<s>
Stereopsis	B-Algorithm
(	O
)	O
is	O
the	O
component	O
of	O
depth	O
perception	O
retrieved	O
through	O
binocular	B-Algorithm
vision	I-Algorithm
.	O
</s>
<s>
Stereopsis	B-Algorithm
is	O
not	O
the	O
only	O
contributor	O
to	O
depth	O
perception	O
,	O
but	O
it	O
is	O
a	O
major	O
one	O
.	O
</s>
<s>
Binocular	B-Algorithm
vision	I-Algorithm
happens	O
because	O
each	O
eye	O
receives	O
a	O
different	O
image	O
because	O
they	O
are	O
in	O
slightly	O
different	O
positions	O
on	O
one	O
's	O
head	O
(	O
left	O
and	O
right	O
eyes	O
)	O
.	O
</s>
<s>
These	O
positional	O
differences	O
are	O
referred	O
to	O
as	O
"	O
horizontal	B-Algorithm
disparities	I-Algorithm
"	O
or	O
,	O
more	O
generally	O
,	O
"	O
binocular	O
disparities	O
"	O
.	O
</s>
<s>
While	O
binocular	O
disparities	O
are	O
naturally	O
present	O
when	O
viewing	O
a	O
real	O
three-dimensional	O
scene	O
with	O
two	O
eyes	O
,	O
they	O
can	O
also	O
be	O
simulated	O
by	O
artificially	O
presenting	O
two	O
different	O
images	O
separately	O
to	O
each	O
eye	O
using	O
a	O
method	O
called	O
stereoscopy	B-Algorithm
.	O
</s>
<s>
The	O
perception	O
of	O
depth	O
in	O
such	O
cases	O
is	O
also	O
referred	O
to	O
as	O
"	O
stereoscopic	B-Algorithm
depth	O
"	O
.	O
</s>
<s>
Therefore	O
,	O
the	O
term	O
stereopsis	B-Algorithm
(	O
or	O
stereoscopic	B-Algorithm
depth	O
)	O
can	O
also	O
refer	O
specifically	O
to	O
the	O
unique	O
impression	O
of	O
depth	O
associated	O
with	O
binocular	B-Algorithm
vision	I-Algorithm
(	O
colloquially	O
referred	O
to	O
as	O
seeing	O
"	O
in	O
3D	O
"	O
)	O
.	O
</s>
<s>
There	O
are	O
two	O
distinct	O
aspects	O
to	O
stereopsis	B-Algorithm
:	O
coarse	O
stereopsis	B-Algorithm
and	O
fine	O
stereopsis	B-Algorithm
,	O
and	O
provide	O
depth	O
information	O
of	O
different	O
degree	O
of	O
spatial	O
and	O
temporal	O
precision	O
.	O
</s>
<s>
Coarse	O
stereopsis	B-Algorithm
(	O
also	O
called	O
gross	O
stereopsis	B-Algorithm
)	O
appears	O
to	O
be	O
used	O
to	O
judge	O
stereoscopic	B-Algorithm
motion	O
in	O
the	O
periphery	O
.	O
</s>
<s>
It	O
provides	O
the	O
sense	O
of	O
being	O
immersed	O
in	O
one	O
's	O
surroundings	O
and	O
is	O
therefore	O
sometimes	O
also	O
referred	O
to	O
as	O
qualitative	O
stereopsis	B-Algorithm
.	O
</s>
<s>
Coarse	O
stereopsis	B-Algorithm
is	O
important	O
for	O
orientation	O
in	O
space	O
while	O
moving	O
,	O
for	O
example	O
when	O
descending	O
a	O
flight	O
of	O
stairs	O
.	O
</s>
<s>
Fine	O
stereopsis	B-Algorithm
is	O
mainly	O
based	O
on	O
static	O
differences	O
.	O
</s>
<s>
It	O
allows	O
the	O
individual	O
to	O
determine	O
the	O
depth	O
of	O
objects	O
in	O
the	O
central	O
visual	O
area	O
(	O
Panum	O
's	O
fusional	O
area	O
)	O
and	O
is	O
therefore	O
also	O
called	O
quantitative	O
stereopsis	B-Algorithm
.	O
</s>
<s>
It	O
is	O
typically	O
measured	O
in	O
random-dot	O
tests	O
;	O
persons	O
having	O
coarse	O
but	O
no	O
fine	O
stereopsis	B-Algorithm
are	O
often	O
unable	O
to	O
perform	O
on	O
random-dot	O
tests	O
,	O
also	O
due	O
to	O
visual	O
crowding	O
which	O
is	O
based	O
on	O
interaction	O
effects	O
from	O
adjacent	O
visual	O
contours	O
.	O
</s>
<s>
Fine	O
stereopsis	B-Algorithm
is	O
important	O
for	O
fine-motor	O
tasks	O
such	O
as	O
threading	O
a	O
needle	O
.	O
