<s>
A	O
fog	B-General_Concept
display	I-General_Concept
,	O
fog	O
screen	O
,	O
vapor	O
screen	O
or	O
vapor	O
display	O
is	O
a	O
system	O
that	O
uses	O
haze	O
machines	O
or	O
water	O
vapor	O
to	O
create	O
a	O
semi-transparent	O
wall	O
,	O
or	O
"	O
curtain	O
"	O
of	O
suspended	O
particles	O
which	O
trapped	O
in	O
a	O
thin	O
sheet	O
(	O
laminar	O
flow	O
)	O
of	O
air	O
and	O
are	O
illuminated	O
by	O
a	O
projector	B-Application
,	O
in	O
order	O
to	O
produce	O
a	O
display	O
whose	O
images	O
seem	O
to	O
float	O
in	O
mid	O
air	O
.	O
</s>
<s>
Several	O
commercial	O
systems	O
exist	O
,	O
such	O
as	O
FogScreen	O
,	O
Displair	O
and	O
Heliodisplay	B-General_Concept
.	O
</s>
<s>
This	O
system	O
can	O
be	O
expanded	O
using	O
multiple	O
projectors	O
to	O
create	O
a	O
three-dimensional	O
image	O
,	O
thus	O
becoming	O
a	O
volumetric	B-Algorithm
3D	I-Algorithm
display	I-Algorithm
.	O
</s>
