Spectral Distribution Of Light Research Articles

Analysis of Illumination Generated by LED Matrices Distribution

Сreation of indoor lighting systems with the possibility of changing its parameters in space and time is a promising direction within the framework of the intellectual environment system. The aim of this work was to create a methodology for calculating the illumination created by LED matrices which does not require the use of specialized software products and is adapted to the possibility of varying the parameters of LEDs and illuminated rooms.The urgency of creating a room lighting system that simulates the conditions of natural lighting taking into account the need to change its spectral composition in time, in space taking into account the physical and psychological state of a person is substantiated. The possibility of using well-known computer programs to calculate the distribution of illumination in the room is analyzed.A method has been developed for calculating the distribution of illumination on a plane using both a flat LED matrix and a matrix with an inclined arrangement of the planes of individual LEDs. It is shown that the distribution of illumination is a function of the indicatrix of the light intensity of the LED, its location in space, the number of LEDs in the matrix.Illumination distribution has been calculated for various light sources consisting of RGB LEDs both for desktop and ceiling lighting was calculated. It is established that when using matrices containing the same LEDs distribution of illumination is very nonuniform. The inclined arrangement of LED planes slightly increases uniformity reducing the maximum illumination. For ceiling lighting the option of uniform distribution of LEDs within the ceiling plane provides more uniform illumination than when the same number of LEDs are arranged in groups of matrices.Results of LED sources modeling indicate the need to modernize simple orthogonal matrices containing the same type of elements with the same power modes for all elements in order to increase the uniformity of illumination and efficiency. Such modernization can be carried out by changing the geometry of matrices differentiating the power modes of individual LEDs. The developed calculation program can be supplemented with options for introducing the above changes, as well as options for analyzing the spectral distribution of light in space.

Influence of transmissometers’ light source spectral distribution in measuring visibility

Presently, the difference in the spectral distribution of light sources is not been sufficiently taken into account when measuring and calibrating the transmissometers. As such, the visibility measurement result cannot be to be traced to the World Meteorological Organization (WMO) definition of meteorological optical range (MOR). In this study, a method is proposed to trace the spectral distribution of transmissometers’ light sources to the 2700 K incandescent light’s spectral distribution in MOR definition. Then a traceability basis of the light source’s spectral distribution is proposed, and a model is established to determine the influence of the light source’s absolute color temperature on the MOR measurement accuracy. At the transmissometers’ typical baseline lengths of 10, 20, 30, 50, and 75 m, the absolute color temperature range and their corresponding spectral simulation error range equivalent to 2700 K incandescent lamp are obtained. Finally, the Monte Carlo method is used to simulate and analyze the MOR error corresponding to the absolute color temperature of different spectral simulation errors at five typical baseline lengths. The results show that in 10 m–600 m of MOR, the maximum simulated MOR absolute error is 42 m, which is less than 50 m, in 600 m–1500 m of MOR, the maximum simulated MOR relative error is 2.9%, which is much lower than 10% and in 1500 m–10 km of MOR, the maximum simulated MOR relative error is 18.6%, which is less than 20%, the MOR measurement accuracy is improved to the International Civil Aviation Organisation (ICAO)’s recommended requirements, thus confirming the accuracy of our theoretical research. We expect that this work will help establish the standard procedure for the SI-traceable calibration of transmissometers.

Calibration of a Hyper-Spectral Imaging System Using a Low-Cost Reference.

In this paper, we present a hyper-spectral imaging system and practical calibration procedure using a low-cost calibration reference made of polytetrafluoroethylene. The imaging system includes a hyperspectral camera and an active source of illumination with a variable spectral distribution of intensity. The calibration reference is used to measure the relative reflectance of any material surface independent of the spectral distribution of light and camera sensitivity. Winter road conditions are taken as a test application, and several spectral images of snow, icy asphalt, dry asphalt, and wet asphalt were made at different exposure times using different illumination spectra. Graphs showing measured relative reflectance for different road conditions support the conclusion that measurements are independent of illumination. Principal component analysis of the acquired spectral data for road conditions shows well separated data clusters, demonstrating the system’s suitability for material classification.

