The Weizmann Institute of Science
Faculty of Mathematics and Computer Science
Vision and Robotics Seminar
Amit Gruber
School of Computer Science and Engineering
The Hebrew University of Jerusalem
will speak on
Factorization with uncertainty and missing data:
exploiting temporal coherence
Abstract:
This is a joint work with Yair WeissThis is a joint work with Yair WeissThis is
a joint work with Yair WeissThe problem of ``Structure From Motion" is a
central problem in vision: given the 2D locations of certain points we wish to
recover the camera motion and the 3D coordinates of the points. Under
simplified camera models, the problem reduces to factorizing a measurement
matrix into the product of two low rank matrices. Each element of the
measurement matrix contains the position of a point in a particular image. When
all elements are observed, the problem can be solved trivially using SVD, but
in any realistic situation many elements of the matrix are missing and the ones
that are observed have a different directional uncertainty. Under these
conditions, most existing factorization algorithms fail while human perception
is relatively unchanged.
In this work we use the well known EM algorithm for factor analysis to perform
factorization. This allows us to easily handle missing data and measurement
uncertainty and more importantly allows us to place a prior on the temporal
trajectory of the latent variables (the camera position). We show that
incorporating this prior gives a significant improvement in performance in
challenging image sequences.
This is a joint work with Yair Weiss.
The lecture will take place in the
Lecture Hall, Room 1, Ziskind Building
on Thursday, December 4, 2003
at noon