<s>
These	O
relations	O
are	O
derived	O
based	O
on	O
the	O
assumption	O
that	O
the	O
cameras	O
can	O
be	O
approximated	O
by	O
the	O
pinhole	B-Algorithm
camera	I-Algorithm
model	I-Algorithm
.	O
</s>
<s>
This	O
conversion	O
from	O
3D	O
to	O
2D	O
is	O
referred	O
to	O
as	O
a	O
perspective	B-Architecture
projection	I-Architecture
and	O
is	O
described	O
by	O
the	O
pinhole	B-Algorithm
camera	I-Algorithm
model	I-Algorithm
.	O
</s>
<s>
These	O
two	O
image	O
points	O
,	O
denoted	O
by	O
eL	O
and	O
eR	O
,	O
are	O
called	O
epipoles	O
or	O
epipolar	B-General_Concept
points	I-General_Concept
.	O
</s>
<s>
All	O
epipolar	O
lines	O
in	O
one	O
image	O
contain	O
the	O
epipolar	B-General_Concept
point	I-General_Concept
of	O
that	O
image	O
.	O
</s>
<s>
In	O
fact	O
,	O
any	O
line	O
which	O
contains	O
the	O
epipolar	B-General_Concept
point	I-General_Concept
is	O
an	O
epipolar	O
line	O
since	O
it	O
can	O
be	O
derived	O
from	O
some	O
3D	O
point	O
X	O
.	O
</s>
<s>
It	O
means	O
that	O
it	O
is	O
possible	O
to	O
test	O
if	O
two	O
points	O
correspond	B-Algorithm
to	O
the	O
same	O
3D	O
point	O
.	O
</s>
<s>
Epipolar	O
constraints	O
can	O
also	O
be	O
described	O
by	O
the	O
essential	B-General_Concept
matrix	I-General_Concept
or	O
the	O
fundamental	B-General_Concept
matrix	I-General_Concept
between	O
the	O
two	O
cameras	O
.	O
</s>
<s>
If	O
the	O
two	O
image	O
points	O
correspond	B-Algorithm
to	O
the	O
same	O
3D	O
point	O
X	O
the	O
projection	O
lines	O
must	O
intersect	O
precisely	O
at	O
X	O
.	O
</s>
<s>
This	O
means	O
that	O
X	O
can	O
be	O
calculated	O
from	O
the	O
coordinates	O
of	O
the	O
two	O
image	O
points	O
,	O
a	O
process	O
called	O
triangulation	B-Algorithm
.	O
</s>
<s>
This	O
means	O
that	O
for	O
each	O
point	O
in	O
one	O
image	O
,	O
its	O
corresponding	B-Algorithm
point	I-Algorithm
in	O
the	O
other	O
image	O
can	O
be	O
found	O
by	O
looking	O
only	O
along	O
a	O
horizontal	O
line	O
.	O
</s>
<s>
This	O
process	O
is	O
called	O
image	B-Algorithm
rectification	I-Algorithm
.	O
</s>
<s>
Epipolar	O
geometry	O
of	O
this	O
sensor	O
is	O
quite	O
different	O
from	O
that	O
of	O
pinhole	B-Algorithm
projection	I-Algorithm
cameras	O
.	O
</s>