Rayleigh-Brillouin scattering in binary mixtures of disparate-mass constituents: SF_{6}-He,SF_{6}-D_{2}, and SF_{6}-H_{2}.

The spectral distribution of light scattered by microscopic thermal fluctuations in binary mixture gases was investigated experimentally and theoretically. Measurements of Rayleigh-Brillouin spectral profiles were performed at a wavelength of 532nm and at room temperature, for mixtures of SF_{6}-He,SF_{6}-D_{2}, and SF_{6}-H_{2}. In these measurements, the pressure of the gases with heavy molecular mass (SF_{6}) is set at 1bar, while the pressure of the lighter collision partner was varied. In view of the large polarizability of SF_{6} and the very small polarizabilities of He, H_{2}, and D_{2}, under the chosen pressure conditions these low mass species act as spectators and do not contribute to the light scattering spectrum, while they influence the motion and relaxation of the heavy SF_{6} molecules. A generalized hydrodynamic model was developed that should be applicable for the particular case of molecules with heavy and light disparate masses, as is the case for the heavy SF_{6} molecule, and the lighter collision partners. Based on the kinetic theory of gases, our model replaces the classical Navier-Stokes-Fourier relations with constitutive equations having an exponential memory kernel. The energy exchange between translational and internal modes of motion is included and quantified with a single parameter z that characterizes the ratio between the mean elastic and inelastic molecular collision frequencies. The model is compared with the experimental Rayleigh-Brillouin scattering data, where the value of the parameter z is determined in a least-squares procedure. Where very good agreement is found between experiment and the generalized hydrodynamic model, the computations in the framework of classical hydrodynamics strongly deviate. Only in the hydrodynamic regime both models are shown to converge.

The relationship between internode elongation of soybean stems and spectral distribution of light in the canopy under different plant densities

ABSTRACT The present study carried out with a field plot experiment and light environment simulation experiment in 2017 to assess the effect of spectral distribution on internode elongation in soybean canopy. Henong 60 and Heinong 48 were used as the experimental materials. The spectral distribution in the soybean canopy was studied under four planting densities 200,000(D20), 300,000(D30), 400,000(D40) and 500,000(D50) plant ha−1. Meanwhile, a pot experiment of light environment simulation with light-emitting diode (LED) was carried out to further analyze the effects of light quantity and quality on the elongation of soybean seedlings. The results showed that the intensity of PAR, blue light, red light and far-red light in soybean canopy decreased by varying degrees with density and canopy depth increasing, and the decrease of PAR and R/FR led to significant elongation of internodes and plant height in high density. The spectral intensity in the middle and base of the canopy was strongly reduced, resulting in the strongest internode elongation in the middle of soybean stem. The increase in soybean plant height was also mainly due to the internode elongation in the middle at high density. In addition, the mono-light of far-red light could promote the internode elongation, while the red light and blue light acted as inhibitors and the inhibitory effect of blue light was even greater.

StainedView: Variable-Intensity Light-Attenuation Display with Cascaded Spatial Color Filtering for Improved Color Fidelity.

We present StainedView, an optical see-through display that spatially filters the spectral distribution of light to form an image with improved color fidelity. Existing light-attenuation displays have limited color fidelity and contrast, resulting in a degraded appearance of virtual images. To use these displays to present virtual images that are more consistent with the real world, we require three things: intensity modulation of incoming light, spatial color filtering with narrower bandwidth, and appropriate light modulation for incoming light with an arbitrary spectral distribution. In StainedView, we address the three requirements by cascading two phase-only spatial light modulators (PSLMs), a digital micromirror device, and polarization optics to control both light intensity and spectrum distribution. We show that our design has a 1.8 times wider color gamut fidelity (75.8% fulfillment of sRGB color space) compared to the existing single-PSLM approach (41.4%) under a reference white light. We demonstrated the design with a proof-of-concept display system. We further introduce our optics design and pixel-selection algorithm for the given light input, evaluate the spatial color filter, and discuss the limitation of the current prototype.

