<s>
Range	B-Algorithm
imaging	I-Algorithm
is	O
the	O
name	O
for	O
a	O
collection	O
of	O
techniques	O
that	O
are	O
used	O
to	O
produce	O
a	O
2D	O
image	O
showing	O
the	O
distance	O
to	O
points	O
in	O
a	O
scene	O
from	O
a	O
specific	O
point	O
,	O
normally	O
associated	O
with	O
some	O
type	O
of	O
sensor	O
device	O
.	O
</s>
<s>
The	O
resulting	O
range	B-Algorithm
image	I-Algorithm
has	O
pixel	O
values	O
that	O
correspond	O
to	O
the	O
distance	O
.	O
</s>
<s>
If	O
the	O
sensor	O
that	O
is	O
used	O
to	O
produce	O
the	O
range	B-Algorithm
image	I-Algorithm
is	O
properly	O
calibrated	O
the	O
pixel	O
values	O
can	O
be	O
given	O
directly	O
in	O
physical	O
units	O
,	O
such	O
as	O
meters	O
.	O
</s>
<s>
The	O
sensor	O
device	O
that	O
is	O
used	O
for	O
producing	O
the	O
range	B-Algorithm
image	I-Algorithm
is	O
sometimes	O
referred	O
to	O
as	O
a	O
range	B-Algorithm
camera	I-Algorithm
or	O
depth	B-Algorithm
camera	I-Algorithm
.	O
</s>
<s>
Range	B-Algorithm
cameras	I-Algorithm
can	O
operate	O
according	O
to	O
a	O
number	O
of	O
different	O
techniques	O
,	O
some	O
of	O
which	O
are	O
presented	O
here	O
.	O
</s>
<s>
Stereo	B-Algorithm
triangulation	O
is	O
an	O
application	O
of	O
stereophotogrammetry	O
where	O
the	O
depth	O
data	O
of	O
the	O
pixels	O
are	O
determined	O
from	O
data	O
acquired	O
using	O
a	O
stereo	B-Algorithm
or	O
multiple-camera	O
setup	O
system	O
.	O
</s>
<s>
In	O
order	O
to	O
solve	O
the	O
depth	O
measurement	O
problem	O
using	O
a	O
stereo	B-Algorithm
camera	I-Algorithm
system	O
it	O
is	O
necessary	O
to	O
first	O
find	O
corresponding	B-Algorithm
points	I-Algorithm
in	O
the	O
different	O
images	O
.	O
</s>
<s>
Solving	O
the	O
correspondence	B-Algorithm
problem	I-Algorithm
is	O
one	O
of	O
the	O
main	O
problems	O
when	O
using	O
this	O
type	O
of	O
technique	O
.	O
</s>
<s>
For	O
instance	O
,	O
it	O
is	O
difficult	O
to	O
solve	O
the	O
correspondence	B-Algorithm
problem	I-Algorithm
for	O
image	O
points	O
that	O
lie	O
inside	O
regions	O
of	O
homogeneous	O
intensity	O
or	O
color	O
.	O
</s>
<s>
As	O
a	O
consequence	O
,	O
range	B-Algorithm
imaging	I-Algorithm
based	O
on	O
stereo	B-Algorithm
triangulation	O
can	O
usually	O
produce	O
reliable	O
depth	O
estimates	O
only	O
for	O
a	O
subset	O
of	O
all	O
points	O
visible	O
in	O
the	O
multiple	O
cameras	O
.	O
</s>
<s>
The	O
other	O
techniques	O
mentioned	O
here	O
do	O
not	O
have	O
to	O
solve	O
the	O
correspondence	B-Algorithm
problem	I-Algorithm
but	O
are	O
instead	O
dependent	O
on	O
particular	O
scene	O
illumination	O
conditions	O
.	O
</s>
<s>
These	O
can	O
be	O
represented	O
as	O
a	O
2D	O
range	B-Algorithm
image	I-Algorithm
.	O
</s>
<s>
By	O
illuminating	O
the	O
scene	O
with	O
a	O
specially	O
designed	O
light	O
pattern	O
,	O
structured	B-General_Concept
light	I-General_Concept
,	O
depth	O
can	O
be	O
determined	O
using	O
only	O
a	O
