Human Lighting Research Articles

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

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.

Biophilic photobiological adaptive envelopes for sub-Arctic buildings: Exploring impacts of window sizes and shading panels’ color, reflectance, and configuration

Northern building envelopes must provide efficient indoor-outdoor connections based on photobiological-psychological needs of occupants for positive relationships with the sub-Arctic nature, particularly daylighting and day/night cycles. Envelope configurations of Northern Canada’s buildings have not yet considered such requirements. Potentials of adaptive systems are also still limited. This research develops a fundamental model of adaptive multi-skin envelopes for sub-Arctic buildings based on main biophilic and photobiological indicators which characterize efficient indoor-outdoor connections. Biophilic indicators characterize the state of connections among occupants and outdoors which could stimulate biological-psychological responses. Photobiological indicators determine human-centric lighting adaptation scenarios for hourly lighting qualities and sufficient darkness in relation to local day/night cycles and daylighting. Biophilic performance of the proposed envelope was evaluated through 18 numerical models in terms of impacts of window and shading sizes on occupants’ field of views. Photobiological lighting performance was evaluated by experimental methods using 23 physical models at 1:10 scale. Surface characteristics of dynamic shading panels, including color, reflectance, orientation, and inclination, were studied for potential photobiological impacts in terms of melanopic/photopic ratios and color temperatures. Results show that the proposed envelope could (i) offer acceptable direct visual connections with the outdoor nature through efficient window sizes for biophilia, and (ii) modify daylighting qualities to address hourly/seasonal photobiological needs of sub-Arctic occupants. Challenges of the proposed envelope to implement under sub-Arctic climatic conditions are underlined especially in terms of energy issues. The research outcomes help architects and decision-makers to improve occupants’ wellbeing and healthy buildings in sub-Arctic climates.

Theoretical justification and practical aspects of implementation of Human Centric Lighting Program in production conditions

The relevance of the introduction of HCL systems in production conditions, in which the dynamics of changes in the characteristics of light flux can be synchronized with the circadian biorhythms of the human body. This is determined by the fact that the unsatisfactory characteristics of industrial lighting increase the risk of injury and occupational morbidity. It is shown that providing only normative quantitative characteristics of illumination is not enough, since its qualitative characteristics – ripple coefficient, spectral composition cause non-visual effect of light. They can affect the psychophysiological state of a person, his\her performance, fatigue by affecting the circadian biorhythms of the body. The comparison of standard values of the level of artificial lighting of jobs in different countries with natural ones. Based on the analysis, recommendations were developed aimed at improving artificial lighting. The analysis of the results of the study of non-visual effect of the pulsation of the light flux on the psychophysiology of a person was carried out. Its main negative consequences are given, the necessary tasks for the implementation of the HCL program in a production environment in this aspect are identified. The results of analysis of studies of the influence of the color temperature of the light flux on the psychophysiological state of a person are also presented. Recommendations on the regulation of this parameter for various types of production activities have been developed.
 
 Keywords: industrial lighting; NIF-effect; occupational injuries.

Advancing Human-Centric LED Lighting Using Na2MgPO4F:Eu2.

The proliferation of energy-efficient light-emitting diode (LED) lighting has resulted in continued exposure to blue light, which has been linked to cataract formation, circadian disruption, and mood disorders. Blue light can be readily minimized in pursuit of "human-centric" lighting using a violet LED chip (λem ≈ 405 nm) downconverted by red, green, and blue-emitting phosphors. However, few phosphors efficiently convert violet light to blue light. This work reports a new phosphor that meets this demand. Na2MgPO4F:Eu2+ can be excited by a violet LED yielding an efficient, bright blue emission. The material also shows zero thermal quenching and has outstanding chromatic stability. The chemical robustness of the phosphor was also confirmed through prolonged exposure to water and high temperatures. A prototype device using a 405 nm LED, Na2MgPO4F:Eu2+, and a green and red-emitting phosphor produces a warm white light with a higher color rendering index than a commercially purchased LED light bulb while significantly reducing the blue component. These results demonstrate the capability of Na2MgPO4F:Eu2+ as a next-generation phosphor capable of advancing human-centric lighting.

Human-Centric Lighting: Foundational Considerations and a Five-Step Design Process.

