<s>
Stereoscopy	B-Algorithm
(	O
also	O
called	O
stereoscopics	B-Algorithm
,	O
or	O
stereo	O
imaging	O
)	O
is	O
a	O
technique	O
for	O
creating	O
or	O
enhancing	O
the	O
illusion	O
of	O
depth	O
in	O
an	O
image	O
by	O
means	O
of	O
stereopsis	B-Algorithm
for	O
binocular	B-Algorithm
vision	I-Algorithm
.	O
</s>
<s>
The	O
word	O
stereoscopy	B-Algorithm
derives	O
.	O
</s>
<s>
Any	O
stereoscopic	B-Algorithm
image	I-Algorithm
is	O
called	O
a	O
stereogram	O
.	O
</s>
<s>
Originally	O
,	O
stereogram	O
referred	O
to	O
a	O
pair	O
of	O
stereo	O
images	O
which	O
could	O
be	O
viewed	O
using	O
a	O
stereoscope	B-Algorithm
.	O
</s>
<s>
Most	O
stereoscopic	B-Algorithm
methods	O
present	O
a	O
pair	O
of	O
two-dimensional	O
images	O
to	O
the	O
viewer	O
.	O
</s>
<s>
However	O
,	O
the	O
3D	O
effect	O
lacks	O
proper	O
focal	O
depth	O
,	O
which	O
gives	O
rise	O
to	O
the	O
Vergence-Accommodation	O
Conflict	O
.	O
</s>
<s>
Stereoscopy	B-Algorithm
is	O
distinguished	O
from	O
other	O
types	O
of	O
3D	B-Algorithm
displays	I-Algorithm
that	O
display	B-Device
an	O
image	O
in	O
three	O
full	O
dimensions	O
,	O
allowing	O
the	O
observer	O
to	O
increase	O
information	O
about	O
the	O
3-dimensional	O
objects	O
being	O
displayed	O
by	O
head	O
and	O
eye	O
movements	O
.	O
</s>
<s>
Stereoscopy	B-Algorithm
creates	O
the	O
illusion	O
of	O
three-dimensional	O
depth	O
from	O
a	O
pair	O
of	O
two-dimensional	O
images	O
.	O
</s>
<s>
Stereoscopy	B-Algorithm
is	O
the	O
production	O
of	O
the	O
illusion	O
of	O
depth	O
in	O
a	O
photograph	O
,	O
movie	O
,	O
or	O
other	O
two-dimensional	O
image	O
by	O
the	O
presentation	O
of	O
a	O
slightly	O
different	O
image	O
to	O
each	O
eye	O
,	O
which	O
adds	O
the	O
first	O
of	O
these	O
cues	O
(	O
stereopsis	B-Algorithm
)	O
.	O
</s>
<s>
Because	O
all	O
points	O
in	O
the	O
image	O
produced	O
by	O
stereoscopy	B-Algorithm
focus	O
at	O
the	O
same	O
plane	O
regardless	O
of	O
their	O
depth	O
in	O
the	O
original	O
scene	O
,	O
the	O
second	O
cue	O
,	O
focus	O
,	O
is	O
not	O
duplicated	O
and	O
therefore	O
the	O
illusion	O
of	O
depth	O
is	O
incomplete	O
.	O
</s>
<s>
There	O
are	O
also	O
mainly	O
two	O
effects	O
of	O
stereoscopy	B-Algorithm
that	O
are	O
unnatural	O
for	O
human	O
vision	O
:	O
(	O
1	O
)	O
the	O
mismatch	O
between	O
convergence	O
and	O
accommodation	O
,	O
caused	O
by	O
the	O
difference	O
between	O
an	O
object	O
's	O
perceived	O
position	O
in	O
front	O
of	O
or	O
behind	O
the	O
display	B-Device
or	O
screen	O
and	O
the	O
real	O
origin	O
of	O
that	O
light	O
;	O
and	O
(	O
2	O
)	O
possible	O
crosstalk	O
between	O
the	O
eyes	O
,	O
caused	O
by	O
imperfect	O
image	O
separation	O
in	O
some	O
methods	O
of	O
stereoscopy	B-Algorithm
.	O
</s>
<s>
Holographic	B-Algorithm
displays	I-Algorithm
and	O
volumetric	B-Algorithm
display	I-Algorithm
do	O
not	O
have	O
this	O
limitation	O
.	O
</s>
<s>
The	O
accurate	O
term	O
"	O
stereoscopic	B-Algorithm
"	O
is	O
more	O
cumbersome	O
than	O
the	O
common	O
misnomer	O
"	O
3D	O
"	O
,	O
which	O
has	O
been	O
entrenched	O
by	O
many	O
decades	O
of	O
unquestioned	O
misuse	O
.	O
</s>
<s>
Although	O
most	O
stereoscopic	B-Algorithm
displays	I-Algorithm
do	O
not	O
qualify	O
as	O
real	O
3D	B-Algorithm
display	I-Algorithm
,	O
all	O
real	O
3D	B-Algorithm
displays	I-Algorithm
are	O
also	O
stereoscopic	B-Algorithm
displays	I-Algorithm
because	O
they	O
meet	O
the	O
lower	O
criteria	O
also	O
.	O
</s>
<s>
Most	O
3D	B-Algorithm
displays	I-Algorithm
use	O
this	O
stereoscopic	B-Algorithm
method	O
to	O
convey	O
images	O
.	O
</s>
<s>
Wheatstone	O
originally	O
used	O
his	O
stereoscope	B-Algorithm
(	O
a	O
rather	O
bulky	O
device	O
)	O
with	O
drawings	O
because	O
photography	O
was	O
not	O
yet	O
available	O
,	O
yet	O
