Academic literature on the topic 'COLOR RENDERING INDEX (CRI)'

Color is not a physical properly of object, but rather a human perception enabled by light. Never­theless the color of light sources is described by the industry primarily in terms of two metrics, correlated color temperature (CCT) and color rendering index (CRI), that are only indirectly related to human perception. CCT is intended to characterize the appearance of the illumination generated by source, and CRI is intended to characterize the appearance of objects illuminated be the source. There two color metrics developed nearly of half-century ago, are increasingly being challenged because new source are being developed with increasingly exotic spectral power distribution. The new color metric applicable to the color appearance of the light emitted by at light source and quantified by the CCT and D. The chromaticity is one of the critical parameters for light sources for general lighting and normally specified with chromaticity coordinates CIE (x, y) or (', '). However these two numbers do not provide the color information intuitively. For practical purposes, collated color temperature (CCT) is commonly used to provide the chromaticity information of general illumination source CCT, however, provides only one dimension of the chromaticity and there is ano­ther dimension, which is the position of chromati­city with respect to Plancian locus. For this purpose «D» or similar terms as distance from Plancian locus have been need used in some part at the industry but these had not beer officially defined is any standard. Color rendering is general term for describing the ability of a light source to provide color information to human observer when objects are illuminated by that source like CCT color rendering index (CRI), the most accepted measure of color rendering. CRI was developed, through the system of colori­metry, simply to be an indication of how «natural» or «undistorted» the light source makes the color of objects appear when illuminated by the source when used as the sole measure of color rendering for a light source, CRI simply cannot meet expectations. With the advent of SSL, these limitations have become more widely recognized. It was proposed a two-metric system combi­ning CRI, a measure of color consistency with respect to a reference source, with gamut area index (GAI), a measure of color saturation. When used to ga­ther, the two metrics appear to optimize the color appeara­nce of natural objects like fruits and vegetable enhancing their vividness with making them appear unnatural. CCT is shown in commercial instruments but D is often avai­lable. D needs to be calculated using the method of triangular solution: Create a table CCT is distance di to Plancian locus on () coordinate; Find the closest point in the table; Solve the triangle for the neighboring 2 points. Gamut area of light source is commonly calculated as the area of the polygon defined by the chromaticities in CIE 1977 (', ') color space of the light CIE TCSs. Gamut area of EES is sealed to 100 and defined as gamut area index. The gamut area of any other light source is scaled accondingle.

The correlated color temperature (CCT) tunable white-light LED cluster with extrahigh color rendering property has been found by simulation and fabricated, which consists of three WW LEDs (CCT = 3183 K), one red LED (634.1 nm), one green LED (513.9 nm), and one blue LED (456.2 nm). The experimental results show that this cluster can realize the CCT tunable white-lights with a color rendering index (CRI) above 93, special CRI R9 for strong red above 90, average value of the special CRIs of R9 to R12 for the four saturated colors (red, yellow, green, and blue) above 83, and luminous efficacies above 70 lm/W at CCTs of 2719 K to 6497 K.

High color rendering index performance has been required for phosphor-converted warm-white light-emitting diodes (PC-WWLEDs) in lighting industry. The characteristics of low-temperature fabricated phosphor (yellow: Ce3+:YAG, green: Tb3+:YAG, and red: CaAlClSiN3:Eu2+) doped glass were presented for applications to high color rendering index warm-white-light-emitting diodes. Color coordinates (x, y) = (0.36, 0.29), quantum yield (QY) = 55.6%, color rending index (CRI) = 85.3, and correlated color temperature (CCT) = 3923 K were characterized. Glass-based PC-WWLEDs was found able to maintain good thermal stability for long-time high-temperature operation. QY decay, CRI remenance, and chromaticity shift were also analyzed for glass- and silicone-based high-power PC-WLEDs by thermal aging at 150°C and 250°C for industrial test standard’s aging time 1008 hours. Better than the silicone’s, thermal stability of glass-based PC-WLEDs has been improved. The resulted high color rendering index (CRI) glass phosphor potentially can be used as a phosphor layer for high-performance and low-cost PC-WLEDs used in next-generation indoor solid-state lighting applications.

We demonstrate a phosphor free, dichromatic GaN-based monolithic white LED with vertically stacked green and blue emitting multiple quantum wells. The optimal thickness of GaN barrier layer between green and blue quantum wells used is 8 nm. This device can be tuned over a wide range of correlated color temperature (CCT) to achieve warm white (CCT = 3600 K) to cool white (CCT = 13,000 K) emission by current modulation from 2.3 A/cm2 to 12.9 A/cm2. It is also demonstrated for the first time that a color rendering index (CRI) as high as 67 can be achieved with such a dichromatic source. The observed CCT and CRI tunability is associated with the spectral power evolution due to the pumping-induced carrier redistribution.

In order to assess the performances of different color rendering index (Ra, CRI, CQS, nCRI, R96a). The LED (light-emitting diode), fluorescent light sources and 30 printed color samples were used in our experiment. 20 observers were organized to carry out the color preference experiment, the visual data were accumulated to test the performances of the light sources and the results indicated that existing color rendering index have some deficiencies to assess the quality of the light source, which were needed to be modified for the theory of color science and industry application. The new CQS additional scales were calculated and the improvements were still insufficient for the LED light sources.

The TeO2 layer endowed bifacial semitransparent organic photovoltaics (ST-OPVs) with improved values of average visible transmittance (AVT), light utilization efficiency (LUE), bifaciality factor (BF) and color-rendering index (CRI).

The TeO2 layer endowed bifacial semitransparent organic photovoltaics (ST-OPVs) with improved values of average visible transmittance (AVT), light utilization efficiency (LUE), bifaciality factor (BF) and color-rendering index (CRI).

