Luminance Difference Research Articles

Streamgraph Generation with Enhanced Readability

<p indent=0mm>In order to enhance the readability of the streamgraph and assist users identify the target layer more efficiently, a method to optimize the color assignment and label layout in streamgraph based on the existing layout of streamgraph is proposed. First, the color assignment evaluation function of the streamgraph is established according to the layout, and then the color assignment result is got which can maximize the color difference between layers as well as the luminance difference between the background color and layers through genetic algorithm. Secondly, the sliding window is used to traverse each layer, and the tilt angle of each label is automatically adjusted by least squares to fit the shape change of each layer. Then the label layout results are obtained with adaptive label size. The method is compared with existing methods on multiple real and simulated datasets through user study and quantitative evaluation. The results show that the method can significantly improve the recognition accuracy, reduce the recognition time of the layers, and increase the label size at the same time, which means it can improve the readability of the streamgraph effectively.

The Confetti illusion

The Munker illusion, which produces two apparently different hues from a base color, can be extended to multiple apparent colors. By having foreground stripes in more than two colors, it is possible to create multiple foreground colors that lead to multiple apparent hues in the base objects. All of these apparently different colors are due to color assimilation rather than to differences in luminance, as in the Munker-White illusion. This technique works well for three colors and can be extended to four and even six colors.

The magnitude of monocular light attenuation required to elicit the Pulfrich illusion

In the Pulfrich illusion, the depth of a moving object is misperceived due to induced retinal disparity and/or interocular velocity differences arising from differences in luminance, contrast, or spatial frequency between the two eyes. These effects have been shown to occur both for visual deficits and for optical corrections that introduce significant binocular differences between the retinal images. However, it remains unknown to what extent the illusion might arise given normal variation between the eyes, such as natural interocular variation in pupil diameter (anisocoria). To assess this, we examined the threshold interocular retinal illuminance difference required to experience illusory depth in two random-dot fields moving in opposite directions in 24 normally-sighted observers with dilated pupils. Interocular difference in retinal illuminance was induced by placing neutral density filters of different intensities before the left eye. A minority of subjects (n = 8) did not provide meaningful data on changes in the experience of illusory depth with interocular difference in retinal illuminance and four subjects showed biases >±10% from the 50% point of subjective equality in the psychometric function. For the remaining 12 participants, the retinal illuminance had to differ by approximately 40% for the depth between the planes to become visible at threshold levels. This difference was approximately constant over a range of absolute luminance levels from 10 to 80 cd/m2. Our results suggest that while motion-in-depth illusions due to interocular differences in retinal illuminance may be pronounced in certain ophthalmic diseases or following certain optical interventions, it is unlikely to be manifest as a result of normal interocular variations in retinal illuminance. Further, our results also point towards the existence of substantial individual differences in the experience of what is otherwise thought of as a readily appreciable motion-in-depth illusion.

Configurations of tunnel deceleration area

The deceleration area of the tunnel has always been the place where accidents occur frequently. Recently published statistics on tunnel accidents showed that 42 percent of which are rear-end collisions. The main reason lies on the luminance difference between the inside and the outside parts of the tunnel. The inside part of the tunnel is much darker than that of the outside part, which results in a “sight shock” and shortage of clear sight for drivers at the tunnel portal. If the tunnel deceleration area is not long enough and the vehicle is at a high speed, rear-end collisions will most likely occur at this area. Therefore, it is important to design the deceleration area of the tunnel in order to avoid rear-end collisions. This paper explains the cause of rear-end collision at deceleration area from the principles of physics and physiology. The mathematical relations among the speed, time and distance of trucks and cars entering the tunnel are given from the mathematical point of view. Finally, this paper puts forward the design idea and reasonable suggestions for the configuration of tunnel deceleration area.

