Showing papers in "Lighting Research & Technology in 2012"
TL;DR: Attempts to model the spectral sensitivity of the circadian system are discussed, each of which varies in terms of its complexity and its consideration of retinal neuroanatomy and neurophysiology.
Abstract: It is now well established that the spectral, spatial, temporal and absolute sensitivities of the human circadian system are very different from those of the human visual system. Although qualitati...
239 citations
TL;DR: It is found that applying the adaptive zone concept to a sidelit office with manually operated venetian blinds reduces the predicted hours of intolerable discomfort glare from 735 to 18 occupied hours per year and increases the annual mean daylight availability from 40% to 72%.
Abstract: Discomfort glare is an underutilized parameter in contemporary architectural design due to uncertainties about the meaning of existing metrics, how they should be applied and what the benefits of such analysis are. Glare is position and view direction-dependent within a space, rendering it difficult to assess compared to conventional illuminance-based metrics. This paper compares simulation results for five glare metrics under 144 clear sky conditions in three spaces in order to investigate the ability of these metrics to predict the occurrence of discomfort glare and to hence support the design of comfortable spaces. The metrics analyzed areDaylight Glare Index, CIE Glare Index, Visual Comfort Probability, Unified Glare Rating and Daylight Glare Probability. It is found that Daylight Glare Probability yields the most plausible results. In an attempt to deal with multiple positions and view directions simultaneously, the concept of an ‘adaptive zone’ is introduced within which building occupants may freel...
222 citations
TL;DR: In this paper, a modeling framework for occupant exposure to non-visual effects of light, such as entrainment of the circadian system and maintenance of alertness, has been proposed.
Abstract: This paper investigates the formulation of a modelling framework for the nonvisual effects of daylight, such as entrainment of the circadian system and maintenance of alertness. The body of empirical data from photobiology studies is now sufficient to start developing preliminary non-visual lighting evaluation methods for lighting design. Eventually, these non-visual effects have the potential to become a relevant quantity to consider when assessing the overall daylighting performance of a space. This paper describes the assumptions and general approach that were developed to propose a modeling framework for occupant exposure to non-visual effects of light, and presents a novel means of visualizing the ‘circadian potential’ of a point in space. The proposed approach uses current outcomes of photobiology research to define – at this point static – threshold values for illumination in terms of spectrum, intensity and timing of light at the human eye. These values are then translated into goals for lighting simulation, based on vertical illuminance at the eye, that – ultimately – could become goals for building design. A new climate-based simulation model has been developed to apply these concepts to a residential environment. This will be described in Part 2 of this paper.
134 citations
TL;DR: The results show that whilst pedestrians may spend between 40% and 50% of their time looking at the footpath, not all of that time is spent on critical visual tasks, which raises questions about how appropriate the lighting on residential road using illuminance on the road and pavement is.
Abstract: Despite its importance, very little is found in the literature on the visual tasks of pedestrians, particularly at night. This study was performed to identify and characterise the principal visual tasks of pedestrians at night and the key aspects of the visual environment that are important to pedestrians. In this study, an eye tracking method was employed. Wearing an eye tracker, subjects were asked to walk three different residential routes (5 subjects in day time and 15 subjects at night). In order to obtain further information about the experience of the subjects during the walk, a short interview was performed after completion of the task. The results show that whilst pedestrians may spend between 40% and 50% of their time looking at the footpath, not all of that time is spent on critical visual tasks. Looking at other people appears to be important to pedestrians but during this study the amount of time when subjects fixated on other people was limited. The apparent importance of the visual tasks away from the footpath compared to the tasks on it raises questions about how appropriate it is to specify the lighting on residential road using illuminance on the road and pavement. Language: en
65 citations
TL;DR: In this paper, the effect of blue-enriched white light on the course of mood, sleepiness and light perception over the working day in a real work setting was investigated, and the results showed that the effects of light perception on mood and sleepiness were positively associated with blue-enhanced white light.
Abstract: The aim of this study was to investigate the effect of blue-enriched white light on the course of mood, sleepiness and light perception over the working day in a real work setting. The participants...
55 citations
TL;DR: In this paper, the authors proposed a "daylighting dashboard" to identify buildings that are well-daylit buildings, which is a key component of green building, but no prevailing metric has emerged to help identify buildings with well daylit buildings.
Abstract: Daylight is a key component of green building; however, no prevailing metric has emerged to help identify buildings that are well-daylit buildings. This paper proposes a ‘daylighting dashboard’; a ...
