Human Stereopsis Research Articles

Detection of the Relative Depth between Surfaces with the Same or Different Features in Human Stereopsis

Detection of the Relative Depth between Surfaces with the Same or Different Features in Human Stereopsis

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.

Can human stereopsis improve by making the eyes optically perfect?

Can human stereopsis improve by making the eyes optically perfect?

Analytical procedures for 3D mapping at the Photogeological Laboratory of the Geological Survey of Denmark and Greenland

Photogrammetry is a classical remote sensing technique dating back to the 19th century that allows geologists to make three-dimensional observations in two-dimensional images using human stereopsis. Pioneering work in the 1980s and 1990s (Dueholm 1992) combined the use of vertical (nadirlooking) aerial photographs with oblique stereo images from handheld small-frame cameras into so-called multi-model photogrammetry. This was a huge technological step forward that made it possible to map, in three dimensions, steep terrain that would otherwise be inaccessible or poorly resolved in conventional nadir-looking imagery. The development was fundamental to the mapping and investigation of e.g. the Nuussuaq basin (Pedersen et al. 2006). Digital photogrammetry, the all-digital version of multi-model photogrammetry, is nowadays an efficient and powerful geological tool that is used by the Photogeological Laboratory at the Geological Survey of Denmark and Greenland (GEUS) to address geological problems in a range of projects from 3D mapping to image-based surface reconstruction and orthophoto production. Here we present an updated description (complementary to Dueholm 1992) of the analytical procedures in the typical digital workflow used in current 3D mapping projects at GEUS.

7.2: Invited Paper: Quantification and Modulation of Stereopsis in Humans

Binocular vision in general and stereopsis in particular are fundamental to human vision and visual actions. It is widely thought that about 5% of the population have a lazy eye and lack stereo vision, so it is often supposed that most of the population (95%) have good stereo abilities. We show that this is not the case; 68% have good to excellent stereo (the haves) and 32% have moderate to poor stereo (the have‐nots). Why so many people lack good 3‐D stereo vision is unclear but it is likely to be neural and reversible.Interocular suppression and stereopsis are two important binocular functions. To date, it still remains unclear about the relationship between them. Here, we use the binocular phase combination paradigm and a comparable paradigm to provide a normative dataset for perceptual eye dominance and stereo acuity in 142 normal‐sighted human adults and analyze their correlation. We show that our eye dominance and stereopsis are not strongly correlated in the normalsighted subjects. These results thus support the idea that the binocular phase combination and stereopsis may be limited by different factors in normal‐sighted adults.At present there is no good way of reliably measuring stereopsis in the clinic other than the standard book tests designed for children. These are convenient but coarsely quantized in disparity with no measure of variance. This makes it difficult to be able to assess the significance of differences from visit to visit contingent on therapy. We report an iPod app that has been developed from laboratory studies of normal stereopsis, to measure stereo in the clinic that is not limited by these factors. The application enables measurements over the wide disparity range and not just at the finest disparities. In addition, it allows changes in stereopsis of the order of 1.9 to be statistically distinguished.Luminance plays a modulating role in the processes of several visual tasks, which in turn provides significant information for the understanding of visual processing. To study the relationship between luminance and stereopsis, we manipulated the mean luminance seen by both eyes or the interocular difference in mean luminance by using ND filters placed in front of both eyes or just one eye respectively. We found that disparity processing was little affected by a binocular change in luminance, but was greatly affected by a luminance mismatch between the two eyes. To investigate its origin we manipulated two factors, the temporal synchrony between the two eyes and the interocular contrast. Both factors are implicated in the loss of stereo performance when the mean luminance is different between the eyes, suggesting an underlying explanation in terms of temporal low‐pass filtering resulting in the combination of a luminance‐dependent temporal delay and a luminance‐dependent change in contrast gain.These results add to our knowledge of stereopsis and have therapeutic potential in re‐establishing stereopsis in patients with binocular disorders.

