Disparity Limit Research Articles

Analytical Derivation of Intersubmodule Active Power Disparity Limits in Modular Multilevel Converter-Based Battery Energy Storage Systems

Due to a dramatic increase in grid-connected renewable energy resources, energy storage systems are interesting and important for future power systems, among which the modular multilevel converter (MMC)-based battery energy storage systems (BESSs) are one of the most modular, efficient, and flexible topologies. Uneven active power distribution among submodules (SMs) in the arms of an MMC-based BESS is necessary for certain applications. The main contribution of this article is to present a general analysis of the inter-SM active power disparity problem which incorporates the inherent operational constraints of the MMC converter. An analytical method to derive inter-SM active power disparity limits is introduced. The proposed analysis can help facilitate the design of MMC-based BESS for applications such as recycled batteries and hybrid battery chemistries, which can both require significant inter-SM active power disparity. The analysis formulates a criteria vector and criterion value that describes whether an MMC-based BESS is capable of supplying demanded output powers while subject to inter-SM active power disparity. Simulation and experimental results are obtained on a single-phase system with varying numbers of SMs per arm, which verifies the feasibility and generality of the proposed analytical method.

Predicting Stereopsis in Macular Degeneration.

Each of our eyes sees a slightly different view of the physical world. Disparity is the small difference in position of features in the retinal images; stereopsis is the percept of depth from disparity. A distance between corresponding features in the retinal images of the two eyes smaller than the "upper disparity limit" yields a percept of depth; distances greater than this limit cause the two unfused monocular features to appear flattened into the fixation plane. This behavioral disparity limit is consistent with neurophysiological estimates of the largest disparity scale in primate, allowing us to relate physiological limits on plausible binocular interactions to separation between retinal locations. Here we test the hypothesis that this upper disparity limit predicts the presence of coarse stereopsis in humans with macular degeneration (MD), which affects the central retina but typically spares the periphery. The pattern of vision loss can be highly asymmetric, such that an intact location in one eye has a corresponding point in the other eye that lies within affected retina. Nevertheless, some individuals with MD have coarse stereopsis that is useful for eye-hand coordination. Our results show that individuals with MD (n = 25, male and female) have coarse stereopsis when the distance between intact retinal locations is less than the behavioral and physiological upper disparity limit at the corresponding eccentricity. Furthermore, for those without stereopsis, we can predict whether they can achieve stereopsis by using alternate retinal loci at further eccentricities whose separation is below the upper disparity limit.SIGNIFICANCE STATEMENT We show that the largest separation between features in the two eyes that yields a percept of depth in humans is related to the largest disparity scale in macaque medial temporal area and to the estimated size of the receptive fields in human depth-sensitive cortical regions. This upper disparity limit also predicts whether individuals with retinal damage due to macular degeneration will have stereopsis. Individuals have stereopsis when the separation between intact retinal locations in the two eyes is smaller than the upper disparity limit measured behaviorally. Our results indicate the importance of the behavioral upper disparity limit as a predictor for stereopsis in populations with retinal damage.

The upper disparity limit increases gradually with eccentricity.

Stereopsis is important for tasks of daily living such as eye-hand coordination. It is best in central vision but is also mediated by the periphery. Previously we have shown that individuals with central-field loss who have residual stereopsis in the periphery perform better at an eye-hand-coordination task when they perform the task binocularly rather than monocularly. Here we seek to determine what sets the limit of stereopsis, defined as the largest disparity that supports the sustained appearance of depth, in the near periphery in healthy individuals. While stereoacuity thresholds increase sharply with eccentricity, Panum's area increases much more slowly. We used a rigorous method to determine the uppermost limit of disparity. At long durations, the two half-images that define a large disparity appear as two isolated targets in the same flat plane; small incremental changes in disparity produce changes in the separation between the half-images, and disparity magnitude can be judged on the basis of separation, like a monocular width judgment. The disparity limit is the point at which the threshold for judging dichoptic separation between the half-images is equal to the monocular width-discrimination threshold. The disparity limit at 10° was a factor of 2–4 times larger than the fovea, regardless of the meridian tested. The increase in the disparity limit with eccentricity was shallow, similar to that of Panum's area. Within this disparity limit, disparity increment thresholds were comparable for foveal and peripheral targets, illustrating the significance and utility of peripheral stereopsis, especially in the absence of foveal stereopsis.