54 citations
TL;DR: In this paper, the authors provide an overview of the present and future challenges facing horticultural lighting and food production in the context of a food and fuel-hungry world.
Abstract: There is an urgent need to find environmentally sustainable technologies that help to address the challenges related to increasing global demand for energy and food. Horticultural lighting allows for year-round cultivation of vegetable crops independent of weather conditions or season of the year. However, high energy prices, environmental impact and market competition are threatening this industry. Although understanding the principles and processes behind human responses to light and lighting is important, the investigation of similar aspects for plants deserves more attention from the lighting research community. This paper provides an overview of the present and future challenges facing horticultural lighting and food production in the context of a food- and fuel-hungry world.
52 citations
TL;DR: In this article, the effects of bright light exposure on the working memory, concentration and sustained attention of elderly persons during three consecutive night shifts were investigated and the results demonstrate that exposure to bright light at night reduces error rates for a working memory task and a concentration performance task but performance on a sustained attention task is completely unaffected.
Abstract: Night shift workers show a decline in performance during working time. Due to demographic change, the labour market requires more elderly people to work at night. Ageing is accompanied by a decrease in cognitive abilities, in the capabilities of the visual system and in coping with night work from the age of 40 onwards. This investigation focuses on the effects of bright light exposure on the working memory, concentration and sustained attention of elderly persons during three consecutive night shifts. After statistical control for neuroticism and intelligence as covariates, the results demonstrate that exposure to bright light at night reduces error rates for a working memory task and a concentration performance task but performance on a sustained attention task is completely unaffected.
48 citations
TL;DR: It is proposed that the benchmark lamp for residential streets in the UK is the low-pressure sodium lamp; if other types of lamps are used, and these have a CIE General Colour Rendering Index of Ra ≥ 60, then the average illuminance can be reduced by an amount that is determined using the new CIE system for mesopic photometry and is dependent on the scotopic/photopic ratio of the lamp.
Abstract: This paper reports a proposed new system for specifying illuminances and lamp types for equal visual effects at mesopic illuminances, developed within the mesopic lighting panel of the Institution of Lighting Professionals in the UK. This study is applied in residential streets and thus the visual tasks considered are those relevant for pedestrians. It is proposed that the benchmark lamp for residential streets in the UK is the low-pressure sodium lamp; if other types of lamps are used, and these have a CIE General Colour Rendering Index of Ra � 60, then the average illuminance can be reduced by an amount that is determined using the new CIE system for mesopic photometry and is dependent on the scotopic/photopic ratio of the lamp.
46 citations
TL;DR: In a laboratory study, participants reported whether they could detect stroboscopic effects from flickering light with a range of frequencies and percent flicker values, and if detected, whether it was acceptable, to provide functional relationships between frequency and% flicker in terms of detection and acceptability of stroboscope effects under conditions corresponding to those tested.
Abstract: Previous studies have demonstrated that the perception of stroboscopic effects from flickering light is strongly influenced by both the frequency and the amount of modulation (eg percent flicker) The relationship, if any, between these factors for the detection and acceptability of stroboscopic effects has not been elucidated under conditions corresponding to illuminating engineering practice In a laboratory study, participants reported whether they could detect stroboscopic effects from flickering light with a range of frequencies and percent flicker values, and if detected, whether it was acceptable The resulting data can provide functional relationships between frequency and percent flicker in terms of detection and acceptability of stroboscopic effects under conditions corresponding to those tested
42 citations
TL;DR: In this article, the performance of 16 Actiwatch Spectrum™ devices for spectral response, directional response and dynamic range was evaluated and a discussion of applicability focussing on spectral response for circadian studies was presented.
Abstract: Through the influence on circadian rhythms, natural and artificial lighting, as well as lifestyle and architecture, affect health and performance. Epidemiological and interventional studies of light-initiated circadian biological outcomes require robust 24‐hour data on personal light exposures, including blue light weighted irradiance data. The performance of the detection systems used is a key factor. We assessed the performance of 16 Actiwatch Spectrum™ devices for spectral response, directional response and dynamic range and propose techniques for calibration, deployment and data analysis for use of the watches in circadian studies. The results are presented, followed by a discussion of applicability focussing on spectral response for circadian studies.
TL;DR: The brain mechanisms involved in light-induced daytime alertness are described and a novel model of two parallel mechanisms, suggested that light can use the amygdala in the limbic system to send signals to the cerebral cortex, is proposed.
