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.

58 Operational Reference

Genie Monochrome Series-GigE Vision Camera

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Faber M640, M1600, M1024, M1400 user manual Flat Field Image Shading Correction, Flat Field Correction Calibration Procedure