<s>
A	O
parallax	B-Algorithm
barrier	I-Algorithm
is	O
a	O
device	O
placed	O
in	O
front	O
of	O
an	O
image	O
source	O
,	O
such	O
as	O
a	O
liquid	B-Device
crystal	I-Device
display	I-Device
,	O
to	O
allow	O
it	O
to	O
show	O
a	O
stereoscopic	B-Algorithm
or	O
multiscopic	B-General_Concept
image	O
without	O
the	O
need	O
for	O
the	O
viewer	O
to	O
wear	O
3D	O
glasses	O
.	O
</s>
<s>
Placed	O
in	O
front	O
of	O
the	O
normal	O
LCD	B-Device
,	O
it	O
consists	O
of	O
an	O
opaque	O
layer	O
with	O
a	O
series	O
of	O
precisely	O
spaced	O
slits	O
,	O
allowing	O
each	O
eye	O
to	O
see	O
a	O
different	O
set	O
of	O
pixels	B-Algorithm
,	O
so	O
creating	O
a	O
sense	O
of	O
depth	O
through	O
parallax	B-Device
in	O
an	O
effect	O
similar	O
to	O
what	O
lenticular	O
printing	O
produces	O
for	O
printed	O
products	O
and	O
lenticular	O
lenses	O
for	O
other	O
displays	O
.	O
</s>
<s>
However	O
,	O
recent	O
versions	O
of	O
this	O
technology	O
have	O
addressed	O
this	O
issue	O
by	O
using	O
face-tracking	O
to	O
adjust	O
the	O
relative	O
positions	O
of	O
the	O
pixels	B-Algorithm
and	O
barrier	O
slits	O
according	O
to	O
the	O
location	O
of	O
the	O
user	O
's	O
eyes	O
,	O
allowing	O
the	O
user	O
to	O
experience	O
the	O
3D	O
from	O
a	O
wide	O
range	O
of	O
positions	O
.	O
</s>
<s>
Another	O
disadvantage	O
is	O
that	O
the	O
horizontal	O
pixel	B-Algorithm
count	O
viewable	O
by	O
each	O
eye	O
is	O
halved	O
,	O
reducing	O
the	O
overall	O
horizontal	O
resolution	O
of	O
the	O
image	O
.	O
</s>
<s>
The	O
principle	O
of	O
the	O
parallax	B-Algorithm
barrier	I-Algorithm
was	O
independently	O
invented	O
by	O
Auguste	O
Berthier	O
,	O
who	O
published	O
an	O
article	O
on	O
stereoscopic	B-Algorithm
pictures	O
including	O
his	O
new	O
idea	O
illustrated	O
with	O
a	O
diagram	O
and	O
pictures	O
with	O
purposely	O
exaggerated	O
dimensions	O
of	O
the	O
interlaced	O
image	O
strips	O
,	O
and	O
by	O
Frederic	O
E	O
.	O
Ives	O
,	O
who	O
made	O
and	O
exhibited	O
a	O
functional	O
autostereoscopic	B-Algorithm
image	O
in	O
1901	O
.	O
</s>
<s>
In	O
the	O
early	O
2000s	O
,	O
Sharp	O
developed	O
the	O
electronic	O
flat-panel	O
application	O
of	O
this	O
old	O
technology	O
to	O
commercialization	O
,	O
briefly	O
selling	O
two	O
laptops	O
with	O
the	O
world	O
's	O
only	O
3D	O
LCD	B-Device
screens	I-Device
.	O
</s>
<s>
In	O
2009	O
,	O
Fujifilm	O
released	O
the	O
Fujifilm	B-Algorithm
FinePix	I-Algorithm
Real	I-Algorithm
3D	I-Algorithm
W1	I-Algorithm
digital	O
camera	O
,	O
which	O
features	O
a	O
built-in	O
autostereoscopic	B-Algorithm
LCD	B-Device
measuring	O
2.8	O
"	O
diagonal	O
.	O
</s>
<s>
Nintendo	O
has	O
also	O
implemented	O
this	O
technology	O
on	O
its	O
portable	O
gaming	O
consoles	O
,	O
the	O
New	B-Device
Nintendo	I-Device
3DS	I-Device
and	O
the	O
New	B-Device
Nintendo	I-Device
3DS	I-Device
XL	I-Device
,	O
after	O
first	O
including	O
it	O
on	O
the	O
previous	O
console	O