This ultra-simple di-chromatic WOLED, using only three organic materials, achieves an ultra-high CRI of 90, which is even comparable with other reported three-color, four-color, and five-color WOLEDs.

Recent advances in solid state lighting (SSL) technology have encouraged its utilization in versatile applications. SSL technology based on phosphor converted light emitting diodes (pc-LEDs) are acting potentially as a substitute for traditional incandescent and fluorescent lamps on an account of their unprecedented luminous efficiency, low energy consumption, less emission of harmful gases, high brightness, compact design, fast switching and long working lifetimes. The pc-LEDs utilize phosphors coated on the LED chip capable of emitting light in desirable spectral regions upon an appropriate excitation. In the light of the above mentioned advantages, pc-LEDs are believed to be the next generation SSL technology and will bring a revolutionary changes in the lighting industry. For example, the white pc-LEDs have been the most preferred lighting devices for general illumination due to effective energy utilization, long lifetime, safety and so on. Moreover, pc-LEDs can be harnessed for indoor agricultural lighting owing to their excellence in controlling the spectral composition and lighting intensity to mimic the changes of sunlight during the day. Therefore, all the above mentioned fascinating features like effective energy saving and desirable light emission have enabled pc-LEDs to become economically feasible choice for general illumination and large scale indoor agricultural lighting applications around the corners of the world. The phosphor based w-LEDs can be developed by (i) coating of appropriate mixture of red, green and blue (RGB) phosphors excited with UV LED chip (ii) single yellow phosphor by a blue LED chip. However, reabsorption of blue color by RG phosphors in the former approach and lack of red component in later approach may lead to shortcomings like low color saturation, deteriorated color rendering index (CRI) and low color temperature stability. To overcome the above mentioned shortcomings, it is necessary to develop single phase phosphor doped with appropriate combination of rare earth ions (such as Dy3+/Eu3+, Tb3+/Eu3+ , Tb3+/Sm3+, Dy3+/Sm3+ etc.) providing white light emission via energy transfer or new red vii phosphor for the improvement of performance factors like luminous efficiency, CRI and correlated color temperature (CCT). Further, for plant growth under controlled environment fitted with smart pc-LEDs, it is necessary to conduct a widespread research for deep-red, far- red and blue light emitting phosphors that can be utilised to best drive photosynthetic metabolism and photo-morphogenesis as per the literature survey. Therefore, the ascending demand of energetically efficient lighting devices for general illumination and plant growth applications has led to a significant interest in the development of novel high quality phosphors with superior brightness, multiple emission color and excellent color purity. Besides lighting, the phosphors facilitate their utilization in diverse applications such as solar cells, bio-sensing and other optoelectronic devices due to their versatile physical, chemical and luminescent properties. In general, phosphor consisting of a host matrix (crystalline host) and an activator (luminescent center) have been pondered as a technologically significant components for the development of w-LEDs and agricultural lighting systems. In the past few decades, inorganic phosphors activated with rare earth (RE) ions have remained the prevalent protocol for fabricating pc-LEDs due to unique luminescence properties of RE ions. In such phosphors, the intermixing of oxygen atomic orbitals of host with orbitals of RE ion creates a specific crystal field environment around it such that transitions between incompletely filled 4f energy levels of RE ions deliver distinctive luminescence features. Also, the efficient energy transfer from the host crystal to the RE activators have been investigated to comprehend interesting optical phenomena. Among all the various inorganic oxides, vanadates have attracted acquiescent utilization in the wide-spread of luminescent device applications due to their wide-range of excitation wavelengths with abundant luminous colour, good physical and chemical stability. In addition, the vanadate materials are cost-effective and their preparation methods are energy efficient. The vanadate based phosphors give a broadband emission originating from inherent [VO4] 3- group. The broadband emission in the visible range by vanadate hosts can bring viii improvement in CRI and CCT values. Recent investigations have been established the possibility of achieving tunable visible emissions in RE activated vanadate phosphors via controlling [VO4] 3- to RE ions energy transfer. To harness the above mentioned precedencies, an investigation on a new ternary vanadate (CaBiVO5) phosphor doped with RE ions has been done for general and agricultural lighting applications. By incorporating suitable RE ions, the present host (CaBiVO5) can be tuned to emit different colors in the visible region suitable for pc-LEDs used in general illumination and agricultural lighting applications. Based on the extensive structural, morphological and photoluminescence characterizations, the outcome of the research work for accomplishing the research objectives has been organized in seven chapters. The brief summary of each chapter is as follows: Chapter 1 highlights the brief history, motivation, an outlook on the recent developments, potential challenges and great opportunities in white light generation and agricultural lighting. This chapter explains the basic concepts related to luminescence, spectroscopic features of RE ions, theoretical models implemented for examining the observed spectral data, and possible energy transfer processes. This chapter also present a brief viewpoint on the various characteristics and indices such as chromaticity coordinates, color purity, CCT and activation energy describing the color quality, thermal stability and performance of pc-LEDs. The importance of the present work and selected vanadate host have been discussed briefly in this chapter. At the last, the objectives of the thesis based on literature review have been included. Chapter 2 makes a thorough discussion about the different synthesis methods opted for the synthesis of single phase calcium bismuth vanadate (CaBiVO5: CBV) phosphors activated with different RE ions (Eu3+, Sm3+, Pr3+ and Dy3+). It also explicates the basic principle and working of experimental techniques employed to explore structural, morphological, optical and luminescent properties of CBV phosphors. The thermal and structural properties are studied by thermogravimetric analysis (TGA) and X-ray Diffraction (XRD) method, respectively. The ix scanning electron microscopy (SEM) reveals the morphology of the as synthesized phosphors. The optical properties are determined from diffuse-reflectance (DR) spectral measurements, while photoluminescence