his	O
original	O
paper	O
seems	O
to	O
foresee	O
the	O
development	O
of	O
a	O
realistic	O
imaging	O
method	O
:	O
</s>
<s>
Stereoscopy	B-Algorithm
is	O
used	O
in	O
photogrammetry	B-Application
and	O
also	O
for	O
entertainment	O
through	O
the	O
production	O
of	O
stereograms	B-Algorithm
.	O
</s>
<s>
Stereoscopy	B-Algorithm
is	O
useful	O
in	O
viewing	O
images	O
rendered	O
from	O
large	O
multi-dimensional	O
data	O
sets	O
such	O
as	O
are	O
produced	O
by	O
experimental	O
data	O
.	O
</s>
<s>
Modern	O
industrial	O
three-dimensional	O
photography	O
may	O
use	O
3D	B-Algorithm
scanners	I-Algorithm
to	O
detect	O
and	O
record	O
three-dimensional	O
information	O
.	O
</s>
<s>
The	O
three-dimensional	O
depth	O
information	O
can	O
be	O
reconstructed	B-Algorithm
from	O
two	O
images	O
using	O
a	O
computer	O
by	O
correlating	O
the	O
pixels	B-Algorithm
in	O
the	O
left	O
and	O
right	O
images	O
.	O
</s>
<s>
Solving	O
the	O
Correspondence	B-Algorithm
problem	I-Algorithm
in	O
the	O
field	O
of	O
Computer	B-Application
Vision	I-Application
aims	O
to	O
create	O
meaningful	O
depth	O
information	O
from	O
two	O
images	O
.	O
</s>
<s>
Anatomically	O
,	O
there	O
are	O
3	O
levels	O
of	O
binocular	B-Algorithm
vision	I-Algorithm
required	O
to	O
view	O
stereo	O
images	O
:	O
</s>
<s>
Some	O
people	O
who	O
have	O
strabismus	O
disrupt	O
the	O
development	O
of	O
stereopsis	B-Algorithm
,	O
however	O
orthoptics	O
treatment	O
can	O
be	O
used	O
to	O
improve	O
binocular	B-Algorithm
vision	I-Algorithm
.	O
</s>
<s>
It	O
is	O
believed	O
that	O
approximately	O
12%	O
of	O
people	O
are	O
unable	O
to	O
properly	O
see	O
3D	B-Algorithm
images	I-Algorithm
,	O
due	O
to	O
a	O
variety	O
of	O
medical	O
conditions	O
.	O
</s>
<s>
According	O
to	O
another	O
experiment	O
up	O
to	O
30%	O
of	O
people	O
have	O
very	O
weak	O
stereoscopic	B-Algorithm
vision	I-Algorithm
preventing	O
them	O
from	O
depth	O
perception	O
based	O
on	O
stereo	O
disparity	O
.	O
</s>
<s>
Stereoscopic	B-Algorithm
viewing	O
may	O
be	O
artificially	O
created	O
by	O
the	O
viewer	O
's	O
brain	O
,	O
as	O
demonstrated	O
with	O
the	O
Van	B-Algorithm
Hare	I-Algorithm
Effect	I-Algorithm
,	O
where	O
the	O
brain	O
perceives	O
stereo	O
images	O
even	O
when	O
the	O
paired	O
photographs	O
are	O
identical	O
.	O
</s>
<s>
Traditional	O
stereoscopic	B-Algorithm
photography	I-Algorithm
consists	O
of	O
creating	O
a	O
3D	O
illusion	O
starting	O
from	O
a	O
pair	O
of	O
2D	O
images	O
,	O
a	O
stereogram	O
.	O
</s>
<s>
The	O
easiest	O
way	O
to	O
enhance	O
depth	O
perception	O
in	O
the	O
brain	O
is	O
to	O
provide	O
the	O
eyes	O
of	O
the	O
viewer	O
with	O
two	O
different	O
images	O
,	O
representing	O
two	O
perspectives	B-Architecture
of	O
the	O
same	O
object	O
,	O
with	O
a	O
minor	O
deviation	O
equal	O
or	O
nearly	O
equal	O
to	O
the	O
perspectives	B-Architecture
that	O
both	O
eyes	O
naturally	O
receive	O
in	O
binocular	B-Algorithm
vision	I-Algorithm
.	O
</s>
<s>
The	O
principal	O
disadvantage	O
of	O
side-by-side	O
viewers	O
is	O
that	O
large	O
image	O
displays	O
are	O
not	O
practical	O
and	O
resolution	O
is	O
limited	O
by	O
the	O
lesser	O
of	O
the	O
display	B-Device
medium	O
or	O
human	O
eye	O
.	O
</s>
<s>
One	O
approach	O
to	O
decoupling	O
the	O
two	O
functions	O
is	O
to	O
view	O
the	O
image	O
pair	O
extremely	O
close	O
up	O
with	O
completely	O
relaxed	O
eyes	O
,	O
making	O
no	O
attempt	O
to	O
focus	O
clearly	O
but	O
simply	O
achieving	O
comfortable	O
stereoscopic	B-Algorithm
fusion	O
of	O
the	O
two	O
blurry	O
images	O
by	O
the	O
"	O
look-through	O
"	O
approach	O
,	O
and	O
only	O
then	O
exerting	O
the	O
effort	O
to	O
focus	O
them	O
more	O
clearly	O
,	O
increasing	O
the	O
viewing	O
distance	O
as	O
necessary	O