</s>
<s>
The	O
stereopsis	B-Algorithm
which	O
an	O
individual	O
can	O
achieve	O
is	O
limited	O
by	O
the	O
level	O
of	O
visual	O
acuity	O
of	O
the	O
poorer	O
eye	O
.	O
</s>
<s>
In	O
particular	O
,	O
patients	O
who	O
have	O
comparatively	O
lower	O
visual	O
acuity	O
tend	O
to	O
need	O
relatively	O
larger	O
spatial	O
frequencies	O
to	O
be	O
present	O
in	O
the	O
input	O
images	O
,	O
else	O
they	O
cannot	O
achieve	O
stereopsis	B-Algorithm
.	O
</s>
<s>
Fine	O
stereopsis	B-Algorithm
requires	O
both	O
eyes	O
to	O
have	O
a	O
good	O
visual	O
acuity	O
in	O
order	O
to	O
detect	O
small	O
spatial	O
differences	O
,	O
and	O
is	O
easily	O
disrupted	O
by	O
early	O
visual	O
deprivation	O
.	O
</s>
<s>
There	O
are	O
indications	O
that	O
in	O
the	O
course	O
of	O
the	O
development	O
of	O
the	O
visual	O
system	O
in	O
infants	O
,	O
coarse	O
stereopsis	B-Algorithm
may	O
develop	O
before	O
fine	O
stereopsis	B-Algorithm
and	O
that	O
coarse	O
stereopsis	B-Algorithm
guides	O
the	O
vergence	B-Algorithm
movements	O
which	O
are	O
needed	O
in	O
order	O
for	O
fine	O
stereopsis	B-Algorithm
to	O
develop	O
in	O
a	O
subsequent	O
stage	O
.	O
</s>
<s>
Furthermore	O
,	O
there	O
are	O
indications	O
that	O
coarse	O
stereopsis	B-Algorithm
is	O
the	O
mechanism	O
that	O
keeps	O
the	O
two	O
eyes	O
aligned	O
after	O
strabismus	O
surgery	O
.	O
</s>
<s>
It	O
has	O
also	O
been	O
suggested	O
to	O
distinguish	O
between	O
two	O
different	O
types	O
of	O
stereoscopic	B-Algorithm
depth	O
perception	O
:	O
static	O
depth	O
perception	O
(	O
or	O
static	O
stereo	O
perception	O
)	O
and	O
motion-in-depth	O
perception	O
(	O
or	O
stereo	O
motion	O
perception	O
)	O
.	O
</s>
<s>
Some	O
individuals	O
who	O
have	O
strabismus	O
and	O
show	O
no	O
depth	O
perception	O
using	O
static	O
stereotests	O
(	O
in	O
particular	O
,	O
using	O
Titmus	O
tests	O
,	O
see	O
this	O
article	O
's	O
section	O
on	O
contour	O
stereotests	O
)	O
do	O
perceive	O
motion	O
in	O
depth	O
when	O
tested	O
using	O
dynamic	O
random	B-Algorithm
dot	I-Algorithm
stereograms	I-Algorithm
.	O
</s>
<s>
One	O
study	O
found	O
the	O
combination	O
of	O
motion	O
stereopsis	B-Algorithm
and	O
no	O
static	O
stereopsis	B-Algorithm
to	O
be	O
present	O
only	O
in	O
exotropes	O
,	O
not	O
in	O
esotropes	O
.	O
</s>
<s>
There	O
are	O
strong	O
indications	O
that	O
the	O
stereoscopic	B-Algorithm
mechanism	O
consists	O
of	O
at	O
least	O
two	O
perceptual	O
mechanisms	O
,	O
possibly	O
three	O
.	O
</s>
<s>
Coarse	O
and	O
fine	O
stereopsis	B-Algorithm
are	O
processed	O
by	O
two	O
different	O
physiological	O
subsystems	O
,	O
with	O
a	O
coarse	O
stereopsis	B-Algorithm
being	O
derived	O
from	O
diplopic	O
stimuli	O
(	O
that	O
is	O
,	O
stimuli	O
with	O
disparities	O
well	O
beyond	O
the	O
range	O
of	O
binocular	B-Algorithm
fusion	I-Algorithm
)	O
and	O
yielding	O
only	O
a	O
vague	O
impression	O
of	O
depth	O
magnitude	O
.	O
</s>
<s>
Coarse	O
stereopsis	B-Algorithm
appears	O
to	O
be	O
associated	O
with	O
the	O
magno	O
pathway	O
which	O
processes	O
low	O
spatial	O
frequency	O
disparities	O
and	O
motion	O
,	O
and	O
fine	O
stereopsis	B-Algorithm
with	O
the	O
parvo	O
pathway	O
which	O
processes	O
high	O
spatial	O
frequency	O
disparities	O
.	O
</s>
<s>
The	O