At its best, human-centric lighting considers the visual and non-visual effects of light in support of positive human outcomes. At its worst, it is a marketing phrase used to healthwash lighting products or lighting design solutions. There is no doubt that environmental lighting contributes to human health, but how might one practice human-centric lighting given both the credible potential and the implausible hype? Marketing literature is filled with promises. Technical lighting societies have summarized the science but have not yet offered design guidance. Meanwhile, designers are in the middle, attempting to distinguish credible knowledge from that which is dubious to make design decisions that affect people directly. This article is intended to: (1) empower the reader with fundamental understandings of ways in which light affects health; (2) provide a process for human-centric lighting design that can dovetail with the decision-making process that is already a part of a designer's workflow.

Human centric lighting in hotel facilities`s interiors

The article describes the features of Human centric lighting and it`s application in hotel facilities`s interiors and aims to proof feasibility of human centric lighting application in hotel facilities`s interiors In modern society, humans spend over 90% or their time indoors. However, despite the growing scientific understanding of the impact of light on biological mechanisms, benefits of this understanding are not harvested in practical systems. Existing light in the built environment, offices in particular, is designed predominantly to meet visual performance requirements. Increasing attention is being given to the biological effects of light, especially how it could be used to promote occupants’ health and well-being through the circadian functions that regulate sleep, mood, and alertness. HCL is used to describe lighting that, considering both visual and non-visual effects of light, aims to enhance the biological and emotional health and well-being of people. Several characteristics of lighting, including quantity, spectrum, timing, duration, and distribution, determine its nonvisual effects on our bodies and minds. Artificial light can be exploited as a means to modulate sleep‐wake schedules and re‐align the internal clock with the environment by phase‐shifting the biological clock. This ability can be used in hotel facilities in order to minimize implications of jet lag in tourists. It is also reasonable to implement human centric lighting systems predominantly at hotel facilities designed for long term stay.

Human-centric lighting: Myth, magic or metaphor?

This paper discusses the rise of human-centric lighting and its current status in lighting. We summarise the human benefits associated with light and lighting and show that human-centric lighting has sound motivations, despite being tainted by misleading marketing claims. The phrase integrative lighting avoids the hype and encapsulates what lighting aspires to be. Embodied in these concepts are some things old and some things new. The old is twofold. First, without diminishing the value of lighting products, the core ingredient for good human outcomes is good design, driven by a design team. Second, light is still for vision, and lighting for visibility, visual comfort and visual amenity is as important as ever. Complementing the old is new awareness and responsibility for how light and lighting influence non-visual responses in humans. Circadian, neuroendocrine and neurobehavioural responses are important for human health and should be considered on-par with visual responses. This awareness leads toward lighting design solutions with increased contrast between day and night. The parties responsible for addressing non-visual responses to light and lighting are evolving. Architects, lighting professionals, lighting equipment manufacturers, medical professionals, building owners and individuals all have a stake, but who should drive decisions and in what proportion?

Present And Future Activities Of The International Commission On Illumination (CIE)

The article describes the main activities of the International Commission on Illumination in recent years. The most important publications are reflecting recent developments in lighting science and industry, including LED sources and luminaires test methods, fundamental recommendations concerning colorimetry, discomfort caused by glare from luminaires with a non-uniform luminance, as well as intelligent control of lighting systems. Human centric lighting and the non-visual effects of light on humans was highlighted. To promote standardization in the field of horticultural lighting the CIE is in the process of establishing a new JTC. In view of COVID‑19 pandemic outspread the use of germicidal UV radiation is of relevance to reduce both contact spread and airborne transmission of infectious agents. The CIE is responsible for worldwide standardization of the fundamentals, including metrology and vocabulary, as well as lighting education. The CIE considers it important to make digital products including validated calculation tools, apps, databases and machine-readable documents more available for many experts and it takes a step in this direction by provide open access to the individual CIE publications.

Parameter Estimation in a Model of the Human Circadian Pacemaker Using a Particle Filter.

