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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 th e 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 hen 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 be 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 Sap era 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 the ability to ad d either a p ositive o r 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 changed .
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 u ser's ap p lication.
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 a s the
averaging p rocess of the cam era w ill d im inish the effects on any sm all variation in the w hite reference.
The u ser m ay w ish to start the calibration p rocess by evalu ating the characteristics of their setu p w ith no
calibration enabled . This can be read ily achieved 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 D N 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
calibration can be p erform ed u sing a target valu e you w ant all the p ixels to achieve. 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 three 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
03-032-20180-00
Piranha4 4K Camera Color User's Manual
era.
Once com p lete, a PRN U
Teledyne DALSA
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