the main source of light for photosynthesis for various kinds of plants. Our article utilizes natural sunlight, instead of artificial light, for growing plants inside a greenhouse. We develop an autonomous system to control the amount of sunlight inside the greenhouse by controlling the angle of the RB, which is located in front of the greenhouse. Since the proposed greenhouse uses natural sunlight, one can grow various kinds of plants which cannot grow under artificial light. Suppose that we accumulate the RB angle data for one year. Since solar motion repeats every year, we can control the RB according to this accumulated angle data. In this way, we can reduce unnecessary RB controls, after running the system for more than a year. As far as we know, the proposed greenhouse system based on autonomous RB controls is novel, since we control RBs for providing optimal sunlight for plants inside the greenhouse. We perform experiments to demonstrate the performance of the proposed greenhouse system.

Urbo-ecological characteristics of the formation of green architecture in the conditions of sustainable development

The article defines the main problems and prospects for the development of the concept of “green” architecture in the context of sustainable development. In the process of identifying the main problem, the relevance of the research was determined. Having conducted a thorough analysis of the current state of green architecture formation in the conditions of sustainable development, it was found that green architecture is multi-vector and includes energy-efficient, ecological and economic aspects, while the impact on the environment is minimal. The main trends in the development of "green" architecture were identified, which gave the opportunity to apply their role in the formation of a modern urban environment in terms of increasing the energy efficiency of buildings, the use of solar energy, "green" technologies and the latest materials. Based on the conducted research, the main principles of "green" architecture were defined: the principle of energy efficiency manifests itself in such design and construction, in which heat consumption, both for heating and for cooling, is reduced to a minimum; the principle of sound orientation using solar energy as the main source of light and heat; the principle of inclusiveness, where the urban environment is designed for the comfortable stay of people from all walks of life; the principle of environmental friendliness includes a harmonious combination of the urbanized and natural environment; the principle of autonomy represents the possibility of architectural and urban planning objects to function autonomously in critical situations.

BER analysis of a full-duplex relay-assisted BPSK-SIM based VLC system for indoor applications.

This paper contemplates a relay-assisted visible light communication (VLC) system, where the light source (table lamp) acts as a relay node and cooperates with the main light source. Following the IEEE 802.15.7r1 VLC reference channel model, we assume that there are two different light sources present in an office room. The first one is the source terminal present on the ceiling and another one is the desk lamp that serves as the relay station, which works in a full-duplex method. Because of the loop interference channel, we model the VLC relay terminal using ray tracing simulations. We have analyzed the bit error rate (BER) performance of the relay-assisted VLC system using a binary phase shift keying-subcarrier intensity modulation (BPSK-SIM) technique. The proposed method outperforms existing phase shift keying (PSK) and square M-quadrature amplitude modulation (M-QAM) techniques. The proposed VLC system using the BPSK-SIM technique achieves a BER performance of 10-12 for an SNR of 20dB. The results of the proposed full-duplex and half-duplex relayed VLC systems are evaluated using equal power allocation (EPA) and optimum power allocation (OPA) techniques over three different modulation schemes, which are 2-PSK, square M-QAM, and BPSK-SIM.

Optimization of LED-Based Solar Simulators for Cadmium Telluride and Microcrystalline Silicon Solar Cells

Solar simulators are instruments used for controllable measurements of the properties of solar cells in indoor environments. The purpose of this paper is to examine the peculiarities of the photoresponses of CdTe/CdSeTe and microcrystalline Si solar cells and to reveal the pathways to reduction of spectrum mismatch effects when using light-emitting diode (LED)-based or hybrid LED and halogen lamp-based solar simulators of an A+-class spectrum with a small number of sources. While only four different LED types are needed to achieve an A+-class spectrum under updated IEC 60904-9:2020 standard requirements, as demonstrated by our results, additional ultraviolet LEDs are necessary to reduce the spectrum mismatch. For hybrid solar simulator configurations, the combination of cool white LED arrays and halogen emitters can serve as a main light source. Optimized for both solar cell types, hybrid simulators have a lower spectral deviation and better spectrum coverage compared to LED-only simulators with the same number of distinct source types. In addition, our results predict lower spectral mismatch errors for optimized simulators when compared with conventional Xe lamp-based simulators.