In the near future, real-time estimation of peoples unique, precise circadian clock state has the potential to improve the efficacy of medical treatments and improve human performance on a broad scale. Human-centric lighting can bring circadian-rhythm support using biodynamic lighting solutions that sync light with the time of day. We investigate a method to improve the tracking of individual's circadian processes. In literature, the human circadian physiology has been mathematically modeled using ordinary differential equations, the state of which can be tracked via the signal processing concept of a Particle Filter. We show that substantial improvements can be made if the estimator not only tracks state variables, such as the phase and amplitude of the circadian pacemaker, but also fits specific model parameters to the individual. In particular, we optimize model parameter τx, which reflects the intrinsic period of the circadian pacemaker ( τ). We show that both state and model parameters can be estimated based on minimally-invasive light exposure measurements and sleep-wake state observations. We also quantify the effect of inaccuracies in sensing. We demonstrate improved performance by estimating τx for every individual, both with artificially created and human subject data. Prediction accuracy improves with every newly available observation. The estimated τx-s correlate well with the subjects' chronotypes, in a similar way as τ correlates. Our results show that individualizing the estimation of model parameters can improve circadian state estimation accuracy. These findings underscore the potential improvements in personalized models over one-size fits all approaches.

Human Centric Lighting: The impact of light on sleep and attention of factory shift workers

Abstract Introduction Increased blue-enriched morning light is often said to support circadian rhythm synchronization. Through a better sleep quality, one's cognitive and emotional functioning can also be enhanced. However, it is unclear which light characteristics (especially illuminance at eye level) are necessary to obtain a wellbeing effect in employees. This field study investigated different lighting conditions in a truck factory. Methods 71 shift workers participated in the study during their morning shift (6 am - 2 pm). Measurements of sleep (MotionWatch8), attention (D2 attention task, go no-go computer task) and visual comfort (questionnaire) were administered before and after changing the lighting conditions. A Human Centric Lighting-condition (HCL; vertical melanopic equivalent daylight illuminance (MEDI) = 250 lux, CCT=5000 K; N = 33) was compared with a control LED-condition (MEDI = 44 lux, CCT=4000K; N = 38). Results Results show that workers in the HCL-condition showed a larger improvement in sleep efficiency (p=.057) and concentration (p=.01) than the control LED-group. No differences were found in visual comfort between groups. Discussion Preliminary results are promising and show that 250 MEDI might be a sufficient cut-off to stimulate workers' sleep and cognition. The high illuminance level was not detrimental in the HCL condition for the perceived visual comfort. Key messages Blue-enriched morning light supports sleep and concentration in shift workers. High illuminance levels are not detrimental for the perceived visual comfort.

Personalized Office Lighting for Circadian Health and Improved Sleep.

In modern society, the average person spends more than 90% of their time indoors. However, despite the growing scientific understanding of the impact of light on biological mechanisms, the existing light in the built environment is designed predominantly to meet visual performance requirements only. Lighting can also be exploited as a means to improve occupant health and well-being through the circadian functions that regulate sleep, mood, and alertness. The benefits of well-lit spaces map across other regularly occupied building types, such as residences and schools, as well as patient rooms in healthcare and assisted-living facilities. Presently, Human Centric Lighting is being offered based on generic insights on population average experiences. In this paper, we suggest a personalized bio-adaptive office lighting system, controlled to emit a lighting recipe tailored to the individual employee. We introduce a new mathematical optimization for lighting schedules that align the 24-h circadian cycle. Our algorithm estimates and optimizes parameters in experimentally validated models of the human circadian pacemaker. Moreover, it constrains deviations from the light levels desired and needed to perform daily activities. We further translate these into general principles for circadian lighting. We use experimentally validated models of the human circadian pacemaker to introduce a new algorithm to mathematically optimize lighting schedules to achieve circadian alignment to the 24-h cycle, with constrained deviations from the light levels desired for daily activities. Our suggested optimization algorithm was able to translate our findings into general principles for circadian lighting. In particular, our simulation results reveal: (1) how energy constrains drive the shape of optimal lighting profiles by dimming the light levels in the time window that light is less biologically effective; (2) how inter-individual variations in the characteristic internal duration of the day shift the timing of optimal lighting exposure; (3) how user habits and, in particular, late-evening light exposure result in differentiation in late afternoon office lighting.

Indoor Surveillance Camera based Human Centric Lighting Control for Smart Building Lighting Management

The human centric lighting (HCL) control is a major focus point of the smart lighting system design to provide energy efficient and people mood rhythmic motivation lighting in smart buildings. This paper proposes the HCL control using indoor surveillance camera to improve the human motivation and well-beings in the indoor environments like residential and industrial buildings. In this proposed approach, the indoor surveillance camera video streams are used to predict the day lights and occupancy, occupancy specific emotional features predictions using the advanced computer vision techniques, and this human centric features are transmitted to the smart building light management system. The smart building light management system connected with internet of things (IoT) featured lighting devices and controls the light illumination of the objective human specific lighting devices. The proposed concept experimental model implemented using RGB LED lighting devices connected with IoT features open-source controller in the network along with networked video surveillance solution. The experiment results are verified with custom made automatic lighting control demon application integrated with OpenCV framework based computer vision methods to predict the human centric features and based on the estimated features the lighting illumination level and colors are controlled automatically. The experiment results received from the demon system are analyzed and used for the real-time development of a lighting system control strategy.

