Luminance Levels Research Articles

Investigation of the Optimum Display Luminance of an LCD Screen under Different Ambient Illuminances in the Evening

Ambient illuminance and screen luminance have a significant influence on the visual fatigue and visual performance associated with the use of computers. The current study was conducted to investigate optimal screen luminance under different ambient illuminances and fit a curve of the optimum luminance of LCD screens under evening illumination. Thirty-three participants were assigned to rate screen brightness, visual comfort with screen luminance, satisfaction with ambient illuminance and visual fatigue under six screen luminance levels (3.87, 21.47, 42.74, 64.12, 84.77 and 106.7 cd/m2) combined with five ambient illuminance levels (0, 25, 50, 75 and 100 lx) in the evening. The results showed that optimum LCD screen luminance increased with increasing ambient illuminance. Moreover, ambient illuminance and screen luminance levels should be in the range of 13.08–62.16 lx and 20.63–75.15 cd/m2, respectively, to obtain the optimal subjective feelings of visual fatigue and visual comfort during the evening.

Color appearance shift in augmented reality metameric matching.

The physical additivity of optical-see-through (OST) augmented reality (AR), where display and the real-world overlay with each other, impacts its color appearance. We explored this unique dynamic by looking at the effect of background correlated color temperature (CCT) on AR color appearance with a color matching experiment between a prototype OST-AR RGB system and daylight spectrum reproduction. Different background CCT, luminance levels, and two stimulus types [simulated two-dimensional (2D) disk and three-dimensional (3D) cube] were examined. We found that when the background color is inconsistent with the stimulus providing conflicted cues, matched colors in AR shifted towards the background. The luminance matched on the 3D cube is higher than the 2D disk, suggesting the impact of context on the AR appearance. A controlled metameric matching group between daylight reproduction and LCD or CRT did not show the shift, indicating that the appearance shift is not due to the RGB-spectrum metameric matching, but due to RGB foreground-spectral background interaction beyond simple additivity. How perceptual weighting on the foreground and background is modified to predict the appearance as a function of additivity is discussed.

Novel Deep‐Blue Hybridized Local and Charge‐Transfer Host Emitter for High‐Quality Fluorescence/Phosphor Hybrid Quasi‐White Organic Light‐Emitting Diode

AbstractA new hybrid local and charge transfer (HLCT) molecule 2TPA‐PPI is obtained for constructing the high‐performance organic light‐emitting diodes (OLEDs) in this work. 2TPA‐PPI possesses the sufficient emission/charge‐transporting properties, thus it is used as a neat emitter achieving an efficient deep‐blue OLED with very high external quantum efficiency (EQE) up to 10.7%, as well as a multi‐functional emitting host matrix constructing the high‐performance phosphorescent OLEDs. More importantly, a high‐efficiency candle light‐style OLED adopting the HLCT/phosphor hybrid strategy is realized, where 2TPA‐PPI acts as not only a blue emitter, but also a universal host sensitizing both yellow and red phosphors. This quasi‐white OLED represents almost the highest EQE/PE level of 25.2%/49.7 lm W−1 at the practical luminance level of 1000 cd m−2 for the white OLEDs with the excellent color rendering index values of more than 80 reported.

The linearization of the relationship between scene luminance and digital camera output levels

The linearization of the relationship between scene luminance and digital camera output levels

Display dimming model characterized by three-dimensional ergonomic study

Self-luminous display devices are essential in various working environments, such as aircraft cockpits and the driver cab of vehicles and trains, where the external light environment varies drastically. Owing to the significant illumination changes, auto-adjusted display luminance based on ambient lighting is necessary for drivers to work efficiently and comfortably. This study proposes a display dimming model based on three dimensions of ergonomic testing, consisting of visual performance (VP), visual comfort (VC), and visual fatigue (VF). Five ambient illuminances, each combined with five display luminance levels, form a total of 25 conditions demonstrated in this experiment. Using a within-subject design, ten observers experienced all the combination conditions. The experiment employs the Anfimov table to test the VP, VC scale to evaluate VC, and VF scale to assess VF. Based on the experimental results, sub-models are constructed to clarify the characteristics of each dimension (VP, VC, and VF). Subsequently, the analytic hierarchy process is employed to construct an evaluation system by calculating the weight of each dimension in the total score. Finally, exponential fitting is utilized to build a wide-range display dimming model, which explicitly describes the inherent connection of complex light environment matching.

Investigating Arousal, Saccade Preparation, and Global Luminance Effects on Microsaccade Behavior.

