Статті в журналах: "COLOR RENDERING INDEX (CRI)"

1

Nazarenko, L. A., O. M. Didenko, and D. O. Usichenko. "New Color Rendering Metrics." Metrology and instruments, no. 1 (March 2, 2020): 37–44. http://dx.doi.org/10.33955/2307-2180(1)2020.37-44.

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Color is not a physical properly of object, but rather a human perception enabled by light. Nevertheless the color of light sources is described by the industry primarily in terms of two metrics, correlated color temperature (CCT) and color rendering index (CRI), that are only indirectly related to human perception. CCT is intended to characterize the appearance of the illumination generated by source, and CRI is intended to characterize the appearance of objects illuminated be the source. There two color metrics developed nearly of half-century ago, are increasingly being challenged because new source are being developed with increasingly exotic spectral power distribution. The new color metric applicable to the color appearance of the light emitted by at light source and quantified by the CCT and D. The chromaticity is one of the critical parameters for light sources for general lighting and normally specified with chromaticity coordinates CIE (x, y) or (', '). However these two numbers do not provide the color information intuitively. For practical purposes, collated color temperature (CCT) is commonly used to provide the chromaticity information of general illumination source CCT, however, provides only one dimension of the chromaticity and there is another dimension, which is the position of chromaticity with respect to Plancian locus. For this purpose «D» or similar terms as distance from Plancian locus have been need used in some part at the industry but these had not beer officially defined is any standard. Color rendering is general term for describing the ability of a light source to provide color information to human observer when objects are illuminated by that source like CCT color rendering index (CRI), the most accepted measure of color rendering. CRI was developed, through the system of colorimetry, simply to be an indication of how «natural» or «undistorted» the light source makes the color of objects appear when illuminated by the source when used as the sole measure of color rendering for a light source, CRI simply cannot meet expectations. With the advent of SSL, these limitations have become more widely recognized. It was proposed a two-metric system combining CRI, a measure of color consistency with respect to a reference source, with gamut area index (GAI), a measure of color saturation. When used to gather, the two metrics appear to optimize the color appearance of natural objects like fruits and vegetable enhancing their vividness with making them appear unnatural. CCT is shown in commercial instruments but D is often available. D needs to be calculated using the method of triangular solution: Create a table CCT is distance di to Plancian locus on () coordinate; Find the closest point in the table; Solve the triangle for the neighboring 2 points. Gamut area of light source is commonly calculated as the area of the polygon defined by the chromaticities in CIE 1977 (', ') color space of the light CIE TCSs. Gamut area of EES is sealed to 100 and defined as gamut area index. The gamut area of any other light source is scaled accondingle.

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2

Zhang, Minhao, Yu Chen, and Guoxing He. "Color Temperature Tunable White-Light LED Cluster with Extrahigh Color Rendering Index." Scientific World Journal 2014 (2014): 1–6. http://dx.doi.org/10.1155/2014/897960.

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The correlated color temperature (CCT) tunable white-light LED cluster with extrahigh color rendering property has been found by simulation and fabricated, which consists of three WW LEDs (CCT = 3183 K), one red LED (634.1 nm), one green LED (513.9 nm), and one blue LED (456.2 nm). The experimental results show that this cluster can realize the CCT tunable white-lights with a color rendering index (CRI) above 93, special CRI R9 for strong red above 90, average value of the special CRIs of R9 to R12 for the four saturated colors (red, yellow, green, and blue) above 83, and luminous efficacies above 70 lm/W at CCTs of 2719 K to 6497 K.

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3

Li, Cheng, M. Ronnier Luo, Changjun Li, and Guihua Cui. "The CRI-CAM02UCS colour rendering index." Color Research & Application 37, no. 3 (July 15, 2011): 160–67. http://dx.doi.org/10.1002/col.20682.

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4

Tsai, Chun-Chin. "Color Rendering Index Thermal Stability Improvement of Glass-Based Phosphor-Converted White Light-Emitting Diodes for Solid-State Lighting." International Journal of Photoenergy 2014 (2014): 1–6. http://dx.doi.org/10.1155/2014/407239.

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High color rendering index performance has been required for phosphor-converted warm-white light-emitting diodes (PC-WWLEDs) in lighting industry. The characteristics of low-temperature fabricated phosphor (yellow: Ce3+:YAG, green: Tb3+:YAG, and red: CaAlClSiN3:Eu2+) doped glass were presented for applications to high color rendering index warm-white-light-emitting diodes. Color coordinates (x, y) = (0.36, 0.29), quantum yield (QY) = 55.6%, color rending index (CRI) = 85.3, and correlated color temperature (CCT) = 3923 K were characterized. Glass-based PC-WWLEDs was found able to maintain good thermal stability for long-time high-temperature operation. QY decay, CRI remenance, and chromaticity shift were also analyzed for glass- and silicone-based high-power PC-WLEDs by thermal aging at 150°C and 250°C for industrial test standard’s aging time 1008 hours. Better than the silicone’s, thermal stability of glass-based PC-WLEDs has been improved. The resulted high color rendering index (CRI) glass phosphor potentially can be used as a phosphor layer for high-performance and low-cost PC-WLEDs used in next-generation indoor solid-state lighting applications.

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5

Yadav, Amit, Ilya Titkov, Alexei Sakharov, Wsevolod Lundin, Andrey Nikolaev, Grigorii Sokolovskii, Andrey Tsatsulnikov, and Edik Rafailov. "Di-Chromatic InGaN Based Color Tuneable Monolithic LED with High Color Rendering Index." Applied Sciences 8, no. 7 (July 17, 2018): 1158. http://dx.doi.org/10.3390/app8071158.

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We demonstrate a phosphor free, dichromatic GaN-based monolithic white LED with vertically stacked green and blue emitting multiple quantum wells. The optimal thickness of GaN barrier layer between green and blue quantum wells used is 8 nm. This device can be tuned over a wide range of correlated color temperature (CCT) to achieve warm white (CCT = 3600 K) to cool white (CCT = 13,000 K) emission by current modulation from 2.3 A/cm2 to 12.9 A/cm2. It is also demonstrated for the first time that a color rendering index (CRI) as high as 67 can be achieved with such a dichromatic source. The observed CCT and CRI tunability is associated with the spectral power evolution due to the pumping-induced carrier redistribution.

