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Falcon2 4M, 8M, and 12M Camera User's Manual
03-032-20107-03
Teledyne DALSA
cam era w ill have the sam e resp onsivity since the light level and target valu e are alw ays the sam e.
Typ ical ou tp u t levels for the cam era at this light level are 680 DN (10 bit).
4.
The sensor w ind ow at this p oint has been cleaned thorou ghly su ch that there are no significant
blem ishes p resent.
5.
For the m onochrom e cam era only, PRN U target is set to 840 DN (82.11 % p eak).
6.
PRN U calibration is ru n.
How can one match gain and offset values on multiple cameras?
One w ay is of cou rse to u se flat field correction. All cam eras w ou ld be set u p u nd er the sam e cond itions ,
inclu d ing lighting, and then calibrated w ith FPN and PRN U. This p rocess can be tim e-consu m ing and
com p licated (esp ecially the w h ite target). Another w ay is to u se global FPN (Sensor Control > Black Level
Selector > DigitalAll1):
1.
Starting from factory settings (factory flat field ), take note w hat the highest d ark offset is am ong
the set of cam eras. If the highest d ark offset is hig her than abou t 16 DN (10 bit) you m ight w ant to
consid er recalibrating the FPN correction. You can u se the histogram featu re in Cam Exp ert to
d eterm ine this valu e see Figu re 25. Large d ifferences in d ark offset betw een th e factory and u ser
are typ ically cau sed by d ifferences in tem p eratu re from factory to u ser. Large d ark offsets w ill
resu lt in PRN U-correction-ind u ced FPN and shou ld therefore be avoid ed .
2.
Decrease global FPN (increase the offset in d ark) on all cam eras u nt il they are the sam e and reach
at least 4 DN (10 bit).
3.
Illu m inate to abou t 80 % satu ration (820 DN , 10 bit) and note the highest signal level am ong the
set of cam eras.
4.
Increase the system gain (Sensor Control > Gain Selector > DigitalAll1) on the cam eras u ntil they
all reach the sam e ou tp u t level (highest of all cam eras).
5.
Place cam era in the d ark and rep eat step 2 to 4 u ntil both d ark offset and 80 % sat signal levels are
equ al on all cam eras.
Hot Pixels and Long Exposure Times
The cam era is calibrated and op tim ized for an exp osu re tim e of 1500 m icro second s p rovid ing p eak FPN
and PRN U p erform ance are at this setting. This FPN correction also m anages hot p ixels for the sam e
exp osu re tim e. Changing the exp osu re tim e to very long tim es , su ch as 60000 m icrosecond s, can
introd u ce ad d itional u ncorrected hot p ixels in the im age. The u ser can elim inate these p ixels by
p erform ing a u ser p ixel rep lacem ent calibration w hich w ill cap tu re and correct these p ixels. This
correction elim inates hot p ixels at long exp osu re tim e w hile m aintaining the sam e FPN ch aracteristics.
How to do a FFC Setup via Sapera CamExpert
The Sap era LT Cam Exp ert tool p rovid es an easy GUI based m ethod for a u ser to p erform a Flat Fiel d
Calibration. The p rocess first requ ires the u ser to p lan acqu isitions in d ark and bright cond itions,
follow ed by the FFC p rocess itself. Please review the list of best p ractices in the
section. The step s to p erform a FFC calibration u sing Cam Exp ert are d etailed below .
.
1.
Verify a Dark Acquisition.
Close the cam era lens iris and cover the lens w ith a lens cap . Using Cam Exp ert, click on the grab
bu tton and then the histogram bu tton. The follow ing figu re show s a typ ical histogram for a
Falcon2 grabbing a very d ark im age.