Spectral Optimization of White LED Based on Mesopic Luminance and Color Gamut Volume for Dim Lighting Conditions (original) (raw)
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Color and light are inseparable entities that are the essential design factors in the field of interior architecture. When the light changes, the perceived color appearance of a surface within an interior environment also changes. The change in color perception is not only related to the type of a light source or the intensity of illumination, but also to the correlated color temperature (CCT) of a light source. The aim of this study is to understand how different CCTs of lightemitting diode (LED) lighting influence the color perception. A study is conducted to compare the perceptive color tendencies for inherent colors under two different CCTs of LED lighting, i.e. warm (2700º K) and cool (4000º K). In the study, Natural Color System (NCS) is utilized as a color notation system to reveal the possible tendencies and patterns concerning the relationship between the inherent and perceived colors. The general tendencies for the perceived colors revealed similar patterns in the nuance (i.e. blackness and chromaticness) color area for each inherent color and showed dispersion on the hue color area under the CCTs of both 2700º K and 4000º K LED lighting.
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Using the example of the UV-excited Ca9KMg(PO4)7:1% Eu2+ phosphor, methods for characterizing the color quality of the light emitted by it at different operating temperatures are described. The effect of adopting two different colorimetric observers established by the International Commission on Illumination (i.e., the CIE 1931 observer with a viewing angle of two degrees and the CIE 2015 observer with a viewing angle of ten degrees) on the position of the chromaticity point of light emitted by phosphor is discussed. It was demonstrated that using the CIE 2015 photometric observer to determine the position of the chromaticity point, the tested phosphor is characterized by smaller changes in the color of emitted light as a function of operating temperature than when using the CIE 1931 observer. Full Text: PDF ReferencesR. Pązik et al., "Thermal quenching mechanisms of the Eu3+ luminescence in Ca9Al(PO4)7 obtained by citric route", Materials Research Bulletin, Vol. 48, I.2, ...
Journal of Optics, 2019
The mesopic photometry system is expected to enable lighting designers to provide more visually effective lighting designs for appropriate outdoor lighting applications which are supposed to be more energy efficient compared to the photopic system. Studies on the adaptation characteristics are performed to define adaptation luminance and viewing conditions on the basis of peripheral adaptation state of observers for implementation of mesopic photometry system in outdoor lighting. In this work, experimentation is carried out to study the change in adaptation luminance due to various combinations of lamps with different spectral compositions and variable surrounding luminance effects caused by warm white and cool white light sources. The analysis of experimental results reveals that adaptation luminance can be considered instead of mesopic luminance for fixed area of measurement. Spectral composition of surrounding light sources imparts significant contribution on adaptation luminance. Cool white LED lamp shows most effective adaptation luminance under cool white surrounding lighting effect.