Falcon 4M Camera Manual
Teledyne DALSA
03-032-20044-03
53
3.7.5 Performing PRNU Calibration
Pu rp ose:
Perform s PRN U calibration to a targeted , u ser d efined valu e and
elim inates the d ifference in resp onsivity betw een the m ost and least
sensitive p ixel creating a u niform resp onse to light. Using this
com m and , you m u st p rovid e a calibration target.
Execu ting these algorithm s cau ses the
ssb
com m and to be set to 0
(no backgrou nd su btraction) and the
ssg
com m and to 4096 (u nity
d igital gain). The p ixel coefficients are d isabled (
epc 0 0
) d u ring
the algorithm execu tion bu t retu rn to the state they w ere p rior to
com m and execu tion.
Syntax:
cpa
x y
Syntax Elem ents:
x
PRN U calibration algorithm to u se:
2
= Calcu lates the PRN U coefficients u sing the entered target
valu e as show n below :
PRNU Coefficient =
Target
(AVG Pixel Value ) - (FPN +
value)
sdo
i
i
i
This algorithm is u sefu l for achieving u niform ou tp u t across
m u ltip le cam eras. It is im p ortant that the target valu e (set w ith
the next p aram eter) is set to be greater than 1.2X than the
average signal level w hen FPN correction is enabled (EPC 1 0).
This is to ensu re that fu ll signal sw ing can b e reached for m ost
p ixels.
y
Peak target valu e in a range from 1 to 1023DN . The target valu e
m u st be greater than the cu rrent p eak ou tp u t valu e. If som e
p ixels are below the target valu e then the PRN U coefficients for
said p ixels w ill be set to 1X (ie. PRN U coefficients can never be
less than 1X). Sim ilarly the m axim u m PRN U coefficient is 4X,
8X, or 16X d ep end ing on the SPM setting , if m ore is need ed it
w ill clip at 4X, 8X, or 16X, resp ectively.
N otes:
Calibrate FPN before calibrating PRN U. If you a re not
p erform ing FPN calibration then issu e the
rpc
(reset p ixel
coefficients) com m and and set the
sdo
(set d igital offset) valu e
so that the ou tp u t is near zero u nd er d ark. FPN calibration is
highly recom m end ed , the u se of SDO is not.
The
cpa
com m and is not available w hen the cam era is u sing the
factory calibrated coefficients (
csn 0-2
). You m u st select the
u ser coefficient set (
csn 3-5
) before you can p erform PRN U
calibration. An error m essage is retu rned if you attem p t to
p erform PRN U calibration w hen u sing
csn 0-2
.
Exam p le:
cpa 2 700