Terms Of Visual Comfort Research Articles

Effect of LED Light Frequency on an Object in Terms of Visual Comfort

Light emitting diodes (LEDs) play an essential role in lighting, and green earth activities because of their high efficiency, longevity, and reduction of carbon dioxide emissions during illumination. However, the brightness level of LED light sources must be adjusted appropriately for the backlight source or illumination; therefore, pulse amplitude modulation (PWM) is a commonly used method of LED control. This article experimentally investigated human interaction with the visual comfort effect of the light obtained using different PWM frequencies on an object in a sensor-based intelligent lighting system. Critical light frequencies are vital for the eye to distinguish light stimuli according to time. Histograms of the object were created according to the light frequency, and the results are discussed. The eye’s response to light frequencies changing over time is important for visual comfort, and examining light frequencies in the range of 25–250 Hz was sufficient to conclude the study. It has been experimentally shown that light frequencies around 160 Hz, and above this value provide visual comfort.

Energy efficiency, visual comfort, and thermal comfort of suspended particle device smart windows in a residential building: A full-scale experimental study

Smart window controls the visible light transmittance and solar heat gain coefficient through the transition to a clear or tint state. When applied in buildings, it can be an effective solution in terms of visual and thermal environment by controlling solar radiation. Various previous studies have provided smart windows’ effective performance results related to the visual or thermal environment, however, these studies were mostly based on numerical simulations or small-scale test cells. Few studies have comprehensively analyzed smart windows’ performance when applied to real buildings. Accordingly, this study aimed to analyze and evaluate the performance of smart windows applied in residential buildings related to the visual and thermal environments from various perspectives. For this purpose, we installed suspended particle device smart windows in an apartment building, i.e., a typical residential building type in South Korea, set up related sensors and equipment and collected data from July to September 2022. Based on this campaign, we evaluated visual and thermal comfort and lighting and cooling energy performance according to the sky condition (cloudy, partly cloudy, and clear days) and smart window tinting control method (always tinting, automatic control to maintain the indoor daylight illuminance at 200 lx, and automatic control to maintain the illuminance at 400 lx). In terms of glare, on partly cloudy and clear days, smart windows effectively controlled glare regardless of the tinting control method. In terms of the indoor daylight illuminance, automated control was more effective than always tinting in terms of providing useful daylight under all sky conditions. In terms of thermal comfort, tinting at all times was the most effective on partly cloudy and clear days. The lighting energy consumption increased by 3.9–17.9% when smart windows were used, while the cooling energy consumption was reduced by 0.0–20.5%. Overall, this study revealed that the appropriate smart window operation method varied depending on the sky condition. On cloudy day, maintenance of the indoor daylight illuminance at 200 lx using automated control was efficient. On partly cloudy and clear day, the automated control (200 lx or 400 lx) was efficient in terms of visual comfort, however, in terms of thermal comfort and energy consumption, tinting at all times was effective. This suggested that completely tinting smart window in conjunction with automatic artificial lighting control to ensure proper indoor illuminance could be the most effective on a partly cloudy day and a clear day. Based on this study, it is necessary to derive more detailed optimal smart window operation strategies in terms of glare, indoor daylight illuminance, thermal comfort, and energy consumption for all seasons.

Energy and daylighting performance of building integrated spirooxazine photochromic films

The study of chromogenic materials and systems is particularly promising for innovative, transparent building envelopes, with thermo-optical properties adaptable to surrounding environmental conditions. This work spots light on the multiple effects of photochromic glazing on the energy consumption of buildings and on the impact that such technologies would have on the visual comfort of occupants. To our knowledge, this is the first work dealing with building integration of spirooxazine-based photochromic films. This experimental and theoretical work aims helping to fill this gap by reporting the results of a study concerning the spirooxazine photochromic molecules, integrated in transparent matrices of polymethylmethacrylate. This work discloses the potential of specific photochromic materials, especially as a function of spectral peculiarities. The figures of merit of this technology have been studied by assuming its integration in an ideal multi-storey office building, and by studying the effects in terms of energy consumption and visual comfort and proposing a comparison with several static commercial glazing technologies. The photochromic glazing demonstrated to offer significant reduction of energy use for cooling, compared to a clear glass (with yearly saving of 4079 kWh, on the Southern facade), and for artificial lighting (with a saving of 3711 kWh), if compared to the commercial solar control glazing. Furthermore, the dynamic behaviour of the photochromic glazing represented the best choice in terms of visual comfort.

