Luminous Intensity Distribution Research Articles

Effect of Ce<sup>3+</sup> Concentration and YAG Crystal Particles Size on Photoluminescence

Purpose of research. Determine the effect on the photoluminescence of phosphors from yttrium-aluminum garnet activated by cerium ions Ce3+, the size of its particles and the concentration of cerium ions in them.Methods. Structural electron and confocal microscopic, fluorescent, microspectral studies using a laser lex = 473 nm as an excitation source, energy dispersive, X-ray diffraction studies, as well as goniophotometric measurements on the radial distribution of light intensity excited by the LED matrix were carried out.Results. A detailed granulometric analysis of the particle sizes of phosphors was carried out for two samples from different manufacturers, cumulative distributions M(d) were constructed and their quantiles were established. Based on the results of measuring photoluminescence from individual particles in the compositions of phosphors based on YAG:Ce3+, a Stokes shift was detected in these samples: short-wavelength – for particles with sizes less than 10 μm and with low concentration and long-wavelength – with sizes greater than 10 μm with an increased concentration of over ~0.2% . The obtained microspectral size-emission dependences lem(d) and energy Imax(d) were consistent with the description based on the proposed physical mechanism of their formation by the 5d → 2F5/2 and 5d → 2F7/2 transitions.Conclusion. A short-wavelength shift of photoluminescence intensity maxima for particles smaller than 10 μm was discovered, due to a significant increase in the influence of surface stresses due to a reduction in the number of atoms. For larger particle sizes, the characteristic photoluminescence intensity maxima cease to depend on the wavelength. The radial distribution of luminous intensity determined by the goniophotometric method made it possible to calculate the value of the luminous flux equal to 1350 lm and 1140 lm, respectively, for LED matrices containing 8 LEDs with the studied phosphors.

Analysis of the General Index of Modelling in Interior Lighting

Directionality of light and modelling effects impact lighting quality in interiors. The modelling effects depend on luminaires’ photometric characteristics and their layout but also on interior size and reflectance. The objective of this research was to evaluate lighting design limitations and impact of interior and luminaires’ characteristics on the modelling effects, as well as elaborate a prediction method of the modelling effects in interior lighting. The General Index of Modelling was used for the analysis of the modelling effects in interiors. The implementation of the research objectives was based on the simulation and statistical analysis. 432 situations, varied interior size and reflectance, lighting class, luminaire downward luminous intensity distribution and layout were considered. The results show that achieving the required range of the General Index of Modelling in interior lighting is substantially limited. Luminaires’ layout impacts the General Index of Modelling the most. The elaborated multiple linear regression models can have a practical use for interior lighting design and analysis in terms of obtaining therequired range of the General Index of Modelling.

Influence of the reflector properties on the photometric characteristics of a luminaire with variable luminous intensity distribution

Influence of the reflector properties on the photometric characteristics of a luminaire with variable luminous intensity distribution

Laboratory Assessment of In-Pavement Airport Lamp’s Luminous Intensity Distribution

The luminous intensity measurements of airport navigational lighting should be performed in accordance with the recommendations of the European Aviation Safety Agency (EASA), which allows for the determination of the possibility of further operation or the need to replace particular lamps. This article presents a device and method for measuring the light main beam of in-pavement airport lamps used on runways and taxiways. During the measuring process in the laboratory dark room, the proposed system automatically prepares reports as heatmaps presenting angular relationships of light distribution. Photometric measurements were made using a BH1750 illuminance sensor, which was compared to a certified Sonopan L-200P luxmeter. The measurement stability of different BH1750 modes was investigated for different airport lamp power source thresholds. Due to distortions in spectral characteristic of BH1750, polynomial corrections were proposed. The functionality of the device was presented for the exemplary assessment of used and refurbished runway in-pavement airport lamps to compare their parameters change. The research results and device implementation were possible through scientific cooperation with the Poznań-Ławica Airport.

