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Color Temperature (color + temperature)
Selected AbstractsPerformance of high-power III-nitride light emitting diodesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2008G. Chen Abstract The performance of III-nitride based high-power light emitting diodes (LEDs) is reviewed. Direct color high-power LEDs with 1 × 1 mm2 chip size in commercial LUXEON® Rebel packages are shown to exhibit external quantum efficiencies at a drive current of 350 mA ranging from ,60% at a peak wavelength of ,420 nm to ,27% at ,525 nm. The short wavelength blue LED emits ,615 mW at 350 mA and >2 W at 1.5 A. The green LED emits ,110 lm at 350 mA and ,270 lm at 1.5 A. Phosphor-conversion white LEDs (1 × 1 mm2 chip size) are demonstrated that emit ,126 lm of white light when driven at 350 mA and 381 lm when driven at 1.5 A (Correlated Color Temperature, CCT , 4700 K). In a similar LED that employs a double heterostructure (DH) insign instead of a multi-quantum well (MQW) active region, the luminous flux increases to 435 lm (CCT , 5000 K) at 1.5 A drive current. Also discussed are experimental techniques that enable the separation of internal quantum efficiency and extraction efficiency. One technique derives the internal quantum efficiency from temperature and excitation-dependent photoluminescence measurements. A second technique relies on variable-temperature electroluminescence measurements and enables the estimation of the extraction efficiency. Both techniques are shown to yield consistent results and indicate that the internal quantum efficiency of short wavelength blue (, , 420 nm) high-power LEDs is as high as 71% even at a drive current of 350 mA. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The Effects of Lighting on Consumers' Emotions and Behavioral Intentions in a Retail Environment: A Cross-Cultural ComparisonJOURNAL OF INTERIOR DESIGN, Issue 1 2007Nam-Kyu Park Ph.D. ABSTRACT As an important component of a retail store's atmospherics, lighting can affect the emotional responses that influence consumer shopping behavior. The purpose of this study is to examine, through cross-cultural comparison, the effect of the color quality of light in a retail environment on consumers' emotional states, behavioral intentions, and perceptions. The experimental research followed a 2 times 2 × 2 factorial design with repeated measures to identify the impact of culture group, color rendering index, and color temperature. The results of this study indicate that consumers are aroused and pleased by certain lighting effects and that cultural differences influence perceptions as well as the behavioral intentions of "approach-avoid" in a retail environment. Practical implications of this study could include application of store lighting techniques that enhance visual perceptions of consumers, induce emotional states of arousal and pleasure, and appeal to consumers from different cultures. [source] Optical Properties of Co3O4 -Doped ZnO,B2O3,SiO2,Al2O3 Glass System for a Transparent Dielectric LayerJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2009Byung-Hwa Seo There has been a need to improve color temperature without using asymmetric cell structures using transparent dielectric layers with variation of Co3O4 contents in plasma display panel (PDP). In this study, ZnO,B2O3,SiO2,Al2O3 glasses with variations of the Co3O4 content (0, 0.5, 1.0, 1.5, and 2.0 wt%) were fabricated and the optical properties of these glasses were characterized. As the content of Co3O4 increased, the transmittance of the red region (from 580 to 780 nm) decreased more than of the blue region (from 380 to 500 nm). This change of transmittance induced the transition of the coordination of the color temperature toward the blue region. Therefore, the addition of 2 wt% Co3O4 can improve the color temperature from 6087 to 7378 K and the result was confirmed using simulation. [source] Color constancy from invariant wavelength ratios: I. The empirical spectral mechanismCOLOR RESEARCH & APPLICATION, Issue 3 2008Ralph W. PridmoreArticle first published online: 10 APR 200 Abstract The wavelengths of several constant hues over four illuminants (D95, D65, D50, A) are derived from several sets of published data. In the plane of wavelength and reciprocal illuminant color temperature (MK,1), the wavelengths of constant hues plot straight approximately parallel lines whose mean slope is about 87°. Parallel lines give invariant wavelength ratios, hence constant hues in this plane are near-invariant wavelength ratios across illuminants. As recently demonstrated, the complementary wavelengths to a constant hue (across illuminants) represent the complementary constant hue; these complementary wavelengths also plot a near-parallel line to the first constant hue. To confirm and further define the constant slope of these lines, it is shown that complementary wavelength pairs, per CIE data, can only plot parallel straight lines at the angle of 87° ± 1. In summary, near-parallel sloping lines represent constant hues at near-invariant wavelength ratios. This mechanism of color constancy is shown to relate to the well-known theory of relational color constancy from invariant cone-excitation ratios. In the visual process, the latter ratios are presumably the source of the former (invariant wavelength ratios). © 2008 Wiley Periodicals, Inc. Col Res Appl, 33, 238,249, 2008 [source] Whiteness perception under different types of fluorescent lampsCOLOR RESEARCH & APPLICATION, Issue 2 2003Miyoshi Ayama Abstract The effects of correlated color temperature and the chromaticity of light sources on the perception of surface whiteness were investigated. For the experiment, a Munsell N9.25 chip and 11 nearly white chips (V = 9.25, Munsell chroma , 1.0) were selected. The interval scale of the whiteness of these chips was determined from the results of pair comparisons under eight different fluorescent lamps with correlated