Front-end computations in human visionSlide 2Cerebral CortexSlide 4Slide 5Slide 6Monocular Visual Field: 160 deg (w) X 135 deg (h) Binocular Visual Field: 200 deg (w) X 135 deg (h)Slide 8Slide 9Cones and RodsSlide 11Slide 12Slide 13Slide 14Slide 15ON and OFF cells in retinal gangliaSlide 17Slide 18Slide 19Modeling simple cellsSlide 21Orientation EnergySlide 23Slide 24Slide 25Visual Processing AreasMacaque Visual AreasSlide 28Slide 29Textons (Malik et al, IJCV 2001)Slide 31Texton HistogramsCSF as function of eccentricityReceptor density vs eccentricityCortical Magnification FactorMapping from Retina to V1Front-end computations in human vision Front-end computations in human vision Jitendra MalikU.C. BerkeleyReferences: DeValois & DeValois,Hubel, Palmer, Spillman &Werner, WandellJitendra MalikU.C. BerkeleyReferences: DeValois & DeValois,Hubel, Palmer, Spillman &Werner, WandellCerebral CortexCerebral CortexMonocular Visual Field: 160 deg (w) X 135 deg (h)Binocular Visual Field: 200 deg (w) X 135 deg (h)Monocular Visual Field: 160 deg (w) X 135 deg (h)Binocular Visual Field: 200 deg (w) X 135 deg (h)Cones and RodsCones and RodsON and OFF cells in retinal gangliaON and OFF cells in retinal gangliaModeling simple cellsModeling simple cells•Elongated directional Gaussian derivatives•2nd derivative and Hilbert transform•L1 normalized for scale invariance•6 orientations, 3 scales•Zero mean•Elongated directional Gaussian derivatives•2nd derivative and Hilbert transform•L1 normalized for scale invariance•6 orientations, 3 scales•Zero meanOrientation EnergyOrientation Energy•Gaussian 2nd derivative and its Hilbert pair • •Can detect combination of bar and edge features; also insensitive to linear shading [Perona&Malik 90]•Multiple scales22)()(evenoddfIfIOE Visual Processing AreasVisual Processing AreasMacaque Visual AreasMacaque Visual AreasTextons (Malik et al, IJCV 2001)Textons (Malik et al, IJCV 2001)•K-means on vectors of filter responses•K-means on vectors of filter responsesTextons (cont.)Textons (cont.)Texton HistogramsTexton HistogramsijkKmjijijimhmhmhmhhh122)()()]()([21),(Chi square test:0.10.8CSF as function of eccentricityCSF as function of eccentricityReceptor density vs eccentricityReceptor density vs eccentricityCortical Magnification FactorCortical Magnification FactorMapping from Retina to V1Mapping from Retina to
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