Multi-function indoor light sources based on light-emitting diodes–a solution for healthy lighting

Wu, Tingzhu; Lin, Yue; Zhu, Honghui; Guo, Ziquan; Zheng, Lili; Lu, Yijun; Shih, Tien-Mo; Chen, Zhong

doi:10.1364/oe.24.024401

Cited by 37 publications

(26 citation statements)

References 19 publications

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“…A methodology named optical power ratio algorithm (OPRA) for obtaining overall SPDs of indoor light sources has been proposed in our previous work [12]. In this work, although it works well for optimizing SPDs to realize both decent mesopic parameters (high S/P ratio) and good color rendering index (CRI) at the same time, this methodology cannot solve the problem that color drifts are commonly observed due to environmental temperature variations.…”

Section: Methodology and Algorithmmentioning

confidence: 99%

“…Therefore, we can readily obtain desirable spectral power distributions (SPDs) of RGBW LEDs by changing optical powers of each chip [11], via PWM currents. However, commonly known as the phenomenon of metamerism, lights with two different SPDs display the same color to human eyes as they share identical chromaticity coordinates (thus identical correlated color temperatures (CCTs)), but different color qualities [12]. Therefore, the set of PWMs of RGBW LEDs should be designed carefully, not only to ensure desirable chromaticity coordinates but also to meet fundamental requirements of mesopic visions and color qualities for the outdoor lighting [13].…”

Section: Introductionmentioning

confidence: 99%

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Improvements of mesopic luminance for light-emitting-diode-based outdoor light sources via tuning scotopic/photopic ratios

Guo

et al. 2017

Opt. Express

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Outdoor light sources must guarantee excellent mesopic luminance (Lmes) for traffic safety at night. Here, we propose a solution to improve mesopic-related parameters, which include especially the scotopic/photopic ratio and the Lmes, of multi-chip light-emitting diode (LED) light sources. Generally, these sources are driven by pulse-width-modulation currents, and possess readily-controlled spectral power distributions (SPDs). An updated version of the optical power ratio algorithm developed in this article can select suitable overall SPDs and yield corresponding duty cycles to drive individual chips at different correlated-color temperatures and operating temperatures. Its accuracy and practicality are proven by experimental results. In addition, our study introduces a temperature-feedback technique that can instantly adjust duty cycles for each chip according to real-time operating temperatures in order to avoid undesirable color drifts at different operating temperatures. It can also be regarded as a model for practitioners who desire to improve the quality of outdoor light sources.

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Section: Methodology and Algorithmmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Improvements of mesopic luminance for light-emitting-diode-based outdoor light sources via tuning scotopic/photopic ratios

Guo

et al. 2017

Opt. Express

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“…In contrast, the static and unchanged spectra of most artificial lighting will disrupt the circadian rhythm [35]. However, the artificial lighting may appear same chromaticity coordinates for different spectra, named as metamerism [36]. It means that one CCT can correspond to a wide span of CAF [12].…”

Section: Introductionmentioning

confidence: 99%

“…Usually multiple LED chips or packages are mixed in the daylight mimicking [6], [7], [12], [17], [27], [29], [34], [36]- [42]. By mixing red, green, cyan and blue (RGCB) monochromatic LEDs, the circadian tunability is higher than that including wide-band white LED (RGBW) [42].…”

Section: Introductionmentioning

confidence: 99%

Tunable LED Lighting With Five Channels of RGCWW for High Circadian and Visual Performances

et al. 2019

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In this study, red, green, cyan, warm white and cool white (RGCWW) LEDs are individually controlled to simulate dynamic daylight. The spectral power distributions (SPDs) are measured for both the daylight and the mixed white light. The correlated color temperature (CCT), circadian action factor (CAF) curves in the daytime of the mixed white LED almost overlap to those of daylight with a small error of about 1%. The CIE chromaticity coordinates of the mixed white light are distributed along the Planckian locus with a little deviation below 0.003. Also, its color rendering index (CRI) is above 90. The RGCWW five-chip LEDs of high circadian and visual performances will benefit to synchronize circadian rhythm in closed environment during long time without daylight, combined with better mood and alertness. The simulation errors and development trend of the mixed lighting are discussed.

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“…It has been a prevalence to simulate SPDs by Gaussian distribution and iterate SPDs for evaluating figures of merit like the color quality, visual performance, circadian effect by algorithms (Wu et al 2016). Among them, brute-force method which can cycle all the conditions in given ranges and steps provides accurate iterative results (Robinson et al 2018).…”

Section: Introductionmentioning

confidence: 99%

Optimization of four-primary white LEDs based on protective effect and color quality-a solution for museum illumination

Dang¹,

Wang²,

Liu³

et al. 2018

Healthy, Intelligent and Resilient Buildings and Urban Environments

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A solution was proposed for obtaining white light-emitting-diodes (LEDs) which are suitable for illuminating traditional Chinese paintings painted with inorganic pigments (iop-TCPs) based on the requirements of protective illumination and color quality. The damage laws and degrees of 450nm, 510nm, 583nm, and 650nm monochromatic lights which can construct four-primary white LEDs on the iop-TCPs were obtained through long-term illumination experiment and data analysis by converting color coordinates into CIE DE2000 color difference values. Then we obtained the damage formula of the constructed white LEDs, which can be used to evaluate damage degree. Spectral power distributions (SPDs) of the white LEDs, which can be iterated by brute-force algorithm, were simulated by the Gaussian formula. Constructed SPDs were evaluated by the damage formula and color quality formulas. The color quality eligible white LEDs with higher correlated color temperatures (CCTs) damage less to iop-TCPs. And the lowest damage SPDs satisfying color quality requirements in CCT ranges from 2700K to 4000K were obtained. Achievements can provide the theory and application basis for manufacturing white LEDs suitable for illuminating iop-TCPs; and the method can be further used in preparing white LEDs applicable to other cultural relics.

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Multi-function indoor light sources based on light-emitting diodes–a solution for healthy lighting

Cited by 37 publications

References 19 publications

Improvements of mesopic luminance for light-emitting-diode-based outdoor light sources via tuning scotopic/photopic ratios

Improvements of mesopic luminance for light-emitting-diode-based outdoor light sources via tuning scotopic/photopic ratios

Tunable LED Lighting With Five Channels of RGCWW for High Circadian and Visual Performances

Optimization of four-primary white LEDs based on protective effect and color quality-a solution for museum illumination

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