4.2 Depth perception and stereopsis

Depth perception and stereopsis are crucial for navigating our 3D world. Our brain combines info from both eyes to create a sense of depth. This process, called stereopsis, relies on the slight differences in what each eye sees.

But it's not just about two eyes. Even with one eye, we can judge depth using cues like occlusion and perspective. These tricks help us understand spatial relationships and distances in our environment.

Binocular Vision and Stereopsis

Binocular Disparity and Stereopsis

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Top images from around the web for Binocular Disparity and Stereopsis

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  Stereo Depth Cues – Introduction to Sensation and Perception View original

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  Frontiers | Contextual Cueing Effect in Spatial Layout Defined by Binocular Disparity View original

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  Frontiers | Neural circuits for binocular vision: Ocular dominance, interocular matching, and ... View original

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  Stereo Depth Cues – Introduction to Sensation and Perception View original

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  Frontiers | Contextual Cueing Effect in Spatial Layout Defined by Binocular Disparity View original

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• Binocular disparity refers to the slight difference in the images seen by the left and right eyes due to their horizontal separation
  • This disparity allows the brain to extract depth information and create a three-dimensional perception of the world
• Stereopsis is the perception of depth and three-dimensional structure obtained on the basis of visual information deriving from two eyes by individuals with normally developed binocular vision
  • Stereopsis relies on the brain's ability to process and integrate the slightly different images from each eye (binocular disparity)
  • Enables the perception of depth, distance, and three-dimensional shape of objects
  • Provides a rich and detailed sense of the spatial layout of the environment (enhances depth perception compared to monocular vision)

Convergence and Parallax in Binocular Vision

• Convergence is the simultaneous inward movement of both eyes toward each other, usually in an effort to maintain single binocular vision when viewing an object
  • The eyes converge more when looking at closer objects and less when looking at distant objects
  • Provides a cue for depth perception based on the angle of convergence (the closer the object, the greater the convergence)
• Parallax refers to the apparent displacement or difference in the apparent position of an object viewed along two different lines of sight
  • Objects closer to the viewer have a larger parallax than objects farther away
  • The brain uses this difference in parallax to estimate the relative depth and distance of objects (motion parallax)
  • Parallax can be observed by alternately closing one eye while keeping the other open (monocular parallax)

Monocular Depth Cues

Occlusion and Perspective

• Occlusion occurs when one object partially or fully covers another object from view
  • If one object partially hides another, the occluded object is perceived as being farther away
  • Provides relative depth information based on which objects are in front of or behind others (a cue for depth ordering)
• Perspective refers to the way objects appear smaller as their distance from the observer increases
  • Parallel lines (like railroad tracks) appear to converge in the distance at a vanishing point on the horizon
  • Objects of known size appear smaller when they are farther away (relative size cue)
  • The position of an object relative to the horizon can provide a cue for its distance (height in the visual field)

Texture Gradient and Motion Parallax

• Texture gradient is a depth cue in which the apparent texture of an object or surface changes as a function of distance from the viewer
  • Texture appears more detailed and distinct for closer objects and becomes progressively less detailed and more uniform for distant objects
  • The rate at which texture changes (texture density) provides a cue for the relative distance and depth of surfaces
• Motion parallax is a depth cue that relies on the relative motion of objects against a background due to the motion of the observer
  • As an observer moves, objects that are closer appear to move more quickly relative to the background than objects that are farther away
  • The brain uses this relative motion to infer the relative depth and distance of objects in the environment
  • Motion parallax can be a powerful cue for depth perception, especially in the absence of other depth cues (during movement or in low light conditions)