<s>
The	O
viewing	B-Device
cone	I-Device
refers	O
to	O
the	O
effective	O
viewing	B-Device
directions	I-Device
of	O
an	O
LCD	B-Device
display	I-Device
,	O
as	O
seen	O
from	O
the	O
eye	O
.	O
</s>
<s>
The	O
concept	O
has	O
been	O
introduced	O
as	O
an	O
international	O
standard	O
ISO	B-General_Concept
13406-2	I-General_Concept
,	O
which	O
defines	O
it	O
as	O
the	O
range	O
of	O
viewing	B-Device
directions	I-Device
that	O
can	O
safely	O
be	O
used	O
for	O
the	O
intended	O
task	O
without	O
"	O
reduced	O
visual	O
performance	O
"	O
.	O
</s>
<s>
This	O
standard	O
describes	O
a	O
complex	O
procedure	O
which	O
evaluates	O
the	O
viewing	B-Device
cone	I-Device
from	O
measurements	O
of	O
luminance	O
and	O
chromaticity	O
versus	O
direction	O
of	O
observation	O
.	O
</s>
<s>
ISO	B-General_Concept
13406-2	I-General_Concept
introduces	O
4	O
viewing	B-Device
direction	I-Device
range	O
classes	O
,	O
from	O
a	O
wide	O
viewing	B-Device
cone	I-Device
,	O
for	O
many	O
simultaneous	O
observers	O
,	O
to	O
the	O
so-called	O
"	O
privacy	O
display	B-Device
"	O
,	O
with	O
a	O
severely	O
limited	O
viewing	B-Device
cone	I-Device
.	O
</s>
<s>
Compliance	O
routes	O
for	O
different	O
display	B-Device
applications	O
can	O
now	O
be	O
found	O
in	O
the	O
successor	O
standard	O
ISO	O
9241-300	O
.	O
</s>
<s>
When	O
a	O
visual	O
display	B-Device
with	O
non-vanishing	O
size	O
is	O
seen	O
by	O
an	O
observer	O
,	O
every	O
point	O
of	O
the	O
display	B-Device
area	O
is	O
seen	O
from	O
a	O
different	O
direction	O
as	O
illustrated	O
in	O
fig	O
.	O
</s>
<s>
No	O
two	O
spots	O
on	O
the	O
display	B-Device
are	O
seen	O
from	O
the	O
same	O
direction	O
.	O
</s>
<s>
The	O
larger	O
the	O
display	B-Device
is	O
and	O
the	O
closer	O
the	O
observer	O
is	O
to	O
the	O
display	B-Device
the	O
more	O
the	O
viewing	B-Device
direction	I-Device
varies	O
over	O
the	O
surface	O
area	O
of	O
the	O
display	B-Device
.	O
</s>
<s>
Colloquially	O
,	O
the	O
viewing	B-Device
direction	I-Device
is	O
often	O
called	O
"	O
viewing	B-General_Concept
angle	I-General_Concept
"	O
.	O
</s>
<s>
This	O
is	O
an	O
ill-chosen	O
expression	O
which	O
should	O
be	O
avoided	O
,	O
because	O
the	O
viewing	B-Device
direction	I-Device
is	O
specified	O
by	O
two	O
polar	O
angles	O
:	O
the	O
angle	O
of	O
inclination	O
,	O
θ	O
(	O
measured	O
from	O
the	O
surface	O
normal	O
of	O
the	O
display	B-Device
)	O
and	O
the	O
azimuth	O
angle	O
,	O
Φ	O
,	O
measured	O
in	O
the	O
plane	O
of	O
the	O
display	B-Device
as	O
shown	O
in	O
figure	O
3	O
.	O
</s>
<s>
2	O
,	O
the	O
eyeball	O
represents	O
the	O
observer	O
that	O
is	O
looking	O
at	O
a	O
specific	O
spot	O
on	O
the	O
display	B-Device
which	O
is	O
identical	O
to	O
the	O
origin	O
of	O
the	O
polar	O
coordinate	O
system	O
.	O
</s>
<s>
The	O
green	O
arrow	O
is	O
the	O
viewing	B-Device
direction	I-Device
(	O
i.e.	O
</s>
<s>
The	O
viewing	B-Device
direction	I-Device
is	O
specified	O
by	O