Abstract: The effects of light on alertness have been shown several times and the proposed cause has been suppressed melatonin levels. The relation of melatonin and alertness applies at night but not by day when there is hardly any melatonin. Still, light can be used to improve daytime alertness, but how? This paper describes the brain mechanisms involved in light-induced daytime alertness and proposes a novel model of two parallel mechanisms. In addition to the well-established circadian pathway, it is suggested that light can use the amygdala in the limbic system to send signals to the cerebral cortex. The participation of the amygdala in light-induced alertness means that light is provoking and modulating emotions that induce alerting responses. The model is assembled from known relations but has not yet been verified as a functional system. The paper proposes methods to test the model.
TL;DR: In this paper, the authors compared the amount of light scattered back to Earth from a man-made sky glow by LED sources for outdoor lighting, and found that it was significantly less than that of traditional lighting sources.
Abstract: As LED sources are increasingly being used for outdoor lighting, concerns are being raised about their impact on man-made sky glow. This paper compares the amount of light scattered back to Earth f...
TL;DR: Blind systems have been introduced to provide visual and thermal comfort, as well as to reduce energy use in buildings as discussed by the authors, and a wide variety of such systems exist in terms of thermal and optical properti...
Abstract: Blind systems have been introduced to provide visual and thermal comfort, as well as to reduce energy use in buildings. A wide variety of such systems exist in terms of thermal and optical properti...
TL;DR: In this paper, simulated and real tri-and tetrachromatic light-emitting-diode (LED) clusters were optimized for luminous efficacy of radiation (LER) and the memory colour quality metric developed by the authors.
Abstract: Simulated and real tri- and tetrachromatic light-emitting-diode (LED) clusters were optimized for luminous efficacy of radiation (LER) and the memory colour quality metric developed by the authors. The simulated clusters showed no significant differences in achievable colour quality and LER between the different cluster types investigated. The real clusters (composed of commercially available LEDs) showed substantial differences in achievable colour quality and LER between the different cluster types investigated. The real clusters also exhibited a large drop in LER and memory colour quality compared to the simulated clusters due to the limited range of available peak wavelengths and spectral halfwidths. A real tetrachromatic LED lamp, constructed with commercial red, green, blue and warm white LEDs, was optimized for LER and colour quality. In a psychophysical experiment, several aspects of the colour quality of the LED lamp (optimized for 2700 K) and an incandescent lamp were assessed by 18 observers. T...
TL;DR: In this paper, the authors explored the energy performance of an automated lighting control system under realistic conditions in two groups of lecture rooms that have the same shape, dimensions and exposure, and demonstrated that the use of automated systems for electric lighting control can improve the system's energy performance between 40% and 65% depending on the complexity of the system and the parameters under control.
Abstract: Due to new European standards and requirements for energy performance in non-residential buildings, it is important to explore and quantify the benefits of intelligent (automated) energy-efficient operating systems relative to conventional (manual) systems. This paper explores the energy performance of an automated lighting control system under realistic conditions in two groups of lecture rooms that have the same shape, dimensions and exposure. The results demonstrate that the use of automated systems for electric lighting control can improve the energy performance of the system between 40% and 65% depending on the complexity of the system and the parameters under control.
TL;DR: In this paper, an adaptive predictive control strategy for robust control of a daylight-electric light integrated scheme is proposed to elicit daylight variations, occupancy detection and user preferences for real-time control of electric lights and window blinds.
Abstract: Daylight–electric light integrated schemes encompassing soft computing models have been perceived as a lucrative option for lighting energy conservation. This paper exploits the quintessence of design and real-time implementation of an adaptive predictive control strategy for robust control of a daylight–electric light integrated scheme. To elicit daylight variations, occupancy detection and user preferences an online self-adaptive, predictive control algorithm is structured for real-time control of electric lights and window blinds. The adaptive, predictive model entails integration of an online, adaptive daylight illuminance predictor in conjunction with an electric light intensity control algorithm for interior illuminance regulation and a fuzzy-logic based window blind control algorithm to eliminate glare and solar heat gain. The control algorithm modelled with real-time sensor information administers an online process of identification, prediction and parameter adaptation. The prototype controller is successfully implemented in a test chamber. A real-time user-friendly simulator provides an online visualisation of illuminance performance indicators and control of the process. The anticipated synergetic effects of the online control algorithm validated in the test chamber highlights the benefits of the scheme in terms of glare control, illuminance uniformity and energy efficiency.
TL;DR: In this paper, a hybrid lighting system simultaneously delivers daylight and electric light into the core of a building where they are combined and distributed via luminaires, and the system has only been developed in the last few years.