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6

Jiang, Huan, Min Huang, Fu Song Yang, and Yu Liu. "Evaluation of Color Rendering Index for LED and Fluorescent Light Sources." Applied Mechanics and Materials 731 (January 2015): 22–26. http://dx.doi.org/10.4028/www.scientific.net/amm.731.22.

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In order to assess the performances of different color rendering index (Ra, CRI, CQS, nCRI, R96a). The LED (light-emitting diode), fluorescent light sources and 30 printed color samples were used in our experiment. 20 observers were organized to carry out the color preference experiment, the visual data were accumulated to test the performances of the light sources and the results indicated that existing color rendering index have some deficiencies to assess the quality of the light source, which were needed to be modified for the theory of color science and industry application. The new CQS additional scales were calculated and the improvements were still insufficient for the LED light sources.

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7

Yu, Wenjuan, Xu Jia, Mengnan Yao, Linghui Zhu, Yongbing Long, and Liang Shen. "Semitransparent polymer solar cells with simultaneously improved efficiency and color rendering index." Physical Chemistry Chemical Physics 17, no. 37 (2015): 23732–40. http://dx.doi.org/10.1039/c5cp03467a.

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8

Liu, Xin, Yunsen Zhao, Jiangsheng Yu, and Rihong Zhu. "High-performance bifacial semitransparent organic photovoltaics featuring a decently transparent TeO₂/Ag electrode." Materials Chemistry Frontiers 5, no. 23 (2021): 8197–205. http://dx.doi.org/10.1039/d1qm01142a.

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The TeO2 layer endowed bifacial semitransparent organic photovoltaics (ST-OPVs) with improved values of average visible transmittance (AVT), light utilization efficiency (LUE), bifaciality factor (BF) and color-rendering index (CRI).

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9

Liu, Xin, Yunsen Zhao, Jiangsheng Yu, and Rihong Zhu. "High-performance bifacial semitransparent organic photovoltaics featuring a decently transparent TeO₂/Ag electrode." Materials Chemistry Frontiers 5, no. 23 (2021): 8197–205. http://dx.doi.org/10.1039/d1qm01142a.

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The TeO2 layer endowed bifacial semitransparent organic photovoltaics (ST-OPVs) with improved values of average visible transmittance (AVT), light utilization efficiency (LUE), bifaciality factor (BF) and color-rendering index (CRI).

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10

Miao, Yanqin, Kexiang Wang, Bo Zhao, Long Gao, Jiacong Xu, Hua Wang, and Bingshe Xu. "Ultra-simple white organic light-emitting diodes employing only two complementary colors with color-rendering index beyond 90." RSC Adv. 7, no. 78 (2017): 49769–76. http://dx.doi.org/10.1039/c7ra10205d.

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This ultra-simple di-chromatic WOLED, using only three organic materials, achieves an ultra-high CRI of 90, which is even comparable with other reported three-color, four-color, and five-color WOLEDs.

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11

Lee, Sujung, and Heakyung C. Yoon. "A Randomized Controlled Trail for Comparing LED Color Temperature and Color Rendering Attributes in Different Illuminance Environments for Human-Centric Office Lighting." Applied Sciences 11, no. 18 (September 8, 2021): 8313. http://dx.doi.org/10.3390/app11188313.

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In this study, two experiments were conducted to investigate the effects of the color rendering index (CRI) and correlated color temperature (CCT) of light-emitting diode (LED) lighting on office user acceptance and to explore the proper color attributes for human-centric office lighting. Experiment 1 had four LED lights, with two levels for the CRI (CRI < 80: 79, 76; or CRI ≥ 80: 83, 84) and CCT (3000 K or 6500 K) at 300 lux. In experiment 2, there were four LED lights, with several levels for the CRI (CRI < 80: 78; or CRI ≥ 80: 87, 83) and CCT (3000 K or 6500 K) at 500 lux. Ninety-six participants in experiment 1 and ninety-four participants in experiment 2 performed a reading task. The results in experiment 1 and experiment 2 showed that LEDs with lower CRI values at warm color temperatures were rated as more acceptable than LEDs with higher CRI values at warm color temperatures. However, the positive effect extended to LEDs with higher CRI values at cool temperatures but not to LEDs with lower CRI values at cool temperatures. Therefore, the findings are that LEDs with lower CRI values at warm color temperatures and LEDs with higher CRI values at cool temperatures provide the right level of color attributes for office lighting.

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12

Chung, Shu-Ru, Sheng-Shiun Chen, Kuan-Wen Wang, and Cyuan-Bin Siao. "Promotion of solid-state lighting for ZnCdSe quantum dot modified-YAG-based white light-emitting diodes." RSC Advances 6, no. 57 (2016): 51989–96. http://dx.doi.org/10.1039/c6ra10673k.

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In this study, the effect of quantum dot (QD) addition and photoluminescence quantum yield (PL QY) of QDs on the luminous efficacy and color rendering index (CRI) of white light-emitting diodes (LEDs) has been investigated.

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13

Zhuang, Xuming, Helei Wang, Daren Xu, Yu Liu, and Yue Wang. "High-quality warm white organic electroluminescence from efficient phosphor-only emitting systems based on bipolar iridium(iii) complexes." Journal of Materials Chemistry C 8, no. 47 (2020): 16730–35. http://dx.doi.org/10.1039/d0tc04934d.

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Warm white organic light-emitting diodes (WOLEDs) based on efficient phosphor-only emitting systems exhibit very high peak electroluminescence (EL) efficiencies of 25.0/22.5% and 71.3/59.3 lm W⁻¹ and desirable color rendering index (CRI) of 81/90.

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14

Wang, Guan-E., Gang Xu, Ming-Sheng Wang, Li-Zhen Cai, Wen-Hua Li, and Guo-Cong Guo. "Semiconductive 3-D haloplumbate framework hybrids with high color rendering index white-light emission." Chemical Science 6, no. 12 (2015): 7222–26. http://dx.doi.org/10.1039/c5sc02501j.

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15

Piccolo, Antonio, Mauro Prestipino, Maria Francesca Panzera, and Roberto Baccoli. "Study of the Correlation among Luminous Properties of Smart Glazing for Adaptive Energy Saving Buildings." Buildings 13, no. 2 (January 24, 2023): 337. http://dx.doi.org/10.3390/buildings13020337.

