Piranha Color Camera User’s Manual 43
DALSA 03-032-10211-01 5/9/2007
The white light calibration is performed next to determine the multiplication factors
required to bring each pixel to the required value (target) for flat, white output. Video
output is set slightly above the brightest pixel (depending on offset subtracted).
Flat Field Correction Restrictions
It is important to do the FPN correction first. Results of the FPN correction are used in
the PRNU procedure. We recommend that you repeat the correction when a
temperature change greater than 10°C occurs or if you change the analog gain,
integration time, line rate, or SRM.
PRNU correction requires a clean, white reference. The quality of this reference is
important for proper calibration. White paper is often not sufficient because the grain in
the white paper will distort the correction. White plastic or white ceramic will lead to
better balancing.
For best results, ensure that:
50 or 60 Hz ambient light flicker is sufficiently low so as not to affect camera
performance and calibration results.
The analog gain should be adjusted for the expected operating conditions.
The ratio of the brightest to darkest pixel in a tap should be less than 3 to 1, where:
The brightest pixel should be slightly below the target output.
When greater than 6.25% of the pixels from a single row within the region of interest
are clipped, then flat field correction results may be inaccurate.
Correction results are valid only for the current analog gain and offset values. If you
change these values, it is recommended that you recalculate your coefficients.
Bri
htest Pixel
er ta
Darkest Pixel (per tap)
3>
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