Effects of the spatial and spectral distribution of red and blue light on Haematococcus pluvialis growth

The spatial and spectral distribution of light were essential for H. pluvialis growth and astaxanthin yield. In this work, experiments and numerical simulation with red and blue light in different ratios have been carried out on H. pluvialis. Although the light transmittance along the incident direction decreased significantly with increasing blue light ratio, the growth of H. pluvialis did not show linear relation with the absorption of blue light. Due to the red/blue light ratio of 2:1 matching the chlorophyll a/b ratio well, it produced the highest biomass and photosynthetic pigments, which were 19% and 62% higher than that under red light, respectively. The trend of maximal photochemical yield (Fv/Fm) and non-photochemical quenching (NPQ) change were similar to the content of chlorophyll and carotenoids separately. The highest carotenoids content and NPQ has been observed under red/blue light in the ratio of 2:1, which might bring H. pluvialis strong self-protection from high light and high astaxanthin yield.

Characteristics of transmission light in tetracycline hydrochloride polluted wastewater and the response of g-C3N4 under different transmission spectral range during the photodegradation process

The purification efficiency of the contaminants in the process of photocatalysis is influenced by the co-function of catalytic activity of materials, aquatic environment conditions and characteristics of transmission light. Here, tetracycline hydrochloride (TC-HCl) was introduced as the target pollutant, and the effects of different depths and TC-HCl concentrations on the transmission light intensity and spectral distribution were explored. The results show that incident light decreases with the increase of depth and pollutant concentration. The increase of depth influences the irradiance greatly, however, increase of concentration mainly lead to the narrow of transmission spectral range in the underwater field. The coupling relationship among pollutants, transmission spectral characteristics and photocatalytic reaction efficiency was discussed. Results show that the reduction of the underwater spectral range will reduce the effective response area of the material significantly, which directly leads to the reduction of pollutant removal efficiency in the degradation process. Aiming at different aquatic environment, photocatalytic materials with appropriate response spectral range should be selected to improve the light absorption ability, so that the removal efficiency can be improved significantly.

Real-Time Sensing and Control of Integrative Horticultural Lighting Systems

Optical radiation, including light, plays a crucial role in the structural development of plants through photomorphogenesis and the response to environmental changes. However, plant sensitivity to optical radiation widely varies across species. While research efforts are currently underway to discover the fundamentals of plant physiology, light sources with preprogrammed light settings (light recipes) are offered to clients to expedite plant growth. Since horticultural lighting research is in its infancy, prescribed lighting conditions are not likely to address every plants’ needs in terms of the spatial and spectral distribution, intensity, and duration of the light sources. However, it is possible to imagine an intelligent horticultural lighting system that can diagnose plants through sensors, and adjust the light intensity, the spatial and spectral distribution for the specific plant species with active feedback. Such an advanced real-time horticultural lighting system would consist of sensors to detect physiological markers from plants and environmental factors and an artificial intelligence algorithm to adjust the output. While the underlying technology for a real-time optimization system exists, the implementation and training would require further research.

The blue light dose from white light emitting diodes (LEDs) and other white light sources.

This study was carried out to determine if light emitting diodes (LEDs) represented a special case in exposing the retina to blue light, when compared with other methods of backlighting television and computer screens and with fluorescent tube lighting. The spectral distribution of light from computer and television screens (cathode ray tube, plasma screen, organic LEDs, and screens backlit by cold cathode tubes and/or LEDs), domestic type spotlights (LED and fluorescent tube) and objects in the outdoor sunlit environment were measured with a telespectroradiometer. The spectral data were analysed for the proportion of blue light and luminance. The results were also presented as time to reach the occupational safety limit, without regard to the normal 10000s time limit by which time there is no summation of exposure. The amount of blue light in a source is essentially independent of the technology of the light source, but closely related to the correlated colour temperature. Fluorescent lamps show essentially the same proportions of blue light and LEDs do not represent a special case, given the same correlated colour temperature. Blue-blocking lenses are no more needed with LED sources than with other screen illumination methods or with fluorescent lighting. There is no evidence base on which to recommend blue-blocking lenses for indoor applications.

