This document discusses depth perception and stereoscopic vision. It begins by outlining several visual cues that provide information about 3D shape and depth, including motion, size, perspective, texture perspective, occlusion, and shading. It then focuses on stereopsis, or 3D vision from slight differences in left and right eye images. It describes disparity, or differences in feature positions between the two eyes, and how the magnitude of disparity signifies depth. It discusses Sir Charles Wheatstone's invention that demonstrated stereopsis, and random-dot stereograms. It examines how the brain matches features between the eyes to solve stereopsis, and what happens when matches cannot be found. It also looks at the neural bases of disparity registration and

1. Depth Perception, with Emphasis on
Stereoscopic Vision
Randolph Blake
Visual System, Spring Semester
March 24, 2003
http://www.psy.vanderbilt.edu/faculty/blake/StereoStuff/Stereopsis.htm
Chapter 10 in McIlwain and Chapter 11 in Tovee

2. Specifying 3D shape and depth relations
• motion

3. Specifying 3D shape and depth relations
• motion

4. Specifying 3D shape and depth relations
• motion

5. Specifying 3D shape and depth relations
• motion
• size

6. Specifying 3D shape and depth relations
• motion
• size
• perspective

7. Specifying 3D shape and depth relations
• motion
• size
• perspective

8. Specifying 3D shape and depth relations
• motion
• size
• perspective

9. Specifying 3D shape and depth relations
• motion
• size
• perspective
• texture perspective

10. Specifying 3D shape and depth relations
• motion
• size
• perspective
• texture perspective
• occlusion

11. Specifying 3D shape and depth relations
• motion
• size
• perspective
• texture perspective
• occlusion
• shading

12. Specifying 3D shape and depth relations
• motion
• size
• perspective
• texture perspective
• occlusion
• shading

13. Specifying 3D shape and depth relations
• motion
• size
• perspective
• texture perspective
• occlusion
• shading

15. Sir Charles Wheatstone’s Famous Invention

16. Stereograms (anaglyphs)

17. Stereograms (“Magic Eye”)

18. Stereopsis (literally, “seeing solid”)- 3D vision resulting from slight
differences in left and right eye images, arising because the two eyes
view the world from slightly different perspectives
Disparity - slight differences in positions of
“features” in left and right eye views
• crossed disparity
• uncrossed disparity
• zero disparity

19. Magnitude of Disparity Signifies Depth Difference

20. Disparity Magnitude Also Varies with Viewing
Distance
stereopsis works only within 10 - 20 ft of the
observer; once the visual axes are parallel,
objects beyond the point of fixation provide no
disparity

21. Magnitude of Disparity Depends on “IPD”
“ipd” = interpupillary distance (averages 6.5 cm in humans)

22. Random-dot Stereograms (Julesz, 1971)

23. How They’re Made

24. How They’re Made

25. How They’re Made

28. How Does the Brain “Solve” This Problem?

29. What “features” does the brain match for stereopsis?
“low” spatial frequencies
“high” spatial frequencies”
original images

30. What Happens When Binocular Matches
Cannot Be Found?
left eye right eye

31. Binocular Rivalry

32. Neural Bases of Disparity Registration

33. Neural Bases of Disparity Registration

34. Neural Bases of Disparity Registration
zero disparity

35. Neural Bases of Disparity Registration
uncrossed disparity

36. Neural Bases of Disparity Registration
uncrossed disparity

37. Neural Bases of Disparity Registration

38. Neural Bases of Disparity Registration
“crossed disparity

39. Neural Bases of Disparity Registration
“crossed disparity

40. NO! Disparity must be scaled for distance. (Recall that a given
disparity can be associated with different depth intervals,
depending on viewing distance and on IPD.)
Non-stereoscopic cues required for this “depth
scaling”
Neurons in visual cortex can match features
between the two eyes and can “compute” retinal
disparity. Is the problem of stereopsis solved?

41. http://www.3d-web.com/index.html
http://www.stereographics.com/
http://www.psy.vanderbilt.edu/faculty/blake/StereoStuff/Stereopsis.htm