72
Piranha4 2K and 4K Camera Color User's Manual
03-032-20180-05
Teledyne DALSA
cam era to have a flat resp onse to a w hite target in the field of view . The ou tp u t target valu e for
PRN U calibration can be set by the u ser.
3.
The w hite balancing gains are u sed set the red , green and blu e resp onse to equ al valu es w ith a
w hite target in the field of view . The w hite balance gains can be ind ivid u ally set by the u ser, bu t
w ill be overrid d en by the cam era w h en the cam era p erform s PRN U calibration or w hite
balancing com m and s.
4.
Color correction is available for those u sers that need to com p ensate for the sp ectral transm ission
characteristics of the sensors color filters and the cu stom ers light sou rce. This can b e achieved by
im aging the Gretag Macbeth® ColorChecker® illu m inated by the ap p lication’s light sou rce and
p rocessing the im age u sing a color correction d em onstration tool p rovid ed as p art of Teled yne
DALSA’s Sapera Processing softw are. This tool w ill generate the d esired color correction file that
can be d ow nload ed to the cam era.
Note:
Prior to im aging the Gretag Macbeth ColorChecker , the cam era shou ld have been calibrated
w ith a w hite reference in p lace of the Gretag Macbeth ColorChecker and color correction m u st be
tu rned off. The calibration p rocess w ill ensu re the cam era ou tp u t is u niform and w hite balanced .
5.
The introd u ction of offsets has lim ited valu e in color ap p lications as it w ill cau se color d istortion.
H ow ever, the cam era has th e ability to ad d either a p ositive or negative offset as requ ired by a
sp ecific ap p lication. This offset can be u sefu l w hen trying to m easu re d ark noise w here black
level clip p ing w ill cau se an error in the resu lt.
6.
A single overall system gain is ap p lied equ ally to all three colors. It w ill therefore not cau se color
d istortion w hen ch anged .
7.
A factory setting for w hite LED color correction can be ap p lied , if need ed .
Calibration
The goal of calibration is to p rod u ce a u niform , w hite balanced and , if requ ired , color corrected im age at
the d esired level ou t of the cam era w hen it is im aging a u niform w hite object, u sing the op tical setu p of
the user’s application.
The u ser shou ld configu re the cam era to u se the EXSYN C and exp osu re tim ing they d esire p lu s ad ju st the
light level for norm al op eration. The lens shou ld be at the d esired m agnification, ap ertu re and be in focu s.
As the w hite reference located at the object p lane w ill be in focu s, any featu res on its su rface (e.g. d u st,
scratches) w ill end u p in the calibration p rofile of the cam era. To avoid this, u se a clean w hite p lastic or
ceram ic m aterial, not p ap er. Id eally, the w hite object shou ld m ove d u ring the calibration p rocess as the
averaging p rocess of the cam era w ill d im inish the effects on any sm all vari ation in the w hite reference.
The u ser m ay w ish to start the calibration p rocess by evalu ating the ch aracteristics of their setu p w ith no
calibration enabled . This can be read ily ach ieved by d isabling FPN , PRN U & color correction coefficients,
setting w hite balance red , green and blu e gains to one, and the system gain to one.
Begin by ad ju sting the system gain u ntil the p eak intensity of the three colors is at the d esired DN level.
You m ay w ant to u se the w hite balance gains to ad ju st the p eak of each color to be a sim ilar DN valu e,
bu t this is not necessary. Before p roceed ing any fu rther, it is d esirable to com p lete an FPN calibration.
This is best p erform ed u sing a lens cap to ensu re no light gets into the cam era
.
Once com p lete, a PRN U
calibration can be p erform ed u sing a target valu e you w ant all the p ixels to ach ieve. This target valu e can
be higher or low er than the p eak valu es you observed w hile initially setting u p the cam era. Once PRN U
calibration is com p lete, it w ill take several second s, all th ree colors shou ld be at the target valu e, w hite
balance gains w ill have been ad ju sted to su it the cam eras op tim u m setu p for a balanced w hite ou tp u t,
and the correction coefficient w ill be enabled . The system gain w ill rem ain as originally set. The
coefficient and gain p aram eters, tim ing and control configu ration etc can be stored in any one of eight
