Download 2320Lecture12

Binocular Disparity
• points nearer than
horopter have crossed
disparity
• points farther than
horopter 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
separate
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
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 face to the
right; left eye sees face 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 face to the
left; left eye sees face 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
• Optically separate images aren’t needed
• WARNING! Confusing stuff coming in the
next slides
Autostereograms
• Optically separate images aren’t needed
• WARNING! Confusing stuff coming in the
next slides
• Keep the definitions of convergence and
disparity separate.
Autostereograms
•right-eye line of sight
crosses left-eye line of sight
in front of image
•What would you see?
crossed convergence
Autostereograms
•Right eye sees face shifted
to right; left eye sees face
shifted to left therefore:
uncrossed disparity
•Face appears behind square
crossed convergence
Autostereograms
Crossed convergence shifts right retinal image to
the right of the left image and vice versa:
Left Eye’s Image
Right Eye’s Image
Autostereograms
What would happen if the convergence was
uncrossed?
Autostereograms
Uncrossed convergence shifts right-eye’s image to the
left of the left-eye image and vice versa:
Left Eye
Right Eye
Autostereograms
What would happen if the faces were switched relative
to the boxes?
Autostereograms
• one doesn’t even need two different images!
Autostereograms
RIGHT EYE
LEFT EYE
Convergence tells your brain that the plane of the image
is behind the plane of the surface
Next Time:
• Read Pinker !!