Association of hemodynamic factors and progressive aortic dilatation following type A aortic dissection surgical repair

Type A aortic dissection (TAAD) involves the ascending aorta or the arch. Acute TAAD usually requires urgent replacement of the ascending aorta. However, a subset of these patients develops aortic rupture due to further dilatation of the residual dissected aorta. There is currently no reliable means to predict the risk of dilatation following TAAD repair. In this study, we performed a comprehensive morphological and hemodynamic analysis for patients with and without progressive aortic dilatation following surgical replacement of the ascending aorta. Patient-specific models of repaired TAAD were reconstructed from post-surgery computed tomography images for detailed computational fluid dynamic analysis. Geometric and hemodynamic parameters were evaluated and compared between patients with stable aortic diameters (N = 9) and those with aortic dilatation (N = 8). Our results showed that the number of re-entry tears and true/false lumen pressure difference were significantly different between the two groups. Patients with progressive aortic dilatation had higher luminal pressure difference (6.7 [4.6, 10.9] vs. 0.9 [0.5, 2.3] mmHg; P = 0.001) and fewer re-entry tears (1.5 [1, 2.8] vs. 5 [3.3, 7.5]; P = 0.02) compared to patients with stable aortic diameters, suggesting that these factors may serve as potential predictors of aneurysmal dilatation following surgical repair of TAAD.

Segmenting surface boundaries using luminance cues

Segmenting scenes into distinct surfaces is a basic visual perception task, and luminance differences between adjacent surfaces often provide an important segmentation cue. However, mean luminance differences between two surfaces may exist without any sharp change in albedo at their boundary, but rather from differences in the proportion of small light and dark areas within each surface, e.g. texture elements, which we refer to as a luminance texture boundary. Here we investigate the performance of human observers segmenting luminance texture boundaries. We demonstrate that a simple model involving a single stage of filtering cannot explain observer performance, unless it incorporates contrast normalization. Performing additional experiments in which observers segment luminance texture boundaries while ignoring super-imposed luminance step boundaries, we demonstrate that the one-stage model, even with contrast normalization, cannot explain performance. We then present a Filter–Rectify–Filter model positing two cascaded stages of filtering, which fits our data well, and explains observers' ability to segment luminance texture boundary stimuli in the presence of interfering luminance step boundaries. We propose that such computations may be useful for boundary segmentation in natural scenes, where shadows often give rise to luminance step edges which do not correspond to surface boundaries.

Face Antispoofing Method Using Color Texture Segmentation on FPGA

User authentication for accurate biometric systems is becoming necessary in modern real-world applications. Authentication systems based on biometric identifiers such as faces and fingerprints are being applied in a variety of fields in preference over existing password input methods. Face imaging is the most widely used biometric identifier because the registration and authentication process is noncontact and concise. However, it is comparatively easy to acquire face images using SNS, etc., and there is a problem of forgery via photos and videos. To solve this problem, much research on face spoofing detection has been conducted. In this paper, we propose a method for face spoofing detection based on convolution neural networks using the color and texture information of face images. The color-texture information combined with luminance and color difference channels is analyzed using a local binary pattern descriptor. Color-texture information is analyzed using the Cb, S, and V bands in the color spaces. The CASIA-FASD dataset was used to verify the proposed scheme. The proposed scheme showed better performance than state-of-the-art methods developed in previous studies. Considering the AI FPGA board, the performance of existing methods was evaluated and compared with the method proposed herein. Based on these results, it was confirmed that the proposed method can be effectively implemented in edge environments.

Decoding visual colour from scalp electroencephalography measurements

Recent advances have made it possible to decode various aspects of visually presented stimuli from patterns of scalp EEG measurements. As of recently, such multivariate methods have been commonly used to decode visual-spatial features such as location, orientation, or spatial frequency. In the current study, we show that it is also possible to track visual colour processing by using Linear Discriminant Analysis on patterns of EEG activity. Building on other recent demonstrations, we show that colour decoding: (1) reflects sensory qualities (as opposed to, for example, verbal labelling) with a prominent contribution from posterior electrodes contralateral to the stimulus, (2) conforms to a parametric coding space, (3) is possible in multi-item displays, and (4) is comparable in magnitude to the decoding of visual stimulus orientation. Through subsampling our data, we also provide an estimate of the approximate number of trials and participants required for robust decoding. Finally, we show that while colour decoding can be sensitive to subtle differences in luminance, our colour decoding results are primarily driven by measured colour differences between stimuli. Colour decoding opens a relevant new dimension in which to track visual processing using scalp EEG measurements, while bypassing potential confounds associated with decoding approaches that focus on spatial features.

