Just another teaser

[Tom22]

Not really just some questions

 

Why is it when I come in for a landing my perception of the landing zone stays the same even though the image on my retina changes (gets larger).That is the proximal sensation of the distant object changes. And I know depth perception is one element involved but I see the world in 3-D and the image on my retina is only in 2-D, so how is it that I see 3-D to judge distance.

Edited April 11, 2011 by Tom22

[helistar]

Cool question...

The fact that we have two eyes (binocular vision) also provide information on distance. One of these binocular distance cues is called convergence. Convergence refers to the turning in of our eyes as objects come closer to our eyes. The other thing that happens as objects come closer is that our accommodation changes. There is a change of focus that occurs when the lens gets fatter for nearby objects..

 

You can learn everything you ever wanted to know about depth perception @ http://www.yorku.ca/eye/toc.htm

 

 

Additional info:

The retina is a multi-layered sensory tissue that lines the back of the eye. It contains millions of photoreceptors that capture light rays and convert them into electrical impulses. These impulses travel along the optic nerve to the brain where they are turned into images.

 

There are two types of photoreceptors in the retina: rods and cones. The retina contains approximately 6 million cones. The cones are contained in the macula, the portion of the retina responsible for central vision. They are most densely packed within the fovea, the very center portion of the macula. Cones function best in bright light and allow us to appreciate color.

 

There are approximately 125 million rods. They are spread throughout the peripheral retina and function best in dim lighting. The rods are responsible for peripheral and night vision.

[SBuzzkill]

I am under the impression that binocular cues are only used at close ranges and that the distances we view things from a helicopter cause us to use monocular cues.

[helistar]

Another way to consider the condition that the further away objects are the smaller their visual angle, or the smaller their image on your retina is with a perspective illusion. That the lines radiate to some common point in the distance is called perspective. Because the rectangular blocks are actually all the same size, the ones further away seem larger because the conflict with the perspective information.

 

The fact that we have two eyes (binocular vision) also provides information on distance. One of these binocular distance cues is called convergence. Convergence refers to the turning in of our eyes as objects come closer to our eyes. The other thing that happens as objects come closer is that our accommodation changes. There is a change of focus that occurs when the lens gets fatter for nearby objects.

 

Another cue to distance perception especially for more complex scenes in which there are multiple objects is binocular disparity.

 

Yet another cue to distance is motion parallax. As you move from one location to another objects at various distances will move in a direction dependent on where you are fixating.

 

Finally, it turns out that color and brightness can have an effect on how far away something appears.

[helistar]

The eye flips the image of the world.

The retina distorts this image, magnifying that falling on the fovea.

The images from the two eyes are combined in primary visual cortex. The left cortex codes images seen on one’s right side (by both eyes).

 

By comparing these two images, depth is computed.

Primary visual cortex separates the image into distinct feature channels. Different groups of cells work collectively to extract each feature.

1) Cells in the blobs extract color.

2) Binocular cells compute the retinal disparity and thus depth.

3) Simple and complex cell are activated by edges of particular orientations and their motion.

[helistar]

Stereopsis refers to our ability to appreciate depth, that is the ability to distinguish the relative distance of objects with an apparent physical displacement between the objects. It is possible to appreciate the relative location of objects using one eye (monocular cues). However, it is the lateral displacement of the eyes that provides two slightly different views of the same object (disparate images) and allow acute stereoscopic depth discrimination.

 

I am under the impression that binocular cues are only used at close ranges and that the distances we view things from a helicopter cause us to use monocular cues.

[SBuzzkill]

Makes sense.

[Tom22]

Thanks for participating, good information!

 

This is what I think the answers are without going into detail about what cells respond to what stimulus and the processing in the brain. Although, one aspect about visual processing that I found interesting was the antagonistic way (on off responses) retinal ganglion cells respond to light changes.

 

Anyway, perceptual constancies of size and shape are the reason why the landing zone is perceived the same size even though the object becomes larger on my retina.

 

Depth Perception includes monocular and binocular depth cues that our brain uses to see 3-D:

 

Monocular Depth Cues

 

Texture gradients

 

Relative Size

 

Linear perspective

 

Aerial perceptive

 

Location in the picture plane

 

Motion parallax

 

Binocular Depth Cues

 

Binocular convergence

 

Binocular disparity

[helistar]

Anytime Tom...

 

Here's some additional information I'm sure your aware of, however other following this thread might find interesting...

 

Binocular Disparity

Perhaps the most important perceptual cues of distance and depth depend on so-called binocular disparity. Because our eyes are spaced apart, the left and right retinas receive slightly different images. This difference in the left and right images is called binocular disparity. The brain integrates these two images into a single three-dimensional image, allowing us to perceive depth and distance. The phenomenon of binocular disparity functions primarily in near space because with objects at considerable distances from the viewer the angular difference between the two retinal images diminishes.

 

 

Monocular Disparity

 

Monocular cues are cues to depth that are effective when viewed with only one eye. Although there are many kinds of monocular cues, the most important are interposition, atmospheric perspective, texture gradient, linear perspective, size cues, height cues, and motion parallax.