Abstract: Hybrid lighting systems simultaneously deliver daylight and electric light into the core of a building where they are combined and distributed via luminaires. The systems have only been developed i...
TL;DR: Investigations were conducted to test the SPD-dependence of the brightness perception of equal luminance and correlated colour temperature white lights, to find out whether receptors other than cones, such as rods and intrinsically photosensitive retinal ganglion cells, have an influence on brightness.
Abstract: Brightness perception of near-white surfaces is influenced by the spectral power distribution (SPD) of the illuminant; at the same time, this has an effect on task performance, either directly or v...
TL;DR: In this paper, a white-light source based on mixtures of multiple narrow-band light-emitting diodes (LEDs) with the spectrum optimized for high radiant luminous efficacy and good co-existence was proposed.
Abstract: This paper joins the quest for a white-light source based on mixtures of multiple narrow-band light-emitting diodes (LEDs) with the spectrum optimised for high radiant luminous efficacy and good co...
TL;DR: The proposed pruning process removes LEDs so as to minimize the synthesis error and produces the same optimal set of LEDs as those identified by the full-search method but also suggests when using phosphor-converted LEDs is beneficial.
Abstract: Multi-channel light-emitting diode (LED) light sources have been developed for various applications in lighting, but especially for spectrum-tunable lighting. However, how to select the optimal combination of LEDs for these light sources is rarely discussed. Unlike the negative-pruning process which operates by removing LEDs from a set of available LEDs based on an unrealizable negative-coefficient criterion alone, the proposed pruning process removes LEDs so as to minimize the synthesis error. This method not only produces the same optimal set of LEDs as those identified by the full-search method but also suggests when using phosphor-converted LEDs is beneficial. It does this by investigating the trade-off between the full width half maximum of the LEDs and the number of LEDs.
TL;DR: In this paper, the CIE mesopic system is used for road lighting design, which assumes the development of new measurement devices, recommendations and software for road light design, such as a road lighting system.
Abstract: Since practical application of the recently developed CIE mesopic system assumes the development of new measurement devices, recommendations and software for road lighting design, this paper presen...
TL;DR: In the field of goniophotometry, as in many other measurement disciplines, there is an increasing need for laboratories to become ISO-17025 accredited as discussed by the authors, which involves, amongst other things, characte...
Abstract: In the field of goniophotometry, as in many other measurement disciplines, there is an increasing need for laboratories to become ISO-17025 accredited. This involves, amongst other things, characte...
TL;DR: Recent research shows that the incremental improvements in visual performance provided by roadway lighting are correlated with the incremental reductions in night-time crashes, demonstrating that an understanding of visual performance remains important for lighting practice.
Abstract: Visual performance has been studied since the 1930s to help establish a foundation for recommended illuminances. Two approaches were taken to research visual performance, one by Weston in Great Britain and the other by Luckiesh in the United States, leading to different recommended illuminances in the two countries. Because of the energy crisis of the 1970s, applied research into visual performance was undertaken to resolve the discrepancy, resulting in a model of relative visual performance. More recently, a controversy has emerged regarding the value of illuminating roadways. Recent research shows that the incremental improvements in visual performance provided by roadway lighting are correlated with the incremental reductions in night-time crashes, demonstrating that an understanding of visual performance remains important for lighting practice.
TL;DR: The IES Handbook as mentioned in this paper is a very good read for anyone interested in lighting, however, it is not suitable for the general public and it is difficult to read it in any format.
