Dalsa Linea SWIR GigE Series, Руководство пользователя

Страница: 57 / 136

Linea SWIR GigE Series Camera Operational Reference
•
55
Example User Defective Pixel Map XML File
The following example shows the required components of the defective pixel map file. Each bad
pixel position (relative to the image origin, which is the upper left corner), must be identified by
the XML statement:
<DefectivePixel OffsetX=”
number
” OffsetY=”0”/>
The pixel format (8 or 12-bit) is handled transparently, thus requires no special consideration by
the user. This example XML listing has four “bad” pixels identified.
Image Response Uniformity & Flat Field Calibration
The Flat Field Correction function (FFC) consists of using two coefficients per pixel to correct the
gain and offset of the corresponding pixel. These corrections compensate for Photo-Response Non-
Uniformity (PRNU) and Fixed Pattern Noise (FPN) unique to each camera sensor and the lens
used.
Related Features: flatfieldCalibrationFPN, flatfieldCalibrationPRNU,
flatfieldCorrectionCalibrationAlgorithm, flatfieldCalibrationTarget
It is common to find an image has a lower response at the edges of the camera’s field of view
compared to its center. This is typically the result of a combination of lens vignetting (cos4th)
roll-off and the beam structure of the illumination source. Using a more diffused light may reduce
the roll-off effect. However, if decreasing the lens aperture improves the edge roll-off, then barrel
vignetting (a shadow cast on the sensor by the focus helical or extension tubes) may also be
present.
The camera can compensate for edge roll-off and other optical non-uniformities by activating Flat
Field Correction after the calibration procedure acquires correction coefficients.
<?xml version=”1.0” encoding=”UTF-8” ?>
<!–-Example User Defective Pixel Map -- >
<!-- maximum 512 coordinates -- >
<!–-filename: ExampleBadPixels.xml -- >
<Coordinates>
<DefectivePixel OffsetX=”12” OffsetY=”0”/>
<DefectivePixel OffsetX=”17” OffsetY=”0”/>
<DefectivePixel OffsetX=”103” OffsetY=”0”/>
<DefectivePixel OffsetX=”206” OffsetY=”0”/>
</Coordinates>