scholarly journals Toward a Connected System—Understanding the Contribution of Light from Different Sources on Occupants’ Circadian Rhythms

2021 ◽  
Vol 11 (21) ◽  
pp. 9939
Author(s):  
Wenye Hu ◽  
Wendy Davis
Keyword(s):  
Circadian Rhythms ◽  
Spectral Irradiance ◽  
Limited Impact ◽  
Circadian Effect ◽  
Electric Light ◽  
Lighting Systems ◽  
Control Light ◽  
Computer Tasks ◽  
Different Sources ◽  
Effect Of Light

Light that enters humans’ eyes and impacts circadian rhythms may come from various sources, including the sun, electric lighting systems, and self-luminous displays. Occupants’ activities strongly impact the light entering their eyes, which is difficult to predict and not yet well understood. This study investigated the circadian contributions of light from different sources in real building environments to better understand the variables that influence the circadian health of occupants. Spectral irradiance distributions at a position equivalent to the front of an eye of a seated occupant in various interior office spaces were collected. Daylight and electric light were measured separately, and light emitted from displays was measured when a variety of different computer tasks was performed. Circadian stimulus (CS) and α-opic irradiance, defined by CIE DIS026/E:2018, were further calculated, and the circadian effects of light from different sources were compared. The results show that daylight has the greatest circadian effect, while electric light in spaces that were predominantly designed with conventional downward lighting has a very limited impact. The circadian effect of light from screens was considerably high. The outcomes suggest that, to optimise the circadian effects of light, connected lighting systems are needed to control light from different sources.

scholarly journals Space of visual and circadian parameters of RGBW lighting systems

2020 ◽  
Vol 1 (57) ◽  
pp. 16-21
Author(s):  
D. Kalustova ◽  
V. Kornaga ◽  
A. Rybalochka ◽  
S. Valyukh
Keyword(s):  
Power Distribution ◽  
Spectral Power ◽  
Visual Comfort ◽  
White Leds ◽  
Spectral Power Distribution ◽  
Circadian Effect ◽  
Lighting Environment ◽  
Lighting Systems ◽  
Colour Rendering ◽  
Effect Of Light

Due to the proven effect of light on human circadian rhythms, nowadays researchers and developers of lighting systems (LS) concentrate on the non-visual parameters of light and methods of ensuring a safe comfortable light environment. This requires optimisation of spectral power distribution (SPD). In this view the most promising and functional are RGBW systems due to their ability to change dynamically SPD and, hence, light parameters. In this work we explore two RGBW (red-greenblue-white) systems with different white LEDs (warm white and neutral white) and the space of visual and non-visual parameters that they can ensure. Visual parameters are studied in terms of colour rendering index, colour fidelity index and visual corneal illuminance while non-visual parameters are studied in terms of circadian light, circadian stimulus and circadian action factor. These parameters are calculated for different contribution of the components in a correlated colour temperature (CCT) range of 2500 – 7000K. In addition, acceptable criterion of the colour fidelity index above 85 is used. It is shown that under this condition the circadian action factor in the range of 0.33-0.98 can be obtained by changing the CCT and (or) colour fidelity index. Also an achievable area of the circadian stimulus versus corneal illuminance space for RGBW systems is found. It enables to choose optimal combination of CCT, circadian stimulus and corneal illuminance to provide the desired level of circadian effect with sufficient visual comfort depending on the daytime and field of system's implementation. This data is useful for LS manufacturers and lighting designers to create a comfortable lighting environment. Keywords - RGBW colour mixing, tunable white light, circadian effect, colour rendering, colour fidelity index.

Effect of light intensity on assimilation characteristics of detached tea leaves

1964 ◽  
Vol 63 (2) ◽  
pp. 265-271 ◽  
Author(s):  
D. N. Barua
Keyword(s):  
Light Intensity ◽  
Chlorophyll Concentration ◽  
Leaf Lamina ◽  
Tea Leaves ◽  
Tungsten Filament ◽  
Strong Light ◽  
Filament Lamp ◽  
Sun Leaves ◽  
Different Sources ◽  
Effect Of Light

Photosynthetic rates of detached, mature tea leaves from four different sources were determined in excess CO2 and light of 4, 10, 16 and 32 klux intensities from a tungsten-filament lamp. Temperature was maintained at 25°C. The assimilation rates were significantly different for the four sources both in weak and in strong light. Neither thickness of the leaf lamina nor chlorophyll concentration could explain the cause of this difference.The effect of shade adaptation on the subsequent rate of assimilation was examined in one of the four sources of leaf. Shade-adapted leaves had significantly higher rates of photosynthesis at the weakest light intensity of 4 klux and lower rates in 16 and 32 klux intensities than the corresponding sun leaves.