properties, thermal stability and decay kinetics of the CBV phosphors doped with different RE ions were investigated using spectrofluorophotometer. All these characterization techniques have been discussed in this chapter. Chapter 3 describes about the synthesis of single phase Eu3+ activated calcium bismuth vanadate (CaBiVO5) phosphors using solid state reaction method. X-ray diffraction (XRD) analysis confirms the pure phase formation and scanning electron microscope (SEM) micrographs exhibit inhomogeneous particle formation with irregular morphology of Eu3+ doped CaBiVO5 (CBV) phosphor. The photoluminescence excitation (PLE) spectrum indicates significant absorption in the ultraviolet (UV) and near ultraviolet (n-UV) spectral regions for un-doped CBV sample, whereas Eu 3+ doped CBV phosphors reveal various sharp absorption bands in n-UV and blue region along with host absorption bands. Trivalent europium activated CBV phosphors under 342 nm excitation exhibit dominant red emission peak at 613 nm wavelength accompanied by weak broadband originating from VO4 groups, whereas the phosphors under 464 nm excitation, exhibit similar emission profile with most intense one centered at 613 nm by excluding host emission bands. The energy transfer mechanism and the probable cause for concentration quenching beyond 4.0 mol% of Eu3+ ions concentration have been discussed in detail. The CIE chromaticity coordinates for the optimized phosphor, (0.551, 0.398) and (0.639, 0.358), situated in the reddish-orange and red region under 342 and 464 nm excitations, respectively. The CIE coordinates calculated based on the emission spectra measured under 464 nm excitation are close to the commercial phosphor Y2O2S: Eu3+ (0.622, 0.351). All the above mentioned results support the utilization of Eu3+ doped CBV phosphor as a potential red emitting component for luminescent devices. x The research work described in this chapter has been published in “Ceramics International 45 (2019) 15385-15393” (Impact factor =4.527) Chapter 4 describes the optimization of synthesis procedure for Sm3+ doped CaBiVO5 phosphor by preparing through it via three different synthesis methods, solid-state reaction (SR), combustion (CB) and citrate sol-gel (SG) method to enhance the luminescent properties. The pure phase formation of CBV: Sm3+ phosphors via diverse routes (SR, CB and SG) is confirmed as diffraction peaks for all prepared phosphors correspond to the standard data (JCPDS card no: 81-1775). The SEM results reveal that CBV: Sm3+ phosphors are synthesized with improved homogeneity and shape regularity at lower reaction temperature via SG method. The excitation spectra measured by monitoring the emission at 649 nm for CBV: Sm3+ phosphors reveal significant absorption in ultraviolet (UV), near (n)-UV and blue spectral regions. The comparative photoluminescence (PL) spectra measured under 343 nm excitation for differently synthesized CBV: Sm3+ phosphors, which exhibit significantly enhanced emission intensity for SG derived phosphor than other adopted methods. The PL spectra for SG derived 1.0 mol% Sm3+ doped CBV phosphor at λex = 275 and 343 nm exhibit sharp peaks located at 566, 606 and 649 nm along with weak host emission broadband and for λex = 406 nm, similar sharp peaks of Sm3+ transitions are observed without any host emission. Unlike mostly explored Sm3+ doped phosphors, emission peak in red spectral region (649 nm) is more intense as compared to the emission peak in orange region (599 nm) in the present work. The energy transfer mechanism responsible for concentration quenching in CBV phosphors is discussed in detail. The CBV: Sm3+ phosphors manifest color tunability from orange to orange- red region by modulating excitation from 275 nm (0.567, 0.404) to 343 nm (0.591, 0.399) and finally to 406 nm (0.620, 0.376). The temperature-dependent PL studies indicate appreciable thermal stability of as-prepared phosphor. Above mentioned results suggest that CBV: Sm3+ phosphor has great potential for use in white light-emitting diode (w-LED) applications. xi The research work described in this chapter has been published in “Optical Materials 107 (2020) 110119” (Impact factor =3.080). Chapter 5 describes the citrate sol-gel synthesis of Dy3+ activated and Dy3+/Eu3+ bi-activated calcium bismuth vanadate (CBV) phosphor to achieve white light emission and color- tunability. The phase purity and quasi-spherical particle with few agglomerations of the as- prepared CBV phosphors are indicated by structural and morphological characterizations, respectively. The emission spectral properties and energy transfer in Dy3+ doped and Dy3+/Eu3+ co-doped CBV phosphors have been examined extensively. The Dexter and Reisfeld’s approximation applied to emission spectra specifies electric dipolar-dipolar interaction to be accountable for Dy3+ to Eu3+ energy transfer. In CBV: Dy3+ phosphors, co-doping with Eu3+ ion facilitates red component that ensues warm white light emission as well as flexible color tunability with increasing Eu3+ ion concentration under different excitations. The significant findings like warm white light emission and controllable spectral composition in Dy3+/Eu3+ co- doped CBV phosphor by altering the excitation energy and co-dopant (Eu3+) concentration potentiate it as a suitable candidate in the domain of lighting and display devices. The research work described in this chapter is communicated to an Internationally reputed Journal “Solid State Sciences (2021)” (Impact factor = 3.059) Chapter 6 describes about orthorhombic Pr3+ -doped calcium bismuth vanadate (CBV: Pr3+) phosphors synthesized via citrate-gel method. The single-phase formation of CBV: Pr3+ phosphor has been endorsed by XRD analysis. The SEM image reveals dense-particle packaging with the quasi-spherical shape for the prepared CBV: Pr3+ phosphors. Under blue light excitation, CBV: Pr3+ phosphors exhibit intense red emission bands located at 608 and 656 nm wavelengths, overlapping with the absorption spectrum of PR phytochrome, which is present in plants. To achieve the maximum red intensity, the Pr3+ ion concentration is optimized xii to be 1.25 mol% in the CBV host, after which the emission intensity ceases due to the concentration quenching. Dexter's theory disclosed the possibility of d-d multipolar interaction among Pr3+ ions at higher concentrations of Pr3+ ions in the CBV host. The CIE coordinates are found to be positioned in the pure red region for CBV: Pr3+ phosphor and in the proximity of red-emitting commercial phosphor. The temperature dependent spectral studies manifest substantial thermal stability of the as-synthesized phosphor. All the studies mentioned above specify the tremendous potentiality of thermally stable CBV: Pr3+ phosphor in agricultural lighting and w-LED applications. The research work described in this chapter has been accepted to publish in “Journal of the American Ceramic Society 104 (2021) 5764-5775” (Impact factor =3.784). Chapter 7 summarizes the research outcomes of the work described in chapters 3 to 6 and outline the future scope of the thesis work for the expected applications.