coarse	O
stereoscopic	B-Algorithm
system	O
seems	O
to	O
be	O
able	O
to	O
provide	O
residual	O
binocular	O
depth	O
information	O
in	O
some	O
individuals	O
who	O
lack	O
fine	O
stereopsis	B-Algorithm
.	O
</s>
<s>
Individuals	O
have	O
been	O
found	O
to	O
integrate	O
the	O
various	O
stimuli	O
,	O
for	O
example	O
stereoscopic	B-Algorithm
cues	O
and	O
motion	O
occlusion	O
,	O
in	O
different	O
ways	O
.	O
</s>
<s>
How	O
the	O
brain	O
combines	O
the	O
different	O
cues	O
–	O
including	O
stereo	O
,	O
motion	O
,	O
vergence	B-Algorithm
angle	O
and	O
monocular	O
cues	O
–	O
for	O
sensing	O
motion	O
in	O
depth	O
and	O
3D	O
object	O
position	O
is	O
an	O
area	O
of	O
active	O
research	O
in	O
vision	O
science	O
and	O
neighboring	O
disciplines	O
.	O
</s>
<s>
Not	O
everyone	O
has	O
the	O
same	O
ability	O
to	O
see	O
using	O
stereopsis	B-Algorithm
.	O
</s>
<s>
One	O
study	O
shows	O
that	O
97.3	O
%	O
are	O
able	O
to	O
distinguish	O
depth	O
at	O
horizontal	B-Algorithm
disparities	I-Algorithm
of	O
2.3	O
minutes	O
of	O
arc	O
or	O
smaller	O
,	O
and	O
at	O
least	O
80%	O
could	O
distinguish	O
depth	O
at	O
horizontal	O
differences	O
of	O
30	O
seconds	O
of	O
arc	O
.	O
</s>
<s>
Stereopsis	B-Algorithm
has	O
a	O
positive	O
impact	O
on	O
exercising	O
practical	O
tasks	O
such	O
as	O
needle-threading	O
,	O
ball-catching	O
(	O
especially	O
in	O
fast	O
ball	O
games	O
)	O
,	O
pouring	O
liquids	O
,	O
and	O
others	O
.	O
</s>
<s>
Professional	O
activity	O
may	O
involve	O
operating	O
stereoscopic	B-Algorithm
instruments	O
such	O
as	O
a	O
binocular	O
microscope	O
.	O
</s>
<s>
While	O
some	O
of	O
these	O
tasks	O
may	O
profit	O
from	O
compensation	O
of	O
the	O
visual	O
system	O
by	O
means	O
of	O
other	O
depth	O
cues	O
,	O
there	O
are	O
some	O
roles	O
for	O
which	O
stereopsis	B-Algorithm
is	O
imperative	O
.	O
</s>
<s>
Occupations	O
requiring	O
the	O
precise	O
judgment	O
of	O
distance	O
sometimes	O
include	O
a	O
requirement	O
to	O
demonstrate	O
some	O
level	O
of	O
stereopsis	B-Algorithm
;	O
in	O
particular	O
,	O
there	O
is	O
such	O
a	O
requirement	O
for	O
aeroplane	O
pilots	O
(	O
even	O
if	O
the	O
first	O
pilot	O
to	O
fly	O
around	O
the	O
world	O
alone	O
,	O
Wiley	O
Post	O
,	O
accomplished	O
his	O
feat	O
with	O
monocular	O
vision	O
only	O
.	O
)	O
</s>
<s>
As	O
to	O
car	O
driving	O
,	O
a	O
study	O
found	O
a	O
positive	O
impact	O
of	O
stereopsis	B-Algorithm
in	O
specific	O
situations	O
at	O
intermediate	O
distances	O
only	O
;	O
furthermore	O
,	O
a	O
study	O
on	O
elderly	O
persons	O
found	O
that	O
glare	O
,	O
visual	O
field	O
loss	O
,	O
and	O
useful	O
field	O
of	O
view	O
were	O
significant	O
predictors	O
of	O
crash	O
involvement	O
,	O
whereas	O
the	O
elderly	O
persons	O
 '	O
values	O
of	O
visual	O
acuity	O
,	O
contrast	O
sensitivity	O
,	O
and	O
stereoacuity	O
were	O
not	O
associated	O
with	O
crashes	O
.	O
</s>
<s>
Binocular	B-Algorithm
vision	I-Algorithm
has	O
further	O
advantages	O
aside	O
from	O
stereopsis	B-Algorithm
,	O
in	O
particular	O
the	O
enhancement	O
of	O
vision	O
quality	O
through	O
binocular	O
summation	O
;	O
persons	O
with	O
strabismus	O
(	O
even	O
those	O
who	O
have	O
no	O
double	O
vision	O
)	O
have	O
lower	O
scores	O
of	O
binocular	O
summation	O
,	O
and	O