the	O
angle	O
of	O
inclination	O
,	O
θ	O
,	O
measured	O
from	O
the	O
surface	O
normal	O
of	O
the	O
display	B-Device
(	O
blue	O
vertical	O
arrow	O
)	O
while	O
the	O
azimuth	O
angle	O
,	O
Φ	O
,	O
is	O
the	O
angle	O
that	O
the	O
projection	O
of	O
the	O
viewing	B-Device
direction	I-Device
onto	O
the	O
surface	O
of	O
the	O
display	B-Device
makes	O
with	O
the	O
x-axis	O
(	O
red	O
arrow	O
)	O
.	O
</s>
<s>
The	O
projection	O
of	O
the	O
viewing	B-Device
direction	I-Device
is	O
shown	O
here	O
as	O
the	O
shadow	O
of	O
the	O
green	O
arrow	O
.	O
</s>
<s>
The	O
multitude	O
of	O
directions	O
,	O
from	O
which	O
a	O
display	B-Device
can	O
be	O
seen	O
without	O
artifacts	O
and	O
distortions	O
that	O
would	O
render	O
its	O
intended	O
use	O
impossible	O
(	O
e.g.	O
</s>
<s>
computerized	O
office	O
work	O
,	O
television	O
,	O
entertainment	O
)	O
is	O
called	O
the	O
viewing	B-Device
cone	I-Device
(	O
even	O
though	O
its	O
shape	O
might	O
be	O
that	O
of	O
a	O
generalized	O
cone	O
)	O
.	O
</s>
<s>
The	O
concept	O
of	O
the	O
viewing	B-Device
cone	I-Device
has	O
been	O
introduced	O
for	O
the	O
first	O
time	O
in	O
the	O
international	O
standard	O
ISO	O
13406-2:2001	O
"	O
Ergonomic	O
requirements	O
for	O
work	O
with	O
visual	O
displays	O
based	O
on	O
flat	O
panels	O
–	O
Part	O
2	O
:	O
Ergonomic	O
requirements	O
for	O
flat	O
panel	O
displays	O
"	O
.	O
</s>
<s>
This	O
standard	O
provides	O
a	O
classification	O
for	O
computer	O
monitors	O
with	O
LCDs	B-Device
according	O
to	O
the	O
range	O
of	O
viewing	B-Device
directions	I-Device
that	O
can	O
safely	O
be	O
used	O
for	O
the	O
intended	O
task	O
(	O
here	O
:	O
office	O
work	O
)	O
without	O
"	O
reduced	O
visual	O
performance	O
"	O
.	O
</s>
<s>
The	O
classification	O
is	O
according	O
to	O
"	O
Viewing	B-Device
Direction	I-Device
Range	O
Classes	O
"	O
with	O
the	O
"	O
range	O
of	O
viewing	B-Device
directions	I-Device
"	O
being	O
equivalent	O
to	O
the	O
viewing	B-Device
cone	I-Device
.	O
</s>
<s>
ISO	B-General_Concept
13406-2	I-General_Concept
describes	O
a	O
complex	O
procedure	O
according	O
to	O
which	O
the	O
usable	O
viewing	B-Device
cone	I-Device
can	O
be	O
evaluated	O
from	O
measurements	O
of	O
luminance	O
and	O
chromaticity	O
versus	O
direction	O
of	O
observation	O
.	O
</s>
<s>
ISO	B-General_Concept
13406-2	I-General_Concept
introduces	O
4	O
viewing	B-Device
direction	I-Device
range	O
classes	O
of	O
which	O
the	O
first	O
(	O
class	O
I	O
)	O
is	O
a	O
wide	O
viewing	B-Device
cone	I-Device
for	O
many	O
simultaneous	O
observers	O
and	O
the	O
last	O
(	O
class	O
IV	O
)	O
is	O
a	O
so-called	O
"	O
privacy	O
display	B-Device
"	O
with	O
a	O
severely	O
limited	O
viewing	B-Device
cone	I-Device
.	O
</s>
<s>
Depending	O
on	O
the	O
actual	O
task	O
to	O
be	O
performed	O
with	O
a	O
certain	O
display	B-Device
device	I-Device
(	O
e.g.	O
</s>
<s>
the	O
requirements	O
for	O
the	O
display	B-Device
are	O
different	O
