Showing papers on "Monocular vision published in 1989"

Monocular Geometry Is Selectively Distorted in the Central Visual Field of Strabismic Amblyopes

Abstract: Strabismic amblyopia is associated with a distorted perception of visual space. The aim of our study was to investigate the monocular space perception of strabismic observers at several locations in the central and peripheral visual field. We tested nine observers with strabismic and/or anisometropic amblyopia, two strabismic subjects with alternating fixation and two normal control subjects. The task was to align a light stimulus with two vertically arranged reference marks. Testing conditions included three separations of the references along the vertical meridian (10 degrees, 20 degrees and 40 degrees) as well as several presentation sites of the vertical references in the nasal and temporal peripheral visual field (5 degrees, 10 degrees and 20 degrees from fixation). Performance with the amblyopic eye was clearly impaired as compared to the nonamblyopic eye. For alignment along the vertical meridian, all amblyopic eyes showed increased uncertainty in their position judgements. Most of the squinting eyes of amblyopes also displayed a systematic lateral displacement of the test stimulus in relation to the reference marks, in the most extreme case up to almost 7 degrees. Usually, larger errors were found with wider separations of the reference marks. In the peripheral field, the differences between the amblyopic and the nonamblyopic eye diminished or disappeared. Thus, monocular geometry appears to be selectively impaired in the central visual field of the deviated eye of strabismic amblyopes. These spatial distortions might be related to the different states of binocular correspondence in the central vs. peripheral visual field, shown by some strabismic amblyopes.

Monocular vision using inverse perspective projection geometry: analytic relations

Abstract: The author derives a variety of relationships, all in the reference frame of the camera, between 3-D points; 3-D lines; collections of 3-D lines; the angles between lines lying in common planes; the planes in which lines may lie; and the corresponding perspective projection of the 3-D points, lines and angles. These relationships are useful in many aspects of model-based vision and can serve as the geometric basis of a perspective-projection expert system. The derivations are outlined, and practical implications are briefly indicated. >

Binocular depth reversals despite familiarity cues

Abstract: Stereoscopic depth can be reversed by interchanging the left- and right-eye views (pseudoscopy) when abstract stereograms are used, but not when stereograms contain natural objects or scenes. This resistance to reversal of depth has traditionally been attributed to familiarity with the shape of objects and the presence of monocular depth cues. However, when texture disparity is neutralized by making the texture perspective of surfaces identical for both eyes, even a highly familiar object, like a monocularly recognizable human face, appears as concave (nose pointing inwards) when viewed pseudoscopically.

Self-Produced Locomotion and the Development of Responsiveness to Linear Perspective and Texture Gradients.

Abstract: Replicated and extended research on the development of sensitivity to the depth cues of linear perspective and texture gradients by using a more sensitive method (Experiment 1) and by investigating the role of self-produced locomotion in facilitating the onset of sensitivity to information (Experiment 2). Using a method similar to Yonas, Granrud, Arterberry, and Hanson (1986), infants' reaching to the pictorially closer object served as the dependent measure. Changes in methodology provided an increase in the difference between 7-month-olds' monocular and binocular reaching performance, but 5-month-olds failed to show evidence of sensitivity to the depth cues investigated. Experiment 2 found no difference in monocular reaching performance among 7-month-old infants with varying degrees of locomotor experience, suggesting that self-produced locomotion may not play a role in facilitating the onset of sensitivity to static-monocular depth information.

Fused binocular vision is required for development of proper eye alignment in barn owls.

Abstract: The eyes of adult barn owls (Tyto alba) are virtually fixed in the head in positions that are highly consistent from one individual to the next. However, early in development the eyes are exodeviated; the eyes achieve their adult positions during the owl's second month of life. Disruption of binocular vision in baby owls leads to permanent, highly abnormal eye positions and interocular alignment. Of three owls raised with both eyelids sutured closed, two developed exotropic strabismus and one developed esotropic strabismus. Two owls reared with monocular vision developed esotropic strabismus, whereas three owls reared with fused, but optically deviated binocular vision developed normal eye positions. Thus, the alignment of the eyes in adults results from an active process that depends on fused binocular vision during early life. Extracellular microelectrode recordings from the optic tecta of strabismic owls reveal that many units retain binocular inputs from corresponding points of the two eyes: the left-eye and right-eye receptive fields of individual units are misaligned by an amount predicted by the direction and magnitude of the strabismus. These results indicate that an innately determined pattern of connections in the brain anticipates the eye positions necessary to achieve binocular fusion. The hypothesis is put forth that the powerful activation of such binocular neurons by strong, synchronous inputs from the two eyes is the signal required by the optimotor system that proper eye alignment has been attained.

Relative 3D-State Estimation for Autonomous Visual Guidance of Road Vehicles

Abstract: The integrated spatio-temporal approach to real-time machine vision, which has allowed outstanding performance with moderate computing power, is extended to obstacle recognition and relative spatial state estimation using monocular vision. A modular vision system architecture is discussed centering around features and objects. Experimental results with VaMoRs, a 5-ton test vehicle are given. Stopping in front of obstacles of at least 0.5 m 2 cross section has been demonstrated on unmarked two-lane roads at velocitie up to 40 km/h.

Partial Binocular-Overlap In Helmet-Mounted Displays

Abstract: One approach to decreasing the size and weight of a helmet-mounted display while maintaining a wide-field-of-view and adequate image resolution is to use a partial binocular-overlap configuration. With a partial binocular-overlap helmet-mounted display the user would see a central binocular image flanked by two monocular images. Properly implemented, the user should not be aware of the partial-overlap condition, but would benefit from the reduced weight, decreased size, and extended field-of-view. However, the successful implementation of a partial-overlap design requires understanding of and solutions for several complex problems.