this	O
appears	O
to	O
incite	O
persons	O
with	O
strabismus	O
to	O
close	O
one	O
eye	O
in	O
visually	O
demanding	O
situations	O
.	O
</s>
<s>
It	O
has	O
long	O
been	O
recognized	O
that	O
full	O
binocular	B-Algorithm
vision	I-Algorithm
,	O
including	O
stereopsis	B-Algorithm
,	O
is	O
an	O
important	O
factor	O
in	O
the	O
stabilization	O
of	O
post-surgical	O
outcome	O
of	O
strabismus	O
corrections	O
.	O
</s>
<s>
Many	O
persons	O
lacking	O
stereopsis	B-Algorithm
have	O
(	O
or	O
have	O
had	O
)	O
visible	O
strabismus	O
,	O
which	O
is	O
known	O
to	O
have	O
a	O
potential	O
socioeconomic	O
impact	O
on	O
children	O
and	O
adults	O
.	O
</s>
<s>
It	O
has	O
been	O
noted	O
that	O
with	O
the	O
growing	O
introduction	O
of	O
3D	O
display	O
technology	O
in	O
entertainment	O
and	O
in	O
medical	O
and	O
scientific	O
imaging	O
,	O
high	O
quality	O
binocular	B-Algorithm
vision	I-Algorithm
including	O
stereopsis	B-Algorithm
may	O
become	O
a	O
key	O
capability	O
for	O
success	O
in	O
modern	O
society	O
.	O
</s>
<s>
Nonetheless	O
,	O
there	O
are	O
indications	O
that	O
the	O
lack	O
of	O
stereo	B-Algorithm
vision	I-Algorithm
may	O
lead	O
persons	O
to	O
compensate	O
by	O
other	O
means	O
:	O
in	O
particular	O
,	O
stereo	B-Algorithm
blindness	I-Algorithm
may	O
give	O
people	O
an	O
advantage	O
when	O
depicting	O
a	O
scene	O
using	O
monocular	O
depth	O
cues	O
of	O
all	O
kinds	O
,	O
and	O
among	O
artists	O
there	O
appear	O
to	O
be	O
a	O
disproportionately	O
high	O
number	O
of	O
persons	O
lacking	O
stereopsis	B-Algorithm
.	O
</s>
<s>
In	O
particular	O
,	O
a	O
case	O
has	O
been	O
made	O
that	O
Rembrandt	O
may	O
have	O
been	O
stereoblind	B-Algorithm
.	O
</s>
<s>
Stereopsis	B-Algorithm
was	O
first	O
explained	O
by	O
Charles	O
Wheatstone	O
in	O
1838	O
:	O
“	O
…	O
the	O
mind	O
perceives	O
an	O
object	O
of	O
three	O
dimensions	O
by	O
means	O
of	O
the	O
two	O
dissimilar	O
pictures	O
projected	O
by	O
it	O
on	O
the	O
two	O
retinæ	O
…	O
”	O
.	O
</s>
<s>
Objects	O
at	O
different	O
distances	O
from	O
the	O
eyes	O
project	O
images	O
in	O
the	O
two	O
eyes	O
that	O
differ	O
in	O
their	O
horizontal	O
positions	O
,	O
giving	O
the	O
depth	O
cue	O
of	O
horizontal	B-Algorithm
disparity	I-Algorithm
,	O
also	O
known	O
as	O
retinal	B-Algorithm
disparity	I-Algorithm
and	O
as	O
binocular	O
disparity	O
.	O
</s>
<s>
Wheatstone	O
showed	O
that	O
this	O
was	O
an	O
effective	O
depth	O
cue	O
by	O
creating	O
the	O
illusion	B-Application
of	O
depth	O
from	O
flat	O
pictures	O
that	O
differed	O
only	O
in	O
horizontal	B-Algorithm
disparity	I-Algorithm
.	O
</s>
<s>
To	O
display	O
his	O
pictures	O
separately	O
to	O
the	O
two	O
eyes	O
,	O
Wheatstone	O
invented	O
the	O
stereoscope	B-Algorithm
.	O
</s>
<s>
Leonardo	B-Application
da	I-Application
Vinci	I-Application
had	O
also	O
realized	O
that	O
objects	O
at	O
different	O
distances	O
from	O
the	O
eyes	O
project	O
images	O
in	O
the	O
two	O
eyes	O
that	O
differ	O
in	O
their	O
horizontal	O
positions	O
,	O
but	O
had	O
concluded	O
only	O
that	O
this	O
made	O
it	O
impossible	O
for	O
a	O
painter	O
to	O
portray	O
a	O
realistic	O
depiction	O
of	O
the	O
depth	O
in	O
a	O
scene	O
from	O
a	O
single	O
canvas	O
.	O
</s>
<s>
Had	O
he	O
chosen	O
any	O
other	O