Fundamentals of Presbyopia: visual processing and binocularity in its transformation

BackgroundThe accommodation has considerable interactions with the pupil response, vergence response and binocularity. The transformation of visual reception processing and the changes of the binocular cooperation during the presbyopia development are still poorly studied. So, the regularities of visual system violation in the presbyopia formation need to be characterized. This study aims to reveal the transformation of visual reception processing and to determine the role of disturbances in binocular interactions in presbyopia formation.MethodsThis study included 60 people with emmetropic refraction, uncorrected distance visual acuity 1.0 or higher (decimal scale), normal color perception, without concomitant ophthalmopathology. The first group consisted of 30 people (from 18 to 27 years old) without presbyopia, the second cohort comprised 30 patients (from 45 to 55 years old) with presbyopia. The eyeball anatomy and optics were evaluated using ultrasound biomicroscopy, aberrometry, and pupillometry. The functional state of the visual system was investigated under monocular and binocular conditions. The registration of the disparate fusional reflex limits was performed by the original technic using a diploptic device which facilitated investigation of the binocular interaction under natural conditions without the accommodation response, but with the different vergence load. The disparate fusional reflex was analyzed using the proximal and distal fusion borders, and the convergence and divergence fusion borders. The calculation of the area of binocularity field was performed in cm2.ResultsThe presbyopia formation is characterized by a change in an intraocular anatomy, optics, visual processing, and binocularity. The processes of binocular interaction inhibition make a significant contribution to the misalignment of the visual perception. The modification of the proximal, distal and convergence fusion borders was determined. It was revealed that 87% of the presbyopic patients had binocularity shortage, whereas the reduction of binocularity field area in extreme grade was seen in 6% of cases.ConclusionsThe presbyopia formation is accompanied by a significant reorganization of the visual system activity and by the creation of the new visual processing interactions. These data may be useful in presbyopia surgery.

StereoEditor: controllable stereoscopic display by content retargeting

We report a stereoscopic editing method, named as StereoEditor, to achieve controllable stereoscopic display. By taking content-aware, depth-adaptive and object-selective retargeting into account, the resolution, depth and object of stereoscopic input are simultaneously edited to create flexible stereoscopic output. The retargeting semantics from retinal disparity limits, viewing distance, and object’s scaling factors can be adjusted flexibly to achieve particular stereoscopic display, which can be controlled by user’s preference and practical viewing conditions. Compared with previous methods, our method can achieve a better tradeoff among shape preservation, depth control and object layout, leading to promising viewing experience.

Magnitude, precision, and realism of depth perception in stereoscopic vision

Our perception of depth is substantially enhanced by the fact that we have binocular vision. This provides us with more precise and accurate estimates of depth and an improved qualitative appreciation of the three-dimensional (3D) shapes and positions of objects. We assessed the link between these quantitative and qualitative aspects of 3D vision. Specifically, we wished to determine whether the realism of apparent depth from binocular cues is associated with the magnitude or precision of perceived depth and the degree of binocular fusion. We presented participants with stereograms containing randomly positioned circles and measured how the magnitude, realism, and precision of depth perception varied with the size of the disparities presented. We found that as the size of the disparity increased, the magnitude of perceived depth increased, while the precision with which observers could make depth discrimination judgments decreased. Beyond an initial increase, depth realism decreased with increasing disparity magnitude. This decrease occurred well below the disparity limit required to ensure comfortable viewing.