color temperatures from 2800 to 6700 K. The Munsell 3PB, 10PB, 7P, and N chips gained high scores under 6700 K illumination, whereas the 3PB, 5B, 7BG, and 9G chips scored higher under the 2800 K illumination. The 12 chips were divided into two groups. In one group, the interval scale from the bottom was found to increase as the correlated color temperature increased, whereas in the other group, it decreased with the temperature. The Munsell 3PB/9.25/1.0 chips fell into the latter group but consistently exhibited the highest or at least high-order scores for all the illuminations examined. In those cases in which the correlated color temperature was held constant, the chromaticity of the light source was found to have no significant effect on the whiteness interval scale. A high correlation was identified between the interval scale of the whiteness and the two metrics, the metric chroma of CIELAB, and CIECAM97s chroma C. © 2003 Wiley Periodicals, Inc. Col Res Appl, 28, 96,102, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.10129 [source] Retail Store Lighting for Elderly Consumers: An Experimental ApproachFAMILY & CONSUMER SCIENCES RESEARCH JOURNAL, Issue 4 2007Nam-Kyu Park The study presents an investigation of the influence of the color of light on readability by figure to background value contrast, color perception, and overall room-light estimation for elderly consumers in an experimental setting representing a retail store. A factorial design with repeated measures was used to identify the impact of three independent variables: (a) lamp color temperatures, (b) lamp color-rendering properties, and (c) age of the participants. The results show that older adults perceived the higher color temperature light source as less cool than did younger adults. Older adults rated their level of comfort and preference higher than the younger participants under all lighting conditions. Regarding readability, higher color-rendering light sources provide better readability, and older adults have more difficulty with warmer lighting when value contrasts were reduced. Implications from this study can be applied to retail lighting techniques to attract elderly consumers. [source] Cover Picture: Multilayer Polymer Light-Emitting Diodes: White-Light Emission with High Efficiency (Adv. Mater.ADVANCED MATERIALS, Issue 17 200517/2005) Abstract White-light-emitting polymer diodes can be fabricated by solution processing using a blend of luminescent semiconducting polymers and organometallic complexes as the emission layer, and water-soluble (or ethanol-soluble) polymers and/or small molecules as the hole-injection/transport layer (HIL/HTL) and the electron injection/transport layer (EIL/ETL), as reported on p.,2053 by Gong, Bazan, Heeger and co-workers. Illumination-quality light is obtained from these multilayer, high-performance devices, with stable CIE coordinates, color temperatures, and high color-rendering indices all close to those of "pure" white light. The cover illustration envisages the incorporation of the fabrication technique with low-cost manufacturing technology in order to produce large areas of high-quality white light. [source] Cultural Preferences in Hotel Guestroom Lighting DesignJOURNAL OF INTERIOR DESIGN, Issue 1 2010Nam-Kyu Park Ph.D. This study examined North American and South Korean preferences for different lighting conditions in a hotel guestroom. A sample of 87 North Americans and 88 Koreans (N = 175) rated their preference for different intensities and color temperatures of light within a digitally generated hotel guestroom design. A mixed between-within analysis of variance (Kuehl, 1999) evaluated three dependent variables (preference, arousal, and pleasure) against three independent variables (two culture groups × two light colors × two light intensities). Findings indicated that North American subjects preferred the hotel guestroom with low intensity and warm color lighting the most, whereas the Korean group preferred high intensity and warm color lighting the most. North American participants also perceived dim lighting as more arousing than bright lighting, whereas Korean participants perceived bright lighting as more arousing than dim lighting. Overall, the findings suggest that design criteria for hotel guestroom lighting should be revised to account for distinct cultural differences. [source] Whiteness perception under different types of fluorescent lampsCOLOR RESEARCH & APPLICATION, Issue 2 2003Miyoshi Ayama Abstract The effects of correlated color temperature and the chromaticity of light sources on the perception of surface whiteness were investigated. For the experiment, a Munsell N9.25 chip and 11 nearly white chips (V = 9.25, Munsell chroma , 1.0) were selected. The interval scale of the whiteness of these chips was determined from the results of pair comparisons under eight different fluorescent lamps with correlated color temperatures from 2800 to 6700 K. The Munsell 3PB, 10PB, 7P, and N chips gained high scores under 6700 K illumination, whereas the 3PB, 5B, 7BG, and 9G chips scored higher under the 2800 K illumination. The 12 chips were divided into two groups. In one group, the interval scale from the bottom was found to increase as the correlated color temperature increased, whereas in the other group, it decreased with the temperature. The Munsell 3PB/9.25/1.0 chips fell into the latter group but consistently exhibited the highest or at least high-order scores for all the illuminations examined. In those cases in which the correlated color temperature was held constant, the chromaticity of the light source was found to have no significant effect on the whiteness interval scale. A high correlation was identified between the interval scale of the whiteness and the two metrics, the metric chroma of CIELAB, and CIECAM97s chroma C. © 2003 Wiley Periodicals, Inc. Col Res Appl, 28, 96,102, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.10129 [source] | ||||||||||