Pike
Technical
Manual
V5.2.3
123
Description of the data path
Description
of
the
data
path
Automatic generation of correction data
Requirements
Shading
correction
compensates
for
non-homogeneities
by
giving
all
pixels
the
same
gray
value
as
the
brightest
pixel.
This
means
that
only
the
background
must
be
visible
and
the
brightest
pixel
has
a
gray
value
of
less
than
255
when
automatic
generation
of
shading
data
is
started.
It
may
be
necessary
to
use
a
neutral
white
reference,
e.g.
a
piece
of
paper,
instead
of
the
real
image.
Algorithm
After
the
start
of
automatic
generation,
the
camera
pulls
in
the
number
of
frames
set
in
the
GRAB_COUNT
register.
Recommended
values
are
2,
4,
8,
16,
32,
64,
128
or
256.
An
arithmetic
mean
value
is
calculated
from
them
(to
reduce
noise).
After
this,
a
search
is
made
for
the
brightest
pixel
in
the
mean
value
frame.
The
brightest
pixel(s)
remain
unchanged.
A
factor
is
then
calculated
for
each
pixel
to
be
multiplied
by,
giving
it
the
gray
value
of
the
brightest
pixel.
All
of
these
multipliers
are
saved
in
a
shading
reference
image.
The
time
required
for
this
process
depends
on
the
number
of
frames
to
be
calculated
and
on
the
resolution
of
the
image.
Correction
alone
can
compensate
for
shading
by
up
to
50%
and
relies
on
full
resolution
data
to
minimize
the
generation
of
missing
codes.
How
to
proceed:
Figure 45: Automatic generation of a shading image
Set GrabCount to # of
desired frames
Set BuildImage Flag to true
Poll SHGD_Control
Register until Busy and
BuildImage Flag are
resetted
