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Verify a Bright Acquisition
Aim the camera at a diffused light source or evenly lit white wall with no shadows falling on it.
Using CamExpert, click on the grab button and then the histogram button. Use the lens iris to
adjust for a bright gray approximately around a pixel value of 200 (for 8-bit pixels). The following
figure shows a typical histogram for a Linea GigE grabbing a bright gray image.
Important: In this example, the average pixel value for the frame is bright gray. Also note that sensors
may show a much higher maximum or a much lower minimum pixel value due to one or more "hot or dead
pixels". The sensor specification accounts for a small number of hot, stuck, or dead pixels (pixels that do
not react to light over the full dynamic range specified for that sensor).
Once the bright gray acquisition setup is done, note the camera position and lens iris position so as
to be able to repeat it during the calibration procedure.
Flat Field Correction Calibration Procedure
The camera calibration contains operations such as FPN (Fixed Pattern Noise) correction, PRNU
(Photon Response Non-uniformity) correction, color correction, etc. The most commonly used
operations are FPN and PRNU corrections. Together they are called Flat Field Correction (FFC).
The goal of camera calibration is to produce a uniform, white balanced, and, if required, color
corrected image at the desired level while imaging a uniform white object along with the user's
application setup.
66 • Operational Reference
Linea GigE Series Camera
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