.	O
</s>
<s>
Compliance	O
routes	O
for	O
different	O
display	B-Device
applications	O
can	O
now	O
be	O
found	O
in	O
the	O
successor	O
standard	O
ISO	O
9241-300	O
.	O
</s>
<s>
Viewing	B-Device
directions	I-Device
are	O
conveniently	O
represented	O
in	O
a	O
polar	O
coordinate	O
system	O
with	O
the	O
angle	O
of	O
inclination	O
,	O
θ	O
,	O
being	O
represented	O
by	O
the	O
radial	O
distance	O
from	O
the	O
origin	O
and	O
the	O
azimuth	O
,	O
Φ	O
,	O
increasing	O
counterclockwise	O
as	O
shown	O
in	O
figure	O
4	O
.	O
</s>
<s>
In	O
this	O
coordinate	O
system	O
every	O
point	O
corresponds	O
to	O
one	O
viewing	B-Device
direction	I-Device
.	O
</s>
<s>
A	O
viewing	B-Device
cone	I-Device
is	O
thus	O
defined	O
by	O
a	O
locus	O
(	O
a	O
closed	O
line	O
)	O
in	O
this	O
coordinate	O
system	O
as	O
indicated	O
by	O
the	O
rectangle	O
and	O
the	O
ellipse	O
in	O
fig	O
.	O
</s>
<s>
If	O
a	O
viewing	B-Device
cone	I-Device
is	O
specified	O
by	O
four	O
directions	O
only	O
(	O
e.g.	O
</s>
<s>
In	O
order	O
to	O
resolve	O
this	O
ambiguity	O
,	O
the	O
viewing	B-Device
cone	I-Device
should	O
be	O
specified	O
by	O
at	O
least	O
8	O
directions	O
,	O
located	O
in	O
the	O
horizontal	O
and	O
vertical	O
plane	O
and	O
in	O
the	O
two	O
diagonal	O
planes	O
( Φ	O
=	O
45°	O
and	O
135°	O
)	O
.	O
</s>
<s>
A	O
viewing	B-Device
cone	I-Device
can	O
be	O
defined	O
starting	O
from	O
a	O
certain	O
application	O
and	O
the	O
related	O
geometry	O
of	O
observation	O
,	O
from	O
which	O
a	O
range	O
of	O
directions	O
can	O
be	O
obtained	O
that	O
specify	O
the	O
viewing	B-Device
cone	I-Device
required	O
for	O
that	O
task	O
.	O
</s>
<s>
Inside	O
this	O
viewing	B-Device
cone	I-Device
certain	O
physical	O
parameters	O
that	O
are	O
related	O
to	O
the	O
visual	O
performance	O
of	O
the	O
display	B-Device
device	I-Device
must	O
remain	O
within	O
certain	O
(	O
task	O
dependent	O
)	O
limits	O
.	O
</s>
<s>
A	O
viewing	B-Device
cone	I-Device
can	O
also	O
result	O
from	O
measurements	O
(	O
versus	O
viewing	B-Device
direction	I-Device
)	O
carried	O
out	O
with	O
a	O
certain	O
display	B-Device
device	I-Device
under	O
specified	O
operating	O
conditions	O
.	O
</s>
<s>
Then	O
the	O
viewing	B-Device
cone	I-Device
is	O
obtained	O
by	O
limiting	O
values	O
of	O
a	O
visual	O
quantity	O
(	O
e.g.	O
</s>
<s>
Then	O
the	O
line	O
for	O
which	O
the	O
contrast	O
equals	O
10	O
defines	O
the	O
viewing	B-Device
cone	I-Device
.	O
</s>
<s>
Recent	O
experiments	O
have	O
shown	O
that	O
the	O
acceptable	O
viewing	B-Device
cone	I-Device
is	O
rather	O
determined	O
by	O
decrease	O
of	O
luminance	O
and	O
change	O
of	O
chromaticity	O
than	O
by	O
the	O
decrease	O
of	O
contrast	O
.	O
</s>
<s>
Comprehensive	O
comparisons	O
between	O
experiments	O
and	O
measurements	O
have	O
been	O
carried	O
out	O
in	O
order	O
to	O
identify	O
the	O
quantities	O
and	O
the	O
corresponding	O
limiting	O
values	O
that	O
define	O
the	O
apparent	O