Microsaccades, small saccadic eye movements occurring during fixation, have been suggested to be modulated by various sensory, cognitive, and affective processes relating to arousal. Although the modulation of fatigue-related arousal on microsaccade behavior has previously been characterized, the influence of other aspects of arousal, such as emotional arousal, is less understood. Moreover, microsaccades are modulated by cognitive processes (e.g., voluntary saccade preparation) that could also be linked to arousal. To investigate the influence of emotional arousal, saccade preparation, and global luminance levels on microsaccade behavior, emotional auditory stimuli were presented prior to the onset of a fixation cue whose color indicated to look either at the peripheral stimulus (pro-saccade) or in the opposite direction of the stimulus (anti-saccade). Microsaccade behavior was found to be significantly modulated by saccade preparation and global luminance level, but not emotional arousal. In the pro- and anti-saccade task, microsaccade rate was lower during anti-saccade preparation as compared to pro-saccade preparation, though microsaccade dynamics were comparable during both trial types. Our results reveal a differential role of arousal linked to emotion, fatigue, saccade preparation, and global luminance level on microsaccade behavior.

The impact of LED spectrum and correlated color temperature on driving safety in long tunnel lighting

According to the Chinese Guidelines JTG/T D70/2-01-2014, there are many long tunnels in China, especially in mountainous areas. In long tunnels, tunnel lighting influence not only visual performance but also non-visual effects. Non-visual effects has enhanced the importance of some factors directly related to driving safety, such as pupil constriction and visual fatigue which seriously affect reaction time of driver. In this work, the relationship between LED spectrum, correlated color temperature (CCT) and reaction time, pupil area difference are analyzed respectively by the experiment of reaction time. Five LEDs with different CCT and short-wave relative spectral value (RSV) are compared to HPS and MH under different tunnel lighting conditions. Experimental results show that, in the threshold and transition zone of long tunnel at luminance160cd/m2, 80 cd/m2 and 24 cd/m2, reaction time is the shortest and pupil constricted the most for LED lighting with CCT 5100 K and short-wave RSV 0.312. While in the interior zone of long tunnel at luminance 4.5 cd/m2 and 2.5 cd/m2, reaction time is the shortest and pupil constricted the most for LED lighting with CCT 3800 K and short-wave RSV 0.215. Based on the results, combining the impacts of visual performance and non-visual effects in long tunnels, this work proposed the recommended values of CCT and short-wave RSV for LED light sources that are suitable for the luminance level of different zones. In this way, the precise lighting can be implemented to meet the needs of long tunnel lighting for driving safety and energy saving.

The Drive towards Optimization of Road Lighting Energy Consumption Based on Mesopic Vision—A Suburban Street Case Study

This paper presents the research of optimization of road lighting energy consumption by utilizing the fact of human twilight and night vision (mesopic vision) dependency on luminance level and lamp’s light spectral composition. The research was conducted for a suburban street illuminated by smart LED road luminaires with a luminous flux control system with which different luminance levels can be achieved on the road. This road is an access road leading to a town located on the outskirts of Warsaw which is the capital of Poland and a large metropolitan area. Therefore, the traffic here is quite heavy on this road in the morning and in the evening and it is very light at other times of the day. In accordance with EN 13201 standard, lighting control can be applied to illuminate this road. This paper compares energy consumption for different lighting scenarios of the road in question. In the first scenario, the road luminance is compliant with M4, M5, and M6 lighting class requirements depending on the time of the day. In the second scenario, for each M lighting class, the values of luminance levels provided by EN 13201 standard have been reduced to the values resulting from their conversion to the corresponding mesopic luminance values. The conducted research has shown that a 15% saving per year in electricity consumption on the road is possible with such a conversion. Therefore, energy efficiency of a lighting installation can be improved by matching the lighting levels provided by the standard to the mesopic vision.

Simulation and Analysis of Floodlighting Based on 3D Computer Graphics

The paper presents the opportunities to apply computer graphics in an object floodlighting design process and in an analysis of object illumination. The course of object floodlighting design has been defined based on a virtual three-dimensional geometric model. The problems related to carrying out the analysis of lighting, calculating the average illuminance, luminance levels and determining the illuminated object surface area are also described. These parameters are directly tied with the calculations of the Floodlighting Utilisation Factor, and therefore, with the energy efficiency of the design as well as the aspects of light pollution of the natural environment. The paper shows how high an impact of the geometric model of the object has on the accuracy of photometric calculations. Very often the model contains the components that should not be taken into account in the photometric calculations. The research on what influence the purity of the geometric mesh of the illuminated object has on the obtained results is presented. It shows that the errors can be significant, but it is possible to optimise the 3D object model appropriately in order to receive the precise results. For the example object presented in this paper, removing the planes that do not constitute its external surface has caused a two-fold increase in the average illuminance and average luminance. This is dangerous because a designer who wants to achieve a specific average luminance level in their design without optimizing the model will obtain the luminance values that will actually be much higher.