.	O
</s>
<s>
Regardless	O
of	O
the	O
approach	O
used	O
or	O
the	O
image	O
medium	O
,	O
for	O
comfortable	O
viewing	O
and	O
stereoscopic	B-Algorithm
accuracy	O
the	O
size	O
and	O
spacing	O
of	O
the	O
images	O
should	O
be	O
such	O
that	O
the	O
corresponding	B-Algorithm
points	I-Algorithm
of	O
very	O
distant	O
objects	O
in	O
the	O
scene	O
are	O
separated	O
by	O
the	O
same	O
distance	O
as	O
the	O
viewer	O
's	O
eyes	O
,	O
but	O
not	O
more	O
;	O
the	O
average	O
interocular	O
distance	O
is	O
about	O
63mm	O
.	O
</s>
<s>
Prismatic	B-Application
,	O
self-masking	O
glasses	O
are	O
now	O
being	O
used	O
by	O
some	O
cross-eyed-view	O
advocates	O
.	O
</s>
<s>
However	O
,	O
any	O
viewing	O
aid	O
that	O
uses	O
prisms	O
,	O
mirrors	O
or	O
lenses	O
to	O
assist	O
fusion	O
or	O
focus	O
is	O
simply	O
a	O
type	O
of	O
stereoscope	B-Algorithm
,	O
excluded	O
by	O
the	O
customary	O
definition	O
of	O
freeviewing	O
.	O
</s>
<s>
Stereoscopically	B-Algorithm
fusing	O
two	O
separate	O
images	O
without	O
the	O
aid	O
of	O
mirrors	O
or	O
prisms	O
while	O
simultaneously	O
keeping	O
them	O
in	O
sharp	O
focus	O
without	O
the	O
aid	O
of	O
suitable	O
viewing	O
lenses	O
inevitably	O
requires	O
an	O
unnatural	O
combination	O
of	O
eye	O
vergence	B-Algorithm
and	O
accommodation	O
.	O
</s>
<s>
An	O
autostereogram	B-Algorithm
is	O
a	O
single-image	B-Algorithm
stereogram	I-Algorithm
(	O
SIS	O
)	O
,	O
designed	O
to	O
create	O
the	O
visual	O
illusion	O
of	O
a	O
three-dimensional	O
(	O
3D	O
)	O
scene	O
within	O
the	O
human	O
brain	O
from	O
an	O
external	O
two-dimensional	O
image	O
.	O
</s>
<s>
In	O
order	O
to	O
perceive	O
3D	O
shapes	O
in	O
these	O
autostereograms	B-Algorithm
,	O
one	O
must	O
overcome	O
the	O
normally	O
automatic	O
coordination	O
between	O
focusing	O
and	O
vergence	B-Algorithm
.	O
</s>
<s>
The	O
stereoscope	B-Algorithm
is	O
essentially	O
an	O
instrument	O
in	O
which	O
two	O
photographs	O
of	O
the	O
same	O
object	O
,	O
taken	O
from	O
slightly	O
different	O
angles	O
,	O
are	O
simultaneously	O
presented	O
,	O
one	O
to	O
each	O
eye	O
.	O
</s>
<s>
A	O
simple	O
stereoscope	B-Algorithm
is	O
limited	O
in	O
the	O
size	O
of	O
the	O
image	O
that	O
may	O
be	O
used	O
.	O
</s>
<s>
A	O
more	O
complex	O
stereoscope	B-Algorithm
uses	O
a	O
pair	O
of	O
horizontal	O
periscope-like	O
devices	O
,	O
allowing	O
the	O
use	O
of	O
larger	O
images	O
that	O
can	O
present	O
more	O
detailed	O
information	O
in	O
a	O
wider	O
field	O
of	O
view	O
.	O
</s>
<s>
One	O
can	O
buy	O
historical	O
stereoscopes	B-Algorithm
such	O
as	O
Holmes	O
stereoscopes	B-Algorithm
as	O
antiques	O
.	O
</s>
<s>
Some	O
stereoscopes	B-Algorithm
are	O
designed	O
for	O
viewing	O
transparent	O
photographs	O
on	O
film	O
or	O
glass	O
,	O
known	O
as	O
transparencies	O
or	O
diapositives	O
and	O
commonly	O
called	O
slides	O
.	O
</s>
<s>
Some	O
of	O
the	O
earliest	O
stereoscope	B-Algorithm
views	O
,	O
issued	O
in	O
the	O
1850s	O
,	O
were	O
on	O
glass	O
.	O
</s>
<s>
In	O
the	O
early	O
20th	O
century	O
,	O
45x107mm	O
and	O
6x13cm	O
glass	O
slides	O
were	O
common	O
formats	O
for	O
amateur	O
stereo	B-Algorithm
photography	I-Algorithm
,	O
especially	O
in	O
Europe	O
.	O
</s>
<s>
For	O
amateur	O
stereo	O
slides	O
,	O
the	O
Stereo	B-Algorithm
Realist	I-Algorithm
format	O
,	O
introduced	O
in	O
1947	O
,	O
is	O
by	O
far	O
the	O
most	O
common	O
.	O
</s>
<s>
The	O
user	O
typically	O
wears	O
a	O
helmet	O
or	O
glasses	O
with	O
two	O
small	O
LCD	B-Device
or	O
OLED	B-Device
displays	I-Device
with	O
magnifying	O
lenses	O
,	O
one	O
for	O
each	O
eye	O
.	O
</s>
<s>
The	O
technology	O
can	O
be	O
used	O
to	O
show	O
stereo	B-Algorithm
films	I-Algorithm
,	O
images	O
or	O
games	O
,	O
but	O
it	O
can	O
also	O
be	O
