<s>
Screenless	B-General_Concept
video	I-General_Concept
is	O
any	O
system	O
for	O
transmitting	O
visual	O
information	O
from	O
a	O
video	O
source	O
without	O
the	O
use	O
of	O
a	O
screen	B-Device
.	O
</s>
<s>
Screenless	B-General_Concept
computing	O
systems	O
can	O
be	O
divided	O
into	O
three	O
groups	O
:	O
Visual	O
Image	O
,	O
Retinal	O
Direct	O
,	O
and	O
Synaptic	O
Interface	O
.	O
</s>
<s>
Visual	O
Image	O
screenless	B-General_Concept
display	O
includes	O
any	O
image	O
that	O
the	O
eye	O
can	O
perceive	O
.	O
</s>
<s>
The	O
most	O
common	O
example	O
of	O
Visual	O
Image	O
screenless	B-General_Concept
display	O
is	O
a	O
hologram	B-Algorithm
.	O
</s>
<s>
In	O
these	O
cases	O
,	O
light	O
is	O
reflected	O
off	O
some	O
intermediate	O
object	O
(	O
hologram	B-Algorithm
,	O
LCD	O
panel	O
,	O
or	O
cockpit	O
window	O
)	O
before	O
it	O
reaches	O
the	O
retina	O
.	O
</s>
<s>
Google	O
has	O
proposed	O
a	O
similar	O
system	O
to	O
replace	O
the	O
screens	O
of	O
tablet	B-Device
computers	I-Device
and	O
smartphones	B-Application
.	O
</s>
<s>
Virtual	B-General_Concept
retinal	I-General_Concept
display	I-General_Concept
systems	O
are	O
a	O
class	O
of	O
screenless	B-General_Concept
displays	O
in	O
which	O
images	O
are	O
projected	O
directly	O
onto	O
the	O
retina	O
.	O
</s>
<s>
Retinal	O
Direct	O
systems	O
,	O
once	O
marketed	O
,	O
hold	O
out	O
the	O
promise	O
of	O
extreme	O
privacy	O
when	O
computing	O
work	O
is	O
done	O
in	O
public	O
places	O
because	O
most	O
snooping	O
relies	O
on	O
viewing	O
the	O
same	O
light	O
as	O
the	O
person	O
who	O
is	O
legitimately	O
viewing	O
the	O
screen	B-Device
,	O
and	O
retinal	O
direct	O
systems	O
send	O
light	O
only	O
into	O
the	O
pupils	O
of	O
their	O
intended	O
viewer	O
.	O
</s>
<s>
Synaptic	O
Interface	O
screenless	B-General_Concept
video	I-General_Concept
does	O
not	O
use	O
light	O
at	O
all	O
.	O
</s>
<s>
Visual	O
information	O
completely	O
bypasses	O
the	O
eye	O
and	O
is	O
transmitted	O
directly	B-Application
to	I-Application
the	I-Application
brain	I-Application
.	O
</s>
