Change of circadian effect with colour temperature and eye spectral transmittance at different ages

2020 ◽  
pp. 147715352092337 ◽  
Author(s):  
HJ Tian ◽  
T Chen ◽  
Y Hu ◽  
T Guan ◽  
MP Cai
Keyword(s):  
Pulse Width Modulation ◽  
Spectral Power ◽  
Light Emitting Diode ◽  
Age Groups ◽  
Spectral Transmittance ◽  
Potential Health ◽  
Light Emitting ◽  
Colour Temperature ◽  
Age Related ◽  
Circadian Effect

With the recent advances in photobiology research and light-emitting diode technology, considering the circadian effects and the potential health benefits of lighting has attracted much attention. In this work, to achieve a white light-emitting LED cluster with beneficial and tunable circadian effects, a red-green-blue-warm white colour-mixing method based on pulse width modulation has been introduced and developed. Five optimal spectral power distributions were achieved with the correlated colour temperatures of 2700, 4000, 5000, 6500 and 8000 K that provide maximum colour-rendering indices of 95.0, 96.6, 96.8, 95.6 and 93.5 for each correlated colour temperature. Moreover, the Bellia model was modified to take into account the reduction in spectral transmittance of the human eye that occurs with age. Using the five spectral power distributions, based on the eye spectral transmittance with age-related change, we studied the change of the circadian effect with corneal illuminance at the different correlated colour temperatures. Solutions are provided for scenarios where circadian effect should be avoided for different age groups while the reasonable illuminance and colour temperature are maintained.

scholarly journals Influences of Spectral Power Distribution on Circadian Energy, Visual Comfort and Work Performance

2021 ◽  
Vol 13 (9) ◽  
pp. 4852
Author(s):  
Jack Ngarambe ◽  
Inhan Kim ◽  
Geun Young Yun
Keyword(s):  
Light Source ◽  
Power Distribution ◽  
Work Performance ◽  
Spectral Power ◽  
Light Emitting Diode ◽  
Essential Element ◽  
Visual Comfort ◽  
Light Emitting ◽  
Organic Light Emitting Diode ◽  
Spectral Power Distribution

Spectral power distribution (SPD) is an essential element that has considerable implications on circadian energy and the perception of lit environments. The present study assessed the potential influences of SPD on energy consumption (i.e., considering circadian energy), visual comfort, work performance and mood. Two lighting conditions based on light-emitting diode (LED) and organic light-emitting diode (OLED) were used as proxies for SPDs of different spectral content: dominant peak wavelength of 455 nm (LED) and 618 nm (OLED). Using measured photometric values, the circadian light (CL), melatonin suppression (MS), and circadian efficacy (CE) of the two lighting sources were estimated via a circadian-phototransduction model and compared. Additionally, twenty-six participants were asked to evaluate the said lit environments subjectively in terms of visual comfort and self-reported work performance. Regarding circadian lighting and the associated energy implications, the LED light source induced higher biological actions with relatively less energy than the OLED light source. For visual comfort, OLED lighting-based conditions were preferred to LED lighting-based conditions, while the opposite was true when considering work performance and mood. The current study adds to the on-going debate regarding human-centric lighting, particularly considering the role of SPD in energy-efficient and circadian lighting practices.

The effectiveness of light-emitting diode lighting for providing circadian stimulus in office spaces while minimizing energy use

2019 ◽  
Vol 52 (2) ◽  
pp. 167-188 ◽  
Author(s):  
C Jarboe ◽  
J Snyder ◽  
MG Figueiro
Keyword(s):  
Energy Use ◽  
Spectral Power ◽  
Light Emitting Diode ◽  
Visual Performance ◽  
Luminous Intensity ◽  
Light Emitting ◽  
Lighting Conditions ◽  
Office Space ◽  
Discomfort Glare ◽  
Architectural Lighting