Influences of Spectral Power Distribution on Circadian Energy, Visual Comfort and Work Performance

Spectral power distribution (SPD) is an essential element that has considerable implications on circadian energy and the perception of lit environments. The present study assessed the potential influences of SPD on energy consumption (i.e., considering circadian energy), visual comfort, work performance and mood. Two lighting conditions based on light-emitting diode (LED) and organic light-emitting diode (OLED) were used as proxies for SPDs of different spectral content: dominant peak wavelength of 455 nm (LED) and 618 nm (OLED). Using measured photometric values, the circadian light (CL), melatonin suppression (MS), and circadian efficacy (CE) of the two lighting sources were estimated via a circadian-phototransduction model and compared. Additionally, twenty-six participants were asked to evaluate the said lit environments subjectively in terms of visual comfort and self-reported work performance. Regarding circadian lighting and the associated energy implications, the LED light source induced higher biological actions with relatively less energy than the OLED light source. For visual comfort, OLED lighting-based conditions were preferred to LED lighting-based conditions, while the opposite was true when considering work performance and mood. The current study adds to the on-going debate regarding human-centric lighting, particularly considering the role of SPD in energy-efficient and circadian lighting practices.

SSVEP phase synchronies and propagation during repetitive visual stimulation at high frequencies

Steady-state visual evoked potentials (SSVEPs), the brain response to visual flicker stimulation, have proven beneficial in both research and clinical applications. Despite the practical advantages of stimulation at high frequencies in terms of visual comfort and safety, high frequency-SSVEPs have not received enough attention and little is known about the mechanisms behind their generation and propagation in time and space. In this study, we investigated the origin and propagation of SSVEPs in the gamma frequency band (40–60 Hz) by studying the dynamic properties of EEG in 32 subjects. Using low-resolution brain electromagnetic tomography (sLORETA) we identified the cortical sources involved in SSVEP generation in that frequency range to be in the primary visual cortex, Brodmann areas 17, 18 and 19 with minor contribution from sources in central and frontal sites. We investigated the SSVEP propagation as measured on the scalp in the framework of the existing theories regarding the neurophysiological mechanism through which the SSVEP spreads through the cortex. We found a progressive phase shift from posterior parieto-occipital sites over the cortex with a phase velocity of approx. 8–14 m/s and wavelength of about 21 and 24 cm. The SSVEP spatial properties appear sensitive to input frequency with higher stimulation frequencies showing a faster propagation speed.

Daylight performance analysis of TiO2@W-VO2 thermochromic smart glazing in office buildings

Thermochromic glazing (TC) is able to modulate the solar radiation transmittance through windows in response to temperature, passively. Apart from the significant role of TC windows in thermal energy conservation in buildings, they affect the indoor daylight performance due to their lower visible transmittance rate and tinted appearance. In this paper, we carried out a comprehensive study on the impact of TiO2@W-VO2 thermochromic glazing, fabricated by the authors, on indoor daylighting performance of a typical office room. The spectrophotometry test on the fabricated TC glass shows a significant modulation ability in near-infrared wavelengths. Based on the measured optical transmittance, daylight behaviors of the glazing were elaborated in terms of visual comfort, color quality of the transmitted light, non-visual daylight availability, and artificial lighting load, using computer simulation methods and numerical calculations. Finally, the paper offers an interactive approach between material development and fabrication methods on one hand, and holistic thermal and daylight analysis of the product on the other hand. This approach optimizes the physical properties of a TC glazing in tradeoff between solar modulation ability, visible transmittance, and color appearance.

Evaluation of The Passenger Areas of Underground Subway Stations In Terms of Visual Comfort: The Sample of Kadıköy and Kartal Stations

Evaluation of The Passenger Areas of Underground Subway Stations In Terms of Visual Comfort: The Sample of Kadıköy and Kartal Stations

Using Saliency-Weighted Disparity Statistics for Objective Visual Comfort Assessment of Stereoscopic Images

Visual comfort assessment (VCA) for stereoscopic images is a particularly significant yet challenging task in 3D quality of experience research field. Although the subjective assessment given by human observers is known as the most reliable way to evaluate the experienced visual discomfort, it is time-consuming and non-systematic. Therefore, it is of great importance to develop objective VCA approaches that can faithfully predict the degree of visual discomfort as human beings do. In this paper, a novel two-stage objective VCA framework is proposed. The main contribution of this study is that the important visual attention mechanism of human visual system is incorporated for visual comfort-aware feature extraction. Specifically, in the first stage, we first construct an adaptive 3D visual saliency detection model to derive saliency map of a stereoscopic image, and then a set of saliency-weighted disparity statistics are computed and combined to form a single feature vector to represent a stereoscopic image in terms of visual comfort. In the second stage, a high dimensional feature vector is fused into a single visual comfort score by performing random forest algorithm. Experimental results on two benchmark databases confirm the superior performance of the proposed approach.