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.

Effect of bright and shade, and luminance difference of defect on defect detection in appearance inspection utilizing peripheral vision

This study considers the effect of bright and shade, and luminance difference of defects on defect detection in appearance inspection utilizing peripheral vision experimentally. Specifically, bright and shade of defect, luminance difference of defect, surface luminance of defect (evaluation index of the difficulty of defect detection, which was proposed in the previous study), and location of defect are designed as experimental factors, and their effects on defect detection rate are evaluated. As a result, it is clarified that the defect detection rate of the shade defects is lower than that of the bright defects, even if the surface luminance is at an identical level. It is also clarified that the defect detection rate of the luminance difference of 10 cd/m2 becomes lower even if the surface luminance is at an identical level. Furthermore, these two trends are particularly remarkable for defects detected in the peripheral vision. Based on the results, in actual appearance inspection utilizing peripheral vision, it is necessary to take measures to detect the shade defects and/or the luminance difference of approximately 10 cd/m2.

Suppression of non-radiative recombination to improve performance of colloidal quantum-dot LEDs with a Cs2CO3 solution treatment

We report a five-fold luminance increase of green-light-emitting CdSe@ZnS quantum-dot LEDs (QLEDs) in response to treatment with a 2-ethoxyethanol solution of cesium carbonate (Cs2CO3). The maximum luminous yield of Cs2CO3-treated QLED is as high as 3.41 cd A−1 at 6.4 V. To elucidate device-performance improvement, we model measured currents as the sum of radiative and non-radiative recombination components, which are respectively represented by modified Shockley equations. Variations in model parameters show that a shift in Fermi level, reduction of barrier heights, and passivation of mid-gap defect states are the main results of Cs2CO3 treatment. In spite of a large luminance difference, light-extraction efficiency remains the same at 9% regardless of Cs2CO3 treatment because of the similarity in optical structures.

Binocular Suppression in the Macaque Lateral Geniculate Nucleus Reveals Early Competitive Interactions between the Eyes.

The lateral geniculate nucleus (LGN) of the dorsal thalamus is the primary recipient of the two eyes’ outputs. Most LGN neurons are monocular in that they are activated by visual stimulation through only one (dominant) eye. However, there are both intrinsic connections and inputs from binocular structures to the LGN that could provide these neurons with signals originating from the other (non-dominant) eye. Indeed, previous work introducing luminance differences across the eyes or using a single-contrast stimulus showed binocular modulation for single unit activity in anesthetized macaques and multiunit activity in awake macaques. Here, we sought to determine the influence of contrast viewed by both the non-dominant and dominant eyes on LGN single-unit responses in awake macaques. To do this, we adjusted each eye’s signal strength by independently varying the contrast of stimuli presented to the two eyes. Specifically, we recorded LGN single unit spiking activity in two awake macaques while they viewed drifting gratings of varying contrast. We found that LGN neurons of all types [parvocellular (P), magnocellular (M), and koniocellular (K)] were significantly suppressed when stimuli were presented at low contrast to the dominant eye and at high contrast to the non-dominant eye. Further, the inputs of the two eyes showed antagonistic interaction, whereby the magnitude of binocular suppression diminished with high contrast in the dominant eye, or low contrast in the non-dominant eye. These results suggest that the LGN represents a site of precortical binocular processing involved in resolving discrepant contrast differences between the eyes.

Pupillary dilation elicited by attending to two disks with different luminance.

Pupils become smaller when people attend to a bright disk as compared to a dark disk. However, people can divide their attention into several distinct positions, which is referred to as divided attention, and pupillary responses under such conditions have not been investigated. In this study, we examined how pupils would respond when people attended to two disks presented at two distinct positions by conducting three experiments. We found that the pupillary response when attending to two disks with different luminance was larger than when attending to a single brighter disk and was comparable to that when attending to a single darker disk, whereas the pupillary response when attending to two disks with identical luminance was not larger than when attending to a single disk (irrespective of the disk luminance). Furthermore, we found that the magnitude of pupillary dilation was determined by the magnitude of the luminance difference between two disks. These results make a useful contribution to the literature on human pupillary responses.

