Search Results (18)

The design of reliable and accurate indoor lighting control systems for LEDs’ (light-emitting diodes) color temperature and brightness, in an effort to affect human circadian rhythms, has been emerging in the last few years. However, this is quite challenging since parameters, such as the melanopic equivalent daylight illuminance (mEDI), have to be evaluated in real time, using illuminance values and the spectrum of incident light. In this work, to address these issues, a prototype platform has been built based on the low-cost and low-power Arduino UNO R4 Wi-Fi BLE (Bluetooth Low Energy) board, which facilitates experiments with a new control approach for LEDs’ correlated color temperature (CCT). Together with the aforementioned platform, the methodology for mEDI calculation using an 11-channel multi-spectral sensor is presented. With proper calibration of the sensor, the visible spectrum can be reconstructed with a resolution of 1 nm, making the estimation of mEDI more accurate. Full article

Understanding user challenges with light dosimeters is crucial for designing more acceptable devices and advancing light exposure research. We systematically evaluated the usability and acceptability of a light dosimeter (lido) with 29 participants who wore the dosimeter near the corneal plane of the eye for 5 days. Common reasons for not wearing the dosimeter included exercise, recharging, wet environments, public places, and discomfort. Despite these issues, participants adhered to using the dosimeter with high compliance (89% of recording time). Our findings revealed a significant discrepancy between mean (300 lx_mEDI) and median (51 lx_mEDI) melanopic equivalent daylight illuminance. This discrepancy indicates that the participants were exposed to significantly lower light levels most of the time. Specifically, participants were exposed to light levels above 250 lx_mEDI for only 14% of their wearing time. This highlights the need for increased exposure to recommended light levels. In the evening, participants were exposed to less than the recommended 10 lx_mEDI for 58% of their wearing time, which is in line with the guidelines for reducing light exposure before sleep. This study highlights the urgent need for strategies to increase daily light exposure that are more in line with circadian health recommendations. Full article

Daylight plays a crucial role in human health, and as research into its effects expands, it is essential for designers to estimate the non-image-forming impacts of various daylighting and lighting strategies. This allows them to create indoor environments that are both pleasant and comfortable. To support this, daylight measurements were taken in five Chinese cities, focusing on spectral power distribution, correlated color temperature, and illuminance. The study calculated the non-image-forming effects of daylight exposure using metrics like melanopic Equivalent Daylight Illuminance and Circadian Light. A key finding was the development of the action factor S_AI, which estimates the potential non-image-forming effects of light in built environments. This factor serves as a proxy for understanding how non-image-forming effects relate to correlated color temperatures. Additionally, the research suggests the possibility of creating a time-variational daylighting and lighting strategy with four distinct periods of non-image-forming effects throughout a 24 h day. These insights could be valuable for architects and designers in optimizing indoor lighting systems. Full article

Daylight influences more than just our vision; elements such as its intensity and spectral composition can significantly impact our circadian rhythms and, consequently, our overall well-being. In this study, we present an analysis of a classroom simulated in Dialux, involving a comprehensive examination of natural daylight through a specific type of glazing, assessing their photopic characteristics and their influence on the human circadian system in individuals aged 32 and 70 years. Our findings highlight that spectral data from daylight (D75, D65, and D50) and glazing transmittance can be easily used to evaluate the melanopic equivalent daylight illuminance (mel-EDI) in addition to standard photopic illuminance, applying a ${f\left({\displaystyle \frac{M}{P}}\right)}_{Glazing}$ factor calculated from the spectral characteristics of both daylight and glazing transmittance. Our results provide new insights for users to more effectively assess daylighting quality and its implications within indoor environments. Full article

After the pandemic, as it becomes more feasible to study and work from home, the quality of residential daylighting has attracted increasing attention. With the rapid growth of high-density residential areas, China is confronted with the incoordination between site planning and interior daylight availability across a wide region. Therefore, this paper investigates the applicability of planning regulations for daylight availability in dense residential areas under different climates across China, with the aim of providing data to optimize design strategies. ClimateStudio and ALFA were used to calculate the daylight factor (DF), daylight illuminance, spatial daylight autonomy (sDA), useful daylight illuminance (UDI), and melanopic equivalent daylight illuminance (m-EDI) of living rooms in four practical mixed housing estates in different Chinese daylight climate zones. The results showed that most of the studied units failed to meet current standards of DF and sDA_300,50% for residence. However, more than half of these units still had high potential for UDI and met the recommendation of m-EDI by daylight only. The results verified the importance of integrative consideration of the local daylight climate and interior unit design for residential area layout planning. Finally, this paper suggests two topics for further exploration to bridge the gap between area planning and interior daylight availability in dense residential areas. Full article