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A smart window, such as electrochromic or thermochromic windows, may not be able to accomplish at the same time energy efficiency and visual comfort functions, since satisfying one criterium interferes with the other. This recalls to the important issue of establishing precise relationships among parameters affecting energy, glare control, and color rendering tasks and the influence on them of glazing material composition and preparation technique. With this aim, the luminous properties of a number of advanced glazings found in literature and of three home-made electrochromic devices differing by material composition and/or preparation technique are analyzed in this study. The investigation has involved the determination of the CIE (Commission International de l’Eclairage) Color Rendering Index (CIE CRI), the Correlated Color Temperature (CCT), and the luminous transmittance coefficient (τV) of the devices which are discussed with regard to their potential in absolving to energy and visual comfort tasks. Results lead to the main conclusion that the CIE CRI, CCT, and τV indexes are clearly linked by an exponential correlation. At low τV values (τV< 0.5), however, the correlation weakens and the variation of the CIE CRI and CCT indexes becomes entirely material dependent. The influence of preparation technique appears to be irrelevant since the color rendering indexes appear to be well correlated to τV over all the investigated τV range.

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16

Khan, Asma, Aurang Zeb, Lina Li, Weichuan Zhang, Zhihua Sun, Yuyin Wang, and Junhua Luo. "A lead-free semiconducting hybrid with ultra-high color rendering index white-light emission." Journal of Materials Chemistry C 6, no. 11 (2018): 2801–5. http://dx.doi.org/10.1039/c7tc05384c.

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17

Moraitis, Panagiotis, Gijs Leeuwen, and Wilfried Sark. "Visual Appearance of Nanocrystal-Based Luminescent Solar Concentrators." Materials 12, no. 6 (March 16, 2019): 885. http://dx.doi.org/10.3390/ma12060885.

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The luminescent solar concentrator (LSC) is a promising concept for the integration of photovoltaic (PV) generators into the building envelope. Having the form of semitransparent plates, LSCs offer a high degree of flexibility and can be used as windows or facades, as part of the of building-integrated photovoltaic (BIPV) industry. Existing performance characterizations of LSC devices focus almost exclusively on electric power generation. However, when used as window components, the transmitted spectrum can alter the color, potentially affecting the visual comfort of the occupants by altering the properties of the sunlight. In this study, eight different state-of-the-art nanocrystals are evaluated as potential candidates for LSC window luminophores, using Monte Carlo simulations. The transparency of each LSC window varies between 90% and 50%, and the color-rendering properties are assessed with respect to the color rendering index (CRI) and the correlated color temperature (CCT). It is found that luminophores with a wide absorption bandwidth in the visible spectrum can maintain a high CRI value (above 85) and CCT values close to the Planckian locus, even for high luminophore concentrations. In contrast, luminophores that only absorb partly in the visible spectrum suffer from color distortion, a situation characterized by low CCT and CRI values, even at high transmittance.

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Bui, Thuc Minh, Nguyen Thi Phuong Loan, Phan Xuan Le, Nguyen Doan Quoc Anh, Anh Tuan Le, and Le Van Tho. "Enhancing the CRI and lumen output for the 6600 K WLED with convex-dual-layer remote phosphor geometry by applying red-emitting MGSR3SI2O8:EU2+,MN2+ phosphor." International Journal of Electrical and Computer Engineering (IJECE) 10, no. 4 (August 1, 2020): 3501. http://dx.doi.org/10.11591/ijece.v10i4.pp3501-3507.

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The traditional white LED product established with a single chip and a single phosphor results in a low color rendering index (CRI). The upgrade of LED package is comprised of two chips and one phosphor material and gives the higher CRI while keeping high luminous efficiency. Based on previous findings, the research paper performs the application of the two chips and two phosphors to enhance the color tunability of LEDs with different amounts and intensities of the two employed phosphors. Additionally, a color design model is built to serve the purpose of bettering the color fine-tuning of the white-light LED module. The maximum value of the difference between the measured CIE 1931 color coordinates and that of the simulated model is approximately 0.0063 around the 6600 K correlated color temperature (CCT). From the results, this study offers a quick approach to achieve the color fine tuning of a white-light LED module with a high CRI and luminous efficiency.

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19

Liu, Xin, Xinglu Qian, Peng Zheng, Xiaopu Chen, Yagang Feng, Yun Shi, Jun Zou, Rongjun Xie, and Jiang Li. "Composition and structure design of three-layered composite phosphors for high color rendering chip-on-board light-emitting diode devices." Journal of Advanced Ceramics 10, no. 4 (June 26, 2021): 729–40. http://dx.doi.org/10.1007/s40145-021-0467-0.

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AbstractA three-layered phosphor structure was designed and prepared by the spin coating of BaSi2N2O2:Eu (cyan-emitting) and (Sr,Ca)AlSiN3:Eu (red-emitting) phosphor films on the yellow-emitting Y3Al5O12:Ce (YAG:Ce) phosphor ceramic synthesized by the solid-state reaction under vacuum sintering. In order to achieve high color rendering lighting, the influence of the composition and structure of the three-layered phosphors on the optical, thermal, and electrical properties of the chip-on-board (COB) packaged white-light-emitting diodes (WLEDs) was studied systematically. The WLED with the structure of “red+cyan+yellow” (R+C+Y) three-layered phosphor generated neutral white light and had a luminous efficacy of 75 lm/W, the fidelity index (Rf) of 93, the gamut index (Rg) of 97, and the correlated color temperature (CCT) of 3852 K. Under the excitation of laser diode (LD), the layer-structured phosphor yielded the white light with a luminous efficacy of 120 lm/W, color rendering index (CRI) of 90, and CCT of 5988 K. The result indicates that the three-layered phosphor structure is a promising candidate to achieve high color rendering and high luminous efficacy lighting.

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20

That, Phung Ton, Nguyen Thi Phuong Loan, Le Van Tho, Nguyen Doan Quoc Anh, Hsing-Yuan Liao, Guo-Feng Luo, and Hsiao-Yi Lee. "Enhancing color quality of WLEDs with dual-layer remote phosphor geometry." Materials Science-Poland 38, no. 4 (December 1, 2020): 667–74. http://dx.doi.org/10.2478/msp-2020-0070.

