i cation
across
sev
eral
meters BFB
Another
t
yp
e
of
triangulation
range nder
is
one
that
uses
t
w
o
inciden
t
b
eams
at
a
xed
angle
The
distance
b
et
w
een
the
t
w
o
b
eams
imaged
is
th
us
a
function
of
range
This
system
is
also
nonlinear
and
has
the
additional
problem
of
not
b
eing
able
to
b
e
scanned
planarly
This
system
is
often
used
for
surface
imaging
on
a
v
ery
small
scale Rea
The
third
t
yp
e
of
triangulation
system
uses
t
w
o
scanners
and
indep
enden
tly
calculates
the
angle
of
an
ob
ject
relativ
e
to
eac
h
scanner
purely
determining
its
x y
p
osition
A
w
ell
kno
wn
example
of
the
system
is
the
SoftBoard
b
y
Micro eld
Graphics Egl
See
Fig
This
system
incorp
orates
the
t
w
o
displaced
laser
scanners
atop
a
white
b
oard
eac
h
of
whic
h
only
measures
angle
A
user
is
required
to
write
with
sp
ecial
p
ens
iden
ti ed
b
y
a
barco
ded
retro
re ector
on
the
tip
This
system
is
only
used
to
trac
k
a
single
ob
ject
due
to
the
requiremen
t
of
the
dual
scanners
These
t
yp
es
of
range nders
w
ork
w
ell
in
this
appli
cation
but
are
clearly
not
the
b
est
solution
for
a
free gesture
m
ulti hand
bare hand
input
device
o
v
er
a
large
surface
Time of Fligh
t
Time of igh
t
laser
range nders Rea
rely
on
a
simple
principle
They
function
b
y
measuring
the
time
that
a
pulse
of
laser
ligh
t
tak
es
to
eminate
out
re ect
o
a
target
and
return
to
a
reciev
er
on
the
range nder
This
measuremen
t
is
linear
with
distance
impro
ving
on
triangulation
tec
hniques
This
system
emplo
ys
the
least
analog
hardw
are
only
requiring
a
pulse
generator
and
a
simple
high gain
reciev
er
Since
one
only
requires
a
logic lev
el
signal
from
the
returning
w
a
v
efron
t
a
simple
fast
ampli er
circuit
can
b
e
used
The
system
relies
on
a
high
sp
eed
time to digital
con
v
erter TDC Gen
p
oten
tially
a
just
a
fast
coun
ter
and
a
fast
photo
dio
de
to
main
tain
the
timing
information
Since
this
metho
d
isn t
b
ound
b
y
distance
it
is
easily
scaled
for
v
arying
ranges
Man
y
metho
ds
emplo
y
dual
phase lo
c
k
ed
clo
c
ks
for
v
arying
lev
els
of
accuracy BS
These
range nders
are
the
t
yp
e
that
are
most
often
used
on
military
aircraft
and
v
ehicles
Theoretically
they
could
b
e
scaled
easily
and
used
most
e ectiv
ely
since
they
are
digital
in
man
y
asp
ects
There
are
v
ariations
on
the
time of igh
t
range nder
that
measure
frequency