Size matters: Perceived depth magnitude varies with stimulus height

Both the upper and lower disparity limits for stereopsis vary with the size of the targets. Recently, Tsirlin, Wilcox, and Allison (2012) suggested that perceived depth magnitude from stereopsis might also depend on the vertical extent of a stimulus. To test this hypothesis we compared apparent depth in small discs to depth in long bars with equivalent width and disparity. We used three estimation techniques: a virtual ruler, a touch-sensor (for haptic estimates) and a disparity probe. We found that depth estimates were significantly larger for the bar stimuli than for the disc stimuli for all methods of estimation and different configurations. In a second experiment, we measured perceived depth as a function of the height of the bar and the radius of the disc. Perceived depth increased with increasing bar height and disc radius suggesting that disparity is integrated along the vertical edges. We discuss size–disparity correlation and inter-neural excitatory connections as potential mechanisms that could account for these results.

Size matters: Perceived depth magnitude varies with stimulus height

Both the upper and lower disparity limits for stereopsis vary with the size of the targets. Recently, Tsirlin, Wilcox, and Allison (2012) suggested that perceived depth magnitude from stereopsis might also depend on the vertical extent of a stimulus. To test this hypothesis we compared apparent depth in small discs to depth in long bars with equivalent width and disparity. We used three estimation techniques: a virtual ruler, a touch-sensor (for haptic estimates) and a disparity probe. We found that depth estimates were significantly larger for the bar stimuli than for the disc stimuli for all methods of estimation and different configurations. In a second experiment, we measured perceived depth as a function of the height of the bar and the radius of the disc. Perceived depth increased with increasing bar height and disc radius suggesting that disparity is integrated along the vertical edges. We discuss size-disparity correlation and inter-neural excitatory connections as potential mechanisms that could account for these results.

Clinically Normal Stereopsis Does Not Ensure a Performance Benefit from Stereoscopic 3D Depth Cues

To investigate the effect of manipulating disparity on task performance and viewing comfort, twelve participants were tested on a virtual object precision placement task while viewing a stereoscopic 3D (S3D) display. All participants had normal or corrected-to-normal visual acuity, passed the Titmus stereovision clinical test, and demonstrated normal binocular function, including phorias and binocular fusion ranges. Each participant completed six experimental sessions with different maximum binocular disparity limits. The results for ten of the twelve participants were generally as expected, demonstrating a large performance advantage when S3D cues were provided. The sessions with the larger disparity limits typically resulted in the best performance, and the sessions with no S3D cues the poorest performance. However, one participant demonstrated poorer performance in sessions with smaller disparity limits but improved performance in sessions with the larger disparity limits. Another participant's performance declined whenever any S3D cues were provided. Follow-up testing suggested that the phenomenon of pseudo-stereoanomaly may account for one viewer's atypical performance, while the phenomenon of stereoanomaly might account for the other. Overall, the results demonstrate that a subset of viewers with clinically normal binocular and stereoscopic vision may have difficulty performing depth-related tasks on S3D displays. The possibility of the vergence---accommodation conflict contributing to individual performance differences is also discussed.

Visual comfort in 2D/3D modes of glasses-type stereoscopic displays

In this study, we compared visual comfort in 2D/3D modes of the pattern retarder (PR) and shutter glasses (SG) stereoscopic displays by changing viewing factors and image contents. The viewing factors include ambient illuminance/monitor luminance/background luminance and image contents mainly are determined with different disparity limits. The degrees of 2D/3D visual comfort were investigated by using various combinations of ambient illuminance, monitor luminance, background luminance, and disparity limit. A series of psychological experiments were also performed to compare 2D and 3D viewing experiences for the passive PR and active SG stereoscopic displays and to discover more comfortable conditions under various variable combinations. The experiment results show that the various variable combinations affecting visual comfort in the passive PR and active SG stereoscopic displays were significantly different. Finally, we suggest more comfortable conditions of viewing 2D and 3D images for the PR and SG stereoscopic displays.