Estimation of Altitude in Stereoscopic-3D Versus 2D Real-world Scenes

Research on the role of human stereopsis has largely focused on laboratory studies that control or eliminate other cues to depth. However, in everyday environments we rarely rely on a single source of depth information. Despite this, few studies have assessed the impact of binocular vision on depth judgements in real-world scenarios presented in simulation. Here we conducted a series of experiments to determine if, and to what extent, stereoscopic depth provides a benefit for tasks commonly performed by helicopter aircrew. We assessed the impact of binocular vision and stereopsis on perception of (1) relative and (2) absolute distance above the ground (altitude) using natural and simulated stereoscopic-3D (S3D) imagery. The results showed that, consistent with the literature, binocular vision provides very weak input to absolute altitude estimates at high altitudes (10-100ft). In contrast, estimates of relative altitude at low altitudes (0-5ft) were critically dependent on stereopsis, irrespective of terrain type. These findings are consistent with the view that stereopsis provides important information for altitude judgments when close to the ground; while at high altitudes these judgments are based primarily on the perception of 2D cues.

Neurons in Striate Cortex Signal Disparity in Half-Matched Random-Dot Stereograms

Human stereopsis can operate in dense "cyclopean" images containing no monocular objects. This is believed to depend on the computation of binocular correlation by neurons in primary visual cortex (V1). The observation that humans perceive depth in half-matched random-dot stereograms, although these stimuli have no net correlation, has led to the proposition that human depth perception in these stimuli depends on a distinct "matching" computation possibly performed in extrastriate cortex. However, recording from disparity-selective neurons in V1 of fixating monkeys, we found that they are in fact able to signal disparity in half-matched stimuli. We present a simple model that explains these results. This reinstates the view that disparity-selective neurons in V1 provide the initial substrate for perception in dense cyclopean stimuli, and strongly suggests that separate correlation and matching computations are not necessary to explain existing data on mixed correlation stereograms. The initial step in stereoscopic 3D vision is generally thought to be a correlation-based computation that takes place in striate cortex. Recent research has argued that there must be an additional matching computation involved in extracting stereoscopic depth in random-dot stereograms. This is based on the observation that humans can perceive depth in stimuli with a mean binocular correlation of zero (where a correlation-based mechanism should not signal depth). We show that correlation-based cells in striate cortex do in fact signal depth here because they convert fluctuations in the correlation level into a mean change in the firing rate. Our results reinstate the view that these cells provide a sufficient substrate for the perception of stereoscopic depth.

A Temporal and Multi-Resolution Visualization System for Large-Scale Data

In this paper we propose a multi-resolution visualization approach based on a forcedirected algorithm to graphically and hierarchically represent large-scale data sets. Considering the limitations of the human visual cognitive system, it is reasonable to dynamically and interactively extract the most important or user-specified information for representation. To smoothly animate the merging or splitting of nodes and edges in a graph, we adopt a jelly-like metaball technique. Our prototype system clusters and graphically represents thousands of nodes and links in a novel way that allows a user to recognize visually. By adopting our system, the hierarchy of information and the evolving trends are dynamically visualized through an interactive 3D graphical interface, in addition to simultaneous display of data detail and summarization. Furthermore, user perception can be enhanced by adopting human 3D stereopsis skills such as Perspective, Chiaroscuro, and Focusing method.

The Limits of Human Stereopsis in Space and Time

To encode binocular disparity, the visual system determines the image patches in one eye that yield the highest correlation with patches in the other eye. The computation of interocular correlation occurs after spatiotemporal filtering of monocular signals, which leads to restrictions on disparity variations that can support depth perception. We quantified those restrictions by measuring humans' ability to see disparity variation at a wide range of spatial and temporal frequencies. Lower-disparity thresholds cut off at very low spatiotemporal frequencies, which is consistent with the behavior of V1 neurons. Those thresholds are space-time separable, suggesting that the underlying neural mechanisms are separable. We also found that upper-disparity limits were characterized by a spatiotemporal, disparity-gradient limit; to be visible, disparity variation cannot exceed a fixed amount for a given interval in space-time. Our results illustrate that the disparity variations that humans can see are very restricted compared with the corresponding luminance variations. The results also provide insight into the neural mechanisms underlying depth from disparity, such as why stimuli with long interocular delays can still yield clear depth percepts.

