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Environmental Ergonomics
Published in Robert W. Proctor, Van Zandt Trisha, Human Factors in Simple and Complex Systems, 2018
Robert W. Proctor, Van Zandt Trisha
The last kind of lighting we will discuss is called solid-state lighting, and it uses arrays of light emitting diodes (LEDs). LED bulbs can fit into the sockets of light fixtures manufactured for incandescent bulbs. LEDs are particularly useful for applications where small size and long lifetimes are important, such as for color indicator lamps. For example, they are now widely used for traffic lights, toll booth lane indicators, light rail signals, vehicle tail lights, and airport runway lighting (Boyce, 2014). While high-brightness LEDs can be used for a variety of lighting applications, they have a number of drawbacks (Žukauskas et al., 2002). In addition to the fact that they can be very expensive, like fluorescent bulbs, color rendering can be poor, and there is some evidence that blue and cool-white LEDs can cause glare, damage the retina, and interfere with normal sleep cycles (Algvere, Marshall, & Seregard, 2006; American Medical Association, 2016).
Visible Light Communications
Published in Z. Ghassemlooy, W. Popoola, S. Rajbhandari, ®, 2017
Z. Ghassemlooy, W. Popoola, S. Rajbhandari
Solid-state lighting refers to the fact that light is generated through solid-state electroluminescence. It has a relatively short history. In the 1990s, we saw the introduction of high-brightness LEDs for the purpose of general illumination. Within only a few years, LED’s luminous efficacy has improved rapidly from less than 0.1 lm/W to over 230 lm/W and with a lifetime as high as 100,000 h [1–3]. We are now seeing the introduction of another upcoming type of solid-state lighting source, known as the organic LED (OLED). OLED has relatively low luminous efficacy (measured value of 100 lm/W [4] and short lifetime compared with the LEDs, thus limiting their application for various colour displays and general illumination for the time being. Nevertheless, OLEDs may also be used as an alternative solution for large area lighting and communications.
Evaluating Lighting Equipment
Published in Craig DiLouie, Lighting Redesign for Existing Buildings, 2020
First, LEDs produce light using a non-traditional method. With conventional sources, electric energy is converted to light by heating a filament (incandescence) or passing current to excite a gas (fluorescence and high intensity discharge). With LEDs, current is passed through crystalline solids (which makes LEDs a “solid state” light source and explains why it is more formally called “solid state lighting”) to produce visible light. This construction yields products that are far more robust, impervious to vibration and immune to extreme cold, with no mercury.
Temporal Luminescence of Broadband Light-Emitting Diodes and Their Use for Generating Customizable White Light
Published in LEUKOS, 2020
Faiz Rahman, Anthony F. George
Solid-state lighting, based on light-emitting diodes (LEDs), is now widespread in all kinds of lighting applications (Rahman 2013a; Schubert et al. 2006; Zukaukas et al. 2002). With the maturity of this relatively recent lighting technology, the focus is shifting toward improving the quality of light produced from both single white LEDs and combinations of color LEDs. This mainly involves exercising control over the exact shade (chromaticity) of white light produced from LED-based sources.
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
Light-emitting diodes (LEDs) are the modest type of solid-state lighting, which have the most significant advancement in the lighting industry in the last few decades. Phosphor-converted LEDs (pcLED), which combine a blue LED chip, and the yellow emitting phosphor is the most common approach to accomplish white light emission through LEDs packaging (“Design of LED,” 2011; Gibney, 2014; Hu, Luo, & Liu, 2011; Luo, Hu, Liu, & Wang, 2016; Winkler, Trinh, Bodrogi, & Khanh, 2015). In the last few decades, there so many research focuses on improving the optical performance of the pcLED in packaging direction. Thickness and concentration of phosphor are considered as the main factors in the white LEDs packaging because the luminous flux and color of LEDs are adjusted mainly through changing the phosphor thickness and concentration after the phosphor converters are chosen. Shuai, He, Tran, and Shi (2011) and Tran and Shi (2008) experimentally studied the effects of phosphor thickness and concentration on LEDs luminous flux and correlated color temperature. From the results, higher luminous efficacy are taken with the lower phosphor concentration and higher phosphor thickness (lower trapping efficiency and fewer backs scattering of light). Sommer et al. firstly studied the effects of phosphor thickness, concentration, and size on the spatial color distribution of white LEDs (Sommer et al., 2008). The spatial color uniformity of white LEDs could be improved by changing the phosphor concentration or thickness. An increase of the phosphor thickness or concentration can alter the color from bluish to yellowish, and the growth in the central zone is faster than that in the border area. In Li et al. (2012) and Liu, Liu, Wang, and Luo (2008a, 2008b, 2008c), the effect of phosphor location on the spatial color distribution was investigated. The results showed that to obtain high color uniformity packaging elements should make the blue light and yellow light have a similar radiation pattern. In the last year, some researchers were concentrated on enhancing the optical performance of multi-chip white LEDs (MCW-LEDs) by adding green or red phosphor into the phosphor compounding (Anh, Quoc, & Lee, 2016; Minh, Quang, Nhan, Anh, & Lee, 2017). It can be found that the optical properties of MCW-LEDs can be enhanced clearly. From this point of view, improving the optical performance of MCW-LEDs by adding diffusers into the phosphor compounding is still needed to be investigated. In this research, we try to fill the remaining gap.