PROBLEMS AND PROSPECTS OF LED LAMP RETROPHYTES

The article discusses modern light sources – LED retrofit lamps, which are used to replace traditional light sources (incandescent, fluorescent lamps). The article provides calculated data showing energy savings as a result of replacing traditional light sources with LED ones. LEDs have undeniable advantages over such light sources. This is a high luminous efficiency, durability, color reproduction and much more. Ample opportunities for direct replacement of LED lamps are associated with their form factor, which is the same as that of traditional light sources. The main parameters of the form factor in this case are the sizes of the light sources (bulb diameter) and the type of cap. However, direct replacement has many controversial sides. Firstly, the light environment created by traditional incandescent lamps is very different from that for LED light sources due to the difference in their spectral light distribution. Secondly, the light intensity curves of LED and traditional light sources are very different in a number of cases. Therefore, direct replacement must be carried out very carefully, taking into account the final light distribution of the light device, where they are used. Thirdly, due to the incompleteness of research in the field of safety of LED lighting, the use of such light sources can be limited due to the potential hazard that may lead to a decrease in labor productivity and quality of life. Fourth, the design of LED lamps is complex, their quality depends on the quality of LEDs, phosphors and electronics, so consumer properties may not be at the highest level, even at fairly high prices. Fifthly, for any, even the simplest LED lamp, a heat sink system is necessary, since the thermal regime of the lamps imposes certain restrictions on their use.

Light intensity and spectral distribution affect chytrid infection of cyanobacteria via modulation of host fitness.

Light gradients are an inherent feature in aquatic ecosystems and play a key role in shaping the biology of phytoplankton. Parasitism by chytrid fungi is gaining increasing attention as a major control agent of phytoplankton due to its previously overlooked ubiquity, and profound ecological and evolutionary consequences. Despite this interest, if and how light conditions modulate phytoplankton chytridiomycosis remains poorly studied. We investigated life-history traits of a chytrid parasite, Rhizophydium megarrhizum, under different light intensities and spectral compositions when infecting two closely related planktonic cyanobacteria with different light-harvesting strategies: Planktothrix rubescens and P. agardhii. In general, parasite transmission was highest under light conditions (both intensity and quality) that maximized growth rates for uninfected cyanobacteria. Chytrid encystment on hosts was significantly affected by light intensity and host strain identity. This likely resulted from higher irradiances stimulating the increased discharge of photosynthetic by-products, which drive parasite chemotaxis, and from strain-specific differences at the cell-surface. Comparisons of parasite transmission and host growth rates under different light conditions suggest the potential for epidemic development at higher irradiances, whereas host and parasite could coexist without epidemic outbreaks at lower light levels. These results illustrate the close relationship between parasite transmission and host fitness, which is ultimately modulated by the external environment.

Measurements of light transfer through drift ice and landfast ice in the northern Baltic Sea

The aim of this study was to investigate the light transfer through sea ice with a focus on bio-optical substances both in fast ice and in the drift ice zones in the northern Baltic Sea. The measurements included snow and ice structure, spectral irradiance and photosynthetically active radiation below the sea ice. We also measured the concentrations of the three main bio-optical substances which are chlorophyll-a, suspended particulate matter, and coloured dissolved organic matter (CDOM). These bio-optical substances were determined for melted ice samples and for the underlying sea water. The present study provides the first spectral light transfer data set for drift ice in the Baltic Sea. We found high CDOM absorption values typical to the Baltic Sea waters also within sea ice. Our results showed that the transmittance through bare ice was lower for the coastal fast ice than for the drift ice sites. Bio-optical substances, in particular CDOM, modified the spectral distribution of light penetrating through the ice cover. Differences in crystal structure and the amount of gas inclusions in the ice caused variation in the light transfer. Snow cover on ice was found to be the dominant factor influencing the light field under ice, confirming previous studies. In conclusion, snow cover dominated the amount of light under the ice, but did not modify its spectral composition. CDOM in the ice absorbs strongly in the short wavelengths. As pure water absorbs most in the long wavelengths, the light transfer through ice was highest in the green (549–585 nm).