A minimal algorithm for computing the likelihood of binocular correspondence1

AbstractI present an algorithm for calculating the likelihood of obtaining stereo images under the assumption that both eyes view the same scene, and test this algorithm using numerical simulations. Each stereo pair analyzed was based on two slightly different views of the same three‐dimensional (3‐D) scene (binocularly correlated) or two entirely different views of unrelated scenes (binocularly uncorrelated). The correlated stereo pair contained local binocular disparities that defined a consistent 3‐D structure. A likelihood ratio was computed for each stereo pair, by assuming the increase of the local cross‐correlation due to the epipolar constraint for binocular correspondence. For complex, random‐dot and natural stereo images, the likelihood ratio correctly predicted whether the two eyes viewed the same 3‐D scene. The results indicate that the algorithm proposed here is useful in modeling human stereopsis.

Human Stereopsis Is Not Limited by the Optics of the Well-Focused Eye

Human stereopsis, the perception of depth from differences in the two eyes' images, is very precise: image differences smaller than a single photoreceptor can be converted into a perceived difference in depth. To better understand what determines this precision, we examined how the eyes' optics affects stereo resolution. We did this by comparing performance with normal, well-focused optics and with optics improved by eliminating chromatic aberration and correcting higher-order aberrations. We first measured luminance contrast sensitivity in both eyes and showed that we had indeed improved optical quality significantly. We then measured stereo resolution in two ways: by finding the finest corrugation in depth that one can perceive, and by finding the smallest disparity one can perceive as different from zero. Our optical manipulation had no effect on stereo performance. We checked this by redoing the experiments at low contrast and again found no effect of improving optical quality. Thus, the resolution of human stereopsis is not limited by the optics of the well-focused eye. We discuss the implications of this remarkable finding.

인간의 입체시 특성을 고려한 입체 카메라의 광축 간격 조절

최근 입체영상 콘텐츠를 소비하기 위한 인프라는 급속도로 구축되고 있지만, 이러한 수요를 충족시킬만한 입체영상 제작기반은 부족한 상황이다. 지금의 입체영상 제작환경에서는 기존에 평면영상을 제작하던 것과 같은 방법으로 입체영상을 제작하고 있다. 그로 인해 인간의 시지각과 카메라의 특성이 고려되지 않은 영상이 제작되고, 이것은 입체효과의 저하와 함께 영상 속 피사체의 크기가 현실과 다르게 왜곡되어 나타나는 등의 문제로 이어지고 있다. 본 논문에서는 이러한 문제를 인식하고 더 나은 입체영상 콘텐츠 제작을 위해, 입체영상 관람 시 나타나는 인간의 크기 지각 특성을 고려한 입체 카메라의 광축 간격 조절에 대하여 연구하였다. 우선, 카메라의 광축 간 거리에 따라 영상 속에 나타나는 피사체의 면적 변화와 비율 데이터를 산출하였고, 광축 간격을 변화시키며 실제 입체영상을 촬영, 관람자들을 대상으로 설문을 진행하였다. 그 결과 인간의 입체시는 인간의 두 눈간 거리인 6.5cm를 기준으로 약 60%에서 2,000% 범위인 3.9cm에서 130cm 내에서는 광축 간 거리가 변화하더라도 크기 지각에 왜곡을 느끼지 않는다. 그러므로 입체영상 촬영할 때 광축 간격을 3.9cm에서 130cm 내에서 유지한다면 영상 관람에도 크기 지각에 문제가 발생하지 않고 실제와 동일한 크기로 느껴지는 영상을 제작할 수 있을 것이다. Recently, the infrastructure of stereoscopy is growing fast. Though, the stereoscopy producing capacity is insufficient to meet the demand of the market. Because, at the moment most people who produce the stereoscopy are skilled for the two-dimensional images. So the characteristics of the human stereopsis and stereoscopic cameras are not well considered, it occurs many problems to the viewer. According to this, we studied about the optical axis distance adjustment of stereoscopic camera considering size perception in human stereopsis. First, we measured the area of the object in the image which depends on the optical axis distance. Second, based on the output of first experiment, we conducted a survey and figured out that if we keep the optical axis distance between 3.9cm to 130cm, it wouldn't occur any size perception and will be possible to produce high quality stereoscopy.