Abstract: Let’s start with the obvious comment about this book; if there is anything called a handbook that weighs 4.6 kg then you know it must come from North America. That said, once you get used to lifting it the handbook is a very good read if you are interested in lighting. This edition of the Handbook is split into 3 sections: ‘Framework’ that covers the basic light technical issues together with the human response to light; ‘Design’ that covers common design process issues; and ‘Applications’ that covers lighting recommendations. The ‘Framework’ section is the most useful to readers outside North America as it provides a review of many of the fundamentals that we all rely on. The chapter Vision: Eye and Brain is a really good review of the subject with some excellent illustrations. The chapter Perceptions and Performance is also an excellent introduction to the topic of visual performance and the psychophysics of the visual system. Elsewhere in this section there is other very good material but in many places you feel let down by the non-inclusion of material or pages that are not properly worked out. For example, in the section of colour there is a really good discussion on colour rendering metrics but it stops short of giving the calculation process for any of them. The page that is typical of many where things are not all they could be is in the section on luminous flux. It defines photopic and scotopic flux with a formula using a sum from 400 to 750 nm whilst on the same page in a table it gives values for v( ) and v0( ) from 360 to 770 nm. Quite why they chose not to use the full range of values given in CIE S010/ E / ISO 23539 Photometry — The CIE System of Physical Photometry is not clear but picking two different ranges makes no sense at all. The ‘Design’ section is something new for the IES Handbook and much of it gives good advice on how to set about delivering good lighting designs. However, when the section gets down to the detailed way things have to be achieved and the rules that need to be followed then its relevance to an audience outside North America is understandably limited. The 17 chapters in the ‘Application’ section all follow the same format and are divided into the same sections: Project Type and Status, Application Types, Illuminance Criteria, Designing and References. A key element of each chapter is a table giving a schedule of illuminance values. The tables are interesting in that in this edition they have changed to using the unit of lux rather than footcandles. However, this seems to be the only use of the metric system as the dimensions that give the locations that have to be illuminated are all given in feet and inches. The other notable feature of the tables is that separate values are given for different age groups. However, the rule across all sections is that where 50% of the population using the space is under 25 the level may be halved and where 50% are over 65 the level is doubled. This statement of the rule might have been a better way of presenting this information. The section makes clear that all of the recommendations given are just that and several times Lighting Res. Technol. 2012; 44: 514–515
TL;DR: In this article, the authors investigated the impact of well geometry and surface reflectance on the vertical daylight factors of walls in atria with square plan forms under a CIE standard overcast sky.
Abstract: This study investigated the impact of well geometry and surface reflectance on the vertical daylight factors of walls in atria with square plan forms under a CIE standard overcast sky. Artificial sky scale model measurements were used to validate predicted values of vertical daylight factors using the software package Radiance. More simulated vertical daylight factors data for a much wider range of square atrium geometries and surface reflectances were then produced. From the results the variations of the vertical daylight factor on the walls of square atria were assessed and explained and some empirical functions derived. Some guidelines for supporting design are presented.
TL;DR: In this article, the authors proposed a sub-points method based on the same principle as standard EN 13201 but protects against a dangerous fault, which allows one to keep the same luminance measure method of verification, giving a more accurate result but needs a different measure of luminous intensity distribution.
Abstract: Light emitting diode (LED) technology creates a new opportunity for designing road lighting. Multi-source LED luminaires can be designed to make their light distribution conform to specific road layouts. However, using Standard EN 13201 to calculate LED road lighting can lead to serious errors. The proposed sub-points method is based on the same principle as Standard EN 13201 but protects against a dangerous fault. It allows one to keep the same luminance measure method of verification, giving a more accurate result but needs a different measure of luminous intensity distribution.
TL;DR: An investigation of the level of disturbance caused by reflections from a variety of display screens, including interactive whiteboards, has been carried out using three test methods: Luminance adjustment, category rating and reading.
Abstract: An investigation of the level of disturbance caused by reflections from a variety of display screens, including interactive whiteboards, has been carried out using three test methods: Luminance adjustment, category rating and reading. The results from the luminance adjustment test and the category rating test were consistent, both showing similar significant effects of lighting-display parameters on the disturbance caused by screen reflections. In contrast, the objective measure of task performance in the reading test was barely responsive to reflections on the screens. Two models have been developed, one to predict the luminaire luminance at which 95% of observers were not disturbed by the reflections and the other to predict the rating of disturbance caused by reflections from the screens. Both models are based on lighting-display parameters including the size and luminance of the reflected light source and the specular reflectance, the effect of haze reflection and the background luminance of the display screen. These models can be used generally, to guide lighting recommendations and, specifically, to identify suitable luminaires to be used with given set of display screens or suitable display screens to be used with a given lighting installation.
TL;DR: The expectations of drivers should be considered when preparing future guidelines for road lighting, as presented to over 100 drivers aged 20–79 years in a questionnaire in Finland during the autumn of 2010.
Abstract: Road lighting practice in Europe is currently under change, the changes being induced by the European Union Ecodesign regulations, the rapid development of LEDs and the new CIE system of mesopic ph...
TL;DR: In this paper, the consequences of misadaptation when suddenly exposed to bright light can by minimised by gradually darkening (photochromic) glasses and this permits better vision, however, the reaction time of...
Abstract: The consequences of misadaptation when suddenly exposed to bright light can by minimised by gradually darkening (photochromic) glasses and this permits better vision. However, the reaction time of ...