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Abstract Usually, remote phosphor structures are beneficial in terms of flux but unfavorable in terms of color quality compared to conformal phosphor or in-cup phosphor packages. To eliminate this disadvantage, many studies have focused on increasing the chromatic quality of the remote phosphor configuration, which requires great efforts in improving two parameters of color: color rendering index (CRI) and color quality scale (CQS). CRI is known as the most useful quantitative method used to measure the ability of a light source to reproduce the colors of illuminated objects faithfully and naturally. Similarly, CQS is also a method of lighting quality determination and analysis, especially used as an alternative to the unsaturated CRI colors. In this paper, we proposed dual-layer remote phosphor structure as a novel method of CRI and CQS enhancement to improve WLEDs’ color quality. Five alike WLEDs but having different color temperatures in the range of 5600 K to 8500 K were applied in this study. The idea behind the study is to place a red phosphor layer SrwFxByOz:Eu2+,Sm2+ on the yellow phosphor layer YAG:Ce3+ and then determining an appropriate concentration of SrwFxByOz:Eu2+,Sm2+ added to achieve the highest color quality. The results point out that SrwFxByOz:Eu2+,Sm2+ brings great benefits to the improvement of CRI and CQS parameters. Specifically, the higher the SrwFxByOz:Eu2+,Sm2+ concentration results in the greater CRI and CQS, owning to the enriched red light components in the WLEDs. However, the flux has a tendency of dropping when SrwFxByOz:Eu2+,Sm2+ concentration rises excessively. This has been proved by using the Mie-scattering theory and the Lambert-Beer law. The results of this article are essential references for manufacturing WLEDs with higher chromatic quality.

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Wang, Yunfeng, Kai Wang, Zhixia Han, Zhengmao Yin, Chuanjian Zhou, Fanglin Du, Shuyun Zhou, Ping Chen, and Zheng Xie. "High color rendering index trichromatic white and red LEDs prepared from silane-functionalized carbon dots." Journal of Materials Chemistry C 5, no. 37 (2017): 9629–37. http://dx.doi.org/10.1039/c7tc02297b.

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22

Dang, Huu Phuc, Nguyen Thi Phuong Loan, Nguyen Thi Kim Chung, and Nguyen Doan Quoc Anh. "The study of convex-dual-layer remote phosphor geometry in upgrading WLEDs color rendering index." International Journal of Electrical and Computer Engineering (IJECE) 11, no. 5 (October 1, 2021): 3890. http://dx.doi.org/10.11591/ijece.v11i5.pp3890-3896.

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The white-light light-emitting diode (LED) is a semiconductor light source that usually has one chip and one phosphor layer. Because of that simple structure, the color rendering index (CRI) is really poor. Therefore, structure with double layer of phosphor and multiple chips has been studied with the phosphorus proportions and densities in the silicone are constantly changed to find the best option to improve optical properties. In research, we use red phosphor Ca5B2SiO10:Eu3+ layer to place above the yellow phosphor one, and both of them have a convex design. Then, the experiments and measurements are carried out to figure out the effects of this red phosphor as well as the convex-double-layer remote phosphor design on the LED’s performances. The measured results reveal that the light output is enhanced significantly when using convex-dual-layer structure instead of the single-layer design. Additionally, the Ca5B2SiO10:Eu3+ concentration benefits CRI and CQS at around 6600 K and 7700 K correlated color temperature (CCT). Yet, the lumen output shows a slight decline as this red phosphor concentration surpass 26% wt. Through the experiments, it is found that a double layer of chip and double phosphorus is the best structure which could support the quality of CRI and luminous flux.

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Minh, Tran Hoang Quang, Nguyen Huu Khanh Nhan, Nguyen Doan Quoc Anh, Tran Thanh Nam, and Hsiao-Yi Lee. "Improving color uniformity and color rending index of remote-phosphor packaging white LEDs by co-doping SiO2 and Sr2Si5N8:Eu2+ particles." Materials Science-Poland 36, no. 3 (September 1, 2018): 370–74. http://dx.doi.org/10.2478/msp-2018-0061.

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AbstractBased on some advantageous properties, such as fast response time, environment friendliness, small size, long lifetime, and high efficiency, white LEDs are increasingly used in common illumination applications. In this research, by co-doping of redemitting Sr2Si5N8:Eu2+ phosphor and adding SiO2 particles to yellow-emitting YAG:Ce phosphor compounds, a new approach for improving color uniformity and color rending index of remote-phosphor structure white LEDs is proposed and demonstrated. The obtained results clearly indicate that the color rendering index (CRI) and color uniformity (ΔCCT) significantly depend on Sr2Si5N8:Eu2+ concentration. The results provide a potential practical solution for manufacturing remote-phosphor white LEDs (RP-WLEDs) in the near future.

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Le, Phan Xuan, and Le Hung Tien. "Triple-layer remote phosphor structure: a selection of the higher color quality and lumen efficiency for WLEDs." Bulletin of Electrical Engineering and Informatics 10, no. 4 (August 1, 2021): 1960–67. http://dx.doi.org/10.11591/eei.v10i4.3084.

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To enhance color quality of glass-based phosphor-converted white light-emitting diodes (pc-WLEDs) with multi-layer remote phosphor layer structures, two phosphors, green CdS:In and red ZnS:Te,Mn, are integrated into the glass matrix and applied to the dual-layer and triple-layer WLED packages. The attained results were examined with Mie-scattering theory and Lambert-Beer law. The dual-layer showed significant enhancement in color rendering index (CRI), in the range of approximate 80-90. Meanwhile, CRI in the triple-layer was lower and stayed around 66. In terms of color quality scale (CQS), a more overall color evaluating index, triple-layer structure helps the glass-based WLED achieve higher value than the dual-layer. The triple-layer is also beneficial to the luminous efficacy, according to the experimented results. Thus, the triple-layer structure can be used to strengthen the benefit of the glass matrix used in WLED products.

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Nguyen Thi, Dieu An, and Phuc Dang Huu. "Application of green-emitting ZnS:Eu2+ for boosting the spectrum of white light-emitting diode packages." International Journal of Electrical and Computer Engineering (IJECE) 12, no. 5 (October 1, 2022): 4765. http://dx.doi.org/10.11591/ijece.v12i5.pp4765-4771.

