Dalsa Piranha3, Руководство пользователя

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Piranha 3 User Manual
03-032-10216-02 DALSA
36
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, or line
rate.
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 not to affect camera performance
and calibration results.
• For best results, the analog gain should be adjusted for the expected operating
conditions and the ratio of the brightest to darkest pixel in a tap should be less than 3
to 1 where:
• The camera is capable of operating under a range of 8 to 1, but will clip values larger
than this ratio.
•
The brightest pixel should be slightly below the target output.
•
When 6.25% of pixels from a single row within the region of interest are clipped, 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.
3
>
Brightest Pixel (per tap)
Darkest Pixel (per tap)
Note: If your
illumination or white
reference does not
extend the full field of
view of the camera,
the camera will send a
warning.