used	O
to	O
create	O
a	O
virtual	O
display	B-Device
.	O
</s>
<s>
Head-mounted	B-General_Concept
displays	I-General_Concept
may	O
also	O
be	O
coupled	O
with	O
head-tracking	O
devices	O
,	O
allowing	O
the	O
user	O
to	O
"	O
look	O
around	O
"	O
the	O
virtual	O
world	O
by	O
moving	O
their	O
head	O
,	O
eliminating	O
the	O
need	O
for	O
a	O
separate	O
controller	O
.	O
</s>
<s>
Head-mounted	O
or	O
wearable	O
glasses	O
may	O
be	O
used	O
to	O
view	O
a	O
see-through	O
image	O
imposed	O
upon	O
the	O
real	O
world	O
view	O
,	O
creating	O
what	O
is	O
called	O
augmented	B-General_Concept
reality	I-General_Concept
.	O
</s>
<s>
Augmented	O
stereoscopic	B-Algorithm
vision	I-Algorithm
is	O
also	O
expected	O
to	O
have	O
applications	O
in	O
surgery	O
,	O
as	O
it	O
allows	O
the	O
combination	O
of	O
radiographic	O
data	O
(	O
CAT	O
scans	O
and	O
MRI	B-Algorithm
imaging	O
)	O
with	O
the	O
surgeon	O
's	O
vision	O
.	O
</s>
<s>
A	O
virtual	O
retinal	O
display	B-Device
(	O
VRD	O
)	O
,	O
also	O
known	O
as	O
a	O
retinal	O
scan	O
display	B-Device
(	O
RSD	O
)	O
or	O
retinal	O
projector	O
(	O
RP	O
)	O
,	O
not	O
to	O
be	O
confused	O
with	O
a	O
"	O
Retina	B-Operating_System
Display	I-Operating_System
"	O
,	O
is	O
a	O
display	B-Device
technology	I-Device
that	O
draws	O
a	O
raster	B-Algorithm
image	I-Algorithm
(	O
like	O
a	O
television	O
picture	O
)	O
directly	O
onto	O
the	O
retina	O
of	O
the	O
eye	O
.	O
</s>
<s>
The	O
user	O
sees	O
what	O
appears	O
to	O
be	O
a	O
conventional	O
display	B-Device
floating	O
in	O
space	O
in	O
front	O
of	O
them	O
.	O
</s>
<s>
For	O
true	O
stereoscopy	B-Algorithm
,	O
each	O
eye	O
must	O
be	O
provided	O
with	O
its	O
own	O
discrete	O
display	B-Device
.	O
</s>
<s>
To	O
produce	O
a	O
virtual	O
display	B-Device
that	O
occupies	O
a	O
usefully	O
large	O
visual	O
angle	O
but	O
does	O
not	O
involve	O
the	O
use	O
of	O
relatively	O
large	O
lenses	O
or	O
mirrors	O
,	O
the	O
light	O
source	O
must	O
be	O
very	O
close	O
to	O
the	O
eye	O
.	O
</s>
<s>
Active	O
viewers	O
have	O
electronics	O
which	O
interact	O
with	O
a	O
display	B-Device
.	O
</s>
<s>
A	O
shutter	O
system	O
works	O
by	O
openly	O
presenting	O
the	O
image	O
intended	O
for	O
the	O
left	O
eye	O
while	O
blocking	O
the	O
right	O
eye	O
's	O
view	O
,	O
then	O
presenting	O
the	O
right-eye	O
image	O
while	O
blocking	O
the	O
left	O
eye	O
,	O
and	O
repeating	O
this	O
so	O
rapidly	O
that	O
the	O
interruptions	O
do	O
not	O
interfere	O
with	O
the	O
perceived	O
fusion	O
of	O
the	O
two	O
images	O
into	O
a	O
single	O
3D	B-Algorithm
image	I-Algorithm
.	O
</s>
<s>
It	O
generally	O
uses	O
liquid	B-Device
crystal	I-Device
shutter	O
glasses	O
.	O
</s>
<s>
Each	O
eye	O
's	O
glass	O
contains	O
a	O
liquid	B-Device
crystal	I-Device
layer	O
which	O
has	O
the	O
property	O
of	O
becoming	O
dark	O
when	O
voltage	O
is	O
applied	O
,	O
being	O
otherwise	O
transparent	O
.	O
</s>
<s>
The	O
main	O
drawback	O
of	O
active	O
shutters	O
is	O
that	O
most	O
3D	B-Algorithm
videos	I-Algorithm
and	O
movies	O
were	O
shot	O
with	O
simultaneous	O
left	O
and	O
right	O
views	O
,	O
so	O
that	O
it	O
introduces	O
a	O
"	O
time	O
parallax	B-Device
"	O
for	O
anything	O
side-moving	O
:	O
for	O
instance	O
,	O
someone	O
walking	O
at	O
3.4mph	O
will	O
be	O
seen	O
20%	O
too	O
close	O
or	O
25%	O
too	O
remote	O
in	O
the	O
most	O
current	O
case	O
of	O
a	O
2x60	O
Hz	O
projection	O
.	O
</s>
<s>
To	O
present	O
stereoscopic	B-Algorithm
pictures	I-Algorithm
,	O
two	O
images	O
are	O
projected	O
superimposed	O
onto	O
the	O
same	O
screen	O
through	O
polarizing	O
filters	O
or	O
presented	O
on	O
a	O
display	B-Device
with	O
polarized	O
filters	O
.	O
</s>
<s>
On	O
most	O
passive	O
displays	O
every	O
other	O
row	O
of	O
pixels	B-Algorithm
