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Advances in Human-Centric Lighting

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A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Optics and Lasers".

Deadline for manuscript submissions: closed (31 January 2022) | Viewed by 39928

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Special Issue Editors

Prof. Dr. Tran Quoc Khanh

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Guest Editor

Laboratory of Lighting Technology, Darmstadt University of Technology, Darmstadt, Germany
Interests: color imaging; color memory; relation between light and human responses; lighting quality; vehicle lighting
Special Issues, Collections and Topics in MDPI journals

Dr. Vinh Quang Trinh

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Guest Editor

Darmstadt University of Technology, Laboratory of Lighting Technology, Darmstadt, Germany
Interests: LED characterization; color-mixing methods; color sensors; color quality

Dr. Sebastian Babilon

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Guest Editor

Darmstadt University of Technology, Laboratory of Lighting Technology, Darmstadt, Germany
Interests: color imaging; color memory; relation between light and alertness

Special Issue Information

Dear Colleagues,

Human-centric lighting contains the concepts and technological aspects combining the visual performance, emotional and color aspects, and non-imaging-forming (NIF) responses of humans to light exposure. Knowledge on human-centric lighting should be relevant to laying out new lighting systems which take human needs in dependence on weather, season, working contexts, application fields (e.g., schools, hospitals, offices), and time-of-day into account. Human responses to light exposure can be characterized by physiological, psychological, and behavioral measures. This Special Edition reports on advances in the field of research determining the acute and long-term effects of light at different light spectra and intensities, under day- and nighttime conditions in laboratory and field studies. In this context, methods for measuring and quantifying light exposure under different illumination conditions will be described.

Prof. Dr. Tran Quoc Khanh
Dr. Vinh Quang Trinh
Dr. Sebastian Babilon
Guest Editors

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Keywords

daytime light exposure
melatonin suppression
alertness
vitality
physiological and behavioral measures
acute and long-term effects
light spectra
color temperature
time-of-day lighting
seasonal effects
adaptive lighting
daylight

Published Papers (14 papers)

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Research

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27 pages, 3936 KiB

Open AccessArticle

Processing RGB Color Sensors for Measuring the Circadian Stimulus of Artificial and Daylight Light Sources

by Vinh Quang Trinh, Sebastian Babilon, Paul Myland and Tran Quoc Khanh

Appl. Sci. 2022, 12(3), 1132; https://doi.org/10.3390/app12031132 - 21 Jan 2022

Cited by 6 | Viewed by 3525

Abstract

The three main tasks of modern lighting design are to support the visual performance, satisfy color emotion (color quality), and promote positive non-visual outcomes. In view of large-scale applications, the use of simple and inexpensive RGB color sensors to monitor related visual and non-visual illumination parameters seems to be of great promise for the future development of human-centered lighting control systems. In this context, the present work proposes a new methodology to assess the circadian effectiveness of the prevalent lighting conditions for daylight and artificial light sources in terms of the physiologically relevant circadian stimulus (CS) metric using such color sensors. In the case of daylight, the raw sensor readouts were processed in such a way that the CIE daylight model can be applied as an intermediate step to estimate its spectral composition, from which CS can eventually be calculated straightforwardly. Maximal CS prediction errors of less than 0.0025 were observed when tested on real data. For artificial light sources, on the other hand, the CS approximation method of Truong et al. was applied to estimate its circadian effectiveness from the sensor readouts. In this case, a maximal CS prediction error of 0.028 must be reported, which is considerably larger compared to daylight, but still in an acceptable range for typical indoor lighting applications. The use of RGB color sensors is thus shown to be suitable for estimating the circadian effectiveness of both types of illumination with sufficient accuracy for practical applications. Full article

(This article belongs to the Special Issue Advances in Human-Centric Lighting)

