Piranha HS-xx RoHS User Manual
Teledyne DALSA
03-032-20013-03
53
Figure 29: 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 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 br ightest 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 .
2.
The analog offset or black level is an ―artificial‖ offset introduced into the video path
to ensu re that the A/ D w ill fu nction p rop erly. The analog offset shou ld be set so that
it is at least 3 tim es the rm s n oise 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.
2.
The d igital offset (
sdo
com m and ) enables the su btraction of the ―artificial‖ A/ D offset
(the analog offset) so that application of the PRN U coefficient doesn’t result in
artifacts at low light levels d u e to the offset valu e. You m ay w ant to set the
sdo
valu e
if you are not u sing FPN correction bu t w ant to p erform PRN U correction.
3.
Photo-Resp onse N on -Uniform ity (PRN U) coefficients are u sed to correct the
d ifference in resp onsivity of ind ivid u al p ixels (i.e. given the sam e am ou nt of light
d ifferent p ixels w ill charge u p at d ifferent rates) and the change in light intensity
across the im age either becau se of the light sou rce or d u e to op tical aberrations (e.g.
there m any be m ore light in the center of the im age). PRN U coefficients are
Summary of Contents for DALSA HS-80-08k40-xx-R
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