Work Zone Lighting and Visual Performance

2013 ◽  
Vol 2337 (1) ◽  
pp. 25-34 ◽  
Author(s):  
John D. Bullough ◽  
Ute C. Besenecker ◽  
Jeremy D. Snyder ◽  
Nicholas P. Skinner
Keyword(s):  
Older Workers ◽  
Full Scale ◽  
Performance Model ◽  
Work Zone ◽  
Visual Performance ◽  
Light Levels ◽  
Lighting Systems ◽  
Control Light ◽  
Computational Analyses

In part because of the potential for high levels of glare from work zone illumination, recommendations for light levels from work zone illumination systems are substantially higher than for levels used along roadways in non–work zone locations. In a two-part study, requirements for work zone illumination light levels were assessed. First, levels for workers varying in age from 20 to 60 years were evaluated with the relative visual performance model, with and without the presence of visibility-reducing glare. Except for the smallest, lowest-contrast tasks performed by the older workers, an illuminance of 10 lx resulted in visibility well above the threshold even in the presence of glare, and an illuminance of 30 lx resulted in suprathreshold visibility for these conditions as well. The results of these computational analyses were largely confirmed in a full-scale, outdoor field demonstration attended by transportation agency engineers and highway contractors. Together, the findings suggest that when lighting systems provide sufficient glare control, light levels do not always need to be especially high to ensure adequate visibility for workers.

scholarly journals The Calculated Circadian Effects of Light Exposure from Commuting

2021 ◽  
Vol 11 (24) ◽  
pp. 11846
Author(s):  
Yihan Lu ◽  
Wenye Hu ◽  
Wendy Davis
Keyword(s):  
Circadian Rhythms ◽  
Light Exposure ◽  
Weather Conditions ◽  
Health Problems ◽  
Spectral Irradiance ◽  
Metropolitan Region ◽  
Circadian Regulation ◽  
Lighting Conditions ◽  
Indoor Lighting ◽  
Daylight Exposure

Light entrains human circadian rhythms, but increased time spent indoors and decreased daylight exposure may disrupt human circadian regulation and cause health problems. Much research is focused on improving indoor lighting conditions to minimize the adverse circadian impact of electric lights, and few studies investigate the circadian impact of daylight during the incidental time that people spend outdoors. For instance, when people commute from home to work, they are exposed to daylight. The purpose of this study is to investigate daylight’s impact on commuters’ circadian rhythms. Measurements of the illuminance and the spectral irradiance distribution (SID) of daylight were taken for three modes of commuting: driving, riding on trains, and walking; and under different weather conditions, on different days, and at different locations throughout the summer and autumn in the Sydney metropolitan region in Australia. With the SID data, three metrics were calculated to estimate the circadian impacts: α-opic irradiance, circadian stimulus (CS), and equivalent melanopic lux (EML). The results suggest that driving or walking on sunny or cloudy days and riding trains on sunny days are beneficial for the commuters’ circadian synchronization.

scholarly journals VALIDATION OF SPECTRAL SIMULATION TOOLS FOR THE PREDICTION OF INDOOR ELECTRIC LIGHT EXPOSURE

2021 ◽  
Author(s):  
C. Pierson ◽  
M. Gkaintatzi-Masouti ◽  
M.P.J. Aarts ◽  
M. Andersen
Keyword(s):  
Light Exposure ◽  
Spectral Characteristics ◽  
Spectral Irradiance ◽  
Spectral Simulation ◽  
Simulation Tools ◽  
Lighting Conditions ◽  
Spectral Simulations ◽  
Electric Light ◽  
Indoor Lighting

As the interest in design applications related to responses to light beyond vision is growing, two simulation tools, ALFA and Lark, have been developed to incorporate spectral characteristics of light in the evaluation of indoor lighting conditions. The spectral characteristics of light are of particular relevance when studying ipRGC-influenced responses. This paper aims to assess the reliability of these tools in predicting indoor spectral irradiance specifically from electric lighting. Spectral irradiance was measured under three indoor electric lighting scenarios and compared against spectral irradiance simulated in ALFA and Lark. While the outcomes of the study tend to show that ALFA is both more accurate and faster, rather large errors were found for spectral irradiance (-28.6% to 33.4%). In comparison to a prior study focusing on daylighting, these results seem to indicate that spectral simulations of electrically lit scenes are generally less accurate than those of daylit scenes with these tools.

scholarly journals A System Simulation Approach for the Control of Stray Electric Light

1991 ◽  
Vol 112 ◽  
pp. 70-70
Author(s):  
T.K. McGowan ◽  
J. Hibbs
Keyword(s):  
System Simulation ◽  
Point Of View ◽  
Stray Light ◽  
Simulation Approach ◽  
Micro Level ◽  
Electric Light ◽  
Lighting Systems ◽  
The Way

ABSTRACTThere are practical ways to improve the way lighting systems are designed and operated where the objective is to control stray light from the astronomical (or other) point of view. Most efforts, however, have been direct toward the lighting hardware or operation on a micro level.

scholarly journals The hygienic assessment of modern sources of light

2010 ◽  
Vol 9 (5) ◽  
pp. 155-159
Author(s):  
T. V. Andropova ◽  
L. P. Volkotrub
Keyword(s):  
Light Sources ◽  
Current State ◽  
Electric Light ◽  
Lighting Systems

This article summarizes the current state of electric lighting systems. Comparing characteristic of different electric sources of light allows to reveal there technical, economical and hygienic advantages. There have been recommended the spheres of application of main types of electric light sources.

scholarly journals Circadian Rhythms: The Price of Electric Light

2017 ◽  
Vol 27 (4) ◽  
pp. R144-R145
Author(s):  
Jonathan S. Emens
Keyword(s):  
Circadian Rhythms ◽  
Electric Light
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