near	O
object	O
,	O
he	O
might	O
have	O
discovered	O
horizontal	B-Algorithm
disparity	I-Algorithm
of	O
its	O
features	O
.	O
</s>
<s>
Stereoscopy	B-Algorithm
became	O
popular	O
during	O
Victorian	O
times	O
with	O
the	O
invention	O
of	O
the	O
prism	O
stereoscope	B-Algorithm
by	O
David	O
Brewster	O
.	O
</s>
<s>
This	O
,	O
combined	O
with	O
photography	O
,	O
meant	O
that	O
tens	O
of	O
thousands	O
of	O
stereograms	B-Algorithm
were	O
produced	O
.	O
</s>
<s>
Until	O
about	O
the	O
1960s	O
,	O
research	O
into	O
stereopsis	B-Algorithm
was	O
dedicated	O
to	O
exploring	O
its	O
limits	O
and	O
its	O
relationship	O
to	O
singleness	O
of	O
vision	O
.	O
</s>
<s>
In	O
the	O
1960s	O
,	O
Bela	O
Julesz	O
invented	O
random-dot	B-Algorithm
stereograms	I-Algorithm
.	O
</s>
<s>
Unlike	O
previous	O
stereograms	B-Algorithm
,	O
in	O
which	O
each	O
half	O
image	O
showed	O
recognizable	O
objects	O
,	O
each	O
half	O
image	O
of	O
the	O
first	O
random-dot	B-Algorithm
stereograms	I-Algorithm
showed	O
a	O
square	O
matrix	O
of	O
about	O
10,000	O
small	O
dots	O
,	O
with	O
each	O
dot	O
having	O
a	O
50%	O
probability	O
of	O
being	O
black	O
or	O
white	O
.	O
</s>
<s>
The	O
two	O
half	O
images	O
of	O
a	O
random-dot	B-Algorithm
stereogram	I-Algorithm
were	O
essentially	O
identical	O
,	O
except	O
that	O
one	O
had	O
a	O
square	O
area	O
of	O
dots	O
shifted	O
horizontally	O
by	O
one	O
or	O
two	O
dot	O
diameters	O
,	O
giving	O
horizontal	B-Algorithm
disparity	I-Algorithm
.	O
</s>
<s>
Random-dot	B-Algorithm
stereograms	I-Algorithm
highlighted	O
a	O
problem	O
for	O
stereopsis	B-Algorithm
,	O
the	O
correspondence	B-Algorithm
problem	I-Algorithm
.	O
</s>
<s>
Our	O
visual	O
systems	O
clearly	O
solve	O
the	O
correspondence	B-Algorithm
problem	I-Algorithm
,	O
in	O
that	O
we	O
see	O
the	O
intended	O
depth	O
instead	O
of	O
a	O
fog	O
of	O
false	O
matches	O
.	O
</s>
<s>
This	O
established	O
the	O
neural	O
basis	O
for	O
stereopsis	B-Algorithm
.	O
</s>
<s>
In	O
the	O
1980s	O
,	O
Gian	O
Poggio	O
and	O
others	O
found	O
neurons	O
in	O
V2	O
of	O
the	O
monkey	O
brain	O
that	O
responded	O
to	O
the	O
depth	O
of	O
random-dot	B-Algorithm
stereograms	I-Algorithm
.	O
</s>
<s>
In	O
the	O
1970s	O
,	O
Christopher	O
Tyler	O
invented	O
autostereograms	B-Algorithm
,	O
random-dot	B-Algorithm
stereograms	I-Algorithm
that	O
can	O
be	O
viewed	O
without	O
a	O
stereoscope	B-Algorithm
.	O
</s>
<s>
This	O
led	O
to	O
the	O
popular	O
Magic	B-General_Concept
Eye	I-General_Concept
pictures	O
.	O
</s>
<s>
In	O
1989	O
Antonio	O
Medina	O
Puerta	O
demonstrated	O
with	O
photographs	O
that	O
retinal	O
images	O
with	O
no	O
parallax	O
disparity	O
but	O
with	O
different	O
shadows	O
are	O
fused	O
stereoscopically	B-Algorithm
,	O
imparting	O
depth	O
perception	O
to	O
the	O
imaged	O
scene	O
.	O
</s>
<s>
He	O
named	O
the	O
phenomenon	O
"	O
shadow	O
stereopsis	B-Algorithm
"	O
.	O
</s>
<s>
Shadows	O
are	O
therefore	O
an	O
important	O
,	O
stereoscopic	B-Algorithm
cue	O
for	O
depth	O
perception	O
.	O
</s>
<s>
He	O
showed	O
how	O
effective	O
the	O
phenomenon	O
is	O
by	O
taking	O
two	O
photographs	O
of	O
the	O
Moon	O
at	O
different	O
times	O
,	O
and	O
therefore	O
with	O
different	O
shadows	O
,	O
making	O
the	O
Moon	O
to	O