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24 pages, 18863 KiB

Open AccessArticle

Evidence for Human-Centric In-Vehicle Lighting: Part 1

by Christopher Weirich, Yandan Lin and Tran Quoc Khanh

Appl. Sci. 2022, 12(2), 552; https://doi.org/10.3390/app12020552 - 6 Jan 2022

Cited by 6 | Viewed by 3252

Abstract

Today, up to hundreds of RGB and W-LEDs are positioned in a vehicle’s interior context and are able to be individually controlled in intensity, color and sequence. However, which kind of illumination distracts or supports car occupants and how to define such a modern illumination system is still under discussion and unknown. For that, first a definition for an in-vehicle lighting system is introduced. Second, a globally distributed study was performed based on a free-access online survey to investigate in-vehicle lighting for visual signaling within 10 colors, eight positions and six dynamic patterns. In total, 238 participants from China and Europe rated color preferences, color moods, light-position preferences, differences between manual and autonomous driving and also different meanings for dynamic lighting patterns. Out of these, three strong significant (p < 0.05) color preference groups were identified with a polarized, accepted or merged character. For the important driving-signaling mood attention, we found a significant hue dependency for Europeans which was missing within the Chinese participants. In addition, we identified that light positioned at the door and foot area was globally favored. Furthermore, we evaluated qualitative results: men are primarily focusing on fast-forward, whereas women paid more attention on practical light usage. These findings conclude the need for a higher lighting-car-occupant adaptation in the future grounded by deeper in-vehicle human factors research to achieve a higher satisfaction level. In interdisciplinary terms, our findings might also be helpful for interior building or general modern cockpit designs for trains or airplanes. Full article

(This article belongs to the Special Issue Advances in Human-Centric Lighting)

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14 pages, 1934 KiB

Open AccessArticle

The Calculated Circadian Effects of Light Exposure from Commuting

by Yihan Lu, Wenye Hu and Wendy Davis

Appl. Sci. 2021, 11(24), 11846; https://doi.org/10.3390/app112411846 - 13 Dec 2021

Cited by 1 | Viewed by 2370

Abstract

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

(This article belongs to the Special Issue Advances in Human-Centric Lighting)

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20 pages, 4169 KiB

Open AccessFeature PaperArticle

Designing Light for Night Shift Workers: Application of Nonvisual Lighting Design Principles in an Industrial Production Line

by Johannes Zauner and Herbert Plischke

Appl. Sci. 2021, 11(22), 10896; https://doi.org/10.3390/app112210896 - 18 Nov 2021

Cited by 6 | Viewed by 3525

Abstract

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

(This article belongs to the Special Issue Advances in Human-Centric Lighting)

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22 pages, 1795 KiB

Open AccessArticle

Testing a Single-Case Experimental Design to Study Dynamic Light Exposure in People with Dementia Living at Home

by Ellen van Lieshout-van Dal, Liselore Snaphaan, Samantha Bouwmeester, Yvonne de Kort and Inge Bongers

Appl. Sci. 2021, 11(21), 10221; https://doi.org/10.3390/app112110221 - 1 Nov 2021

Cited by 1 | Viewed by 2692

Abstract

Most people with dementia live at home supported by informal caregivers, but disturbed sleep patterns may induce a heavy burden of care. The beneficial effects of bright light on their sleep, health, and well-being have been demonstrated in clinical settings, but not in a home situation. We evaluated a dynamic lighting system in a real-life longitudinal single-case experimental design (SCED) with people with dementia living at home. Eleven people with dementia and their informal caregivers were included in this study with four 4-week periods of alternating exposure and nonexposure in an introduction–withdrawal setup (ABAB). Objective light exposure data were collected and analyzed. The used study design seems applicable for this population and suitable for home use. Participant dropout did occur, but was due to health conditions rather than participant burden. The lighting system led to more light in the homes of the participants, as well as to higher actual individual light exposures, although the latter increased only moderately and not consistently across all participants, seasons, and times of day. The participants appreciated the lighting system even after 6 months. We reflect on individual differences, seasonal and daypart influences, and differential light effects. Recommendations and lessons learned are discussed. Full article

(This article belongs to the Special Issue Advances in Human-Centric Lighting)

