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Lamp Measurement and Characterization
Published in M. Nisa Khan, Understanding LED Illumination, 2013
These challenges are especially pronounced when LED lamps are compared to incandescent and fluorescent lamps, but are less crucial when incandescent lamps are compared to compact fluorescent lamps. This is true because typically, emitter shapes and spectral content of LEDs are very different compared to those from their incumbent counterparts. The different spectral content in different types of lamp sources, such as in LED and incandescent lamps, affects color rendering properties in ways that are not properly translated by the single CRI value defined in a traditional manner. Therefore, for the current general CRI definition to remain as an adequate comparison index is being challenged, and the topic of redefining CRI or broadening the description of comparative color quality is now of interest to some in the industry. At present, a debate is taking place to use a different metric, known as color quality scale (CQS), for describing color rendering properties of LED lamps [86].
Choosing Lamp Types & Sources
Published in Michael Stiller, Quality Lighting for High Performance Buildings, 2020
As described in Chapter 5, we measure the ability of electric lighting sources to accurately render the colors of objects by rating the source with a numerical scale called CRI (color rendering index). Sources are evaluated and assigned a CRI rating of 1–100. Daylight, incandescent, and halogen light sources are considered to have a CRI of 100. In fact, the CRI scale was not developed until after the advent of fluorescent and HID lighting created the need by introducing electric light sources that did a poor job of rendering colors. Though incandescent and halogen may be considered perfect, high color rendering can be achieved with fluorescent, metal halide, and LED sources. There is some controversy regarding the use of CRI as a reliable metric, especially for LEDs. A new metric, the Color Quality Scale, under development by researchers at the National Institute of Standards and Technology, is considered by some to be a better gauge, especially when evaluating LED lighting. But for the time being, the CRI scale is the tool available for evaluating light sources. Any good lamp or LED chip manufacturer will publish the CRI of their products, and in general lamps and sources with a CRI rating of at least 80 or 85 should be specified wherever accurate color rendering is important. LEDs tend to do a better job rendering saturated colors, even with lower CRI ratings, and so with LED fixtures we should review an actual sample and leave it to our eyes to judge whether it produces light of a high enough color quality for the application at hand. But for fluorescent and high intensity discharge lamps, we should always specify lamps with as high a CRI as we can, and limit our specifications to those that score no lower than 80 and preferably 85 and higher.
Red-emitting Ba2Si5N8Eu2+ conversion phosphor: A new selection for enhancing the optical performance of the in-cup packaging MCW-LEDs
Published in Cogent Engineering, 2018
Phu Tran Tin, Nguyen Huu Khanh Nhan, Tran Hoang Quang Minh, Nguyen Thi Phuong Thao
In this research, the red-emitting Ba2Si5N8Eu2+ phosphor is proposed to enhancing the optical performance of the 7,000 K and 7,700 K in-cup packaging MCW-LEDs. The optical performance of the MCW-LEDs is based on the primary factors like the color uniformity or the correlated color temperature deviation (D-CCT), the color rendering index (CRI), the color quality scale (CQS), and the luminous efficacy (lumen output). This paper is divided into three sections. The physical model of the 7,000 K, 7,700 K in-cup packaging MCW-LEDs and the optical properties of the red-emitting Ba2Si5N8Eu2+ conversion phosphor are presented Section 1. In Section 2, the mathematical optical description based on Mie theory of red-emitting Ba2Si5N8Eu2+ phosphor with Mat lab software and the simulation results with the commercial Light Tools software (Synopsys) is collected. Finally, the research results are intensely discussed, analyzed, and investigated in Section 3. Then, some conclusions are proposed. From the research results, we can conclude that the red-emitting Ba2Si5N8Eu2+ phosphor crucial influenced the optical performance of the 7,000 K and 7,700 K in-cup packaging MCW-LEDs. The red-emitting Ba2Si5N8Eu2+ phosphor could be considered as a prospective approach for MCW-LEDs improvement shortly.
Estimation of Light Source Color Rendition with Low-Cost Sensors Using Multilayer Perceptron and Extreme Learning Machine
Published in LEUKOS, 2021
J.-S. Botero, J. Valencia Aguirre, J.-F. Vargas Bonilla
Nowadays, there are several metrics that allow measuring the color rendering of artificial light sources, such as the color rendering index – CRI ( and ) (CIE 1995), the color quality scale – CQS (, , and ) (Davis and Ohno 2010) and the TM-30-18 ( and ) (IES 2015).
Prospects for 4-laser white-light sources
Published in Journal of Modern Optics, 2019
Snjezana Soltic, Andrew N. Chalmers
In order to remove some of the inconsistencies inherent in the CIE CRI method, and to update the methods of calculation, the NIST in 2010 proposed (3) their CQS (colour quality scale). The method is again based on the colour-shift principle – but now using 15 high-chroma test colour samples. There are several innovative refinements that aid in assessing colour quality, giving the general colour quality index Qa as output. An alternative calculation gives the colour fidelity index Qf which is intended to be an alternative to Ra.