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Through utilizing a nonlinear application to acquire the best lumen efficiency (LE) for radiation (also known as LER) when color rendering index (CRI) value, especially CRI of R9 for strong red exceeds 90 with correlated color temperature (CCT) range of 2700-6500 K, the white light emitting diodes (WLED) package with adjustable CCT value and comprised of mixed-type light-emitting diodes (LEDs) can be acquired. The WLED model here contains blue and red LEDs with direct emission and a phosphorconversion blue LED or pc/B-LED (including orange and green phosphors mixed with blue LED colorant). The peak wavelengths of each LED constituent are 465 and 628 nm for LEDs in blue and red, 452 nm for the blue LED colorant, 530 and 586 nm for the phosphors exhibiting green and orange colors. Under the CCT of 2722-6464 K, the attained actual LED package, either with conversion phosphor, in red or in blue, possibly displays both CRI and R9 values measured from 90 to 96, color quality scale (CQS) values measured from 89 to 94, with LERs and LEs of 303-358 lm/W and 105-119 lm/W, respectively.

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26

Desirena, Haggeo, Jorge Molina-González, Octavio Meza, Priscilla Castillo, and Juan Bujdud-Pérez. "Multicolor and Warm White Emissions with a High Color Rendering Index in a Tb3+/Eu3+-Codoped Phosphor Ceramic Plate." Materials 12, no. 14 (July 11, 2019): 2240. http://dx.doi.org/10.3390/ma12142240.

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A series of Tb3+/Eu3+-codoped phosphor ceramic plates with a high color rendering index (CRI) for a near-ultraviolet light emitting diode (LED) were fabricated. Color emission can be tuned from green to reddish as a function of Eu3+ concentration. By doping only 0.15 mol% of Eu3+ concentration, a comfortable warm white emission is promoted as a result of simultaneous emissions of Tb3+ and Eu3+ ions. A theoretical model is proposed to calculate the contributions of the emitted color of the donor (Tb3+) and acceptor (Eu3+) ions in terms of europium concentration. The energy transfer from Tb3+ to Eu3+ ions is corroborated by the luminescence spectra and decay time of Tb3+, with a maximum energy transfer efficiency of 76% for 28 mol% of Tb3+ and 14 mol% of Eu3+. Warm white LEDs were constructed using a 380 nm UV chip and showed a CRI of 82.5, which was one of highest values reported for Tb3+/Eu3+-codoped samples. Color-correlated temperature (CCT), color coordinate (CC), and luminous efficacy (LE) were utilized to know the potentials as a phosphor converter in solid-state lighting.

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Dang Huu, Phuc, and Phan Xuan Le. "Y2O3:Eu3+ concentration and particle size: their impacts on color rendering index and lumen of multi-chip white diodes." Indonesian Journal of Electrical Engineering and Computer Science 27, no. 2 (August 1, 2022): 760. http://dx.doi.org/10.11591/ijeecs.v27.i2.pp760-765.

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Aiming at achieving higher colour standard for multi-chip white light-emitting diode (MCW-LEDs) through the enhancement of their color rendering index (CRI), this article worked on and proposed a novel MCW-LED package using a compound of red phosphor Y2O3:Eu3+. The red phosphors were synthesized and applied to build both protective coating and in-cup phosphor configurations. The CRI of MCW-LED which has high correlated colour heat of 8,500 K was observed to be heightened to 86. Moreover, the scattering of the light when added the red phosphor Y2O3:Eu3+ is demonstrated using Mie-scattering theory, while the influences of the red-light enhancement is analyzed using the law of Lambert-Beer.

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Liu, Lin, Guorui Fu, Baoning Li, Xingqiang Lü, Wai-Kwok Wong, and Richard A. Jones. "Single-component Eu3+–Tb3+–Gd3+-grafted polymer with ultra-high color rendering index white-light emission." RSC Advances 7, no. 11 (2017): 6762–71. http://dx.doi.org/10.1039/c6ra26724f.

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Color-tuning to white-light (CIE coordinates of x = 0.322, y = 0.331; CCT of 5979 K; ultra-high CRI of 94) with a highly luminous efficiency (17.8%) was achieved for single-component Eu³⁺−Tb³⁺−Gd³⁺-grafted polymer Poly(MMA-co-2-co-3-co-4).

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29

Gassara, Mahdi, Rawia Msalmi, Xinghui Liu, Fredj Hassen, Anna Moliterni, Naoufel Ben Hamadi, Ahlem Guesmi, Lotfi Khezami, Taoufik Soltani, and Houcine Naïli. "A promising 1D Cd-based hybrid perovskite-type for white-light emission with high-color-rendering index." RSC Advances 12, no. 52 (2022): 33516–24. http://dx.doi.org/10.1039/d2ra04676h.

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Phuong Loan, Nguyen Thi, and Nguyen Doan Quoc Anh. "Improving color quality and luminous flux of white LED utilizing triple-layer remote phosphor structure." International Journal of Electrical and Computer Engineering (IJECE) 10, no. 5 (October 1, 2020): 5168. http://dx.doi.org/10.11591/ijece.v10i5.pp5168-5174.

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In this manuscript, we presented a research that enhance the performance of WLED using the multi-phosphor configuration. The phosphor layers in the research are separated from each other to achieved better luminous efficiency, however, it makes controlling color light quality more complex. Another issue is finding out the whether two layers of phosphor or three layers of phosphor is better in improving color quality. The research addressed this issue by analyzing the optical aspects of the respective WLEDs that employ these structure. The studied aspects are quality indicators such as luminous efficacy (LE), and color uniformity, color rendering index (CRI), color quality scale (CQS). The results of the experiments in this research, which come from the employment of WLEDs with 2 color temperatures 5600 K and 8500, suggest that WLED with three phosphor layers is better in CRI, CQS, LE. This type of phosphor structure also limits the color deviation significantly, thus, improves the color uniformity. This results is verifies with Mie theory, therefore, can be applied as reference or guideline for production of better WLEDs

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Phuong Loan, Nguyen Thi, and Nguyen Doan Quoc Anh. "The application of double-layer remote phosphor structures in increasing WLEDs color rendering index and lumen output." International Journal of Electrical and Computer Engineering (IJECE) 10, no. 5 (October 1, 2020): 5183. http://dx.doi.org/10.11591/ijece.v10i5.pp5183-5190.

