chromaticity coordinates
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2021 ◽  
Author(s):  
Yudie Huang ◽  
Fanzhou Lv ◽  
Jiaxu Chen ◽  
Shijia He ◽  
Zhihang Wang ◽  
...  

Abstract Structural color has been studied through various methods due to its distinguished features of stability, durability, high information storage density and high integration. However, the artificial structural color samples do not exhibit superior performance in color saturation and low angular dependence. Here, we present an approach to acquire additive reflective color based on a metal-dielectric-metal (MDM) stack. The upper layer composed of Ag particles is perforated in a hexagonal arrangement which profits from the dielectric anodic aluminum oxide (AAO) membrane, the size and shape of the Ag particles are getting inhomogeneous as the deposition thickness of the upper layer increasing, which expands the desired absorption range of surface plasmons. The residual non-anodized Al foil serves as a highly reflective substrate for efficient color presenting through the thin-film interference in this plasmonic MDM system. As a result, the color gamut area of this MDM stack is extended 8 times in CIE chromaticity coordinates. Finally, a wafer-scale (diameter of 83 mm) badge of Harbin Engineering University (HEU) with highly saturated colors and a pattern characterized with low angle-dependent property (up to 60°) are presented, which exhibit promising prospects in commercial coloring and imaging.


2021 ◽  
Author(s):  
Á. Urbin ◽  
B.V. Nagy

In our study chromatic discrimination thresholds of normal colour observers measured with the Trivector test of the Cambridge Colour Test were analysed. Chromaticity coordinates were transformed from the CIE (1976) u’v’ diagram to the CAM02-UCS and CAM16-UCS colour spaces, where colour differences were calculated. The measured data consisted of chromatic discrimination thresholds measured in 66 reference points covering the gamut of a CRT display. The test directions were set to the confusion axes towards the Protan, Deutan and Tritan confusion points. Our results show variance in the ΔE values expressed both in the CAM02-UCS and CAM16-UCS colour spaces. Since our input chromaticity values described previously measured just-noticeable stimuli – therefore perceptually equal colour differences – we assumed that our data show equal colour differences in the uniform colour spaces. However, the discrimination thresholds transformed to CAM02-UCS and CAM16-UCS show that colour differences increase towards the chromaticity of the adapting light.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Babak Zandi ◽  
Oliver Stefani ◽  
Alexander Herzog ◽  
Luc J. M. Schlangen ◽  
Quang Vinh Trinh ◽  
...  

AbstractSmart integrative lighting systems aim to support human health and wellbeing by capitalising on the light-induced effects on circadian rhythms, sleep, and cognitive functions, while optimising the light’s visual aspects like colour fidelity, visual comfort, visual preference, and visibility. Metameric spectral tuning could be an instrument to solve potential conflicts between the visual preferences of users with respect to illuminance and chromaticity and the circadian consequences of the light exposure, as metamers can selectively modulate melanopsin-based photoreception without affecting visual properties such as chromaticity or illuminance. This work uses a 6-, 8- and 11-channel LED luminaire with fixed illuminance of 250 lx to systematically investigate the metameric tuning range in melanopic equivalent daylight illuminance (EDI) and melanopic daylight efficacy ratio (melanopic DER) for 561 chromaticity coordinates as optimisation targets (2700 K to 7443 K ± Duv 0 to 0.048), while applying colour fidelity index Rf criteria from the TM-30-20 Annex E recommendations (i.e. Rf$$\ge$$ ≥ 85, Rf,h1$$\ge$$ ≥ 85). Our results reveal that the melanopic tuning range increases with rising CCT to a maximum tuning range in melanopic DER of 0.24 (CCT: 6702 K, Duv: 0.003), 0.29 (CCT: 7443 K, Duv: 0) and 0.30 (CCT: 6702, Duv: 0.006), depending on the luminaire’s channel number of 6, 8 or 11, respectively. This allows to vary the melanopic EDI from 212.5–227.5 lx up to 275–300 lx without changes in the photopic illuminance (250 lx) or chromaticity ($$\Delta u'v'$$ Δ u ′ v ′ $$\le$$ ≤ 0.0014). The highest metameric melanopic Michelson contrast for the 6-, 8- and 11-channel luminaire is 0.16, 0.18 and 0.18, which is accomplished at a CCT of 3017 K (Duv: − 0.018), 3456 K (Duv: 0.009) and 3456 K (Duv: 0.009), respectively. By optimising ~ 490,000 multi-channel LED spectra, we identified chromaticity regions in the CIExy colour space that are of particular interest to control the melanopic efficacy with metameric spectral tuning.


Electronics ◽  
2021 ◽  
Vol 10 (22) ◽  
pp. 2852
Author(s):  
Francisco Díaz-Barrancas ◽  
Halina Cwierz ◽  
Pedro J. Pardo

In virtual reality technology, it is necessary to develop improvements and apply new techniques that allow rapid progress and innovative development. Nowadays, virtual reality devices have not yet demonstrated the great potential they could develop in the future. One main reason for this is the lack of precision to represent three-dimensional scenarios with a similar solvency to what our visual system obtains from the real world. One of the main problems is the representation of images using the RGB color system. This digital colorimetry system has many limitations when it comes to representing faithful images. In this work we propose to develop a virtual reality environment incorporating hyperspectral textures into a virtual reality system. Based on these hyperspectral textures, the aim of our scientific contribution is to improve the fidelity of the chromatic representation, especially when the lighting conditions of the scenes and its precision are relevant. Therefore, we will present the steps followed to render three-dimensional objects with hyperspectral textures within a virtual reality scenario. Additionally, we will check the results obtained by applying such hyperspectral textures by calculating the chromaticity coordinates of known samples.


2021 ◽  
Vol 121 ◽  
pp. 111539 ◽  
Author(s):  
Mega Novita ◽  
Irna Farikhah ◽  
Rizky Muliani Dwi Ujianti ◽  
Dian Marlina ◽  
Benjamin Walker ◽  
...  

2021 ◽  
Vol 2067 (1) ◽  
pp. 012008
Author(s):  
A Kostyukov ◽  
A Nashivochnikov ◽  
M Rakhmanova ◽  
V Snytnikov

Abstract Al2O3:Eu3+ nanophosphors were prepared by laser vaporization method in a flowing mixture of Ar/He and O2. Luminescence properties of Al2O3:Eu3+ nanophosphors are predominantly determined by Eu3+ ions red emission with inhomogeneously broadened bands in the region of 550-750 nm corresponding to 5D0 →7FJ transitions of Eu3+ (J = 0 - 4). Hypersensitive electric dipole transition 5D0 →7F2 dominates in the spectrum and is responsible for the red emission. The effect of crystallite size on luminescence properties of Al2O3:Eu3+ nanocrystals was observed. It was shown that the introduction of oxygen during the synthesis improves the luminescence performance. The obtained chromaticity coordinates and high absolute QY (~ 14%) indicate the possibility of using red nanophosphors based on Al2O3:Eu3+.


Author(s):  
Howard James Swatland

Light may pass along and across the long axes of muscle fibers in any food myosystem. Thus, incident light may be scattered in several ways before some of it reappears at the surface as diffuse reflectance.  Pathways may be short if scattering is strong, or long if scattering is weak. Short pathways minimize selective absorbance by chromophores such as myoglobin, while long pathways maximize selective absorbance.  Many food myosystems exhibit a post-mortem decrease in pH caused by anaerobic glycolysis with a series of microstructural changes – glycogen granules between myofibrils are lost, myofibrils shrink laterally as myofilaments move closer together, water moves from within myofibrils to the space between them, muscle fiber membranes leak and lose their electrical capacitance, and myoglobin is flushed into the fluid filled spaces between muscle fibers. These changes increase scattering of light passing across the long axes of muscle fibers.  Scattering of light along muscle fibers is caused by sarcomere discs (A-bands).  Interference from one or a small number of sarcomere discs may cause iridescence, but in most cases interference from numerous discs causes achromatic diffuse reflectance. Commission International de l’Éclairage (CIE) chromaticity coordinates were calculated for various subsurface optical pathways. Pathways across versus along muscle fibers had a strong effect on CIE y (r = 0.84, P < 0.01) and an even stronger effect on CIE Y% (r = 0.95, P < 0.005).


