Luminance Changes Research Articles

Perception in HDR and Displays

AbstractAlthough the world has been high dynamic range (HDR) all along, commercial HDR displays’ burgeoning availability provides new and interesting challenges for colorimetry and perceptual modeling. The biggest challenge stems from the way that large luminance changes spatial and temporal scales often compressed relative to the natural world. This results in veridical luminance/chromaticity reproduction not representing appearance reproduction. Here, the authors review some of the perceptual and colorimetric issues that create challenges in HDR image reproduction.

P‐99: Low Driving Voltage and High Color‐Stability White OLEDs on Silicon via Thin‐Charge Generation Unit for Microdisplays

In this research, we studied white organic light emitting diodes on silicon (OLEDoS) devices with low driving voltage and high color stability for microdisplay in augmented reality (AR) applications. In this device architecture, a thin charge generation unit (CGU) with 10 nm thickness was introduced into blue fluorescent and yellowish‐green phosphorescent emitting layers. It showed 5.8 V driving voltage at 1,000 cd/m2 with (0.276, 0.382) color coordinates which is sufficiently cool white emission. It also presented maximum luminance of 50,015 cd/m2 at 10 V driving voltage. It also showed high color stability of (± 0.007, ± 0.006) according to the luminance change from 500 to 2,000 cd/m2.

The effect of luminance on the perception of small color differences

AbstractThe objectives of this study were two‐fold; to determine how variations in practical illuminance range (from ~300 to ~2300 lx) affect the perception of suprathreshold small color differences for a range of object stimuli across the color space, and to investigate the role of variations in luminance on intra‐ and inter‐observer variability in repeated psychophysical trials. STRESS index and conventional statistical methods suggest the presence of a significant difference between visual responses for large changes in luminance. Inter‐ and intra‐observer variability also varied according to luminance. Calculated color differences based on recent CAM models show good agreement with visual results over the luminance range examined.

Neoptile feathers contribute to outline concealment of precocial chicks

Camouflage is a widespread strategy to increase survival. The cryptic plumage colouration of precocial chicks improves camouflage often through disruptive colouration. Here, we examine whether and how fringed neoptile feathers conceal the outline of chicks. We first conducted a digital experiment to test two potential mechanisms for outline concealment through appendages: (1) reduction of edge intensity and (2) luminance transition. Local Edge Intensity Analysis showed that appendages decreased edge intensity whereas a mean luminance comparison revealed that the appendages created an intermediate transition zone to conceal the object’s outline. For edge intensity, the outline diffusion was strongest for a vision system with low spatial acuity, which is characteristic of many mammalian chick predators. We then analysed photographs of young snowy plover (Charadrius nivosus) chicks to examine whether feathers increase outline concealment in a natural setting. Consistent with better camouflage, the outline of digitally cropped chicks with protruding feathers showed lower edge intensities than the outline of chicks without those feathers. However, the observed mean luminance changes did not indicate better concealment. Taken together, our results suggest that thin skin appendages such as neoptile feathers improve camouflage. As skin appendages are widespread, this mechanism may apply to many organisms.

Conditions of a Multi-View 3D Display for Accurate Reproduction of Perceived Glossiness.

Visualizing objects as they are perceived in the real world is often critical in our daily experiences. We previously focused on objects' surface glossiness visualized with a 3D display and found that a multi-view 3D display reproduces perceived glossiness more accurately than a 2D display. This improvement of glossiness reproduction can be explained by the fact that a glossy surface visualized by a multi-view 3D display appropriately provides luminance differences between the two eyes and luminance changes accompanying the viewer's lateral head motion. In the present study, to determine the requirements of a multi-view 3D display for the accurate reproduction of perceived glossiness, we developed a simulator of a multi-view 3D display to independently and simultaneously manipulate the viewpoint interval and the magnitude of the optical inter-view crosstalk. Using the simulator, we conducted a psychophysical experiment and found that glossiness reproduction is most accurate when the viewpoint interval is small and there is just a small (but not too small) amount of crosstalk. We proposed a simple yet perceptually valid model that quantitatively predicts the reproduction accuracy of perceived glossiness.