Method for Calculating the Asymmetric Luminous Intensity Distribution for the Road Lighting Luminaire

A method is proposed for calculating the asymmetric luminous intensity distribution of a luminaire for stationary road lighting, in which the properties of directional reflection of light from the road surface are used to the greatest extent. The method is based on the analytical relationship of the luminaire’s luminous intensity in the direction of the calculated point with the luminance of the road surface at this point in the direction of the driver, expressed in terms of the reduced luminance coefficient of this coating. The main provisions and algorithm of the method are given. The features of the calculation depending on the angle of inclination of the luminaire and the layout of the luminaires relative to the direction of movement are shown. According to a specially developed computer program, an example of calculating the asymmetric light distribution of a luminaire is executed and its effectiveness is evaluated in comparison with traditional symmetrical luminous intensity distribution.

Off-axis limiting photometric distance of Lambertians and narrow beams

The near-field - far-field disparity of light sources leads to discussion within the lighting community. In the far-field, light sources are approximated by a point source with a luminous intensity distribution from which other photometric quantities can be computed. In the near-field, light sources must be considered as extended sources and no closed-loop analytical solutions can be found for the illuminance in off-axis directions. The illuminance allows to compute the apparent intensity used for the assessment of the limiting photometric distance (LPD), that is, the threshold between near- and far-field regions. Numerically, the illuminance can be determined through a discretisation of the luminous surface. This approach is verified for on- and off-axis directions through direct comparison with ray tracing simulations based on near-field goniophotometric measurements. A good match is observed for Lambertian and narrow beam light sources. Using the numerical approach, the LPD in all directions is assessed. For light sources of which the luminous intensity strictly decreases while moving away from the optical axis, the LPD decreases as well until a minimal value is reached. After this, the LPD increases again, in certain scenarios up to values resulting in the invalidity of the inverse square law.

Determination of light direction and efficiency criterias of plexiglass diffusion light

In this study, it is aimed to determine the light direction and efficiency criteria of plexiglass diffused light sources. Within this scope, linear slots were opened in plexiglass and these slots' distances were shifted in order to analyze luminous flux, luminous intensity distribution and their effects on luminaire's efficiency. In this study the evaluations were examined in accredited laboratory with goniophotometer. As a result of the measurements, it was observed that slots in the plexiglass and distance changes in between these affect the lighting values of light source. By using these effects and the distance between the slots, a mathematical model was created with the least-square method. In this study, it was concluded that the luminous efficiency of the lighting luminaire is not only related to the light source, but also the light source that used in the luminaire is directed towards the area to be illuminated properly.

Metaheuristic of Arbitrary Luminous Intensity Distribution for Roadway Lighting Luminaires

Metaheuristic of Arbitrary Luminous Intensity Distribution for Roadway Lighting Luminaires

A Novel Way of Optimizing Headlight Distributions Based on Real Life Traffic and Eye Tracking Data Part 1: Idealized Baseline Distribution

In order to find optimized headlight distributions based on real traffic data, a three-step approach is chosen. Since the complete investigations are too extensive to fit into a single publication, this paper is the first in a series of three publications. Over three papers, a novel way to optimize automotive headlight distributions based on real-life traffic and eye-tracking data is presented, based on 119 test subjects who participated in over 15,000 km of driving, including recordings of gaze behavior, light data, detection distances, and other objects in traffic. In the present paper, a baseline headlight distribution is derived from a series of detection tests conducted under ideal conditions, with a total of three tests, each with 19–30 subjects, conducted within the same test environment. In the first test, the influence of low beam intensity on the detection of pedestrians on the sidewalk (5.0 m from the center of the driving lane) is investigated. In the second test, the influence of different high beam intensities was investigated for the same detection task. In the third test, the headlight distribution and intensity are kept constant at a representative high beam level, but the detection task is changed. In this test, the pedestrian detection target is placed along different detection angles, ranging from immediately adjacent to the road (2.5°) to 15.5 m away from the center of the driving lane (8.0°). As mentioned, all of these tests were conducted under ideal conditions, with the studies taking place on an airfield with a 1.2 km long straight road and normal road markings, but without oncoming traffic, tasks other than keeping the vehicle with cruise control within its lane, or other distracting objects present. The tests yielded two sets of data; the first is the intensity, based on the first two studies, needed to ensure sufficient intensity to detect objects under ideal conditions at distances needed for different driving speeds. The last test then uses these intensities and necessary variations in the required intensity to create an idealized, symmetric headlight distribution as a baseline for subsequent publications. Although the distribution applies only to passenger vehicles like the one used in the test, the same approach could be applied to other vehicle types. The second paper of this series will focus on real traffic objects and their distributions within the traffic space in order to identify relevant areas in headlight distribution when driving under real traffic conditions. The third paper of this series will analyze driver gaze distributions during real driving scenarios. The data from all three papers are used to create optimized headlight distributions, thereby showing how such an optimized distribution relates to current headlight distributions in terms of luminous flux, intensity, and overall distribution.