Decoding chromaticity and luminance from patterns of EEG activity.

A long-standing question in the field of vision research is whether scalp-recorded EEG activity contains sufficient information to identify stimulus chromaticity. Recent multivariate work suggests that it is possible to decode which chromaticity an observer is viewing from the multielectrode pattern of EEG activity. There is debate, however, about whether the claimed effects of stimulus chromaticity on visual evoked potentials (VEPs) are instead caused by unequal stimulus luminances, which are achromatic differences. Here, we tested whether stimulus chromaticity could be decoded when potential confounds with luminance were minimized by (1) equating chromatic stimuli in luminance using heterochromatic flicker photometry for each observer and (2) independently varying the chromaticity and luminance of target stimuli, enabling us to test whether the pattern for a given chromaticity generalized across wide variations in luminance. We also tested whether luminance variations can be decoded from the topography of voltage across the scalp. In Experiment 1, we presented two chromaticities (appearing red and green) at three luminance levels during separate trials. In Experiment 2, we presented four chromaticities (appearing red, orange, yellow, and green) at two luminance levels. Using a pattern classifier and the multielectrode pattern of EEG activity, we were able to accurately decode the chromaticity and luminance level of each stimulus. Furthermore, we were able to decode stimulus chromaticity when we trained the classifier on chromaticities presented at one luminance level and tested at a different luminance level. Thus, EEG topography contains robust information regarding stimulus chromaticity, despite large variations in stimulus luminance.

Assessing optimal colour and illumination to facilitate reading.

This study examined the effectiveness of the LuxIQ, the Apple iPad and a smart bulb in assessing optimal colour and illumination to facilitate reading in younger, older and visually impaired adults. Participants read standardised texts at baseline (normal lighting/no device), then using the Apple iPad, LuxIQ and smart bulb, with their normal vision (20/20 condition) and using a simulated reduction in visual acuity/contrast sensitivity (20/80 condition). Visually impaired participants followed the same procedure used in the 20/80 condition. There was a significant interaction between condition and device in younger, F(1.5, 43.51)=30.41, p<0.001, ω2 =0.34 and older, F(1.5, 4.51)=4.51, p=0.03, ω2 =0.05 adults with normal vision, and there was a significant effect of device, F(2, 58)=5.95, p=0.004, ω2 =0.12 in visually impaired adults. In the 20/20 condition, age and colour predicted reading speed, F(3, 176) = 36.25, p<0.001, Adj. R2 =0.37, whereas age, lighting and colour predicted reading speed, F(3, 176) = 36.25, p<0.001, Adj. R2 =0.37 in the 20/80 condition. In the visual impairment condition, lighting, colour and impairment severity predicted reading speed, F(3, 85) = 10.10, p<0.001, Adj. R2 =0.24. The clinical implications of this study are that reading speeds improve in individuals with low vision under improved lighting conditions, specifically, with higher levels of luminance and colour temperature. The effectiveness of the devices varied across groups; however, the LuxIQ was the only device to improve reading speeds from baseline in older adults with visual impairments.

Melanopic Limits of Metamer Spectral Optimisation in Multi-Channel Smart Lighting Systems

Modern indoor lighting faces the challenge of finding an appropriate balance between energy consumption, legal requirements, visual performance, and the circadian effectiveness of a spectrum. Multi-channel LED luminaires have the option of keeping image-forming metrics steady while varying the melanopic radiance through metamer spectra for non-visual purposes. Here, we propose the theoretical concept of an automated smart lighting system that is designed to satisfy the user’s visual preference through neural networks while triggering the non-visual pathway via metamers. To quantify the melanopic limits of metamers at a steady chromaticity point, we have used 561 chromaticity coordinates along the Planckian locus (2700 K to 7443 K, ±Duv 0 to 0.048) as optimisation targets and generated the spectra by using a 6-channel, 8-channel, and 11-channel LED combination at three different luminance levels. We have found that in a best-case scenario, the melanopic radiance can be varied up to 65% while keeping the chromaticity coordinates constant (Δu′v′≤7.05×10−5) by using metamer spectra. The highest melanopic metamer contrast can be reached near the Planckian locus between 3292 and 4717 K within a Duv range of −0.009 to 0.006. Additionally, we publish over 1.2 million optimised spectra generated by multichannel LED luminaires as an open-source dataset along with this work.