is	O
polarized	O
for	O
one	O
eye	O
or	O
the	O
other	O
.	O
</s>
<s>
Eyeglasses	O
which	O
filter	O
out	O
the	O
very	O
specific	O
wavelengths	O
allow	O
the	O
wearer	O
to	O
see	O
a	O
full	O
color	O
3D	B-Algorithm
image	I-Algorithm
.	O
</s>
<s>
It	O
is	O
also	O
known	O
as	O
spectral	O
comb	O
filtering	O
or	O
wavelength	O
multiplex	O
visualization	O
or	O
super-anaglyph	O
.	O
</s>
<s>
Dolby	B-Algorithm
3D	I-Algorithm
uses	O
this	O
principle	O
.	O
</s>
<s>
Anaglyph	B-Algorithm
3D	I-Algorithm
is	O
the	O
name	O
given	O
to	O
the	O
stereoscopic	B-Algorithm
3D	I-Algorithm
effect	O
achieved	O
by	O
means	O
of	O
encoding	O
each	O
eye	O
's	O
image	O
using	O
filters	O
of	O
different	O
(	O
usually	O
chromatically	O
opposite	O
)	O
colors	O
,	O
typically	O
red	O
and	O
cyan	O
.	O
</s>
<s>
Anaglyph	B-Algorithm
3D	I-Algorithm
images	O
contain	O
two	O
differently	O
filtered	O
colored	O
images	O
,	O
one	O
for	O
each	O
eye	O
.	O
</s>
<s>
When	O
viewed	O
through	O
the	O
"	O
color-coded	O
"	O
"	O
anaglyph	B-Algorithm
glasses	I-Algorithm
"	O
,	O
each	O
of	O
the	O
two	O
images	O
reaches	O
one	O
eye	O
,	O
revealing	O
an	O
integrated	O
stereoscopic	B-Algorithm
image	I-Algorithm
.	O
</s>
<s>
The	O
advantage	O
of	O
this	O
technology	O
consists	O
above	O
all	O
of	O
the	O
fact	O
that	O
one	O
can	O
regard	O
ChromaDepth	O
pictures	O
also	O
without	O
eyeglasses	O
(	O
thus	O
two-dimensional	O
)	O
problem-free	O
(	O
unlike	O
with	O
two-color	O
anaglyph	B-Algorithm
)	O
.	O
</s>
<s>
Because	O
the	O
Pulfrich	O
effect	O
depends	O
on	O
motion	O
in	O
a	O
particular	O
direction	O
to	O
instigate	O
the	O
illusion	O
of	O
depth	O
,	O
it	O
is	O
not	O
useful	O
as	O
a	O
general	O
stereoscopic	B-Algorithm
technique	O
.	O
</s>
<s>
Stereoscopic	B-Algorithm
viewing	O
is	O
achieved	O
by	O
placing	O
an	O
image	O
pair	O
one	O
above	O
one	O
another	O
.	O
</s>
<s>
Another	O
with	O
prismatic	B-Application
glasses	O
is	O
the	O
KMQ	B-Algorithm
viewer	I-Algorithm
.	O
</s>
<s>
Autostereoscopic	B-Algorithm
display	I-Algorithm
technologies	O
use	O
optical	O
components	O
in	O
the	O
display	B-Device
,	O
rather	O
than	O
worn	O
by	O
the	O
user	O
,	O
to	O
enable	O
each	O
eye	O
to	O
see	O
a	O
different	O
image	O
.	O
</s>
<s>
Because	O
headgear	O
is	O
not	O
required	O
,	O
it	O
is	O
also	O
called	O
"	O
glasses-free	B-Algorithm
3D	I-Algorithm
"	O
.	O
</s>
<s>
The	O
optics	O
split	O
the	O
images	O
directionally	O
into	O
the	O
viewer	O
's	O
eyes	O
,	O
so	O
the	O
display	B-Device
viewing	O
geometry	O
requires	O
limited	O
head	O
positions	O
that	O
will	O
achieve	O
the	O
stereoscopic	B-Algorithm
effect	O
.	O
</s>
<s>
Automultiscopic	B-General_Concept
displays	O
provide	O
multiple	O
views	O
of	O
the	O
same	O
scene	O
,	O
rather	O
than	O
just	O
two	O
.	O
</s>
<s>
Each	O
view	O
is	O
visible	O
from	O
a	O
different	O
range	O
of	O
positions	O
in	O
front	O
of	O
the	O
display	B-Device
.	O
</s>
<s>
This	O
allows	O
the	O
viewer	O
to	O
move	O
left-right	O
in	O
front	O
of	O
the	O
display	B-Device
and	O
see	O
the	O
correct	O
view	O
from	O
any	O
position	O
.	O
</s>
<s>
The	O
technology	O
includes	O
two	O
broad	O
classes	O
of	O
displays	O
:	O
those	O
that	O
use	O
head-tracking	O
to	O
ensure	O
that	O
each	O
of	O
the	O
viewer	O
's	O
two	O
eyes	O
sees	O
a	O
different	O
image	O
on	O
the	O
screen	O
,	O
and	O
those	O
that	O
display	B-Device
multiple	O
views	O
so	O
that	O
the	O
display	B-Device
does	O
not	O
need	O
to	O
know	O
where	O
the	O
viewers	O
 '	O
eyes	O
are	O
directed	O
.	O
</s>
<s>
Examples	O
of	O
autostereoscopic	B-Algorithm
displays	I-Algorithm
technology	O
include	O
lenticular	O
lens	O
,	O
parallax	B-Algorithm
barrier	I-Algorithm
,	O
volumetric	B-Algorithm
display	I-Algorithm
