Spyder3 SG-34 GigE Vision Color Manual
41
Teledyne DALSA
03-032-20124-00
Camera Calibration
Processing Chain Overview and Description
The following d iagram shows a simp lified block d iagram of the camera’s d igital processing chain.
The d igital p rocessing chain contains the FPN correction, the PRN U correction, the backgrou nd su btract,
and the d igital gain and offset ad ju stm ents.
These elem ents are u ser p rogram m able and m ost are m em bers of the
Analog Controls
and
Advance
Processing
sets.
Figure 23: Signal Processing Chain
Digital Processing
1.
Fixed p attern noise (FPN ) calibration (calcu lated u sing the
FPN C
alibrate
p aram eter) is u sed to
su btract aw ay ind ivid u al p ixel d ark cu rrent.
2.
Photo-Resp onse N on -Uniform ity (PRN U) coefficients (calcu lated u sing the
PRN U Target
and
Calibrate PRN U
p aram eters in the
Advance Processing
fam ily) are u sed to correct the d ifference in
resp onsivity of ind ivid u al p ixels (i.e. given the sam e am ou nt of light d ifferent p ixels w ill ch arge u p
at d ifferent rates) and the change in light intensity across the im age either becau se of the light sou rce
or d u e to op tical aberrations (e.g. there m ay be m ore light in the center of the im age). PRN U
coefficients are m u ltip liers and are d efined to be of a valu e greater than or equ al to 1. This ensu res
that all p ixels w ill satu rate together.
3.
Calibrate White Balance
calibrates ind ivid u al colou r gain settings so that the ou tp u ts are equ al
betw een the colors.
4.
The
Color Gain (D B)
sp ecifies the gain in d B for a given color and tap .
5.
Backgrou nd su btract (
Background Subtract (D N )
p aram eter) and system (d igital) gain (
D igital
Gain (D N )
p aram eter) are u sed to increase im age contrast after FPN and PRN U calibration. It is
u sefu l for system s that p rocess 8-bit d ata bu t w ant to take ad vantage of the cam era’s 12 bit d igital
p rocessing chain. For exam p le, if you find that you r im age is consistently betw een 128 and 255DN (8