The impact of the software’s choice on dynamic daylight simulations’ results: A comparison between Daysim and 3ds Max Design®

Evaluating indoor daylight availability is extremely important in order to define the characteristics of an environment in terms of visual comfort and energy performances of lighting systems. The criticism of the static calculation approach based on Daylight Factor led to the development of the Climate Based Daylight Modeling (CBDM) one. Dynamic simulations are performed thanks to the use of specific software and the choice of a calculation tool or another could provide different output results. Therefore the aim of this paper is to compare results of dynamic daylight simulations carried out with two different software, Daysim and 3ds Max Design® and referred to a simple office located in 4 different cities and exposed according to the 4 main orientations. It demonstrates that differences in results are more or less significant depending on several factors: outdoor daylight conditions, window’s orientation and considered internal calculation point.

Three-dimensional visual comfort assessment via preference learning

Three-dimensional (3-D) visual comfort assessment (VCA) is a particularly important and challenging topic, which involves automatically predicting the degree of visual comfort in line with human subjective judgment. State-of-the-art VCA models typically focus on minimizing the distance between predicted visual comfort scores and subjective mean opinion scores (MOSs) by training a regression model. However, obtaining precise MOSs is often expensive and time-consuming, which greatly constrains the extension of existing MOS-aware VCA models. This study is inspired by the fact that humans tend to conduct a preference judgment between two stereoscopic images in terms of visual comfort. We propose to train a robust VCA model on a set of preference labels instead of MOSs. The preference label, representing the relative visual comfort of preference stereoscopic image pairs (PSIPs), is generally precise and can be obtained at much lower cost compared with MOS. More specifically, some representative stereoscopic images are first selected to generate the PSIP training set. Then, we use a support vector machine to learn a preference classification model by taking a differential feature vector and the corresponding preference label of each PSIP as input. Finally, given a testing sample, by considering a full-round paired comparison with all the selected representative stereoscopic images, the visual comfort score can be estimated via a simple linear mapping strategy. Experimental results on our newly built 3-D image database demonstrate that the proposed method can achieve a better performance compared with the models trained on MOSs.

Dallos Award 2014: Effects on binocular and peripheral visual functions of distance center multifocal soft contact lens designs and significance of add power

Purpose: To investigate the effects on binocular vision and peripheral awareness of distance center multifocal soft contact lenses (MF SCLs) used for myopia control. Method: Twenty-four young adult myopes (18.1–28.6 years; 20 females, 4 males) participated. Baseline acuity, accommodation, near phoria, AC/A, fixation disparity and stereopsis data were collected with single vision distance SCLs. Peripheral visual field detection ability was also assessed using the Useful Field of View test. The samesetofmeasurementswas repeated immediatelyafter subjects were fitted with each of two Proclear distance centre MF SCLs (+1.50 & +3.00 D near adds respectively), and after a 2 week adaptation period of daily wear in each case. The order of testing was randomized and a one-week washout period was allowed between the first and second lens trials. Results: The +3.00 D MF SCLs slightly but significantly reduced both high and low contrast distance acuity by 0.07±0.11 and 0.08±0.11, respectively, while +1.50 D MF SCLs had no significant effect, and near visual acuity was not impaired by either lens design. BothMF lenses also significantly increased accommodative lags, initially by 0.49 D and 0.19 D for the +3.00 and +1.50 D adds respectively, these changes being no longer apparent after 2 weeks of adaptation. The +3.00 D MF SCLs but not the +1.50 D MF SCLs also resulted in significant near exophoric shifts of 3.69 . BothMF SCL designs improved peripheral field detection and were without effect on central field detection. Conclusion: The MF SCL-induced changes in visual acuity were small and do not in themselves argue against the use of the lenses for myopia control. Furthermore, these lenses improved peripheral detection ability, suggesting that the subjects had peripheral hyperopic errors that were reduced or eliminated with the lenses, although peripheral refractions were not measured. Finally given the MF SCL exo shifts in near phoria, myopes with near esophorias and/or fixation disparities are expected to benefitmost, in terms of visual comfort, andperhaps also in terms of improved retinal image quality and myopia control.

