A camera-aided method of using high dynamic range photogrammetry was developed to calculate luminous flux radiated to the camera lens from an environment or its subareas, with per-pixel contributions from visible light-emitting sources, objects, and reflective surfaces. A series of equations were derived to calculate the luminous flux with valid sub-divisibility and additivity. A pilot study was first

A recent paper proposed a more precise approach for investigating the impact of ambient light (daylight versus after dark) on road traffic collisions. The present paper first repeated that analysis of road traffic collisions in the UK to test reproducibility; it then extended the analysis to determine whether the greater precision affected the outcome of road traffic collision analyses. Results of

With the recent advances in photobiology research and light-emitting diode technology, considering the circadian effects and the potential health benefits of lighting has attracted much attention. In this work, to achieve a white light-emitting LED cluster with beneficial and tunable circadian effects, a red-green-blue-warm white colour-mixing method based on pulse width modulation has been introduced

Task illuminance is one of the most used parameters in office lighting design and is often used as a ‘single number criterion’ to verify that a lighting design meets the requirements. Although other parameters, such as wall luminance, are often highly correlated with task illuminance, not taking these explicitly into account means critical user criteria such as comfort and satisfaction are left to

In 2012, an open letter signed by nine Nobel laureates made stinging criticism of the UK Engineering and Physical Sciences Research Council (EPSRC) and called for an urgent review of how funding decisions are made. The signatories of the letter claimed that:

It is critical for the safety of miners to be able to escape, unaided, during a mine emergency. Self-escape is challenging in the presence of smoke that can occur during a mine emergency. To assist self-escape, coloured markers in underground mines designate the primary/secondary escapeways, but no universal colour code exists. Ten participants were tested to recognize the colour and designation (primary/secondary)

There is an ongoing transition from high-pressure sodium lamps to LED street lamps that offer higher efficiency, cost saving and better photometric performance. This transition could lead to unintended consequences such as light flicker and extinguishing in street lighting applications when they are exposed to voltage dips. The goal of this paper is to analyse the light intensity variation of various

Yao Q, Fotios S. Effectiveness of an alternative model for establishing mesopic luminance. Lighting Research and Technology 2019; 51(6): 900–909. DOI: 10.1177/1477153518800529

There is a body of research showing how changes in lighting conditions affect hazard detection in the context of driving after dark. There is a separate body of research showing that driving is impaired by distraction. The two have yet to be integrated: this is critical for lighting design recommendations because giving consideration to distraction may affect the optimal conditions established in lighting

In 2018 we published the 50th volume of Lighting Research and Technology. To mark this achievement, issue 50(1) comprised a series of invited articles which focused on several key themes of lighting research, authored by leading researchers in those themes. In the past decade LR&T has increased in extent – both physically (an increase from four to eight issues per year) and geographically (a greater

This paper investigates the technological challenges and solutions to defining a reproducible standard for light together with its measurement, from the 18th to 21st century. The arrival and subsequent need to quantify gas lighting led to development of improved measurement methods, which in turn demanded more reliable standards of light, evolving from candle and flame standards to incandescence, and

This study investigates the significant factors affecting the adoption of light emitting diode lighting among households in Malaysia by conceptualizing and extending the unified theory of acceptance and use of technology through the adaptation of price value and the anticipated emotions of pride and guilt within the model. This study used the partial least squares technique to validate measurements

The disorderly and disrupted movement of passengers within train stations are key concerns in rail transport, especially where there are increasing numbers of passengers, coupled with often out-dated, adapted station spaces. With careful planning and design, different characteristics of lighting can be employed to address problems relating to the movement and behaviour of passengers in railway environments

Design criteria for lighting in subsidiary roads usually include a minimum average horizontal illuminance, widely assumed to be the arithmetic mean illuminance. Analyses of the illuminance distributions over thirty road sections shows that the distributions are not normal and hence the median is more appropriate than the arithmetic mean as a measure of central tendency: the medians are significantly

The visual conditions in an operating theatre/operating room/surgical suite are essential for adequate work performance of clinical staff and absolutely critical for patient safety. It is common that the illuminance level varies greatly across the operating theatre space, causing large luminance contrasts between the centre beam of the surgical luminaire, the lighting in the operating area and the

