scholarly journals Luminous and Melanopic Efficiency Performance of Phosphor-Converted LEDs with Tunable Spectral Characteristics

2020 ◽  
Vol 10 (18) ◽  
pp. 6198
Author(s):  
Peiyu Wu ◽  
Jiaqi Ju ◽  
Qi Yao
Keyword(s):  
Intensity Distribution ◽  
Emission Intensity ◽  
Spectral Characteristics ◽  
Spectral Composition ◽  
Light Sources ◽  
Peak Wavelength ◽  
Efficiency Performance ◽  
Circadian Effect ◽  
Color Rendering ◽  
Blue Intensity

In this work, we investigated the luminous and melanopic efficiency of the radiation (LER/MER) performances of phosphor-converted LEDs (PC LEDs) with tunable spectral characteristics, namely peak wavelength, full width at half maximum (FWHM), and emission intensity. We constructed theoretical PC LED spectra based on the characteristics extracted from the database of IES TM-30-15, analyzed the relations between LER/MER and different spectral characteristics, and proposed spectral composition strategies at various correlated color temperatures (CCTs). Results showed that both MER and LER are linear with the FWHM of phosphor within the peak wavelength range in practical use, but the change in values by tuning emission intensity varies with spectral compositions. Hence, different spectral characteristics should be considered comprehensively. We further explored the trade-off between luminous and melanopic efficiency. Lowering the FWHM of phosphor and the intensity distribution of the blue LED can obtain higher LER and low circadian effect at lower CCT. As CCT increases, considering color rendering and the increase in the blue intensity distribution, besides reducing FWHM, tuning the peak wavelength close to the peak wavelength of V(λ) helps to reduce the circadian effect. These investigations provide optimization strategies for ideal melanopic and luminous performance of PC LED light sources.

scholarly journals Method for the numerical evaluation of the color rendering quality of matrix photodetectors

2021 ◽  
pp. 39-44
Author(s):  
Oleksandr Kupko ◽  
Olena Liashenko ◽  
Pavel Neyezhmakov ◽  
Yevhen Tymofeiev ◽  
Eduard Diumin ◽  
...  
Keyword(s):  
Color Image ◽  
Spectral Characteristics ◽  
Light Sources ◽  
Color Coordinates ◽  
Visual Impression ◽  
Digital Format ◽  
The Difference ◽  
Angular Coordinates ◽  
Color Rendering

To objectively evaluate the color image of an architectural object when changing its spectral quality and luminance in lighting, it is necessary to ensure its accurate fixation. The measurement of the color coordinates of an object provides the fully capture of its appearance, but this does not allow to get an adequate evaluation of the visual impression without visualizing the lighting scene. This requires a thorough procedure of reproducing the same color coordinates for each point of the image and the object with the same angular coordinates. In this work, an attempt is made to develop a numerical criterion for evaluating the quality of color rendering of the camera as a fixer of color visual impression of the selected scene. The development of a numerical detailed method for evaluation of the quality of color rendering of cameras will allow capturing more reliably such a subjective concept as the correspondence of the visual impression of the real scene and the image file of this scene. The digital format, which contains information about the object, avoids the problems associated with aging of the image. The proposed method of developing ways to numerically evaluate color distortion in photography is considered on the example of digital cameras Nikon D300s, Sony DSC-H5. The described approach for the case of known spectral characteristics allows to unambiguously link the calculated reaction of the camera with the chromaticity coordinates of spectrally pure colors. Modern methods of evaluating the quality of light sources (IES TM-30-15) allow evaluation of the direction of the shift. The proposed indicator – graph E (λi) numerically characterizes the difference between the reaction of the camera and the reaction of the human eye and does not give an idea in which direction there is a difference, conditionally red or blue image compared to the natural scene, but is the simplest and most understandable to the untrained user. It is shown that with an accuracy of measuring spectral characteristics of 1% for the considered example with Nikon D300s, this indicator at different wavelengths is calculated with an uncertainty of not more than 0.002.