appear	O
in	O
3D	O
stereoscopically	B-Algorithm
,	O
despite	O
the	O
absence	O
of	O
any	O
other	O
stereoscopic	B-Algorithm
cue	O
.	O
</s>
<s>
A	O
stereoscope	B-Algorithm
is	O
a	O
device	O
by	O
which	O
each	O
eye	O
can	O
be	O
presented	O
with	O
different	O
images	O
,	O
allowing	O
stereopsis	B-Algorithm
to	O
be	O
stimulated	O
with	O
two	O
pictures	O
,	O
one	O
for	O
each	O
eye	O
.	O
</s>
<s>
This	O
has	O
led	O
to	O
various	O
crazes	O
for	O
stereopsis	B-Algorithm
,	O
usually	O
prompted	O
by	O
new	O
sorts	O
of	O
stereoscopes	B-Algorithm
.	O
</s>
<s>
In	O
Victorian	O
times	O
it	O
was	O
the	O
prism	O
stereoscope	B-Algorithm
(	O
allowing	O
stereo	B-Algorithm
photographs	I-Algorithm
to	O
be	O
viewed	O
)	O
,	O
while	O
in	O
the	O
1920s	O
it	O
was	O
red-green	B-Algorithm
glasses	I-Algorithm
(	O
allowing	O
stereo	O
movies	O
to	O
be	O
viewed	O
)	O
.	O
</s>
<s>
In	O
1939	O
the	O
concept	O
of	O
the	O
prism	O
stereoscope	B-Algorithm
was	O
reworked	O
into	O
the	O
technologically	O
more	O
complex	O
View-Master	O
,	O
which	O
remains	O
in	O
production	O
today	O
.	O
</s>
<s>
In	O
the	O
1950s	O
polarizing	O
glasses	O
allowed	O
stereopsis	B-Algorithm
of	O
coloured	O
movies	O
.	O
</s>
<s>
In	O
the	O
1990s	O
Magic	B-General_Concept
Eye	I-General_Concept
pictures	O
(	O
autostereograms	B-Algorithm
)	O
–	O
which	O
did	O
not	O
require	O
a	O
stereoscope	B-Algorithm
,	O
but	O
relied	O
on	O
viewers	O
using	O
a	O
form	O
of	O
free	O
fusion	O
so	O
that	O
each	O
eye	O
views	O
different	O
images	O
–	O
were	O
introduced	O
.	O
</s>
<s>
Stereopsis	B-Algorithm
appears	O
to	O
be	O
processed	O
in	O
the	O
visual	O
cortex	O
of	O
mammals	O
in	O
binocular	O
cells	O
having	O
receptive	O
fields	O
in	O
different	O
horizontal	O
positions	O
in	O
the	O
two	O
eyes	O
.	O
</s>
<s>
Nevertheless	O
,	O
stereopsis	B-Algorithm
is	O
possible	O
with	O
double	O
vision	O
.	O
</s>
<s>
This	O
form	O
of	O
stereopsis	B-Algorithm
was	O
called	O
qualitative	O
stereopsis	B-Algorithm
by	O
Kenneth	O
Ogle	O
.	O
</s>
<s>
If	O
the	O
images	O
are	O
very	O
different	O
(	O
such	O
as	O
by	O
going	O
cross-eyed	O
,	O
or	O
by	O
presenting	O
different	O
images	O
in	O
a	O
stereoscope	B-Algorithm
)	O
then	O
one	O
image	O
at	O
a	O
time	O
may	O
be	O
seen	O
,	O
a	O
phenomenon	O
known	O
as	O
binocular	O
rivalry	O
.	O
</s>
<s>
There	O
is	O
a	O
hysteresis	O
effect	O
associated	O
with	O
stereopsis	B-Algorithm
.	O
</s>
<s>
Once	O
fusion	O
and	O
stereopsis	B-Algorithm
have	O
stabilized	O
,	O
fusion	O
and	O
stereopsis	B-Algorithm
can	O
be	O
maintained	O
even	O
if	O
the	O
two	O
images	O
are	O
pulled	O
apart	O
slowly	O
and	O
symmetrically	O
to	O
a	O
certain	O
extent	O
in	O
the	O
horizontal	O
direction	O
.	O
</s>
<s>
This	O
effect	O
,	O
first	O
demonstrated	O
on	O
a	O
random	B-Algorithm
dot	I-Algorithm
stereogram	I-Algorithm
,	O
was	O
initially	O
interpreted	O
as	O
an	O
extension	O
of	O
Panum	O
's	O
fusional	O
area	O
.	O
</s>
<s>
Later	O
it	O
was	O
shown	O
that	O
the	O
hysteresis	O
effect	O
reaches	O
far	O
beyond	O
Panum	O
's	O
fusional	O
area	O
,	O
and	O
that	O
stereoscopic	B-Algorithm
depth	O
can	O
be	O
perceived	O
in	O
random-line	O
stereograms	B-Algorithm
despite	O
the	O
presence	O
of	O
cyclodisparities	B-Algorithm
