Binocular Disparity

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(No Transcript)
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Binocular Disparity

• points nearer than horopter have crossed
  disparity
• points farther than horopter have uncrossed
  disparity

The Horopter
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Binocular Disparity

• Why dont we see double vision?

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Binocular Disparity

• Why dont we see double vision?
• Images with a small enough disparity are fused
  into a single image

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Binocular Disparity

• Why dont 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
  Panums Area

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Binocular Disparity

• Panums Area extends just in front of and just
  behind the horopter

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Binocular Disparity

• Panums Area extends just in front of and just
  behind the horopter
• Images outside of Panums area are often blurry
  because accommodation is reflexively set
  according to vergence

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Stereopsis

• Our brains interpret crossed and uncrossed
  disparity as depth
• That process is called stereoscopic depth
  perception or simply stereopsis

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Stereopsis

• Stereopsis requires that the brain can encode the
  two retinal images independently

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Stereopsis

• Primary Visual cortex normally keeps input from
  the eyes separate
• If normal input is restricted during development,
  the cortical representation of the bad eye is
  reduced
• Amblyopia can result

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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

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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 dont lock onto the same
  point
• anisometropia - when one eye has very bad optics
  and the other is normal

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Amblyopia

• People with Amblyopia cant see stereograms

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Stereograms

• seeing depth requires only two different images
  on the retina

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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

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Presenting Binocular Images

• Various ways to add depth
• 1. Stereoscope

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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

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Stereograms
Divider
Left Eye
Right Eye
What would you see?
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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

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Presenting Binocular Images

• Various ways to add depth
• glasses with different lenses

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Presenting Binocular Images

• Various ways to add depth
• glasses with different lenses

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Presenting Binocular Images

• Various ways to add depth
• glasses with different lenses

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Presenting Binocular Images

• Various ways to add depth
• LCD Shutter Glasses

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Gregory
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Science

• Science is like a set of procedures

Make a Hypothesis
Identify a question
Make a Prediction
Prediction Fails
Prediction holds
Test It
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Example The horizontal-vertical illusion
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Example The horizontal-vertical illusion

• Question

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Example The horizontal-vertical illusion

• Question Why does the vertical line seem longer?
• Hypothesis

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Example The horizontal-vertical illusion

• Question Why does the vertical line seem longer?
• Hypothesis Wundt -gt vertical and horizontal eye
  movements scan the image differently
• Prediction

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Example The horizontal-vertical illusion

• Question Why does the vertical line seem longer?
• Hypothesis Wundt -gt vertical and horizontal eye
  movements scan the image differently
• Prediction Stabilized image should eliminate the
  illusion
• Test

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Example The horizontal-vertical illusion

• Question Why does the vertical line seem longer?
• Hypothesis Wundt -gt vertical and horizontal eye
  movements scan the image differently
• Prediction Stabilized image should eliminate the
  illusion
• Test Illusion is still present in afterimage!