Depth Edges Research Articles

Pre-attentive segmentation and correspondence in stereo.

Traditional stereo grouping models have focused on the problem of stereo correspondence between monocular inputs. Recent physiological data revealed that the disparity selective V2 cells increase their responses when (random-dot stereograms) stimuli within their receptive fields are at or near the boundary of a depth surface. Such highlights to depth (non-luminance) edges are seemingly not computationally required for the correspondence problem. Computationally, these highlights make the boundaries of a depth surface more salient, serving pre-attentive segmentation (between depth planes) and attracting visual attention. In special cases, they enable the psychophysically observed perceptual pop-out of a target from a background of visually identical distractors at a different depth. To achieve the highlights, mutual inhibition between disparity selective cells that are tuned to the same or similar depths is required. However, such mutual inhibition would impede the computation for the correspondence problem, which requires mutual excitation between the same cells. In this work, I introduce a computational model that, I believe, is the first to address both stereo correspondence and pre-attentive stereo segmentation. The computational mechanisms in the model are based on intracortical interactions in V2. I will demonstrate that the model captures the following physiological and psychophysical phenomena: (i) depth-edge highlighting; (ii) disparity capture; (iii) pop-out; and (iv) transparency.

Preliminary Results of Cylindrical Electrostatic Confinement Experiment

Effects of electrode shape on fusion reaction rate in the cylindrical IECF device are investigated by the experiments to verify simulation results. The effects of the cylindrical edge of anodes are clearly observed, but the effect of cathode length and radius is not clear in the preliminary experiments. The maximum neutron generation rate of ~47 thousand neutrons per second is obtained with 37.5kV, 6mA discharge using an anode with 40-mm depth edge.

Illumination change at a depth edge can reduce lightness constancy.

Lightness constancy requires that a surface retain its lightness not only when the illumination is changed but also when the surface is moved from one background to another. Occlusion of one surface by another frequently results in a retinal juxtaposition of patches under different illuminations. At such edges, retinal luminance ratios can be much higher than in scenes with a single illumination. We demonstrate that such retinal adjacencies can produce failures of lightness constancy. We argue that they are responsible for departures from perfect lightness constancy in two prior experiments that examined the effects of depth relations on lightness constancy.

Learning to see random-dot stereograms.

In the present study some specific properties of the learning effects reported for random-dot stereograms are examined. In experiment 1 the retinal position-specific learning effect was reproduced and in a follow-up experiment it was shown that the position specificity of learning can be accounted for by selective visual attention. In experiments 2 and 3 evidence was obtained that suggests that observers can learn, to a certain degree, monocular random-dot patterns and that this learning facilitates the depth percept. This result indicates that the traditional belief that random-dot stereograms are devoid of monocularly recognizable or useful forms should be reconsidered. In the second set of experiments the learning of two binocular surface properties of random-dot stereograms, depth edges and internal depth regions, was investigated. It was shown in experiment 4 that the depth edges of random-dot stereograms are not learned, whereas the results of experiment 5 indicate that the internal depth regions are learned. Finally, in experiment 6 it was shown that depth edges are learned when the internal depth regions of the stereogram are ambiguous. The results are discussed in terms of the importance of the particular type of stimulus used in the learning process and in terms of perceptual learning and attention.

Buckling of Open Cylindrical Shells with Torsionally Stiff Rectangular Edge Stiffeners

The bifurcation strength of open cylindrical shells with torsionally very stiff edge stiffeners of rectangular cross section subject to uniform axial load is determined analytically using Donnell's simplified equations. A deflection function with arbitrary undetermined coefficients satisfying the end conditions is assumed. The stress resultants are derived in terms of these coefficients. These stress resultants and the deflections of the shell are made to satisfy the assumed boundary conditions along the longitudinal edges. The resulting determinant of the equations is set equal to zero in order to obtain the critical buckling stress. The limited results obtained in this paper indicates an interesting phenomena that the critical buckling stress of a shell with a shallow edge stiffener is well above the critical buckling stress of a shell with free edges, whereas the buckling of a shell with moderate depth edge stiffeners in a narrow region is only slightly above the critical buckling stress of a shell with free edges.