Failure analysis of engineering structures in undergraduate courses using optimization

ABSTRACTIn the design process for engineering structures, it is often of interest to determine the largest magnitude of a given form of load that can be applied on a structure before causing failure. This gives the factor of safety against failure. Determining the factor of safety entails analysis of a structure on the verge of failure, and is known as limit analysis. It is well known that limit analysis can be formulated as a constrained optimization problem. With robust computational tools for optimization having become readily available, it is possible to introduce the optimization‐based approach to limit analysis at various stages in the undergraduate civil engineering curriculum. In this article, we present three instances of limit analysis using an optimization‐based approach from (i) a sophomore level Statics course, (ii) a junior level Structural Analysis course, and (iii) a senior level Advanced Solid Mechanics course. These are based on materials presented by the author in undergraduate mechanics courses at the University of Colorado at Boulder. In each case, we develop a mathematical formulation and implement the computations in MATLAB. We use two optimization tools, one from the MATLAB Optimization Toolbox and the other called SeDuMi. Classroom experience has shown that the optimization‐based approach helps students recognize the underlying thread in seemingly disparate limit analysis problems. © 2011 Wiley Periodicals, Inc. Comput Appl Eng Educ 22:297–308, 2014; View this article online at wileyonlinelibrary.com/journal/cae; DOI 10.1002/cae.20555

Stereo and motion Dmax in infants

These experiments compared the maximum displacement and disparity limits (Dmax) for apparent motion and stereopsis in random-dot displays in adult and 12-28 week-old infant subjects. Both stereo and motion Dmax increased during development, from about 0.3 deg in the youngest infants to 2 deg in adults. Some of the younger infants (12-14 weeks) did not give a stereo threshold, probably because stereopsis had not yet developed; but otherwise, the values of Dmax in the two domains were close to each other throughout the age range. These results suggest that both stereo and motion Dmax are limited by some common factor. Possible factors include receptive field sizes and internal noise. Simulations in which these were varied showed that while changes in both could contribute to the development of Dmax, only an increase in receptive field size can fully account for the rise in Dmax with age.

Stereoscopic human interfaces

This article focuses on the use of stereoscopic video interfaces for telerobotics. Topics concerning human visual perception, binocular image capturing, and stereoscopic devices are described. There is a wide variety of video interfaces for telerobotic systems. Choosing the best video interface depends on the telerobotic application requirements. Simple monoscopic cameras are good enough for watching remote robot movements or for teleprogramming a sequence of commands. However, when operators seek precise robot guidance or wish to manipulate objects, a better perception of the remote environment must be achieved, for which more advanced visual interfaces are required. This implies a higher degree of telepresence, and, therefore, the most suitable visual interface has to be chosen. The aim of this article is to describe the two main aspects using stereoscopic interfaces: the capture of binocular video images, according to the disparity limits in human perception and the proper selection of the visualization interface for stereoscopic images.

Upper disparity limit after LASIK

We evaluate the effect of the emmetropization technique LASIK (laser-assisted in situ keratomileusis) on stereoscopic vision. For this, we used a mirror stereoscope to measure the upper disparity limit D(max) before (with best correction) and after LASIK for 30 patients. The results show that the upper disparity limit declines from 41.1 min of arc on average to 31.3 min of arc after LASIK, being significant in 83% of the patients. This deterioration is significantly correlated with an increase in the postsurgical interocular differences in higher-order aberrations, corneal asphericity, and presurgical anisometropia. New ablation algorithms should minimize interocular differences in order to improve binocular visual performance.