Human-centric lighting performance of shading panels in architecture: A benchmarking study with lab scale physical models under real skies

This study investigates shading panels’ (SPs) impacts on daylighting features in a lab scale model in terms of parameters representing potential human eyes’ biological responses identified as image forming (IF) and non-image forming (NIF). IF responses enable vision and NIF responses regulate internal body clocks known as circadian clocks. Human-centric lighting evaluates photopic units, representing IF responses, and melanopic units representing NIF responses, combined with correlated color temperature (CCT) of light for potential biological effects. SPs’ impacts on such parameters of daylighting have not yet been studied. Previous research mostly studied panels’ impacts on visual comfort and glare related to IF responses. This research explores the impact of SPs’ color, reflectance, orientation, and openness on photopic and melanopic units and CCT of daylighting inside a 1:50 physical scale model of a space. Approximately 40 prototypes of SPs were evaluated. An experimental setup was designed under outdoor daylighting conditions to capture high dynamic range (HDR) images inside the model. HDR images were post processed to calculate and render the distribution of photopic and melanopic units, melanopic/photopic (M/P) ratios and CCTs in the captured viewpoint of the model. Results reveal the behavior of SPs’ color, reflectance, orientation, and openness in modifying daylighting parameters related to biological responses. Bluish panels, in particular, increase daylighting melanopic units and CCTs whereas reddish panels increase photopic units and reduce CCTs. The research results were discussed to provide an outline for future developments of panels to adapt daylighting to occupants' IF and NIF responses.

The human centric lighting approach for the design of Age-Friendly products

ABSTRACTAs world’s societal wellbeing is growing, in the near future the ‘seniors condition’ will force designers and companies to rethink the way they conceive, produce and sell products. This condition is fundamental for some strategic markets like the lighting domain. In this scenario, Human Centric Lighting (HCL) approach considers both seniors’ biological aspects and technological advances to develop eco-efficient solutions that consider visual and non-visual aspects of light. This paper show the use of HCL as a new design approach able to help designers in the development of a wide range of lighting solutions; from the analysis of human conditions, this paper describes the research process used to design a HCL-Based System that perfectly meets seniors’ needs.

A Simple Designed Lens for Human Centric Lighting Using LEDs

Light is generally important for human beings. Visible light supports vision and can modify circadian rhythm, and together with invisible light at longer or shorter wavelength can also make either a direct or indirect impact on human biological and mental health. For medical applications, several studies have shown success in using light to fasten the skin regeneration in burns and to cure diseases such as newborn jaundice. In daily life, an appropriate amount and time exposure to certain types of light can result in rising of alertness and mood improvement, which leads to noticeable growth in one’s productivity. Therefore, human centric lighting can modify lighting factors to make the best of the natural characteristics of light. The seek an ideal indoor lighting system is widely carried out not only by scientists but also by architects. A qualified luminaire is considered by many factors, including luminous productivity, visual comfort and expenses; meanwhile, the idealization of illuminance is also constructed in many ways, such as widening the lamp’s surface area, changing of luminaire’s positions and applying different methods to illuminate a surface. Approaching these problems, our idea is to study the uplighting method and freeform optics using low-cost acrylic lenses. By changing lens shape and optimizing the factors which affect the illuminance such as the irradiation angle and the distance between the luminaire and the reflection surfaces, we find the most effective lens and its peaks due to each factors using the ray-tracing simulation to obtain results concerning high uniformity of illumination.

