Dalsa Spyder3 SG-34-04k80-00-R User Manual page 43

Spyder3 SG-34 GigE Vision Color Manual
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
calibration 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 osed .
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 end ing on offset su btracted ).
Flat Field Correction Restrictions
It is im p ortant to d o the FPN correction first. Resu lts of the 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 than 10°C
occu rs or if you change the analog gain, integration tim e, or line rate.
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 hit e 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:

Note: If your
illumination or white

reference does not
extend the full field of
view of the camera,
the camera will send a
warning.




Teledyne DALSA
50 or 60 H z am bient light flicker is su fficiently low not to affect cam era perform ance
and calibration resu lts.
For best resu lts, the analog gain shou ld be ad ju sted for the expected operating
cond itions and the ratio of the brightest to d arkest pixel in a tap shou ld be less than 3
to 1 w here:
Brightest Pixel (per tap)
3>
Darkest Pixel (per tap)
The cam era is cap able of operating u nd er a range of 8 to 1, bu t w ill clip valu es larger
than this ratio.
The brightest pixel shou ld be slightly below the target ou tpu t.
When 6.25% of pixels from a single row w ithin the region of interest are clip ped , flat
field correction resu lts m ay be inaccu rate.
Correction resu lts are valid only for the cu rrent analog gain and offset valu es. If you
change these valu es, it is recom m end ed that you recalcu lat e you r coefficients.
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