40
Piranha4 8k Color Camera User's Manual
03-032-20274-00
Teledyne DALSA
Figure 19: Camera Calibration Process.
Digital Processing
1.
Fixed pattern noise (FPN) calibration is used to subtract any residual dark level that
may occur in the application.
2.
Photo response non uniformity (PRNU) calibration is used to correct for variations in
the illumination intensity and / or lens vignetting. When performed, this calibration
will cause the camera to have a flat response to a white target in the field of view.
The output target value for PRNU calibration can be set by the user.
3.
The white balancing gains are used set the red, green and blue response to equal
values with a white target in the field of view. The white balance gains can be
individually set by the user, but will be overridden by the camera when the camera
performs PRNU calibration or white balancing commands.
4.
Color correction is available for those users that need to compensate for the spectral
transmission characteristics of the sensors color filters and the customers light
source. This can be achieved by imaging the Gretag Macbeth® ColorChecker®
illuminated by the application’s light source and processing the image using a color
correction tool to generate the desired color correction parameters to be provided to
the camera via its CamExpert user interface.
Note:
Prior to imaging the Gretag Macbeth ColorChecker, the camera should have
been calibrated with a white reference in place of the Gretag Macbeth ColorChecker
and color correction must be turned off. The calibration process will ensure the
camera output is uniform and white balanced.
5.
A single overall system gain is applied equally to all three colors. It will therefore not
cause color distortion when changed.
6.
A factory setting for white LED color correction can be applied, if needed, by entering
parameters via CamExpert GUI.
Calibration
1.
The goal of calibration is to produce a uniform, white balanced and, if required, color
corrected image at the desired level out of the camera when it is imaging a uniform white
object, using the optical setup of the user’s application.
2.
The user should configure the camera to use the EXSYNC and exposure timing they desire
plus adjust the light level for normal operation. The lens should be at the desired
magnification, aperture and be in focus. As the white reference located at the object plane
will be in focus, any features on its surface (e.g. dust, scratches) will end up in the
calibration profile of the camera. To avoid this, use a clean white plastic or ceramic material,
Video
Gain
‡
Output
Video
Digital Processing
(
color
)
-
+
Offset
‡
BlackLevel
(
ssb
)
x
Gain
(
ssg
3
)
-
Calibrate FPN*
flatfieldCalibrationFPN
(
ccf
)
xR
xG xB
White
Balancing
†
BalanceWhiteAuto
(
bwa
,
ssg
(
0
,
1
,
2
))
X X X X
X X X X
X X X X
Color
Correction
†
colorCorrectionMode
(
ctv
)
x
Calibrate
PRNU*
flatfieldCorrectionMode
flatfieldCalibrationPRNU
flatfieldCorrectionAlgorithm
(
cpa
,
ffm
)
*per pixel
†
per color
‡
applies to all
