41
12
O
PERATIONAL
R
ECOMMENDATIONS
Laser
units
operating
to
determine
speed
and
ranging
are
commonly
used
by
law
enforcement
today.
The
basic
premise
of
how
they
work
is
based
on
knowing
the
speed
of
light
through
the
atmosphere
and
a
very
high
speed
counter.
12.1
T
HEORY
OF
O
PERATION
When
you
aim
the
laser
at
a
target
and
pull
the
trigger,
the
laser
sends
out
pulses
of
light
toward
the
target
while
simultaneously
starting
a
high
precision
timer.
When
the
light
pulses
hit
the
target
they
tend
to
reflect
back
toward
the
laser
unit.
These
reflected
energy
pulses
are
captured
by
the
laser’s
optics
and
the
timer
value
is
read.
Knowing
the
time
from
shooting
the
pulses
to
capturing
their
reflections
gives
us
the
total
time
of
flight
for
the
light
pulses.
Since
the
speed
of
light
through
the
atmosphere
is
known,
we
can
calculate
the
total
distance
traveled
by
the
light
pulses.
Dividing
that
distance
in
half
will
provide
the
distance
from
the
laser
to
the
target.
Because
the
speed
of
light
is
so
much
faster
than
the
speed
the
target
could
be
moving,
the
change
in
distance
due
to
the
target’s
movement
is
negligible.
By
now
taking
successive
range
readings
for
the
same
target
and
noting
the
time
elapsed
between
readings,
we
can
implement
a
detailed
algorithm
to
calculate
the
speed
of
the
target.
Once
we
have
the
speed
and/or
range
calculated,
we
can
display
that
on
the
screen
and
in
the
HUD
for
you
to
see.
Because
the
laser
uses
very
narrow
light
pulses
to
detect
distance
and
speeds,
it
is
much
more
suitable
to
use
when
identifying
specific
targets
than
are
the
broader
beam
radar
units.
A
drawback
to
using
laser,
however,
is
that
the
user
must
be
stationary
and
holding
the
laser
still
and
aimed
directly
at
the
target.
Radar
systems
allow
the
targets
to
pass
through
their
microwave
beam
and
they
calculate
the
speeds
of
the
targets
within
the
beam.
Because
the
aiming
of
the
radar
is
much
less
constrained,
this
lends
itself
to
identifying
targets
while
not
stationary
such
as
in
moving
police
vehicles.
12.2
C
ONSIDERATIONS
FOR
U
SING
A
L
ASER
D
ETECTION
S
YSTEM
While
the
laser
system
is
indeed
a
very
powerful
measurement
instrument,
certain
considerations
should
be
taken
into
account
when
using
it
to
measure
targets.
When
aiming
the
reticle
in
the
HUD
at
a
potential
target,
you
must
not
try
to
move
the
laser
while
firing.
Trying
to
follow
the
target
with
the
laser
can
delay
getting
results.
The
Sure
Shot™
has
algorithms
in
place
that
help
to
alleviate
that
issue,
but
it
is
best
to
just
hold
the
laser
aimed
at
a
target
as
still
as
possible.
When
trying
to
measure
a
potential
target
you
should
also
try
to
aim
at
the
most
reflective
part
of
the
vehicle
–
preferably
the
front
or
rear
of
the
target
depending
on
which
side
is
facing
the
laser
when
shooting.
Higher
reflective
surfaces
maximize
the
reflected
light
energy
back
to
the
laser
optics
for
measurement.
Headlights,
reflective
license
plates
and
front
grilles
are
excellent
reflector
surfaces.
