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Organic–Inorganic Semiconductor Heterojunctions for Hybrid Light-Emitting Diodes
Published in Ye Zhou, Optoelectronic Organic–Inorganic Semiconductor Heterojunctions, 2021
Phosphors possess a broad emission band making them very suitable for white light generation and are very stable. They are made of an inorganic host doped with an optically active element. Common hosts are garnets, such as yttrium aluminium garnet (YAG), Y3Al5O12 [30,31]. The optically active element can be a rare earth element, rare earth oxide, or other rare earth compound. For white light generation cerium (Ce) is used, whereas neodymium (Ny) is utilized for lasers. By adding gadolinium (Gd) and/or gallium (Ga) to fabricate Ce-doped (Y1-xGdx)3(Al1-y Gay)5O15, the emission of the phosphor can be shifted [32]. This makes it possible to change and adapt the chromaticity of the white light when used together with a blue LED. For the fabrication of white LEDs, the YAG phosphor is incorporated in epoxy resin. The epoxy is then deposited on the blue LED die. The fraction of the absorbed blue light by the phosphor depends on the thickness of the epoxy-phosphor layer and its concentration, which also defines the yellow emission intensity of the phosphor.
Quality Criteria for Simulator Images: A Literature Review
Published in Florian Jentsch, Michael Curtis, Eduardo Salas, Simulation in Aviation Training, 2017
Pieter Padmos, Maarten V. Milders
Color perception has three attributes: hue, saturation, and brightness. Hue and saturation are referred to as chromatic color attributes (in everyday language the word color often refers only to chromatic attributes); brightness is the achromatic attribute of color. Psychophysically, a color stimulus is also specified in terms of three values: two chromaticity values (x,y coordinates) and luminance. Chromaticity corresponds to the perception of hue and saturation; luminance corresponds to brightness perception. See Walraven (1990) or Wyszecki and Stiles (1982) for more details. The application of chromatic images in simulators (as opposed to achromatic or monochromatic images) is useful for detecting and identifying objects and adds to realism.
Basic concepts in photometry, radiometry, and colorimetry
Published in John P. Dakin, Robert G. W. Brown, Handbook of Optoelectronics, 2017
The diagram using the chromaticity coordinates (x, y), as shown in Figure 8.12a, is referred to as the CIE 1931 chromaticity diagram, or the CIE(x, y) chromaticity diagram. The boundaries of this horseshoe-shaped diagram are the plots of monochromatic radiation (called the spectrum locus).
Improved Method for Evaluating and Specifying the Chromaticity of Light Sources
Published in LEUKOS, 2023
Michael Royer, Michael J. Murdoch, Kevin Smet, Lorne Whitehead, Aurélien David, Kevin Houser, Tony Esposito, Jason Livingston, Yoshi Ohno
One of the critical aspects of lighting design is specifying the chromaticity of a light source. Chromaticity assesses the color of light, separate from its luminance, and is used to predict if the tint of the light from two or more sources will be the same. The current standard practice for evaluating and specifying the chromaticity of light sources has not changed in almost 50 years, yet many people have become increasingly dissatisfied because it can lead to mismatches in perceived appearance between theoretically metameric light sources. Potential improvements for some elements of the chromaticity specification system have already been documented in scientific literature, but substantive uptake by producers and practitioners has not occurred. This article examines all stages of the chromaticity specification system, recommending a cohesive, updated method that could substantially improve chromaticity matching across light sources.
Tutorial: Background and Guidance for Using the ANSI/IES TM-30 Method for Evaluating Light Source Color Rendition
Published in LEUKOS, 2022
Chromaticity is a numerical specification of color, regardless of luminance (brightness), and is defined as part of the CIE system of colorimetry (CIE 2018; David et al. 2019b). Its primary use is to determine if the light from two or more sources match in appearance. When two spectra have the same chromaticity coordinates, are of equal luminance, and are viewed under identical conditions, their perceived color is predicted to match; however, chromaticity does not take into account the adaptive processes of the eye-brain system that make color vision non-linear and context-dependent. For example, the light emitted by an incandescent lamp can appear white when viewed alone, but yellowish when viewed simultaneously with midday daylight. Importantly, two light sources with the same chromaticity – which are called metamers – may have different spectral power distributions, and therefore render object colors differently.
A comparative study of carbon nanotube characteristics synthesized from various biomass precursors through hydrothermal techniques and their potential applications
Published in Chemical Engineering Communications, 2022
Mathangi J B, Helen Kalavathy M
The composition of any color can be demonstrated using the CIE 1931 chromaticity diagram in terms of three primary colors, such as blue, green, and red. Through adding three artificial colors called tri-stimulus values (X, Y, and Z), spectral color can be obtained (Equations (10)–(12)). The proportions of the emission light X, Y, and Z to the sum of the three values of tri-stimulus give the coordinates of chromaticity X, Y, and Z. The CIE XYZ color space has been deliberately designed to measure the luminance of color by the Y parameter. The chromaticity is then specified by the two derived parameters x and y, two of the three standardized values functioning with all three tristimulus values X, Y, and Z (Su et al. 2009). Color co-ordinates of chromaticity (X, Y, and Z) are typically determined using the following terms: