Depth Perception of Interfering Periodic Patterns: A Possible Contribution to Disorientation on Escalators

Perception ◽  
1992 ◽  
Vol 21 (6) ◽  
pp. 747-752 ◽  
Author(s):  
Roger C Munck-Fairwood
Keyword(s):  
Interference Pattern ◽  
Depth Perception ◽  
Apparent Depth ◽  
Periodic Patterns ◽  
Depth Cues ◽  
The Many

Incongruous and illusory depth cues, arising from ‘interference patterns’ produced by overlapping linear grids at the edges of escalator treads, may contribute to the disorientation experienced by some escalator users, which in turn may contribute to the causes of some of the many escalator accidents which occur. The apparent depth of the interference pattern from the viewer is analysed in terms of the cues deriving from size and viewer motion. Both of these cues support the depth of the target being infinite. Preliminary observations are reported which confirm this analysis. Remedies for the problem are suggested. The possible contribution of this illusion to disorientation on escalators, due to misjudgment of depth, is compared with another recently reported factor which is due to stereoscopic miscorrespondence of periodic targets.

Depth from shading and disparity in humans and monkeys

2007 ◽  
Vol 24 (2) ◽  
pp. 207-215 ◽  
Author(s):  
YING ZHANG ◽  
VERONICA S. WEINER ◽  
WARREN M. SLOCUM ◽  
PETER H. SCHILLER
Keyword(s):  
Animal Model ◽  
Visual System ◽  
Depth Perception ◽  
Discrimination Task ◽  
Stimulus Display ◽  
Neural Mechanisms ◽  
Depth Information ◽  
Depth Cues ◽  
Good Animal Model

A stimulus display was devised that enabled us to examine how effectively monkeys and humans can process shading and disparity cues for depth perception. The display allowed us to present these cues separately, in concert and in conflict with each other. An oddities discrimination task was used. Humans as well as monkeys were able to utilize both shading and disparity cues but shading cues were more effectively processed by humans. Humans and monkeys performed better and faster when the two cues were presented conjointly rather than singly. Performance was significantly degraded when the two cues were presented in conflict with each other suggesting that these cues are processed interactively at higher levels in the visual system. The fact that monkeys can effectively utilize depth information derived from shading and disparity indicates that they are a good animal model for the study of the neural mechanisms that underlie the processing of these two depth cues.

Suprathreshold Stereo-Depth Matches as a Function of Contrast and Spatial Frequency

Perception ◽  
1986 ◽  
Vol 15 (3) ◽  
pp. 249-258 ◽  
Author(s):  
Clifton M Schor ◽  
Peter A Howarth
Keyword(s):  
Spatial Frequency ◽  
Depth Perception ◽  
Low Frequency ◽  
Stereoscopic Depth ◽  
Apparent Depth ◽  
Black Line ◽  
Low Contrast ◽  
Spatial Frequencies ◽  
Vertical Bars ◽  
Thin Black Line

Thresholds for stereoscopic-depth perception increase with decreasing spatial frequency below 2.5 cycles deg−1. Despite this variation of stereo threshold, suprathreshold stereoscopic-depth perception is independent of spatial frequency down to 0.5 cycle deg-1. Below this frequency the perceived depth of crossed disparities is less than that stimulated by higher spatial frequencies which subtend the same disparities. We have investigated the effects of contrast fading upon this breakdown of stereo-depth invariance at low spatial frequencies. Suprathreshold stereopsis was investigated with spatially filtered vertical bars (difference of Gaussian luminance distribution, or DOG functions) tuned narrowly over a broad range of spatial frequencies (0.15–9.6 cycles deg−1). Disparity subtended by variable width DOGs whose physical contrast ranged from 10–100% was adjusted to match the perceived depth of a standard suprathreshold disparity (5 min visual angle) subtended by a thin black line. Greater amounts of crossed disparity were required to match broad than narrow DOGs to the apparent depth of the standard black line. The matched disparity was greater at low than at high contrast levels. When perceived contrast of all the DOGs was matched to standard contrasts ranging from 5–72%, disparity for depth matches became similar for narrow and broad DOGs. 200 ms pulsed presentations of DOGs with equal perceived contrast further reduced the disparity of low-contrast broad DOGs needed to match the standard depth. A perceived-depth bias in the uncrossed direction at low spatial frequencies was noted in these experiments. This was most pronounced for low-contrast low-spatial-frequency targets, which actually needed crossed disparities to make a depth match to an uncrossed standard. This bias was investigated further by making depth matches to a zero-disparity standard (ie the apparent fronto-parallel plane). Broad DOGs, which are composed of low spatial frequencies, were perceived behind the fixation plane when they actually subtended zero disparity. The magnitude of this low-frequency depth bias increased as contrast was reduced. The distal depth bias was also perceived monocularly, however, it was always greater when viewed binocularly. This investigation indicates that contrast fading of low-spatial-frequency stimuli changes their perceived depth and enhances a depth bias in the uncrossed direction. The depth bias has both a monocular and a binocular component.

How is Depth Perception Affected by Long-Term Wearing of Left-Right Reversing Spectacles?

Perception ◽  
1993 ◽  
Vol 22 (8) ◽  
pp. 971-984 ◽  
Author(s):  
Makoto Ichikawa ◽  
Hiroyuki Egusa
Keyword(s):  
Depth Perception ◽  
Binocular Disparity ◽  
Depth Cues ◽  
Directional Relation ◽  
Random Dot Stereogram ◽  
Binocular Depth

The plasticity of binocular depth perception was investigated. Six subjects wore left-right reversing spectacles continuously for 10 or 11 days. On looking through the spectacles, the relation between the direction of physical depth (convex or concave) and the direction of binocular disparity (crossed or uncrossed) was reversed, but other depth cues did not change. When subjects observed stereograms through a haploscope and were asked to judge the direction of perceived depth, the directional relation between perceived depth and disparity was reversed both in the two line-contoured stereograms and in the random-dot stereogram in the middle of the wearing period, but the normal relation often returned late in the wearing period. When subjects observed two objects while wearing the spectacles and were asked which appeared the nearer, veridical depth perception increased as the wearing-time passed. These results indicate that the visual transformation reversing the direction of binocular disparity causes changes both in binocular stereopsis and in processes integrating different depth cues.

Depth Perception in Alzheimer's Disease

1996 ◽  
Vol 83 (3) ◽  
pp. 987-995 ◽  
Author(s):  
Mario F. Mendez ◽  
Monique M. Cherrier ◽  
Robert S. Meadows
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Depth Perception ◽  
Motion Parallax ◽  
Relative Size ◽  
Depth Cues ◽  
Visuospatial Deficits ◽  
Visuospatial Functions ◽  
Monocular Depth ◽  
Global Stereopsis

Abnormal depth perception contributes to visuospatial deficits in Alzheimer's disease. Disturbances in stereopsis, motion parallax, and the interpretation of static monocular depth cues may result from neuropathology in the visual cortex. We evaluated 15 patients with mild Alzheimer's disease and 15 controls matched for age, sex, and education on measures of local stereopsis (stereoscopic testing), global stereopsis (random dots), motion parallax (Howard-Dolman apparatus), and monocular depth perception by relative size, interposition, and perspective. Compared to controls, the patients were significantly impaired in over-all depth perception. This impairment was largely due to disturbances in local stereopsis and in the interpretation of depth from perspective, independent of other visuospatial functions. Patients with Alzheimer's disease have disturbed interpretation of monocular as well as binocular depth cues. This information could lead to optic interventions to improve their visual depth perception.

Dynamic Occlusion and Motion Parallax in Depth Perception

Perception ◽  
1988 ◽  
Vol 17 (2) ◽  
pp. 255-266 ◽  
Author(s):  
Hiroshi Ono ◽  
Brian J Rogers ◽  
Masao Ohmi ◽  
Mika E Ono
Keyword(s):  
Relative Motion ◽  
Depth Perception ◽  
Motion Parallax ◽  
Three Dimensional ◽  
Depth Order ◽  
Depth Cues ◽  
Small Depth ◽  
Stationary Observer ◽  
Depth Separation ◽  
Condition B

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.

Effects of Time Delay on Depth Perception via Head-Motion Parallax in Virtual Environment Systems

2000 ◽  
Vol 9 (6) ◽  
pp. 638-647 ◽  
Author(s):  
Hanfeng Yuan ◽  
W. L. Sachtler ◽  
Nat Durlach ◽  
Barbara Shinn-Cunningham
Keyword(s):  
Time Delay ◽  
Virtual Environment ◽  
Depth Perception ◽  
Head Movement ◽  
Time Delays ◽  
Motion Parallax ◽  
Head Motion ◽  
Depth Cues ◽  
Random Dot Patterns

Experiments were conducted to determine how the ability to detect and discriminate head-motion parallax depth cues is degraded by time delays between head movement and image update. The stimuli consisted of random-dot patterns that were programmed to appear as one cycle of a sinusoi dal grating when the subject's head moved. The results show that time delay between head movement and image update has essentially no effect on the ability to discrimi nate between two such gratings with different depth char acteristics when the delay is less than or equal to roughly 265 ms.

Depth Perception in Pandora's Box and Size Illusion: Evolution with Age

Perception ◽  
1983 ◽  
Vol 12 (2) ◽  
pp. 177-185 ◽  
Author(s):  
Jacques Chevrier ◽  
André Delorme
Keyword(s):  
Depth Perception ◽  
Relative Position ◽  
Linear Perspective ◽  
Pictorial Stimulus ◽  
Texture Gradient ◽  
Familiar Size ◽  
Depth Cues ◽  
Pictorial Depth

The aim of the experiment was to study the evolution with age (6, 8, 11 and 14 years) of pictorial depth perception in Pandora's box and to compare it with the evolution of size illusion with the same subjects and the same pictorial backgrounds. In addition to familiar size and relative position, each pictorial stimulus contained one or more of the following depth cues: linear perspective, texture gradient, and interposition. The two kinds of measurements produced different results. Size illusions, although present, did not vary with age but increased with the number of cues. Estimates of distance in Pandora's box increased with age and varied according to the type of cue present: texture gradient seemed to be critical to the amount of depth perceived. The correlation between size adjustments and distance adjustments was significant only for the two oldest groups of subjects (11 and 14 years).

Adaptation to the Reversal of Binocular Depth Cues: Effects of Wearing Left-Right Reversing Spectacles on Stereoscopic Depth Perception

Perception ◽  
1981 ◽  
Vol 10 (4) ◽  
pp. 391-402 ◽  
Author(s):  
Shinsuke Shimojo ◽  
Yoshitaka Nakajima
Keyword(s):  
Depth Perception ◽  
Neural Mechanism ◽  
Adaptive Change ◽  
Stereoscopic Depth ◽  
Depth Cues ◽  
Uncrossed Disparity ◽  
Random Dot Stereograms ◽  
Long Time ◽  
Binocular Depth

The principle of stereopsis, that crossed disparity causes a convex perception and uncrossed disparity a concave one, has for a long time been considered to depend on a very rigid neural mechanism not affected by experience. Experiments are reported here which show that this relationship between disparity and perceived depth can be reversed by experience. An observer wore a pair of left-right reversing spectacles continuously for nine days. The spectacles also reversed the relation between the direction of perceived depth and the direction of binocular depth cues, ie disparity and vergence. For a period starting two days before wearing the spectacles and continuing until seventy-nine days after their removal the observer was examined with a haploscope and an electrooculograph. All the stereoscopic experiments were carried out without spectacles in order to examine some aftereffects of wearing spectacles. For the stereograms with linear contours not only the adaptive reversal of the relation between disparity and perceived depth, but also some abnormal depth perceptions and long-lasting aftereffects were found. For Julesz's random-dot stereograms, however, in which contours can be seen only after binocular combination, no adaptive change or reversal occurred. These results suggest that the process of stereopsis consists of two concurrent subprocesses.

The Efficient Range of Velocities for Inducing Depth Perception by Motion Parallax

1996 ◽  
Vol 83 (2) ◽  
pp. 659-674 ◽  
Author(s):  
Keikichi Hayashibe
Keyword(s):  
Angular Velocity ◽  
Relative Motion ◽  
Depth Perception ◽  
Motion Parallax ◽  
Apparent Depth ◽  
Velocity Range ◽  
Simulated Motion

The range of velocities over which depth perception can be simulated by motion parallax, was studied experimentally. Perception of apparent depth was induced using method of simulated motion parallax. In the condition of ‘observer parallax,’ the range of angular velocity over which apparent depth accompanied by motion was perceived was 0.0048 to 0.048 rad/sec., while velocities for which robust perception of apparent depth was obtained were restricted to the range 0.0010 to 0.0024 rad/sec., and no perceived reversals of depth occurred over this range. No distinct range for robust perception of apparent depth could be found in the condition of ‘stimulus parallax.’ In the case of velocity ratios of 1:1.1 and 1:1.3, the velocity that produced the most robust perception of apparent depth was 0.0024 rad/sec., and inhibition of perceived depth reversals occurred at 0.0010 rad/sec. Under conditions of opposing relative motion, the velocity range over which robust perception of apparent depth was observed was 0.0005 to 0.0010 rad/sec., slightly lower than when both motions were in the same direction.

Depth Perception of Surfaces in Pictures: Looking for Conventions of Depiction in Pandora's Box

Perception ◽  
1983 ◽  
Vol 12 (1) ◽  
pp. 5-20 ◽  
Author(s):  
Kevin Berbaum ◽  
David Tharp ◽  
Kenneth Mroczek
Keyword(s):  
Light Source ◽  
Depth Perception ◽  
Local Features ◽  
Apparent Depth ◽  
Source Position ◽  
Background Space ◽  
Made In

The perception of depth in monocularly viewed pictures has been investigated with the use of a binocular rangefinder developed by Gregory. Two experiments are reported which focus upon stimulus conditions that were identified by Haber as conventions for rendering depth in pictures. Several conclusions, which concern assumptions that must be made in interpreting pictures according to such conventions, are supported by the results. There is a default or assumed layout of background space. The interpretation of a point in a depiction depends upon the interpretation of neighboring points, so that interpretations of local features influence the interpretations of nearby ‘empty’ areas. In photographs, the magnitude of apparent depth depends upon the degree of discrepancy between the position of the illuminating source and the observer's supposed light-source position. Also in photographs, apparent depth increases as the contrast between highlights and attached shadows increases.

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