1. Vision Overview 18 September 2006

2. Eye: Musculature

3. The eye and retina

4. Eye: Internal Structure 2/3 focusing in first ½ mm Flexible lens fine tunes focus Myopia focuses is before retina Presbyopia focuses behind retina Cataracts are opaque flaws in lens Iris varies from 2-8mm About 17mm from lens to retina Curved image surface

5. Retina 120e6 rod cells (scotopic vision) 6e6 cone cells (photopic vision) Sensors operate by polarization of proteins by photons Produce a “pulse train” with rate proportional to log of intensity

6. Rods and cones density in the retina

7. Blind Spot

8. Eye and Brain About 1e6 nerves leave each eye Clearly a huge reduction has already been done Parts of visual field “cross over” for stereo processing Huge part of brain is devoted to processing Eyes best thought of as an extension of the brain

10. Retina Layers Light enters on the left! Sensors connected together into receptive fields Lateral inhibition Edge detectors, shape detectors, motion predictors Model with convolution

12. Dynamic Range 11 orders of magnitude! Single photons when dark adapted! Scotopic in the dark Photopic in the light Maybe only 20 levels at one point Maybe only 1000 levels at one average brightness

13. Visual Performance 20:20 vision corresponds to 1 arc minute Fovea: 20 minutes max density uniform, 2 degrees “rod-free” area 400 to 700 nanometer wavelength 510nm maximum rod sensitivity (green) 560nm maximum cone sensitivity (orange)

14. Contrast Sensitivity

15. Acuity away from center

16. Macular degeneration

17. A Model of Human Vision with Limited Feedback

18. Retinal sensors, preprocessing through LGN to V1 Receptive fields –Spatial and temporal derivatives Spatial derivatives are oriented –Other than blob sensors (Laplacian) »Intensity boundary sensors ( G u ) »Bar sensors ( G uu ) –Spatial scales (aperture size;  of Gaussian)

19. Receptive Fields

20. Combining Receptive Fields Receptive Fields are combined in many ways to produce orientation sensitive detectors

21. Temporal Aspects of Vision Object motion Egomotion Flicker –Minor nit with article text: When a monitor refreshes at 60Hz it flickers at 60Hz. But a conventional incandescent light driven by 60Hz AC flickers at 120Hz. Why? Saccades

22. Motion Detection

23. Perception of Brightness Affected strongly by boundariness signals of form system Determined by relative intensity changes –Weber’s law: just noticeable difference constant  I/I –Averaging within boundaries –Enhancement/sharpening at boundaries Mach effect

24. Weber’s Law Just noticeable differences

25. Mach Effect

26. “Simultaneous Contrast” -- Brightness Determined by Relative Luminance

27. Discontinuity effects

28. Adelson’s Shadow

29. Hermann grid

30. Perception of Color Trichromatic color mixtures Intensity + 2 chromanences –Red-green (R/(R+G)), Blue-Yellow (B/(R+G)) Affected strongly by boundariness signals of form system Determined by relative chromanence changes –Averaging within boundaries –Enhancement/sharpening at boundaries

31. Spectral Sensitivity

32. Opponent Color Model

33. Color blindness

34. Color Constancy Volunteers needed to reproduce Land’s Mondrian Experiment

35. What is this?

36. How about this?

37. After-Effects Stare at the center dot then switch to the next slide

38. After-Effects

39. Form System Suggests Continuations

40. Both inputs and expectations drive what you see

41. Seeing in 3D Static monocular cues –Occlusion –Relative height –Familiar size –Texture gradient –Shadow –Linear perspective Motion parallax Stereo Oculomotor feedback –Vergence –Accommodation

42. Stereo Random dot stereogram from Foundations of Cyclopean Perception by Bela Julesz Where must stereo correlation happen?

43. Types of 3D display Nice 2D rendering –perspective –shading –relative size –occlusion

44. Stereo Display Color Polarization Shutter Autostereo

45. Head-Tracked Stereo Display Stereo using any of the earlier methods Track head and update image Otherwise, object appears to warp as you move your head

46. Barrier Autostereo

47. Lenticular Autostereo

48. Time Multiplexed Autostereo

49. Head-mounted Display Present images directly to eyes Track head Update images with motion

50. Reimaging Display

51. Varifocal Mirror

52. Volumetric

53. Holograms

54. Pulfrich Effect Video

55. Volunteer opportunities Edwin Land’s Mondrian experiment (Kyle) Bela Julesz random dot stereograms Varifocal mirror

56. Will this be on the test? Yes! Anything is fair game But what I emphasize is more likely Unlikely: How do reimaging displays work? Likely: Apply Weber’s law to some thought experiment.