Test 1

1. Test 1 • Covers material through fixation disparity • 20 multiple choice questions • Study guide questions and problem set • Do not need to know formula for calculating the amount of fixation disparity.

2. Cues to Depth

4. What happens when you close one eye? • Still appreciate depth • Monocular cues help us with depth perception. • Patient’s often confused about this.

5. Characteristics • Cues not hard wired • Learned inferences that the visual system makes.

6. Monocular Cues to Depth in a deprived environment • Retinal image size-this cue works when other cues are absent • Emmert’s law – the perceived size of the object producing a retinal image of given fixed size is proportional to its perceived distance.

7. Emmert’s Law • Example • Afterimage

9. Problem with using retinal images • We do not perceive real life objects based on visual angle. • Familiar objects would be growing or shrinking • Need an invariant or constant to compensate for retinal image size

10. Holway/Boring Experiment

12. Size Constancy • Perception needs to account for both distance and retinal size • S=K(RxD) • S is perceived size • K is a constant • R is retinal image size • D is perceived distance

13. Monocular Cues in Natural Setting • See website this is different than in lecture notes. • http://sites.sinauer.com/wolfe3e/chap6/startF.htm

14. Stereopsis • This is true depth perception. • Preattentive

15. Absolute Depth • Distance from egocentric position • More dependant on monocular cues

16. Relative Depth • Objects in relation to each other • Stereopsis ideal for detecting this

19. Types of Disparity • Horizontal vs. vertical disparity • Other types of disparity • Disparity gradients give rise to tilted surfaces • Orientation disparity

22. Types of Disparity • Horizontal vs. vertical disparity • Other types of disparity • Disparity gradients give rise to tilted surfaces • Orientation disparity

24. Special Cases • Chromostereopsis • Result of chromatic aberration • Longitudinal vs transverse

28. Stereoacuity • Depth discrimination threshold • Hyperacuity similar to vernier acuity – can get 4 to 5 seconds of arc

29. Howard-Dolman • Calculating disparity – Howard Dolman Apparatus • n = 2a/2.9 x 10-4 x d/d2 • n = angular stereoscopic disparity in radians • 2a = interpupillary distance • d = fixation distance • change in d = linear distance between the two rods

34. Characteristics • Effect of exposure time • Retinal eccentricity • Background illumination

38. Measuring Stereoacuity • Howard Dolman apparatus • Method of adjustment • Method of limits

41. Stereopsis upper limit • Patent or quantitative stereopsis • Latent or qualitative stereopsis

43. Purpose of coarse stereo • Processing of depth outside the horopter • Cue for the vergence system • Back up stereo system • May be primary stereo signal for small angle strabismus.

44. Stereo Targets • Local stereopsis • Line targets • Provides monocular cues • Best used for Stereoacuity measures

46. Global Stereopsis • Random dot stereogram – provides no monocular cues to depth • May play a role in detecting camouflaged object • Targets have to be fused for form perception to occur

50. Characteristics • Stereo correspondence problem or how does the visual system decide which dots to fuse. • The visual system yields the best global interpretation of depth • Depth averaging