This paper provides a design method for a light-emitting diode front fog lamp system based on a freeform surface and an improved quadric surface. First, a light-receiving reflector is used to converge the light-emitting diode beam to form an equivalent lighting point. Then, the relationship between the point and the light pattern on the work surface is calculated, and the freeform surface is constructed

Calibration of an illuminance meter is indispensable for accurate measurement of the illuminance of indoor lighting and daylight. In recent years, because of the phasing-out of incandescent lamps and their replacement with LED lamps, it has become difficult to obtain an incandescent type standard lamp to calibrate an illuminance meter. To replace the standard lamp method, we constructed an illuminance

Hospital patients are at risk from infections acquired there. Approximately 1 in 25 patients in the United States contract healthcare-associated infections (HAIs).1 Patients are particularly at risk if the previous patient in that room had an infection.2,3 Standard cleaning procedures usually involve manual application of detergents and disinfectants.4 The efficacy of these manual cleaning procedures

The introduction of solid-state lighting to the marketplace has brought renewed concern about possible adverse consequences of exposure to temporal cyclic or transient variations in lighting system luminous flux, known as temporal light modulation (TLM) (or more commonly referred to as ‘flicker’). TLM may have visual, neurobiological, performance and cognitive effects on viewers.1–3 Visual perception

Many past studies investigating visual performance focused mainly on the effect of luminance contrast between the target and background. Other studies have suggested the importance of colour contrast on visual performance. This pilot study was designed to investigate whether visual performance in the context of road lighting can be improved by enhancing the chroma of targets. Observers were asked to

This study extends previous findings on the effect of different levels of short-wavelength light on human alertness. This study explores the alerting ability of long-wavelength light at two levels (40 lx and 160 lx). Eight subjects took part in the 60-minute experiment for each of two nights, during which their objective alertness and subjective alertness were evaluated using electroencephalogram and

There is considerable focus on technology manufacturing locations and the value in funding innovation when upstream products are not manufactured within a domestic economy. Light-emitting diodes (LEDs) are such an upstream product. Here, we evaluate the value added along the supply chain of luminaires, a product that utilizes LEDs, using bottom-up cost modelling. Coupling the results with analysis

The cubic illuminance concept has long been proposed to indicate light modelling in three-dimensional space. An issue relatively less discussed with regard to its measurement is the potential error due to the finite size of the cube centred at the reference point, yielding a parallax effect. In short, the measured cubic illuminance around a finite-sized object will differ from the designed values that

Twenty-four young adults with myopia in both eyes and no anisometropia participated in this study. Observers were instructed to read one A4-sized page of Chinese text at different levels of illuminance and text contrast, while their reading distance, head tilt angle and reading speed were recorded using an electromagnetic motion tracking system. Four illuminances (3, 30, 300 and 600 lx) and two text

Light's impact on many crop species and vegetables has been deeply studied in recent years but there are still some economic and technical issues to overcome. Thus, the impact of light spectrum and photosynthetic photon flux density from light-emitting diodes on the germination and seedling emergence of Okra has been investigated in this study. Different light treatments have been applied to Okra seeds

Definition of the growth and development characteristics of plants in varied light conditions is a key factor for the creation of highly efficient light facilities for plant cultivation. Experimental research was conducted using an LED irradiation facility with photosynthetic photon flux densities ranging from 0 to 261 μmol m−2 s−1 and a continuous spectrum with maxima at 445 and 600 nm. Under the

Using a calibrated hyperspectral camera, we evaluated the hazard risk level of blue light illumination using the IEC TR 62778:2014 method. The risk levels obtained using the hyperspectral camera were compared with those obtained using the method described in the IEC 62471:2006 guidelines. The IEC TR 62778:2014 risk level of each test product was the same as that obtained using the IEC 62471:2006 method

With the rise of renewable energy systems, there is an increased demand for improved designs of daylighting devices that work without any external energy source to illuminate the deep dark spaces of buildings. Most of the present designs deliver only low light levels especially during the early morning and late evening. This paper focuses on the performance evaluation of specifically designed parabolic-profile

Deliberate temporal modulation (e.g. pulse width modulation) of a light source’s output can be used for predictable control of the intensity and colour of the produced light but can also introduce new problems. Most notably, temporal modulation can lead to unwanted changes in the perception of the environment, called temporal light artefacts (TLA). The two most relevant TLAs for office applications

