Oliver Stefani

Lucerne University of Applied Sciences and Arts | HSLU · Engineering and Architecture

Light profoundly impacts many aspects of human physiology and behaviour, including the synchronization of the circadian clock, the production of melatonin, and cognition. These effects of light, termed the non-visual effects of light, have been primarily investigated in laboratory settings, where light intensity, spectrum and timing can be carefull...

Wearable devices gain increasing attention for use in multifunctional applications related to health monitoring, particularly in research of the circadian rhythms of cognitive functions and metabolic processes. In this comprehensive review, we encompass how wearables can be used to study circadian rhythms in health and disease. We highlight the imp...

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 t...

Light influences human physiology and behaviour by regulating circadian rhythms, melatonin secretion, and alertness. Previous research has reported sex differences in melatonin secretion and circadian rhythms, possibly related to women's greater sensitivity to bright light. Other studies have suggested reduced photosensitivity and earlier circadian...

Light exposure at night can suppress melatonin production and increase alertness, primarily through the action of melanopsin-containing intrinsically photosensitive retinal ganglion cells (ipRGCs). This study investigated whether cone photoreceptors also influence melatonin suppression and subjective alertness using non-visual metameric light emitt...

Whether light exposure during the day reduces non-visual light effects later in the evening has not been studied in adolescents. We investigate whether afternoon-early evening (AEE) light interventions (130 lx, 2500 lx, 4.5 hours, compared to 6.5 lx) would increase melatonin levels during later evening light exposure (130 lx) in a counterbalanced c...

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 the lido (light dosimeter) by 29 participants who wore the dosimeter near the corneal plane of the eye for 5 days. Common reasons for not wearing t...

Background: Human circadian clocks are synchronized daily with the external light-dark cycle and entrained to the 24-hour day. There is increasing evidence that a lack of synchronization and circadian entrainment can lead to adverse health effects. Beyond vision, light plays a critical role in modulating many so-called non-visual functions, includi...

Wearable light loggers are becoming increasingly available for various applications. This study employed a survey design to systematically analyze wearable light loggers, focusing on their key characteristics and usability. A comprehensive survey instrument was developed through expert meetings and iterative discussions, encompassing categories suc...

The pupil modulates the amount of light that reaches the retina. Not only luminance but also the spectral distribution defines the pupil size. Previous research has identified steady-state pupil size and melatonin attenuation to be predominantly driven by melanopsin, which is expressed by a unique subgroup of intrinsically photosensitive retinal ga...

Light profoundly impacts many aspects of human physiology and behaviour, including the synchronization of the circadian clock, the production of melatonin, and cognition. These effects of light, termed the non-visual effects of light, have been primarily investigated in laboratory settings, where light intensity, spectrum and timing can be carefull...

This study explores the relationship between the light features of the Arctic spring equinox and circadian rhythms, sleep and metabolic health. Residents (N = 62) provided week-long actigraphy measures, including light exposure, which were related to body mass index (BMI), leptin and cortisol. Lower wrist temperature (wT) and higher evening blue li...

Background There is no consensus on reporting light characteristics in studies investigating non-visual responses to light. This project aimed to develop a reporting checklist for laboratory-based investigations on the impact of light on non-visual physiology. Methods A four-step modified Delphi process (three questionnaire-based feedback rounds a...

It is well known that variations in light exposure during the day affect light sensitivity in the evening. More daylight reduces sensitivity, and less daylight increases it. On average days, we spend less time outdoors in winter and receive far less light than in summer. Therefore, it could be relevant when collecting research data on the non-image...

Despite rigorous investigation of circadian rhythms in humans and animal models in the past, basic chronobiologic principles have not yet entered clinical practice [...]

Modern humans spend more time indoors than their ancestors. In indoor environments, windows are the primary building elements that provide access to daylight and views. The advancement of the building industry has introduced new glazing and coating technologies for windows. Electrochromic glazing, in particular, has gained popularity in recent deca...

Exposure to natural daylight benefits human well-being, alertness, circadian rhythms and sleep. Many workplaces have limited or no access to daylight. Thus, we implemented a light-panel (“Virtual Sky“), which reproduced nature-adapted light scenarios. In a laboratory office environment, three lighting scenarios were presented during the day: two li...

