Post on 18-Dec-2015
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 Stereogramsin
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
Left Eye Right EyeDivider
•Right eye sees same image as left eye
•Face appears in same plane as square
Stereograms
Left Eye Right EyeDivider
What would you see?
Stereograms
Left Eye Right EyeDivider
•Right eye sees image to the right; left eye sees image to the left therefore:uncrossed disparity
•Face appears behind the square
Stereograms
Left Eye Right EyeDivider
What would you see?
Stereograms
Left Eye Right EyeDivider
•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
Left Eye Right Eye
What the image is doing:
What the eyes are doing:
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
Left EyeRight Eye
What the images are doing:
What the eyes are doing:
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