Architectural lighting has traditionally addressed visual performance and horizontal illuminance on the work plane, later focussing on energy efficiency, while only recently paying particular regard to human health outcomes. The present study evaluated the effectiveness of several light-emitting diode lighting strategies for delivering circadian stimulus to occupants of a typical office space while

In Parts 1 and 2 of this work, an experiment was described in which subjects assessed their visual impressions of scene brightness (B), visual clarity (VC), colour preference (CP) and scene preference (SP) in a real room. In this room, the horizontal illuminance (Ev), the correlated colour temperature (CCT) and the level of chroma enhancement caused by the spectrum of the light source (ΔC*) were changed

Though numerous daylight studies have been conducted worldwide, works for the daylight climate and/or the daylight variations/trends are rare. This gap is treated here. Therefore, the innovative trend analysis and the month–hour diagrams are applied to the illuminance time series at Athens over the period of 1992–2017 under all-/clear-sky conditions. For all skies, the global illuminance shows a broad

Light is considered the most important environmental factor for greenhouse crops, and lack of lighting limits the productivity of greenhouses. Many studies have focused on improving the energy efficiency of lighting in agriculture. In this study, LED lights were mounted in the top, middle and bottom of the plant canopy to provide additional photosynthetically active radiation. Assuming that 100% of

The design method of a double freeform surface lens is being widely applied in non-imaging optical systems. In this paper, a diffuse reflection freeform surface is introduced into the design of a double freeform surface lens. Different from the universal double freeform surface lens, this double freeform surface lens is divided into a small-angle freeform surface and a large-angle diffuse reflection

In this paper an iterative, closed-loop light control scheme is proposed and evaluated by a white light emitting diode-based, daylight-responsive luminaire to follow the time-varying pattern of correlated colour temperature and illuminance of a daylight scene. The proposed control scheme functions primarily with the response signals of two RGB colour sensors, viz., a daylight sensor to monitor the

LED lighting is the most promising lighting technology of the current era because it is highly reliable and energy efficient. The reliability of an LED luminaire is dependent primarily on its junction temperature in operation. Since LED luminaire design differs across manufacturers, a generalised experimental procedure and simplified model is adapted to estimate the junction temperature of an LED luminaire

This paper presents a data analytics model-based predictive control approach for a daylight–artificial light integrated scheme. The essential data are collected from an automated test room with dimmable LED luminaires and motorized Venetian blinds. This study considered machine learning techniques to develop a novel control strategy for all the four-window orientations for maintaining comfort and energy

This is my last Editorial for Lighting Research & Technology because after almost 11 years I am standing down as Editor-in-Chief. After some reflection, I have decided to devote my final editorial to setting out the lessons I have learnt about the world of lighting research over the last decade.

In this work, the correlation between the whiteness of lighting and the preference for the colour of lighting was comprehensively investigated based on four psychophysical studies. Different sets of experimental light sources, two of constant correlated colour temperatures (CCT) and two of different CCTs were adopted to illuminate multiple experimental objects with different illuminance levels (200

In this work, the correlation between the perceived whiteness of lighting and the corresponding colour preference of observers was comprehensively investigated based on the data of 19 groups of experiments collected from 14 studies. The dataset included 13 experiments with constant correlated colour temperature and 6 experiments with multiple correlated colour temperatures, with illuminance levels

This paper presents an experiment on the effect of light on the perception of paintings. The experiment was performed in a test-room where a typical museum exhibition set-up was simulated. Two different paintings were shown to 44 participants, under different light scenes obtained by using tuneable LED (Light Emitting Diode) wallwashers. To set the light scenes, the following parameters were modified:

Lifelines are used to aid self-escape of underground miners, but they are difficult to find in low-visibility conditions of smoke, therefore a self-illuminating lifeline could facilitate miners in locating the lifeline. The detection distance, colour recognition, and miss rate for 10 subjects were determined for red-, green- and blue-lighted diffuse fibre-optic cables, used to create a lighted lifeline

Previous work investigating how lighting enhances peripheral detection for pedestrians has tended to consider only raised hazards and lighting from a directly overhead source. An experiment was conducted to determine the extent to which variations in these parameters would influence the recommendations for optimal lighting. The results did not suggest a difference in the detection of raised and lowered

The popularity of LED-based luminaires has increased enormously in recent years. Every such luminaire consists of several elements including a polymer-based transparent housing, yet some of the ageing aspects of specific luminaire materials have not been investigated. In this paper, we present research aimed at determining the impact of LED lamp powering mode on polymer material deterioration. In the