single	O
image	O
of	O
the	O
reflected	O
light	O
.	O
</s>
<s>
The	O
structured	B-General_Concept
light	I-General_Concept
can	O
be	O
in	O
the	O
form	O
of	O
horizontal	O
and	O
vertical	O
lines	O
,	O
points	O
or	O
checker	O
board	O
patterns	O
.	O
</s>
<s>
A	O
light	O
stage	O
is	O
basically	O
a	O
generic	O
structured	B-General_Concept
light	I-General_Concept
range	B-Algorithm
imaging	I-Algorithm
device	O
originally	O
created	O
for	O
the	O
job	O
of	O
reflectance	O
capture	O
.	O
</s>
<s>
The	O
depth	O
can	O
also	O
be	O
measured	O
using	O
the	O
standard	O
time-of-flight	O
(	O
ToF	O
)	O
technique	O
,	O
more	O
or	O
less	O
like	O
a	O
radar	B-Application
,	O
in	O
that	O
a	O
range	B-Algorithm
image	I-Algorithm
similar	O
to	O
a	O
radar	B-Application
image	O
is	O
produced	O
,	O
except	O
that	O
a	O
light	O
pulse	O
is	O
used	O
instead	O
of	O
an	O
RF	O
pulse	O
.	O
</s>
<s>
A	O
time-of-flight	O
laser	O
radar	B-Application
with	O
a	O
fast	O
gating	O
intensified	O
CCD	O
camera	O
achieves	O
sub-millimeter	O
depth	O
resolution	O
.	O
</s>
<s>
Under	O
the	O
assumption	O
that	O
the	O
true	O
range	B-Algorithm
image	I-Algorithm
is	O
a	O
more	O
or	O
less	O
continuous	O
function	O
of	O
the	O
image	O
coordinates	O
,	O
the	O
correct	O
depth	O
can	O
be	O
obtained	O
using	O
a	O
technique	O
called	O
phase-unwrapping	O
.	O
</s>
<s>
In	O
order	O
to	O
identify	O
the	O
size	O
of	O
the	O
blur	O
(	O
needed	O
to	O
decode	O
depth	O
information	O
)	O
in	O
the	O
captured	O
image	O
,	O
two	O
approaches	O
can	O
be	O
used	O
:	O
1	O
)	O
deblurring	B-Algorithm
the	O
captured	O
image	O
with	O
different	O
blurs	O
,	O
or	O
2	O
)	O
learning	O
some	O
linear	O
filters	O
that	O
identify	O
the	O
type	O
of	O
blur	O
.	O
</s>
<s>
Using	O
a	O
principal	B-Application
component	I-Application
analysis	I-Application
(	O
PCA	O
)	O
based	O
technique	O
,	O
the	O
method	O
learns	O
off-line	O
a	O
bank	O
of	O
filters	O
that	O
uniquely	O
identify	O
each	O
size	O
of	O
blur	O
;	O
these	O
filters	O
are	O
then	O
applied	O
directly	O
to	O
the	O
captured	O
image	O
,	O
as	O
a	O
normal	O
convolution	O
.	O
</s>
<s>
Since	O
the	O
depth	O
for	O
a	O
point	O
is	O
inferred	O
from	O
its	O
extent	O
of	O
blurring	O
caused	O
by	O
the	O
light	O
spreading	O
from	O
the	O
corresponding	B-Algorithm
point	I-Algorithm
in	O
the	O
scene	O
arriving	O
across	O
the	O
entire	O
surface	O
of	O
the	O
aperture	O
and	O
distorting	O
according	O
to	O
this	O
spread	O
,	O
this	O
is	O
a	O
complex	O
form	O
of	O
stereo	B-Algorithm
triangulation	O
.	O
</s>
<s>
This	O
technology	O
has	O
lately	O
been	O
used	O
in	O
the	O
iPhone	B-Operating_System
X	I-Operating_System
.	O
</s>
<s>
Many	O
other	O
phones	O
from	O
Samsung	B-Application
and	O
computers	O
from	O
Microsoft	O
have	O
tried	O
to	O
use	O
this	O
technology	O
but	O
they	O
do	O
not	O
use	O
the	O
3D	O
mapping	O
.	O
</s>
