<s>
Visuo-haptic	B-General_Concept
mixed	I-General_Concept
reality	I-General_Concept
(	O
VHMR	O
)	O
is	O
a	O
branch	O
of	O
mixed	B-General_Concept
reality	I-General_Concept
that	O
has	O
the	O
ability	O
of	O
merging	O
visual	O
and	O
tactile	O
perceptions	O
of	O
both	O
virtual	O
and	O
real	O
objects	O
with	O
a	O
collocated	O
approach	O
.	O
</s>
<s>
The	O
first	O
known	O
system	O
to	O
overlay	O
augmented	O
haptic	O
perceptions	O
on	O
direct	O
views	O
of	O
the	O
real	O
world	O
is	O
the	O
Virtual	B-General_Concept
Fixtures	I-General_Concept
system	O
developed	O
in	O
1992	O
at	O
the	O
US	O
Air	O
Force	O
Research	O
Laboratories	O
.	O
</s>
<s>
Like	O
any	O
emerging	O
technology	O
,	O
the	O
development	O
of	O
the	O
VHMR	O
systems	O
is	O
accompanied	O
by	O
challenges	O
that	O
,	O
in	O
this	O
case	O
,	O
deal	O
with	O
the	O
efforts	O
to	O
enhance	O
the	O
multi-modal	O
human	O
perception	O
with	O
the	O
user-computer	B-Application
interface	I-Application
and	O
interaction	O
devices	O
at	O
the	O
moment	O
available	O
.	O
</s>
<s>
Visuo-haptic	B-General_Concept
mixed	I-General_Concept
reality	I-General_Concept
(	O
VHMR	O
)	O
consists	O
of	O
adding	O
to	O
a	O
real	O
scene	O
the	O
ability	O
to	O
see	O
and	O
touch	O
virtual	O
objects	O
.	O
</s>
<s>
It	O
requires	O
the	O
use	O
of	O
see-through	O
display	O
technology	O
for	O
visually	O
mixing	O
real	O
and	O
virtual	O
objects	O
and	O
haptic	B-Device
devices	I-Device
necessary	O
to	O
provide	O
haptic	O
stimuli	O
to	O
the	O
user	O
while	O
interacting	O
with	O
the	O
virtual	O
objects	O
.	O
</s>
<s>
This	O
setup	O
overcomes	O
the	O
limits	O
of	O
the	O
traditional	O
one	O
,	O
i.e	O
,	O
display	O
and	O
haptic	B-Device
device	I-Device
,	O
because	O
the	O
visuo-haptic	O
co-location	O
of	O
the	O
user	O
's	O
hand	O
and	O
a	O
virtual	O
tool	O
improve	O
the	O
sensory	O
integration	O
of	O
multimodal	O
cues	O
and	O
makes	O
the	O
interaction	O
more	O
natural	O
.	O
</s>