Binocular rivalry and dichoptic masking: suppressed stimuli do not mask stimuli in a dominating eye.

Abstract: Reaction time was used to gauge the sensitivity of an eye during its dominant and suppressed phases of binocular rivalry. During dominance, performance was uniformly good in detecting both stimuli that were spatially identical to the suppressed stimulus and those that were different in spatial frequency. When suppressed eyes were tested, performance was poor when the stimulus was different from the dominating stimulus, but even worse when the test stimulus and the dominating stimulus were spatially identical. The results favor the view that suppression operates nonselectively on a monocular visual channel, prior to the point at which dichoptic pattern masking occurs. Language: en

Cyclopean Tilt Aftereffects Can Be Induced Monocularly: Is There a Purely Binocular Process?:

Abstract: A series of experiments have been reported by Wolfe and Held which they have taken as evidence for the existence of more than one binocular process in human vision, specifically a simple binocular process (OR-gate) and a purely binocular process (AND-gate). In one of their studies, it was shown that tilt aftereffects induced with cyclopean stimuli produced measurable effects only when testing was binocular, which suggested that cyclopean adaptation affects only the AND-gate mechanism. If the two alleged mechanisms (AND or OR) are independent, monocular adaptation with luminance contrast stimuli should produce aftereffects which can only be measured with luminance contrast test stimuli. Cyclopean test displays would probe only the unadapted AND-mechanism. Results to the contrary are reported, casting doubt upon the functional independence, perhaps even the existence, of the so-called purely binocular process.

Anatomy of a flash. 1. Two-peak masking and a temporal filling-in.

Abstract: A modified paradigm of Crawford masking was used to link masking to brightness fluctuation, as distinct from flash brightness. Thresholds were measured for a 10 ms incremental pulse (the 'probe') presented before, during, or after a 500 ms pulse (the 'flash'). Both pulses were spatially coextensive with the background field, thus the criterion for probe detection was purely temporal. The flash occurred either in the tested eye, the opposite eye, or in both eyes. In all conditions, masking was strongly bimodal: thresholds peaked near flash onset and flash offset. The flash was perceived as a unitary event. Bimodal masking is attributed to cortical on-and off-effects, as (i) dichoptic masking was strong and (ii) the same incremental probe was masked by either incremental or decremental flashes. Strikingly, monocular probe thresholds were about equally elevated by binocular as by monocular flashes, although the binocular flashes were brighter. Therefore, some monocular features can be preserved in the larger net binocular response. A general conclusion is that masking depends on the same transient neural responses that bring about a brightness fluctuation, whereas the appearance of the flash as a single event, a unitary change of brightness, depends on a different mechanism, perhaps a sustained response that performs a temporal filling-in.

Grouping image features into loops for monocular recognition

Abstract: Model-based monocular vision has been used to recognize and locate 3-D objects by matching image corners (or lines) to model corners (or lines). These algorithms typically have high computational complexities. Grouping of visual features has been used to reduce the computational complexity. In this work point image features are grouped into loops and object loops that have similar viewpoint-invariant characteristics. Examples of viewpoint-invariant characteristics of loops are the number of lines and vertices, the number of convex and concave curves, and the sequence in which the lines, curves, and vertices are linked together. Grouping into loops also facilitates model matching by ellipses, in addition to corners and lines. Experiments are performed to extract loops from images and segmenting them into lines and elliptical curves. Distinguishable loops are used to find 3-D locations of the objects in scenes. >

Binocular Performance And Design

Abstract: A binocular extends the range of human vision. Binoculars enable the user to see objects at greater distances or, alternatively, to see greater detail in distant objects. In failing light, binocul are used to detect objects that the naked eye cannot detect. Binoculars also extend the range of stereo vision of the user; this application is primarily of interest in military fire control.

Factorial Design: Binocular and Monocular Depth Perception in Vertical and Horizontal Stimuli

Abstract: This article describes a factorial experiment that is useful as a laboratory exercise in a research methods course. In the Howani-Dolman depth perception apparatus, two vertical rods are adjusted, using binocular or monocular vision, so they appear equidistant from the observer. The two rods can also be oriented horizontally, which allows a factorial design combining the factors of Viewing Condition (binocular and monocular) and Rod Orientation (vertical and horizontal). The exercise illustrates the nature of an interaction and the necessity of an additional analysis of simple main effects. It also provides a basis fir understanding a perceptual problem in the real world-the difficulty of localizing horizontally extended stimuli such as power lines.

Do background luminances interact during binocular fusion

Abstract: The question investigated in the experiments reported here was whether monocular background luminances sum during binocular fusion. Fusion was made explicit by using a random-dot stereogram (RDS) as a background stimulus. In the presence of the RDS, differential luminance thresholds were somewhat higher than in the uniform field: a full-field, binocular dot array acted as a mask for a a full-field luminance change, but global depth had no effect at threshold. The amount of the binocular advantage at threshold was compared to the basic “threshold response,” that is, the change in threshold resulting from raising the background luminance by a factor of 2. It was found that the amount of the binocular advantage was equivalent, on the average, to some 75% of the threshold response-significantly less than the 100% predicted by “simple summation.” The amount of the binocular advantage varied substantially among observers and eyes, whereas the threshold response obeyed Weber’s law in all cases: the variability was eyerather than threshold-dependent. Monocular thresholds did not decrease when taken with the nontest eye occluded rather than viewing a fused background. The proposition that the adaptation state of the visual system is increased during binocular fusion (Cogan, 1982) was not supported. Yet occluding the nontest eye, rather than presenting the test stimulus monocularly against a fused background, did change monocular thresholds in some eyes and observers. These findings are interpreted as evidence for a complex binocular background interaction involving both summation and inhibition.