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22 pages, 7455 KiB

Open AccessArticle

HCL Control Strategy for an Adaptive Roadway Lighting Distribution

by Chun-Hsi Liu, Chun-Yu Hsiao, Jyh-Cherng Gu, Kuan-Yi Liu, Shu-Fen Yan, Chien Hua Chiu and Min Che Ho

Appl. Sci. 2021, 11(21), 9960; https://doi.org/10.3390/app11219960 - 25 Oct 2021

Cited by 4 | Viewed by 2251

Abstract

This study aims to develop a human-centric, intelligent lighting control system using adaptive LED lights in roadway lighting, integrated with an imaging luminance meter that uses an IoT sensor driver to detect the brightness of road surfaces. AI image data are collected for luminance and vehicle conditions analyses to adjust the output of the photometric curve. Type-A lenses are designed for R3 dry roads, while Type-B lenses are designed for W1 wet roads, to solve hazards caused by slippery roads, for optimizing safety and for visual clarity for road users. Data are collected for establishing formulae to optimize road lighting. First, the research uses zonal flux analysis to design secondary optical components of LED roadway lighting. Based on the distribution of LED lights and the target photometric curve, the freeform surface calculation model and formula are established, and control points of each curved surface are calculated using an iterative method. The reflection coefficient of a roadway is used to design optical lenses that take into account the illuminance and luminance uniformity to produce photometric curves accordingly. This system monitors roadway luminance in real time, which simulates drivers’ visual experiences and uses the ZigBee protocol to transmit control commands. This optimizes the output of light according to weather and produces quality roadway lighting, providing a safer driving environment. Full article

(This article belongs to the Special Issue Advances in Human-Centric Lighting)

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12 pages, 916 KiB

Open AccessArticle

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

by Wenye Hu and Wendy Davis

Appl. Sci. 2021, 11(21), 9939; https://doi.org/10.3390/app11219939 - 25 Oct 2021

Cited by 2 | Viewed by 1602

Abstract

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. Full article

(This article belongs to the Special Issue Advances in Human-Centric Lighting)

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20 pages, 34082 KiB

Open AccessArticle

Biodynamic Lighting and Functional Disability; a Single-Case Experimental Design in Three Community Dwelling People with Dementia

by Noortje Aarden-van Delft, Manon Peeters and Liselore Snaphaan

Appl. Sci. 2021, 11(20), 9433; https://doi.org/10.3390/app11209433 - 11 Oct 2021

Cited by 2 | Viewed by 2702

Abstract

Functional disability in people with dementia is associated with placement in long-term care facilities, feelings of depression and caregiver burden. As there is currently no cure for dementia, more attention is needed for personalised support for people living with dementia at home. A promising non-pharmacological innovation for reducing problems in functional activities is biodynamic lighting. This type of artificial lighting resembles a normal daylight curve, including changes in light intensity and colour during the day. The aim of this pilot study with three participants is to explore the possible influence of biodynamic lighting on functional activities over time on people with dementia living at home. The study used an A-B-A-B withdrawal single-case experimental design. In the intervention phases, the participants were exposed to biodynamic lighting, while in the placebo phases, the participants were exposed to placebo light. Both light phases came from the same light system. Based on this study protocol, the quantitative effects of biodynamic light related with functional activity did not reach significance. However, the qualitative results of lighting seem promising with a stabilisation of functional activity experienced over time. Future research should examine the effects that light may have on functional activity more in-depth. This study offers recommendations for longitudinal research. Full article

(This article belongs to the Special Issue Advances in Human-Centric Lighting)