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The remote phosphor structure often has inferior color quality but better luminous flux in than conformal or in-cup configurations. Therefore, numerous researches study remote phosphor structure for methods to enhance it chromatic quality. This study introduces the use of dual-layer remote phosphor structure in WLEDs with identical structure but at different color temperature, 6600K and 7700K, to demonstrate their effect on quality indicators. The concept is placing a green phosphor layer (Ce,Tb)MgAl11O19:Ce:Tb or a red phosphor layer MgSr3Si2O8:Eu2+,Mn2+ on the layer of yellow-emitting phosphor YAG:Ce3+ and find the suitable concentration of the additional phosphor to create the best color quality. The results showed that the increase of CRI and CQS are affected by MgSr3Si2O8:Eu2+,Mn2+, in particular, the higher the concentration of red phosphor gets the better CRI and CQS because the emitted red light in enhanced. The green phosphor layer (Ce,Tb)MgAl11O19:Ce:Tb, on the other hand, is beneficial for the luminous flux. The concentration of MgSr3Si2O8:Eu2+,Mn2+ and (Ce,Tb)MgAl11O19:Ce:Tb, however, need to be adjusted properly to avoid decreasing the luminous flux due to overgrowth. The Mie scattering theory and Beer’s law are the verification tools for these conclusions, which gives them the credibility to be applied in producing better quality WLEDs.

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Wu, Zhenyue, Chengmin Ji, Zhihua Sun, Sasa Wang, Sangen Zhao, Weichuan Zhang, Lina Li, and Junhua Luo. "Broadband white-light emission with a high color rendering index in a two-dimensional organic–inorganic hybrid perovskite." Journal of Materials Chemistry C 6, no. 5 (2018): 1171–75. http://dx.doi.org/10.1039/c7tc04868h.

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Huu, Phuc Dang, and Ton That Phung. "CaS: Sb3+, Na and ZnS:Sn2+: phosphor materials for the improvement of WLEDs." Bulletin of Electrical Engineering and Informatics 11, no. 2 (April 1, 2022): 772–78. http://dx.doi.org/10.11591/eei.v11i2.3300.

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Анотація:

The remote phosphor configuration, though not the best choice for WLED color quality, is superior to the luminous flux of LEDs compared to the conformal or in-cup structures. Realizing the capability of the remote phosphor design, several studies have been done to overcome the drawback of this structure, which is the color quality. A two-film distant phosphor configuration with improved color rendering index (CRI) and color quality ratio (CQS) for WLEDs is offered in this study paper. The hue temperature of the WLEDs packets employed in this research is 8500 K. This phosphor structure is constructed by layering of a green CaS:Sb3+,Na or red ZnS:Sn2+ phosphor above the yellow YAG:Ce3+ phosphor. The additional phosphor ZnS:Sn2+ concentration will then be modified to get the best color quality. The results demonstrated an increase in CRI and CQS along with the presence of ZnS:Sn2+, indicating that the existence of ZnS:Sn2+ influences significantly on these two aspects. As a result of the increased concentration of red illumination elements inside packets, the higher the concentration of ZnS:Sn2+, the higher the CRI and CQS. The green phosphor CaS:Sb3+,Na, in the meantime, improves the luminous flux.

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Menéndez-Velázquez, Amador, Dolores Morales, and Ana Belén García-Delgado. "Sunlike White Light-Emitting Diodes Based on Rare-Earth-Free Luminescent Materials." Materials 15, no. 5 (February 23, 2022): 1680. http://dx.doi.org/10.3390/ma15051680.

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Solid-state lighting (SSL) sources based on light-emitting diodes represent the new generation of highly efficient illumination systems that significantly impact energy-saving. The development of white light-emitting diodes (WLEDs) with a combination of high color rendering index (CRI) and high deep-red color rendering R9 is an important challenge in the field of solid-state lighting. On the other hand, most WLEDs use rare-earth inorganic luminescent materials. The annual demand for rare-earth metals has doubled to 125,000 tons in 15 years, and the demand is projected to reach 315,000 tons in 2030. The explosion in demand for these materials, combined with a monopolistic supply source, represents a real risk for the development of WLEDs in the next few years. Luminescent organic materials are a relevant and promising alternative. Here, we report a WLED with a very high CRI of 95.7 and R9 of 78.7, obtained using a combination of a blue LED chip (excitation source) and two organic luminescent dyes (Coumarin 6 and Lumogen Red) acting as spectral converters in a multilayer remote phosphor configuration. To the best of our knowledge, this is the first rare-earth-free WLED with such high values of CRI and R9.

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35

Yu, Wenjuan, Liang Shen, Xu Jia, Yan Liu, Wenbin Guo, and Shengping Ruan. "Improved color rendering index of low band gap semi-transparent polymer solar cells using one-dimensional photonic crystals." RSC Advances 5, no. 67 (2015): 54638–44. http://dx.doi.org/10.1039/c5ra08137h.

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36

Park, YungKyung. "Approach to CRI (Colour Rendering Index) for full colour RGB LED source lighting." Color and Imaging Conference 18, no. 1 (January 1, 2010): 371–74. http://dx.doi.org/10.2352/cic.2010.18.1.art00065.

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Phuong Loan, Nguyen Thi, and Nguyen Doan Quoc Anh. "Y2O3:Ho3+ and ZnO:Bi3+: a selection for enhancing color quality and luminous flux of WLEDs." International Journal of Electrical and Computer Engineering (IJECE) 10, no. 5 (October 1, 2020): 5162. http://dx.doi.org/10.11591/ijece.v10i5.pp5162-5167.

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As the luminescence industry develops, the white light light-emitting diode (LED) package with a single chip and a single phosphor although produces good luminous flux but has a poor color rendering index (CRI) can no longer fulfill the requirements of modern lighting applications. Therefore, this research is conducted to response to the urgent demands of improving other lighting qualities of WLED while maintaining high luminous efficiency. To achieve this target, we applied the new WLED package, which contains multi-chips and multi-phosphor layers, and have obtained outstanding results in both CRI and luminous efficacy. Two types of phosphor used in the WLED package are Y2O3:Ho3+ and ZnO:Bi3+. A color configuration model is also developed to adjust the shading of the white-light LED module. The results of this research show that the triple-layer phosphorhas the best performance when applied in a white-light LED package, which is demonstrated through better color quality, CRI and luminous efficacy, The manufacturers can rely on this research to produce the optimal-quality WLED, or WLED that is appropriate to their quality demands.

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38

Liem Bui, Van, Nguyen Thi Phuong Loan, and Phan Xuan Le. "Study of ZnS:Mn2+,Te2+ phosphor for improving the hue rendering indicator of WLEDs." Bulletin of Electrical Engineering and Informatics 11, no. 4 (August 1, 2022): 1938–44. http://dx.doi.org/10.11591/eei.v11i4.4061.

