Receiver Sensors
Video
Projector
Performer
Rear Projection Screen
Transmit Antenna
Calibrator
Sensor
Figure
Gesture
W
all
Setup
Sensing
has
b
een
used
to
trac
k
gesture
in
one
of
The
Br
ain
Op
er
a s
installations
measuring
the
b
o
dy s
motion
in
fron
t
of
pro
jection
screen SWD
This
installa
tion
w
as
called
the
Gestur
e
Wal
l
Fig
Here
as
in
Fig
the
user s
b
o
dy
w
as
driv
en
b
y
a
w
eak
electric
eld
coupled
in
through
the
o
or
a
set
of
receiv
e
electro
des
w
ere
placed
at
the
edge
of
the
displa
y
p
erimeter
measuring
the
b
o
dy s
distance
via
capacitiv
e
coupling
The
arc
hitecture
of
this
system
ho
w
ev
er
didn t
pro
vide
the
abilit
y
to
trac
k
rep
eatably
The
am
biguit
y
as
to
what
part
of
the
b
o
dy
the
system
w
as
trac
king
put
undue
constrain
ts
on
the
b
o
dy s
p
osition
and
p
osture
Other
approac
hes
ha
v
e
used
video
systems W
re
Computer
vision
researc
h
seeks
to
solv
e
some
of
the
same
problems
but
requires
large
pro
cessing
on
the
part
of
the
host
computer
The
p
erformance
o
v
erhead
is
considerable
and
these
systems
generally
tend
to
b
e
v
ery
sensitiv
e
to
bac
kground
ligh
t
and
clutter
often
relying
on
high
con
trast
of
a
p
erson s
image
They
also
can
require
exp
ensiv
e
computers
to
implemen
t
the
trac
king
algorithms
in
real
time
They
often
try
to
correct
for
man
y