Stereoscopic Depth Perception Research Articles

Vision-based collective motion: A locust-inspired reductionist model.

Naturally occurring collective motion is a fascinating phenomenon in which swarming individuals aggregate and coordinate their motion. Many theoretical models of swarming assume idealized, perfect perceptual capabilities, and ignore the underlying perception processes, particularly for agents relying on visual perception. Specifically, biological vision in many swarming animals, such as locusts, utilizes monocular non-stereoscopic vision, which prevents perfect acquisition of distances and velocities. Moreover, swarming peers can visually occlude each other, further introducing estimation errors. In this study, we explore necessary conditions for the emergence of ordered collective motion under restricted conditions, using non-stereoscopic, monocular vision. We present a model of vision-based collective motion for locust-like agents: elongated shape, omni-directional visual sensor parallel to the horizontal plane, and lacking stereoscopic depth perception. The model addresses (i) the non-stereoscopic estimation of distance and velocity, (ii) the presence of occlusions in the visual field. We consider and compare three strategies that an agent may use to interpret partially-occluded visual information at the cost of the computational complexity required for the visual perception processes. Computer-simulated experiments conducted in various geometrical environments (toroidal, corridor, and ring-shaped arenas) demonstrate that the models can result in an ordered or near-ordered state. At the same time, they differ in the rate at which order is achieved. Moreover, the results are sensitive to the elongation of the agents. Experiments in geometrically constrained environments reveal differences between the models and elucidate possible tradeoffs in using them to control swarming agents. These suggest avenues for further study in biology and robotics.

Revealing the Concealed: Alternatives to Random Dots for Stereograms.

Investigations of stereoscopic depth perception were transformed via the use of computer-generated random-dot stereograms in the 1960s. They realized Wheatstone's wish of demonstrating binocular depth without monocular object recognition, and they have been the dominant stimulus for studying stereopsis since then. Alternative carrier patterns to random dots, based on graphics, photographs, and their combinations, are presented as anaglyphs and for free fusion. A wider range of concealed patterns can be revealed with these alternatives, and presenting them as anaglyphs can yield patterns that have visual appeal independent of the depth they conceal.

Poster Session: Visual System Assessment for Predicting a Transition to Psychosis.

Visual system assessments are seldom regarded as a viable way to predict a future psychotic disorder. Here, we argue that may be a missed opportunity. From a large literature, we identify a set of visual tests that have distinguished individuals prior to or near the first psychotic episode or that have shown group differences independently of illness duration. Such tests have revealed moderate-to-large patient differences unexplainable by medication or generalized deficits. For example, self-reported visual perceptual distortions have already longitudinally predicted impending psychosis in large samples. Possibly predictive psychophysical tests include contrast sensitivity, backward masking, collinear facilitation, stereoscopic depth perception, contour integration, visual shape completion, and restricted fixational patterns during free viewing. Possible brain based markers include visual thalamo-cortical hyperconnectivity, decreased gamma band power during visual detection, and reduced occipital P1 amplitudes (EEG) during passive viewing. Promising retinal markers include reduced cone a- and b-wave amplitudes and photopic negative response (ERG). The foregoing assessments are often brief, well-tolerated, simple to administer, and well-described mechanistically. Across all major levels of analysis-from phenomenology to behavior to brain and retinal functioning-visual system assessment could help identify individuals who go on to develop a psychotic disorder.

21.1: Invited Paper: EEG‐based comparative measurement of visual fatigue caused by stereoscopic depth perception

In this study, we investigated the influence of stereoscopic depth on visual fatigue based on subjective and EEG measurement. 19 channels of EEG data of 17 subjects before and after watching 3D movie with different depth ranges were recorded, and the power of δ, θ, α, β, power spectral parameters (gravity frequency, power spectral entropy) were calculated and analyzed. The results showed that visual fatigue caused by 3D enhanced movies with larger negative disparity was more significantly severe than that of 3D normal movies.

