Ricoh VT3500, Руководство по обслуживанию

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9.3.2 MTF Correction
When the original image is converted to electrical signals by the CCD, the
signal deteriorates and contrast is reduced. This is because neighboring
black and white parts of the image influence each other. The lens’
characteristics are the main reason for this. This phenomenon is typical when
the width and spacing of the black and white areas are narrower. The ratio of
the difference between the black and white levels of the electrical signal (an
actual difference) and the difference between that of the original (an ideal
difference) is called the Modulation Transfer Function (MTF).
If the MTF is too low, edges of the image tend to be lost. In this model, the
MTF correction is used to emphasize 6-bit image data in the line mode. This
helps to better reproduce characters.
A target pixel datum is compared with the surrounding pixel data and is
compensated. If the surrounding pixels are very different (compared with the
target pixel) then the target value will be more influenced by them. This step
is repeated for all pixels of the original.
[Image]
Black
Black
White
White
CCD
Output
A
B
[Ideal Signal]
[Actual Signal]
B
A
x 100
=
MTF%
1 December 1993
2-107