Architectural lighting has traditionally addressed visual performance and horizontal illuminance on the work plane, later focussing on energy efficiency, while only recently paying particular regard to human health outcomes. The present study evaluated the effectiveness of several light-emitting diode lighting strategies for delivering circadian stimulus to occupants of a typical office space while minimizing energy use. The study employed photometric simulations in a typical open-office space, delivering a criterion circadian stimulus of 0.3 to calculation points modelled at the simulated occupants’ eye level. Six luminaire types, two luminous intensity distributions, six spectral power distributions and two horizontal illuminances were evaluated, resulting in 144 unique lighting conditions. Additionally, the study calculated the discomfort glare for selected luminaires with the highest total lumen output, smallest aperture and direct-only luminous intensity distributions at the higher of the two horizontal illuminances (500 lx). The most impactful strategy involved supplementing common overhead lighting with a desktop luminaire delivering light directly to the simulated office occupants’ eyes, which provided greater circadian stimulus and used less energy than overhead luminaires that were capable of delivering the criterion circadian stimulus of 0.3.

Colour-enhanced light emitting diode light with high gamut area for retail lighting

2015 ◽  
Vol 49 (3) ◽  
pp. 329-342 ◽  
Author(s):  
XF Feng ◽  
W Xu ◽  
QY Han ◽  
SD Zhang
Keyword(s):  
Light Source ◽  
Light Emitting Diodes ◽  
Spectral Power ◽  
Light Emitting Diode ◽  
Broad Band ◽  
Area Index ◽  
Light Emitting ◽  
High Preference ◽  
Colour Rendering ◽  
Colour Appearance

Light emitting diodes with high colour quality were investigated to enhance colour appearance and improve observers' preference for the illuminated objects. The spectral power distributions of the light emitting diodes were optimised by changing the ratios of the narrow band red, green and blue light emitting diodes, and the phosphor-converted broad-band light emitting diode to get the desired colour rendering index and high gamut area index. The influence of the light emitting diode light on different coloured fabrics was investigated. The experimental results and the statistical analysis show that by optimising the red, green, blue components the light emitting diode light can affect the colour appearance of the illuminated fabrics positively and make the fabrics appear more vivid and saturated due to the high gamut area index. Observers indicate a high preference for the colours whose saturations are enhanced. The results reveal that the colour-enhanced light emitting diode light source can better highlight products and improve visual impression over the ceramic metal halide lamp and the phosphor-converted light emitting diode light source.

Discomfort glare caused by white LEDs having different spectral power distributions

2017 ◽  
Vol 50 (6) ◽  
pp. 921-936 ◽  
Author(s):  
WJ Huang ◽  
Y Yang ◽  
M Ronnier Luo
Keyword(s):  
White Light ◽  
Spectral Power ◽  
Light Emitting Diode ◽  
Light Emitting ◽  
White Leds ◽  
Significant Difference ◽  
Discomfort Glare ◽  
Led Lights ◽  
Green Leds

This paper describes an experiment to investigate discomfort glare caused by white light-emitting diode (LED) lights having different spectral power distributions. It included two groups: a ‘Metamerism’ group and a ‘correlated colour temperatures (CCT)’ group. In the former group, it was found that white lights at 7000 K constructed from different blue LEDs and the same red and green LEDs gave about the same glare perception. In the latter group, there was a significant difference in glare perception between white lights having different CCTs. Finally, glare models, including unified glare rating (UGR) and the newly derived QUGRspd, and mUGRspd models, were tested using the data from the experiment. All of them gave quite accurate predictions of the data.

