The Role of Disparity Gradient in Stereo Vision

Trivedi, Harit P.; Lloyd, Sheelagh A

doi:10.1068/p140685

Cited by 33 publications

(18 citation statements)

References 3 publications

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“…Disparity gradients at these limiting values indicate the cases where two objects lie on a common line of sight for one eye. It was reported that absolute value of disparity gradient for two dots must be Ͻ1-2 for binocular fusion depending on exact dot parameters (Burt and Julesz 1980;Prazdny 1985;Trivedi and Lloyd 1985). For this reason, we would expect most neurons to be encoding disparity gradient within these limits, if neural encoding of surface slants is constructed in an efficient manner.…”

Section: Spatial Frequency-tuning Testmentioning

confidence: 99%

Encoding of Three-Dimensional Surface Slant in Cat Visual Areas 17 and 18

Sanada

Ohzawa²

2006

Journal of Neurophysiology

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Sanada, Takahisa M. and Izumi Ohzawa. Encoding of threedimensional surface slant in cat visual areas 17 and 18. J Neurophysiol 95: 2768 -2786, 2006. First published January 4, 2006 doi:10.1152/jn.00955.2005. How are surface orientations of threedimensional objects and scenes represented in the visual system? We have examined an idea that these surface orientations are encoded by neurons with a variety of tilts in their binocular receptive field (RF) structure. To examine whether neurons in the early visual areas are capable of encoding surface orientations, we have recorded from single neurons extracellularly in areas 17 and 18 of the cat using standard electrophysiological methods. Binocular RF structures are obtained using a binocular version of the reverse correlation technique. About 30% of binocularly responsive neurons have RFs with statistically significant tilts from the frontoparallel plane. The degree of tilts is sufficient for representing the range of surface slants found in typical visual environments. For a subset of neurons having significant RF tilts, the degrees of tilt are correlated with the preferred spatial frequency difference between the two eyes, indicating that a modified disparity energy model can account for the selectivity, at least partially. However, not all cases could be explained by this model, suggesting that multiple mechanisms may be responsible. Therefore an alternative hypothesis is also examined, where the tilt is generated by pooling of multiple disparity detectors whose preferred disparities progressively shift over space. Although there is evidence for extensive spatial pooling, this hypothesis was not satisfactory either, in that the neurons with extensive pooling tended to prefer an untilted surface. Our results suggest that encoding of surface orientations may begin with the binocular neurons in the early visual cortex. I N T R O D U C T I O NOne of the fundamental roles of the visual system is to reconstruct a three-dimensional (3D) model of the external world from a pair of two-dimensional images on the two retinae. Horizontal displacement of the eyes causes small differences between the retinal images. This difference of the retinal images is called binocular disparity and stereopsis is the process of determining depth from binocular disparity. Visual information processing for stereopsis begins in the primary visual cortex and neurons found in this area are known to encode binocular disparities of stimuli for a small area of visual field (Barlow et al. 1967;Ferster 1981; Wiesel 1962, 1968;LeVay and Voigt 1988;Nikara et al. 1968; Ohzawa and Freeman 1986a,b;Ohzawa et al. 1990Ohzawa et al. , 1996Ohzawa et al. , 1997.How does the processing of stereoscopic information proceed once binocular disparity for small localized areas is available? Is a possible next stage of processing that of detecting the rate of change of binocular disparity, i.e., detecting 3D orientations of surfaces in depth? Some recent studies have examined these possibilities and report that a sub...

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Section: Spatial Frequency-tuning Testmentioning

confidence: 99%

Encoding of Three-Dimensional Surface Slant in Cat Visual Areas 17 and 18

Sanada

Ohzawa²

2006

Journal of Neurophysiology

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“…al. that a vector field with a d t =1.0 represents a stereo vision field of view that has no occlusion or overlap in the target scene [13]. A value of 2.0 or greater indicates occlusion or other discontinuities.…”

Section: Disparity Gradient Filtering Module: "Flow"mentioning

confidence: 99%

Improved Pressure Sensitive Paint Measurement Using Natural Feature Tracking and Piecewise Linear Resection

Kuzub

Mébarki

Whitehead

2011

2011 Canadian Conference on Computer and Robot Vision

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Wind tunnel Pressure Sensitive Paint (PSP) ratio techniques require accurate registration between wind-on and wind-off camera image pairs. The Piecewise Linear Resection (PLR) method of removing registration due to physical wind tunnel model motion and deformation errors can account for nonlinear deformations and benefits from increased tracking point coverage in the image. This work presents a method to increase the accuracy of PLR by tracking natural features in addition to standard fiducial markers. This is accomplished with Speeded-Up Robust Features (SURF) and a modified disparity gradient filtering technique. This work shows that this method of automatic PLR is feasible on wind tunnel imagery and that the resulting pressure data has reduced misregistration noise without the need to perform 3D resection using virtual models and pre-defined deformation equations.

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“…5Ronghly speaking, a bound on first differences of disparities. See [Burt & Julesz 1980a, b;Fleck 1988b;Pollard, Mayhew, & Frisby 1985;Trivedi & Lloyd 1985] for details. 6All synthetic stereo pairs shown in this article are generated with the full range of intensity values ([0, 255]) and then degraded to simulate real image conditions.…”

Section: Notesmentioning

confidence: 99%

A topological stereo matcher

Fleck

1991

Int J Comput Vision

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Presented here is a new stereo algorithm that produces dense, high-quality, subpixel disparity maps. It offers two improvements over previous algorithms. First, it does not blur disparity values across sharp changes in depth. Second, it can reconstruct the correct correspondence between two images even when there is substantial vertical displacement between them: this algorithm has been tested with rotations up to 10 degrees and vertical translations up to 16 pixels. Although such image pairs require extra processing time, this ability is vital when exact calibration cannot be maintained.The new algorithm depends on two new ideas. First, it exploits the fact that the correct vertical disparity field is due to camera misalignment and, thus, has only a few (significan0 degrees of freedom. The algorithm passes camera alignment parameters, not raw disparity fields, between scales. Disparities at individual locations can diverge only slightly from this global model, greatly reducing the algorithm's search space.Second, the new algorithm uses a pre-match filter that prevents two patches of image from matching if they do not have the same (local) topological structure. This constraint subsumes previous "figural continuity" proposals and can be checked by simple, local operations. The filter seems to improve the algorithm's ability to select the correct match from many alternatives and it suppresses intermediate values near sharp changes in disparity. This technique can be extended to other matching tasks, such as motion tracking, analyzing texture periodicity, and evaluating the performance of edge finders.

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The Role of Disparity Gradient in Stereo Vision

Cited by 33 publications

References 3 publications

Encoding of Three-Dimensional Surface Slant in Cat Visual Areas 17 and 18

Encoding of Three-Dimensional Surface Slant in Cat Visual Areas 17 and 18

Improved Pressure Sensitive Paint Measurement Using Natural Feature Tracking and Piecewise Linear Resection

A topological stereo matcher

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