Image Quality Comparison between LCD and OLED Display

The image qualities of LCD and OLED monitors set to their own default settings were compared using forced-choice experiment method. Both displays’ peak white luminance was around 1,000 cd/m2 and color gamut setting was fixed as DCI-P3 for LCD while OLED’s gamut was set as DCI-P3 or BT.2020. The twelve image quality evaluation keywords were collected through the focus group Interview and eleven HDR video clips were selected as test stimuli. During the experiment, the test video was shown on two displays placed side-by-side and thirteen naïve participants were asked to select the display having the better image quality. The experimental results showed that OLED has higher image quality than LCD does because of higher colorfulness in general. Black luminance level affected the image quality for the dark images but the images having large bright area, colorfulness affected the overall image quality. This result shows that not display technology but the color characteristics affects the image quality.

Enterococcus faecalis Glucosamine Metabolism Exacerbates Experimental Colitis.

Background & AimsThe inflammatory bowel diseases (IBDs), Crohn’s disease and ulcerative colitis, are caused in part by aberrant immune responses to resident intestinal bacteria. Certain dietary components, including carbohydrates, are associated with IBDs and alter intestinal bacterial composition. However, the effects of luminal carbohydrates on the composition and colitogenic potential of intestinal bacteria are incompletely understood. We hypothesize that carbohydrate metabolism by resident proinflammatory intestinal bacteria enhances their growth and worsens intestinal inflammation.MethodsWe colonized germ-free, wild-type, and colitis-susceptible interleukin-10 knockout mice (Il10-/-) with a consortium of resident intestinal bacterial strains and quantified colon inflammation using blinded histologic scoring and spontaneous secretion of IL12/23p40 by colon explants. We measured luminal bacterial composition using real-time 16S polymerase chain reaction, bacterial gene expression using RNA sequencing and real-time polymerase chain reaction, and luminal glucosamine levels using gas chromatography–mass spectrometry.ResultsWe show that a consortium of 8 bacterial strains induces severe colitis in Il10-/- mice and up-regulates genes associated with carbohydrate metabolism during colitis. Specifically, Enterococcus faecalis strain OG1RF is proinflammatory and strongly up-regulates OG1RF_11616-11610, an operon that encodes genes of a previously undescribed phosphotransferase system that we show imports glucosamine. Experimental colitis is associated with increased levels of luminal glucosamine and OG1RF_11616 causes worse colitis, not by increasing E faecalis numbers, but rather by mechanisms that require the presence of complex microbiota.ConclusionsFurther studies of luminal carbohydrate levels and bacterial carbohydrate metabolism during intestinal inflammation will improve our understanding of the pathogenesis of IBDs and may lead to the development of novel therapies for these diseases.

RELATIONSHIP BETWEEN DISCOMFORT GLARE AND ELECTROENCEPHALOGRAPHY DURING WORKING IN FRONT OF A WINDOW

It is important to consider discomfort glare in designing comfortable office environment. Architectural Institute of Japan has set UGR and PGSV as design criteria for discomfort glare, but those indicators do not completely reflect the needs for lighting environments due to differences in work behavior. For example, when performing a task that requires concentration, worker may prefer a glare environment to increase one's level of alertness. From the subjective glare and the degree of awakening during work behavior, it is considered necessary to examine the method of indicators that are more suited to actions. Therefore, we focused on the relationship between discomfort glare and EEG, and conducted two experiments with different presentation luminance range. The number of subjects was 10 (5 males and 5 females) in both Experiments 1 and 2, and the age were 21-24 in Experiment 1 and 22-25 in Experiment 2. The experiments were conducted in a space with simulated windows, assuming an office space. The experimental factors were luminance levels of the window and subject' conditions ("Task" is the task of looking at the monitor and doing the calculation work, and "No task" is a task to view the monitor without doing anything). In Exp. 1, luminance levels of the window were 2000, 8000, 14000, 20000 cd/m2, and in Exp. 2, 2000, 5000, 8000, 14000 cd/m2. The measurement indexes were EEG, GSV, and subjective evaluations.

Effects of pupillary light and darkness reflex on the generation of pro- And anti-saccades.