2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Mingming Zhang ◽  
Lili Zhao ◽  
Jiahao Xie ◽  
Qian Zhang ◽  
Xiaoyu Wang ◽  
...  

AbstractLow-dimensional hybrid perovskites have demonstrated excellent performance as white-light emitters. The broadband white emission originates from self-trapped excitons (STEs). Since the mechanism of STEs formation in perovskites is still not clear, preparing new low-dimensional white perovskites relies mostly on screening lots of intercalated organic molecules rather than rational design. Here, we report an atom-substituting strategy to trigger STEs formation in layered perovskites. Halogen-substituted phenyl molecules are applied to synthesize perovskite crystals. The halogen-substituents will withdraw electrons from the branched chain (-R-NH3+) of the phenyl molecule. This will result in positive charge accumulation on -R-NH3+, and thus stronger Coulomb force of bond (-R-NH3+)-(PbBr42−), which facilitates excitons self-trapping. Our designed white perovskites exhibit photoluminescence quantum yield of 32%, color-rendering index of near 90 and chromaticity coordinates close to standard white-light. Our joint experiment-theory study provides insights into the STEs formation in perovskites and will benefit tailoring white perovskites with boosting performance.


Author(s):  
Vladimir Kozlov ◽  
◽  
Dilya Valiullina ◽  
Olga Kurakina ◽  
Erenkst Cadykov ◽  
...  

The service life of transformers and, as a consequence, of the electric power systems depends largely on the chemical composition and electrical insulating properties of the oil. In this regard, much attention is paid to the control of physical and chemical indicators and operational properties of transformer oils. The aim of this work is to determine the important diagnostic parameters such as the acid number and the tangent of the dielectric loss angle of the transformer oil based on the measured coordinates of the color of the transformer oil. This goal is achieved by the study of the coordinates of the transformer oils chromaticity. For this purpose, a white light source is used, which is a LED with a pumping line of 450 nm and a maximum radiation in the region of 550-560 nm, with radiation in the range from 400 to 800 nm. Sensors 1, 2, 3 allow determining the chromaticity coordinates of the measured source R, G, B (red, green, blue), due to several receivers having spectral characteristics of sensitivity in the corresponding region of the visible spectrum. The most significant result of the work was the establishment of correlations between the TM chromaticity coordinatesб their acid number and the tangent of the dielectric loss angle of TM. The significance of the results obtained was that the acid number and the tangent of the dielectric loss angle of the transformer oil could be determined by the chromaticity coordinates, and hence, by the color of the oil.


2021 ◽  
Author(s):  
Marwa Enneffati ◽  
Mohammed Rasheed ◽  
Narjes Aouani ◽  
Bassem Louati ◽  
Kamel Guidara ◽  
...  

Abstract Sm3+ activated NaCdVO4 phosphors were prepared by the simple solid-state reaction method. X-ray diffraction, dispersive energy (EDS), scanning electron microscope (SEM), infrared as well as photoluminescence (PL) techniques were used to characterize obtained samples. Irregular and non-uniform structures were observed by SEM. EDS spectra confirmed the presence of Na, Cd, V, O and Sm elements in each sample. Uuder 405nm excitation, the NaCd1 − xVO4: xSm (x = 0.01, 0.03 and 0.05) exhibits a bright red emission consisting mainly of four wavelength peaks at 556, 593, 650 and 700 nm. The highest emission intensity was found with a composition of x = 0.05. The analysis of PL spectra suggest that studied samples can be used as a red emitting phosphors candidates for fabrication of white LEDs. The CIE chromaticity coordinates of prepared samples were close to the blue-emitting phosphors for NaCdVO4 and red-emitting ones for NaCd0.99Sm0.01VO4, NaCd0.97Sm0.03VO4, and NaCd0.95Sm0.05VO4. The band gap energies of phosphors were calculated from reflectance data using K-M function.


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