10 Advanced Parameters and Commands
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10.2
Background Correction (
U
,
M
)
The module “Background Correction” is closely related to the module “Integrator / Image store” at the
beginning of the processing chain (
H
). It also comprehends an image integration function. But
additionally it can subtract its current correction data image (
H
/
U
) from the incoming image and add
the offset
M
. Thus a fixed pattern noise reduction or difference image calculation is possible. Please
note that this module uses the same memory buffer as the Integrator and Image Store (
H
). It is not
useful to activate
U
and
H
at the same time.
The bits of the parameter value are divided into three different sized bit groups
a
,
b
and
c.
Each bit
group has a special function, being independent of the other ones:
•
a
: Controls the output of background correction module. Beside the normal background
correction mode also the actual memory content (
H
/
U
) of the integrator can be output. In this
case the correction module becomes an image source itself. It provides a simple image store
function. Please note that this bit group is split into two separate areas.
•
b
: Defines the number of images to be integrated and starts the integration process as soon as
a new value was set.
•
c
: Indicates whether the at last started integration is still running. This bit can only be read
out; during write access to
U
it is ignored.
The table below illustrates the possible values for the individual bit groups:
F E D C B A 9 8 7 6 5 4 3 2 1 0
- - - - - - - - c - - a b b b a
U 0
Operation Mode
Background Correction
ro
rw rw rw rw rw
Bit group
Value (hex)
Explanation
a
0
Output: deactivated. Data is passed through transparently.
1
Output: activated. Apply the current correction image (
H
/
U
) and offset value
M
.
2
Output: activated. Output of current correction image (
H
/
U
).
b
0
Integration: deactivated. The image store content is not changed.
1
Integration: 1 image. The following image is copied into the image store.
4
Integration: 8 images. The following 8 images are integrated and the result is
copied into the image store.
5
Integration: 16 images. The following 16 images are integrated and the result is
copied into the image store.
6
Integration: 32 images. The following 32 images are integrated and the result is
copied into the image store.
7
Integration: 64 images. The following 64 images are integrated and the result is
copied into the image store.
c
0
Integration completed. (This value can only be read out.)
1
Integration still running. (This value can only be read out.)
Note:
The Integration is activated by
change
of the bit group
b
of
U
. In case that e.g. directly following the
integration of 64 images a further integration of 64 images is subject to be started another value has to be
written into the register first. I.e. e.g.:
U=E
,
U=0
,
U=E
.
Example:
Integration of 32 images simultaneously to the output of the actual integration image
(a=2, b=6) => abbba = „11100“ binary = 0x1A. After that, reactivate the background
correction.
Command sequence:
>
U=1A[CR]
...wait for at least 34 image cycles (32 + 2 frames jitter buffer, 0.85 seconds at 40
images / sec.) or poll the state of bit group
c
with
U[CR]
...
>
U=1[CR]
VDS Vosskühler GmbH
IRC-320