Saccades are often directed toward a stimulus that provides useful information for observers to navigate the visual world. The quality of visual signals of a stimulus is influenced by global luminance, and the pupil constricts or dilates after a luminance increase or decrease, respectively, to optimize visual signals for further information processing. Although luminance level changes regularly in the real environment, saccades are mostly studied in the luminance-unchanged setup. Whether pupillary responses triggered by global luminance changes modulate saccadic behavior are yet to be explored. Through varying background luminance level in an interleaved pro- and anti-saccade paradigm, we investigated the modulation of pupillary luminance responses on the generation of reflexive and voluntary saccades. Subjects were instructed to either automatically look at the peripheral stimulus (pro-saccade) or to suppress the automatic response and voluntarily look in the opposite direction from the stimulus (anti-saccade). Level of background luminance was increased (light), decreased (dark), or unchanged (control) during the instructed fixation period. Saccade reaction time distributions of correct pro- and anti-saccades in the light and dark conditions were differed significantly from those in the control condition. Moreover, the luminance condition modulated saccade kinematics, showing reduced performances in the light condition than in the control condition, particularly in pro-saccades. Modeling results further suggested that both pupil diameter and pupil size derivative significantly modulated saccade behavior, though effect sizes were small and mainly mediated by intersubject differences. Together, our results demonstrated the influence of pupillary luminance responses on the generation of pro- and anti-saccades.

Emerging roles of calcium-sensing receptor in the local regulation of intestinal transport of ions and calcium.

Whether the intestinal mucosal cells are capable of sensing calcium concentration in the lumen and pericellular interstitium remains enigmatic for decades. Most calcium-regulating organs, such as parathyroid gland, kidney, and bone, are capable of using calcium-sensing receptor (CaSR) to detect plasma calcium and trigger appropriate feedback responses to maintain calcium homeostasis. Although both CaSR transcripts and proteins are abundantly expressed in the crypt and villous enterocytes of the small intestine as well as the surface epithelial cells of the large intestine, the studies of CaSR functions have been limited to amino acid sensing and regulation of epithelial fluid secretion. Interestingly, several lines of recent evidence have indicated that the enterocytes use CaSR to monitor luminal and extracellular calcium levels, thereby reducing the activity of transient receptor potential channel, subfamily V, member 6, and inducing paracrine and endocrine feedback responses to restrict calcium absorption. Recent investigations in zebra fish and rodents have also suggested the role of fibroblast growth factor (FGF)-23 as an endocrine and/or paracrine factor participating in the negative control of intestinal calcium transport. In this review article, besides the CaSR-modulated ion transport, we elaborate the possible roles of CaSR and FGF-23 as well as their crosstalk as parts of a negative feedback loop for counterbalancing the seemingly unopposed calciotropic effect of 1,25-dihydroxyvitamin D3 on the intestinal calcium absorption.

Increased intestinal phosphate absorption, an often-overlooked effect of vitamin D.

Increased intestinal phosphate absorption, an often-overlooked effect of vitamin D.

Asymmetric voltage waveform for enhanced exciton generation in alternative-current field-induced electroluminescence device.

We propose an alternating current (AC) field operation scheme by using an asymmetric voltage waveform to improve the electroluminescence property of AC field-induced electroluminescence (AC-FIEL) devices. Hole injection and transport can be improved by carbon nanotubes (CNT) doping into the emission layer of an AC-FIEL structure operated by a single electrode for AC-responsive alternating carrier injections. However, under an AC operation, highly unbalanced charge transports are inevitably present in CNT-doped AC-FIEL devices due to faster carrier paths through CNTs. Compared with symmetric waveform, asymmetric waveform can be adjusted to allow longer relative duty time for faster carriers in which the luminance level of CNT-doped AC-FIEL devices can be improved by 1.4 times at the same device structure and operation frequency condition.

Improvement of Low Luminance Visual Acuity in Patients with Chronic Central Serous Chorioretinopathy after Half-Dose Verteporfin Photodynamic Therapy.

Patients with central serous chorioretinopathy (CSC) often complain of visual difficulties under low luminance conditions. In this study, we evaluated low luminance visual acuity (LLVA) after half-dose verteporfin photodynamic therapy (hdPDT) in eyes with CSC. The study included eight eyes of eight patients with chronic CSC that underwent hdPDT. The best-corrected visual acuity, LLVA and optical coherence tomography (OCT) findings were evaluated at baseline, and at 1, 3, 6, 9, and 12 months after hdPDT. LLVA was measured at six levels of background luminance. Serous retinal detachment was completely resolved in all eyes. Although the mean LLVA at 1 month did not improve significantly compared to baseline at all luminance levels, significant improvements were observed at 3, 6, 9, and 12 months (p < 0.05). In OCT images, although the ellipsoid zone was not detectable in all eyes before hdPDT, it was observed in 2 eyes at 1 month, in 7 eyes at 3 months, and in all eyes from 6 months. The LLVA and the ellipsoid zone improved similarly with postoperative time courses. In conclusion, hdPDT improves LLVA in eyes with chronic CSC. The recovery of the ellipsoid zone may play a part in improving LLVA after hdPDT.