Tunable white-armaturer utgör idag en stor del av marknaden och förväntas öka ytterligare under de kommande åren. Då många leverantörer idag producerar och marknadsför sina egna lösningar för att skapa ett dynamiskt ljus kan det vara svårt att veta vilken standard dessa lösningar håller och hur väl den tekniska specifikationen stämmer överens med verkligheten. Syftet med denna studie har varit att undersöka om informationen mot beställare är tillräcklig samt om den redovisade data av Tunable White-armaturer är korrekt. Studien bygger på två delar. En experimentell undersökning genomfördes där fem tunable white-armaturers CRI (färgåtergivning) mättes mellan olika CCT-nivåer (färgtemperatur) och sedan jämfördes det med vad leverantörer har specificerat på deras hemsidor. En enkätundersökning genomfördes sedan som riktades mot 144 ljusdesigners i Sverige, varav 52 valde att besvara enkäten. Frågorna berörde redovisning av Tunable white-armaturer samt vikten av en god ljuskvalitet med inriktning på CRI. Resultaten från författarnas experimentella undersökning visar att alla tunable white-armaturer som testades skiftar i CRI under olika färgtemperaturintervaller. Den största skillnaden som mättes var på fabrikat 3 där det skiftade 9 CRI mellan 2700K-6000K. En jämförelse kunde sedan göras och visade att två av fem leverantörers specifikationer inte stämmer överens med vad som redovisats i respektive produktdatablad. Av att tyda svaren från enkätundersökningen kunde slutsatsen dras att det finns mycket skilda åsikter angående de tekniska specifikationerna gällande tunable white-armaturer. En del ansåg att det redovisas tillräckligt väl idag medan andra ansåg att det inte redovisas tillräckligt väl. Majoriteten ansåg att det är mycket viktigt med en god CRI när man föreskriver tunable white-armaturer i sina projekt. Man kunde också se att många ljusdesigners önskade att man redovisade färgåtergivning i TM-30-15 istället för CRI-metoden eller att man bör redovisa i givna färgtemperaturer. Det som kan fastställas av denna studie är att det finns en tendens till att vissa armaturleverantörer har sämre CRI än vad företaget i fråga redovisat. Denna studie enbart mätt TW-armaturer från fem företag verksamma i Sverige samt endast vid 100% ljusflöde. Författarna anser dock att denna studie kan leda till en diskussion om bättre redovisning av tunable white-armaturer behövs, samt ge läsaren en ökad förståelse för komplexiteten inom området.
Tunable white luminaires today form a large part of the market and are expected to increase further in the upcoming years. As many manufacturers today produce and market their own solutions to create a dynamic light, it can be hard to know what quality these solutions have and how well the technical specification is. The purpose of this study were to investigate whether the information to the user is sufficient and whether the presented data of tunable white luminaires is correct. This study is based on two parts. An experimental study where five tunable white luminaires CRI (color rendering) were measured between different CCT levels (color temperature) and then compared these to what providers have specified on their websites. The second part was a survey was conducted to 144 lighting designers based in Sweden, 52 of whom chose to answer the questionnaire. The questions concerned the presented information of tunable white luminaires as well as the importance of a good light quality focusing on CRI. The results from the authors experimental survey showed that all tunable white luminaires that where tested are changing in CRI under different color temperature intervals. The biggest difference that was measured was on manufacturer 3 where 9 CRI shifted between 2700K-6000K. A comparison could be made and showed that two of five of the suppliers specifications did not match with the authors measurements. By analyzing the answers from the survey, some conclusions could be drawn. There were very different opinions regarding the technical specifications of tunable white luminaires. Some felt that it is enough as it is today, while others felt that more information was needed. The majority considered it very important to have a good CRI when selecting tunable white luminaires in their projects. One could also see that many lighting designers wanted to present color reproduction in TM-30-15 instead of the CRI method or to present CRI at given color temperatures. What can be determined by this study is that there is a tendency for some luminaire suppliers to have worse CRI than presented. This study only measured tunable white fixtures from five companies operating in Sweden and only at 100% luminosity. However, the authors consider that this study could lead to a discussion about better specifications for tunable white luminaires, as well as giving the reader an increased understanding of the complexity of the subject.