Subjective responses toward daylight changes in window views: Assessing dynamic environmental attributes in an immersive experiment

In urbanized settlements, ensuring access to the outdoor environment is essential to stimulate well-being responses indoors. Windows provide access to aesthetic and natural features and bring in clues about the time, weather, and seasonal conditions outdoors. Although dynamic environmental attributes are inherent outdoor view qualities, no studies have explored the effects induced by such dynamic conditions on individuals, limiting the extent to which these features might inform design guidelines for sustained indoor well-being. To address this gap, a virtual reality experiment was conducted to analyze subjective responses to lightness changes in outdoor views with respect to three view constructs (i.e., preference, recovery, and imageability). A novel framework for classifying, capturing, and analyzing urban views was extended to generate the view stimuli material consisting of dynamic and static scenes (i.e., panorama images and 360° videos). Attitudes toward dynamic and static views were tested with an adjusted rating instrument. Results showed significant interactions between view type and lightness change factors for the three view constructs presented in dynamic format. Mean scores for views presenting lightness variations were higher than those observed for identical scenes portraying no lightness variations. Low coefficients of variation for individual questions were found, suggesting the adequacy of the subjective instruments to evaluate dynamic views. Moderate to high positive Pearson correlation coefficients were found between three construct pairs, indicating links between the approaches to examine views. The findings in this study demonstrate that positive attitudes toward views are strongly mediated by the presence of luminous changes in these views.

A Recurrent Neural Network for Attenuating Non-cognitive Components of Pupil Dynamics.

There is increasing interest in how the pupil dynamics of the eye reflect underlying cognitive processes and brain states. Problematic, however, is that pupil changes can be due to non-cognitive factors, for example luminance changes in the environment, accommodation and movement. In this paper we consider how by modeling the response of the pupil in real-world environments we can capture the non-cognitive related changes and remove these to extract a residual signal which is a better index of cognition and performance. Specifically, we utilize sequence measures such as fixation position, duration, saccades, and blink-related information as inputs to a deep recurrent neural network (RNN) model for predicting subsequent pupil diameter. We build and evaluate the model for a task where subjects are watching educational videos and subsequently asked questions based on the content. Compared to commonly-used models for this task, the RNN had the lowest errors rates in predicting subsequent pupil dilation given sequence data. Most importantly was how the model output related to subjects' cognitive performance as assessed by a post-viewing test. Consistent with our hypothesis that the model captures non-cognitive pupil dynamics, we found (1) the model's root-mean square error was less for lower performing subjects than for those having better performance on the post-viewing test, (2) the residuals of the RNN (LSTM) model had the highest correlation with subject post-viewing test scores and (3) the residuals had the highest discriminability (assessed via area under the ROC curve, AUC) for classifying high and low test performers, compared to the true pupil size or the RNN model predictions. This suggests that deep learning sequence models may be good for separating components of pupil responses that are linked to luminance and accommodation from those that are linked to cognition and arousal.

Attractiveness in the Eyes: A Possibility of Positive Loop between Transient Pupil Constriction and Facial Attraction.

Contrary to the long-held belief of a close linkage between pupil dilation and attractiveness, we found an early and transient pupil constriction response when participants viewed an attractive face (and the effect of luminance/contrast was controlled). While human participants were making an attractiveness judgment on faces, their pupil constricted more for the more attractive (as-to-be-rated) faces. Further experiments showed that the effect of pupil constriction to attractiveness judgment extended to intrinsically esthetic visual objects such as natural scene images (as well as faces) but not to line-drawing geometric figures. When participants were asked to judge the roundness of faces, pupil constriction still correlated with their attractiveness but not the roundness rating score, indicating the automaticity of the pupil constriction to attractiveness. When pupillary responses were manipulated implicitly by relative background luminance changes (from the prestimulus screen), the facial attractiveness ratings were in accordance with the amount of pupil constriction, which could not be explained solely by simultaneous or sequential luminance contrast. The overall results suggest that pupil constriction not only reflects but, as a part of self-monitoring and attribution mechanisms, also possibly contributes to facial attractiveness implicitly.

Image luminance changes contrast sensitivity in visual cortex

SUMMARYAccurate measures of contrast sensitivity are important for evaluating visual disease progression and for navigation safety. Previous measures suggested that cortical contrast sensitivity was constant across widely different luminance ranges experienced indoors and outdoors. Against this notion, here, we show that luminance range changes contrast sensitivity in both cat and human cortex, and the changes are different for dark and light stimuli. As luminance range increases, contrast sensitivity increases more within cortical pathways signaling lights than those signaling darks. Conversely, when the luminance range is constant, light-dark differences in contrast sensitivity remain relatively constant even if background luminance changes. We show that a Naka-Rushton function modified to include luminance range and light-dark polarity accurately replicates both the statistics of light-dark features in natural scenes and the cortical responses to multiple combinations of contrast and luminance. We conclude that differences in light-dark contrast increase with luminance range and are largest in bright environments.