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This research combines a phosphor-in-glass (PiG) YAG:Ce3+ with a red liquid-type quantum dot (LQD) to invent high-quality white light-emitting diodes (WLEDs). When the PiG LQD-built WLEDs reach 100 mA, they provide heated white illumination offering an outstanding color rendering index (CRI) (Ra=93.9, R9=97.7, and R13=98.1). The luminescent efficiency (LE) and correlating chromatic temperature, correspondingly, are 62 lm/W and 3764 K. In comparison to PiG integrated with solid-kind quantum dot, it has great LE, remarkable CRI, and lower top layer temperature because of self-aggregation and impediment in the outside flaws in semiconductor quantum dots (QDs) of the solid-condition, as well as effective thermal dissipation. The findings suggest that the produced WLEDs could be potential in high-quality lighting applications.

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39

Li, Xiaoxi, Zifei Wang, Yang Liu, Weiguang Zhang, Chaofeng Zhu, and Xiangeng Meng. "Bright tricolor ultrabroad-band emission carbon dots for white light-emitting diodes with a 96.5 high color rendering index." Journal of Materials Chemistry C 8, no. 4 (2020): 1286–91. http://dx.doi.org/10.1039/c9tc06187h.

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Lee, Gi Jung, Seung Chan Hong, Jung-Gyun Lee, Jae-Hyeon Ko, Taehee Park, Young Wook Ko, and Sergey Lushnikov. "Substantial Improvement of Color-Rendering Properties of Conventional White LEDs Using Remote-Type Red Quantum-Dot Caps." Nanomaterials 12, no. 7 (March 27, 2022): 1097. http://dx.doi.org/10.3390/nano12071097.

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A new type of remote red quantum-dot (QD) component was designed and fabricated to improve the color-rendering properties of conventional white LED (light-emitting diode) lightings. Based on an optical simulation, the rectangular cavity-type QD cap was designed with an opening window on the top surface. Red QD caps were fabricated using a typical injection molding technique and CdSe/ZnS QDs with a core/shell structure whose average size was ~6 nm. Red QD caps were applied to conventional 6-inch, 15-W white LED downlighting consisting of 72 LEDs arrayed concentrically. The red QD caps placed over white LEDs enhanced the red components in the long-wavelength range resulting in the increase of the color rendering index (CRI) from 82.9 to 94.5. The correlated color temperature was tuned easily in a wide range by adopting various configurations consisting of different QD caps. The spatial and angular homogeneities were secured on the emitting area because QD caps placed over the white LEDs did not exhibit any substantial optical path length difference. The present study demonstrates that adopting QD caps in conventional LED lightings provides a flexible and efficient method to realize a high color-rendering property and to adjust correlated color temperature appropriately for a specific application.

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Esikova, Alexandra D., and Alexander G. Fomin. "The Study of Subjective Evaluations of Colour Rendering of White Light Sources with Variable Chromaticity." Light & Engineering, no. 04-2022 (August 2022): 25–30. http://dx.doi.org/10.33383/2021-097.

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The effect of spectral composition of white light sources with variable chromaticity on objective and subjective evaluations of their colour rendering was studied. The dependences of the colour rendering indices on colour temperature were obtained for four light sources: a tungsten halogen lamp, white light emitting diodes with adjustable correlated colour temperature, fluorescent lamps of three colours, and three-colour light emitting diodes. The dependences of general colour rendering index (CRI) Ra and Smet’s memory colour rendering index (MCRI) Rm on the distance uv between a point corresponding to the studied radiation and the blackbody line in the 1960 CIE system (u, v) at constant correlated colour temperature 6500 K were also studied for an installation with three-colour light emitting diodes. The conditions, in which these indices reach their maximum values, were identified.

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42

He, Guoxing, Jing Xu, and Huafeng Yan. "Spectral optimization of warm-white light-emitting diode lamp with both color rendering index (CRI) and special CRI of R9 above 90." AIP Advances 1, no. 3 (September 2011): 032160. http://dx.doi.org/10.1063/1.3644342.

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Lee, Jonghwan, and Ki-Youn Kwon. "Thermal Stress Analysis for High CRI LED Indoor Lighting Module." Journal of Microelectronics and Electronic Packaging 15, no. 3 (July 1, 2018): 126–31. http://dx.doi.org/10.4071/imaps.655549.

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Abstract This research is for developing a new light emitting diode (LED) indoor lighting module with high color rendering index greater than 95. When the LED is operated, electrical energy is generated and heat is released. The failing of heat dispersal degrades the performance and decreases the operating life. To manage the thermal problem effectively, several approaches have been tested in this research study. A heat sink is designed to absorb and transfer heat from the LED module. To analyze the heat flow and thermal stress of the designed LED products effectively, hexahedral mesh generation has been implemented. Heat transfer analysis was performed to find an optimal conductive material. The outcomes of this research study suggest the best material for LED products and show the result of thermal transfer simulation.

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44

Ma, Yuelong, Le Zhang, Tianyuan Zhou, Bingheng Sun, Yun Wang, Jian Kang, Pan Gao, et al. "High recorded color rendering index in single Ce,(Pr,Mn):YAG transparent ceramics for high-power white LEDs/LDs." Journal of Materials Chemistry C 8, no. 13 (2020): 4329–37. http://dx.doi.org/10.1039/d0tc00032a.

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Liu, Zhaoyu, Dong Yao, Huiwen Liu, and Hao Zhang. "Metal Nanoclusters/Polyvinyl Alcohol Composite Films as the Alternatives for Fabricating Remote-Type White Light-Emitting Diodes." Nanomaterials 12, no. 2 (January 8, 2022): 204. http://dx.doi.org/10.3390/nano12020204.

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Packing luminescent metal nanoclusters (MNCs) into polymers and fabricating novel MNCs/polymer composite materials is effective in obtaining high-performance light-emitting diodes (LEDs). Herein, water soluble Cu and Au nanoclusters are encapsulated in polyvinyl alcohol (PVA) by a casting method. The obtained MNCs/PVA composite films are highly emissive with triple primary colors, and inherit the merits of PVA, such as transparency, flexibility, machinability, stability and self-healing ability. By employing the MNCs/PVA composite films as down-conversions, remote type monochromic and white LEDs are fabricated. The white LEDs (WLEDs) exhibit a maximum color rendering index (CRI) of 86 with a Commission Internationale de l’Eclairage (CIE) color coordinate of (0.33,0.35). By varying the three MNCs/PVA film arrangement, the correlated color temperature (CCT) of the WLEDs is tuned from 5582 to 9490 K, which signifies the possibility of MNCs/PVA as alternative light-emitting materials for advanced illumination and display in the future.