Organic semiconducting materials have received a lot of attention in recent years and can now be found in many applications. One of the applications, the light emitting electrochemical cell (LEC) has emerged due to its flat and lightweight device structure, low operating voltage, and possibility to be fully solution processed. Today LECs can emit light of various colors, but to be applicable in the lighting industry, white light need to be produced in an efficient way. White light on the other hand, is one of the toughest "colors" to achieve in an efficient way, and is of particular interest in general lighting applications, where high color-rendering index devices are necessary. In this thesis I show that blue light can be partially converted, into white light, by utilizing the photoluminescence of color conversion layers (CCLs). Furthermore, I show that a high color-quality white light can be attained by adopting a blue-emitting LEC with a CCL. Particularly, three different color-conversion materials were embedded onto a blue bottom-emitting LEC, to study the resulting spectrum. One of the materials, MEH-PPV, have good absorption compatibility with the electroluminescence of the blue emitters, but the materials photoluminescence do not cover the red to deep-red range of the spectrum. These parts of the spectrum are necessary to obtain high color rendering indices (≥80). A single layer of MEH-PPV adapted onto a blue-emitting LEC, led to a cold white LEC with CIE-coordinates x = 0.29, and y = 0.36, color-rendering index = 71, and correlated color temperature = 7200 K. These properties makes it potentially useful in outdoor-lighting applications. The photoluminescence of another studied color-converting material, polymer red, covers the red to deep-red range of the spectrum but the material lacks absorption in the green parts of the blue emitters electroluminescence spectrum. Thus it is necessary to combine it with MEH-PPV to be able to absorb all wavelengths from the blue-emitter and get a broad light-spectrum out of the device. In order to preserve a part of the blue light, a new device configuration was designed. It features a top-emitting blue LEC with a dual-layer CCL which reach an impressive color rendering index = 89 at a correlated color temperature = 6400 K (CIE-coordinates x = 0.31, y = 0.33). The color-rendering index is the highest reported for a white LEC. The absence of UV-, and IR-radiation, together with the high color rendering properties make the white LEC a possible candidate for even the most demanding lighting-applications, such as art galleries, and shop display windows, together with indoor lighting. In this thesis, I show that the CCLs function well. However, for the LECs to be worthy competitors, the efficiency and lifetime of the blue emitter need improvements.

Cette thèse a été réalisée en parallèle avec le projet de recherche « ENG05 lighting », un programme européen de recherche en métrologie réunissant une quinzaine d’instituts nationaux de métrologie en Europe. L'apparition de nouvelles solutions d’éclairage utilisant des diodes à électroluminescence (DEL) n’apporte pas seulement une efficacité en termes de diminution de puissance consommée mais elles doivent également répondre à des critères dequalité delumière pour l’utilisateur selon l’environnement.L'étude se concentre sur les problématiques du confort visuel ainsi que sur les indices du rendu des couleurs conformes à ceux de la Commission International de l'Eclairage (CIE) qui ne permettent pas de prédire une évaluation fiable en ce qui concerne ces nouveaux éclairages à l’état solide.Cette recherche s’appuie sur les calculs informatisés des métriques existantes, les résultats de plusieurs expériences subjectives réalisées dans un environnement contrôlé et reproductible et leurs caractérisations. Un premier modèle capable de prédire le confort visuel d'un scénario d'éclairage est réalisé et décrit. Plusieurs axes d'amélioration des métriques du rendu des couleurs sont étudiés.L'ensemble des expériences intègre des solutions d'éclairages traditionnelles. A l’aide de carte de luminance, les résultats obtenus sont comparés aux performances des sources respectives.Mots-clefs : Rendu des couleurs, confort visuel, qualité des éclairages, expérience subjective, DEL, DEL, UGR, IRC, CRI, éblouissement, carte de luminance
The ENG05 project funded by the European Research Metrology Programme (EMRP) addresses measurement aspects of both quantity and quality of new lighting such as solid-state lighting (SSL).The current Colour Rendering Index (CRI) of the CIE (International Commission on Illumination) fails to predict the subjective ranking of the lighting sources based on DEL (light emitting diode). Along with a study of colour rendering metrics based on an extensive computation of relevant metrics and colorimetric calculations, a study on visual comfort is performed and both are presented in this thesis.For interior lighting standards it doesn’t exist a metric able to predict the visual comfort of an environment. Therefore, the aim of this study consists in a contribution to the human visual comfort characterization according to various realistic configurations considering the comparison between DEL luminaries and traditional lighting technologies (fluorescent, halogen).The analysis of the results DEL to develop a model which could be deemed worthy of consideration by CIE.Keywords: color rendering, visual comfort, lighting quality, subjective experiment, DEL, UGR, CRI, glare, luminance maps

A new red emitting phosphors based on oxyfluoride glass and glassceramics doped with europium and manganese ions were synthesized and their optical properties and structure were studied. The transparent ceramic matrices for phosphors were selected because they overcome traditional powder phosphors due to high chemical and thermal stability and low temperature sensitivity. The fluoride based red emitting phosphors combined with green one and blue emitting chip used to fabricate phosphor converted white LEDs with warm color temperature and improved color rendering indexes. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35375

A solar fiber optic lighting system, SP3 from the Swedish company Parans Solar Lighting AB, has been installed in a study area/corridor test site. A collector is tracking the sun during daytime, focusing the direct sun irradiance via Fresnel lenses into optical fibers, which guide the solar light into the building. The illumination properties of the system have been characterized. The energy saving due to reduced need of artificial lighting have been calculated and methods for balancing the artificial lights in the test site have been evaluated. The illumination at the test site using solar light was at least as high as when using the artificial lights and even higher at very clear days. The luminous flux output (500 lm) was somewhat lower than specified by the manufacturer (550 lm) at 100 000 lx direct sun illuminance. The output at 130 000 lx was high 767±33 lm the sunlight coupling efficiency 23 %. However, for a 20 m SP3 system the luminous flux output (400 lm) at 100 000 lx was higher than specified (350 lm). The SP3 system of Parans provides high quality solar light. It has a fuller spectrum close to the spectrum of the sun compared to the fluorescent lights at the test site. The correlated color temperature of the system was 5800±300 K and the color rendering index 84.9±0.5. The lighting energy saved due to decreased need for artificial light was estimated to 19 % in Uppsala which has 1790 annual sun hours. The savings in Italy, which has 3400 sun hours, is 46 %. Additional saving, especially in warmer countries can be obtained due to decreased need for cooling in the building as the solar luminaires provide negligible heat to the indoor air. Economical saving could also be realized by improved well-being of the occupants spending time under the solar luminaires. Three ways of balancing the artificial light due to sunshine fluctuations have been investigated. The global horizontal irradiance could not be used as a control signal for balancing the artificial lights but a pyranometer attached to the SP3 sun tracking collector was usable. Also the signal from an indoor luxmeter sensor could be used for balancing the light. However the signal from the light sensor which makes the SP3 collector to track the sun is probably the most cost effective method as it would serve two purposes; tracking the sun and balancing the artificial lights.

