<s>
In	O
digital	B-Algorithm
image	I-Algorithm
processing	I-Algorithm
,	O
sub-pixel	B-Algorithm
resolution	I-Algorithm
can	O
be	O
obtained	O
in	O
images	O
constructed	O
from	O
sources	O
with	O
information	O
exceeding	O
the	O
nominal	O
pixel	B-Algorithm
resolution	I-Algorithm
of	O
said	O
images	O
.	O
</s>
<s>
When	O
an	O
object	O
with	O
a	O
certain	O
resolution	O
is	O
represented	O
on	O
a	O
display	O
with	O
lower	O
resolution	O
,	O
the	O
imperfections	O
due	O
to	O
the	O
loss	O
of	O
information	O
are	O
known	O
as	O
aliasing	B-Error_Name
.	O
</s>
<s>
The	O
most	O
common	O
kind	O
of	O
visual	O
aliasing	B-Error_Name
is	O
when	O
a	O
smooth	O
object	O
such	O
as	O
a	O
line	O
appears	O
jagged	O
because	O
the	O
pixels	O
are	O
large	O
enough	O
to	O
be	O
easily	O
distinguished	O
by	O
the	O
naked	O
eye	O
.	O
</s>
<s>
These	O
effects	O
can	O
be	O
reduced	O
by	O
anti-aliasing	O
techniques	O
,	O
e.g.	O
</s>
<s>
Now	O
sub-pixel	B-Algorithm
resolution	I-Algorithm
of	O
well	O
resolved	O
features	O
can	O
measure	O
ship	O
movements	O
which	O
are	O
an	O
order	O
of	O
magnitude	O
(	O
10×	O
)	O
smaller	O
.	O
</s>
<s>
Whether	O
features	O
in	O
a	O
digital	O
image	O
are	O
sharp	O
enough	O
to	O
achieve	O
sub-pixel	B-Algorithm
resolution	I-Algorithm
can	O
be	O
quantified	O
by	O
measuring	O
the	O
point	O
spread	O
function	O
(	O
PSF	O
)	O
of	O
an	O
isolated	O
point	O
in	O
the	O
image	O
.	O
</s>
<s>
It	O
is	O
also	O
important	O
when	O
attempting	O
sub-pixel	B-Algorithm
resolution	I-Algorithm
to	O
keep	O
image	O
noise	O
to	O
a	O
minimum	O
.	O
</s>
<s>
Appropriate	O
pixel	O
averaging	O
,	O
through	O
both	O
time	O
(	O
for	O
stationary	O
images	O
)	O
and	O
space	O
(	O
for	O
uniform	O
regions	O
of	O
the	O
image	O
)	O
is	O
often	O
used	O
to	O
prepare	O
the	O
image	O
for	O
sub-pixel	B-Algorithm
resolution	I-Algorithm
measurements	O
.	O
</s>
