Direct Glare Research Articles

Visual comfort assessment of daylit and sunlit areas: A longitudinal field survey in classrooms in Kashan, Iran

Visual comfort in schools enhances not only health and wellbeing, but also satisfaction and therefore learning and visual performance. This research aims at testing students’ evaluations on visual comfort through questionnaires in daylit and non-daylit areas in classrooms. Dynamic daylight metrics including Spatial Daylight Autonomy (sDA) and Annual Sunlight Exposure (ASE), codified in LEED v4, are calculated and compared to students’ evaluations. A typical high school in Kashan was selected in which subjective and field measurements were carried out simultaneously in two different oriented (south and north) classrooms during a school year (2014–2015).Simulation results show that 71% of the space in south facing classroom and 20% of the space in north facing classroom receives adequate amount of daylight while 29% of the space in south facing classroom and 0% of it in north facing classroom receives excessive amount of sunlight. According to simulations, each classroom has been divided into daylit and sunlit areas, in which students’ assessments about daylight and sunlight have been separately analyzed based on their position. Comparing simulation and survey results show that while students’ evaluation about daylight availability in daylit areas is mostly positive, daylight uniformity is not considered “enough” in these areas. Moreover, students’ impression about daylight availability in non-daylit areas is rather neutral and more optimistic than simulation results. More interestingly, most students in both sunlit and non-sunlit areas of classrooms do not feel much direct sunlight and glare. In fact, questionnaires’ results show a wider range of sunlight acceptance in south facing classroom and visual comfort in north facing classroom than simulation results. According to the results non-daylit areas or sun-lit areas defined by dynamic metrics would not necessarily cause visual discomfort, suggesting that some other factors (e.g., view, configurations of windows, expectations and region) can change the degree of comfort experienced in each space.

Effect of Direct Glare on Orbicularis Oculi and Trapezius During Computer Reading.

Unfavorable visual conditions during computer work may affect development of both eyestrain and musculoskeletal pain in the neck and shoulder area. The aim of the study was to investigate how direct glare affects symptom development, muscle activity, and muscle blood flow in m. orbicularis oculi and m. trapezius during reading on a computer screen. Fifteen healthy young adults with normal binocular vision read text on a computer screen at an optimized computer workplace, 30 minutes with glare exposure and 30 minutes with appropriate lighting. Postural angles were continuously registered. Development of eye symptoms and musculoskeletal pain in the neck and shoulder area were recorded using VAS scales. Muscle activity and muscle blood flow were measured continuously using electromyography and photoplethysmography, respectively. Glare exposure resulted in significantly more pronounced eye pain, increased orbicularis muscle activity, and increased trapezius blood flow compared to reading with appropriate lighting. There were no significant differences in posture between the two light conditions. There were also significant associations between orbicularis oculi activity and both trapezius blood flow and neck pain during both conditions. Results from the current study show that direct glare conditions cause increased eyestrain and orbicularis oculi contraction during reading on a computer screen. This study also indicates that exposure to direct glare affects the trapezius muscle, possibly by an interaction between the visual system, sympathetic nervous system, and head-stabilizing muscles. In addition, there were associations between the use of orbicularis oculi, trapezius blood flow, and development of neck pain independent of the lighting.

Adjustable task lighting: Field study assesses the benefits in an office environment.

Lighting is a part of every work task in the office environment, yet it is often overlooked. Research links direct and indirect glare to increased risk of visual discomfort among office workers with symptoms ranging from dry eyes to blurry vision or headaches. Researchers have been primarily concerned with those characteristics of task lighting that cause glare including luminance level, position (line of sight), and control. It is unknown what the benefits of adjustable task lights are and whether or not their use has an effect on musculoskeletal comfort or posture. No comprehensive field evaluations of this type were found among peer-reviewed, indexed journals. The purpose of this study was to assess the ergonomic and calculated utility power consumption benefits of adjustable LED task lighting in an office environment using a control/intervention experiment design. One hundred participants were originally recruited and randomly assigned to intervention and control groups. Self-reported data was collected on level of eye fatigue, perception of job content, intervention usability, and musculoskeletal discomfort. Data was also collected on workspace level of illumination and posture during standardized tasks (assessed using RULA). Comparing baseline data to follow-up data for the intervention group, the use of the adjustable, LED task lights provided statistically significant, positive impacts on users' rating of discomfort, eye fatigue, perception of job content, and posture between baseline and the short-term follow up. Significant benefits to musculoskeletal comfort, posture, and visual comfort were documented when participants used the adjustable task lights. Participants' assessments of the light's usability, usefulness and desirability were positive. There were no negative results found with adjustable task light use.