Effect of Light Intensity and Spectra on Inorganic Constituents in Vietnamese Coriander (Persicaria odorata (Lour.) Soják)

With the aim of optimizing resources in regional production of nutritive valuable leafy vegetables, this study was conducted to obtain more knowledge regarding the interdependencies between light conditions and accumulation of inorganic constituents. The test plant, P. odorata, was cultivated in a climate chamber with fluorescent tubes as the main light source and daylight integrals (DLI) varying between 4.68 and 9.06 mol·m−2·day−1. The average DLI in greenhouse experiments was 41.55 mol·m−2·day−1. Light conditions were modified using additional LEDs (443, 515, and 629 nm) or by covering the plants with photoselective plastic films, leading to a lower DLI and modified light spectrum, especially by reducing the green spectral range. Contents of nitrate, phosphorus, potassium, magnesium, calcium, and iron, biomass accumulation, and water content were analyzed. In terms of particular light modifications, additional green (515 nm) and red (629 nm) LEDs showed reducing effects on nitrate content at both cultivation locations. Other inorganic constituents were affected differently depending on cultivation location. However, the calculation of average partial correlation coefficients enabled a more general statement. Increasing DLI correlated positively with contents of magnesium, nitrate, and potassium but negatively with contents of calcium and iron. Additionally, nitrate content correlated positively with the spectral range of 651–700 nm but negatively with the R:FR ratio. Consequently, a general recommendation related to the light conditions is not possible, as inorganic constituents were affected differently. Nevertheless, as the nitrate content in leafy vegetables is of high concern and was reduced by higher shares of green or red light, this might be one way to regulate nitrate content in leafy vegetables.

CURRENT STATE AND PROSPECTS OF IMPROVING THE LIGHTING EQUIPMENT OF AIRCRAFTS

The development of aviation technology is directly related to technological progress. Taking this into account, the question of switching to modern light sources on aircraft arises. Lighting equipment plays an important role in ensuring the operation of aircraft and flight safety, especially at night. Among the elements of aircraft’s electrical equipment, lighting equipment represents a fairly large electrical load (5.20 % of the total power of consumers).Today, incandescent lamps are most often used in aircraft lighting systems, in which an incandescent thread (a refractory conductor, a spiral made of tungsten alloy), located in a glass vessel with a vacuum or filled with an inert gas, is heated to a high temperature (luminosity temperature) due to the flow of electric current through this thread.
 Recently, reliable and energy-efficient Light Emitting Diode (LED) light sources have been widely implemented in lighting systems for various purposes. Light diodes have now become light sources that are produced on an industrial scale for a variety of needs. LEDs are one of the key devices in today’s technological society. Unlike many other light sources, LEDs can convert electrical energy into light with an efficiency close to unity. It is expected that the role of LEDs will only grow and in the future they will become the main source of light.
 Consequently, the light sources currently used on aircraft of the Armed Forces of Ukraine are outdated and do not correspond to the level of accumulated scientific and technical potential. Therefore, research aimed at introducing LED light technologies to the lighting equipment of aircraft is relevant.
 The article considers the typical structure and main characteristics of aircraft’s lighting equipment of the Armed Forces of Ukraine. The stages of development of aircraft lighting equipment, the main types of existing lighting sources and their features are considered. It is noted that the development of lighting technology and the successful introduction of LEDs into lighting technology for various purposes allow us to consider the possibility of using them as the main light source on aircraft in order to improve operational characteristics. The relevance of conducting research aimed at improving the lighting equipment of aircraft is substantiated.

Intensity Stability Comparison Between Different Colors of Laser Pointer

Different source of light can be used as a main light source in an open path optical method. Sunlight, tungsten lamp, LED, laser, mercury vapor lamp and halogen are the example of the light source.It is important to test the stability of the light source used to avoid inaccuracy in the measurement. The purpose of this project is to determine which color of laser has higher stability. Once the light is switched on, the intensity of the light source changes slowly until it comes to a stable state. Each color has different counts of intensity and stability. Different set of laser pointer is used in this project which included blue, violet, red and green color. An open path optical method is used in the experiment. A different color of laser pointer will be used as a light source whilespectrometer will act as a detector. The stability for each color of laser pointer is reported in this paper where the standarddeviationforeachcoloriscalculated todetermined whichcolorhaveahigherstability.The standard deviation for green color has the smallest value among these four colors where the standard deviation is 15.97.Colorwithsmallerstandarddeviationhasthehigheststability.