Perisaccadic Stereo Depth with Zero Retinal Disparity

When an object is viewed binocularly, unequal perspective projections of the two eyes' half images (binocular disparity) provide a cue for the sensation of stereo depth. For almost 200 years, binocular disparity has remained synonymous with retinal disparity, which is computed by subtracting the distance of each half image from its respective fovea. However, binocular disparity could also be coded in headcentric instead of retinal coordinates, by combining eye position and retinal image position in each eye and representing disparity as differences between visual directions of half images relative to the head. Although these two disparity-coding schemes suggest very different neural mechanisms, both offer identical predictions for stereopsis in almost every viewing condition, making it difficult to empirically distinguish between them. We designed a novel stimulus that uses perisaccadic spatial distortion to generate inconsistency between headcentric and retinal disparity. Foveal half images flashed asynchronously just before a horizontal saccade have zero retinal disparity, yet they produce a sensation of depth consistent with a nonzero headcentric disparity. Furthermore, this headcentric disparity can cancel and reverse the perceived depth stimulated with nonzero retinal disparity. This is the first demonstration that a coding scheme other than retinal disparity has a role in human stereopsis.

Review Paper: Human factors of stereo displays: An update

Abstract— This updated review paper provides a selected review of a number of important perceptual and human‐factors issues that arise when stereo displays are designed and used. This review and analysis draws heavily from the basic vision literature in order to help provide insight for future design solutions for stereo displays. Issues discussed include: (1) the basics of human stereopsis (horopter, binocular disparity, binocular rivalry); (2) low‐level factors (interocular cross talk, interocular differences in luminance and contrast, accommodation‐vergence mismatch, stereoanomaly); (3) contextual factors (spatio‐temporal frequency effects, distance scaling of disparity); and (4) a high‐level cognitive factor (high‐level cue conflict). In this updated review, significant new material has been added: (1) interocular luminance and contrast differences and their effect on stereo viewing; (2) more insightful discussion of accommodative‐vergence mismatch; (3) high‐level cognitive factor. Two topics in the earlier review (visual pathways; dark focus and dark vergence) have been deleted. The paper concludes with the presentation of several recommendations for the design of stereo displays.

Stereo transparency in ambiguous stereograms generated by overlapping two identical dot patterns

In binocular vision, observers can perceive transparent surfaces by fusing a stereogram composed of two overlapping patterns with different disparities. When dot patterns of two surfaces are identical, the stereogram has potential matches leading to both transparency and non-transparency (or unitary surface) perceptions. However, these two matching candidates are exclusive if the uniqueness assumption holds. This stereogram can be regarded as a random-dot version of the double-nail illusion and a stereo version of the locally paired-dot stimulus that was used to investigate the neural mechanism for motion transparency. Which surface is perceived in this ambiguous stereogram would reflect the property of the transparency detection mechanism in human stereopsis. Here we perform a parametric study to examine the perceptual property in this ambiguous stereogram. The result showed that the ability in transparency detection from this stereogram is determined by the contrast reversal ratio between overlapping patterns within small regions the width of which was about 0.4 deg. The width was similar to the receptive field sizes of neurons in striate cortex. The result suggests that the contrast reversal between two identical patterns would modulate activities of binocular neurons, and this modification gives a crucial effect on the neural representation for overlapping disparities.

