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Results for “DEPTH PERCEPTION”

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At least 235 records · Page 13Linked to original sources
PubMed2002

Blur discrimination and its relation to blur-mediated depth perception.

Retinal images of three-dimensional scenes often contain regions that are spatially blurred by different amounts, owing to depth variation in the scene and depth-of-focus limitations in the eye. Variations in blur between regions in the retinal image therefore offer a cue to their relative physical depths. In the first experiment we investigated apparent depth ordering in images containing two regions of random texture separated by a vertical sinusoidal border. The texture was sharp on one side of the border, and blurred on the other side. In some presentations the border itself was also blurred. Results showed that blur variation alone is sufficient to determine the apparent depth ordering. A subsequent series of experiments measured blur-discrimination thresholds with stimuli similar to those used in the depth-ordering experiment. Weber fractions for blur discrimination ranged from 0.28 to 0.56. It is concluded that the utility of blur variation as a depth cue is constrained by the relatively mediocre ability of observers to discriminate different levels of blur. Blur is best viewed as a relatively coarse, qualitative depth cue.

Adult↗
PubMed1988

Dynamic occlusion and motion parallax in depth perception.

Random-dot techniques were used to examine the interactions between the depth cues of dynamic occlusion and motion parallax in the perception of three-dimensional (3-D) structures, in two different situations: (a) when an observer moved laterally with respect to a rigid 3-D structure, and (b) when surfaces at different distances moved with respect to a stationary observer. In condition (a), the extent of accretion/deletion (dynamic occlusion) and the amount of relative motion (motion parallax) were both linked to the motion of the observer. When the two cues specified opposite, and therefore contradictory, depth orders, the perceived order in depth of the simulated surfaces was dependent on the magnitude of the depth separation. For small depth separations, motion parallax determined the perceived order, whereas for large separations it was determined by dynamic occlusion. In condition (b), where the motion parallax cues for depth order were inherently ambiguous, depth order was determined principally by the unambiguous occlusion information.

Attention↗
PubMed2001

Envelope size tuning for stereo-depth perception of small and large disparities.

Stereopsis is the sense of depth derived from binocular disparities that are formed between targets that are matched between the two retinal images. Binocular matches for sustained stereopsis are based on similarity of orientation, spatial frequency and contrast of the two retinal images whereas matches for transient stereopsis depend on these parameters to a very limited extent. In this investigation we have tested the possibility that transient stereopsis forms matches between objects of similar overall size. The tuning of sustained and transient stereopsis to contrast-envelope size was investigated by presenting narrow-band Gabor targets of unequal size to the two eyes. Bandwidth for envelope-size tuning was estimated from the range of dichoptic size-differences over which stereo performance remained above chance level. An equal bandwidth of 2 octaves was found for the sustained and transient stereo systems when stimulated with parallel orientation Gabors that subtended a small disparity. Sustained-stereo performance with orthogonal carriers was reduced with large envelope sizes. Bandwidth of the transient stereo system increased to 3 octaves when tested with a larger disparity stimulus and it was independent of carrier orientation. Reducing the contrast of the larger-size Gabor improved transient-stereo performance from near chance (48-58%) to 85-95%. Thus the bandwidth for envelope-size tuning is much broader than indicated with equal physical contrast stimuli. The observed tuning to envelope size, while broad, is tighter than that observed for carrier spatial-frequency [Vis. Res. 38 (1998) 3057], carrier orientation [Vis. Res. 39 (1999) 2717] and contrast polarity [Vis. Res. 39 (1999) 4010] of the stimulus. Thus it would appear that envelope size and, to a greater extent, temporal synchrony of the dichoptic stimuli [Perception 24 (1995) 33] are the primary means for selecting matched binocular inputs for transient stereopsis.

Contrast Sensitivity↗
PubMed2003

Paired and unpaired features can be equally effective in human depth perception.

The horizontal separation of the eyes results in the projection of slightly different images in each eye that are used to recover depth. One source of depth information is disparity, the relative position of paired features in the two eyes. Another source of depth information comes from features that are present in only one eye's view. These unpaired features arise from occlusion and by definition cannot generate a conventional disparity signal. Here we compare the depth signals generated by paired and unpaired features using stimuli that differ only in whether a given feature (a vertical gap) is paired or unpaired. Ecologically, both stimuli are consistent with two panels separated in depth at the gap, but only the paired gap provides a conventional disparity signal. We found strikingly that depth thresholds for the two gap conditions were the same and that there was perfect cross-adaptation of perceived depth from the unpaired to paired condition, strongly suggesting a common mechanism.

Contrast Sensitivity↗
PubMed1993

Lesion of the suprasylvian cortex impairs depth perception of cats.

Using a 2-alternative-forced-choice-procedure on a jumping stand, four adult cats were trained to make simple depth discriminations. They were tested binocularly and monocularly before and after bilateral lesions of different parts of the lateral suprasylvian cortex. Our results give support to a functional segregation between the lateral suprasylvian visual areas (LSA) and area 7. Lesion of any of these areas impairs the ability to use binocular depth cues. However, lesion of LSA more severely impairs the ability to use monocular depth cues whereas binocular ones can still be used. After lesion of area 7, binocular depth cues can no longer be used. Additional undercutting of areas 17/18/19 leads to a performance similar to that of area 17/18 lesioned cats.

Animals↗
PubMed2005

Illusory depth perception of oblique lines produced by overlaid vertical disparity.

Our visual system matches images from both eyes to establish a single view and stereo depth even when they contain a certain amount of vertical disparity. This paper demonstrates a new stereo effect showing an aspect of vertical disparity processing. When oblique lines without disparity are overlaid with sparse random dots with vertical disparity, the lines look closer or farther in depth. The characteristics of this stereo illusion were experimentally investigated. The results showed that the sign of the perceived depth of the oblique lines depended on the combination of the line orientation and the vertical disparity sign, and that the amount of perceived depth became larger as the line orientation became more horizontal. The depth illusion robustly existed even under conditions that ruled out eye movements (i.e., vertical vergence and cyclovergence) by local-parallel or brief presentations of the stereo figures. This phenomenon suggests that the visual system locally measures vertical disparity and is not simply tolerating a small amount of vertical disparity. Stereo capture of vertical disparity and horizontal matching after vertical image shifts were proposed as possible explanations for the depth illusion.

Depth Perception↗