of	O
about	O
15	O
deg	O
,	O
and	O
this	O
has	O
been	O
interpreted	O
as	O
stereopsis	B-Algorithm
with	O
diplopia	O
.	O
</s>
<s>
Under	O
normal	O
circumstances	O
,	O
the	O
depth	O
specified	O
by	O
stereopsis	B-Algorithm
agrees	O
with	O
other	O
depth	O
cues	O
,	O
such	O
as	O
motion	O
parallax	O
(	O
when	O
an	O
observer	O
moves	O
while	O
looking	O
at	O
one	O
point	O
in	O
a	O
scene	O
,	O
the	O
fixation	O
point	O
,	O
points	O
nearer	O
and	O
farther	O
than	O
the	O
fixation	O
point	O
appear	O
to	O
move	O
against	O
or	O
with	O
the	O
movement	O
,	O
respectively	O
,	O
at	O
velocities	O
proportional	O
to	O
the	O
distance	O
from	O
the	O
fixation	O
point	O
)	O
,	O
and	O
pictorial	O
cues	O
such	O
as	O
superimposition	O
(	O
nearer	O
objects	O
cover	O
up	O
farther	O
objects	O
)	O
and	O
familiar	O
size	O
(	O
nearer	O
objects	O
appear	O
bigger	O
than	O
farther	O
objects	O
)	O
.	O
</s>
<s>
However	O
,	O
by	O
using	O
a	O
stereoscope	B-Algorithm
,	O
researchers	O
have	O
been	O
able	O
to	O
oppose	O
various	O
depth	O
cues	O
including	O
stereopsis	B-Algorithm
.	O
</s>
<s>
The	O
most	O
drastic	O
version	O
of	O
this	O
is	O
pseudoscopy	O
,	O
in	O
which	O
the	O
half-images	O
of	O
stereograms	B-Algorithm
are	O
swapped	O
between	O
the	O
eyes	O
,	O
reversing	O
the	O
binocular	O
disparity	O
.	O
</s>
<s>
The	O
stereoscopic	B-Algorithm
information	O
went	O
along	O
with	O
the	O
overall	O
depth	O
.	O
</s>
<s>
Computer	B-Algorithm
stereo	I-Algorithm
vision	I-Algorithm
is	O
a	O
part	O
of	O
the	O
field	O
of	O
computer	B-Application
vision	I-Application
.	O
</s>
<s>
To	O
a	O
computer	O
this	O
represents	O
significant	O
extra	O
complexity	O
in	O
the	O
geometrical	O
calculations	O
(	O
epipolar	B-Algorithm
geometry	I-Algorithm
)	O
.	O
</s>
<s>
The	O
images	O
may	O
alternatively	O
be	O
converted	O
by	O
reprojection	O
through	O
a	O
linear	B-Architecture
transformation	I-Architecture
to	O
be	O
on	O
the	O
same	O
image	O
plane	O
.	O
</s>
<s>
This	O
is	O
called	O
image	B-Algorithm
rectification	I-Algorithm
.	O
</s>
<s>
Computer	B-Algorithm
stereo	I-Algorithm
vision	I-Algorithm
with	O
many	O
cameras	O
under	O
fixed	O
lighting	O
is	O
called	O
structure	B-Algorithm
from	I-Algorithm
motion	I-Algorithm
.	O
</s>
<s>
Techniques	O
using	O
a	O
fixed	O
camera	O
and	O
known	O
lighting	O
are	O
called	O
photometric	B-Algorithm
stereo	I-Algorithm
techniques	O
,	O
or	O
"	O
shape	B-Algorithm
from	I-Algorithm
shading	I-Algorithm
"	O
.	O
</s>
<s>
Many	O
attempts	O
have	O
been	O
made	O
to	O
reproduce	O
human	O
stereo	B-Algorithm
vision	I-Algorithm
on	O
rapidly	O
changing	O
computer	O
displays	O
,	O
and	O
toward	O
this	O
end	O
numerous	O
patents	O
relating	O
to	O
3D	B-Algorithm
television	I-Algorithm
and	O
cinema	O
have	O
been	O
filed	O
in	O
the	O
USPTO	O
.	O
</s>
<s>
Discounting	O
3D	B-Algorithm
television	I-Algorithm
and	O
cinema	O
(	O
which	O
generally	O
require	O
more	O
than	O
one	O
digital	O
projector	O
whose	O
moving	O
images	O
are	O
mechanically	O
coupled	O
,	O
in	O
the	O
case	O
of	O
IMAX	O
3D	O
cinema	O
)	O
,	O
several	O
stereoscopic	B-Algorithm
LCDs	B-Device
are	O
going	O
to	O
be	O
offered	O
by	O
Sharp	O
,	O
which	O
has	O
already	O
started	O
shipping	O
a	O
notebook	O