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Bui, Thuc Minh, My Hanh Nguyen Thi, Nguyen Doan Quoc Anh, and Nguyen Le Thai. "Triple-layer remote phosphor geometry: an excellent selection to improve the optical properties of white light-emitted diodes." International Journal of Electrical and Computer Engineering (IJECE) 13, no. 5 (October 1, 2023): 5118. http://dx.doi.org/10.11591/ijece.v13i5.pp5118-5125.

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High performance white-light-emitting diodes (WLEDs) have been the goal of recent research on phosphor-in-glass (PiG) devices. In this paper, we introduce a configuration of WLED that achieves high color rendering index (CRI), and correlated color temperature with the addition of Zn2SiO4:Mn2+, As5+ and YAl3O4B12:Eu3+. The technique is lower the temperature during the creation process of phosphor in glass and control the consistent thickness in between 0.5 to 0.7 mm to yield high color quality PiG, high CRI above 80 WLEDs, and extend the color temperature range to 3,900 to 5,300 K. The consistent heat generation combined with extraordinary CRI for PiG prove that low temperature sintering has the potential to create WLEDs with advanced quality. The improved WLEDs can be utilized in many high-demand lighting fields such as chromatic examination, medical analysis, and aesthetic lighting.

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47

Thi, My Hanh Nguyen, Phung Ton That, Nguyen Doan Quoc Anh, and Tran Thanh Trang. "Triple-layer remote phosphor structure: a novel option for the enhancement of WLEDs’ color quality and luminous flux." Materials Science-Poland 38, no. 4 (December 1, 2020): 654–60. http://dx.doi.org/10.2478/msp-2020-0076.

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Анотація:

Abstract The remote phosphor as a lighting structure has outstanding luminous efficiency compared to other options, such as conformal or in-cup. However, the lack of uniformity in distributed color has prevented remote phosphor from wider development. The answer to the chromatic performance enhancement that has been suggested by numerous researchers is the multi-layer configuration with two or three different types of chromatic phosphor. The research purpose is to select the best configuration for multi-chip white LEDs (WLEDs) to achieve optimal results in color quality scale (CQS), color rendering index (CRI), light output and color homogeneity. WLEDs mentioned in this paper have two distinct color temperatures, 6600 K and 7700 K. Experimental results show that the remote phosphor structure with three phosphor layers is superior in terms of color rendering, chromatic performance, and emitted light. The deviation of correlated color measured in this structure is also low, which means that the color uniformity is greatly enhanced in this multi-layer lighting structure. This result can be demonstrated by analyzing the scattering characteristics of the phosphoric layers using the Mie theory. The research findings have proven the effectiveness of the multi-phosphor configuration and can serve as a guideline to fabricate WLEDs with better performance.

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48

Palchikova, Irina, Elena Karamchuk, Evgenii Smirnov, Eugeny Palchikov, and Mikhail Samoylenko. "Multi-functional semiconductor lighting." Proceedings of the Russian higher school Academy of sciences, no. 3 (December 18, 2020): 62–74. http://dx.doi.org/10.17212/1727-2769-2020-3-62-74.

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Анотація:

Features of the development of the multifunctional semiconductor illuminators are discussed. The design and characteristics of the experimental model of the “Photobox 3138” illuminator are described. The lighting variation does not exceed 2 % at the edges of the working field of 300*300 mm. The design includes a white LED illuminator with a color temperature of 5000 K (CIE D50) and a high color rendering index (CRI 97+) and a set of six independently switched monochrome led illuminators in the spectral range from 365 to 880 nm. Digital images of objects obtained in “Photobox 3138” are of use to colorimetric, spectrozonal, and multispectral analysis.

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49

Lee, Hsiao-Yi, Phan Xuan Le, and Doan Quoc Anh Nguyen. "Selecting a Suitable Remote Phosphor Configuration for Improving Color Quality of White Led." Journal of Advanced Engineering and Computation 3, no. 4 (December 31, 2019): 503. http://dx.doi.org/10.25073/jaec.201934.249.

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Анотація:

When compared with two conformal phosphor and in-cup phosphor structures, the remote phosphor structure has higher luminescent performance. However, it is difficult to control the color quality of the remote phosphor structure, so it has become a research target in recent years. So far, there are two remote phosphor structures used to improve color quality including dual-layer phosphor configuration and triple-layer phosphor configuration. This study suggests using those two configurations to make multi-chip white LEDs (WLEDs) that can achieve adequate values in color rendering index (CRI), color quality scale (CQS), luminous efficacy (LE) and color uniformity. WLEDs with a color temperature of 5600 K are applied. Research results show that the triple-layer phosphor configuration is superior in CRI, CQS, LE. Besides, the color deviation decreases significantly, meaning that the color homogeneity increases with the triple-layer phosphor configuration. This can be demonstrated by analyzing the scattering characteristics of phosphor classes through Mie theory, thus making the research results more reliable and valuable for producing quality WLEDs. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium provided the original work is properly cited.

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Pekur, D. V., Yu V. Kolomzarov, V. M. Sorokin, and Yu E. Nikolaenko. "Super powerful LED luminaires with a high color rendering index for lighting systems with combined electric power supply." Semiconductor Physics, Quantum Electronics and Optoelectronics 25, no. 1 (March 24, 2022): 97–107. http://dx.doi.org/10.15407/spqeo25.01.097.

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Considered in this paper are development and creation of high-power LED luminaires with high light efficiency and color rendering index (CRI). As light sources, there used are 6 powerful LED СОВ (Chip-on-Board) modules CreeCXA 2550, the radiation of which contains quasi-chromatic peaks in the spectral range 600…650 nm. It allows to provide CRI values higher than 92. Features of the improved compact construction of the luminaire with indicated COB modules have been presented. To ensure normal thermal regimes of LED COB modules, a small cooling system based on heat pipes has been created, the optimal dimensions of the structural elements of which have been determined by computer simulation. The results of modeling and experimental studies have shown that the developed and manufactured passive cooling system of LED COB modules provides operation temperature modes (up to 85 °C) of light-emitting crystals at the total electric power of COB modules up to 290 W and allows using the luminaires of this type in the systems of continuous artificial illumination with combined power supply. The efficiency of the developed cooling system at some angles to the horizon expands the scope of applying the illumination device.

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