Human vision
description
Transcript of Human vision
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Human vision
Jitendra MalikU.C. Berkeley
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Cerebral Cortex
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Monocular Visual Field: 160 deg (w) X 175 deg (h)Binocular Visual Field: 200 deg (w) X 135 deg (h)
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Cones and Rods
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Receptor density vs eccentricity
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Processing in the retina
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ON and OFF cells in retinal ganglia
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Visual Processing Areas
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The visual system performs
• Measurement of light and spatial relations• Perceptual Organization• Active interaction with environment
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Measurement of light and spatial relations
• Measuring light– Sensitivity over high dynamic range– Gain control results in “Weber Machine”– Sensitivity to contrast rather than absolute
luminance level—discounting the illuminant• Measuring Spatial relations
– Contrast sensitivity function– Vernier Acuity
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Threshold vs. Intensity
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Weber Contrast Cw = ΔL/LMichelson Contrast CM = (Lmax – Lmin)/2 Lmean
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Why contrast is the right variable..
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Simultaneous Contrast
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Mach Band
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A Mach Band in 1D profile
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Craik-O’Brien-Cornsweet
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Contrast Sensitivity Function at different luminances
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Receptor density vs eccentricity
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CSF as function of eccentricity
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Cortical Magnification Factor
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Mapping from Retina to V1
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Physiological Optics 1840-1894
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The Empiricist-Nativist debate
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The debate..(and sometimes both were right !)
• Helmholtz argued that perception is unconscious inference. Associations are earned through experience.
• Hering proposed physiological mechanisms—opponent color channels, contrast mechanisms, conjunctive and sisjunctive eye movements..
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The Twentieth Century..
• The Gestalt movement emphasized perceptual organization.– Grouping– Figure/ground – Configuration effects on perception of
brightness and lightness
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Grouping factors
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Grouping Factors
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The Figure-Ground Problem
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Transparency
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Wallach’s Brightness ratios
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Gibson’s ecological optics (1950)
• Emphasized richness of information about shape and surface layout available to a moving observer– Optical flow– Texture Gradients– ( and the classical cues such as stereopsis etc)
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Measuring Surface Orientation
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Accomodation
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Depth of field of human eye
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Convergence
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Convergence angle vs. distance
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Binocular Stereopsis
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Optical flow for a pilot
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Some Pictorial Cues
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Shading
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Cast Shadows
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Geometry of cast shadows