The effect of correlated colour temperature of lighting on thermal sensation and thermal comfort in a simulated indoor workplace

2016 ◽  
Vol 27 (3) ◽  
pp. 308-316 ◽  
Author(s):  
Rupak R Baniya ◽  
Eino Tetri ◽  
Jukka Virtanen ◽  
Liisa Halonen
Keyword(s):  
Thermal Comfort ◽  
Room Temperature ◽  
Thermal Sensation ◽  
Light Emitting Diode ◽  
Air Velocity ◽  
Light Emitting ◽  
Colour Temperature ◽  
Test Room ◽  
Illuminance Level ◽  
Colour Rendering

The ‘hue-heat’ hypothesis states that an environment which has wavelengths predominantly toward the red end of the visual spectrum feels ‘warm’ and one with wavelengths mainly toward the blue end feels ‘cool’. In order to test the hypothesis and to study the impacts of the correlated colour temperature of a light source on thermal sensation and thermal comfort, a study was conducted in a test room illuminated with an Light Emitting Diode (LED) lighting system with an adjustable correlated colour temperature where air temperature, air velocity, and relative humidity were kept constant. The correlated colour temperature of lighting inside the test room was changed gradually while keeping the colour rendering index values greater than 90, an illuminance level of 500 lx, and chromaticity difference (Duv) values within the limits of ±0.005. Sixteen study subjects were exposed to a ‘high room temperature’ (25℃) and a ‘low room temperature’ (20℃) on different days. The subjects were adapted to low correlated colour temperature (2700 K), medium correlated colour temperature (4000 K), and high correlated colour temperature (6200 K) lighting for 10 min and subsequently completed the questionnaire about their thermal comfort and thermal sensation. The results of this survey did not provide support for the hue-heat hypothesis and indicated that people felt thermally more comfortable in an indoor workplace at the correlated colour temperature of 4000 K than at the correlated colour temperature of 2700 K or 6200 K.

Different Frequency Bands of Electromagnetic Wave on Age-Related Developmental Changes

2013 ◽  
Vol 479-480 ◽  
pp. 480-485
Author(s):  
Ming Chung Ho ◽  
Chin Fei Huang ◽  
Chia Yi Chou ◽  
Ming Chi Lu ◽  
Chen Hsieh ◽  
...  
Keyword(s):  
Spectral Power ◽  
Brain Activity ◽  
Phase Locking ◽  
Age Groups ◽  
Event Related Potentials ◽  
Brain Dynamics ◽  
Alpha Power ◽  
Time Frequency ◽  
Age Related ◽  
Related Potentials

Brain dynamics is an important issue in understanding child development. However, very little research of the event-related responses has been used to explore changes during childhood. The aim of this study was to investigate mature changes in spatiotemporal organization of brain dynamics. We hypothesized that oscillatory event-related brain activity were affected by age-related changes. The sample include three age groups, namely 7 years (N = 18), 11 years (N = 18), and adults (N = 18). The event-related spectral power (ERPSP), and inter-trial phase locking (ITPL) of the event-related potentials (ERPs) were obtained from the time-frequency analysis of the auditory oddball task. Results revealed that: (a) decreased theta power, but alpha power increased with age; (b) the values of ITPL in the theta and alpha bands increased with age. These suggest that ERPSP, and ITPL provide useful indicators of cognitive maturation processes in children aged 7 and 11 years.

A High Efficiency Step-Up WLED Driver with Wide Range PWM Dimming

2012 ◽  
Vol 588-589 ◽  
pp. 884-887
Author(s):  
Fei Xu ◽  
Le Nian He
Keyword(s):  
Pulse Width Modulation ◽  
High Efficiency ◽  
Light Emitting Diode ◽  
System Efficiency ◽  
Current Sensing ◽  
Light Emitting ◽  
Wide Range ◽  
Simulation Results ◽  
Peak Value ◽  
Pwm Dimming

A high efficiency step-up White Light Emitting-diode (WLED) driver with PWM dimming is presented in this paper. An integrated current sensing technique is used to improve system efficiency. Meanwhile, a novel PWM(pulse width modulation) dimming scheme is proposed to achieve wide range dimming frequency, which can be adaptive to dimming frequency from 200Hz to 200 KHz. The proposed driver is designed with CSMC 0.5um 40V bipolar-CMOS-DMOS process. Simulation results verify the functionality of the design and high efficiency is realized, with a peak value of 94.12% at 5.5V-input and 200mA-load.

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