Binocular portraiture

Pictorial portraits are viewed with two eyes despite the fact that they are mostly monocular: they have been produced from a single viewpoint (either by painters or photographers). The differences between the images on each eye are a consequence of the separation between them rather than differences in two pictorial images. Viewing with two eyes detracts from the monocular cues to depth within the singular portrait because of information for the flatness of the pictorial surface. Binocular portraits, on the other hand, incorporate differences between two pictorial images producing perceptual effects that cannot be seen by a single eye alone. The differences can consist of small disparities that yield stereoscopic depth or large ones that produce binocular rivalry. Binocular portraits require viewing with a stereoscope, many varieties of which exist. Those shown here are anaglyphs which can be observed through red/cyan filters. They are not conventional stereoscopic portraits where the sitter is imaged from two slightly different locations. Rather, the binocular processes of cooperation (stereoscopic depth perception) and competition (binocular rivalry) are manipulated in the binocular portraits. The subjects shown in the anaglyphic portraits have been involved in the science and art of binocular vision.

Context-based modulations of 3D vision are expertise dependent.

An object's identity can influence depth-position judgments. The mechanistic underpinnings underlying this phenomenon are largely unknown. Here, we asked whether context-dependent modulations of stereoscopic depth perception are expertise dependent. In 2 experiments, we tested whether training that attaches meaning (i.e. classification labels) to otherwise novel, stereoscopically presented objects changes observers' sensitivity for judging their depth position. In Experiment 1, observers were randomly assigned to 3 groups: a Greeble-classification training group, an orientation-discrimination training group, or a no-training group, and were tested on their stereoscopic depth sensitivity before and after training. In Experiment 2, participants were tested before and after training while fMRI responses were concurrently imaged. Behaviorally, stereoscopic performance was significantly better following Greeble-classification (but not orientation-discrimination, or no-) training. Using the fMRI data, we trained support vector machines to predict whether the data were from the pre- or post-training sessions. Results indicated that classification accuracies in V4 were higher for the Greeble-classification group as compared with the orientation-discrimination group for which accuracies were at chance level. Furthermore, classification accuracies in V4 were negatively correlated with response times for Greeble identification. We speculate that V4 is implicated in an expertise-dependent, object-tuning manner that allows it to better guide stereoscopic depth retrieval.

Stereo Dense Scene Reconstruction and Accurate Localization for Learning-Based Navigation of Laparoscope in Minimally Invasive Surgery.

The computation of anatomical information and laparoscope position is a fundamental block of surgical navigation in Minimally Invasive Surgery (MIS). Recovering a dense 3D structure of surgical scene using visual cues remains a challenge, and the online laparoscopic tracking primarily relies on external sensors, which increases system complexity. Here, we propose a learning-driven framework, in which an image-guided laparoscopic localization with 3D reconstructions of anatomical structures is obtained. To reconstruct the structure of the whole surgical environment, we first fine-tune a learning-based stereoscopic depth perception method, which is robust to texture-less and variant soft tissues, for depth estimation. Then, we develop a dense reconstruction algorithm to represent the scene by surfels, estimate the laparoscope poses and fuse the depth into a unified reference coordinate for tissue reconstruction. To estimate poses of new laparoscope views, we achieve a coarse-to-fine localization method, which incorporates our reconstructed model. We evaluate the reconstruction method and the localization module on three datasets, namely, the stereo correspondence and reconstruction of endoscopic data (SCARED), the ex-vivo data collected with Universal Robot (UR) and Karl Storz Laparoscope, and the in-vivo DaVinci robotic surgery dataset, where the reconstructed structures have rich details of surface texture with an error under 1.71 mm and the localization module can accurately track the laparoscope with images as input. Experimental results demonstrate the superior performance of the proposed method in anatomy reconstruction and laparoscopic localization. The proposed framework can be potentially extended to the current surgical navigation system.

Stereopsis for rapidly moving targets.

Stereoscopic depth perception is possible with luminance-defined target velocities at least as high as 600° s-1, up to the limit of 30 Hz imposed by the high-temporal frequency cut-off of the eye. The limitation for perceiving depth from stereo disparity of moving targets is not their velocity but the temporal frequency bandwidth of the eye, which is affected by adaption state. Stereoacuity for a depth shift in a horizontally moving grating depends not on spatial disparity between corresponding luminance points in spatial units of arc min, but on the spatial shift as a fixed proportion of the period of the grating, in other words, on the phase angle difference between the two eyes, as is also the case for obliquely orientated, stationary gratings. Phase differences explain not only the classic Pulfrich stereophenomenon but its equivalent with dynamic visual noise, and a new effect in which depth results from interocular phase differences in luminance modulation. This article is part of a discussion meeting issue 'New approaches to 3D vision'.

