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Vision Lecture 7 Notes: Depth Perception

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Vision Lecture 7 Notes: Depth Perception Depth perception 1 Images removed due to copyright restrictions. Please refer to lecture video 2 Cues used for coding depth in the brain Oculomotor cues Visual cues accommodation Binocular vergence stereopsis Monocular motion parallax shading interposition size perspective 3 Stereopsis, basic facts and demos 4 Two simple methods for creating stereo images 1 2 stereo camera swiveled regular camera 5 Image is in public domain. Demos, page 1 6 Images removed due to copyright restrictions. Please see lecture video or Figure 1 of Schiller, Peter H., Geoffrey L. Kendall, et al. "Depth Perception, Binocular Integration and Hand-Eye Coordination in Intact and Stereo Impaired Human Subjects." Journal of Clinical & Experimental Ophthalmology 3, (210). Demos, page 1 & 2 7 Autostereogram from Magic Eye Images removed due to copyright restrictions. Please see lecture video or the autostereogram from The Magic Eye, Volume I: A New Way of Looking at the World. Andrews McMeel Publishing, 1993. Autostereograms: see Howard and Rogers, Depth Perception, Vol 2, pp. 549-556. Demos, page 3 8 Retinal disparity utilized for stereopsis Target hits corresponding retinal points Target hits non-corresponding retinal points target fix fix target Vieth-Muller circle y y x x x = y x = y 9 Stereopsis, neuronal responses 10 V1 cell response to drifting bars at varied stereo depths 0.58 +6.0 +4.0 0.21 +2.0 +1.5 +1.0 +0.5 _ 0 38 + 0 -0.5 Depth (cm) -1.0 Disparity (degree) -1.5 -0.23 -2.0 -4.0 -6.0 -1.13 -8.0 -10O 3O 0 1 2 O sec 0.14 Image by MIT OpenCourseWare. 11 V1 cell response to drifting bars at varied stereo depths 0.88 +10.0 +8.0 +6.0 +4.0 0.31 +3.0 +2.0 +1.0 +1.0 _ 0 38 + 0 Depth (cm) -0.5 Disparity (degree) -1.0 -0.23 -2.0 -4.0 -6.0 -1.13 -8.0 0 4O 0 1 2 3 0.18o sec R 38 L Key down Image by MIT OpenCourseWare. 12 Basic cell types for stereo Tuned excitatory far Tuned excitatory near Tuned excitatory zero 100 150 100 125 75 75 100 50 75 50 50 25 25 L R 25 0 0 0 .10 .05 00 05 10 .10 .05 00 05 10 .05 00 05 100 75 100 Tuned inhibitory Far Neural responses (impulses per sec) Near 75 75 50 50 50 25 25 25 0 0 0 .10 .05 00 05 10 .10 .05 00 05 10 .10 .05 00 05 10 Horizontal display (deg) Image by MIT OpenCourseWare. 13 Basic cell types for stereo Tuned excitatory Near ] Far Neural activity ] Tuned inhibitory Near Fixation point Far Depth Image by MIT OpenCourseWare. 14 The effects of V4 and MT lesions on stereoscopic depth perception 15 Images removed due to copyright restrictions. Please see lecture video or Figure 1 of Schiller, Peter H., Geoffrey L. Kendall, et al. "Depth Perception, Binocular Integration and Hand-Eye Coordination in Intact and Stereo Impaired Human Subjects. "Journal of Clinical & Experimental Ophthalmology 3, (210). 16 Stereopsis Graphs removed due to copyright restrictions. Please see lecture video or Schiller, Peter H. "The Effects of V4 and Middle Temporal (MT) Area Lesions on Visual Performance in the Rhesus Monkey." Visual Neuroscience 10, no. 4 (1993): 717-46. 17 Motion parallax 18 MOTION PARALLAX, the eye is stationary A B C Velocity of motion: A fastest, C slowest, creating velocity gradient With rigidity constraint highest relative velocity is judged to be closest 19 MOTION PARALLAX, the eye tracks 1 a 2 b eye movement object motion a 1 The eye tracks the circle, which therefore remains stationary on the fovea Objects nearer than the one tracked move 2 b at greater velocities on the retinal surface than objects further; the further objects actually move in the opposite direction on the retina. 20 21 Motion parallax To derive depth information from motion parallax neurons are needed that provide information about velocity and direction of motion and perhaps also about differential motion. The majority of cells in V1 are direction and velocity selective. Some appear also to be selective for differential motion. Cells that process motion parallax have also been found in MT. 22 Brain activation by stereopsis and motion parallax in normal and stereoblind subjects with fMRI 23 Images are projected here 24 25 A: Stereo 27 B: Parallax 28 C: Stereo + Parallax 29 Shading 30 31 32 TheThe powerpower ofof shadingshading forfor depthdepth perceptionperception 33 Examples of the 12 different shadings used 34 The next five displays have identical, repeating elements which are shaded differently in each set yielding a variety of stable and conflicting percepts 35 36 37 38 39 40 Stereo and shading in harmony and in conflict Demos, page 4-7 41 f f f 42 43 44 Putting stereo, parallax and shading together 45 3HUFHSWLRQ 35, no. 11 (2006): 1521. about the visual system." about the Image removed due to copyright restrictions. Please see lecture video or see Display 24 of Schiller, Peter H., and Christina E. Carvey. "Demonstrations of Spatiotemporal Integration and What they Tell us About the Visual System." Perception 35, no. 11 (2006): 1521. 46 Separate and combined disparity, parallax and shading depth cues Graphs removed due to copyright restrictions. Please see lecture video or Figure 3a,b of Schiller, Peter H., Warren M. Slocum, et al. "The Integration of Disparity, Shading and Motion Parallax Cues for Depth Perception in Humans and Monkeys." Brain Research 1377 (2011): 67-77. 47 Perspective 48 Image removed due to copyright restrictions. Please see lecture video or see William O'Brian, "Because it's here, that's why," New Yorker, September 21, 1963, 42. 49 50 51 52 53 Perspective illusion 54 55 The Savage family Painting is in public domain. Edward Savage 56 Hand-eye coordination and Binocular integration tests 57 Needle test 58 Movie of needle test needle_binoc needle_monoc 59 Touch-panel test 60 Examples of test of binocular integration 61 Binocular integration test, figures A B 62 Binocular integration test, words S U D T R Y A S U D T R Y B SSTT UU RR DD YY SSTT UU RR DD YY 63 Summary, depth: 1. Numerous mechanisms for analyzing depth have been identified that include vergence and accommodation, stereopsis, parallax, shading, and perspective. 2. Several cortical structures process stereopsis utilizing disparity information; the number of disparities represented is limited as in the case of color coding. 3. Utilizing motion parallax for depth processing necessitates neurons specific for direction, velocity and differential velocity; several areas, including V1 and MT process motion parallax. 4. Area MT contributes to the analysis of motion, motion parallax, depth, and flicker; however, these analyses are also carried out by several other structures. 5. Litte is known at present about the manner in which information about shading and perspective is analyzed by the brain. 64 MIT OpenCourseWare http://ocw.mit.edu 9.04 Sensory Systems Fall 2013 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms..
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