The paper presents results from a study on integrative lighting in real middle school classrooms located in a school building in Turin, Italy. The contribution of both daylighting and electric lighting was considered. Besides the existing configuration of electric lighting systems (fluorescent luminaires), a set of six possible retrofitting solutions was considered, all using LED luminaires. The research addressed two main objectives: (i) To verify if the circadian values (melanopic equivalent daylight illuminance m-EDI) in the classrooms could meet the recommended values reported in recent literature, for instance, in the WELL protocol, (ii) to assess the influence on integrative lighting (photopic and melanopic illuminances) played by the electric lighting, as a function of the different lighting systems, and by daylighting, as a function of different room orientations and sky conditions. Results showed that the existing spaces benefit from high daylighting amount, whilst the existing lighting systems provide an insufficient m-EDI. Even when last-generation LED lighting systems were ideally used for retrofitting, no solution was able to meet the three-point WELL recommendation, while two solutions only allowed the one-point recommendation to be met. Some design implications concerned with the results were critically discussed. Full article

In the context of intelligent and integrative lighting, in addition to the need for color quality and brightness, the non-visual effect is essential. This refers to the retinal ganglion cells ($ipRGCs$) and their function, which were first proposed in 1927. The melanopsin action spectrum has been published in CIE S 026/E: 2018 with the corresponding melanopic equivalent daylight (D65) illuminance ($mEDI$), melanopic daylight (D65) efficacy ratio ($mDER$), and four other parameters. Due to the importance of $mEDI$ and $mDER$, this work synthesizes a simple computational model of $mDER$ as the main research objective, based on a database of 4214 practical spectral power distributions (SPDs) of daylight, conventional, LED, and mixed light sources. In addition to the high correlation coefficient $R^2$ of 0.96795 and the 97% confidence offset of 0.0067802, the feasibility of the $mDER$ model in intelligent and integrated lighting applications has been extensively tested and validated. The uncertainty between the $mEDI$ calculated directly from the spectra and that obtained by processing the RGB sensor and applying the $mDER$ model reached ± 3.3% after matrix transformation and illuminance processing combined with the successful $mDER$ calculation model. This result opens the potential for low-cost RGB sensors for applications in intelligent and integrative lighting systems to optimize and compensate for the non-visual effective parameter $mEDI$ using daylight and artificial light in indoor spaces. The goal of the research on $RGB$ sensors and the corresponding processing method are also presented and their feasibility is methodically demonstrated. A comprehensive investigation with a huge amount of color sensor sensitivities is necessary in a future work of other research. Full article

Lighting studies that take into account the age of the inhabitants of an area and are related to circadian light are difficult to find. This study aims to simplify a method to approximately compute the circadian light reaching the retina based on photopic illuminance reaching the corneal plane and considering the optical density of an aging crystalline lens. As an example of this proposed method, calculations were performed with both the D65 and A standard illuminants, showing how the spectral power distribution is modified by the optical density of the crystalline lens, mainly at short wavelengths. Due to these selective wavelength absorptions of the aged lens, a significant variation in the level of daylight equivalent melanopic illuminance (EDI) is present in the retina. With levels of 200 lux at the corneal plane, these variations ranged from 204 EDI lux to 178 EDI lux for the D65 standard illuminant, and from 99 EDI lux to 101 EDI lux for the A standard illuminant for observers aged 10 and 90, respectively. In this work, we aimed to simplify the greatest possible level of calculation of melanopic light, while describing simple protocols that are easy to translate into practice. Our results will allow researchers to carry out optimized lighting designs from both the photometric and circadian perspectives considering the optical density of an aging lens. Full article

Although there is a documented preference for daylighting over artificial electric lighting indoors, there are comparatively few investigations of behaviour and perception in indoor day-lit spaces at high latitudes during winter. We report a pilot study designed to examine the effects of static artificial lighting conditions (ALC) and dynamic daylighting conditions (DLC) on the behaviour and perception of two groups of participants. Each group (n = 9 for ALC and n = 8 for DLC) experienced one of the two conditions for three consecutive days, from sunrise to sunset. The main results of this study show the following: indoor light exposure in February in Stockholm can be maintained over 1000 lx only with daylight for most of the working day, a value similar to outdoor workers’ exposure in Scandinavia; these values can be over the recommended Melanopic Equivalent Daylight Illuminance threshold; and this exposure reduces sleepiness and increases amount of activity compared to a static artificial lighting condition. Mood and feeling of time passing are also affected, but we do not exactly know by which variable, either personal or group dynamics, view or variation of the lighting exposure. The small sample size does not support inferential statistics; however, these significant effects might be large enough to be of importance in practice. From a sustainability point of view, daylighting can benefit energy saving strategies and well-being, even in the Scandinavian winter. Full article

