Dalsa Piranha3, User Manual

Page: 46 / 91

Piranha 3 User Manual
03-032-10216-02 DALSA
46
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.
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 (ROI).
2
= Calculates the PRNU coefficients using the entered target
value as shown below:
PRNU Coefficient =
Target
(AVG Pixel Value ) ‐ (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. Recommended peak video output before PRNU
calibration is 5-20% lower than target. The target value must be
greater than the current peak output value.
This command performs the same function as the
cpp
command but requires that you enter a target value.
3
= This algorithm includes an analog gain adjustment prior to
PRNU calibration. Analog gain is first adjusted so that the peak
pixel value in 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:
PRNU Coefficient =
Target
(AVG Pixel Value ) ‐ (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.
4 = Calculates the PRNU coefficient in the same way as cpa 2
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 1024 to 40554DN.
Notes:
•
Perform all analog adjustments before calibrating PRNU.
•
Calibrate FPN before calibrating PRNU. If FPN cannot be
calibrated, use the
rpc
command to reset all coefficients to
zero, and save them to memory with the
wfc
command. You
can then adjust the digital offset (
sdo
command) to remove
some of the FPN.
•
Note: Refer to Calibrating the Camera to Remove Non-
Uniformity (Flat Field Correction)on page 35 for a procedural