The effect of glare on eye movements when reading

Glare is a very common source of image degradation when performing computer work. Since reading is a task that is very sensitive to image degradation induced disability glare affects reading performance. To assess the effect of different glare conditions on eye movements when reading on a computer screen. Glare conditions have an impact on reading. This observation is based on the results from a study where we investigated how reading eye movements were affected by glare. Sixteen subjects with normal vision participated in this study. In a balanced repeated-measurement study, all subjects performed equal near-vision reading tasks. In addition to the condition of no glare three controlled conditions of glare were used: direct light, indirect light, and desk luminary. The subjects read three texts under each condition: First a short standardized text (IReST), secondly a longer newspaper text, and finally an additional IReST text. The texts were read on a Tobii T120 eye tracker. The results show that glare does have a negative effect on reading performance. The more adverse the lighting condition was, the slower the reading speed became. The decrease was primarily a result of increased fixation durations. Both glare conditions of direct and indirect glare increased the fixation durations significantly (p < 0.05). This study shows that even moderate glare conditions can have an impact on reading. The results show that it is important to follow recommendations of lighting design in computer work environment in order to avoid disability glare.

Corrections for minimizing solar profile prediction errors and methods for preventing direct glare on the workplane in blind control

As a means of improvement of environmental comfort in buildings with blind control, the objective of this study is to minimize solar profile prediction error for the purpose of preventing direct glare caused by the sunlight inlet in blind control. During the process of solar profile prediction, the main variables that cause prediction error of the solar profile were defined and problems from the prediction error were analysed. Surface orientation and time are significant factors that may cause error and glare during blind control. This research proposes and evaluates the correction methods and control strategy to minimize prediction error. In this research, the proposed correction methods and control strategy, which considers the surface orientation based on True North and potential time errors, could solve problems of direct glare caused by daylight inlet on the workplane, according to prediction errors of the solar profile. These methods could also be used to maximize daylight and solar heat gain, because the blocked area on windows could be minimized.

Optimized control algorithm for automated Venetian blind system considering solar profile variation in buildings

Automated blinds need to be controlled to maximize benefits of daylight to enhance occupant comfort and to reduce energy consumption. However, previous control methods focused on minimizing the negative impacts of daylight, but failed to maximize the positive impacts of daylight and solar heat gain. The objective of this study is to develop an optimized control algorithm for automated venetian blind which would reduce the negative effects of incoming daylight on visual comfort of occupants, and to minimize psychological anxieties caused by frequent motions of the blind, by maximizing the positive effects of incoming daylight and solar irradiation, by opening/closing of the blind. Through implementation of the proposed methods and algorithms, the direct glare on work-planes could be prevented at all time, and also incoming daylight and solar irradiation could be increased.

Lighting conditions in sustainable buildings: results of a survey of users’ perceptions

For the last 4 years, the authors have been investigating the performance in practice of a range of sustainable commercial and institutional buildings worldwide. These investigations involved the principal author in one or more visits to each of the buildings and the personal distribution and collection of a questionnaire survey seeking users’ perceptions (on a 7-point scale) of a range of factors: operational, environmental, personal control and satisfaction. For this article, the authors focus on users’ perceptions of the quality of lighting in their work areas. The users’ overall perceptions of lighting conditions are presented and analysed, first with an overview of the average scores for each question, followed by a look at the shapes of their distributions over the set of buildings and then the results of some correlations between lighting overall and a number of other key performance factors such as health, productivity and overall comfort. It was found that lighting overall was one of the higher scoring factors of the environmental category, and the average scores for the amount of natural and artificial lighting were close to the ideal. However, direct glare from the lights and from the sun and sky were noted as issues to be addressed.