Experimental study and characteristic analysis of vacuum arc between cup-type axial magnetic contacts under different diameter-to-gap ratios

Since vacuum circuit breakers gradually advanced to higher voltage levels, axial magnetic field (AMF) contacts have drawn a great deal of attention due to their excellent breaking ability. The cup-type AMF contact is a common kind of AMF contact, which has much potential in contact design and application of high voltage grade systems due to the advantages of strong structural strength, uniform magnetic field distribution, lower resistance, etc. This study analyzes the arcing characteristics of a cup-type AMF contact with a large slotted rotation angle at various diameter-to-gap ratios (DGRs). The arcing process is divided into five stages as follows: initial diffusion, contracting, fully constricted, re-diffusion, and extinguished. Arc self-rotation and anode separation phenomena in the re-diffusion stage appear when the DGR is 58/24. The reasons for these occurrences were discussed and explained with regard to the magnetic field vector's spatial distribution. The duration of each stage and the current threshold of a fully constricted arc will both differ with the change of the DGR. The structural parameters of the fully constricted arc were computed through the method of imaging the luminous intensity distribution after the arc was fully constricted. The source of the change in the arc voltage can be seen in the variation of arc structural parameters, which also reflect anode activity intensity to a certain extent. The transient magnetic field simulation method was used to explain why the arc under the same instantaneous current shows variable morphology at the extinguished stage and contracting stage in one arcing process. The research results presented in the article can be used as a reference for developing high-voltage cup-type AMF contacts.

Udo Krüger Charts TechnoTeam's Journey

Udo Krüger Charts TechnoTeam's Journey

The Interplay between Parameters of Light Pollution and Energy Efficiency for Outdoor Amenity Lighting

This paper is related to light pollution and the energy efficiency of outdoor amenity lighting. It concerns the standard design assessment parameters of light pollution, the Upward Light Ratio (ULR) and Upward Flux Ratio (UFR), and the classic energy efficiency parameter—Normalized Power Density (NPD). The motivation for this research was the observation of certain inaccuracies related to the applicability and interpretation of these parameters in practice and the lack of connection between parameters of light pollution and energy efficiency. The multi-variant computer simulations of the exemplary large-area parking lot lighting system were conducted. Over four hundred cases were carefully analyzed. Individual cases differ in the shape of the task area, luminaire arrangements, mounting height, luminous intensity distribution, aiming, and maintenance factor. The results confirmed that the criteria values of ULR and UFR are often overestimated for modern luminaires, which emit luminous flux emitted only downwards. In this case, the ULR and UFR values do not exceed the criteria values for even zones with lower ambient brightness. Thus, lighting solutions with much lower energy efficiency easily meet the requirements of these parameters. This situation is not rational. So, it is crucial to make the criteria of ULR and UFR much more stringent in all environmental zones. Moreover, the research confirms a strong positive linear correlation between UFR and NPD (0.92, p < 0.001), which means that light pollution can be reduced by ensuring an appropriate level of energy efficiency. It is a great help in designing sustainable outdoor amenity lighting.

Omnidirectional color shift suppression of full-color micro-LED displays with enhanced light extraction efficiency.

