Front-end computations in human vision Jitendra Malik U.C. Berkeley References: DeValois & DeValois,Hubel, Palmer, Spillman &Werner, Wandell Jitendra Malik.

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Presentation transcript:

Front-end computations in human vision Jitendra Malik U.C. Berkeley References: DeValois & DeValois,Hubel, Palmer, Spillman &Werner, Wandell Jitendra Malik U.C. Berkeley References: DeValois & DeValois,Hubel, Palmer, Spillman &Werner, Wandell

Cerebral Cortex

Monocular Visual Field: 160 deg (w) X 135 deg (h) Binocular Visual Field: 200 deg (w) X 135 deg (h)

Cones and Rods

ON and OFF cells in retinal ganglia

Modeling simple cells Elongated directional Gaussian derivatives 2nd derivative and Hilbert transform L 1 normalized for scale invariance 6 orientations, 3 scales Zero mean Elongated directional Gaussian derivatives 2nd derivative and Hilbert transform L 1 normalized for scale invariance 6 orientations, 3 scales Zero mean

Orientation 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 scales

Visual Processing Areas

Macaque Visual Areas

Textons (Malik et al, IJCV 2001) K-means on vectors of filter responses

Textons (cont.)

Texton Histograms i j k Chi square test:

CSF as function of eccentricity

Receptor density vs eccentricity

Cortical Magnification Factor

Mapping from Retina to V1