200 CONTENTS
Figure 4: Image corrections: Offset histogram
Figure 5: Image corrections: Dark current
20.3.1.3 Flat-Field Correction
Each pixel of a sensor chip is a single detector with its own properties. Particularly, this pertains to the sensitivity
as the case may be the spectral sensitivity. To solve this problem (inlcuding lens and illumination variations), a plain
and equally "colored" calibration plate (e.g. white or gray) as a flat-field is snapped, which will be used to correct
the original image. Between flat-field correction and the future application you must not change the optic. To reduce
errors while doing the flat-field correction, a saturation between 50 % and 75 % of the flat-field in the histogram is
convenient.
MATRIX VISION GmbH
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