Teledyne Linea GigE 2K, User Manual

Page: 59 / 132

Linea GigE Series Camera Operational Reference
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Flat Field Correction Overview
The Flat Field correction function (FFC) consists of using two coefficients per pixel which correct the
gain and offset of the corresponding pixel. These corrections compensate for Photo-response Non-
uniformity (PRNU) and Fix Pattern noise (FPN), unique to each camera sensor.
With CMOS sensors, it is imperative to perform FFC calibration under the same conditions the
camera is to be used in. The exposure time and camera internal temperature need to be similar to
the expected operating conditions, else CMOS sensor variations (over temperature and exposure)
will render the FFC calibration invalid. Linea GigE cameras have multiple FFC user memory spaces
to store calibration data, allowing users to store FFC data for different optimized exposure setups.
The following diagram illustrates the camera’s digital processing chain and associated GeniCam
features.
Video
Output
Video
Digital Processing
(monochrome
)
FPN
correction
PRNU
correction
Offset Gain
To calibrate FPN:
Features: flatfieldCorrectionMode
fflatfieldCalibrationSampleSize
flatfieldCalibrationFPN
To calibrate PRNU:
Features: flatfieldCorrectionMode
flatfieldCalibrationSampleSize
flatfieldCalibrationPRNU
flatfieldCorrectionAlgorithm
flatfieldCorrectionTarget
-
X -/+ X
To set black level offset:
Features: BlackLevel
To set gain:
Features: Gain
Flat Field Correction Algorithm Description
Flat Field Correction Algorithm–Method1 (feature: flatfieldCorrectionAlgorithm) applies the
following FFC formula for correcting pixel values.
newPixelValue[x] = (sensorPixelValue[x] - FFCOffset[x]) * FFCGain[x]
where:
•
[x] is the Flat Field Correction Pixel coordinate.
See the FlatfieldCorrectionPixelXCoordinate features.
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newPixelValue is the pixel value after Flat Field Correction is applied.
•
sensorPixelValue is the pixel value before Flat Field correction is applied.
• FFCOffset is the offset coefficient value to subtract from the sensorPixelValue.
• FFCGain is the gain coefficient value that is multiplied with the sensorPixelValue.
Important: FFCOffset and FFCGain are derived factors calculated from a number of camera
specific feature values (Invisible DFNC features). Reading these values directly from the Flat Field
Coefficients file will be meaningless to the user.
Information on the Sapera Flat Field Coefficients File
The Flat Field Coefficients File is a standard 16-bit TIFF file for both 12-bit and 8-bit acquisition
modes. If the Flat Field calibration is made while using a 12-bit buffer, the user Flat Field
calibration coefficients file is applicable to both 12-bit or 8-bit acquisitions. If the Flat Field