This thesis deals with the processing of light technical parameters and performance of key LED chips for their applications in lighting systems. The aim is to create a laboratory model for measuring the qualitative and quantitative parameters of highly luminous light LED emitted depending on the angle, using a spherical integrator 0.3 m, goniometer and fiber spektroradiometr /luxmeters. Goniometer is designed using modular optomechanical parts company Thorlabs. Due to the current passing through the LED chips heat up considerably. To light LED chip parameters tested were not affected by heat from the chip is required to pay the heat generated by a passive radiator. Another part of this thesis is the reconstruction of an older model spherical integrator. Reconstruction must be undertaken so as to ensure sufficient cooling again tested LEDs. Light scattered in the ball of the integrator is led by the optical cable to the spektroradiometr that are subsequently recorded its parameters. The second element used to measure the light produced by the LED source is photocell. Spherical integrator must be appropriately modified to indicate the two measuring elements and also meet the standards of determining the correctness of measurement. At the end of the measurement results will be compared with catalog values provided by the manufacturer.

Актуальність теми. Актуальною задачею комп’ютерної графіки являється отримання реалістичних зображень, котрі активно користуються попитом в промисловості, ігровій індустрії та кіно. Фотореалістичне зображення характеризується такими ефектами, як м’які тіні, напівтіні, каустика, динамічне розмиття, глибина різкості, нечіткі відбиття, блиск, напівпрозорість. Серед існуючих підходів фотореалістичної візуалізації методи трасування променів являються найбільш точними, оскільки вони базуються на фізичній моделі поширення світла. Існує багатий спектр різноманітних методів трасування променів, отже з’являється необхідність у вибірці найбільш ефективних точних методів трасування променів, котрі будуть в середній мірі коректно працювати для широкого ряду статичних (в майбутньому і динамічних) сцен, що проходять візуалізацію. Об’єктом дослідження є процес фізично обґрунтованого рендерингу і процес трасування променів. Предметом дослідження є способи трасування променів та методи розрахунку індексу передачі кольору. Мета роботи: дослідження методів PBR (Physical Based Rendering), їх одночасного використання для отримання максимального ефекту реалізму; оцінка здатності джерела світла виявляти всі частоти його кольорового спектру у порівнянні з контрольним світлом. Наукова новизна, а точніше – інноваційне рішення полягає в тому, що розроблений рушій реалізує обчислення індексу передачі кольору (CRI - Color Rendering Index) з високим рівнем точності відносно очікуваних значень контрольних джерел світла. Практична цінність проведених досліджень полягає у розробці нового PBRE, який для рендерингу сцен використовує емпіричні моделі освітлення; реалізовані такі моделі BRDF, як Ламберта, Орена Найара, Торренса Спарроу, дзеркального відбиття, дзеркального пропускання і виміряного BRDF. Реалізована підтримка декількох технік трасування променів: трасування Уайтеда і трасування шляху. Розраховуються кольори з використанням спектральних даних і колірний простір CIE XYZ в сценах PBR для досягнення високої передачі кольору. TTFD також підтримує обчислення індексу передачі кольору (CRI – Color Rendering Index). Цей показник описує здатність джерела світла точно відображати всі частоти його колірного спектра в порівнянні з ідеальним еталонним світлом аналогічного типу. Структура та обсяг роботи. Магістерський дипломний проект складається зі вступу, чотирьох розділів та висновків. У вступі подано загальну характеристику роботи, зроблено оцінку сучасного стану проблеми, обґрунтовано актуальність напрямку досліджень, сформульовано мету і задачі досліджень, показано наукову новизну отриманих результатів і практичну цінність роботи. У першому розділі розглянуто принципи колориметрії та радіометрії. Вони складають основу деяких основних ключових особливостей TTFD. Зокрема, розрахунок кольору і методи освітлення / затінення, реалізовані в TTFD, використовують поняття, представлені даному розділі. У другому розділі розглянуто трасування променів: фотореалістичний рендеринг (візуалізація). Коротка класифікація алгоритмів трасування променів. Вирішення рівняння рендеринга. У третьому розділі наведено особливості реалізації розробленої системи. У четвертому розділі представлено підходи до тестування системи в цілому та окремих модулів. У висновках представлені результати проведеної роботи. Робота представлена на 116 аркушах, містить посилання на список використаних літературних джерел. Ключові слова: фізичний рендеринг (PBR), трасування променів, індекс передачі кольору, емпіричні моделі освітлення, модель Уайтеда, трасування шляху.
Relevance of the topic. The actual task of computer graphics is to obtain realistic images that are actively in demand in industry, gaming and film industry. A photorealistic image is characterized by such effects as soft shadows, partial shade, caustic, dynamic blur, depth of field, fuzzy reflection, shine, translucency. Among the existing approaches of photorealistic visualization, ray tracing methods are the most accurate because they are based on a physical model of light propagation. There is a wide range of different ray-tracing methods, and therefore there is a need to select the most efficient, accurate ray-tracing methods that will, in average, work correctly for a wide range of static (future dynamic) scenes, and are being visualized. The object of the research is the process of physically sound rendering and the ray tracing process. The subject of research is the methods of ray tracing and methods for calculating the color rendering index. Objective: to study the methods of PBR (Physical Based Rendering), their simultaneous use to obtain the maximum effect of realism; assessment of the ability of a light source to detect all the frequencies of its color spectrum compared to the control light. The scientific novelty, or rather, an innovative solution, is that the engine developed implements the calculations of the color rendering index (CRI - Color Rendering Index) with a high degree of