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17 pages, 9145 KiB

Open AccessArticle

Visual Comfort of Tablet Devices under a Wide Range of Ambient Light Levels

by Hsin-Pou Huang, Minchen Wei, Hung-Chung Li and Li-Chen Ou

Appl. Sci. 2021, 11(18), 8679; https://doi.org/10.3390/app11188679 - 17 Sep 2021

Cited by 2 | Viewed by 2387

Abstract

E-reading devices are becoming more and more common in our daily life, and they are used under a wide range of ambient light levels, from completely dark to extremely bright conditions. In this study, a psychophysical experiment is carried out to investigate how ambient light level affects the visual comfort of an e-reading device. Human observers compare the visual comfort of pairs of different text-background lightness combinations on a tablet device under three ambient light levels (i.e., 150, 1500, and 15,000 lx). With our previous work, the experimental results show that the trend of visual comfort interval scales below 1500 lx (i.e., Dark, 150, 300, and 1500 lx) are similar to each other but not for those under illuminance above the 1500 lx (i.e., 3000 and 15,000 lx). For the same lightness difference between text and background, the observers tend to read the text with a white background compared to a black background, especially for 3000 and 15,000 lx. Moreover, a black text on a light-gray background is the most comfortable combination under these two illuminance levels. An evaluation model is proposed based on ambient illuminance, screen parameters, and visual estimation to design an optimal viewing condition when reading on the tablet display. Full article

(This article belongs to the Special Issue Advances in Human-Centric Lighting)

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15 pages, 5112 KiB

Open AccessArticle

A Randomized Controlled Trail for Comparing LED Color Temperature and Color Rendering Attributes in Different Illuminance Environments for Human-Centric Office Lighting

by Sujung Lee and Heakyung C. Yoon

Appl. Sci. 2021, 11(18), 8313; https://doi.org/10.3390/app11188313 - 8 Sep 2021

Cited by 6 | Viewed by 2374

Abstract

In this study, two experiments were conducted to investigate the effects of the color rendering index (CRI) and correlated color temperature (CCT) of light-emitting diode (LED) lighting on office user acceptance and to explore the proper color attributes for human-centric office lighting. Experiment 1 had four LED lights, with two levels for the CRI (CRI < 80: 79, 76; or CRI ≥ 80: 83, 84) and CCT (3000 K or 6500 K) at 300 lux. In experiment 2, there were four LED lights, with several levels for the CRI (CRI < 80: 78; or CRI ≥ 80: 87, 83) and CCT (3000 K or 6500 K) at 500 lux. Ninety-six participants in experiment 1 and ninety-four participants in experiment 2 performed a reading task. The results in experiment 1 and experiment 2 showed that LEDs with lower CRI values at warm color temperatures were rated as more acceptable than LEDs with higher CRI values at warm color temperatures. However, the positive effect extended to LEDs with higher CRI values at cool temperatures but not to LEDs with lower CRI values at cool temperatures. Therefore, the findings are that LEDs with lower CRI values at warm color temperatures and LEDs with higher CRI values at cool temperatures provide the right level of color attributes for office lighting. Full article

(This article belongs to the Special Issue Advances in Human-Centric Lighting)

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14 pages, 1808 KiB

Open AccessArticle

Fabrication of Circadian Light Meter with Non-Periodic Optical Filters to Evaluate the Non-Visual Effects of Light on Humans

by Yun Jae Eo, Seohyeon Kim, Keyong Nam Lee, Dae Hwan Kim, Changwook Kim, Seung Min Lee and Young Rag Do

Appl. Sci. 2021, 11(18), 8283; https://doi.org/10.3390/app11188283 - 7 Sep 2021

Cited by 4 | Viewed by 2010

Abstract

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

(This article belongs to the Special Issue Advances in Human-Centric Lighting)

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19 pages, 5949 KiB

Open AccessArticle

Measurement of Circadian Effectiveness in Lighting for Office Applications

by Sebastian Babilon, Sebastian Beck, Julian Kunkel, Julian Klabes, Paul Myland, Simon Benkner and Tran Quoc Khanh