The impact of video characteristics and subtitles on visual comfort of 3D TV

Some viewers of stereoscopic content experience visual discomfort that can be induced or intensified by certain video characteristics such as fast in-scene motion, large changes in disparity and depth discontinuities caused by subtitles. An experiment was carried out to determine the impact of these video characteristics in terms of visual comfort via different measurement methods. Two 3-D movies of approximately 15min each, both with and without subtitles, were assessed in terms of visual comfort via a continuous assessment and retrospective questionnaires. Analysis of the questionnaire data revealed that subtitles negatively affect how viewers watch stereoscopic movie in terms of general visual comfort items as well as in terms of double vision and sharpness. Via the questionnaires, participants reported that their visual comfort assessment depended primarily on the motion and (changes in) depth in the video content. The scores of the continuous assessment were directly correlated to video characteristics that were derived from the 3-D movies. In line with the questionnaire results, analysis of the continuous assessment scores revealed that visual comfort could be predicted from a linear combination of these video characteristics per scene, yet more complex models are required to extend the comfort prediction to entire movies, incorporating different scenes.

Visual discomfort of 3D TV: Assessment methods and modeling

To gain knowledge on how visual discomfort is built up while watching stereoscopic content an experiment was designed with two objectives: (1) to compare the continuous evaluation method with other assessment methods that potentially can substitute the continuous evaluation for the assessment of visual discomfort of e.g., feature-length movies, and (2) to relate the impact of time-variant content characteristics, such as motion and disparity, to the assessment of visual discomfort. In an experiment a 24 min 3D movie ‘Spy Kids 3-D: game over’ converted from 2D to 3D was displayed on a 9-view autostereoscopic lenticular LCD, and continuously assessed in terms of visual comfort by 24 participants. Additional assessment methods included the assessment of six 10 s sequences captured from the 3D movie and a single retrospective assessment of the entire 3D movie. Time-variant content characteristics, such as derivatives of motion and screen disparity values, were extracted from the 3D movie with motion and depth estimation algorithms. The moment-to-moment values of these characteristics were correlated to the continuous assessment scores of visual discomfort. With respect to the first objective, results reveal that the correlation between the assessment of the 10 s sequences captured from the 3D movie and their corresponding part within the continuous assessment is low, whereas the correlation between the retrospective assessment and the mean of the continuous assessment score over scene parts with a high screen disparity is higher. With respect to the second objective, for static scenes the visual comfort can be largely described by the screen disparity offset and range. For dynamic scenes the visual comfort is largely related to the screen disparity range, lateral motion and to the change in screen disparity.

The role of the PASLINK test cell in the modelling and integrated simulation of an innovative window

The SOLVENT window is an innovative glazing system concept that involves the use of a rotating frame, an absorptive glazing and a naturally ventilated vertical channel, in order to improve the balance between the visual comfort and the energy efficiency of windows. The tools available for simulating the behaviour of the window in terms of visual comfort and of thermal and energetic behaviour are complex and potentially dependent on many calibration parameters, such as the heat convection coefficients and the number of nodes in an air-flow network. Different modelling approaches can lead to large variability in the results obtained. It is thus essential that the models are supported by measurements that may, on one hand, help to optimise the component modelling and, on the other hand, ensure that the global results provided by the model are realistic. In the case of the SOLVENT window, a prototype mounted on a PASLINK test cell in Porto (Portugal) played a fundamental role in this process. The monitoring results were used to: (a) assess the quality of the results obtained with a base case model, (b) develop improved models for the air flow and for the heat convection in the vertical air channel, (c) validate the results for the global heating and cooling loads obtained with the optimised model, and (d) calibrate the parameters needed for accurate daylighting simulation with Radiance. Once the component model was optimised and validated, it was then applied in realistic global building models for detailed performance studies. An example is provided in this paper for the virtual application of the SOLVENT window to an office in Porto, Portugal.

On the Issue of Illuminance Requirement as a Design Criterion

Although there are many factors contributing to the quality of luminous environment, lighting design standards are almost entirely based on one predominant parameter, namely illuminance level for task performance. In this paper we will discuss the limitations of such a practice based on the findings made in terms of visual comfort and users preferences in lighting.