accuracy relative to the expected values of the control light sources. The practical value of the research is the development of a new PBRE, which employs empirical lighting models for rendering scenes; BRDF models such as Lambert, Oren Nayar, Torrens Sparrow, specular reflection, specular transmission and measured BRDF are implemented. Implemented support for several ray tracing techniques: Traced by Wyted and path tracing. Colors are calculated using spectral data and CIE XYZ color space in PBR scenes to achieve high color rendering. TTFD also supports Color Rendering Index (CRI) calculations. This indicator describes the ability of a light source to accurately reflect all the frequencies of its color spectrum compared to ideal reference light of a similar type. Structure and scope of work. Master thesis project consists of introduction, four chapters and conclusions. The introduction presents a general description of the work, assesses the current state of the problem, substantiates the relevance of the research area, formulates the goals and objectives of the research, shows the scientific novelty of the results and practical value of the work. The first section discusses the principles of colorimetry and radiometry. They form the basis of some key TTFD key features. In particular, color calculations and lighting / shading methods implemented in TTFD use the concept presented in this section. The second section deals with ray tracing: photorealistic rendering (visualization). Brief classification of ray tracing algorithms. Solution of the rendering equation. The third section presents the features of the implementation of the developed system. The fourth section presents approaches to testing the system as a whole and individual modules. The findings present the results of this work. The work is presented on 116 pages, contains links to the list of references used.
Актуальность темы. Актуальной задачей компьютерной графики является получение реалистичных изображений, которые активно пользуются спросом в промышленности, игровой индустрии и кино. Фотореалистичное изображение характеризуется такими эффектами, как мягкие тени, полутени, каустика, динамическое размытие, глубина резкости, нечеткие отражение, блеск, полупрозрачность. Среди существующих подходов фотореалистичной визуализации методы трассировки лучей являются наиболее точными, поскольку они базируются на физической модели распространения света. Существует богатый спектр различных методов трассировки лучей, следовательно появляется необходимость в выборке наиболее эффективных точных методов трассировки лучей, которые будут в средней степени правильно работать для широкого ряда статических (в будущем и динамических) сцен, проходят визуализацию. Объектом исследования является процесс физически обоснованного рендеринга и процесс трассировки лучей. Предметом исследования являются способы трассировки лучей и методы расчета индекса цветопередачи. Цель работы: исследование методов PBR (Physical Based Rendering), их одновременного использования для получения максимального эффекта реализма; оценка способности источника света выявлять все частоты его цветового спектра по сравнению с контрольным светом. Научная новизна, а точнее - инновационное решение, заключается в том, что разработан двигатель реализует вычисления индекса цветопередачи (CRI - Color Rendering Index) с высокой степенью точности относительно ожидаемых значений контрольных источников света. Практическая ценность проведенных исследований состоит в разработке нового PBRE, который для рендеринга сцен использует эмпирические модели освещения; реализованы такие модели BRDF, как Ламберта, Орена Найара, Торренса Спарроу, зеркального отражения, зеркального пропускания и измеренного BRDF. Реализована поддержка нескольких техник трассировки лучей: трассировки Уайтеда и трассировки пути. Рассчитываются цвета с использованием спектральных данных и цветовое пространство CIE XYZ в сценах PBR для достижения высокой цветопередачи. TTFD также поддерживает вычисления индекса цветопередачи (CRI - Color Rendering Index). Этот показатель описывает способность источника света точно отражать все частоты его цветового спектра по сравнению с идеальным эталонным светом аналогичного типа. Структура и объем работы. Магистерский дипломный проект состоит из введения, четырех глав и выводов. Во введении представлена общая характеристика работы, произведена оценка современного состояния проблемы, обоснована актуальность направления исследований, сформулированы цели и задачи исследований, показано научную новизну полученных результатов и практическую ценность работы. В первом разделе рассмотрены принципы колориметрии и радиометрии. Они составляют основу некоторых основных ключевых особенностей TTFD. В частности, расчет цвета и методы освещения / затенения, реализованные в TTFD, используют понятие, представленные данном разделе. Во втором разделе рассмотрены трассировки лучей: фотореалистичный рендеринг (визуализация). Краткая классификация алгоритмов трассировки лучей. Решение уравнения рендеринга. В третьем разделе приведены особенности реализации разработанной системы. В четвертом разделе представлены подходы к тестированию системы в целом и отдельных модулей. В выводах представлены результаты проведенной работы. Работа представлена на 116 листах, содержит ссылки на список использованных литературных источников.

碩士
大葉大學
電機工程學系碩士在職專班
96
The dissertation will focus on the energy conservation sends the photo source at present the market condition to mix the white light LED technology inking that including Muliti-Chip LED Approach、the chromatic aberration compensation method, the color warm compensation method and so on because of the present high electrovalence and the environmental protection subject.There are some defects of white light LED that heat to drift and serious light fades, this paper will research four colors to mix light LED (R to be red) (the G green) (the B blue color) (the Y yellow) and to use RGBY LED to mix the white light LED test research light to fade the potency and the present market condition fluorescent lamp tube, Cold Cathode Fluorescent Lamp, the white light LED degree of illumination experiment. It is supposed to make the graph its result to study its province electricity potency and the light fades the degree.