DESIGN OF THE VIRTUAL DEVICE FOR THE SIGNAL SPECTRUM CALCULATION IN THE LABVIEW ENVIRONMENT

2019 ◽  
Author(s):  
Tossenko O.M.
Keyword(s):  
Virtual Instrument ◽  
Spectral Characteristics ◽  
Spectral Composition ◽  
Automated System ◽  
Signal Spectrum ◽  
Measuring Instruments ◽  
Specific Information ◽  
Measuring Device ◽  
Virtual Device ◽  
Graphical Tool

The development of measuring instruments requires a specialist to know the principles of operation of advanced measuring systems. This article describes guidelines for creating a virtual appliance in LabVIEW. LabVIEW (Laboratory Virtual Instrument Engineering Workbench) is a graphical application programming environment used as a standard tool for measuring, analyzing their data, further ma­ naging devices and objects under study. LabVIEW language is not like other programming languages. It does not create a program, but a virtual tool, designed not only for the simulation of certain processes, but also for the management of hardware and the study of real physical objects. The article deals with the task of designing application software for a specific information-measuring device, analyzes the capabilities of the LabVIEW environment for spectral analysis of various signals, outlines the basic principles and techniques of programming within the framework of the LabVIEW graphical environment during the basic stages of development. The procedure for creating a virtual device is described, which allows to evaluate the spectral composition of the signals, presents a graphical code of execution (diagram) to the program and a graphical tool interface of the virtual device. A number of basic elements used to develop the program are described. The simplicity of the graphic designs, the ease of installation on the field of the program, the clarity and readability of the program — all of which makes LabVIEW preferred over other languages of programming. In most cases, the experiment is the only source of reliable information. And the result is achieved much faster than the methods of "pure" theory. The article substantiates the effectiveness of using a development tool that allows to obtain a software product and ensure the fulfillment of all the basic functions of an automated system. Developing a software algorithm for calculating statistical parameters will help engineering students understand the order of determining spectral characteristics and their place in the structure of experimental research.

Four color stacked white organic light-emitting diodes utilizing the concept of triplet harvesting

2011 ◽  
Vol 1286 ◽  
Author(s):  
Th. C. Rosenow ◽  
S. Olthof ◽  
S. Reineke ◽  
B. Lüssem ◽  
K. Leo
Keyword(s):  
Light Emitting Diodes ◽  
Blue Emission ◽  
Organic Light Emitting Diodes ◽  
Light Sources ◽  
Emission Layer ◽  
Light Emitting ◽  
Organic Light ◽  
Blue Emitters ◽  
Color Rendering ◽  
Triplet Harvesting

ABSTRACTOrganic light-emitting diodes (OLEDs) are developing into a competitive alternative to conventional light sources. Nevertheless, OLEDs need further improvement in terms of efficiency and color rendering for lighting applications. Fluorescent blue emitters allow deep blue emission and high stability, while phosphorescent blue emitter still suffer from insufficient stability. The concept of triplet harvesting is the key for achieving internal quantum efficiencies up to 100 % and simultaneously benefiting from the advantages of fluorescent blue emitters. Here, we present a stacked OLED consisting of two units comprising four different emitters in total. The first unit takes advantage of the concept of triplet harvesting and combines the light emission of a fluorescent blue and a phosphorescent red emitter. The second unit emits light from a single emission layer consisting of a matrix doped with phosphorescent green and yellow emitters. With this approach, we reach white color coordinates close to the standard illuminant A and a color rendering index of above 75. The presented devices are characterized by high luminous efficacies of above 30 lm/W on standard glass substrates without outcoupling enhancement.