Evening light-emitting visual displays may disrupt sleep, suppress melatonin and increase alertness. Here, we control melanopic irradiance independent of display luminance and colour, in 72 healthy males 4 h before habitual bedtime and expose each of them to one of four luminance levels (i.e., dim light, smartphone, tablet or computer screen illumi...

Long-term recording of a person’s activity (actimetry or actigraphy) using devices typically worn on the wrist is increasingly applied in sleep/wake, chronobiological, and clinical research to estimate parameters of sleep and sleep-wake cycles. With the recognition of the importance of light in influencing these parameters and with the development...

Future automotive interior lighting might have the potential to go beyond decorative purposes by influencing alertness, circadian physiology, and sleep. As the available space in the interior of an automobile for lighting applications is limited, understanding the impact of various luminous surface sizes on non-image-forming effects is fundamental...

Evening exposure to electric light can acutely suppress melatonin levels and adversely affect subsequent sleep. We conducted a systematic review with meta-analysis investigating the influence of evening illuminance levels on polysomnographically (PSG)-assessed sleep. We also explored how melanopsin (expressed in melanopic equivalent daylight illumi...

Light-induced melatonin suppression data from 29 peer-reviewed publications was analysed by means of a machine learning approach to establish which light exposure characteristics (i.e. photopic illuminance, five α-opic equivalent daylight illuminances (EDIs), duration and timing of the light exposure, and the dichotomous variables pharmacological p...

Smart integrative lighting systems aim to support human health and wellbeing by capitalising on the light-induced effects on circadian rhythms, sleep, and cognitive functions, while optimising the light’s visual aspects like colour fidelity, visual comfort, visual preference, and visibility. Metameric spectral tuning could be an instrument to solve...

Nowadays lighting projects often include temporal variations of the light, both spectrally and in terms of intensity to consider non-visual effects of light on people. However, as of today there are no specific regulations. Compliance with common lighting standards that address visual aspects of light, often means that only little non-visually effe...

Introduction Light emitted from visual displays can acutely increase alertness, improve cognitive performance and suppress melatonin in the evening. Here we tested the influence of different melanopic irradiance levels emitted by a metameric display setting on alertness, vigilance and salivary melatonin levels. Methods In an ongoing study, 37 heal...

We examined whether dynamically changing light across a scheduled 16‐h waking day influences sleepiness, cognitive performance, visual comfort, melatonin secretion, and sleep under controlled laboratory conditions in healthy men. Fourteen participants underwent a 49‐h laboratory protocol in a repeated‐measures study design. They spent the first 5‐h...

The growing awareness of the biological effects of electric light on humans has stimulated ample research. New research has been devoted to lighting solutions that dynamically change their colour to mimic spectral changes of daylight. However, in some situations, the visual properties of light must be preserved, such as when working under standardi...

We examined whether dynamic light across a scheduled 16-h waking day influences cognitive performance, visual comfort, melatonin secretion, sleepiness and sleep under strictly controlled laboratory conditions of 49-h duration. Participants spent the first 5-h in the evening under standard lighting, followed by an 8-h nocturnal sleep episode at habi...

Daylight stems solely from direct, scattered and reflected sunlight, and undergoes dynamic changes in irradiance and spectral power composition due to latitude, time of day, time of year and the nature of the physical environment (reflections, buildings and vegetation). Humans and their ancestors evolved under these natural day/night cycles over mi...

LED *Shared senior authors. light sources have a discontinuous light spectrum with a prominent ‘blue’ peak between 450 and 470 nm that influences non-image forming responses in humans. We tested an LED lighting solution mimicking a daylight spectrum on visual comfort, circadian physiology, daytime alertness, mood, cognitive performance and sleep. F...

Licht ist der wichtigste Zeitgeber für die zirkadianen Rhythmen des Menschen. Es kontrolliert diverse chronobiologische Funktionen, wie etwa den Schlaf-Wach-Rhythmus. Treten bei Nachtarbeit künstliche, phasenverschobene Lichtbedingungen auf, so kann dies zur Desynchronisation der endogenen Rhythmen führen und das Befinden negativ beeinflussen. Um a...

The growing awareness of the biological effects of artificial light on humans has stimulated ample research. It is now widely accepted that asynchrony between artificialand natural light-dark cycles can elicit severe detrimental health effects. New research has been devoted to lighting solutions that dynamically change their color to mimic spectral...