with	O
a	O
built	O
in	O
stereoscopic	B-Algorithm
LCD	B-Device
.	O
</s>
<s>
Although	O
older	O
technology	O
required	O
the	O
user	O
to	O
don	O
goggles	O
or	O
visors	O
for	O
viewing	O
computer-generated	O
images	O
,	O
or	O
CGI	O
,	O
newer	O
technology	O
tends	O
to	O
employ	O
Fresnel	O
lenses	O
or	O
plates	O
over	O
the	O
liquid	B-Device
crystal	I-Device
displays	I-Device
,	O
freeing	O
the	O
user	O
from	O
the	O
need	O
to	O
put	O
on	O
special	O
glasses	O
or	O
goggles	O
.	O
</s>
<s>
In	O
stereopsis	B-Algorithm
tests	O
(	O
short	O
:	O
stereotests	O
)	O
,	O
slightly	O
different	O
images	O
are	O
shown	O
to	O
each	O
eye	O
,	O
such	O
that	O
a	O
3D	B-Algorithm
image	I-Algorithm
is	O
perceived	O
in	O
case	O
stereovision	B-Algorithm
is	O
present	O
.	O
</s>
<s>
This	O
can	O
be	O
achieved	O
by	O
means	O
of	O
vectographs	B-Algorithm
(	O
visible	O
with	O
polarized	O
glasses	O
)	O
,	O
anaglyphs	B-Algorithm
(	O
visible	O
with	O
red-green	B-Algorithm
glasses	I-Algorithm
)	O
,	O
lenticular	O
lenses	O
(	O
visible	O
with	O
the	O
naked	O
eye	O
)	O
,	O
or	O
head-mounted	B-General_Concept
display	I-General_Concept
technology	O
.	O
</s>
<s>
There	O
are	O
two	O
types	O
of	O
common	O
clinical	O
tests	O
for	O
stereopsis	B-Algorithm
and	O
stereoacuity	O
:	O
random	O
dot	O
stereotests	O
and	O
contour	O
stereotests	O
.	O
</s>
<s>
Random-dot	O
stereopsis	B-Algorithm
tests	O
use	O
pictures	O
of	O
stereo	O
figures	O
that	O
are	O
embedded	O
in	O
a	O
background	O
of	O
random	O
dots	O
.	O
</s>
<s>
The	O
ability	O
of	O
stereopsis	B-Algorithm
can	O
be	O
tested	O
by	O
,	O
for	O
example	O
,	O
the	O
Lang-Stereotest	O
,	O
which	O
consists	O
of	O
a	O
random-dot	B-Algorithm
stereogram	I-Algorithm
upon	O
which	O
a	O
series	O
of	O
parallel	O
strips	O
of	O
cylindrical	O
lenses	O
are	O
imprinted	O
in	O
certain	O
shapes	O
,	O
which	O
separate	O
the	O
views	O
seen	O
by	O
each	O
eye	O
in	O
these	O
areas	O
,	O
similarly	O
to	O
a	O
hologram	B-Algorithm
.	O
</s>
<s>
Without	O
stereopsis	B-Algorithm
,	O
the	O
image	O
looks	O
only	O
like	O
a	O
field	O
of	O
random	O
dots	O
,	O
but	O
the	O
shapes	O
become	O
discernible	O
with	O
increasing	O
stereopsis	B-Algorithm
,	O
and	O
generally	O
consists	O
of	O
a	O
cat	O
(	O
indicating	O
that	O
there	O
is	O
ability	O
of	O
stereopsis	B-Algorithm
of	O
1200	O
seconds	O
of	O
arc	O
of	O
retinal	B-Algorithm
disparity	I-Algorithm
)	O
,	O
a	O
star	O
(	O
600	O
seconds	O
of	O
arc	O
)	O
and	O
a	O
car	O
(	O
550	O
seconds	O
of	O
arc	O
)	O
.	O
</s>
<s>
with	O
polarized	O
or	O
red-green	B-Algorithm
glasses	I-Algorithm
)	O
,	O
the	O
Lang-Stereotest	O
works	O
without	O
the	O
use	O
special	O
spectacles	O
,	O
thereby	O
facilitating	O
the	O
use	O
in	O
young	O
children	O
.	O
</s>
<s>
Deficiency	O
in	O
stereopsis	B-Algorithm
can	O
be	O
complete	O
(	O
then	O
called	O
stereoblindness	B-Algorithm
)	O
or	O
more	O
or	O
less	O
impaired	O
.	O
</s>
<s>
Vision	O
therapy	O
is	O
one	O
of	O
the	O
treatments	O
for	O
people	O
lacking	O
in	O
stereopsis	B-Algorithm
.	O
</s>
<s>
There	O
is	O
good	O
evidence	O
for	O
stereopsis	B-Algorithm
throughout	O
the	O
animal	O
kingdom	O
.	O
</s>
<s>
Stomatopods	O
even	O
have	O
stereopsis	B-Algorithm
with	O
just	O
one	O
eye	O
.	O
</s>