Impacts of Application Light-Emitting Diode (LED) Lamps in Reducing Generator Power on Ro-Ro Passenger Ship 300 GT KMP Bambit

KMP Bambit is an Indonesian Ro-Ro ship that carries passengers. It is public transportation from Merauke Regency to Asmat Regency and vice versa. The ship is still using fluorescent lamps as its main lighting source. This study presents a comparative study of the efficiency level between the use of fluorescent lamps and LED lamps in the room aboard the ship. The method used is the zonal cavity (lumen) method by dividing each room into three parts, namely the height ceiling cavity (hcc), height room cavity (hrc), and height floor cavity (hfc). The illumination value was determined according to the standards set for each room. The principal results for comparing lighting power on KMP Bambit showed that the total lighting electrical load accumulated using the fluorescent lighting type was 24.31kW. In contrast, LED lighting had a total lighting electrical load of 16.51 kW. This reduced the generator power from 68 kW to 60 kW, which could improve the efficiency of ship fuel operational costs. This study can evaluate the existing Ro-Ro ship fleet and be a good option in the process of building Ro-Roships in the future.

10 kHz repetition rate picosecond green laser for high-accuracy satellite ranging

Picosecond pulse laser is the main light source for satellite laser ranging. In this paper, a 10 kHz repetition rate picosecond green laser with an average output power of 5.3 W is demonstrated. The laser generates a pulse width of 18.6 ps at a center wavelength of 532.20 nm with a spectral width of .066 nm. The beam quality is well preserved with M2 of 1.1 with the beam divergence measured to be .62 mrad and pointing stability of 7 μrad over 30 min of operation. The laser system was then applied to measure the BeiDou satellite (Compass-I3) and generated a single range accuracy of 3.2 mm, which is the highest reported range accuracy for synchronous orbit satellite laser ranging.

A laboratory based study on the effect of peripheral flickering LED sources on reaction time of drivers for object recognition

The effects of peripheral source on On-axis visual task performance by human observers under different lighting conditions are very much identified. The effect of Color Temperature of the main and peripheral light sources also influences the driver’s performance in a real road. There arises a necessity to investigate the effect of peripheral glaring LED sources on driver’s task performance. In this paper a laboratory-based experiment is explained, which was carried out, to understand the effect of varying frequencies of peripheral flickering LED sources with varying chromaticity of main LED source on the reaction times of static human observers for test object recognition and to find the correlation among observers’ reaction times, main source’s chromaticity and flickering frequency. CCT is a suitable lighting parameter to experiment with as it can be directly correlated with chromaticity, a fundamental mark for a light source. It is found from the experiment that reaction time decreases as the CCT of main source increases irrespective of the increment of flickering frequency. Besides, it is also found that the introduction of flicker and change of flickering frequency have profound effects on human observers’ reaction time and flickering of peripheral glare sources increases the reaction time for object recognition. Moreover, it is also seen from the additional behavioral studies done on the participants in the same experimental setup that, the behavioral study supports the findings from reaction time measurement study.

