Dalsa PC-30-02K80 - Flat Field Correction; Flat Field Correction Overview

Piranha Color Camera User’s Manual 42
DALSA 03-032-10211-01 5/9/2007
Offset value in a range from 0 to 255DN (12 bit LSB).
Notes: To return the current analog offset value, use the command
gcp or get sao.
Example:
sao 2 35
Related Commands:
3.15 Flat Field Correction
Flat Field Correction Overview
This camera has the ability to calculate correction coefficients in order to remove non-
uniformity in the image. This video correction operates on a pixel-by-pixel basis and
implements a two point correction for each pixel. This correction can reduce or
eliminate image distortion caused by the following factors:
 Fixed Pattern Noise (FPN)
 Photo Response Non Uniformity (PRNU)
Lens and light source non-uniformity Correction is implemented such that for each
pixel:

Analog Processing
Digital Processing
analo gvideo
ana log
gain
analog
offset
FPN
coefficients
dig i tal
offset
PRNU
coefficients
background
subtr act
digitalsys tem
gain
sag,ccg
sao
ccf
sdo
ccp,cpa ssb
ssg
background
addition
digitalvideo
sab
background
addition
digitalvideo
eil
LU T
addition
V
output
=[(V
input
- FPN( pixel ) - digital offset) * PRNU(pixel) – Background Subtract] x
System Gain + Background Addition
where V
output
= digital output pixel value
V
input
= digital input pixel value from the CCD
PRNU( pixel) = PRNU correction coefficient for this pixel
FPN( pixel ) = FPN correction coefficient for this pixel
Background Subtract = background subtract value
System Gain = digital gain value
Background Addition = background addition value
The algorithm is performed in two steps. The fixed offset (FPN) is determined first by
performing a calibration without any light. This calibration determines exactly how
much offset to subtract per pixel in order to obtain flat (zero) output when the CCD is
not exposed.
Note: If your
illumination
or white
reference
does not
extend the
full field of
view of the
camera, the
camera will
send a
warning.