We now show that, if 
is the projection matrix which
rectifies one of the two views, the linear transformation (in projective
coordinates) that maps the retinal plane of 
onto the rectified retinal plane is given by
the matrix 
.
For any 3-D point w
we can write
We know that the equation of the optical ray
associated to 
is
hence
Assuming that rectification does not alter the optical center ( 
), we obtain
This is a clearer and more compact result than the one reported in
[1], in which 
is not written as the inverse of a
projection matrix.