17.5: Luminance Instability of OLED panels at Various Situations

To decrease tack time during Demura process, images are captured directly after turning on panels or changing patterns and then used to generate compensation data which determines the Demura results. However, the panel's luminance stability in those situations have not been paid enough attention. Seven panels from five different OLED panel producers were tested at various situations which are from turning off to turning on the panel, changing patterns from different gray levels of the same color or from the same gray level but with different colors. Even after the panels were turned on for a while, their luminance is still instable, therefore luminance's stability was also tested. We found that when turning on panels or changing patterns from different colors, the luminance will go up or down 1–5% of the mean of the relatively stable luminance and need 4–30 seconds to get stable. However, when changing patterns among different gray levels but with the same color, there almost no luminance's sudden change at high gray level (above 160) while the luminance goes up or down 0–3% and need half time to get stable at low gray level (32). The results provide a choice to avoid the sudden change of panels' luminance when changing patterns during Demura process while not increasing the tack time so much and also a possible reason that why the Demura results are not good enough. We also found that the luminance instability could be 0–4% at high gray level (RGB192) and 0.3–4.9% at low gray level (RGB32) which should be paid enough attention since the compensation data based on only one image could not be accurate enough if the panels' luminance is not stable.

Magnocellular and Parvocellular Mediated Luminance Contrast Discrimination in Severe Alcohol Use Disorder

Severe alcohol use disorder (SAUD) is associated with widespread cognitive impairments, including low-level visual processing deficits that persist after prolonged abstinence. However, the extent and characteristics of these visual deficits remain largely undetermined, impeding the identification of their underlying mechanisms and influence on higher-order processing. In particular, little work has been conducted to assess the integrity of the magnocellular (MC) and parvocellular (PC) visual pathways, namely the 2 main visual streams that convey information from the retina up to striate, extrastriate, and dorsal/ventral cerebral regions. We investigated achromatic luminance contrast processing mediated by inferred MC and PC pathways in 33 patients with SAUD and 32 matched healthy controls using 2 psychophysical pedestal contrast discrimination tasks that promote responses of inferred MC or PC pathways. We relied on a staircase procedure to assess participants' ability to detect small changes in luminance within an array of 4 gray squares that were either continuously presented (steady pedestal, MC-biased) or briefly flashed (pulsed pedestal, PC-biased). We replicated the expected pattern of MC and PC contrast responses in healthy controls. We found preserved dissociation of MC and PC contrast signatures in SAUD but higher MC-mediated mean contrast discrimination thresholds combined with a steeper PC-mediated contrast discrimination slope compared with healthy controls. These findings indicate altered MC-mediated contrast sensitivity and PC-mediated contrast gain, confirming the presence of early sensory disturbances in individuals with SAUD. Such low-level deficits, while usually overlooked, might influence higher-order abilities (e.g., memory, executive functions) in SAUD by disturbing the "coarse-to-fine" tuning of the visual system, which relies on the distinct functional properties of MC and PC pathways and ensures proper and efficient monitoring of the environment.

A color image watermarking framework for copyright protection of stereo images based on binocular just noticeable difference and LU decomposition

The copyright protection of three-dimensional (3D) content is a matter of interest in artistic and creative works due to the rights of the holder for the distribution of the material. However, although stereo images are widely used for the generation of 3D content, there is a little amount of research focused on copyright protection for this type of image. In this study, a novel invisible and blind color image watermarking framework for protecting the copyright of the stereo images based on Binocular Just Noticeable Difference (BJND) and lower-and-upper (LU) decomposition is proposed. In this framework, a color watermark is encoded to reduce the information. Then, the BJND model is calculated in the R channel of a stereo image, and finally, LU decomposition is applied into the G and B channels to embed and extract a color watermark. The BJND model has demonstrated a remarkable sensitivity comparable with the Human Visual System (HVS) in luminance changes such as the ones presented in stereo images, guaranteeing a good protection performance and a high imperceptibility. The proposed framework was compared with other state-of-the-art techniques, and it has demonstrated better performance and high resistance to attacks of JPEG compression or impulsive and Gaussian noise. Additionally, this novel framework does not affect the generation of the disparity map or the 3D content when the watermarked stereo images are used for their creation.