Light Beyond Vision: Implications for Human-centric Lighting Design in Tropical Nursing homes

For the elderly people, adequate environment to compensate for increasing frailty and sensory loss are crucial. Normal age-related changes to the eye decrease the amount of light reaching the retina impacting both vision and circadian rhythm. Some attempts have been made recently to conduct tunable white lighting and vary lighting levels and Correlated Colour Temperature (CCT) for health and wellness. However, how to translate such Human-centric Lighting (HCL) concepts proven in laboratory studies into built environments are still in early stage and lack of largely proven practices and strategies on an operational level. This research project aimed to explore HCL design strategies in nursing homes in Singapore. Firstly, state of the art HCL and aging studies were discussed. We then captured the views to illustrate a HCL framework in a tropical context, whereby the quantitative and qualitative approaches were considered. The preliminary design strategies were developed based on this framework and exemplified in a selected nursing home in Singapore. Also, pre-/post implementation user surveys together with quantitative evaluations (involving horizontal and corneal illuminance measurements) were conducted for assessing the performance of the HCL design strategies. These pilot study findings provide initial insight into HCL design-related knowledge and serve as the solid basis towards the HCL best practices in the environment of nursing home in Singapore.

The Spectral Optimization of a Commercializable Multi-Channel LED Panel With Circadian Impact

There exists a need for the design of light emitting diode (LED) luminaires which can deliver both visual and non-visual benefits of light to humans. In this work, we introduce an optimization approach based on spectral shaping for a minimalistic and practical design of a circadian-tunable multi-channel luminaire which also outputs white light with high quality and luminous efficacy of radiation (LER). The spectral optimization approach utilizes Multi-objective Genetic Algorithm to maximize circadian tunability, light quality and LER while minimizing the number of channels. Solution sets are constrained using the non-visual quality metric, Melanopic Efficacy of Luminous Radiation (MELR) from the Melanopic Equivalent Daylight Illuminance (MEDI) approach and the more stringent visual quality metric TM-30 in addition to conventional Color Rendering Index (CRI). By matching theoretically optimized LED parameters to commercially available LED parameters for commercialization purposes, we establish the maximum MELR tunability that is achievable with 4 and 5 LED channels and the resulting trade-off in efficacy and light quality. Based on the results and analysis in this work, we detail a spectral optimization approach to propel the field of indoor lighting towards human-centric lighting.

Eight-month experimental study of energy impact of integrated control of sun shading and lighting system based on HDR vision sensor

One fifth of the electricity consumption of Swiss buildings is due to electric lighting. Integrated control of sun shading and artificial lighting can mitigate this demand while maintaining user comfort. However, the drawback of existing building control approaches is that they do not consider one of the main aspects of human-centric lighting: visual comfort. An ‘on-the-fly’ measurement of a visual comfort index, Daylight Glare Probability (DGP), by a novel High Dynamic Range (HDR) vision sensor was introduced into the building control system optimizing the sun shadings position and electric lighting status. As the first approach, this novel solution was tested during a short-term experiment for 15 afternoons at the LESO solar experimental building. The long-term effect of such novel system was evaluated during an eight-month data monitoring campaign. This experiment was carried out in the same building in order to study the ability of a novel control approach to maintain optimal visual and thermal comfort conditions while reducing the energy performance gap of a room as well as its electric lighting demand. The experimental results showed that the advanced controller mitigated the performance gap during the heating season by 72% with regard to a simulated scenario where a standard occupant manually controls the sun shadings and electric lightings; and by 19% with respect to an experimented scenario with best-practice integrated automated shading and lighting system. This system reduced backup heating demand leading to lower CO2 gas emissions. At the same time, visual comfort constraints regarding DGP and workplane horizontal illuminance were respected for 88.1% of work hours.

7.1: Invited Paper: To see or not to see The Human Centric Lighting is There to Be

7.1: <i>Invited Paper:</i> To see or not to see The Human Centric Lighting is There to Be

Intelligent human-centric lighting for mental wellbeing improvement

In recent years, the main area of interest in the issue of influencing mental states of people is the impact of lighting on human beings, their wellbeing but also workplace productivity. This work discusses in detail the problem of positively influencing people using intelligent technologies, especially the role of the colors. We describe techniques and technologies needed to implement the case study of an intelligent lighting system. The system proposed can detect humans from an IP camera, find faces, and detect emotion. The main aim is to adjust the lights accordingly to the emotional result to improve the mood of people while taking into consideration the principles of color psychology and daytime. We have evaluated our case study solution in a real-world environment and collected the feedback from participants in the form of a questionnaire. Evaluation of participants’ wellbeing was based on their subjective statements. There were several ideas on further functionality extension which needs to be explored. Among them is including wearable devices to the proposed system, validate the emotional results according to them, but also determine the impact of an increasing number of users interacting with the system at the same time.