Piranha ES-Sx User Manual
Teledyne DALSA
03-032-20162-00
33
PRNU Correction
Performing PRNU to a user entered value
Purpose:
Note: CPA 5/6
should be used.
CPA 2/4 is
available in the
camera but may
cause your camera
to not meet
camera
specifications.
Performs PRNU calibration to user entered value and eliminates the
difference in responsivity between the most and the least sensitive
pixel creating a uniform response to light. Using this command, you
must provide a calibration target.
Executing these algorithms causes the
ssb
command to be set to 0 (no
background subtraction), the
ssg
command to 0 (unity digital gain),
and the
sab
command to 0 (no background addition). The pixel
coefficients are disabled (epc 0 0) during the algorithm execution but
returned to the state they were prior to command execution.
Additionally when CPA 5/6 are used, the digital gains will be
automatically adjusted for optimal performance when calculating
pixel coefficients. It is expected that after using CPA 5/6 that your
gains will be set to a new value.
Syntax:
cpa i i
Syntax Elements:
i
PRNU calibration algorithm to use:
5
= Calculates the PRNU coefficients and Digital gains using the
entered target value as shown below:
Target value (14 bits) in range from 4096 to 16220DN
For example, if the camera is in 8 bit mode and the target is to be
200DN, use (200x64) = 12800 (14 bit equivalent) as target value.
The calculation is performed for all sensor pixels but warnings
are only applied to pixels in the region of interest. This algorithm
is useful for achieving uniform output across multiple cameras.
It is important to note that the target value (set with the next
parameter) does not need to be equal of higher to the highest
pixel across all cameras. Since the cpa 5 function now controls
gain, negative gain values may also be set automatically. The
ideal result of CPA 5 is that the PRNU coefficients and the
camera gain are setup automatically.
6
= Calculates the PRNU coefficient and the Digital gains in the
same way as
cpa 5
with the exception that this command only
calculates PRNU for pixels within the current Region of Interest
(ROI).
i
Peak target value in a range from 4096 to 16220 DN.
Notes:
•
Calibrate FPN before calibrating PRNU. If you are not
performing FPN calibration then issue the
rpc
(reset pixel
coefficients) command.
•
CPA 2 and CPA 4 functions are still available for use in the
camera, but Teledyne DALSA does not recommend their use
and will not guarantee any camera specifications. The improper
use of CPA 2/4 may cause the camera to exceed its designed
performance criteria.
•
CPA 2/4 will only calculate a PRNU coefficient and will not
