Dalsa Spyder2 - How to Calibrate the Camera

29 Spyder2 User’s Manual
03-032-10091-06 Teledyne DALSA
i
Line av er age in a range d ependent on the cur r ent camer a
data mode setting:
8-bit: 64 to 251 DN
10 bit: 256 to 1007 DN
See secti on 3.11 Returning Video Informati on for more
information on line averages.
N otes:
• This function requires constant light input while
executing.
• This command sets gain in uncalibrated mode.
Rel ated 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. Thi s v i deo cor r ection operates on a pi xel -by-pixel basi s and i mplem ents a t w o
point correction for each pixel. This correction can reduce or eliminate image distortion
caused by the following factors:
• Fi xed Patter n N oise (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)
w here 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).
For FPN (dark light) the value of all pixels must be between 1DN and 127DN. For PRNU
(w hi te light) the val ue must be betw een 128DN and 254DN . Use the
gl command to
ensure the proper input to the digital processing, V
input
.
White light calibration will gain up to maximum white light pixel plus the maximum
FPN subtract pixel.