Appl. Sci. 2021, 11(15), 6936; https://doi.org/10.3390/app11156936 - 28 Jul 2021

Cited by 11 | Viewed by 4710

Abstract

As one factor among others, circadian effectiveness depends on the spatial light distribution of the prevalent lighting conditions. In a typical office context focusing on computer work, the light that is experienced by the office workers is usually composed of a direct component emitted by the room luminaires and the computer monitors as well as by an indirect component reflected from the walls, surfaces, and ceiling. Due to this multi-directional light pattern, spatially resolved light measurements are required for an adequate prediction of non-visual light-induced effects. In this work, we therefore propose a novel methodological framework for spatially resolved light measurements that allows for an estimate of the circadian effectiveness of a lighting situation for variable field of view (FOV) definitions. Results of exemplary in-field office light measurements are reported and compared to those obtained from standard spectral radiometry to validate the accuracy of the proposed approach. The corresponding relative error is found to be of the order of 3–6%, which denotes an acceptable range for most practical applications. In addition, the impact of different FOVs as well as non-zero measurement angles will be investigated. Full article

(This article belongs to the Special Issue Advances in Human-Centric Lighting)

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19 pages, 21014 KiB

Open AccessArticle

Evaluation of Visual and Nonvisual Levels of Daylight from Spectral Power Distributions Considering Orientation and Seasonality

by Silvia Ezpeleta, Elvira Orduna-Hospital, Justiniano Aporta, María José Luesma, Isabel Pinilla and Ana Sánchez-Cano

Appl. Sci. 2021, 11(13), 5996; https://doi.org/10.3390/app11135996 - 28 Jun 2021

Cited by 5 | Viewed by 2090

Abstract

The evaluation of both visual and nonvisual effects from the spectral power distribution (SPD) of outdoor light is critical in lighting design. The dome-light SPD characteristically changes continuously depending on the seasonality, orientation, altitude of the sun or hour of the day. Traditional photopic parameters, such as the illuminance, luminance or correlated colour temperature (CCT), have been widely studied, but presently, there is no melanopic measurement or evaluation method. This article discusses the processes involved in establishing a simple method to determine the SPD of daylight and solar radiation over the skydome in a location to accurately account for the effects of both photopic and circadian levels around a location. Once per month for one year, natural daylight was spectrally measured in the city of Zaragoza (Spain); radiometric and photometric characteristics were analysed by season; and circadian effects were calculated in terms of standard parameters described by the Commission International de l’Eclairage (CIE), factors recommended by normative and scientific backgrounds. Finally, we suggest that the best parameter is the melanopic versus photopic irradiance ratio, which achieves reliable results at simplifying and correlating calculations. Full article

(This article belongs to the Special Issue Advances in Human-Centric Lighting)

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Review

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16 pages, 5760 KiB

Open AccessReview

The Effect of Dynamic Lighting for Working Shift People on Clinical Heart Rate Variability and Human Slow Wave Sleep

by Chien-Yu Chen and Hung-Wei Chen

Appl. Sci. 2022, 12(5), 2284; https://doi.org/10.3390/app12052284 - 22 Feb 2022

Cited by 4 | Viewed by 1803

Abstract

The quality of sleep during lunch breaks will affect the work efficiency, concentration, and mood of workers, and then increase the performance of workers. In this study, Dynamic CCT lighting is proposed as a method to control sleep quality, and a novel hypnotic lighting system is developed according to the experimental design. Pulse width modulation(PWM) is used for controlling sleep lights and adjusting and controlling the spectrum intensity of polychromatic LED to realize the color mixing, which conforms to CCT, illumination, uniformity, and other parameters in the experimental design. The control group of this study is in a dark room, and the experimental group is given dim light and Dynamic CCT lighting. Through volunteer psychological questionnaire evaluation, objective Sleep Wrist Actigraphy and Heart Rate Variability (HRV) are used analyzing sleep quality and Autonomic Nervous System (ANS). The result is found that the sleep environment with Dynamic CCT lighting is better than that with Dim light in three kinds of sleep lighting environments, while the sleep environment of Dynamic CCT lighting is very similar to that of a dark room. In terms of work efficiency after sleep, Dynamic CCT used in the sleep environment of lighting and Dim light is significantly better than that in a dark room. Full article

(This article belongs to the Special Issue Advances in Human-Centric Lighting)

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