Dalsa Piranha 2 Series - 3.14 How to Calibrate the Camera

35 Piranha 2 User’s Manual
03-032-00493-14 Teledyne DALSA
To calibrate the analog gain:
Syntax:
cag t i
Syntax Elements:
t
Tap selection. Allowable range is 1 to 4, or 0 for all taps.
i
Line average in a range dependent on the current camera
data mode setting:
8-bit: 64 to 251 DN
10 bit: 256 to 1007 DN
See section 3.11 Returning Video Information for more
information on line averages
Notes:
 This function requires constant light input while executing.
 This command sets gain in uncalibrated mode.
Related Commands:
gla, gl
Example:
cag 1 156
3.14 How to Calibrate the Camera
Calibration Overview
This camera has the ability to calibrate itself in order to remove non-uniformity in the
image. This video correction operates on a pixel-by-pixel basis and implements a two
point correction for each pixel. This correction can reduce or eliminate image distortion
caused by the following factors:
Fixed Pattern Noise (FPN)
Photo Response Non Uniformity (PRNU)
Lens and light source non-uniformity
The two point correction is implemented such that for each pixel:
V
output
= (V
input
- FPN( pixel ) - digital offset) * PRNU(pixel)
where
V
output
=
digital output pixel value
V
input
=
digital input pixel value from the CCD
PRNU( pixel)
=
PRNU correction coefficient for this pixel
FPN( pixel )
=
FPN correction coefficient for this pixel
The calibration algorithm is performed in two steps. The fixed offset (FPN) is determined
first by performing a calibration without any light. This calibration determines exactly
how much offset to subtract per pixel in order to obtain flat output when the CCD is not
exposed.
The white light calibration is performed next to determine the multiplication factors
required to bring each pixel to the required value (balance target) for flat, white output.
Video output is set slightly above the brightest pixel (depending on offset subtracted).
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