Spectral differences in the underwater light regime caused by sediment types in New Zealand estuaries: implications for seagrass photosynthesis

The underwater light regime is fundamental to the ecological health of aquatic systems because it is a limiting factor for photosynthesis in marine plants such as seagrasses. Although seagrass meadows are a key component of coastal systems, their survival has been threatened by increased turbidity levels, both from resuspension of marine sediments and input of terrestrial material. The objective of this study was to investigate how marine (typically grey/white in colour) and terrestrial (typically more yellow-orange in colour with finer texture) sediments affect underwater light quality. Two experimental systems were used: (1) a large outdoor tank and (2) laboratory controlled small sampling container, using natural terrestrial and marine sediment samples (with different colours and grain sizes) from New Zealand. In the tank experiments, high concentrations of sediment reduced transmittance considerably, particularly below 450 nm. Since seagrasses absorb light optimally at wavelengths < 500 nm, as well as between 650 nm and 700 nm, the photosynthetic capacity will be less efficient with pigment absorption occurring mainly at the 650–700 nm wavebands. The difference in colour (white and grey) between marine sediments with the same grain sizes was tested in the laboratory. White sediment resulted in lower transmittance at the same concentration compared with grey sediments; concentration differences had more impact on the spectral distribution of light for white sediments. Within the ranges tested, sediment concentration contributed most to changes in overall light transmittance, with grain size being slightly less important. Sediment colour was important in changing the distribution of light, with orange and white sediments increasing attenuation of shorter wavelengths, which are most needed for seagrass photosynthesis. Our results emphasise the importance of quantifying the spectral changes to underwater light regimes in managing estuaries that are subjected to regular catchment runoff.

Optimizing vertical light spectral distribution to improve yield and quality in greenhouse fruit vegetable production

Optimizing vertical light spectral distribution to improve yield and quality in greenhouse fruit vegetable production

Influence of a Light Source Installed in a Luminaire of Opal Sphere Type on the Effect of Light Pollution

The article presents the results of the studies concerning the influence of a light source installed in luminaire of opal sphere type on the light pollution effect of the night sky. It is known from literature reports that the effect of light pollution is influenced by the spectral distribution of light. Although the influence of the spectral distribution has been widely studied from different perspectives, there is still a need to study this phenomenon—for example, from the point of view of the spectral reflection properties of the ground, on which the lanterns are installed. Hence, the above-mentioned aspect was considered in the authors’ investigations. The luminaire considered has been equipped with 20 different light sources, including the latest generation of lamps (light-emitting diodes, LEDs) as well as the conventional ones. With respect to these light sources, the measurements of light distribution and spectral distribution of emitted radiation of the luminaire were performed. Having these measurement data, the simulations were carried out using the DIALux software, and the calculations were made using the specially prepared calculation tool. On the basis of the results obtained in this way this was stated that the type of light source installed in the luminaire has a significant effect on the sky glow. An important factor affecting light pollution is not only the value of the luminous flux emitted upward but also the spectral characteristics of the emitted radiation, the impact of which is most noticeable. The conclusions from the studies indicate the next steps in the analysis of the light pollution effect. These steps will be focused on extended analysis of LEDs as modern and developed light sources.

The Impact of Dynamic Changes in Light Spectral Power Distribution on Cognitive Performance and Wellbeing

ABSTRACT The spectral power distribution (SPD) of the indoor lighting environment can improve cognitive performance, as well as positively impact occupant wellbeing. Advances in solid-state lighting now allow the SPD of indoor light sources to change temporally to better match the dynamic quality of the natural environment. The present study sought to explore how rapid, dynamic changes in light SPD can impact cognitive performance and comfort compared to traditional, static indoor light fixtures. In this study, undergraduate students completed tasks measuring attention and processing speed, as well as questionnaires of sleepiness, emotion, and headache and eyestrain under traditional static lighting or a dynamic lighting condition consisting of fluctuations in light correlated color temperature (CCT) and constant illuminance. In Experiment 1, consistent, cyclical changes in CCT (4700–5300 K in a triangular wave pattern at a frequency of 0.03 Hz) were found to negatively impact participants’ processing speed and reported ability to focus. However, these impairments were accompanied by a decrease in negative affect. In contrast, stochastic changes in CCT used in Experiment 2 (4700–5300K in semi-random changes at a frequency of 0.03, 0.07, or 0.10 Hz) produced no measured effects on participant task performance, alertness, mood, or comfort, suggesting that a degree of unpredictability in the frequency of changes in light CCT may be less disruptive to occupant performance and focus than regular, cyclical changes. The preliminary findings from this small-scale study highlight the need for further research into how changes in the lighting environment might be beneficial or detrimental to occupant performance and comfort.

