Digital Signal Processing Reference
In-Depth Information
Fig. 6.
Energy scattering during the energy accumulation
DP algorithm enables dim-small moving target to be prominence with the energy
integrated along the optimal trajectory, which guarantees the enhancement of SNR,
but meanwhile inevitably introduces the problem of energy scattering. That is, the
target is much lighter with the energy increased, but looks larger at the same time for
the energy of neighborhood pixels also may be accumulated, shown in figure 6.
Dim-small targets can be considered as doing uniform rectilinear motion in a short
period of time because IR image sequence is taken from long-distance. It is suggested
that the energy and forward moving direction of dim IR target are relative stable and
consecutive for frames but not of the Gauss noise, for which its distribution and
movement are randomly. In this case, we find a way
[7] to avoid the problem of ener-
γ
gy scattering. That is, introduce an energy gradient threshold
and a move transi-
E
γ
tion threshold
to bind the energy accumulation. The followed formulas show
d
these constraints.
Z
−
Z
(
X
)
(9)
′
E
k
exp(
)
≤
γ
k
=
1
,...
N
E
Z
(
X
)
k
E
(
X
,
k
−
1
k
=
1
,...
N
Z
=
max
k
−
1
Where
′
E
k
−
1
d
(10)
(
k
,
k
−
1
exp(
−
)
≤
γ
k
=
1
,...
N
d
180
d
X
Here
is the transition angle of pixel
moved from the
(k-1)
th frame
(
k
,
k
−
1
k
−
1
to
k
th frame, defined as
{
d
(
X
,
X
)
−
d
(
X
,
X
)
d
(
X
,
X
)
−
d
(
X
,
X
)
≤
180
°
(11)
d
=
k
k
−
1
k
−
1
k
−
2
k
k
−
1
k
−
1
k
−
2
(
k
,
k
−
1
360
°
d
(
X
,
X
)
−
d
(
X
,
X
)
360
−
d
(
X
,
X
)
−
d
(
X
,
X
)
≥
180
°
k
k
−
1
k
−
1
k
−
2
k
k
−
1
k
−
1
k
−
2