碩士
華梵大學
機電工程學系博碩專班
97
In recent years, with the enhancement of material, process and technology, it greatly upgrades the luminous efficacy and power capacity, enables the possibility of having white light - emitting diodes replacing existing lighting sources. A fine quality in indoor lighting source requires conditions of high color rendering index, high luminous efficacy and low manufacturing cost. This research adopts blue light-emitting diodes with 6 lumens per watt in conjunction with market available phosphors with different wavelengths to analyze the synthesized frequency emitted after mixed with phosphors. And the absorptive quotient which the blue light should possesses and the emitted frequency functions for the phosphor will be used as basis to design each type of white light source with high color rendering index so as to promote and upgrade the luminous efficacy for light-emitting diode. From the design method of synthesized frequency for phosphor, the experimentation resulted with emitted color temperature of 3150 K of coloring rendering index of 96.51 and luminous efficacy of 28 lm/w; color temperature at 4700K with color rendering index of 95.5 and luminous efficacy of 30 lm/w; color temperature of 5200K with color rendering index of 94.21 and luminous efficacy of 30 lm/w for white light-emitting diode frequency range. In comparison to typical blue light-emitting diode covered with YAG phosphors, which would emit color temperature of 3800K with color rendering index of 62.6 and luminous efficacy of 44 lm/w, the above indicated that, the research findings point to the fact that, with slightly lowering of the luminous efficacy, it would have better performance in color rendering effect and it could generate the white light spectrum close to that of Planck’s and can readily replace the filament lamp lighting.

In this chapter, we review our recent work on blue laser diode-based visible light communication and solid-state lighting. Gallium nitride (GaN) phosphor-converted white light-emitting diodes (Pc-WLEDs) are emerging as an indispensable solid-state lighting (SSL) source for next-generation display system and the lighting industry. Together with the function of lighting, visible light communication (VLC) using Pc-WLEDs has gained increasing attention to fulfill the growing demand for wireless data communication. Practically, the low modulation response and low emitting intensity of light-emitting diodes (LED) are the drawbacks for the development of ultrahigh-speed VLC and high-quality SSL system. Blue GaN laser diode (LD) and remote phosphor-based white light can be used for both high-speed VLC and SSL simultaneously. We demonstrated a color-rendering index (CRI) of 93.8, a correlated color temperature (CCT) of 4435 K, and a data rate of 1.6 Gbps under NRZ-OOK modulation by an exciting blue laser diode on narrowband green−/red-emitting composite phosphor film. This work opens up exciting possibilities for future high-speed indoor VLC and high-quality SSL.

We proposed an all-inorganic multi-color converter based on Eu3+-doped phosphor-in-glass (PiG) for high-power white light-emitting diodes (WLEDs). The Eu3+-doped PiG was fabricated by screen-printing and low-temperature sintering a green phosphor into a Eu3+-doped glass matrix, which was prepared by a lead-free and low-melting glass frit doped with Eu3+ ions. When the Eu3+ doping content increases from 0.5 to 5 mol%, the transmittance of Eu3+-doped glass matrix is reduced while the red emission intensity is increased. In addition, with the green phosphor mass ratio of 30%, the Eu3+-doped PiG based WLEDs achieve a warm white light with a correlated color temperature (CCT) of 4496 K and a color rendering index (CRI) of 82 at the driving current of 350 mA. These results indicate that the Eu3+-doped PiG is a promising multi-color converter for high-power WLEDs.

White light-emitting diodes (WLEDs) composed of blue LED chip, yellow phosphor, and red quantum dots (QDs) are considered as a potential alternative for next-generation artificial light source with their high luminous efficiency (LE) and color-rendering index (CRI). While, QDs’ poor temperature stability and the incompatibility of QDs/silicone severely hinder the wide utilization of QDs-WLEDs. To relieve this, here we proposed a separated QSNs/phosphor structure, which composed of a QSNs-on-chip layer with a yellow phosphor layer above. A silica shell was coated onto the QDs surface to solve the compatibility problem between QDs and silicone. With CRI > 92 and R9 > 90, the newly proposed QDs@silica nanoparticles (QSNs) based WLEDs present 16.7 % higher LE and lower QDs working temperature over conventional mixed type WLEDs. The reduction of QDs’ temperature can reach 11.5 °C, 21.3 °C and 30.3 °C at driving current of 80 mA, 200 mA and 300 mA, respectively.

The use of solid-state lighting (SSL), such as light-emitting-diode (LED) products for general lighting and display applications, has increased dramatically over the past decade. However, there are significant photometric and radiometric metrological challenges with this new lighting technology. The photometric procedures and standards that have been developed for traditional lighting products, such as incandescent and compact fluorescent (CFL) lamps, do not work well for LEDs because they exhibit significantly different characteristics. This paper will discuss these differences in the spectral, geometric and operating properties of LEDs and how they impact precise photometric measurements and associated performance metrics, such as color rendering index (CRI). The current state-of-the-art uncertainties for photometric measurements of LED lighting products is about a factor of 5 poorer than for traditional lamps, based upon the results of recent interlaboratory comparisons involving both national measurement institutes (NMIs) and accredited laboratories. Reducing the uncertainty of these measurements will have a significant impact on society - both on reducing costs due to energy savings, but also on improving overall lighting quality and performance. For these reasons, there are a number of activities being carried out both at the national and international level to address these LED measurement issues. This paper will highlight the current strategies and standardization activities within both the Consultative Committee of Photometry and Radiometry (CCPR) and the International Commission of Illumination (CIE) to develop improved measurement techniques, transfer standards and metrics for the measurement and use of LED lighting in photometry and to meet consumer needs.