<s>
A	O
time	B-Algorithm
delay	I-Algorithm
and	I-Algorithm
integration	I-Algorithm
or	O
time	O
delay	O
integration	O
(	O
TDI	O
)	O
charge-coupled	B-Algorithm
device	I-Algorithm
(	O
CCD	O
)	O
is	O
an	O
image	B-Algorithm
sensor	I-Algorithm
for	O
capturing	O
images	O
of	O
moving	O
objects	O
at	O
low	O
light	O
levels	O
.	O
</s>
<s>
While	O
using	O
similar	O
underlying	O
CCD	O
technology	O
,	O
in	O
operation	O
it	O
contrasts	O
with	O
staring	B-Algorithm
arrays	I-Algorithm
and	O
line	B-Algorithm
scanned	I-Algorithm
arrays	I-Algorithm
.	O
</s>
<s>
It	O
is	O
perhaps	O
the	O
easiest	O
to	O
understand	O
TDI	O
devices	O
by	O
contrast	O
with	O
more	O
well-known	O
types	O
of	O
CCD	B-Algorithm
sensors	I-Algorithm
.	O
</s>
<s>
The	O
best	O
known	O
is	O
the	O
staring	B-Algorithm
array	I-Algorithm
one	O
.	O
</s>
<s>
In	O
a	O
staring	B-Algorithm
array	I-Algorithm
configuration	O
,	O
the	O
image	O
is	O
exposed	O
on	O
the	O
two-dimensional	O
semiconductor	O
surface	O
,	O
and	O
then	O
the	O
resulting	O
charge	O
distribution	O
over	O
each	O
line	O
of	O
the	O
image	O
is	O
moved	O
to	O
the	O
side	O
,	O
to	O
be	O
rapidly	O
and	O
sequentially	O
read	O
out	O
by	O
an	O
electronic	O
read	O
amplifier	O
.	O
</s>
<s>
When	O
done	O
fast	O
enough	O
,	O
this	O
produces	O
a	O
snapshot	O
of	O
the	O
applied	O
photonic	O
flux	B-General_Concept
over	O
the	O
sensor	O
;	O
the	O
readout	O
can	O
proceed	O
in	O
parallel	O
over	O
the	O
several	O
lines	O
,	O
and	O
yields	O
a	O
two-dimensional	O
image	O
of	O
the	O
light	O
applied	O
.	O
</s>
<s>
Along	O
with	O
CMOS	O
detectors	O
which	O
sense	O
the	O
photocharge	O
accumulation	O
pixel	B-Algorithm
by	O
pixel	B-Algorithm
instead	O
of	O
moving	O
the	O
charge	O
out	O
line	O
by	O
line	O
,	O
such	O
sensors	O
are	O
commonly	O
known	O
as	O
parts	O
of	O
digital	O
cameras	O
,	O
from	O
the	O
small	O
to	O
the	O
large	O
.	O
</s>
<s>
The	O
advantage	O
of	O
using	O
a	O
CCD	B-Algorithm
sensor	I-Algorithm
this	O
way	O
is	O
reduced	O
complexity	O
,	O
and	O
so	O
price	O
,	O
or	O
vice	O
versa	O
the	O
possibility	O
of	O
utilizing	O
much	O
more	O
refined	O
and	O
so	O
more	O
expensive	O
CCD	O
technology	O
for	O
the	O
single	O
line	O
sensor	O
array	O
,	O
for	O
higher	O
fidelity	O
.	O
</s>
<s>
Since	O
the	O
out-clocking	O
mechanism	O
of	O
a	O
well-phased	O
CCD	O
line	O
is	O
a	O
continuous	O
process	O
,	O
not	O
divided	O
to	O
pixels	B-Algorithm
,	O
the	O
eventual	O
line-wise	O
resolution	O
of	O
the	O
image	O
can	O
also	O
exceed	O
the	O
resolution	O
of	O
the	O
gating	O
infrastructure	O
,	O
leading	O
to	O
higher	O
resolution	O
than	O
a	O
pixel	B-Algorithm
based	O
sensor	O
.	O
</s>
<s>
This	O
leads	O
to	O
what	O
is	O
in	O
cinematography	O
called	O
motion	O
blur	O
,	O
and	O
since	O
the	O
readout	O
of	O
the	O
multiple	O
lines	O
of	O
the	O
typical	O
CCD	B-Algorithm
array	I-Algorithm
occur	O
at	O
different	O
successive	O
times	O
,	O
it	O
also	O
causes	O
screen	O
tearing	O
.	O
</s>
<s>
The	O
line	O
or	O
2D	O
array	O
is	O
turned	O
90	O
degrees	O
so	O
that	O
the	O
lines	O
in	O
the	O
CCD	B-Algorithm
sensor	I-Algorithm
follow	O
the	O
expected	O
trajectory	O
of	O
the	O
object	O
of	O
interest	O
in	O
the	O
field	O
of	O
view	O
.	O
</s>
<s>
With	O
the	O
high	O
sensitivity	O
of	O
CCD	B-Algorithm
sensors	I-Algorithm
,	O
into	O
the	O
photon	O
counting	O
regime	O
,	O
this	O
can	O
lead	O
lead	O
to	O
extremely	O
high	O
detection	O
and	O
measurement	O
sensitivity	O
.	O
</s>
<s>
Additionally	O
,	O
it	O
is	O
difficult	O
to	O
achieve	O
the	O
kinds	O
of	O
coherent	O
measurement	O
gains	O
with	O
digital	O
technologies	O
besides	O
CCDs	O
,	O
because	O
they	O
suffer	O
from	O
more	O
prominent	O
aliasing	B-Error_Name
.	O
</s>
<s>
While	O
the	O
basic	O
theory	O
of	O
TDI	O
only	O
mentions	O
single	O
row	O
CCDs	O
,	O
specifically	O
designed	O
parts	O
and	O
algorithms	O
utilize	O
everything	O
from	O
a	O
few	O
lines	O
to	O
entire	O
staring	B-Algorithm
arrays	I-Algorithm
,	O
with	O
integration	O
taking	O
place	O
over	O
multiple	O
lines	O
,	O
in	O
software	O
,	O
as	O
well	O
.	O
</s>
<s>
TDI	O
CCD	O
is	O
especially	O
used	O
in	O
scanning	O
of	O
moving	O
objects	O
,	O
for	O
example	O
letter	O
and	O
film	B-Device
scanning	I-Device
,	O
or	O
from	O
a	O
moving	O
platform	O
,	O
for	O
example	O
aerial	O
reconnaissance	O
.	O
</s>
