
196 OPTICS FOR ENGINEERS
where
z is the distance from the laser radar to the target
z
0
accounts for distance differences within the interferometer
The factor of 2 multiplying z accounts for the round trip to and from the target.
7.2.2 Mixing Efficiency
The mixing power detected is
P
mix
=
I
mix
dA =
E
Sig
(
x
d
, y
d
)
E
∗
LO
(
x
d
, y
d
)
Z
dA, (7.56)
where x
d
and y
d
are coordinates in the detector. If the signal eld E
sig
(
x
d
, y
d
)
is proportional
to the local oscillator E
LO
(
x
d
, y
d
)
, then we can show that the integral becomes
P
mix
=
P
sig
P
LO
Maximum mixing power. (7.57)
If the proportionality relationship between the elds differs in any way, the result will be
smaller. For example, ...