,	O
holography	B-Algorithm
and	O
light	B-Algorithm
field	I-Algorithm
displays	I-Algorithm
.	O
</s>
<s>
Laser	O
holography	B-Algorithm
,	O
in	O
its	O
original	O
"	O
pure	O
"	O
form	O
of	O
the	O
photographic	O
transmission	O
hologram	B-Algorithm
,	O
is	O
the	O
only	O
technology	O
yet	O
created	O
which	O
can	O
reproduce	O
an	O
object	O
or	O
scene	O
with	O
such	O
complete	O
realism	O
that	O
the	O
reproduction	O
is	O
visually	O
indistinguishable	O
from	O
the	O
original	O
,	O
given	O
the	O
original	O
lighting	O
conditions	O
.	O
</s>
<s>
It	O
creates	O
a	O
light	B-Algorithm
field	I-Algorithm
identical	O
to	O
that	O
which	O
emanated	O
from	O
the	O
original	O
scene	O
,	O
with	O
parallax	B-Device
about	O
all	O
axes	O
and	O
a	O
very	O
wide	O
viewing	O
angle	O
.	O
</s>
<s>
Most	O
people	O
have	O
never	O
seen	O
a	O
laser-lit	O
transmission	O
hologram	B-Algorithm
.	O
</s>
<s>
The	O
types	O
of	O
holograms	B-Algorithm
commonly	O
encountered	O
have	O
seriously	O
compromised	O
image	O
quality	O
so	O
that	O
ordinary	O
white	O
light	O
can	O
be	O
used	O
for	O
viewing	O
,	O
and	O
non-holographic	O
intermediate	O
imaging	O
processes	O
are	O
almost	O
always	O
resorted	O
to	O
,	O
as	O
an	O
alternative	O
to	O
using	O
powerful	O
and	O
hazardous	O
pulsed	O
lasers	O
,	O
when	O
living	O
subjects	O
are	O
photographed	O
.	O
</s>
<s>
Although	O
the	O
original	O
photographic	O
processes	O
have	O
proven	O
impractical	O
for	O
general	O
use	O
,	O
the	O
combination	O
of	O
computer-generated	O
holograms	B-Algorithm
(	O
CGH	O
)	O
and	O
optoelectronic	O
holographic	B-Algorithm
displays	I-Algorithm
,	O
both	O
under	O
development	O
for	O
many	O
years	O
,	O
has	O
the	O
potential	O
to	O
transform	O
the	O
half-century-old	O
pipe	O
dream	O
of	O
holographic	B-Algorithm
3D	B-Algorithm
television	I-Algorithm
into	O
a	O
reality	O
;	O
so	O
far	O
,	O
however	O
,	O
the	O
large	O
amount	O
of	O
calculation	O
required	O
to	O
generate	O
just	O
one	O
detailed	O
hologram	B-Algorithm
,	O
and	O
the	O
huge	O
bandwidth	O
required	O
to	O
transmit	O
a	O
stream	O
of	O
them	O
,	O
have	O
confined	O
this	O
technology	O
to	O
the	O
research	O
laboratory	O
.	O
</s>
<s>
In	O
2013	O
,	O
a	O
Silicon	O
Valley	O
company	O
,	O
LEIA	B-Algorithm
Inc	I-Algorithm
,	O
started	O
manufacturing	O
holographic	B-Algorithm
displays	I-Algorithm
well	O
suited	O
for	O
mobile	O
devices	O
(	O
watches	O
,	O
smartphones	O
or	O
tablets	O
)	O
using	O
a	O
multi-directional	O
backlight	O
and	O
allowing	O
a	O
wide	O
full-parallax	O
angle	O
view	O
to	O
see	O
3D	O
content	O
without	O
the	O
need	O
of	O
glasses	O
.	O
</s>
<s>
Volumetric	B-Algorithm
displays	I-Algorithm
use	O
some	O
physical	O
mechanism	O
to	O
display	B-Device
points	O
of	O
light	O
within	O
a	O
volume	O
.	O
</s>
<s>
Such	O
displays	O
use	O
voxels	B-Algorithm
instead	O
of	O
pixels	B-Algorithm
.	O
</s>
<s>
Volumetric	B-Algorithm
displays	I-Algorithm
include	O
multiplanar	O
displays	O
,	O
which	O
have	O
multiple	O
display	B-Device
planes	O
stacked	O
up	O
,	O
and	O
rotating	O
panel	O
displays	O
,	O
where	O
a	O
rotating	O
panel	O
sweeps	O
out	O
a	O
volume	O
.	O
</s>
<s>
Integral	B-Algorithm
imaging	I-Algorithm
is	O
a	O
technique	O
for	O
producing	O
3D	B-Algorithm
displays	I-Algorithm
which	O
are	O
both	O
autostereoscopic	B-Algorithm
and	O
multiscopic	B-General_Concept
,	O
meaning	O
that	O
the	O
3D	B-Algorithm
image	I-Algorithm
is	O
viewed	O
without	O
the	O
use	O
of	O
special	O
glasses	O
and	O
different	O
aspects	O
are	O
seen	O
when	O
it	O
is	O
viewed	O
from	O
positions	O
that	O
differ	O
either	O
horizontally	O
or	O
vertically	O
.	O
</s>
<s>
This	O
is	O
achieved	O
by	O
using	O
an	O
array	O
of	O
microlenses	O
(	O
akin	O
to	O
a	O
