Chapter 6: Space Perception and Binocular Vision

Euclidian geometry

Parallel lines remain parallel as they are extended in space.

Binocular Vision Advantages

Probability summation and Binocular summation

Probability summation

The increased probability of detecting a stimulus from having two or more samples.

Binocular summation

The combination (or "summation") of signals from each eye in ways that make performance on many tasks better with both eyes than with either eye alone.

Binocular disparity

The differences between the two retinal images of the same scene.

Stereopsis

A vivid perception of the three-dimensionality of the world that is not available with monocular vision.

Depth cue

Information about the third dimension (depth) of visual space. (Monocular, Binocular, Oculomotor)

Depth Cues Monocular

a visual signal that allows the brain to perceive depth using only one eye.

Metrical depth cue

A depth cue that provides quantitative information about distance in the third dimension.

- Relative and absolute

Nonmetrical depth cue

A depth cue that provides information about the depth order (relative depth) but not depth magnitude.

Occlusion

A cue to relative depth order in which, for example, one object partially obstructs the view of another object.

Projective Geometry

the study of geometric properties that are invariant with respect to projective transformations. (Ex: Shadows cast)

Relative size

A comparison of size between items without knowing the absolute size of either one.

Relative height

For objects touching the ground, those higher in the visual field appear to be farther away. In the sky above the horizon, objects lower in the visual field appear to be farther away.

Texture gradient

based on the geometric fact that items of the same size form smaller, closer spaced images the farther away they get.

Familiar size

A cue based on knowledge of the typical size of objects. (absolute metrical depth cue)

Aerial/atmospheric perspective

A depth cue based on the implicit understanding that light is scattered by the atmosphere.

Linear perspective and vanishing points

Monocular depth cue where parralell lines appear to converge in the distance.

Anamorphic projection

a distorted projection that creates a recognizable image when viewed from a specific angle.

Shadow and shading

Monocular depth cue

Deletion and accretion

Monocular depth cue that includes the gradual dissapearance of one object behind another and the gradual reapperance of that object.

Motion parallax

Images closer to the observer move faster across the visual field than images farther away. - Due to movement of head or any other relative movement

Motion parallax caused by optic flow

a global pattern of visual motion that is both caused by and signals self-motion.

Kinetic depth effects

Rotational motion, wave motion, walking motion, and optical expansion.

Oculomotor depth cue

visual signals that provide information about the distance of objects based on the movements and adjustments made by the eyes

Accommodation

Oculomotor depth cue: lens changes shape to focus on objects

Vergence, Convergence and Divergence

Oculomotor depth cue

Absolute disparity

the difference in angle subtended on the left and right retina of an object in space and gives an estimate of the depth of that object to the observer.

Binocular disparity

The differences between the two retinal images of the same scene.

Corresponding retinal points

A geometric concept stating that points on the retina of each eye where the monocular retinal images of a single object are formed are at the same distance from the fovea in each eye.

Horopter

The location of objects whose images lie on the corresponding points. The surface of zero disparity.

Vieth-Müller circle

The location of objects whose images fall on geometrically corresponding points in the two retinas.

Panum's fusional area

The region of space, in front of and behind the horopter, within which binocular single vision is possible.

Diplopia

Double vision. If visible in both eyes, stimuli falling outside of Panum's fusional area will appear this way.

Stereoscope

A device for presenting one image to one eye and another image to the other eye.

Crossed and uncrossed disparity

"Crossed disparity" refers to the visual signal created when an object is closer to you than the point you are focusing on, causing the images on your retinas to be slightly offset towards the nasal side of each eye, while "uncrossed disparity" occurs when an object is further away than the focus point, causing the retinal images to be offset towards the temporal side of each eye.

Free fusion

The technique of converging (crossing) or diverging (uncrossing) the eyes in order to view a stereogram without a stereoscope.

Stereoblindness

An inability to make use of binocular disparity as a depth cue.

Random dot stereogram (RDS)

A stereogram made of a large number of randomly placed dots.

Correspondence problem

In binocular vision, the problem of figuring out which bit of the image in the left eye should be matched with which bit in the right eye. - The problem is particularly vexing in images like random dot stereograms.

Solving the correspondence problem

Blurring the image: Leaving only the low-spatial frequency information helps. - Uniqueness constraint: The observation that a feature in the world is represented exactly once in each retinal image. - Continuity constraint: The observation that, except at the edges of objects, neighboring points in the world lie at similar distances from the viewer. - Brain sensing dissimilar features - Motion disparity

Stereopsis

can be used as both a metrical and nonmetrical depth cue.

The Bayesian approach

A way of formalizing the idea that our perception is a combination of the current stimulus and our knowledge about the conditions of the world—what is and is not likely to occur.

Ponzo Illusion

Zollner Illusion

Hering Illusion

Binocular rivalry

The competition between the two eyes for control of visual perception, which is evident when completely different stimuli are presented to the two eyes.

Stereoacuity

A measure of the smallest binocular disparity that can generate a sensation of depth.

Cyclopean

One of Hering's laws, the law of common binocular direction, states that the directions derived from the two eyes' images will be perceived as if the observer is viewing the scene from a single vantage point between the two eyes.

Uniqueness constraint

each feature in one eye can only match to one feature in the other eye.

Continuity constraint

in stereopsis, the observation that, except at the edges of objects, neighboring points in the world lie at similar distances from the viewer.

Dichoptic

Referring to the presentation of two stimuli, one to each eye. Different from binocular presentation, which could involve both eyes looking at a single stimulus.

Strabismus

A misalignment of the two eyes such that a single object in space is imaged on the fovea of one eye, and on a nonfoveal area of the other (turned) eye.

- Esotropia

- Exotropia

- loss of stereopsis

Suppression

In vision, the inhibition of an unwanted image.