Analysis on the Change of Stereoscopic Depth Perception with Geometrical Monocular Cues

Analysis on the Change of Stereoscopic Depth Perception with Geometrical Monocular Cues

Ernst Wilhelm Brücke on stereoscopic vision

ABSTRACT In the early 19th century the doctrine of identical retinal points, linked with the Vieth-Müller circle, was a pillar of German physiological optics. It was challenged by Wheatstone’s observations of stereoscopic depth perception announced in 1838; he also advanced a cognitive theory of binocular vision that attacked physiological interpretations. In 1841 Brücke mounted a defense of the doctrine by questioning Wheatstone’s observations and offering an alternative interpretation in terms of the integration over time of a rapid sequence of convergence eye movements. The theory could not be sustained because of evidence that stereoscopic depth occurred without eye movements. Brücke also questioned Wheatstone’s observations that with some stereoscopic displays stimulation of identical retinal points could result in double vision. The binocular combination of circles differing in size was accounted for by differentially dissociating accommodation in opposite directions for each eye from convergence. Despite the negative reaction to Brücke’s proposals, his speculations about the nature of rapid eye movements and of their neural basis were ahead of his time.

Altered spontaneous brain activity in patients with comitant exotropia before and after surgery: A resting-state fMRI study

Patients with comitant exotropia (CE) would usually develop compromised binocular vision and impaired stereoscopic depth perception, which could result in a profound decrease in quality of life. Although the deviated optic axis could be corrected surgically, the impaired stereovision and sensory eye balance may sometimes remain remnant. This study was to investigate the brain functional alterations in patients with CE before and after surgery, using resting-state functional magnetic resonance imaging (fMRI) with amplitude of low-frequency fluctuation (ALFF). Thirty-five patients with CE were recruited to undergo a preoperative fMRI scan, as well as 24 healthy controls (HCs). Twenty-four of the patients were available for rescanned fMRI one month after surgery. The ALFF method was used to evaluate the group differences of spontaneous brain activity. The correlations between ALFF values and clinical variables were analyzed in the patient group. Preoperatively, compared with HCs, 35 patients with CE showed significantly decreased ALFF values in one cluster involving bilateral calcarine sulcus, lingual gyrus and cuneus. The ALFF values in the above cluster were negatively correlated with disease duration (r = −0.379, P = 0.033). One month after surgery, 24 patients with available rescanned fMRI demonstrated increased ALFF values in one cluster located in bilateral cuneus, calcarine sulcus and lingual gyrus relative to the preoperative collection, while still reduced ALFF values in the cluster involving left calcarine sulcus and lingual gyrus compared with HCs. Our study revealed the functional changes of patients with CE in visual-associated brain areas before and after surgery. The findings may provide a new perspective for understanding the underlying pathological mechanisms of CE.

Alfred Wilhelm Volkmann on stereoscopic vision

ABSTRACT Wheatstone’s demonstration of binocular single vision and depth with stimulation of non-corresponding points reverberated throughout mid-nineteenth century German visual science. It challenged the received view that single vision was a consequence of retinal correspondence otherwise objects were seen double. Wheatstone also argued that stimulation of corresponding points could yield double vision. He interpreted his experimental observations in psychological rather than physiological terms, as did Helmholtz later. Volkmann addressed both of these challenges in a long article on stereoscopic vision published in 1859. While he accepted the first of the questions Wheatstone posed Volkmann was more cautious with regard to the second. Volkmann was an experimentalist who applied psychophysical methods to determine thresholds for stereoscopic depth perception. In line with many of his colleagues in Germany, he took issue implicitly with Wheatstone’s approach: how can the detailed quantitative experiments supporting Vieth and Müller’s interpretation of binocular single vision be derailed by simple observations with a stereoscope? Unlike most of his colleagues, Volkmann was swayed in Wheatstone’s favor through his own experiments: both physiological and psychological processes are involved in stereoscopic depth perception.

MRI Stereoscope: A Miniature Stereoscope for Human Neuroimaging.