Light is necessary for vision; it enables us to sense and perceive our surroundings and in many direct and indirect ways, via eye and skin, affects our physiological and psychological health. The use of light in built environments has comfort, behavioural, economic and environmental consequences. Daylight has many particular benefits including exce...

Exposure to light has short- and long-term impacts on non-visual responses in humans. While many aspects related to non-visual light sensitivity have been characterised (such as the action spectrum for melatonin suppression), much remains to be elucidated. Here, we provide a set of minimum reporting guidelines for reporting the stimulus conditions...

Autonomous driving provides new opportunities for the use of time during a car ride. One such important scenario is working. We conducted a neuroergonomical study to compare three configurations of a car interior (based on lighting, visual stimulation, sound) regarding their potential to support productive work. We assessed participants? concentrat...

light sources have a discontinuous light spectrum with a prominent ‘blue’ peak between 450 and 470 nm that influences non-image forming responses in humans. We tested an LED lighting solution mimicking a daylight spectrum on visual comfort, circadian physiology, daytime alertness, mood, cognitive performance and sleep. Fifteen young males twice spe...

Das visuelle System des Menschen ist ideal an das Tageslicht angepasst; diverse chronobiologische Rhythmen bzw. Funktionen werden vom Tageslicht kontrolliert. Eine Beleuchtung in der Nacht mit erhöhtem Blauanteil ist wegen der Melatoninsuppression und damit einhergehenden möglichen Befindensstörungen (z. B. chronische Erschöpfung, Schlafstörungen,...

Objectives/Introduction: Current understanding of the term “Human Centric Lighting (HCL)” is the change of correlated color temperature and illuminance across the day. Here we tested the repercussions of a HCL solution on subjective sleepiness and melatonin secretion during two 16:8 hr light:dark cycles in healthy men. Methods: Fourteen male heal...

Besides aesthetic aspects, color can have impact on human perception and behaviour. A special pink hue, the so-called Baker-Miller pink, is assumed to induce calming effects. In this study, we evaluated pink and white lighting conditions with N = 29 subjects, through tests of attention, measurements of skin conductance and emotional state ratings....

In this work, the variation of lighting parameters (illuminance and correlated colour temperature) was used as a prestimulus to investigate effects on cognitive processes. To synchronize the pre-programmed lighting scenarios with the stimulus presentation, a control unit with a short response time was implemented into a LED lighting unit with preci...

Human beings spend much time under the influence of artificial lighting. Often, it is beneficial to adapt lighting to the task, as well as the user’s mental and physical constitution and well-being. This formulates new requirements for lighting - human-centric lighting - and drives a need for new light control methods in interior spaces. In this pa...

Background: Comfort is an important factor in the acceptance of transport systems. In 2010 and 2011, the European Commission (EC) put forward its vision for air travel in the year 2050 which envisaged the use of in-flight virtual reality. This paper addressed the EC vision by investigating the effect of virtual environments on comfort. Research ha...

With LED and OLED taking over the general lighting market, and OLED being the most promising successor technology to LCD with whatever backlight source, both areas have begun to converge. This leads to completely new ways of building and controlling general lighting systems, but also to the possibility (and necessity) to rethink the currently mostl...

Die Studie »LightWork« des LightFusionLab am Fraunhofer IAO untersucht das Benutzerverhalten und die Benutzerakzeptanz von LED-beleuchteten Arbeitsplätzen mit unterschiedlicher Lichtfarbe, sowie die Energieeffizienz einer präsenzbasierten Flurbeleuchtung. Insgesamt 16 Arbeitsplätze des LightFusionLab wurden mit verschiedenen, hinsichtlich Beleuchtu...

Our vision is that regardless of future variations in the interior of airplane cabins, we can utilize ever-advancing state-of-the-art virtual and mixed reality technologies with the latest research in neuroscience and psychology to achieve high levels of comfort for passengers. Current surveys on passenger's experience during air travel reveal that...

VR-HYPERSPACE is a European-funded Seventh Framework project which began in October, 2011 to investigate enhancing passenger comfort in future air travel using state of the art research in neuroscience and psychology of self and space perception, with future visions of virtual reality (VR) and mixed reality (MR) technologies. The goal is to investi...

