Teledyne Linea Color GigE LA-GC-02k05B User Manual page 71

2) Height: The closer the average output level is to your calibration target the better. It is okay if
the level is higher than the target, but it is not desirable to be much lower than the target.
Compared to the target, an extremely low output will increase the noise level significantly high
after the PRNU is corrected such that the SNR and/or DNR may not meet your application's
requirements. To avoid this, the profile should reach a level as near the calibration target as
possible.
In order to adjust the profile height the exposure time, light intensity, diaphragm opening (which
may conflict with the flatness), and lens throughput index, etc. are all factors that need to be
considered. The purpose of all these is to enhance the illumination, after all.
3) Matching: The closer the three RGB line profiles are to each other the better. A large
separation between the colors indicates varying noise level between colors. In theory, it is best if
all three profiles match each other. In practice, however, it is not necessary that they overlap
completely, only that you try to get them as close together as possible.
Light in different wavelength ranges can affect the degree of matching. Therefore, the filters being
used in your applications need to be considered.
If, despite the above effort, you still do not meet your goals, it's time to use the gain features. You
may want to use the white balance gains to adjust the peak of each color to a similar DN value,
and use the system gain to adjust the peak intensity of the three colors to the desired DN level.
Keep in mind that changes to gain do not improve the image quality at all from an SNR
perspective. All gains are digital multipliers and, as such, the gain scales up signal and noise
proportionally. Therefore, use this method only as long as the SNR meets your application
requirements.
In conclusion, before you perform the FFC, we recommend that you to try to improve the bare
image quality first. Increasing the output level by enhancing illumination is the preferred method.
You can do this by adjusting gains in the SNR allowable range.
Note that the line profile shown in the above figure is acceptable.
Keep the following in mind:
1. Ensure that camera's temperature is in a stable condition. This may require 30 or more
minutes after power-on.
2. All parameters should meet your application's specifications. If you change parameters after
the FFC is done, then the FFC results many no longer be relevant. When parameters
change, you should consider rerunning the FFC.
The followings are the basic and typical steps to run an FFC:
FPN Correction
In general, you can skip the FPN correction as the camera's factory correction is good enough.
Step 1. Cover the lens (place the sensor in dark).
Step 2. Select Off from the Flat Field Correction Mode drop-down menu and check the line profile /
histogram. If some, or all, of the pixels outputs are zero, then you should adjust the black level
Linea GigE Series Camera Operational Reference • 69