잠재적 시간 오차에 따른 현휘의 발생 방지를 위한 최적 블라인드 제어

For the improvement of environmental comfort in the buildings with the blind control, the objective of this study is to prevent the direct glare caused by the daylight inlet. During the process of solar profile prediction, time are significant factors that may cause error and glare during the blind control. This research proposes and evaluates the correction and control method to minimize prediction error. For the local areas with different longitude and local standard meridian, error occurred in the process of the time conversion from local standard time to apparent solar time. In order to correct error in time conversion, apparent solar time should be recalculated after adjusting the day of year and the equation of time. To solve the problems by the potential time errors, control method is suggested to divide the control sections using the calibrated fitting-curve and this method is verified through simulations. The proposed correction and control method, which considered potential time errors by loop lop leap years, could solve the problems about direct glare caused by daylight inlet on the work-plane according to the prediction errors of solar profile. And also these methods could maximize daylight inlet and solar heat gain, because the blocked area on windows could be minimized.

작업면 현휘 방지와 주광 및 일사 유입 최대화를 위한 제어 종료 영역에서의 최적 블라인드 제어

The objective of this study is to develop the blind control strategy and method which reduce negative effect of incoming daylight on visual comfort of occupants, minimize psychological anxieties caused by frequent motions of a blind, and maximize positive effect of incoming daylight and solar irradiation by opening/closing of a blind. As previous researches on blind controls have limited outdoor environmental conditions to those in specific regions, orientations and dates, these resulted in problems at various conditions for general-purpose application. Major problem is that the time interval and amount of blind movement do not meet the control objective at the end of control zone and discontinuous curve. To overcome these limitations revealed in the previous researches, following tasks were performed in this study. 1) To establish the control objective to accomplish the goal of this study. 2) To develop the control methods and algorithms which prevent glare on the work-plane at any time and which control the time interval and amount of blind movement to follow the control objective at various profile angle curves. 3) To validate the general-purpose applicability and performance of the developed control methods and algorithms by simulation and its data analysis at various conditions. It was found that the proposed methods and algorithms can prevent the direct glare on the work-plane at all the time and also increase the incoming daylight and solar irradiation.

Illuminance-based slat angle selection model for automated control of split blinds

Venetian blinds play an important role in controlling daylight in buildings. Automated blinds overcome some limitations of manual blinds; however, the existing automated systems mainly control the direct solar radiation and glare and cannot be used for controlling innovative blind systems such as split blinds. This research developed an Illuminance-based Slat Angle Selection (ISAS) model that predicts the optimum slat angles of split blinds to achieve the designed indoor illuminance. The model was constructed based on a series of multi-layer feed-forward artificial neural networks (ANNs). The illuminance values at the sensor points used to develop the ANNs were obtained by the software EnergyPlus™. The weather determinants (such as horizontal illuminance and sun angles) were used as the input variables for the ANNs. The illuminance level at a sensor point was the output variable for the ANNs. The ISAS model was validated by evaluating the errors in the calculation of the: 1) illuminance and 2) optimum slat angles. The validation results showed that the power of the ISAS model to predict illuminance was 94.7% while its power to calculate the optimum slat angles was 98.5%. For about 90% of time in the year, the illuminance percentage errors were less than 10%, and the percentage errors in calculating the optimum slat angles were less than 5%. This research offers a new approach for the automated control of split blinds and a guide for future research to utilize the adaptive nature of ANNs to develop a more practical and applicable blind control system.

A comparison of Mesua ferrea L. and Hura crepitans L. for shade creation and radiation modification in improving thermal comfort

