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58 • Operational Reference Genie Monochrome Series-GigE Vision Camera
Flat Field (Image Shading) Correction
Image Shading correction, also know as Flat Field Correction is the process of eliminating small gain differences
between pixels in a sensor array. That sensor when exposed to a uniformly lit field will have no gray level
differences between pixels when calibrated flat field correction is applied to the image. The Genie camera stores flat
field correction data until power off or in its user setting state for recall at any time (see "
Power-up Configuration"
on page 32). Flat field correction data is composed of 8 bit gain and 8 bit offset coefficients.
The CamExpert Flat Field Correction tool allows calibrating. saving, and loading the flat field calibration data for
any Genie camera being controlled.
Before performing calibration, verify Genie acquisition with a live grab. Also at this time make preparations to grab
a flat light gray level image, required for the calibration, such as a clean evenly lighted white wall or non-glossy
paper. Note the lens iris position for a white but not saturated image. Additionally check that the lens iris closes well
or have a lens cover to grab the dark calibration image.
Flat Field Correction Calibration Procedure
Calibration is the process of taking two reference images, one of a black field – one of a light gray field (not
saturated), to generate correction data for images captured by Genie. Each sensor pixel data is modified by the
correction factor generated by the calibration process, so that each pixel now has an identical response to the same
illumination.
Start the Flat Field calibration tool via the CamExpert menu bar:
Pre-processing • Flat Field Correction • Calibration.
Flat Field Calibration Window
The Flat Field calibration window provides a three step process to acquire two reference images and then save the
flat field correction data for the Genie used. To aid in determining if the reference images are valid, a histogram tool
is provided so that the user can review the images used for the correction data.