lenticular	O
lens	O
,	O
but	O
an	O
XY	O
or	O
"	O
fly	O
's	O
eye	O
"	O
array	O
in	O
which	O
each	O
lenslet	O
typically	O
forms	O
its	O
own	O
image	O
of	O
the	O
scene	O
without	O
assistance	O
from	O
a	O
larger	O
objective	O
lens	O
)	O
or	O
pinholes	B-Algorithm
to	O
capture	O
and	O
display	B-Device
the	O
scene	O
as	O
a	O
4D	O
light	B-Algorithm
field	I-Algorithm
,	O
producing	O
stereoscopic	B-Algorithm
images	I-Algorithm
that	O
exhibit	O
realistic	O
alterations	O
of	O
parallax	B-Device
and	O
perspective	B-Architecture
when	O
the	O
viewer	O
moves	O
left	O
,	O
right	O
,	O
up	O
,	O
down	O
,	O
closer	O
,	O
or	O
farther	O
away	O
.	O
</s>
<s>
Integral	B-Algorithm
imaging	I-Algorithm
may	O
not	O
technically	O
be	O
a	O
type	O
of	O
autostereoscopy	B-Algorithm
,	O
as	O
autostereoscopy	B-Algorithm
still	O
refers	O
to	O
the	O
generation	O
of	O
two	O
images	O
.	O
</s>
<s>
Wiggle	O
stereoscopy	B-Algorithm
is	O
an	O
image	O
display	B-Device
technique	O
achieved	O
by	O
quickly	O
alternating	O
display	B-Device
of	O
left	O
and	O
right	O
sides	O
of	O
a	O
stereogram	O
.	O
</s>
<s>
For	O
general-purpose	O
stereo	B-Algorithm
photography	I-Algorithm
,	O
where	O
the	O
goal	O
is	O
to	O
duplicate	O
natural	O
human	O
vision	O
and	O
give	O
a	O
visual	O
impression	O
as	O
close	O
as	O
possible	O
to	O
actually	O
being	O
there	O
,	O
the	O
correct	O
baseline	O
(	O
distance	O
between	O
where	O
the	O
right	O
and	O
left	O
images	O
are	O
taken	O
)	O
would	O
be	O
the	O
same	O
as	O
the	O
distance	O
between	O
the	O
eyes	O
.	O
</s>
<s>
The	O
concept	O
of	O
baseline	O
also	O
applies	O
to	O
other	O
branches	O
of	O
stereography	B-Algorithm
,	O
such	O
as	O
stereo	O
drawings	O
and	O
computer	B-Algorithm
generated	I-Algorithm
stereo	I-Algorithm
images	I-Algorithm
,	O
but	O
it	O
involves	O
the	O
point	O
of	O
view	O
chosen	O
rather	O
than	O
actual	O
physical	O
separation	O
of	O
cameras	O
or	O
lenses	O
.	O
</s>
<s>
The	O
concept	O
of	O
the	O
stereo	O
window	O
is	O
always	O
important	O
,	O
since	O
the	O
window	O
is	O
the	O
stereoscopic	B-Algorithm
image	I-Algorithm
of	O
the	O
external	O
boundaries	O
of	O
left	O
and	O
right	O
views	O
constituting	O
the	O
stereoscopic	B-Algorithm
image	I-Algorithm
.	O
</s>
<s>
But	O
these	O
objects	O
can	O
not	O
be	O
seen	O
as	O
too	O
close	O
,	O
since	O
there	O
is	O
always	O
a	O
limit	O
of	O
the	O
parallax	B-Device
range	O
for	O
comfortable	O
viewing	O
.	O
</s>
<s>
In	O
the	O
case	O
of	O
viewing	O
on	O
a	O
3D	B-Algorithm
TV	I-Algorithm
set	O
,	O
it	O
is	O
easier	O
to	O
place	O
the	O
window	O
in	O
front	O
of	O
the	O
image	O
,	O
and	O
to	O
let	O
the	O
window	O
in	O
the	O
plane	O
of	O
the	O
screen	O
.	O
</s>
<s>
Of	O
course	O
the	O
viewers	O
seated	O
beyond	O
will	O
see	O
the	O
window	O
more	O
remote	O
,	O
but	O
if	O
the	O
image	O
is	O
made	O
in	O
normal	O
conditions	O
,	O
so	O
that	O
the	O
first	O
row	O
viewers	O
see	O
this	O
background	O
at	O
the	O
infinite	O
,	O
the	O
other	O
viewers	O
,	O
seated	O
behind	O
,	O
will	O
also	O
see	O
this	O
background	O
at	O
the	O
infinite	O
,	O
since	O
the	O
parallax	B-Device
of	O
this	O
background	O
is	O
equal	O
to	O
the	O
average	O
human	O
interocular	O
.	O
</s>
<s>
In	O
stereo	B-Algorithm
photography	I-Algorithm
window	O
adjustments	O
is	O
accomplished	O
by	O
shifting/cropping	O
the	O
images	O
,	O
in	O
other	O
forms	O
of	O
stereoscopy	B-Algorithm
such	O
as	O
drawings	O
and	O
computer	O
generated	O
images	O
the	O
window	O
is	O
built	O
into	O
the	O
design	O
of	O
the	O
images	O
as	O
they	O
are	O
generated	O
.	O
</s>
<s>
While	O
stereoscopic	B-Algorithm
images	I-Algorithm
have	O
typically	O
been	O
used	O
for	O
amusement	O
,	O
including	O
stereographic	B-Algorithm
cards	I-Algorithm
