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Camera Performance and Features
Linea2 5GigE Series Camera
A Sapera application (such as CamExpert) creates a new SapBuffer object of the same width as the
sensor but with twice the number of lines. This provides the room to store both offset and gain Flat
Field data. The Flat Field offset data is contained in the top half of the new buffer, while the gain
buffer is in the bottom half.
A Sapera application saves the new buffer using the SapBuffer class Save function with the
"-format tiff" option, which allows saving data without loss of significant bits.
Important Factors about Flat Field Processing
Important:
Before calibration, the Linea2 5GigE should be powered on long enough
to achieve its nominal temperature (a minimum of 30 minutes).
Important:
During calibration, no other Linea2 5GigE features should be accessed or
modified.
Calibration via CamExpert or via a User Application:
Exposure and frame rates
used during a Flat Field Calibration should be similar to the exposure settings used in
the camera application.
Performing an FFC Setup via Sapera CamExpert
The Sapera LT CamExpert tool provides an easy GUI based method for a user to perform a Flat
Field Calibration. The process requires the user to plan acquisitions in dark and bright conditions,
followed by the FFC process itself. These steps are detailed below.
Set up Dark and Bright Acquisitions with the Histogram Tool
Verif
y the camera’s acquisition with a live grab and prepare to grab a flat light image required for
calibration. Ideally, a controlled diffused light source aimed directly at the lens should be used or a
non-glossy paper with the lens slightly out of focus (or evenly lit wall).
If a sheet of material is being used as a white target, it must be completely free of blemishes and
texture. Any dirt or texture present will generate a variation in the image that will be incorporated
into the calibration coefficients of the camera. Once the target is removed, or moved, vertical
stripes will be present in the scanned image. Dirt or texture that has dark characteristics will
appear as bright vertical lines. Dirt or texture that has bright characteristics will appear as dark
vertical lines. One way to minimize this effect is for the white target to be moving during the
calibration process. This has the effect of averaging out any dirt or texture present.
Note the lens iris position for a bright but not saturated image.
Verify a Dark Acquisition
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Cover the lens with the lens cap.
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Using CamExpert, click
Grab
and then
Statistics
.
Figure 16: CamExpert
–
Grab & Statistics Buttons
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In the Statistics dialog, use the
Selected view
drop-down list to select Histogram.
