Assessing and Modeling Discomfort Glare for Raw White LEDs with Different Patterns

In 5G, indoor visible light communication is going to use panel of white light emitting diodes (LED) to provide high-speed communication as well as illumination. In this system, it is important to maintain uniform illuminance as non-uniformity creates bright and dark spots, which may cause discomfort for the occupants. The uniform illuminance depends upon the position and semi-angle of radiation associated with the LED panel. The objective is to optimize the position of the LED panels so that the received power and SNR at all locations in the room are uniform. The optimization task is carried out using a new metaheuristics whale optimization algorithm. Simulation study is performed in a room with dimension 5 × 5 × 3 m, having 4 to 6 LED panels (each with 60 × 60 LEDs). Results reveal that the proposed approach obtained superior uniformity (received power and SNR achieved in dB) compared to that achieved by particle swarm optimization.

Building simulation results are frequently expressed in terms of the computed values of various performance indicators. Specifically, simulations of visual conditions in buildings yield estimated values of performance indictors such as illuminance levels and daylight factors (at specific points, or averaged over a reference plane) or glare-related indices such as UGR (Unified Glare Rating). Aside from visual performance simulation, such visual performance indicators may be also used in buildings' energy simulation as virtual sensors that feed into control algorithms for operation of luminaires and shades. As such, it is important to examine the fitness and dependability of these kinds of performance indicators and their utility in the building performance simulation process on a regular basis. In this context, the present contribution presents a case study focused on UGR, an occupant-centric performance indicator, which is meant to express the level of visual discomfort experienced by people exposed to the presence of bright light sources in the field of view. This case study address issues of calculation, measurement, and occupants' evaluation. Embedded routines for the calculation of UGR in simulation applications require information (computed in a previous step) on the background luminance, the luminance of luminaires present in the observer's field of view, the solid angles extended from the observer's eye to the luminaire weighted according to their relative position to the line of sight. Actual UGR values in a given spatial setting can be obtained using luminance meters or specially calibrated cameras. Moreover, empirical studies have established relationships between measured UGR values at a reference point of view and the human observers' evaluation of glare discomfort using standardized Likert-type scales. The present case study entails the results of calculations and measurements of UGR as well as corresponding subjective evaluations of visual discomfort levels in an office space. The results provide, for the specific setting examined, answers to the following questions: Do the UGR measurements agree with prior calculated values? Are observers' judgment of the discomfort level caused by glare agree with the relevant reference information in literature and standards? Specifically, the findings regarding the difference a) between calculation and measurement results on the one side and b) between standard-based predictions of subjective evaluations on the other side provide insights into the dependability of simulation-based UGR estimations as the basis for the evaluation of visual comfort in indoor environments.

Recently, there has been increased interest in energy-efficient lighting as energy resources become higher in demand. Anecdotal evidence suggests that certain populations believe light-emitting diodes (LED) produce more glare than traditional technologies. This may be due to a number of factors such as spectral power distribution (SPD), source luminance, or beam intensity distribution. A study was conducted to assess the effect of different SPDs on the perception of discomfort glare from an LED source. For the range of conditions evaluated, the presence of any luminous surround significantly reduced the perception of discomfort glare from the LED array. The blue luminous surround reduced discomfort glare perception significantly less than the white or the yellow luminous surrounds. The implications for solid-state lighting systems are discussed.

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 freely adjust their position and view in order to minimise the effect of glare. The spatial and directional extents of the adaptive zone depend on furniture layout and the freedom of occupants’ tasks. 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%.

It is well established that there are two main aspects to glare, the visual impairment and the discomfort, known as disability and discomfort glare, respectively. In contrast to the case of disability glare we understand very little about the underlying mechanisms or physiology of discomfort glare. This study attempts to elucidate the neural mechanisms involved using fMRI and glare sources with controlled levels of retinal illuminance. Prior to carrying out the fMRI experiment, we determined each participant's discomfort glare threshold. The participants were then divided into two groups of equal size based on their ranked sensitivity to discomfort glare, a low and high sensitivity group. In the fMRI experiment each participant was presented with three levels of glare intensity whilst simultaneously required to carry out a simple behavioral task. We compared BOLD responses between the two groups and found that the group more sensitive to glare had an increased response that was localized at three discrete, bilateral cortical locations: one in the cunei, one in the lingual gyri and one in the superior parietal lobules. This increased response was present for all light levels tested, whether or not they were intense enough to cause discomfort glare. Based on the results, we present the case that discomfort glare may be a response to hyperexcitability or saturation of visual neurons.