Open spaces in tropical climates are highly exposed to solar radiation. These conditions will influence the outdoor energy budget, leading to an increased heat island effect and reduced human thermal comfort. Trees, however, can influence the microclimate through radiation control that indirectly reduces direct radiation uptake and glare by humans and buildings. This condition affects building energy budget and human thermal comfort. This study compares the effectiveness of Mesua ferrea L. and Hura crepitans L. in shade creation and radiation modification in improving human thermal comfort. The study employed two methods: (i) a field measurement procedure and (ii) a computer-based sun-shading analysis using ECOTECT. The results from this study indicate that both M. ferrea L. and H. crepitans L. contribute significantly to direct thermal radiation modification below their canopies. The average solar filtration under the tree canopy for M. ferrea L. was 93%, with 5% canopy transmissivity, 6.1% of leaf area index (LAI) and 35% of shade area. For H. crepitans L. the average heat filtration under the canopy was 79%, with transmissivity of 22%, LAI of 1.5 and 52% of shade area. Thus, the study found that M. ferrea L. was more significant as a thermal radiation filter than H. crepitans L., due to the former's denser foliage cover and branching habit. This significant filtration capability contributes to reduce more terrestrial radiation, cooling the ground surfaces by promoting more latent heat, reducing air temperature by promoting more evapotranspiration and effectively improves outdoor thermal comfort in tropical open spaces.

Automated blind control to maximize the benefits of daylight in buildings

Venetian blinds are a common type of shading device and are increasingly operated automatically to overcome the limitations of manual operation. Automated blinds need to be controlled to maximize benefits of daylight in the point of occupant comfort and energy consumption. However, the previous control methods are focused on minimizing negative impacts of daylight, so they might fail to maximize positive impacts of daylight. They may often overpredict a blind's position, resulting in the undesirable blockage of daylight. In this paper, we propose a new control method for automated venetian blinds to maximize occupant comfort. The proposed control method can not only protect occupants from direct solar glare but also maximize daylight penetration into buildings based on occupants' preferences on daylight. The proposed control method is designed to allow the occupants to define the zone they want protected from direct sunlight. It can control the blinds to protect only the defined zone; therefore, more daylight can be introduced to the other areas, excluding the predetermined zone. A control method for the case of one blind with one zone was developed and then extended for the case of multiple blinds with multiple zones.

Evaluation of visibility of tinted helmet visors for motorcycle riders

Abstract This study investigates the effect of tinted helmet visors on visibility through objective experiments and subjective evaluation by an on-road test. The method of limits is employed in the experiments. The main dependent variable is the degree of visibility of a Landolt C ring. In the subjective evaluation, the subjects fill out questionnaires to rate traffic evaluation items on five-point Likert scales. The main findings from the study can be summarized as follows: (1) the visibility performance of a transparent helmet visor is superior to that of tinted helmet visors, (2) tinted helmet visors are ineffective in reducing direct glare and also affect visibility performance, (3) the results of the subjective evaluation demonstrate that tinted helmet visors affect the rider's visibility (however, yellow visors do not significantly affect visibility, particularly at night), and finally, (4) this study proposes an optimal tinted helmet visor for motorcycle riders that is effective in avoiding reduction of visibility performance. Relevance to industry These findings can improve the safety of helmets and reduce the risk of traffic accidents for motorcycle riders. This study can also help manufacturers to develop more effective and safer helmets.

Adding advanced behavioural models in whole building energy simulation: A study on the total energy impact of manual and automated lighting control

Behavioural models derived from on-going field studies can provide the basis for predicting personal action taken to adjust lighting levels, remedy direct glare, and save energy in response to physical conditions. Enabling these behavioural models in advanced lighting simulation programs, such as DAYSIM and the Lightswitch Wizard, allows for a more realistic estimate of lighting use under dynamic conditions. The current downside of these approaches is that the whole building energy impact of manual changes in blind settings and lighting use, including its effect on heating and cooling requirements, is not considered. A sub-hourly occupancy-based control model (SHOCC), which enables advanced behavioural models within whole building energy simulation, is presented. The considered behavioural models are the Lightswitch2002 algorithms for manual and automated light and blind control, while the investigated whole building energy simulation program is ESP-r. The enhanced functionality is demonstrated through annual energy simulations aiming at quantifying the total energy impact of manual control over lights and window blinds. Results show that building occupants that actively seek daylighting rather than systematically relying on artificial lighting can reduce overall primary energy expenditure by more than 40%, when compared to occupants who rely on constant artificial lighting. This underlines the importance of defining suitable reference cases for benchmarking the performance of automated lighting controls. Results also show that, depending on the proportion of buildings occupants that actively seek out daylighting, reduced lighting use through automated control may not always produce anticipated savings in primary energy for indoor climate control. In some cases, reduced lighting use is shown to even increase primary energy expenditure for indoor climate control, trimming down initial primary energy savings in lighting alone. This reveals the superiority of integrated design approaches over simpler daylighting guidelines or rules of thumb.