Influence of Difference in Luminance between Traffic Lane Dividing Lines and Road Surface on Detection Performance of Lane Departure Warning System

Influence of Difference in Luminance between Traffic Lane Dividing Lines and Road Surface on Detection Performance of Lane Departure Warning System

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.

Perceptual change-of-mind decisions are sensitive to absolute evidence magnitude

To navigate the world safely, we often need to rapidly ‘change our mind’ about decisions. Current models assume that initial decisions and change-of-mind decisions draw upon common sources of sensory evidence. In two-choice scenarios, this evidence may be ‘relative’ or ‘absolute’. For example, when judging which of two objects is the brightest, the luminance difference and luminance ratio between the two objects are sources of ‘relative’ evidence, which are invariant across additive and multiplicative luminance changes. Conversely, the overall luminance of the two objects combined is a source of ‘absolute’ evidence, which necessarily varies across symmetric luminance manipulations. Previous studies have shown that initial decisions are sensitive to both relative and absolute evidence; however, it is unknown whether change-of-mind decisions are sensitive to absolute evidence. Here, we investigated this question across two experiments. In each experiment participants indicated which of two flickering greyscale squares was brightest. Following an initial decision, the stimuli remained on screen for a brief period and participants could change their response. To investigate the effect of absolute evidence, the overall luminance of the two squares was varied whilst either the luminance difference (Experiment 1) or luminance ratio (Experiment 2) was held constant. In both experiments we found that increases in absolute evidence led to faster, less accurate initial responses and slower changes of mind. Change-of-mind accuracy decreased when the luminance difference was held constant, but remained unchanged when the luminance ratio was fixed. We show that the three existing change-of-mind models cannot account for our findings. We then fit three alternative models, previously used to account for the effect of absolute evidence on one-off decisions, to the data. A leaky competing accumulator model best accounted for the changes in behaviour across absolute evidence conditions – suggesting an important role for input-dependent leak in explaining perceptual changes of mind.

A dichoptic presentation device and a method for measuring binocular temporal function in the visual system

Recent studies highlight the importance of the temporal domain in visual processing. Critical Flicker Frequency (CFF), the frequency at which a flickering light is perceived as continuous, is a widely used measure for evaluating visual temporal processing. Another important issue to investigate is the cortical interactions arising between the flicker stimuli of both eyes.This paper presents a robust and reliable dichoptic tool for evaluating the CFF threshold in both eyes. This system is based on an analog output device used to independently drive two LEDs through a custom-written MATLAB code (using a laptop PC) for eliciting sinusoidal flickering stimuli and for psychophysically measuring the perceived CFF threshold. The luminance and phases of each LED are individually controlled, enabling the investigation of the effect of phase and luminance differences on binocular summation in subjects with different ocular pathologies. Experiments were designed to evaluate the CFF threshold through a psychophysical test, based on a discrimination task with a stimulus duration of 1 s, based on a temporal alternative forced-choice paradigm. The target stimulus temporal features were modulated using the staircase method. Subjects were requested to discriminate between a target stimulus (a flickering light at various frequencies) and a flickering light at a frequency of 120 Hz, which is significantly higher than the CFF in humans; therefore, it is perceived as constant.One of the main advantages of the introduced dichoptic presentation system is that it enables the visual temporal performance to be measured under both monocular and binocular conditions where phenomena such as temporal binocular summation (BS) can be evaluated. Moreover, the system offers great flexibility by introducing a stimulus phase shift, which enables studying how stimulus timing affects the temporal function at millisecond scale resolution. Our results confirm that no crosstalk exists between the eyes and that the system can reliably separate the stimuli presented to the eyes. Using this set-up, we observed the binocular summation of CFF for low target luminance levels. The CFF was significantly (p = 0.011) higher (5.2%) under binocular compared with monocular viewing conditions. More importantly, introducing an inter - ocular phase shift reduced the binocular CFF in normally sighted subjects. Finally, in amblyopic subjects the amblyopic eye showed a decrease of 3.9 Hz (15%) in CFF, compared with the fellow eye (p = 0.001).The ability to assess binocular temporal performance using a dichoptic display can shed light on visual temporal performance in general, and on binocular temporal summation processes in particular, both for subjects with normal binocular vision and for subjects with impaired binocular vision (e.g., amblyopic subjects). Furthermore, such a presentation set-up may facilitate the development of training paradigms aimed at improving binocular vision performance.In this paper we describe the system and methods in detail and provide all necessary computer code and other details that will enable an easy and quick adaptation of the method by scientists interested in studying the temporal resolution of the visual system in general, and in studying inter-ocular differences or interactions in particular.