scholarly journals System efficiency of laser-based white light

2014 ◽  
Vol 3 (5-6) ◽  
Author(s):  
Roland Lachmayer ◽  
Alexander Wolf ◽  
Gerolf Kloppenburg
Keyword(s):  
Thermal Management ◽  
White Light ◽  
High Power ◽  
Laser Diodes ◽  
Light Sources ◽  
System Efficiency ◽  
Light Emitting ◽  
Scale Down ◽  
Color Rendering ◽  
Product Weight

AbstractFor many lighting applications, light-emitting diodes (LEDs) are replacing traditional light sources providing the possibility for smart and efficient systems as well as a reduction in the product weight. A next step in this development is the integration of laser-based light sources to increase luminance and to further scale down the optics possibly leading to a reduction of necessary resources. This article reviews the possibilities and challenges arising from the use of laser diodes especially compared to current high-power LED systems in terms of efficiency, color-rendering properties, and thermal management.

Modelling the effects of inter-observer variation on colour rendition

2017 ◽  
Vol 51 (1) ◽  
pp. 37-54 ◽  
Author(s):  
MJ Murdoch ◽  
MD Fairchild
Keyword(s):  
Colour Vision ◽  
Spectral Characteristics ◽  
Observer Variation ◽  
Light Sources ◽  
Standard Observer ◽  
Natural Range ◽  
Normal Colour ◽  
Range Of Variation

The colour rendition characteristics of light sources are quantified with measures based on CIE standard observers, which are reasonable representations of population averages. However, even among people with normal colour vision, the natural range of variation in colour sensitivity means any individual may see something different than the standard observer. Modelling results quantify the effects of these inter-observer differences on colour rendition measures defined by IES TM-30-15. In general, inter-observer differences tend to be smaller for light sources with high colour fidelity values, and they are affected by spectral characteristics of different lighting technologies. The magnitude of variation in colour rendition measures, up to 5–10 units in IES TM-30-15 ( Rf, Rg), measures is compared with other sources of variability and ambiguity.

scholarly journals Researching CdZnS/ZnS (GT) Quantum Dots in Cathodoluminescent Mode

2019 ◽  
Vol 8 (9S2) ◽  
pp. 841-843
Keyword(s):  
Quantum Dots ◽  
Research And Development ◽  
Uv Light ◽  
Spectral Characteristics ◽  
Light Sources ◽  
Application Field ◽  
Medium Pressure

Application field of UV light sources is getting larger at the last decades. Among the most widespread are high and medium pressure vacuum lamps. But there currently is a trend of moving away from using mercury both in household applications and manufacturing. This creates a necessity to conduct research and development for UV sources made and operating without Hg. Cathodoluminescent UV sources are in this category. One of the possible ways to create a viable UV anode phosphor is using quantum dots with needed spectral characteristics.

Evaluation methodology for light sources used to illuminate highly photosensitive artwork

2022 ◽  
pp. 147715352110515
Author(s):  
Z Li ◽  
F Zhang ◽  
X Song ◽  
R Dang
Keyword(s):  
Spectral Power ◽  
Spectral Composition ◽  
Primary Source ◽  
Evaluation Methodology ◽  
Spectral Energy ◽  
Light Sources ◽  
Damage Evaluation ◽  
Colour Difference ◽  
Lighting Intensity ◽  
Reflection Characteristics

Spectral energy radiated by light sources is the primary source of colour damage in highly photosensitive artworks (HPAs). However, spectral power distributions differ for different light sources, and the absorption and reflection characteristics of different materials, when irradiated by each narrow spectral energy band, also differ. This could result in large differences in the degree of radiation damage for materials under the same lighting intensity. In this paper, the suitability of different light sources used to illuminate HPAs was experimentally investigated over a long period of time by irradiating nine types of typical HPA materials with 10 different narrow-band light sources. By analysing the colour difference data of the illuminated material against the amount of exposure, a mathematical model relating the spectral composition and the damage to the colour of HPA materials was obtained. Based on this, a colour damage evaluation equation for light sources used for lighting HPAs was proposed. Finally, the equations were discussed using an example.

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