Superflares on solar-like stars

Context. Over the past years, thousands of stellar flares have been detected by harvesting data from large photometric surveys. These detections, however, do not account for potential sources of contamination such as background stars or small Solar System objects appearing in the same aperture as the primary target. Aims. We present a new method for identifying the true flare sources in large photometric surveys using data from the Kepler mission as an illustrative example. The new method considers not only the brightness excess in the stellar light curves, but also the location of this excess in the pixel-level data. Methods. Potential flares are identified in two steps. First, we search the light curves for at least two subsequent data points exceeding a 5σ threshold above the running mean. For these two cadences, we subtract the “quiet” stellar flux from the Kepler pixel data to obtain new images where the potential flare is the main light source. In the second step, we use a Bayesian approach to fit the point spread function of the instrument to determine the most likely location of the flux excess on the detector. We match this location with the position of the primary target and other stars from the Gaia DR2 catalog within a radius of 10 arcsec around the primary Kepler target. When the location of the flux excess and the target star coincide, we associate the event with a flare on the target star. Results. We applied our method to 5862 main-sequence stars with near-solar effective temperatures. From the first step we found 2274 events exceeding the 5σ level in at least two consecutive points in the light curves. Applying the second step reduced this number to 342 superflares. Of these, 283 flares occurred on 178 target stars and 47 events are associated with fainter background stars; in 10 cases the flare location could not be distinguished between the target and a background star. We also present cases where flares were reported previously but our technique could not attribute them to the target star. Conclusions. We conclude that identifying outliers in the light curves alone is insufficient to attribute them to stellar flares and that flares can only be uniquely attributed to a certain star when the instrument pixel-level data together with the point spread function are taken into account. As a consequence, previous flare statistics are likely contaminated by instrumental effects and unresolved astrophysical sources.

Locating the flickering source in polars

ABSTRACT Flickering is a fast variability observed in all accreting systems. It has been shown that in most cataclysmic variables flickering originates in the accretion disc. However, in polars the strong magnetic field of the white dwarf prevents the formation of an accretion disc. Therefore, the origin of flickering in polars is not clear. We analysed the changes of flickering amplitude with orbital phase in seven polars in order to reveal its site of origin. We show that at least in some polars there are two separate sources of flickering. Moreover, at least one of the sources is located at a large distance from the main source of light in the system.

Effect of LED light on the growth and physiological indices of blueberry

AbstractLight‐emitting diode (LED) is a recent type of light source characterized by low energy consumption and high photoelectric conversion efficiency and can be used in modern smart agriculture. However, there are few published studies on the use of LED light, especially on blueberry (Vaccinium spp.), despite its importance in boosting the economies of many countries. Therefore, this study was aimed at assessing the effects of light quality on blueberry seedling tissue cultures morphological and physiological parameters with emphasis on the influence of different light wavelengths. In the research, we used white light (i.e., fluorescent lamp) and four treatments of composite LED light (blue wavelength [B]/red wavelength [R] = 1:2 [1B2R], B/R = 1:4 [1B4R], B/R = 2:1 [2B1R], B/R = 4:1 [4B1R]). The results showed that: the number of leaves, stem, and fresh weight increased when exposed to 2B1R; stem length, thickness, and fresh weight were higher in the 1B2R treatment; chlorophyll, carotenoid pigments, peroxidase, and superoxide dismutase were enhanced under treatment 1B2R; soluble sugar, anthocyanin, and proline were greater when exposed to 2B1R; soluble protein was higher with 1B4R; and malondialdehyde increased in the 4B1R treatment. Overall, it can be said that 1B2R LED lights enhanced the selected parameters in blueberry seedlings and can be used as the main light source in the cultivation of blueberry factory seedlings.

Resonant Fiber Optic Gyroscope With HOPLL Technique Based on Acousto-Optic Modulation

Backscattering noise is a key factor to restrict the performance of resonant fiber optic gyroscopes (RFOG). In order to improve the accuracy of RFOG, this paper proposes a scheme with heterodyne optical phase-locked loop (HOPLL) technique based on acousto-optic modulation (AOM) to suppress backscattering noise. In this scheme, the main light source is divided into three output lights, two of which are frequency-shifted by the AOM, and then are phase-locked with the third light, using the HOPLL technique. The two channels of frequency-shifted light are respectively used as the clockwise (CW) and counterclockwise (CCW) light of the RFOG, and are locked on the resonance peak. The transmissive fiber resonator can be regarded as a band-pass filter. By adjusting the reference signal in the HOPLL, the carrier of the two frequency-shifted lights can be moved away from the resonance peak. The carrier light intensity of the frequency-shifted light is suppressed by the cavity itself. The suppression ratio (SPR) reaches 15.83dB. The experimental results illustrate that the bias stability of RFOG is 3.8°/h based on the Allan deviation, strongly proving the effectiveness of this scheme in suppressing backscattering noise in practical applications.