Prediction of Tumor Temperature in Regional Hyperthermia by Using LED Luminance

Hyperthermia is used to destroy tumors by generating heat in the body (40–45 °C). In particular, regional hyperthermia entails intense heating of tumors rather than raising the temperature of the body. In regional hyperthermia, the prediction of the tumor temperature before treatment is essential to ensure treatment efficiency and patient safety. The goal of this study is to predict the temperature of tumors in regional hyperthermia by using a light emitting diode (LED). LED luminance shows a linear relationship with current above a certain voltage. Thus, the temperature may be predicted via LED luminance based on these electrical characteristics, Special Absorption Rate (SAR), and Pennes’ Bio-heat Transfer Equation. LED was located in the agar phantom at the same intervals to measure the luminance, and measure temperature at same spot using thermometer and well verified using a commercialized simulation program (Sim4Life). Within the range of electrode size, the difference in luminance between the predicted and the measured temperatures was within 2.5%. In addition, the difference between the predicted temperature and the result of the simulation program was within 1.5%. In this study, the tumor temperature in regional hyperthermia was predicted using LED luminance to ensure treatment accuracy and patient safety. This study showed the possibility of temperature prediction based on LED luminance.

3D computational modeling and perceptual analysis of kinetic depth effects

Humans have the ability to perceive kinetic depth effects, i.e., to perceived 3D shapes from 2D projections of rotating 3D objects. This process is based on a variety of visual cues such as lighting and shading effects. However, when such cues are weak or missing, perception can become faulty, as demonstrated by the famous silhouette illusion example of the spinning dancer. Inspired by this, we establish objective and subjective evaluation models of rotated 3D objects by taking their projected 2D images as input. We investigate five different cues: ambient luminance, shading, rotation speed, perspective, and color difference between the objects and background. In the objective evaluation model, we first apply 3D reconstruction algorithms to obtain an objective reconstruction quality metric, and then use quadratic stepwise regression analysis to determine weights of depth cues to represent the reconstruction quality. In the subjective evaluation model, we use a comprehensive user study to reveal correlations with reaction time and accuracy, rotation speed, and perspective. The two evaluation models are generally consistent, and potentially of benefit to inter-disciplinary research into visual perception and 3D reconstruction.

Instantaneous Art? Investigating Frank Stella’s Moroccan Paintings with a Short-Exposure Experiment

In his search to create ‘instantaneously capturable’ paintings, Frank Stella started to use Day-Glo alkyd paints as a vehicle to communicate his simple, striped designs. Up till now, art criticism has neglected the visual impact of these fluorescent colours on this concept of ‘instantaneous art’. By presenting participants with Stella’s designs (fluorescent and conventional variants) for short presentation times (8 to 12 ms), we aimed to find out whether fluorescent colour combinations are seen faster (i.e., yield better performance in identifying the specific design) than their conventional counterparts. In general, participants were very good in identifying the correct design among distractors, which means that the pattern and colour combinations based on Stella’s work do seem to be ‘instantaneously capturable’. However, Stella’s formula for ‘instantaneous’ paintings is not identical for the different combinations. When exploring fluorescence in combination with other aspects of the design (colour and pattern), we found two effects that seemed to predict performance. First, performance seemed to depend on specific design patterns. Second, fluorescence seemed to interact with specific colour combinations in predicting performance. The red/yellow designs yielded better performance for the fluorescent variants, while the opposite was found for the green/orange designs. Contrast differences in luminance between the two colours of each colour combination might explain part of the results. On the other hand, the effect of fluorescent colours might have been watered down by the confusion between the hand-printed fluorescent colours and the computer display used for the identification task, which only showed conventional colours.