Mtf Correction - Ricoh C217 Service Manual

8.2.1 MTF Correction

When the original image is converted to electrical signals by the CCD, the
contrast is reduced. This is because neighboring black and white parts of the
image influence each other due to lens characteristics. This phenomenon is
typical when the width and spacing of the black and white areas are
narrower.
MTF correction counters this phenomenon and emphasizes image detail.
The value of a target pixel is modified according to the value of surrounding
pixels. The modified data is compared to the threshold level. This determines
if the pixel is to be black or white.
Sub Scan
E = 2E – 1/2(D + F) ------ Main Scan Data Modified
2
E = 2E – 1/2(B + H) ------ Sub Scan Data Modified
1
The modified data is compared to a threshold level to determine if the pixel is
black or white.
Modified Data E
Modified Data E
SM
Main Scan
I H G
F E D
C B A
≥ 8.0 or Data E
2
< 8.0 and Data E
2
2-47
≥ 8.0 ----- Black
1
< 8.0 ----- White
1
C217