Stereoscopic vision enables the perception of depth. To study the brain mechanisms behind stereoscopic vision using noninvasive brain imaging (magnetic resonance brain imaging; MRI), scientists need to reproduce the independent views of the left and right eyes in the brain scanner using "dichoptic" displays. However, high-quality dichoptic displays are technically challenging and costly to implement in the MRI scanner. The novel miniature stereoscope system ("MRI stereoscope") is an affordable and open-source tool that displays high-quality dichoptic images inside the MRI scanner. The MRI stereoscope takes advantage of commonly used display equipment, the MRI head coil, and a display screen. To validate the MRI stereoscope, binocular disparity stimuli were presented in a 3T MRI scanner while neural activation was recorded using functional MRI in six human participants. The comparison of large binocular disparities compared with disparities close to zero evoked strong responses across dorsal and ventral extra-striate visual cortex. In contrast, binocularly anti-correlated stimuli, which are not perceived in depth, did not evoke comparable activation. These results are the proof-of-concept that the MRI stereoscope can deliver dichoptic images that produce the perception of stereoscopic depth during acquisition of MR responses. Application of the MRI stereoscope to neuroscience can help to address important questions in perception and consciousness.

Virtual Reality visualization for computerized COVID-19 lesion segmentation and interpretation

Coronavirus disease (COVID-19) is a severe infectious disease that causes respiratory illness and has had devastating medical and economic consequences globally. Therefore, early, and precise diagnosis is critical to control disease progression and management. Compared to the very popular RT-PCR (reverse-transcription polymerase chain reaction) method, chest CT imaging is a more consistent, sensible, and fast approach for identifying and managing infected COVID-19 patients, specifically in the epidemic area. CT images use computational methods to combine 2D X-ray images and transform them into 3D images. One major drawback of CT scans in diagnosing COVID-19 is creating false-negative effects, especially early infection. This article aims to combine novel CT imaging tools and Virtual Reality (VR) technology and generate an automatize system for accurately screening COVID-19 disease and navigating 3D visualizations of medical scenes. The key benefits of this system are a) it offers stereoscopic depth perception, b) give better insights and comprehension into the overall imaging data, c) it allows doctors to visualize the 3D models, manipulate them, study the inside 3D data, and do several kinds of measurements, and finally d) it has the capacity of real-time interactivity and accurately visualizes dynamic 3D volumetric data. The tool provides novel visualizations for medical practitioners to identify and analyze the change in the shape of COVID-19 infectious. The second objective of this work is to generate, the first time, the CT African patient COVID-19 scan datasets containing 224 patients positive for an infection and 70 regular patients CT-scan images. Computer simulations demonstrate that the proposed method’s effectiveness comparing with state-of-the-art baselines methods. The results have also been evaluated with medical professionals. The developed system could be used for medical education professional training and a telehealth VR platform.

On the Art of Binocular Rivalry.

Binocular rivalry has a longer descriptive history than stereoscopic depth perception both of which were transformed by Wheatstone's invention of the stereoscope. Thereafter, artistic interest in binocular vision has been largely confined to stereopsis. A brief survey of research on binocular contour rivalry is followed by anaglyphic examples of its expression as art. Rivalling patterns can be photographs, graphics, and combinations of them. In addition, illustrations of binocular lustre and interactions between rivalry and stereopsis are presented, as are rivalling portraits of some pioneers of the science and art of binocular vision. The question of why a dynamic process like binocular rivalry has been neglected in visual art is addressed.

Neural Mechanism Underlying Stereoscopic Depth Perception: Why are the Two Eyes Aligned?

This paper explains the basics of depth perception and explores why both eyes are aligned. We concluded that the brain may analyze image features for binocular fusion while calculating the horizontal disparity for depth perception.

A remote and immersive setup for pandemic-safe surgical education

Abstract Existing challenges in surgical education (See one, do one, teach one) as well as the Covid-19 pandemic make it necessary to develop new ways for surgical training. This is also crucial for the dissemination of new technological developments. As today’s live transmissions of surgeries to remote locations always come with high information loss, e.g. stereoscopic depth perception, and limited communication channels. This work describes the implementation of a scalable remote solution for surgical training, called TeleSTAR (Telepresence for Surgical Assistance and Training using Augmented Reality), using immersive, interactive and augmented reality elements with a bi-lateral audio pipeline to foster direct communication. The system uses a full digital surgical microscope with a modular software-based AR interface, which consists of an interactive annotation mode to mark anatomical landmarks using an integrated touch panel as well as an intraoperative image-based stereo-spectral algorithm unit to measure anatomical details and highlight tissue characteristics.We broadcasted three cochlea implant surgeries in the context of otorhinolaryngology. The intervention scaled to five different remote locations in Germany and the Netherlands with lowlatency. In total, more than 150 persons could be reached and included an evaluation of a participant’s questionnaire indicating that annotated AR-based 3D live transmissions add an extra level of surgical transparency and improve the learning outcome.

