PRELIMINARY
4M Stop Action Camera Manual
PRELIMINARY
4M Stop Action Camera Manual
03-32-10121-09
DALSA
32
3.6 Flat Field Correction
to remove non-
correction operates on a pixel-by-pixel basis and
int correction for each pixel. This correction can reduce or eliminate
)
(PRNU)
V
output
=[(V - FPN( pixel ) - digital offset) * PRNU(pixel) – Background Subtract] x System Gain
w
tput
alue
V
t pixel value from the sensor
NU correction coefficient for this pixel
for this pixel
ue
ined first by
s exactly how much
ensor is not exposed.
ine the multiplication
flat, white output.
n offset subtracted).
e FPN correction first. Results of the FPN correction are used in the
ecommend that you repeat the correction when a temperature
c
tegration time.
P
e quality of this reference is
import
ecause the grain in
t
mic will lead to
b
1.
60 Hz ambient light flicker is sufficiently low not to affect camera performance
and calibration results.
2.
The brightest pixel should be slightly below the target output.
3.
When 6.25% of pixels from a single row within the region of interest are clipped,
flat field correction results may be inaccurate.
4.
Correction results are valid only for the current analog offset values. If you
change this value, it is recommended that you recalculate your coefficients.
Note: If your
illumination or white
reference does not
extend the full field of
view of the camera,
the camera will send a
warning.
This camera has the ability to calculate correction coefficients in order
uniformity in the image. This video
implements a two po
image distortion caused by the following factors:
•
Fixed Pattern Noise (FPN
•
Photo Response Non Uniformity
•
Lens and light source non-uniformity
Correction is implemented such that for each pixel:
input
here V
ou
=
digital output pixel v
input
=
digital inpu
PRNU( pixel)
=
PR
FPN( pixel )
=
FPN correction coefficient
Background Subtract
=
background subtract val
System Gain
=
digital gain value
The algorithm is performed in two steps. The fixed offset (FPN) is determ
performing a calculation without any light. This calibration determine
offset to subtract per pixel in order to obtain flat output when the s
The white light (PRNU) calibration is performed next to determ
factors required to bring each pixel to the required value (target) for
Video output is set slightly above the brightest pixel (depending o
It is important to do th
PRNU procedure. We r
hange greater than 10°C occurs or if you change the frame rate or in
RNU correction requires a clean, white reference. Th
ant for proper calibration. White paper is often not sufficient b
he white paper will distort the correction. White plastic or white cera
etter balancing.
For best results, ensure that:
