1. Binocular Disparity
points (C) nearer than fixation (P) have crossed disparity
points (F) farther than fixation have uncrossed disparity

2. Binocular Disparity
Why don’t we see double vision?

3. Binocular Disparity Why don’t we see double vision?
Images with a small enough disparity are fused into a single image

4. 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

5. Binocular Disparity
Panum’s Area extends just in front of and just behind the horopter

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

7. Stereopsis
Stereopsis requires that the brain can encode the two retinal images independently

8. Stereopsis
Primary visual cortex (V1) has bands of neurons that keep input from the two eyes seperate

9. 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

10. 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

11. 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

12. Pinker: How the mind works
3-D Stereograms in
Pinker: How the mind works

13. Infinity of Interpretations
There are an infinite number of interpretations of the 2D pattern of light on the retina

14. 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

15. 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

16. Infinity of Interpretations
Ames Room

17. Adding stereoscopic depth cues to 2D pictures

18. Stereograms
seeing depth requires “only” two different images on the retina

19. 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

20. Stereograms Divider Left Eye Right Eye
Right eye sees same image as left eye
Face appears in same plane as square

21. Stereograms
Divider
Left Eye
Right Eye
What would you see?

22. 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

23. Stereograms
Divider
Left Eye
Right Eye
What would you see?

24. 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

25. Presenting Binocular Images
Various ways to add depth:
1. Stereoscope

26. Presenting Binocular Images
Various ways to add depth:
2. glasses with different lenses

27. Presenting Binocular Images
Various ways to add depth:
2. glasses with different lenses

28. Presenting Binocular Images
Various ways to add depth:
2. glasses with different lenses

29. Presenting Binocular Images
Various ways to add depth:
3. LCD Shutter Glasses

30. Autostereograms
Optically separate images aren’t needed

31. Autostereograms
Right eye sees image to the right; left eye sees image to the left therefore:
uncrossed disparity
Face appears behind square
crossed convergence

32. Autostereograms What the image is doing: Left Eye Right Eye
What the eyes are doing:

33. 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

34. Autostereograms What the images are doing: Right Eye Left Eye
What the eyes are doing:

35. Autostereograms
one doesn’t even need two different images!

36. RIGHT EYE
LEFT EYE
Convergence tells your brain that the plane of the image is behind the plane of the surface