 

Interposition: Probably the most important monocular cue is interposition, or overlap. When one object overlaps or partly blocks our view of another object, we judge the covered object as being farther away from us.

 

Atmospheric Perspective: The air contains microscopic particles of dust and moisture that make distant objects look hazy or blurry. This effect is called atmospheric perspective, and we use it to judge distance.

 

Texture Gradient: A texture gradient arises whenever we view a surface from a slant, rather than directly from above. The texture becomes denser and less detailed as the surface recedes into the background, and this information helps us to judge depth.

 

Linear Perspective: Linear perspective refers to the fact that parallel lines, such as railroad tracks, appear to converge with distance, eventually reaching a vanishing point at the horizon. The more the lines converge, the farther away they appear.

 

Size Cues: Another visual cue to apparent depth is closely related to size constancy. If we assume that two objects are the same size, we perceive the object that casts a smaller retinal image as farther away than the object that casts a larger retinal image. This depth cue is known as relative size, because we consider the size of an object's retinal image relative to other objects when estimating its distance.

Another depth cue involves the familiar size of objects. Through experience, we become familiar with the standard size of certain objects. Knowing the size of these objects helps us judge our distance from them and from objects around them.

 

Height Cues: We perceive points nearer to the horizon as more distant than points that are farther away from the horizon. This means that below the horizon, objects higher in the visual field appear farther away than those that are lower. Above the horizon, objects lower in the visual field appear farther away than those that are higher. This depth cue is called relative height, because when judging an object's distance, we consider its height in our visual field relative to other objects.

 

Motion Parallax: Motion parallax appears when objects at different distances from you appear to move at different rates when you are in motion. The rate of an object's movement provides a cue to its distance. The more distant objects appear to move in a more slower pace.

[Goldy]

Anytime Tom...

 

Here's some additional information I'm sure your aware of, however other following this thread might find interesting...

 

Binocular Disparity

Perhaps the most important perceptual cues of distance and depth depend on so-called binocular disparity. Because our eyes are spaced apart, the left and right retinas receive slightly different images. This difference in the left and right images is called binocular disparity. The brain integrates these two images into a single three-dimensional image, allowing us to perceive depth and distance. The phenomenon of binocular disparity functions primarily in near space because with objects at considerable distances from the viewer the angular difference between the two retinal images diminishes.

 

 

Monocular Disparity

 

Monocular cues are cues to depth that are effective when viewed with only one eye. Although there are many kinds of monocular cues, the most important are interposition, atmospheric perspective, texture gradient, linear perspective, size cues, height cues, and motion parallax.

 

Interposition: Probably the most important monocular cue is interposition, or overlap. When one object overlaps or partly blocks our view of another object, we judge the covered object as being farther away from us.

 

Atmospheric Perspective: The air contains microscopic particles of dust and moisture that make distant objects look hazy or blurry. This effect is called atmospheric perspective, and we use it to judge distance.

 

Texture Gradient: A texture gradient arises whenever we view a surface from a slant, rather than directly from above. The texture becomes denser and less detailed as the surface recedes into the background, and this information helps us to judge depth.

 

Linear Perspective: Linear perspective refers to the fact that parallel lines, such as railroad tracks, appear to converge with distance, eventually reaching a vanishing point at the horizon. The more the lines converge, the farther away they appear.

 

Size Cues: Another visual cue to apparent depth is closely related to size constancy. If we assume that two objects are the same size, we perceive the object that casts a smaller retinal image as farther away than the object that casts a larger retinal image. This depth cue is known as relative size, because we consider the size of an object's retinal image relative to other objects when estimating its distance.

Another depth cue involves the familiar size of objects. Through experience, we become familiar with the standard size of certain objects. Knowing the size of these objects helps us judge our distance from them and from objects around them.

 

Height Cues: We perceive points nearer to the horizon as more distant than points that are farther away from the horizon. This means that below the horizon, objects higher in the visual field appear farther away than those that are lower. Above the horizon, objects lower in the visual field appear farther away than those that are higher. This depth cue is called relative height, because when judging an object's distance, we consider its height in our visual field relative to other objects.

 

Motion Parallax: Motion parallax appears when objects at different distances from you appear to move at different rates when you are in motion. The rate of an object's movement provides a cue to its distance. The more distant objects appear to move in a more slower pace.

 

Geez Helistar- Pre-med Opthalmology????

[helistar]

Geez Helistar- Pre-med Opthalmology????

 

Goldy,

At one time I did consider pre-med, however decided I would enjoy studying human factors in aviation... Human factors involves gathering information about human abilities, limitations, and other characteristics and applying it to tools, machines, systems, tasks, jobs, and environments to produce safe, comfortable, and effective human use...

 

In aviation, human factors is dedicated to better understanding how humans can most safely and efficiently be integrated with the technology... Because technology continues to evolve faster than the ability to predict how humans will interact with it, the industry can no longer depend as much on experience and intuition to guide decisions related to human performance... Instead, a sound scientific basis is necessary for assessing human performance implications in design, training, and procedures, just as developing a new wing requires sound aerodynamic engineering...