,	O
3D	B-Algorithm
films	I-Algorithm
,	O
3D	B-Algorithm
television	I-Algorithm
,	O
stereoscopic	B-Application
video	I-Application
games	I-Application
,	O
printings	O
using	O
anaglyph	B-Algorithm
and	O
pictures	O
,	O
posters	O
and	O
books	O
of	O
autostereograms	B-Algorithm
,	O
there	O
are	O
also	O
other	O
uses	O
of	O
this	O
technology	O
.	O
</s>
<s>
Salvador	O
Dalí	O
created	O
some	O
impressive	O
stereograms	B-Algorithm
in	O
his	O
exploration	O
in	O
a	O
variety	O
of	O
optical	O
illusions	O
.	O
</s>
<s>
Red-and-cyan	O
anaglyph	B-Algorithm
stereoscopic	B-Algorithm
images	I-Algorithm
have	O
also	O
been	O
painted	O
by	O
hand	O
.	O
</s>
<s>
In	O
the	O
19th	O
century	O
,	O
it	O
was	O
realized	O
that	O
stereoscopic	B-Algorithm
images	I-Algorithm
provided	O
an	O
opportunity	O
for	O
people	O
to	O
experience	O
places	O
and	O
things	O
far	O
away	O
,	O
and	O
many	O
tour	O
sets	O
were	O
produced	O
,	O
and	O
books	O
were	O
published	O
allowing	O
people	O
to	O
learn	O
about	O
geography	O
,	O
science	O
,	O
history	O
,	O
and	O
other	O
subjects	O
.	O
</s>
<s>
The	O
Mars	B-Application
Exploration	O
Rovers	O
,	O
launched	O
by	O
NASA	O
in	O
2003	O
to	O
explore	O
the	O
surface	O
of	O
Mars	B-Application
,	O
are	O
equipped	O
with	O
unique	O
cameras	O
that	O
allow	O
researchers	O
to	O
view	O
stereoscopic	B-Algorithm
images	I-Algorithm
of	O
the	O
surface	O
of	O
Mars	B-Application
.	O
</s>
<s>
The	O
two	O
cameras	O
that	O
make	O
up	O
each	O
rover	O
's	O
Pancam	B-Algorithm
are	O
situated	O
1.5m	O
above	O
the	O
ground	O
surface	O
,	O
and	O
are	O
separated	O
by	O
30cm	O
,	O
with	O
1	O
degree	O
of	O
toe-in	O
.	O
</s>
<s>
This	O
allows	O
the	O
image	O
pairs	O
to	O
be	O
made	O
into	O
scientifically	O
useful	O
stereoscopic	B-Algorithm
images	I-Algorithm
,	O
which	O
can	O
be	O
viewed	O
as	O
stereograms	B-Algorithm
,	O
anaglyphs	B-Algorithm
,	O
or	O
processed	O
into	O
3D	O
computer	O
images	O
.	O
</s>
<s>
The	O
ability	O
to	O
create	O
realistic	O
3D	B-Algorithm
images	I-Algorithm
from	O
a	O
pair	O
of	O
cameras	O
at	O
roughly	O
human-height	O
gives	O
researchers	O
increased	O
insight	O
as	O
to	O
the	O
nature	O
of	O
the	O
landscapes	O
being	O
viewed	O
.	O
</s>
<s>
In	O
environments	O
without	O
hazy	O
atmospheres	O
or	O
familiar	O
landmarks	O
,	O
humans	O
rely	O
on	O
stereoscopic	B-Algorithm
clues	O
to	O
judge	O
distance	O
.	O
</s>
<s>
Multiple	O
camera	O
stereoscopic	B-Algorithm
systems	O
like	O
the	O
Pancam	B-Algorithm
address	O
this	O
problem	O
with	O
uncrewed	O
space	O
exploration	O
.	O
</s>
<s>
Stereogram	O
cards	O
and	O
vectographs	B-Algorithm
are	O
used	O
by	O
optometrists	O
,	O
ophthalmologists	O
,	O
orthoptists	O
and	O
vision	O
therapists	O
in	O
the	O
diagnosis	O
and	O
treatment	O
of	O
binocular	B-Algorithm
vision	I-Algorithm
and	O
accommodative	O
disorders	O
.	O
</s>
<s>
Stereopair	B-Algorithm
photographs	O
provided	O
a	O
way	O
for	O
3-dimensional	O
(	O
3D	O
)	O
visualisations	O
of	O
aerial	O
photographs	O
;	O
since	O
about	O
2000	O
,	O
3D	O
aerial	O
views	O
are	O
mainly	O
based	O
on	O
digital	O
stereo	O
imaging	O
technologies	O
.	O
</s>
<s>
Recently	O
,	O
computer	B-Application
vision	I-Application
scientists	O
tried	O
to	O
find	O
techniques	O
to	O
attack	O
the	O
visual	O
redundancy	O
of	O
stereopairs	B-Algorithm
with	O
the	O
aim	O
to	O
define	O
compressed	O
version	O
of	O
stereopair	B-Algorithm
files	O
.	O
</s>
<s>
Cartographers	O
generate	O
today	O
stereopairs	B-Algorithm
using	O
computer	O
programs	O
in	O
order	O
to	O
visualise	O
topography	O
in	O
three	O
dimensions	O
.	O
</s>
<s>
In	O
biology	O
and	O
chemistry	O
,	O
complex	O
molecular	O
structures	O
are	O
often	O
rendered	O
in	O
stereopairs	B-Algorithm
.	O
</s>
