CAS PS 222 Lecture Notes - Lecture 9: Retina, Visual System, Stereopsis
18 May 2018
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Binocular or retinal disparity:
There are monocular cues to depth as well. There are multiple cues that we can use with just one
eyes. But that does’t gie us the est alulatios. The fat that e hae the to eyes, offset at
a particular distance, we use that information to precisely get information of the depth
Offset means: Both the eyes are taking videos from two different angles.
And because the distance from the two eyes is always fixed, we can use that information to
precisely compute where objects are in depth.
We have two different images on two different retinas.
The difference between the two images is called retinal disparity.
Retinal Disparity: The relative positions of two images in the two retinae.
Depth from Retinal Disparity
How do we compute depth from retinal disparity?
- We need to compute how the two points falls on the two retinae. Then you use the
information to understand depth
- What is in the image on the retinae? – a 2D image of a 3D world. 2 images taken from
slightly different angles
- Where is the image of the object on the 2 retinae? – the fovea. When you fixate on an
object, that object falls on the two foveae which means it is falling on the same point of
each retina. There are called corresponding point
- The location of the image on Retina 1 is the same location of Retina 2. Fixation is an
example of it. There is zero disparity.
- If you sketch an imaginary sphere that goes through the fixation point, everything on the
sphere falls on the corresponding point. Its called the
- Horoptor: anything that falls outside or inside the imaginary sphere, the image of that
object will be projected to different points in the Retina. Those are non-corresponding
points
- This yields retinal disparity different than 0.
Things in front of fixation point, look as if they are passing over the fixation point. What does it
mean for retinal disparity?
3 types of retinal disparity?
- Zero Disparity
- Crossed Disparity: Objects nearer the fixation point: crosses over the object. OBJECT NEAR
THE FIXATION POINT
- Uncrossed Disparity: Objects further from the fixation point. If you are looking at the
fixated object, anything beyond the horoptor, If looked at from right eye, the object is on
the right. Similarly for the left. OBJECT FAR FROM THE FIXATION point
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Document Summary
There are monocular cues to depth as well. There are multiple cues that we can use with just one eyes. But that does(cid:374)"t gi(cid:448)e us the (cid:271)est (cid:272)al(cid:272)ulatio(cid:374)s. the fa(cid:272)t that (cid:449)e ha(cid:448)e the t(cid:449)o eyes, offset at a particular distance, we use that information to precisely get information of the depth. And because the distance from the two eyes is always fixed, we can use that information to precisely compute where objects are in depth. We have two different images on two different retinas. The difference between the two images is called retinal disparity. Retinal disparity: the relative positions of two images in the two retinae. How do we compute depth from retinal disparity? taking videos from. We need to compute how the two points falls on the two retinae. Then you use the information to understand depth. A 2d image of a 3d world.
