PerLecture 9 - Depth and Size Vision Lecture Notes

Vocabulary flashcards covering depth perception, oculomotor and visual cues, monocular and binocular disparity, and size-distance scaling based on the lecture transcript.

Vision’s inverse problem

The challenge where the visual system must understand a 3d world from a 2d image, which can be encoded in an infinite amount of ways.

Depth Cues

The different sources of information or cues that humans use to reconstruct the 3d structure of the environment in vision.

Oculomotor Cues

A subset of depth cues based on the position of the eyes and the use of the 6 extra-ocular muscles; it consists of convergence and accommodation.

Convergence

The inward movement of the eyes when looking at a nearby object to direct the fovea to fixate on it; a greater angle signals a closer distance.

Descartes’ Theory of Binocular Depth Perception

The suggestion that depth perception is determined by eye movement, claiming that focusing on closer then further objects allows the angle of convergence for both to be encoded.

Accommodation

The process of contracting or retracting the ciliary muscle to alter the focal distance of the eye, allowing images to focus on the retina.

Visual Cues

Cues that can be depicted on a flat canvas, consisting of pictorial, movement-based, and binocular disparity.

Pictorial Cues

Monocular visual cues that require only one eye to provide depth information from a linear perspective.

Linear Perspective

A pictorial visual cue where parallel lines in an image converge into a single vanishing point, requiring a horizon line and orthogonal lines.

Orthogonal lines

Parallel lines that converge into the vanishing point in a linear perspective image.

Perspective Convergence

The phenomenon where lines that are parallel in the world appear to converge in an image as they get further away at the vanishing point.

Occlusion

A pictorial visual cue occurring when closer objects block or slightly hide more distant ones.

Height in the visual field

A depth cue where objects lower in the visual field appear closer when below the horizon (reversed for objects above the horizon).

Texture Gradients

A depth cue where objects that are further away appear smaller and denser in images.

Familiar Size

The use of the known size of familiar objects to help scale the unknown size of other objects.

Epstein (1965)

A study that showed familiar size only worked in the absence of other cues, suggesting it is a weaker cue.

Cast shadows

Shadows that provide information about an object's distance from a surface.

Attached shadows (shading)

Shadows that provide information about an object's shape or volume.

Atmospheric Perspective

The phenomenon where distant objects look more hazy and blue-ish because light from them does not hit the fovea due to optical blurring.

Tilt Shift Miniaturization

An effect where blur and accommodation infer that the subject is very close and everything blurry is very far.

Looming/Receding

A monocular motion-based cue where objects moving further away appear to become smaller.

Deletion & Accretion

A monocular motion-based cue where parts of a further object disappear (deletion) and reappear (accretion) during occlusion in motion.

Movement Parallax

A monocular motion-based cue where objects moving at a constant speed appear to move a greater amount when they are closer to the observer.

Binocular Disparity

A binocular cue where the lateral difference in the placement of each eye creates two different retinal images that provide depth information.

Stereoscopic depth

The perception of depth based on small positional differences between images formed on both retinae (binocular disparity).

Polaroid Filters

A method where two different superimposed images are presented to each eye using different colored filters.

Corresponding Points

Points on each retina where fixated objects and non-fixated objects on the horopter fall.

Horopter

The imaginary circle where objects fall onto corresponding retinal points.

Barlow et al. (1967)

Researchers who found that some neurons are sensitive to particular degrees of disparity, leading to increased response.

Blake and Hirsch (1975)

A study where cats restricted to monocular vision failed to develop binocular cells sensitive to disparity, preventing them from perceiving depth from disparity.

Visual Angles

Angles that depend on both the distance and size of an object, which can lead to mistakes in size perception.

Emmert’s Law

The law of size-distance scaling expressed as $\text{Perceived Size} = \text{Retinal Size} \times \text{Perceived Distance} \times k$.