54.1:Invited Paper: Human Factors of Stereoscopic Displays

AbstractThis paper provides a review of human factors issues that arise when designing stereoscopic displays. Issues discussed include: (1) basics of human stereopsis; (2) interocular cross talk; (3) distance scaling of disparity information; (4) accommodative‐vergence mismatch; (5) stereoanomly; (6) intuitive reasoning. The paper concludes with several recommendations.

Limits of stereopsis explained by local cross-correlation

Human stereopsis has two well-known constraints: the disparity-gradient limit, which is the inability to perceive depth when the change in disparity within a region is too large, and the limit of stereoresolution, which is the inability to perceive spatial variations in disparity that occur at too fine a spatial scale. We propose that both limitations can be understood as byproducts of estimating disparity by cross-correlating the two eyes' images, the fundamental computation underlying the disparity-energy model. To test this proposal, we constructed a local cross-correlation model with biologically motivated properties. We then compared model and human behaviors in the same psychophysical tasks. The model and humans behaved quite similarly: they both exhibited a disparity-gradient limit and had similar stereoresolution thresholds. Performance was affected similarly by changes in a variety of stimulus parameters. By modeling the effects of stimulus blur and of using different sizes of image patches, we found evidence that the smallest neural mechanism humans use to estimate disparity is 3-6 arcmin in diameter. We conclude that the disparity-gradient limit and stereoresolution are indeed byproducts of using local cross-correlation to estimate disparity.

Disparity statistics in natural scenes

Binocular disparity is the input to stereopsis, which is a very strong depth cue in humans. However, the distribution of binocular disparities in natural environments has not been quantitatively measured. In this study, we converted distances from accurate range maps of forest scenes and indoor scenes into the disparities that an observer would encounter, given an eye model and fixation distances (which we measured for the forest environment, and simulated for the indoor environment). We found that the distributions of natural disparities in these two kinds of scenes are centered at zero, have high peaks, and span about 5 deg, which closely matches the macaque MT cells' disparity tuning range. These ranges are fully within the operational range of human stereopsis determined psychophysically. Suprathreshold disparities (>10 arcsec) are common rather than exceptional. There is a prevailing notion that stereopsis only operates within a few meters, but our finding suggests that we should rethink the role of stereopsis at far viewing distances because of the abundance of suprathreshold disparities.

Human factors of 3‐D displays

Abstract— This paper provides a selected review of a number of important perceptual and human‐factors issues that arise when 3‐D displays are designed and used. This review and analysis draws heavily from the basic vision literature in order to help provide insight for future design solutions for 3‐D displays. Issues discussed include (1) the basics of human stereopsis, (2) interocular crosstalk, (3) oculomotor responding and distance scaling of binocular disparity information, (4) accommodative‐vergence mismatch, and (5) stereoanomly. The paper concludes with a presentation of several recommendations for the design of 3‐D displays.

The Stereoscopic Sliver: A Comparison of Duration Thresholds for Fully Stereoscopic and Unmatched Versions

Just as positional disparities of image features seen with both eyes provide depth information, the presence of an area visible to one eye but not the other within a binocularly viewed scene can indicate an occlusion at a depth discontinuity. The close geometrical association between these two kinds of cues suggests they may both be exploited by stereopsis. To investigate this, we developed a novel binocular stimulus entirely lacking in classical disparity that contains an unmatched vertical sliver which elicits a warping of the surrounding surface to accommodate a depth discontinuity. We measured depth-discrimination performance at a range of stimulus durations, correcting for variations in stimulus visibility, to characterise the decline of the efficacy of the depth signal with limited integration time. Results show a close correspondence of performance for similar stimuli with unmatched features and classical binocular disparity across a sixtyfold range of viewing durations, supporting the notion of a close association between the two types of cues in human stereopsis. Control experiments excluded simple eye-of-origin cues and long-range false matches as explanatory factors.