Dense and Proximate Development—Daylight in the Downtown Area of a Compact City

Daylight is of utmost importance and should be the main source of light in most areas dedicated to working and living. When considering our contemporary way of living, it can be easily discerned that most of our life is spent indoors, yet in a typical architectonic design approach, daylight is too often hardly of consequence. Hence daylight becomes a critical factor. Designers comply with the legal requirements of the solar hours required for areas subjected to constant use. Simultaneously for electrical engineers’ daylight is only an additional source of light valued only where energy efficiency is concerned. The basic idea of this research is to, starting from the concept level, design the building’s volume in line with energy efficiency requirements and user expectations using daylight access strategy as the main parameter. This scope of research has been a subject of various scientific theses conducted within the last years at the Faculty of Architecture Warsaw University of Technology. This paper is dedicated to the latest and most developed outcomes. The presented solution is an architectonic point of view dedicated to the use of the daylight factor in office areas located in a dense city district that may support efficient energy requirements, including the requirements of the electric lighting system. Illumination values were set according to the BREEAM daylight and PN-EN 17037 Daylight of Buildings standard. The presented strategy is unconventional for Poland, but has the potential to be included in practice and should be developed further, together with electrical engineers, as a part of energy-saving solutions. Possibly, it should be followed simultaneously with the development of the compact cities ideas. It is hoped that it might be a starting point for discussion, and for a more detailed interdisciplinary research in the future.

Review of Low-Frequency Noise Properties of High-Power White LEDs during Long-Term Aging.

Low-frequency noise investigation is a highly sensitive and very informative method for characterization of white nitride-based light-emitting diodes (LEDs) as well as for the evaluation of their degradation. We present a review of quality and reliability investigations of high-power (1 W and 3 W) white light-emitting diodes during long-term aging at the maximum permissible forward current at room temperature. The research was centered on the investigation of blue InGaN and AlInGaN quantum wells (QWs) LEDs covered by a YAG:Ce3+ phosphor layer for white light emission. The current-voltage, light output power, and low-frequency noise characteristics were measured. A broadband silicon photodetector and two-color (blue and red) selective silicon photodetectors were used for the LED output power detection, which makes it possible to separate physical processes related to the initial blue light radiation and the phosphor luminescence. Particular attention was paid to the measurement and interpretation of the simultaneous cross-correlation coefficient between electrical and optical fluctuations. The presented method enables to determine which part of fluctuations originates in the quantum well layer of the LED. The technique using the two-color selective photodetector enables investigation of changes in the noise properties of the main blue light source and the phosphor layer during the long-term aging.

INVESTIGATION OF LIGHT INTENSITY OF LIGHT CURING UNITS AFTER DIFFERENT PERIODS OF USE

Quartz-tungsten halogen light curing units (LCUs) have been the main source of light for the polymerization of resin based composites (RBCs) for several decades. Since the beginning of the 20th century, however, their use has been reduced due to the invention and improvement of LED LCUs. Various factors can cause a decrease in the light intensity of LED LCUs, one of which is diode aging. The aim of the present paper is to study the change in light intensity of LCUs after different periods of intensive use. For this purpose, the light intensity of 94 regularly used LED LCUs aged between 1 and 10 years was measured with a digital radiometer. The devices were used in conventional mode with maximum light intensity. It was found that regardless of the type and model of LCU, there is a direct relationship between the time of use and light intensity - the longer the operation period of a device is and the more used it is, the lower its intensity is. The decrease in light intensity as devices age is different for different models, as well as for different devices of the same model. In the studied LCUs with a 10-year period of use, 77.5% have light intensity lower than the required minimum of 400 mW/cm2, which makes them unusable. It can be concluded that dentists should regularly monitor and measure the light intensity of their LCUs, especially as they age, to ensure the longevity of their restorative procedures.