Testing the adequacy of luminous change descriptors to represent dynamic attributes in outdoor views

Outdoor views are critical for sustaining well-being in urbanized environments, as they increase opportunities for contact with natural and dynamic features. Yet, current view assessment procedures do not investigate the role of dynamic attributes in views. In this study, we evaluated a systematic procedure to test the adequacy of representing dynamic outdoor attributes as a function of lightness changes over time. Using image processing and monitoring techniques, we examined the presence of lightness changes in views in two seasons and as a function of three spatial parameters. In Part 1, we evaluated light variations in 16 distinct view scenes collected in summer (n = 320 intervals). In Part 2, we examined daylight changes in four pairs of identical view scenes collected in summer and fall (n = 80 intervals each). Continuous solar radiation measurements anchored lightness changes values as a function of sky conditions. The results showed the recurrence of lightness changes in views for Part 1 (77%) and Part 2 (75%), suggesting the prevalence of light changes in views across the year. In Part 1, lightness changes in views presented statistical significance in naturalistic conditions and three sky types, yet more data is needed for comparative analysis. In Part 1, the prevalence of Global variation in views was demonstrated. Likewise, two view types (i.e., Roof and Wall) showed a clear frequency of lightness changes under naturalistic conditions (76% and 74%). These outcomes help to sustain the adequacy of lightness change for describing dynamic attributes in views.

Effect of Speech-to-Noise Ratio and Luminance on a Range of Current and Potential Pupil Response Measures to Assess Listening Effort.

In hearing research, pupillometry is an established method of studying listening effort. The focus of this study was to evaluate several pupil measures extracted from the Task-Evoked Pupil Responses (TEPRs) in speech-in-noise test. A range of analysis approaches was applied to extract these pupil measures, namely (a) pupil peak dilation (PPD); (b) mean pupil dilation (MPD); (c) index of pupillary activity; (d) growth curve analysis (GCA); and (e) principal component analysis (PCA). The effect of signal-to-noise ratio (SNR; Data Set A: –20 dB, –10 dB, +5 dB SNR) and luminance (Data Set B: 0.1 cd/m2, 360 cd/m2) on the TEPRs were investigated. Data Sets A and B were recorded during a speech-in-noise test and included TEPRs from 33 and 27 normal-hearing native Dutch speakers, respectively. The main results were as follows: (a) A significant effect of SNR was revealed for all pupil measures extracted in the time domain (PPD, MPD, GCA, PCA); (b) Two time series analysis approaches (GCA, PCA) provided modeled temporal profiles of TEPRs (GCA); and time windows spanning subtasks performed in a speech-in-noise test (PCA); and (c) All pupil measures revealed a significant effect of luminance. In conclusion, multiple pupil measures showed similar effects of SNR, suggesting that effort may be reflected in multiple aspects of TEPR. Moreover, a direct analysis of the pupil time course seems to provide a more holistic view of TEPRs, yet further research is needed to understand and interpret its measures. Further research is also required to find pupil measures less sensitive to changes in luminance.

Маркирование текстовых документов на экране монитора посредством изменения яркости фона в областях межстрочных интервалов

One of the most common ways documents leak is taking a picture of document displayed on the screen. For investigation of such cases data leakage prevention technologies including screen watermarking are used. The article gives short review on the problem of screen shooting watermarking and the existing research results. A novel approach for watermarking text images displayed on the screen is proposed. The watermark is embedded as slight changes in luminance into the interline spacing of marked text. The watermark is designed to be invisible for human eye but still able to be detected by digital camera. An algorithm for extraction of watermark from the screen photo is presented. The extraction algorithm doesn’t need the original image of document for successful extraction. The experimental results show that the approach is robust against screen-cam attacks, that means that the watermark stays persistent after the process of taking a photo of document displayed on the screen. A criterion for watermark message extraction accuracy without knowledge about the original message is proposed. The criterion represents the probability that the watermark was extracted correctly.

Low-contrast Acuity Under Strong Luminance Dynamics and Potential Benefits of Divisive Display Augmented Reality

Abstract Understanding and predicting outdoor visual performance in augmented reality (AR) requires characterizing and modeling vision under strong luminance dynamics, including luminance differences of 10000-to-1 in a single image (high dynamic range, HDR). Classic models of vision, based on displays with 100-to-1 luminance contrast, have limited ability to generalize to HDR environments. An important question is whether low-contrast visibility, potentially useful for titrating saliency for AR applications, is resilient to saccade-induced strong luminance dynamics. The authors developed an HDR display system with up to 100,000-to-1 contrast and assessed how strong luminance dynamics affect low-contrast visual acuity. They show that, immediately following flashes of 25× or 100× luminance, visual acuity is unaffected at 90% letter Weber contrast and only minimally affected at lower letter contrasts (up to +0.20 LogMAR for 10% contrast). The resilience of low-contrast acuity across luminance changes opens up research on divisive display AR (ddAR) to effectively titrate salience under naturalistic HDR luminance.