The three-primary-color chip array is the most straightforward to realize full-color micro-LED displays. However, the luminous intensity distribution shows high inconsistency between the AlInP-based red micro-LED and GaN-based blue / green micro-LEDs, resulting in the issue of angular color shift with different viewing angles. This Letter analyzes the angular dependence of color difference of conventional three-primary-color micro-LEDs, and proves that the inclined sidewall with homogeneous Ag coating has a limited angular regulation effect for micro-LEDs. Based on this, a patterned conical microstructure array is designed on the micro-LED's bottom layer to effectively eliminate the color shift. This design cannot only regulate the emission of full-color micro-LEDs to perfectly meet Lambert's cosine law without any external beam shaping elements, but also improve the light extraction efficiency of top emission by 16%, 161%, and 228% for red, green, and blue micro-LEDs, respectively. The color shift Δ u ' v ' of the full-color micro-LED display is also kept below 0.02 with the viewing angle ranging from 10° to 90°.

Road marking BRDF model applicable for a wide range of incident illumination conditions.

To drive safely and comfortably, an adequate contrast between the road surface and road markings is needed. This contrast can be improved by using optimized road illumination designs and luminaires with dedicated luminous intensity distributions, taking advantage of the (retro)reflective characteristics of the road surface and road markings. Since little is known about road markings' (retro)reflective characteristics for the incident and viewing angles relevant for street luminaires, bidirectional reflectance distribution function (BRDF)-values of some retroreflective materials are measured for a wide range of illumination and viewing angles using a luminance camera in a commercial near-field goniophotometer setup. The experimental data are fitted to a new and optimized "RetroPhong" model, which shows good agreement with the data [root mean squared error (R M S E)<0.13, normalized root mean squared error (N R M S E)<0.04, and the normalized cross correlation ratio (N C C)>0.8]. The RetroPhong model is benchmarked with other relevant (retro)reflective BRDF models, and the results suggest that the RetroPhong model is most suitable for the current set of samples and measurement conditions.

A design‐oriented approach for managing colored light sources in lighting design software

AbstractIn the last decade, the extensive introduction of LED lighting sources has brought elements of innovation to interior lighting design in terms of color. Besides the new tunable white LED source, lighting is no longer exclusively white; indeed, colored lighting has entered the design practice thanks to the positive effects on people's health and mood. Unfortunately, this element of lighting innovation, color, cannot be computed correctly in commercial lighting design software. These computations are based on the assumption that light is only white or defined in terms of RGB triplets in the relative digital color space of computer graphics, which does not have a physically correct relationship with the actual spectral power distribution (SPD) of luminaires. In this paper, attention is focused on a practical design‐oriented approach for describing luminaires in lighting design software that also considers the real SPD and the luminous intensity distribution. The focus is on information available to lighting designers who do not have a laboratory to measure light sources and luminaires. This information could be available in online datasheets or as a Cartesian graph from luminaires and light sources manufacturers. Following this approach, a set of functions is proposed that can be easily implemented in lighting design software to improve light sources' color management and allow lighting designers to add SPD data to luminaires.

23‐2: Characterization of Directional Chromaticity of Cylindrically Curved OLED

Bending a flexible OLED panel alters the optical structure of the panel resulting in change of optical characteristics. The effects of bending on the luminous intensity distribution were analyzed and the issues were extracted, and reported in the previous publications by the first author. However, the directional chromaticity characteristics of the OLED in bent states remained. In this paper we study the on‐axis and off‐axis chromaticity characteristics of the bent OLEDs in cylindrical states. The characteristics of two OLEDs that had barrier layer thicknesses of 100 nm and 150 nm are measured at cylindrically bend curvature radii of R0=∞ mm (planar state), R2=143 mm (cylindrically curved state) and R5=56. 7 mm (cylindrically curved state). The effect of bent curvature on the directional characteristics of cylindrical OLEDs, such as emission spectrum and chromaticity are measured at specified viewing directions. The results are evaluated and discussed for the cylindrically curved OLEDs in comparison with those of the OLEDs in planar state.