Zusammenfassung Medizinische und biologische Studien in den letzten Jahren haben gezeigt, dass kurzwelliges Licht einen großen Einfluss auf den menschlichen Organismus haben kann. Neben dem Einsatz von LEDs in Computerbildschirmen ermöglichen dynamische Veränderungen der Lichtfarbe sowie des Dimmzustandes in der Allgemeinbeleuchtung eine Annäherung...

To investigate the hypothesis that a simulation of natural daylight such as a sky with moving clouds would be desirable in offices and if this reproduction increases well-being and reduces subjective tiredness, we developed a luminous ceiling (Virtual Sky) and examined 30 test persons for three times during three weeks. In this paper we provide a t...

— In commodity LC flat-panel displays, the traditional CCFL backlight is being replaced more and more by LEDs. The typical spectrum of LED-lit displays shows a significantly higher amount of blue light in the range around 464 nm. Blue light in this wavelength area suppresses the melatonin level in humans and thus effects the biological clock. Our h...

In recent years, huge advancements in stereoscopic displays and 3D projection technologies have been accomplished, mainly driven by the rapidly increasing dissemination of 3D technologies at cinemas and in consumer products. Virtual Reality systems built from these products, enhanced by head tracking are able to produce a perspective-correct view,...

Immersive visualization environments have generally been built on single user stereoscopic displays. We have extended these systems to multi-view systems that provide perspectively correct stereoscopic image pairs for up to six users. As a result, groups of users can explore a shared 3D virtual environment from all perspectives and discuss it using...

In this paper we present a multi-view stereo display concept based on pulsed LED light sources of a 3 LED/3 LCD projector. Switching LED sources allows high frequency shuttering of the displayed image and can therefore be used for multi-view systems. We have implemented a two user system which can be extended to more views with little expenditure....

In this paper we present research activities on the interaction between light and human emotion. We describe the SmartHeliosity prototype which evaluates human emotions to provide appropriate coloured light in order to enhance emotional wellbeing within the working environment. We present technical specifications, colour concepts to provoke certain...

Many people spend an increasing amount of time in front of computer screens equipped with light-emitting diodes (LED) with a short wavelength (blue range). Thus we investigated the repercussions on melatonin (a marker of the circadian clock), alertness, and cognitive performance levels in 13 young male volunteers under controlled laboratory conditi...

We present the results of clinical user studies comparing the effects of LED- vs. CCFL-backlit displays on humans, resulting from the emitted amount of 464 nm light. The LED-lit display causes significant effects on the user. We present a concept of a display with controllable 464 nm emission.

This paper addresses current research activities on the interaction between light and humans, including visual perception as well as cognitive, biological, and emotional factors. We focus on issues which can be deployed at office workplaces and describe how we adopt these findings at the "nLightened Workplace" at the Fraunhofer Institute for Indust...

In the present paper a VR (Virtual Reality) exposure treatment program for Acrophobia (fear of heights) is introduced and evaluated against an in vivo exposure with the same success rate. During the VR exposure psychophysiological parameters (heart rate, respiratory rate) are collected. VR offers the good opportunity to study psychophysiological ef...

It is commonly acknowledged that user needs should drive design, but often technical influences prevail. Currently, there are no standard interaction devices or interfaces used in 3-D environments, and there is a lack of specific best practice guidelines to develop these. This paper discusses the process of collecting feedback on prototype designs...

Users are increasingly recognizing the potential of virtual reality (VR) technology for applications such as data analysis, design review, product development, production planning, marketing, training, etc. The currently established workflow is to design and construct at a desktop system with CAD or modeling software, and visualize and evaluate the...

Fully immersive and stereoscopic Virtual Environments (VE) represent a powerful multimedia tool for laboratory-based simulations of distinct scenarios including scenarios for evaluating stressful situations resembling reality. Thus far, cortisol secretion as a neuroendocrine parameter of stress has not been evaluated within a Virtual Reality (VR)-b...

In today's society, there is an increasing number of workplaces in virtual environments (VE). But, there are only a few reports dealing with occupational health issues or age effects. The question arises how VR generally interferes with cognitive processes. This interference might have relevant implications for workability and work-efficiency in vi...