viewing	B-Device
cone	I-Device
for	O
television	B-Device
screens	I-Device
with	O
LCDs	B-Device
and	O
PDPs	O
.	O
</s>
<s>
Furthermore	O
,	O
"	O
not	O
only	O
the	O
chromaticity	O
coordinates	O
of	O
the	O
primaries	O
,	O
but	O
even	O
more	O
those	O
of	O
the	O
white	O
point	O
play	O
an	O
important	O
role	O
and	O
need	O
to	O
be	O
included	O
in	O
a	O
viewing	B-Device
direction	I-Device
dependent	O
metric	O
"	O
.	O
</s>
<s>
The	O
authors	O
conclude	O
that	O
"	O
for	O
LCDs	B-Device
,	O
this	O
new	O
metric	O
results	O
in	O
a	O
viewing	B-Device
cone	I-Device
,	O
which	O
is	O
on	O
the	O
order	O
of	O
70°	O
–	O
90°	O
(	O
subtended	O
angle	O
)	O
,	O
and	O
thus	O
,	O
considerably	O
lower	O
than	O
what	O
is	O
usually	O
specified	O
based	O
on	O
a	O
minimum	O
contrast	O
of	O
10	O
.	O
</s>
<s>
For	O
PDPs	O
,	O
this	O
new	O
metric	O
yields	O
the	O
same	O
viewing	B-Device
direction	I-Device
range	O
as	O
the	O
present	O
specification	O
that	O
uses	O
a	O
luminance	O
decrease	O
to	O
50%	O
"	O
.	O
</s>
<s>
In	O
the	O
terminology	O
as	O
introduced	O
above	O
(	O
and	O
illustrated	O
in	O
Figure	O
2	O
)	O
a	O
viewing	B-Device
cone	I-Device
of	O
70°	O
–	O
90°	O
subtended	O
angle	O
means	O
(	O
for	O
a	O
rotationally	O
symmetric	O
viewing	B-Device
cone	I-Device
)	O
a	O
maximum	O
angle	O
of	O
inclination	O
of	O
35°	O
-45	O
°	O
.	O
</s>
<s>
5	O
shows	O
luminance	O
and	O
contrast	O
versus	O
viewing	B-Device
direction	I-Device
in	O
a	O
polar	O
coordinate	O
system	O
.	O
</s>
<s>
The	O
left	O
column	O
shows	O
the	O
directional	O
luminance	O
distribution	O
of	O
the	O
dark	O
state	O
of	O
the	O
display	B-Device
(	O
here	O
:	O
IPS-LCD	O
)	O
,	O
the	O
center	O
column	O
shows	O
the	O
bright	O
state	O
and	O
the	O
right	O
column	O
shows	O
the	O
(	O
luminance	O
)	O
contrast	O
(	O
ratio	O
)	O
resulting	O
from	O
the	O
preceding	O
two	O
luminance	O
distributions	O
.	O
</s>
<s>
This	O
way	O
of	O
representing	O
the	O
variation	O
of	O
a	O
quantity	O
of	O
a	O
display	B-Device
with	O
direction	O
of	O
observation	O
originates	O
from	O
an	O
optical	O
technique	O
called	O
conoscopy	O
.	O
</s>
<s>
Conoscopy	O
,	O
originally	O
proposed	O
and	O
used	O
by	O
Maugin	O
for	O
examination	O
of	O
the	O
state	O
of	O
liquid	B-Device
crystal	I-Device
alignment	O
in	O
1911	O
has	O
been	O
used	O
in	O
every	O
LCD-laboratory	O
in	O
the	O
late	O
seventies	O
and	O
throughout	O
the	O
eighties	O
for	O
measurement	O
and	O
evaluation	O
of	O
the	O
optical	O
properties	O
of	O
LCDs	B-Device
and	O
for	O
estimation	O
of	O
LCD-contrast	O
as	O
a	O
function	O
of	O
viewing	B-Device
direction	I-Device
.	O
</s>
<s>
The	O
first	O
publication	O
of	O
the	O
variation	O
of	O
the	O
contrast	O
of	O
reflective	O
LCDs	B-Device
measured	O
with	O
a	O
motorized	O
mechanically	O
scanning	O
gonioscopic	O
apparatus	O
and	O
represented	O
as	O
a	O
conoscopic	O
directions	O
figure	O
was	O
published	O
in	O
1979	O
.	O
</s>