This paper presents experimental approaches for evaluating concert lighting from the viewpoints of audience members and performers in Cambridge King's College Chapel. We develop image zoning and abstraction techniques to quantify and interpret photometric data acquired under four different electric lighting conditions. Assessed by 78 participants, these lighting scenarios are compared across six different

Rectangular illumination has found extensive application in the field of LED lighting. In this paper, a design method for a combined lens has used the two characteristics of refraction and diffuse reflection for rectangular illumination. The combined lens is composed of a cutting lens and a pedestal. We determined the cutting lens through the shape of the target plane and then applied diffuse reflection

This paper presents the design of a collimator lens for use with the Lightbrick that uses total internal reflection as well as convex and concave surfaces. The Lightbrick is a light collector for the Natural Light Illumination System. The collimator lens is constructed using freeform surfaces which can be calculated through geometric-optics. Verified by optical simulation, using the collimator lens

In a previous study comparing alternative approaches for determining scalar illuminance from cubic illuminance data, the approach using mean spherical semi-cubic illuminances (representing the positive and the negative x-, y-, z-axes) was found to have the highest accuracy. However, this approach, referred to as Approach 2, becomes less accurate as more point sources are introduced into the scene.

This study investigated how light exposure duration affects melatonin suppression, a well-established marker of circadian phase, and whether adolescents (13-18 years) are more sensitive to short-wavelength (blue) light than adults (32-51 years). Twenty-four participants (12 adolescents, 12 adults) were exposed to three lighting conditions during successive 4-h study nights that were separated by at

In addition to stimulating the visual system, light incident on the retina stimulates other biological functions, also referred to as non-visual responses. Among the most notable biological functions are human circadian rhythms, which are bodily rhythms that, in constant darkness, oscillate with a period close to, but typically slightly longer than 24 hours. Twenty-four-hour light-dark patterns incident

Flashing yellow warning lights are important for worker and driver safety in work zones. Current standards for these lights do not address whether and how they should be coordinated to provide course-way information to drivers navigating through work zones. A field study in which the intensities and flash patterns of warning lights along a simulated work zone were varied during daytime and nighttime

Proper lighting plays a critical role in enabling miners to detect hazards when operating a roof bolter, one of the most dangerous mining machines to operate; however, there has not been any lighting research to address the walk-thru type of roof bolter commonly used today. To address this, the Saturn light was designed to directly address walk-thru roof bolter safety by improving trip hazard illumination

The increased use of self-luminous displays, especially in the evening prior to bedtime, has been associated with melatonin suppression, delayed sleep and sleep curtailment. The present study set out to investigate whether the Night Shift application provided by Apple Inc. for use on its portable electronic devices is effective for reducing acute melatonin suppression, a well-established marker of

Light can be used to consolidate sleep in individuals with Alzheimer's disease and related dementias, but the light delivery method is one of the greatest challenges for successful treatment. Based on our field observations, it was hypothesised that a self-luminous light table would be a practical way to deliver light because persons with Alzheimer's disease typically spend a significant amount of

Sleep disorders are problematic for persons with dementia and their family caregivers. This randomized controlled trial with crossover evaluated the effects of an innovative blue-white light therapy on 17 pairs of home-dwelling persons with dementia and their caregivers. Subjects with dementia received blue-white light and control ('red-yellow' light) for six weeks separated by a four-week washout

This paper documents the spectral and spatial performance characteristics of two new versions of the Daysimeter, devices developed and calibrated by the Lighting Research Center to measure and record personal circadian light exposure and activity levels, and compares them to those of the Actiwatch Spectrum (Philips Healthcare). Photometric errors from the Daysimeters and the Actiwatch Spectrum were

A field study was conducted with eighth-grade students to determine the impact of morning light on circadian timing, sleep duration and performance. Before and during school hours for a week in February 2009, half the students studied wore orange glasses that minimized short-wavelength light exposure needed for circadian system stimulation. A control group did not wear the orange glasses. The Daysimeter

Circadian rhythms are biological rhythms that repeat at approximately 24 hours. In humans, circadian rhythms have an average period of 24.2 hours. The 24-hour patterns of light and dark on the retina synchronize circadian rhythms to the local time on earth. Lighting characteristics affecting circadian rhythms are very different than those affecting visual responses. Lack of synchronization between