Binocular Disparity Limit in Three-dimensional Display Systems

In three-dimensional display systems, binocular disparities must be limited within a certain fusional area, called as “Panum's fusional area. Otherwise, too larger disparity could cause double view or serious eye fatigue. However, the measurements about Panum's fusional area in the previous studies focused only on the horizontal and vertical meridian of retina. For fully measuring the Panum's fusional area in more directions, we took the measurements of the limits of Panum's fusional area, in sixteen different directions from 0 degree to 360 degrees by a step of 22.5 degrees in the fovea. It was found that the horizontal disparity limit of binocular fusional area is about 32-38.4 min of arc and the vertical limit is about 19.2-24 min of arc. The disparity limits of binocular fusional area are approximately symmetrical about horizontal meridian. However, the disparity limits are not symmetrical about vertical meridian; the nasalward disparity limits are obviously larger than temporalward disparity limits. Moreover, in the nasal side of retina, the disparity limits decrease in a monotonic fashion, and in the temporal side, however, the disparity limits have no obvious difference.

Disparity Limit for Binocular Fusion in Fovea

In the human visual system, binocular disparity limit must be limited within a certain fusional area, called “Panum's fusional area”; otherwise, unsuitable disparity could cause double vision. The previous studies on Panum's fusional area have focused only on the horizontal and vertical meridians. In order to measure this area in more directions, we determined its limits in 16 different directions from 0 to 360° at 22.5° steps in fovea. It was found that: (1) the horizontal disparity limit (about 32-40 arcmin) is larger than the vertical limit (about 19.2–25.6 arcmin); (2) Panum's fusional area is approximately symmetrical around the horizontal meridian; (3) however, it is not symmetrical around the vertical meridian; the nasalward disparity limits are obviously larger than temporalward disparity limits; (4) therefore, the form of Panum's fusional area in fovea could be suggested to be an ellipse off-centered toward the nasal side on the horizontal meridian.

Changing Binocular Fusional Area with Retinal Shift in Binocular Vision

In three-dimensional display systems, binocular disparity must be limited within a certain area, called as “Panum's fusional area”. Otherwise, unsuitable binocular disparity can cause double view or eye fatigue. In this study, we measured the binocular fusional areas in central vision, in the case of peripheral visions of retinal eccentricity of 3 degrees and 6 degrees on horizontal meridian, respectively, using a three-dimensional display. The following results were obtained, (1) in each experiment in central vision, peripheral vision of 3 degrees and 6 degrees, the disparity limit in horizontal meridian is larger than that in vertical meridian; the binocular fusional area is symmetrical about horizontal meridian and is not symmetrical about vertical meridian; the nasalward disparity limits are larger than the temporalward disparity limits; therefore, the form of the binocular fusional area is considered as an ellipse off-centered toward the nasal side on the horizontal meridian. (2) The size of the binocular fusional areas increases with the increase of retinal eccentricity, and the increase of disparity limit on horizontal meridian is faster than that on vertical meridian.

Change of Binocular Disparity Limits in Retinal Fovea

Change of Binocular Disparity Limits in Retinal Fovea

Analysis of Human Binocular Fusional Area in Retinal Fovea

In three-dimensional display systems, binocular disparities must be limited within a certain fusional area, called as “Panum's fusional area”, otherwise too large disparity could cause double view or serious eye tiresome. In this study, a three-dimensional display device was employed with a constant stimuli method to measure the disparity limits of the Panum's fusional area in sixteen different directions from 0 degree to 360 degrees by a step of 22.5 degrees in the retinal fovea. The following results were obtained: (1) the horizontal disparity limit of binocular fusional area is about 32-40min of arc and the vertical limit is about 19.2-25.6min of arc. (2) The disparity limits of binocular fusional area are approximatively symmetrical about horizontal meridian. (3) The disparity limits are not symmetrical about vertical meridian, and the nasalward disparity limits are obviously larger than the temporalward disparity limits. (4) In the nasal side of retina, the disparity limits decrease in a monotonic fashion and in the temporal side, however, the disparity limits have no obvious difference.

Binocular Disparity Limits in Three-dimensional Display Systems

Binocular Disparity Limits in Three-dimensional Display Systems