An Acoustic Tag for Recording Directional Pulsed Ultrasounds Aimed at Free-Swimming Bottlenose Dolphins (&lt;I&gt;Tursiops truncatus&lt;/I&gt;) by Conspecifics

The ability of dolphins to produce pulse sounds with a bandwidth of up to 150 kHz, has been intensively studied with focus on their sonar capabilities, i.e. the detection, ranging and discrimination of objects of various shapes, textures and material. The sonar pulses have been found to be directional, with a -3db beam width of about 10 degrees in both the vertical and the horizontal plane, and with the beam axis ea. 5 degrees above that of the rostrum. Pulse sounds also frequently occur in social situations (Paper I), but studies of these sounds traditionally have been limited to their audio band, omni-directional components. Hypothesising that social pulse sounds in bottlenose dolphins (Tursiops truncatus) also were directional, early recordings within this study were done across a net barrier, in a narrow channel connecting two pools, to increase the probability to record such sounds with a fixed hydrophone. These recordings confirmed the presence of ultrasonic frequencies in pulse sounds emitted in aggressive interactions, where the interacting animals were oriented face-to-face on either side of the net barrier. There were also indications that they were directional (Paper I). These sounds also had a pronounced energy peak 1 sec), labelled Machine-gun sound, occurred frequently in the initial phase of the aggressive interactions. While emitting this sound, the animal kept its rostrum, and possibly the sound beam axis aimed at the agonist, suggesting that it was deliberately used to expose the opponent to powerful broadband pulse sounds, probably to provoke a fight (Paper III).To avoid the restrictions on the behaviour imposed on the dolphins by the net barrier setup, an acoustic tag system was developed (Paper II). The tag was attached to the receiving dolphin instead of the transmitter, and made it possible to study the use of the directionality of the pulse sounds in social contexts, while the interacting dolphins were fully free-swimming. The tag, based on click detectors, recorded the envelope of pulses within two narrow band pass frequency filters, centred on 70kHz and 120kHz, respectively (Paper II). The tag recordings verified the presence of energy within both filter frequency bands in social pulse sounds, in particular in aggressive interactions (Paper III). This thesis suggests that thedirectionality of such pulse sounds is used intentionally to address social signals to a specific individual, or group of individuals. The relatively loud omni-directional audio band component will facilitate for nearby conspecifics to monitor the progress of the interaction. It will also make the signal clearly audible to the opponents throughout an interaction, even if they may be tumbling around, being unable to keep the sound beam axis aimed at the other. Similar pulse bursts were recorded in association with what was interpreted as play-fight, between subadults and juveniles (Paper IV). However, unlike the real aggressive bursts, these bursts had a trailing FM whistle, and this combined signal is suggested to be an appeasement signal, analogous with the laugh and giggle observed in apes. It is supposed to prevent play-fights from escalating into physical and potentially dangerous real fights. It was never recorded in true aggressive interactions among adults.There were individual differences between the animals in amount of received directional pulse sounds while carrying the tag (Paper III). The socially most active of the females, having an intermediate position in the dominance hierarchy, received significantly more directional pulse sounds than the other, socially less active, but higher ranked female. The breeding male received the least number of pulse sounds. This lends support to the presence of echolocation manners, as suggested by Johnson and Norris (1994), making it socially unacceptable to aiming the sonar beam towards conspecifics unless the intention is to conveying a social message.Dolphins lack the facial plasticity playing a dominant role in the social life of many terrestrial mammals, e.g. primates, canids and felids. This directional signal modality is used to express internal emotions and can be addressed to selected individuals, further stressed by a direct glare. Dolphins completely lack such a facial plasticity but most likely not the need for expressing emotions. This thesis suggests that in dolphins the facial expressions may have been replaced bydirectional pulse sounds. The facial expressions in e.g., wolves, is supposed to be the result of a mixture of dominance/aggression vs. submission/fear emotions. We propose that the pulse sounds, seen in the aggressive interactions, reflect a similar mix of feelings. Obvious parameters in such a graded social signal system are pulse repetition rate, amplitude, duration and power spectrum. To study this further a broadband acoustic tag, preferably attached to several animals simultaneously, is required.