Design of a DC Microgrid System for a Remote Community in Nigeria

This paper presents the design of a DC microgrid for a remote community in Edo State, Nigeria having a solar irradiance of 4.63 kWh/m2/day. The community is isolated and located far away from the city with no access to the electricity grid. There is a need for lighting and running of electronics, as the main source of lighting presently is kerosine, which is not efficient and leads to health issues. The community is made up of 9 residences that are not more than 100 m apart. House 1 was selected as the standard house with a load of 1 kWh/day, while the other 8 houses have a load difference of ±10% with reference to house 1. Using a 48 V DC bus, the designed PV system components comprise of a 100W solar photovoltaic (PV) panel and a 12 V 45 A·hr battery. The system was sized using Homer Pro. Optimization results presented various design for the various houses. The result obtained showed reasonable and feasible cost-effective solution in terms of the Net Present Cost in both installation and running of the hybrid system for the community. Sensitivity analysis was also carried out to test the adaptability of the system using a solar irradiation input of ±10%. Detailed result of the analysis is presented in the paper.

Laryngeal High-Speed Videoendoscopy with Laser Illumination: A Preliminary Report.

<br><b>Introduction:</b> Advances in computer image analysis have enabled the use of new functional imaging methods in the diagnosis of laryngeal diseases. Particularly interesting techniques of dynamic laryngeal imaging involve High Speed Videoendoscopy (HSV). This still-developed technique allows to overcome the limitations of laryngovideostroboscopy (LVS) and a more detailed analysis of the glottal function based on the image of the actual vibrations of the vocal folds. It also enables the determination of objective coefficients parameterizing phonatory vibrations of the vocal folds.</br> <br><b>Aim:</b> The aim of this pilot study was to evaluate the use of a high-speed videoendoscopy set with laser illumination for the diagnosis of glottic pathology in ENT practice.</br> <br><b>Material and methods:</b> The study included 40 patients who underwent LVS followed by HSV. The modern HSV examination kit - Advanced Larynx Imager System (ALIS), used for the first time in a clinical setting in Poland, is characterized by significantly improved, compared to the previously used high-speed cameras, operational parameters - a light head, the possibility of continuous lighting operation without excessive heating of the head tip, registration of the image in full color scale. Thanks to such modernization, the safety and course of the examination do not differ from laryngoscopy conducted with commonly used recorders. The device owes some of these improvements to a laser illuminator which was used for the first time as the main light source in a high-speed camera. In the study, two cases were selected to present the results of HSV and the analysis of the generated kymograms - a woman with no glottic pathology and a man with a polyp of the right vocal fold. In the first case, the HSV examination compared with the LVS revealed a discrete glottis functional disorder in the form of a tendency to hyperphonation. The patient with an organic lesion had a clearly visible irregularity of vocal fold vibrations, which also allowed to trace mucosal wave disturbances related to its reflection from the pathological structure of the glottis and the formation of a return wave, both on the fold affected by the lesion and, to a lesser extent, contralaterally. The glottic dysfunctions observed in the studied patients were confirmed in the generated kymograms and the graphs of the glottal width waveform (GWW), as well as in the parameters calculated on their basis, assessing the frequency and amplitude of phonatory vibrations.</br> <br><b>Conclusions:</b> The use of high-speed videoendoscopy allows for a much more accurate assessment of the phonatory function of the glottis than in laryngovideostroboscopy. The presented HSV system allows for obtaining high quality kinematic images of the larynx, color fidelity, and contrast. The use of this technology in laryngological practice enables precise structural and functional assessment of the glottis and detection of discrete phonation disorders that elude the techniques used so far.</br&gt.

Real-Time Outdoor Illumination Estimation for Camera Tracking in Indoor Environments

Dynamic illumination is a challenging problem for visual robot localization and tracking. In indoor environments, the main source of light during the day is outdoor illumination. We propose a method that estimates the appearance of an indoor scene in real-time based on a reflectance map and the current outdoor lighting. Our outdoor illumination model consists of three components, namely sun, sky and ground, where the sun position is obtained from the scene geolocation and the current time of day. The scene illumination is pre-computed using radiosity transport for each of those components. To deal with dynamic illumination resulting from changing weather conditions, we estimate the outdoor light brightness in each input frame and scale the pre-computed illumination accordingly. We evaluate our approach on real-world data covering diverse outdoor illumination settings and show that our adaptable model is beneficial for direct camera tracking.