Hierarchical Bit-Plane Slicing for High Dynamic Range Image Stereo Matching

Due to the recent advances of sensing technologies, high dynamic range (HDR) imaging devices have been developed for the image acquisition of real-world scenes with a wide range of luminance changes. In this article, the hierarchical matching techniques for HDR image pairs are investigated. A bit slicing method is combined with the state-of-the-art stereo matching algorithms for HDR images generated from multiple exposures. Our approach demonstrates that it is possible to use only the most significant 16 bits of the HDR image encoding per pixel to achieve a comparable bad pixel rate on stereo matching. Thus, the computational power and memory constraints can be reduced while benefiting from the HDR images. This makes HDR stereo matching feasible under general resource limited setups. In the experiments, the evaluation and comparison carried out using Middlebury stereo datasets have illustrated the effectiveness of the proposed framework. The source codes are available at: https://github.com/chillwater/HDR_Stereo_Match .

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.

Proton Pump Inhibitors Reduce Duodenal Eosinophilia, Mast Cells, and Permeability in Patients With Functional Dyspepsia

Despite the growing recognition of duodenal alterations in the pathophysiology of functional dyspepsia (FD), the effect and mechanism of proton pump inhibitors (PPIs) or first-line therapy remain unclear. We studied duodenal and systemic alterations in relation to PPI therapy in patients with FD and healthy volunteers (HVs). We performed a prospective interventional study assessing symptoms (Patient Assessment of Gastrointestinal Symptom Severity Index), duodenal alterations, and systemic factors in patients with FD ("FD-starters") and HVs before and after PPI therapy (pantoprazole 40 mg once daily for 4 weeks). Duodenal mucosal eosinophils, mast cells and permeability were quantified. Luminal pH and bile salts were determined in duodenal aspirates. Procedures were also performed in PPI-refractory patients with FD ("FD-stoppers") before and 8 weeks after PPI withdrawal. Between- and within-group changes from baseline and associations with duodenal or systemic factors were analyzed using linear mixed models. The study was completed by 30 HV, 27 FD-starters, and 18 FD-stoppers. Symptoms and duodenal eosinophils, mast cells (all, P < .0001), and paracellular passage (P= .02) were significantly higher in FD-starters vs HVs and reduced with PPI therapy. Symptoms and duodenal immune cells also decreased in FD-stoppers off PPIs. In contrast, immune cells and permeability increased in HVs on PPIs. Dyspeptic symptoms correlated with eosinophils before and during PPI therapy, and increased eosinophils and permeability in HVs on PPIs were associated with changes in bile salts. We provide the first prospective evidence for eosinophil-reducing effects as a therapeutic mechanism of PPIs in FD, with differential effects in HVs pointing to a role of luminal changes. ClinicalTrials.gov, Number: NCT03545243.

BitLight

This paper presents BitLight, a novel paradigm that uses the rapid flashing of a digital light processing (DLP) projector to encode an imperceptible mask temporally that, when sensed by a photodiode, uniquely specifies where the photodiode is located on the projected image. BitLight is inspired by the psychophysical phenomenon that the human visual system (HVS) cannot resolve rapid temporal changes in optical signals, so redundant optical signals could be inserted for tracking with some or little compromise on the original human perceived visual content. BitLight is the first to devise a bit-level temporal encoding to display RGB colors while also embedding tracking signals in a digital fashion. Compared to traditional visible-light-communication (VLC) systems that use frame-level encoding techniques such as luminance changes [10, 25, 26, 32] and alpha channel [16], the bit-level encoding of BitLight makes better use of the ultra-fine temporal division capabilities of DLP projectors to embed a much higher tracking data throughput and thus achieve faster localization speed. With our current prototype hardwares of a low-end microcontroller, cheap photodiodes, and a commercial off-the-shelfDLP projector, evaluation results have demonstrated an average of only 9.5ms to localize the sensor, versus 200ms by a comparison testbed that uses simple frame-level encodings.