Latitude and Weather Influences on Sun Light Quality and the Relationship to Tree Growth

Natural changes in photoperiod, light quantity, and quality play a key role in plant signaling, enabling daily and seasonal adjustment of growth and development. Growing concern about the global climate crisis together with scattered reports about the interactive effects of temperature and light parameters on plants necessitates more detailed information about these effects. Furthermore, the actual light emitting diode (LED) lighting technology allows mimicking of light climate scenarios more similar to natural conditions, but to fully exploit this in plant cultivation, easy-to-apply knowledge about the natural variation in light quantity and spectral distribution is required. Here, we aimed to provide detailed information about short and long-term variation in the natural light climate, by recording the light quantity and quality at an open site in Switzerland every minute for a whole year, and to analyze its relationship to a set of previous tree seedling growth experiments. Changes in the spectral composition as a function of solar elevation angle and weather conditions were analyzed. At a solar elevation angle lower than 20°, the weather conditions have a significant effect on the proportions of blue (B) and red (R) light, whereas the proportion of green (G) light is almost constant. At a low solar elevation, the red to far red (R:FR) ratio fluctuates between 0.8 in cloudy conditions and 1.3 on sunny days. As the duration of periods with low solar angles increases with increasing latitude, an analysis of previous experiments on tree seedlings shows that the effect of the R:FR ratio correlates with the responses of plants from different latitudes to light quality. We suggest an evolutionary adaptation where growth in seedlings of selected tree species from high latitudes is more dependent on detection of light quantity of specific light qualities than in such seedlings originating from lower latitudes.

Disentangling simultaneous changes of surface and illumination

Retinally incident light is an ambiguous product of spectral distributions of light in the environment and their interactions with reflecting, absorbing, and transmitting materials. An ideal color constant observer would unravel these confounded sources of information and account for changes in each factor. Scene statistics have been proposed as a way to compensate for changes in the illumination, but few theories consider changes of 3-dimensional surfaces. Here, we investigated the visual system’s capacity to deal with simultaneous changes in illumination and surfaces. Spheres were imaged with a hyperspectral camera in a white box and their colors, as well as that of the illumination were varied along “red-green” and “blue-yellow” axes. Both the original hyperspectral images and replica scenes rendered with Mitsuba were used as stimuli, including rendered scenes with Glavens (Acta Psychologica, 2009, 132, 259–266). Observers viewed sequential, random pairs of our images, with either the whole scene, only the object, or only a part of the background being present. They judged how much the illuminant and object color changed on a scale of 0–100%. Observers could extract simultaneous illumination and reflectance changes when provided with a view of the whole scene, but global scene statistics did not fully account for their behavior, while local scene statistics improved the situation. There was no effect of color axis, shape, or simulated vs. original hyperspectral images. Observers appear to be making use of various sources of local information to complete the task.

Phytochrome A Protects Tomato Plants From Injuries Induced by Continuous Light.

Plants perceive and transduce information about light quantity, quality, direction and photoperiod via several photoreceptors and use it to adjust their growth and development. A role for photoreceptors has been hypothesized in the injuries that tomato plants develop when exposed to continuous light as the light spectral distribution influences the injury severity. Up to now, however, only indirect clues suggested that phytochromes (PHY), red/far-red photoreceptors, are involved in the continuous-light-induced injuries in tomato. In this study, therefore, we exposed mutant and transgenic tomato plants lacking or over-expressing phytochromes to continuous light, with and without far-red light enrichment. The results show that PHYA over-expression confers complete tolerance to continuous light regardless the light spectrum. Under continuous light with low far-red content, PHYB1 and PHYB2 diminished and enhanced the injury, respectively, yet the effects were small. These results confirm that phytochrome signaling networks are involved in the induction of injury under continuous light.HIGHLIGHTS- PHYA over-expression confers tolerance to continuous light regardless the light spectrum.- In the absence of far-red light, PHYB1 slightly diminishes the continuous light-induced injury.- Continuous light down-regulates photosynthesis genes in sensitive tomato lines.