자연채광은 건물 재실자에게 시각적 편안함과 쾌적함을 제공하여 건강성을 향상시키며 조명 에너지를 절약할 수 있는 중요한 조명환경 요소이다. 자연광에 의해 발생되는 창면에서의 글레어는 장시간 노출될 시 시각의 저하, 시각적 불쾌감의 원인이 된다. 창면에 의한 불쾌글레어 평가시에는 창면에서 글레어 광원을 어떻게 선별할 것인가가 중요한 문제이다. 기존의 불쾌글레어 평가법을 적용하더라도 글레어 광원을 한정할 방법이 없다. 따라서 본 연구에 서는 글레어 광원 선별방법을 모색하기 위하여 불균일한 대광원의 휘도차가 불쾌글레어감에 미치는 영향을 검토하였다. 이를 위하여 120×120[㎝]의 정사각형 모형창을 제작하였다. 실험변수는 균일과 불균일한 휘도분포의 광원의 휘도비와 광원크기로 선정하였다. 실험방법은 모형창을 3분할한 후, 각기 다른 휘도비를 설정하여, 1[m] 1.5[m], 3[m] 거리에서 불쾌글레어를 평가하도록 하였다. 실험 결과 두 개의 결론을 얻었다. 첫째, 광원의 평균휘도가 증가 할수록 불쾌글레어 평가값이 증가하였으며, 둘째 창면 상부의 천공 부분만을 글레어 광원으로 볼 수 없으며 하부 면도 불쾌글레어 평가에 영향을 주는 것으로 나타났다. 본 연구의 결과는 채광창으로부터의 불쾌글레어 평가 시 글레어 광원을 선택하는 기준으로 활용될 수 있을 것이다.

Glare from very small sources is grossly overrated by the UGR (Unified Glare Rating) formula. Experiments were carried out on glare from small sources at interior lighting distances. Results varied widely but were of adequate statistical accuracy. They showed that a small glare source is characterised by a constant projected area of 0.005 m2, not a constant solid angle; that glare from a source below 0.005 m2 is determined by its intensity, not by its luminance; and that the UGR formula is applicable to small sources if it is suitable modified (L2ω becomes 200I 2/R2).

Light-emitting diodes (LEDs) are used widely for their high luminous efficiency and durability. We developed a novel prototype high definition endoscope with white LEDs and evaluated the image quality it produced against a commercial endoscope with conventional light source. The specifications of both colonoscopes were identical, except for the LED light source at the tip of the prototype. We examined 20 patients with rectal or sigmoid colon lesions and the image quality was evaluated in 40 images (one image from the LED colonoscope and one from the conventional colonoscope for each lesion) by three endoscopists. We additionally evaluated the 17 videos recorded with the LED colonoscope that were available. Image quality, mucosal and vascular color, and luminous distribution and intensity were scored on a 5-point scale. The mean score for vascular color given by one evaluator was significantly higher using the LED colonoscope than using the conventional colonoscope. The mean scores for mucosal color and luminous intensity from another evaluator were significantly lower with the LED colonoscope than with the conventional colonoscope. There were no significant differences in the luminous distribution scores for any of the evaluators. The image quality of the videos was evaluated as being similar with both colonoscopes. Image quality from the LED and conventional colonoscopes were similar, although the luminous intensity of the LEDs is inferior to that of the conventional light source at the present time.

Light emitting diodes (LED) are a new source for replacing traditional light sources including under water illumination. As traditional underwater light sources operate under a radiative transfer model, the luminous intensity is dispersed evenly at each emission angle, with the scattering factors included in the attenuation coefficient. By contrast, LED light sources are characterized by being highly directional, causing underwater luminous energy to vary with different emission angles. Thus, the traditional theory of underwater optical transfer becomes inapplicable when an underwater LED lighting module is designed. Therefore, to construct an underwater transfer model for LED light sources, this study employed the average cosine of the underwater light field, the method for light scattering probability, the LED luminous intensity distribution curve (LIDC) and axial luminous intensity. Afterwards, an underwater LED fish-attracting lamp was designed. Experimental results showed that, compared with the simulation values, the luminous intensity of the underwater LED lighting module at all emission angles had a percentage error of less than 10%.

A prediction method to identify the glare source in a window with non-uniform luminance distribution

A state of the art pilot-scale plant-factory, planned for research, was constructed at Tamagawa University in Tokyo, Japan. The full research facility, named Future Science Technology Center, has been operational since March 2010. The plant-factory facility is housed on the first floor of the research center. In this presentation, the plant factory facility design will be discussed as well as the facilities’ planned utilization of artificial lighting sources, such as Light-emitting Diodes (LEDs), Hybrid Electrode Fluorescent Lamps (HEFLs) and cool white fluorescent (CWF) lamps for plant production. The main component of the artificial lighting source is liquid cooled Chip on Board (COB) high intensity LED panels. The COB utilizes AlGaInP/GaP-based LEDs with a peak wavelength of 660 nm. Various COB and Package on Board (POB) LED panel designs were tested prior to the construction of the facility.

