Dalsa Spyder2 S2-1-40 Series, User Manual

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30 Spyder2 User’s Manual
03-32-10091-04 DALSA
To calibrate the analog gain:
Syntax:
cag t i
Syntax Elements:
t
Tap selection. Allowable values are
1
for one tap or
0
for all
taps. Since the Spyder2 is a one tap camera, the values 1 or 0
are interchangeable.
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.