Field measurements of direct and rearview-mirror glare from low-beam headlamps

This study measured direct and rearview-mirror glare illuminances produced by low-beam headlamps in a sample of 22 passenger vehicles. The glare illuminances were measured for 12 common glare situations that were defined by a full factorial combination of three scenarios (oncoming driver, center rearview mirror of a preceding driver, or driver-side mirror of a preceding driver one lane to the right), two longitudinal distances (25 m or 50 m), and two vertical locations (illuminated vehicle being either a car or a light truck/van/sport utility vehicle). The measurements were made outdoors at night on asphalt pavement. The median illuminances (not taking into account window transmittance or mirror reflectance) ranged from 0.5 lux for an oncoming driver of a light truck/van/sport utility vehicle at a distance of 50 m, to 3.4 lux at the driver-side mirror of a preceding car at 25 m one lane to the right. The ratios of the maxima and the minima measured for each of the 12 glare situations were large, ranging from about 5:1 to 36:1. The median actual illuminances were compared to the median expected illuminances based on a recent, laboratory-measured, representative sample of US low-beam patterns, taking into account the possible effects of dirt, voltage, misaim, and pavement reflectance. This analysis indicates that the actual illuminances could be very well modeled using the laboratory-measured beam patterns and assuming a linear relationship between the light output of clean and dirty headlamps. Additional analyses evaluated the relationships between headlamp mounting height and glare illuminance.

Comment on ‘Field measurements of direct and rearview-mirror glare from low-beam headlamps’ by M Sivak, MJ Flannagan, B Schoettle and Y Nakata

Comment on ‘Field measurements of direct and rearview-mirror glare from low-beam headlamps’ by M Sivak, MJ Flannagan, B Schoettle and Y Nakata

Summertime performance of an automated lighting and blinds control system

An innovative automated blind and lighting control system was developed to eliminate direct solar penetration and keep working plane illuminances within an optimal range, while making maximum use of daylight, and minimizing blind movement. Data collected from a controlled experiment indicate that the system eliminated direct solar glare and kept the working plane illuminance within the target range, while providing only 30% more electric lighting than a theoretical system with no blinds and perfect knowledge of the working plane illuminance. The system needed to provide 60% less electric lighting than a similar system with switchable rather than dimmable luminaires. Total blind movement varied from less than 1 min to over 6 min in one day depending on the weather, with an average of 190 s. Similar integrated systems have the potential to save a large fraction of the electricity used for lighting, while providing an amenable visual environment.

Roof lighting and sun protection

On the basis of a radiation model of the sky and direct sunlight, glare and heat loads can be calculated for different roof light systems. To avoid overheating, a maximum daily energy input through roof lights of 0.65 kWh per square metre of floor area is suggested, whereas the glare limit is set by a maximum luminance of 6000 cd/m 2. With these criteria the efficiency of various roof light systems is evaluated in terms of annual hours of daylight use with a set minimum for the interior illuminance. Actual energy savings with roof lighting depend on the required lighting level and on the switching scheme for the electric lighting.

Orientation of giant tortoises, Geochelone gigantea (Schweigger) while grazing on Aldabra Atoll

AbstractThe Aldabran giant tortoise is one of the few testudines that feeds in dense herds, and in so doing the animals frequently exhibit a conspicuous orientation away from the sun. This orientation is most marked when ambient temperature is high, and it breaks down when the tortoises are shielded from direct sunlight. It was previously hypothesized that negative heliotaxis is related to thermoregulation-to reduce heat inflow to the exposed anterior appendages and instead expose the protected posterior of the shell. There has been no test of the thermoregulatory function, and pilot experiments indicate that orientation away form the sun occurs to reduce direct glare into the tortoise's eyes. The glare of the sun seems to interfere with accurately oriented biting movements and reduce feeding efficiency. Speed and intensity of reaction to solar glare is inversely related to the animal's body size. The possibility of a thermoregulatory component to the away-from-the-sun orientation cannot be discounted, but it must be investigated directly.