lec3 prelim

# lec3 prelim - Lecture 3 Course Enrollment Those on waiting...

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USC CS574: Computer Vision, Fall 2010 Copyright 2010, by R. Nevatia 1 Lecture 3: Aug 30, 10 • Course Enrollment – Those on waiting list will be admitted as slots open • Must continue to attend class, must hand in assignments • Lecture slides posted in two formats (single page, 4 pp) – Preliminary slides posted ahead of class • Last Class – Image formation: equations for projection of a point – Homogeneous coordinates – Intrinsic camera parameters • Today’s objective – Intrinsic and Extrinsic parameters – Affine Cameras – Camera Calibration

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USC CS574: Computer Vision, Fall 2010 Copyright 2010, by R. Nevatia 2 Homogeneous Coordinates • Add an extra coordinate –( x,y,z ) => ( x h , y h , z h , w h ) = ( wx, wy, wz, w ), w is any constant (in the book, w is set to 1) • Advantage: allows perspective transformation to be linearized , i.e. expressed as a matrix equation x h f’ 0 0 0 x h y h = 0 f’ 0 0 y h w h 0 0 1 0 z h w h x h = f x h , y h = f y h , w h = z h x = x h / w h = f *x/z, y = f * y/z NOTE: If image plane in front, replace f by –f in the above equations.
USC CS574: Computer Vision, Fall 2010 Copyright 2010, by R. Nevatia 3 Rigid Transformations • Translation • Rotation • Combine rotation and translation • Note: t = B O A , from object to camera coordinates, it may be more convenient to be given A O B in which case t = -R A O B

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USC CS574: Computer Vision, Fall 2010 Copyright 2010, by R. Nevatia 4 Intrinsic Camera Parameters Figure 2.8 • Measurement in image coordinate system may be in “pixel” units (u,v), pixels may not be rectangular, origin of image coordinate system may not be at the center of image (projection of lens center), axis may be skewed . Normalized image plane is unit distance in front .
USC CS574: Computer Vision, Fall 2010 Copyright 2010, by R. Nevatia 5 Intrinsic Camera Equations • All intrinsic parameters combined • Projection equation – Note that division by z is present because p = (u, v, 1) T ; if we allow p = (u', v', w') T ; we can just write p = M P , leaving the step of division to be

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## This note was uploaded on 11/23/2010 for the course CS 574 taught by Professor Ramnevatia during the Fall '10 term at USC.

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lec3 prelim - Lecture 3 Course Enrollment Those on waiting...

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