Piranha HS-S0-06K Camera User Manual
03-032-20213-01
Teledyne DALSA
28
Lens an d light sou rce non -u niform ity Correction is im p lem ented su ch that for each p ixel:
V
output
=[(V
input
- dark offset- FPN ( pixel )) * digital gain * PRNU (pixel)]
w here
V
ou tp u t
=
d igital ou tp u t p ixel valu e
V
inp u t
=
d igital inp u t p ixel valu e from the CCD
PRN U( p ixel)
=
PRN U correction coefficient for this p ixel
FPN ( p ixel )
=
FPN correction coefficient for this p ixel
The algorithm is p erform ed in tw o step s. The fixed offset (FPN ) is d eterm ined first by
p erform ing a calcu lation w ithou t any light. This calibration d eterm ines exactly how m u ch
offset to su btract p er p ixel in ord er to obtain flat ou tp u t w hen the CCD is not exp o sed .
The w hite light calibration is p erform ed next to d eterm ine the m u ltip lication factors
requ ired to bring each p ixel to the requ ired valu e (target) for flat, w hite ou tp u t. Vid eo
ou tp u t is set slightly above the brightest p ixel (d ep en d in g on offset su btr acted ).
Flat Field Correction Restrictions
It is im p ortant to d o the FPN correction first. Resu lts of th e FPN correction are u sed in the
PRN U p roced u re. We recom m end that you rep eat the correction w hen a tem p eratu re
change greater th an 10°C occu rs or if you change the integration tim e or nu m ber of
integration stages.
PRN U correction requ ires a clean, w hite reference. The qu ality of this reference is
im p ortant for p rop er calibration. White p ap er is often not su fficient becau se the grain in
the w hite p ap er w ill d istort the correction. White p lastic or w hite ceram ic w ill lead to
better balancing.
For best resu lts, ensu re that:
1.
60 H z am bient light flicker is su fficiently low not to affect cam era
p erform ance and calibration resu lts.
2.
The brightest p ixel sh ou ld be slightly below the target ou tp u t.
3.
When 6.25% (or m ore) of p ixels from a single row w ithin the region of interest
are clip p ed , flat field correction resu lts m ay be inaccu rate.
4.
Correction resu lts are valid only for the cu rrent stage selection. If you change
the nu m ber of stages, it is recom m end ed that you recalcu late you r
coefficients.
Note: If your
illumination or white
reference does not
extend the full field of
view of the camera,
the camera will send a
warning.
