48
Spyder3 S3-14 and S3-24 Monochrome Camera User's Manual
03-032-20117-01
Teledyne DALSA
Analog and Digital Signal Processing Chain
Processing Chain Overview and Description
The following d iagram shows a simp lified block d iagram of the camera’s analog and d igital processing
chain. The analog p rocessing chain begins w ith an analog gain ad ju stm ent, follow ed by an analog offset
ad ju stm ent. These ad ju stm ents are ap p lied to the vid eo analog signal p rior to its d igitization by an A/ D
converter.
The d igital p rocessing chain contains the FPN correction, the PRN U correction, the backgrou nd su btract,
and the d igital gain and offset. N on-linearity look-u p table (LUT) correction is available for the 4k m od el
of cam era.
All of these elem ents are u ser p rogram m able.
Figure 26: Signal Processing Chain
Analog Processing
Op tim izing offset p erform ance and gain in the analog d om ain allow s you to achieve a better signal-to-
noise ratio and d ynam ic range than you w ou ld achieve by trying to op tim ize the offset in the d igital
d om ain. As a resu lt, p erform all analog ad ju stm ents p rior to any d igital ad ju stm ents.
1.
Analog gain (
sag
or
ccg
com m and .) is m u ltip lied by the analog signal to increase the signal strength
before the A/ D conversion. It is u sed to take ad vantage of the fu ll d ynam ic range of the A/ D
converter. For exam p le, in a low light situ ation the brightest p art of the im age m ay be consistently
com ing in at only 50% of the DN . An analog gain of 6 d B (2x) w ill ensu re fu ll u se of the d ynam ic
range of the A/ D converter. Of cou rse the noise is also increased . N ote: To m aintain valid LUT
calibration d o not u se the
sag
com m and w ith the 4k m od el. Instead , u se the
ssg
com m and .
2.
The analog offset (
sao
com m and ) or black level is an ―artificial‖ offset introd u ced into the vid eo p ath
to ensu re that the A/ D is fu nctioning p rop erly. The analog offset shou ld be set so that it is at least 3
tim es the rm s noise valu e at the cu rrent gain.
Digital Processing
To op tim ize cam era p erform ance, d igital signal p rocessing shou ld be com p leted after any analog
ad ju stm ents.
1.
Fixed p attern noise (FPN ) calibration (calcu lated u sing the
ccf
com m and ) is u sed to su btract aw ay
ind ivid u al p ixel d ark cu rrent.
Analog Processing
Digital Processing
analog video
analog
gain
analog
offset
FPN
coefficients
digital
offset
PRNU
coefficients
background
subtract
digital system
gain
sag,ccg
sao
ccf
sdo
ccp,cpa
ssb
ssg
eil
LUT
addition
4k ONLY
