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Since parallel stereo configurations greatly simplify
the matching process of two images, if a pair of images
is taken with a general stereo configuration,
an operation known as rectification can be applied
to bring the two retinal planes to be coplanar to
a common plane
in space. This plane
can be chosen as follows (Fig. 11):
Figure 11:
Image rectification (after Faugeras).
![\begin{figure}
\begin{center}
\
\psfig {figure=rectification.xfigps,height=7cm}
\end{center}\end{figure}](img39.gif) |
- compute
, the line of intersection between the
original retinal planes
and
. - compute the baseline vector CC'.
- compute the equation of the plane that
contains
and parallel
to CC'.
- assign this computed plane to
.
An alternative way of choosing
is:
instead of step 3 above, look for a plane that
contains CC' and that minimizes the projective
distortion.
Fig. 12 shows an image triplet before
and after applying image rectification.
After rectification,
the epipolar lines between images 1 and 2
coincide with the horizontal scanlines,
the epipolar lines between images 1 and 3
coincide with the vertical scanlines.
Figure 12:
Image triplets of a room scene before
and after rectification (after Ayache and Hansen)
![\begin{figure}
\begin{center}
\
\begin{minipage}
{7cm}
(a) before rectification ...
...
\psfig {figure=rect-after.ps,width=7cm}
\end{minipage}\end{center}\end{figure}](img41.gif) |
Next: Computing the epipolar lines
Up: Computer Vision IT412
Previous: References
Robyn Owens
10/29/1997