Introduction: In 2009, the World Health Organization identified vehicle crashes, both injury-related and fatal, as a public health hazard. Roadway lighting has long been used to reduce crashes and improve the safety of all road users. Ocular light exposure at night can suppress melatonin levels in humans. At sufficient light levels, all visible light wavelengths can elicit this response, but melatonin suppression is maximally sensitive to visible short wavelength light. With the conversion of roadway lighting to solid state sources that have a greater short wavelength spectrum than traditional sources, there is a potential negative health impact through suppressed melatonin levels to roadway users and those living close to the roadway. This paper presents data on the impact of outdoor roadway lighting on salivary melatonin in three cohorts of participants: drivers, pedestrians, and those experiencing light trespass in their homes. Methods: In an outdoor naturalistic roadway environment, healthy participants (N = 29) each being assigned to a cohort of either pedestrian, driver, or light trespass experiment, were exposed to five different solid state light sources with differing spectral emissions and one no lighting condition. Salivary melatonin measurements were made under an average roadway luminance of 1.0 cd/m² (IES RP-18 Roadway Lighting Requirements for expressway roads) with a corneal melanopic Equivalent Daylight Illuminances (EDI) ranging from 0.22 to 0.86 lux. Results: The results indicate that compared to the no roadway lighting condition, the roadway light source spectral content did not significantly impact salivary melatonin levels in the participants in any of the cohorts. Conclusions: These data show that recommended levels of street lighting for expressway roads do not elicit an acute suppression of salivary melatonin and suggest that the health benefit of roadway lighting for traffic safety is not compromised by an acute effect on salivary melatonin. Full article

In this study, we investigated the impact of the lighting environment on psychological perception, physiology, and productivity and then designed lighting control strategies based on the experimental results. The research was conducted in a smart lighting laboratory, and 67 subjects were tested in different illuminances and correlated color temperatures (CCTs). During the experiment, the physiological data of subjects were continuously recorded, while the psychology and productivity results were evaluated by questionnaires and working tests, respectively. The experimental results found that both illuminance and CCT could significantly influence the feeling of comfort and relaxation of the subjects. Warm CCT and higher illuminance (3000 K–590 lux) made subjects feel more comfortable. Productivity reached its maximum value with illuminance above 500 lux and equivalent melanopic lux (EML) higher than 150. The brain-wave and heart-rate changes did not have a close relationship with either illuminance or CCT, but the heart rate slightly increased in the adjustable lighting mode. Regardless of the initial value setting, the subjects preferred intermediate CCT (4200 K) and bright illumination (500 lux) after self-adjustment. Finally, we proposed three comprehensive lighting control strategies based on psychology, productivity, circadian rhythm, and energy-saving. Full article

A holistic approach to daylight dynamics in our built environment can have beneficial outcomes for both physiological and visual effects on humans. Simulations of how daylight variables affect light levels on the horizontal work plane are compared to their physiological effects, measured as melanopic EDI (Melanopic Equivalent Daylight Illuminance) on a vertical plane. The melanopic EDI levels were calculated in a simulated office space in ALFA software (Adaptive Lighting for Alertness) employing the daylight variables of orientation, time of day, season, sky conditions and spatial orientation. Results were analyzed for how daylight design can contribute to the physiological effects of dynamic light in office buildings. Daylight is shown to be a sufficient light source in the majority of cases to meet the recommended values of EDI and provide the suggested horizontal lx level according to the Danish Standards. A mapping of daylight conditions, focusing on the specific factors presented here, can provide guidelines in the design process and future smart building systems. The complex interrelationship between these parameters is important to acknowledge when working with daylight dynamics as a sustainable element in architecture and lighting design. Full article

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. Full article

Chronodisruption deteriorates the health and wellbeing of shift workers. Artificial light at night and the lack of light during the day are major contributors to chronodisruption and need to be optimized in shift work scenarios. Here, we present one solution for a lighting and automation system in an industrial production workplace. The setting is a rapidly rotating shift work environment with morning, evening, and night shifts. We describe a procedure to specify the new lighting through a software-agnostic nonvisual lighting simulation for artificial and daylighting scenarios. Through this process, a new luminaire is created, called Drosa, that allows for a large melanopic stimulus range between 412 and 73 lx melanopic equivalent daylight (D65) illuminance vertically at eye level, while maintaining a neutral white illuminance at task level between 1250 and 900 lx, respectively. This is possible through a combination of glare-free spotlights with adjustable areal wing lights. An individually programmed automation system controls the light dosage and timing during the day and night. The work is relevant for other shift work scenarios, where the presented example and the discussed rationale behind the automation might provide insights. The work is further relevant for other lighting scenarios beyond industrial shift work, as the nonvisual lighting simulation process can be adapted to any context. Full article

Given that light is known to function as a zeitgeber, having the greatest influence on the human circadian rhythm, it is necessary to assess the effects of light on humans with the goal of maintaining the circadian rhythm. Herein, we fabricated a simple circadian light meter that directly measures the non-visual effects of light using optical filters that mimic the non-visual action spectrum. The fabricated light meter was calibrated and verified through the values obtained from a conventional illuminance spectrophotometer. Furthermore, during 24 h of everyday life, 11 participants wore hats equipped with the developed light meter so that we could investigate the effects of the light environment to which they were exposed to, both indoors and outdoors. For comparison, natural outdoor illumination was also measured with the same light meter. Based on the considerable difference between the light exposure levels during the daytime and nighttime, it is possible that the participant’s melatonin levels would be impacted by the light exposure measured by the light meter. Consequently, based on the light exposure measurements made in this study, the proposed circadian light meter would be a valuable tool for real world circadian lighting studies that require actual light dose to the eyes of the test subjects. Full article