6
3
1
2
Figure 5 : Flat field calibration steps
Notes:
1.
Errors might show up when a sudden peak in intensity is present in the reference scene as the
correction is a low frequency correction.
2.
There might be limits to the total difference that you will be able to correct for. The correction is
often achieved by applying a gain per pixel or pixel segment. If the available gain is not sufficient
to correct for the difference between the weakest and brightest illuminated pixel segment, a flat
field cannot be achieved.
Figure 6 : Uniform light source before vs. after flat field calibration
To summarize, depending on the flat field correction variant, reference images have to be recorded
in dark and in a bright field. Make sure the sensor is really dark when performing a dark field
calibration and performing a bright field calibration in a light intensity range around 40% of the sensor
full scale.
Using the DSNU and PRNU corrections