Proposing a Method Reducing UGR Calculations for LED Luminaires with Diffusers in Indoor Applications

This paper studies discomfort glare in indoor LED lighting systems and proposes a method reducing UGR calculations. There are several methods for expressing discomfort glare, among which the unified glare rating (UGR) method is one of the most popular. It is safe to indicate that the UGR method was introduced before LED lighting became popular in indoor applications. Thus, the UGR method is not versatile currently. In this paper, key limitations of the UGR method are discussed. A method for reducing UGR calculations based on UGR tables for both LED luminaires with diffusers (uniform luminous intensity distribution) and with lenses is proposed. The method is mathematically discussed and its applicability for luminaires is discussed. Also, the luminaires are put through a test and the results from the tests are presented and the feasibility of the method separately from mathematical proofs is examined. The proof and case studies both indicate that the method can be used accurately for luminaires with diffusers. They also illustrate that the accuracy of applying the proposed method to the LED luminaires with lenses is not satisfactory. Simulations are carried out using DIALux lighting design software.

Simulation-based analysis of luminous environment of OLED lighting-integrated blinds for PV–OLED blind systems

Photovoltaic (PV) blinds generate power and control the sunlight entering the rooms. The control of PV blinds to maximize the power generation is disadvantageous to the indoor lighting environment as it blocks daylight. This study developed a PV–OLED blind system with an organic light-emitting diode (OLED) lighting panel attached to the back of a PV blind slat. It maximizes PV power generation, supplements indoor illuminance, and enables easy installation because it is an integrated device. A simulation modeling method of OLED, a surface-type lighting that rotates according to the blind angle, was developed and verified using measurement values. In order to apply the surface-type lighting form, a method of applying several luminous intensity distribution data files was used where we divided the height and width of one OLED lighting panel. As the number of height divisions increased, the coincidence rate with the measured values of the simulation results tended to increase. Using the proposed modeling method, the indoor illuminance distributions according to the installation position of the OLED lighting panel and the control angle of the slat were analyzed. When the slat angle was close to 60°, the influence of OLED was the greatest, and the influence of daylight decreased as the slat angle was decreased. As the slat angle increased, insufficient daylight could be compensated with an OLED lighting panel. As the OLED lighting panel was installed in the lower part of the blinds, the uniformity ratio decreased, and the average illuminance increased.

Geometric system analysis of ILMD-based LID measurement systems using Monte-Carlo simulation

Imaging Luminance Measuring Device (ILMD) based luminous intensity distribution measurement systems are an established method for measuring the luminous intensity distribution (LID) of light sources in the far field. The advantage of this system is the high-resolution acquisition of a large angular range with one image. For the uncertainty budget, the mathematical description of the system can be divided into photometric and geometric contributions. In the following, we will present a Monte-Carlo approach to analyse the geometric contributions which are the uncertainty of measurement direction and measurement distance. Therefore, we set up a geometric system description based on kinematic transformations that describes the connection between detector and light source position. To consider all relevant input quantities we simulate the adjustment and measurement process. Finally, an analysis of the geometric input parameters is shown.

On Illumination Vector Quantities Due to Area Light Sources: Comparison of Two Calculation Approaches

ABSTRACT The concept of illumination vector quantities at a given point in three-dimensional space has been proposed since long time ago, but it is mostly described for scenes with point light sources. In real scenes with area light sources, numerical approximations are required to estimate the illumination vector quantities, which can be done by discretising the area into an array of point sources. Two different approaches are proposed in this study; Approach 1 is applicable in the design phase, where the positions of the source and receiver point are exactly known. Approach 2 is applicable during field measurement, based on the obtained cubic illuminances. This study aims to determine the required number of point source elements in the computation and to investigate the difference between both calculation approaches. The proposed concept is demonstrated using a scenario with horizontal, square source and a scenario with vertical, rectangular source, with various luminous intensity distribution patterns, by observing various illumination vector quantities. Grid sensitivity analyses suggest that the largest grid size satisfying the five-to-one approximation rule shall yield quantities that converge within no more than 5% to the final value. For a given size of area source, at a given distance, the differences of illumination vector quantities obtained from both calculation approaches are expected to be approximately the same, regardless the luminous intensity distribution. The estimation of cylindrical illuminance is generally more accurate than that of scalar illuminance.