Dalsa Piranha ES Series, User Manual

Page: 58 / 106

Piranha ES-xx User Manual
03-032-20070-02 Teledyne DALSA
58
Calibrating Analog Offset
Pu rp ose: Instead of m anu ally setting the analog offset to a sp ecific valu e,
the cam era can d eterm ine ap p rop riate offset valu es. This
command calculates and averages each tap’s pixels w ithin the
ROI and sets the offset to achieve the sp ecified average target
valu e.
Syntax:
cao t i
Syntax Elem ents:
t
Tap selection. Use
0
for all tap s or
1
to nu m ber of CCD tap s
for ind ivid u al tap selection.
i
Average target valu e in a range from
1
to
255
DN (12 bit
LSB).
N otes:

Perform analog offset calibration before p erform ing FPN and
PRN U coefficients.

To u se this com m and , CCD shift d irection shou ld be
controlled internally, either
scd 0
or
1
Exam p le:
cao 1 50
Updating the Gain Reference
To update the analog gain reference:
Pu rp ose: Sets the cu rrent analog gain setting to be the 0d B p oint. This is
u sefu l after tap gain m atching allow ing you to change the gain on
all tap s by the sam e am ou nt.
Syntax:
ugr
Calibrating the Camera to Remove Non-Uniformity
(Flat Field Correction)
Flat Field Correction Overview
This cam era has the ability to calcu late correction coefficients in ord er to rem ove non -
u niform ity in the im age w hen op erating in TDI Mod e. This vid eo correction o p erates on a
p ixel-by-p ixel basis and im p lem ents a tw o p oint correction for each p ixel. This correction
can red u ce or elim inate im age d istortion cau sed by the follow ing factors:

Fixed Pattern N oise (FPN )

Photo Resp onse N on Uniform ity (PRN U)

Lens and ligh t sou rce non -u niform ity
Correction is im p lem ented su ch that for each p ixel:
V
output
=[(V
input
- FPN( pixel ) - digital offset) * PRNU(pixel) – Background Subtract] x System Gain
w here V
ou tp u t
= d igital ou tp u t p ixel valu e
V
inp u t
= d igital inp u t p ixel valu e from the CCD