Dichoptic Perceptual Training and Sensory Eye Dominance Plasticity in Normal Vision

PurposeWe introduce a set of dichoptic training tasks that differ in terms of (1) the presence of external noise and (2) the visual feature implicated (motion, orientation), examining the generality of training effects between the different training and test cues and their capacity for driving changes in sensory eye dominance and stereoscopic depth perception.MethodsWe randomly assigned 116 normal-sighted observers to five groups (four training groups and one no training group). All groups completed both pre- and posttests, during which they were tested on dichoptic motion and orientation tasks under noisy and noise-free conditions, as well as a binocular phase combination task and two depth tasks to index sensory eye dominance and binocular function. Training groups received visual training on one of the four dichoptic tasks over 3 consecutive days.ResultsTraining under noise-free conditions supported generalization of learning to noise-free tasks involving an untrained feature. By contrast, there was a symmetric learning transfer between the signal-noise and no-noise tasks within the same visual feature. Further, training on all tasks reduced sensory eye dominance but did not improve depth perception.ConclusionsTraining-driven changes in sensory eye balance do not depend on the stimulus feature or whether the training entails the presence of external noise. We conjecture that dichoptic visual training acts to balance interocular suppression before or at the site of binocular combination.

Endocranial Anatomy of the Giant Extinct Australian Mihirung Birds (Aves, Dromornithidae)

Dromornithids are an extinct group of large flightless birds from the Cenozoic of Australia. Their record extends from the Eocene to the late Pleistocene. Four genera and eight species are currently recognised, with diversity highest in the Miocene. Dromornithids were once considered ratites, but since the discovery of cranial elements, phylogenetic analyses have placed them near the base of the anseriforms or, most recently, resolved them as stem galliforms. In this study, we use morphometric methods to comprehensively describe dromornithid endocranial morphology for the first time, comparing Ilbandornis woodburnei and three species of Dromornis to one another and to four species of extant basal galloanseres. We reveal that major endocranial reconfiguration was associated with cranial foreshortening in a temporal series along the Dromornis lineage. Five key differences are evident between the brain morphology of Ilbandornis and Dromornis, relating to the medial wulst, the ventral eminence of the caudoventral telencephalon, and morphology of the metencephalon (cerebellum + pons). Additionally, dromornithid brains display distinctive dorsal (rostral position of the wulst), and ventral morphology (form of the maxillomandibular [V2+V3], glossopharyngeal [IX], and vagus [X] cranial nerves), supporting hypotheses that dromornithids are more closely related to basal galliforms than anseriforms. Functional interpretations suggest that dromornithids were specialised herbivores that likely possessed well-developed stereoscopic depth perception, were diurnal and targeted a soft browse trophic niche.

Learning Laparoscopic Surgery Skills With a 4K Ultra-High Definition 2D vs a Three-Dimensional HD Laparoscopic System: Results From a Prospective Randomized Trial.

Background. In minimally invasive surgery (MIS), the loss of stereoscopic depth perception in a two-dimensional (2D) representation is most challenging. Recently introduced 4K ultrahigh definition (UHD) 2D optical systems could potentially facilitate the learning and use of compensation mechanisms for the loss of depth perception. However, the role of the new 4K technology against three dimensional (3D) in learning and implementation of MIS remains unknown. The aim of this trial was to determine the influence of 4K UHD 2D vs 3D HD representation on the acquisition of MIS skills. Methods. This was a prospective randomized study involving 62 MIS-inexperienced study participants. We compared a laparoscopic 4K UHD 2D (system A) vs a laparoscopic 3D HD system (system B) for differences in learning MIS skills using the Lübeck Toolbox (LTB) video box trainer. We evaluated participants' performance regarding the repetitions required to reach the goal of each LTB task. Results. Comparing systems A and B, participants using the laparoscopic 3D system required fewer repetitions to achieve goals of LTB tasks No. 1 (P = .0048) and No. 3 (P = .0014). In contrast, for LTB tasks No. 2 and No. 4, no significant difference could be determined between both groups. Conclusion. Our results indicated that MIS basic skills can be learned quicker using a 3D HD system vs a 4K UHD 2D system. However, for MIS tasks in confined spaces, the learning speed with 4K UHD 2D imaging seems to be comparable to a 3D HD system.