User`s manual
64 PRELIMINARY Spyder 3 CL User's Manual
03-032-20008-03 DALSA
PRNU Correction
Performing PRNU to a user entered value
Purpose: Performs PRNU calibration to user entered value and eliminates the
difference in responsivity between the most and 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) and the
ssg command to 4096 (unity
digital gain). The pixel coefficients are disabled (
epc 0 0) during
the algorithm execution but returned to the state they were in prior
to command execution.
Syntax:
cpa i i
Syntax Elements:
i
PRNU calibration algorithm to use:
1 = This algorithm first adjusts each tap’s analog gain so that 8-
13% of pixels within a tap are above the value specified in the
target value parameter. PRNU calibration then occurs using the
peak pixel in the region of interest.
This algorithm is recommended for use only when FPN is
negligible and FPN coefficients are set to zero. Since this
algorithm adjusts the analog gain, it also affects FPN. If FPN is
calibrated prior to running this algorithm, FPN will be
observable in dark conditions and an incorrect FPN value will be
used during PRNU calibration resulting in incorrect PRNU
coefficients.
2 = Calculates the PRNU coefficients using the entered target
value as shown below:
PRNUC o efficient=
Targ et
(AVG PixelValue)‐(FPN +value)
sdo
i
i
i
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 that the target value (set with the next
parameter) is set to be at least equal to the highest pixel across
all cameras so that all pixels can reach the highest pixel value
during calibration.
3 = This algorithm includes an analog gain adjustment prior to
PRNU calibration. Analog gain is first adjusted so that the peak
pixel value in the tap’s ROI is within 97% to 99% of the specified
target value. It then calculates the PRNU coefficients using the
target value as shown below:
PRNUC o efficient=
Targ et
(AVG PixelValue)‐(FPN +value)
sdo
i
i
i
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.
This algorithm is useful for achieving uniform output across
multiple cameras by first adjusting analog gain and then
performing PRNU calibration. This algorithm is recommended