,	O
the	O
Nintendo	B-Operating_System
3DS	I-Operating_System
.	O
</s>
<s>
It	O
is	O
also	O
used	O
in	O
the	O
Nintendo	B-Operating_System
3DS	I-Operating_System
hand-held	O
game	O
console	O
and	O
LG	O
's	O
Optimus	B-Application
3D	I-Application
and	O
Thrill	O
smartphones	O
,	O
HTC	O
's	O
EVO	B-Application
3D	I-Application
as	O
well	O
as	O
Sharp	O
's	O
Galapagos	O
smartphone	O
series	O
.	O
</s>
<s>
A	O
Toshiba	O
21-inch	O
3D	B-Algorithm
display	I-Algorithm
uses	O
parallax	B-Algorithm
barrier	I-Algorithm
technology	O
with	O
9	O
pairs	O
of	O
images	O
,	O
to	O
cover	O
a	O
viewing	O
angle	O
of	O
30	O
degrees	O
.	O
</s>
<s>
The	O
slits	O
in	O
the	O
parallax	B-Algorithm
barrier	I-Algorithm
allow	O
the	O
viewer	O
to	O
see	O
only	O
left	O
image	O
pixels	B-Algorithm
from	O
the	O
position	O
of	O
their	O
left	O
eye	O
,	O
right	O
image	O
pixels	B-Algorithm
from	O
the	O
right	O
eye	O
.	O
</s>
<s>
When	O
choosing	O
the	O
geometry	O
of	O
the	O
parallax	B-Algorithm
barrier	I-Algorithm
the	O
important	O
parameters	O
that	O
need	O
to	O
be	O
optimised	O
are	O
;	O
the	O
pixel	B-Algorithm
–	O
barrier	O
separation	O
d	O
,	O
the	O
parallax	B-Algorithm
barrier	I-Algorithm
pitch	O
f	O
,	O
the	O
pixel	B-Algorithm
aperture	O
a	O
,	O
and	O
the	O
parallax	B-Algorithm
barrier	I-Algorithm
slit	O
width	O
b	O
.	O
</s>
<s>
The	O
closer	O
the	O
parallax	B-Algorithm
barrier	I-Algorithm
is	O
to	O
the	O
pixels	B-Algorithm
,	O
the	O
wider	O
the	O
angle	O
of	O
separation	O
between	O
the	O
left	O
and	O
right	O
images	O
.	O
</s>
<s>
For	O
a	O
stereoscopic	B-Algorithm
display	O
the	O
left	O
and	O
right	O
images	O
must	O
hit	O
the	O
left	O
and	O
right	O
eyes	O
,	O
which	O
means	O
the	O
views	O
must	O
be	O
separated	O
by	O
only	O
a	O
few	O
degrees	O
.	O
</s>
<s>
The	O
pixel	B-Algorithm
-	O
barrier	O
separation	O
d	O
for	O
this	O
case	O
can	O
be	O
derived	O
as	O
follows	O
.	O
</s>
<s>
For	O
a	O
typical	O
auto-stereoscopic	O
display	O
of	O
pixel	B-Algorithm
pitch	O
65	O
micrometers	O
,	O
eye	O
separation	O
63mm	O
,	O
viewing	O
distance	O
30cm	O
,	O
and	O
refractive	O
index	O
1.52	O
,	O
the	O
pixel-barrier	O
separation	O
needs	O
to	O
be	O
about	O
470	O
micrometers	O
.	O
</s>
<s>
The	O
pitch	O
of	O
a	O
parallax	B-Algorithm
barrier	I-Algorithm
should	O
ideally	O
be	O
roughly	O
two	O
times	O
the	O
pitch	O
of	O
the	O
pixels	B-Algorithm
,	O
but	O
the	O
optimum	O
design	O
should	O
be	O
slightly	O
less	O
than	O
this	O
.	O
</s>
<s>
In	O
a	O
parallax	B-Algorithm
barrier	I-Algorithm
system	O
for	O
a	O
high-resolution	O
display	O
,	O
the	O
performance	O
(	O
brightness	O
and	O
crosstalk	O
)	O
can	O
be	O
simulated	O
by	O
Fresnel	O
diffraction	O
theory	O
.	O
</s>
<s>
Note	O
that	O
the	O
parallax	B-Algorithm
barrier	I-Algorithm
may	O
also	O
be	O
placed	O
behind	O
the	O
LCD	B-Device
pixels	B-Algorithm
.	O
</s>
<s>
In	O
this	O
case	O
,	O
light	O
from	O
a	O
slit	O
passes	O
the	O
left	O
image	O
pixel	B-Algorithm
in	O
the	O
left	O
direction	O
,	O
and	O
vice	O
versa	O
.	O
</s>
<s>
This	O
produces	O
the	O
same	O
basic	O
effect	O
as	O
a	O
front	O
parallax	B-Algorithm
barrier	I-Algorithm
.	O
</s>
<s>
In	O
a	O
parallax	B-Algorithm
barrier	I-Algorithm
system	O
,	O
the	O
left	O
eye	O
sees	O
only	O
half	O
the	O
pixels	B-Algorithm
(	O
that	O
is	O
to	O
say	O
the	O
left	O
image	O
pixels	B-Algorithm
)	O
and	O
the	O
same	O
is	O
true	O
for	O
the	O
right	O
eye	O
.	O
</s>
<s>
Therefore	O
,	O
the	O
resolution	O
of	O
the	O
display	O
is	O
reduced	O
,	O
and	O
so	O
it	O
can	O
be	O
advantageous	O
to	O
make	O
a	O
parallax	B-Algorithm
barrier	I-Algorithm
that	O
can	O
be	O
switched	O
on	O
when	O
3D	O
is	O
needed	O
or	O
off	O
when	O
a	O
2D	O
image	O
is	O
required	O
.	O
</s>
<s>
One	O
method	O
of	O
switching	O
the	O
parallax	B-Algorithm
barrier	I-Algorithm
on	O
and	O
off	O
is	O
to	O
form	O
it	O
from	O
a	O
liquid	B-Device
crystal	I-Device
material	O
,	O
the	O
parallax	B-Algorithm
barrier	I-Algorithm
can	O
then	O
be	O
created	O
similar	O
to	O
the	O
way	O
that	O
an	O
image	O
is	O
formed	O
in	O
a	O
liquid	B-Device
crystal	I-Device
display	I-Device
.	O
</s>
<s>
Time	O
multiplexing	O
provides	O
a	O
means	O
of	O
increasing	O
the	O
resolution	O
of	O
a	O
parallax	B-Algorithm
barrier	I-Algorithm
system	O
.	O
</s>
<s>
In	O
a	O
standard	O
parallax	B-Algorithm
barrier	I-Algorithm
system	O
,	O
the	O
viewer	O
must	O
position	O
themselves	O
in	O
an	O
appropriate	O
location	O
so	O
that	O
the	O
left	O
and	O
right	O
eye	O
views	O
can	O
be	O
seen	O
by	O
their	O
left	O
and	O
right	O
eyes	O
respectively	O
.	O
</s>
<s>
In	O
a	O
‘	O
tracked	O
3D	O
system’	O
,	O
the	O
viewing	O
freedom	O
can	O
be	O
increased	O
considerably	O
by	O
tracking	O
the	O
position	O
of	O
the	O
user	O
and	O
adjusting	O
the	O
parallax	B-Algorithm
barrier	I-Algorithm
so	O
that	O
the	O
left	O
and	O
right	O
views	O
are	O
always	O
directed	O
to	O
the	O
user	O
's	O
eyes	O
correctly	O
.	O
</s>
<s>
Adjustment	O
of	O
the	O
angle	O
at	O
which	O
the	O
left	O
and	O
right	O
views	O
are	O
projected	O
can	O
be	O
done	O
by	O
mechanically	O
or	O
electronically	O
shifting	O
the	O
parallax	B-Algorithm
barrier	I-Algorithm
relative	O
to	O
the	O
pixels	B-Algorithm
.	O
</s>
<s>
Crosstalk	O
is	O
the	O
interference	O
that	O
exists	O
between	O
the	O
left	O
and	O
right	O
views	O
in	O
a	O
3D	B-Algorithm
display	I-Algorithm
.	O
</s>
<s>
The	O
perception	O
of	O
crosstalk	O
in	O
stereoscopic	B-Algorithm
displays	O
has	O
been	O
studied	O
widely	O
.	O
</s>
<s>
It	O
is	O
generally	O
acknowledged	O
that	O
the	O
presence	O
of	O
high	O
levels	O
of	O
crosstalk	O
in	O
a	O
stereoscopic	B-Algorithm
display	O
is	O
detrimental	O
.	O
</s>
<s>
The	O
visibility	O
of	O
crosstalk	O
(	O
ghosting	O
)	O
increases	O
with	O
increasing	O
contrast	O
and	O
increasing	O
binocular	O
parallax	B-Device
of	O
the	O
image	O
.	O
</s>
<s>
For	O
example	O
,	O
a	O
stereoscopic	B-Algorithm
image	O
with	O
high	O
contrast	O
will	O
exhibit	O
more	O
ghosting	O
on	O
a	O
particular	O
stereoscopic	B-Algorithm
display	O
than	O
will	O
an	O
image	O
with	O
low	O
contrast	O
.	O
</s>
<s>
A	O
technique	O
to	O
quantify	O
the	O
level	O
of	O
crosstalk	O
from	O
a	O
3D	B-Algorithm
display	I-Algorithm
involves	O
measuring	O
the	O
percentage	O
of	O
light	O
that	O
deviates	O
from	O
one	O
view	O
to	O
the	O
other	O
.	O
</s>
<s>
The	O
crosstalk	O
in	O
a	O
typical	O
parallax-barrier-based	O
3D	O
system	O
at	O
the	O
best	O
eye	O
position	O
might	O
be	O
3%	O
.	O
</s>
<s>
Theoretical	O
simulations	O
of	O
diffraction	O
have	O
been	O
found	O
to	O
be	O
a	O
good	O
predictor	O
of	O
experimental	O
crosstalk	O
measurements	O
in	O
emulsion	O
parallax	B-Algorithm
barrier	I-Algorithm
systems	O
.	O
</s>
<s>
These	O
simulations	O
predict	O
that	O
the	O
amount	O
of	O
crosstalk	O
caused	O
by	O
the	O
parallax	B-Algorithm
barrier	I-Algorithm
will	O
be	O
highly	O
dependent	O
on	O
the	O
sharpness	O
of	O
the	O
edges	O
of	O
the	O
slits	O
.	O
</s>
<s>
The	O
diffraction	O
simulations	O
also	O
suggest	O
that	O
if	O
the	O
parallax	B-Algorithm
barrier	I-Algorithm
slit	O
edges	O
had	O
a	O
transmission	O
that	O
decreases	O
over	O
a	O
10	O
micrometers	O
region	O
,	O
then	O
crosstalk	O
could	O
become	O
as	O
0.1	O
.	O
</s>
<s>
There	O
are	O
three	O
main	O
types	O
of	O
autostereoscopic	B-Algorithm
displays	I-Algorithm
with	O
a	O
parallax	B-Algorithm
barrier	I-Algorithm
:	O
</s>
<s>
Early	O
experimental	O
prototypes	O
that	O
simply	O
put	O
a	O
series	O
of	O
precision	O
slits	O
on	O
a	O
regular	O
LCD	B-Device
screen	I-Device
to	O
see	O
if	O
it	O
had	O
any	O
potential	O
.	O
</s>
<s>
The	O
first	O
fully	O
developed	O
"	O
Parallax	B-Algorithm
barrier	I-Algorithm
displays	O
"	O
have	O
precision	O
slits	O
as	O
one	O
of	O
the	O
optical	O
components	O
over	O
the	O
pixels	B-Algorithm
.	O
</s>
<s>
The	O
newest	O
and	O
most	O
convenient	O
displays	O
,	O
in	O
products	O
such	O
as	O
the	O
Nintendo	B-Operating_System
3DS	I-Operating_System
,	O
HTC	B-Application
Evo	I-Application
3D	I-Application
,	O
and	O
LG	B-Application
Optimus	I-Application
3D	I-Application
,	O
do	O
not	O
have	O
the	O
parallax	B-Algorithm
barrier	I-Algorithm
in	O
front	O
of	O
the	O
pixels	B-Algorithm
,	O
but	O
behind	O
the	O
pixels	B-Algorithm
and	O
in	O
front	O
of	O
the	O
backlight	O
.	O
</s>
<s>
The	O
entire	O
LCD	B-Device
matrix	O
is	O
therefore	O
exposed	O
to	O
both	O
eyes	O
,	O
but	O
as	O
seen	O
from	O
each	O
eye	O
's	O
position	O
only	O
one	O
of	O
the	O
interlaced	O
images	O
in	O
it	O
is	O
backlit	O
.	O
</s>
<s>
Glare	O
from	O
the	O
visibly	O
lit	O
pixel	B-Algorithm
columns	O
tends	O
to	O
make	O
the	O
adjacent	O
unlit	O
columns	O
less	O
noticeable	O
.	O
</s>