In the CIE TC3-13 meeting in 1993, the unified glare rating (UGR) proposed by K. S φresen was approved for adoption in the TC report. In Japan, the “G-Classification” which classifies luminaires based on the CIE Glare Safeguard System, has been used. Therefore, it is important to clarify the relationship between the “G-Classification” and UGR. This paper analyzes the relationship between them using calculations for nine typical luminaires and establishes that there is a clear relationship between them.However, UGR has a significant problem. It was developed based not on observations, but on calculations that merely simplify and make more consistent the previous glare evaluation methods. Thus there is no observation data to proveits accuracy. The second part of this paper presents studies done to clarify the relationship between the subjective appraisals of discomfort glare and UGR. Using a full-scale office model where various lighting conditions could be presented, the degree of discomfort glare was evaluated by many observers, and the relationship between the evaluations and the calculated UGR was analyzed. The results show that although there is a certain relationship between them, the degree of discomfort glare obtained by the subjective appraisal is lower than the value calculated for UGR.

Nowadays, discomfort glare indices are frequently calculated by using evalglare. Due to the lack of knowledge on the implications of the methods and parameters of evalglare, the default settings are often used. But wrong parameter settings can lead to inappropriate glare source detection and therefore to invalid glare indices calculations and erroneous glare classifications. For that reason, this study aims to assess the influence of several glare source detection methods and parameters on the accuracy of discomfort glare prediction for daylight. This analysis uses two datasets, representative of the two types of discomfort glare: saturation and contrast glare. By computing three different statistical indicators to describe the accuracy of discomfort glare prediction, 63 different settings are compared. The results suggest that the choice of an evalglare method should be done when considering the type of glare that is most likely to occur in the visual scene: the task area method should be preferred for contrast glare scenes, and the threshold method for saturation glare scenes. The parameters that should be favored or avoided are also discussed, although a deeper understanding of the discomfort glare mechanism and a clear definition of a glare source would be necessary to reliably interpret these results.

Discomfort glare metrics typically consider at least one of the two effects of discomfort glare - saturation and contrast - in their equation. The former occurs when there is an excessively bright glare source in the field of view, while the latter occurs when there is a high luminance ratio between the glare source and the adaptation level of the eye. We hypothesize that the contrast effect may dominate in low-light scenarios such as those commonly found in open-plan offices. Thus, we designed and carried out a user study in controlled laboratory conditions with 63 participants with a total of 252 scenes to investigate discomfort glare evaluations in dim daylight office environments with low adaptation levels. Our preliminary findings support our hypothesis that contrast-driven metrics predict glare responses in a more reliable way than hybrid metrics at low adaptation levels where the contrast effect dominates, which underlines the need for refining glare metrics in low brightness conditions.

The aim of the experiment was to assess the effects of supplemental lighting of cucumber grown in greenhouse using lamps with differentiated light spectra: sodium lamps – high-pressure sodium (HPS) and light emitting diodes (LEDs). Plants (cucumber ‘Pacto’ F 1 ) were grown in two greenhouse compartments with five light treatments: I – HPS + LED (top light with HPS LEDs as interlighting), II – only HPS as top light, III – LED R (LED chips on board (COB) type with an increased level of red band), IV – LED W (LED COB type, white), V – LED B (LED COB type with an increased level of blue spectrum). Light treatments: HPS + LEDs and HPS were grown in one greenhouse compartment and the other three light treatments: LED R (red light supplementation), LED W (without additional supplementation) and LED B (red spectrum supplementation) in the second compartment in analogous climatic conditions. The LED lamps using COB technology are known to be a very efficient source of light. Plants were cultivated from December 2018 to March 2019 in mineral wool slabs Grotop Master (100 × 15 × 10) with four plants on one mat. They were illuminated for 18 h (from 5 am to 11 pm), setting the threshold value (on and off) at 130 W. The plants were drip-irrigated with a complete nutrient solution. The irrigation was controlled based on a weighting system. The assessment of the effect of lighting on early yield and quality of cucumbers was completed after 8 weeks of cropping. It was shown that it was possible to obtain 3.59 kg from one plant during the 8-week period of evaluation by illuminating plants with sodium lamps (HPS), while using HPS and LEDs as additional illuminated inter-rows 3.89 kg. The yield of plants illuminated by LED lamps varied depending on the variant of the spectrum used and was respective for LED R, LED W and LED B, 3.30 kg, 3.90 kg and 3.25 kg. The obtained results indicated that the yield of cucumber ‘Pacto’ F 1 grown with HPS lamps at top lighting and at the same time using interlighting with LED lamps was similar to LED W lamps (i.e. without additional supplementation in the range of red (LED R) and blue (LED B) light). Due to good results of LED lamps (type COB for top lighting or as interlighting) used for the cucumber supplemental lighting and high energy efficiency of LEDs, the promising future for that type of lamps compared with traditionally used HPS during winter cultivation in a greenhouse was demonstrated.