Transcript 2320Lecture15

Binocular Disparity
• points (C) nearer than
fixation (P) have
crossed disparity
• points (F) farther than
fixation have uncrossed
disparity
Binocular Disparity
• Why don’t we see double vision?
Binocular Disparity
• Why don’t we see double vision?
• Images with a small enough disparity are
fused into a single image
Binocular Disparity
• Why don’t we see double vision?
• Images with a small enough disparity are
fused into a single image
• The region of space that contains images
with close enough disparity to be fused is
called Panum’s Area
Binocular Disparity
• Panum’s Area
extends just in front
of and just behind the
horopter
Stereopsis
• Our brains interpret crossed and
uncrossed disparity as depth
• That process is called stereoscopic depth
perception or simply stereopsis
Stereopsis
• Stereopsis requires that the brain can
encode the two retinal images
independently
Stereopsis
• Primary visual cortex (V1) has bands of
neurons that keep input from the two eyes
seperate
Stereopsis
• If the brain only
gets normal
signals from one
eye early in life,
that eye’s neurons
crowd out the
other eye’s
neurons
Amblyopia
• Amblyopia is a visual deficit in which
one eye has poor vision because the brain
never developed the ability to use signals
from that retina
Amblyopia
• Amblyopia is a visual deficit in which
one eye has poor vision because the brain
never developed the ability to use signals
from that retina
• Usually caused by
– strabismus - when eyes don’t lock onto the
same point
– anisometropia - when one eye has very bad
optics and the other is normal
3-D Stereograms
in
Pinker: How the mind works
Infinity of Interpretations
• There are an infinite number of
interpretations of the 2D pattern of light on
the retina
Infinity of Interpretations
• There are an infinite number of
interpretations of the 2D pattern of light on
the retina
• The brain selects one that matches with
common experience
Infinity of Interpretations
• There are an infinite number of
interpretations of the 2D pattern of light on
the retina
• The brain selects one that matches with
common experience
• Ames Room is example of how this can
lead to an illusion
Infinity of Interpretations
• Ames Room
Adding stereoscopic depth cues
to 2D pictures
Stereograms
• seeing depth requires “only” two different
images on the retina
Stereograms
• seeing depth requires
“only” two different
images on the retina
• this could be
accomplished by an
optical device that
projects separate images
into the two eyes
Stereograms
Divider
Left Eye
Right Eye
•Right eye sees same image
as left eye
•Face appears in same plane
as square
Stereograms
Divider
Left Eye
Right Eye
What would you see?
Stereograms
Divider
Left Eye
Right Eye
•Right eye sees image to the
right; left eye sees image to
the left therefore:
uncrossed disparity
•Face appears behind the
square
Stereograms
Divider
Left Eye
Right Eye
What would you see?
Stereograms
Divider
Left Eye
Right Eye
•Right eye sees image to the
left; left eye sees image to
the right therefore:
crossed disparity
•Face appears in front of
square
Presenting Binocular Images
• Various ways to add depth:
– 1. Stereoscope
Presenting Binocular Images
• Various ways to add depth:
– 2. glasses with different lenses
Presenting Binocular Images
• Various ways to add depth:
– 2. glasses with different lenses
Presenting Binocular Images
• Various ways to add
depth:
– 2. glasses with
different lenses
Presenting Binocular Images
• Various ways to add depth:
– 3. LCD Shutter Glasses
Autostereograms
• Optically separate images aren’t needed
Autostereograms
•Right eye sees image to the
right; left eye sees image to
the left therefore:
uncrossed disparity
•Face appears behind square
crossed convergence
Autostereograms
What the image is doing:
Left Eye
What the eyes
are doing:
Right Eye
Autostereograms
•Right eye sees image to the
left; left eye sees image to
the right therefore:
crossed disparity
•Face appears in front of
square
uncrossed convergence
Autostereograms
What the images are doing:
Right Eye
What the eyes
are doing:
Left Eye
Autostereograms
• one doesn’t even need two different images!
RIGHT EYE
LEFT EYE
Convergence tells your brain that the plane of the image
is behind the plane of the surface