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IMAGE PROCESSING
W h i t e
Correction
Black
Correction
The shading circuit corrects the video signal for each pixel obtained during image
scanning as follows:
(Video data for each pixel) – (Black shading data for each line)
(White shading data for each pixel) – (Black shading data for each line)
The white shading data is updated before every first scanning (2C and 4C mode)
or every scanning (1C mode). The black shading data is updated every scan line.
The white shading data is used to correct the image data for irregularities in the
CCD and in the optics across the main scan. The black shading data is used to
correct the image data for any changes in black level with time, while the machine
scans down the page.
(2) Main Scan Timing
The shading circuit generates the CCD timing signals, and the timing signals for
feeding back the black and white level data from the shading circuit to the Analog
ASIC.
(3) Sub-scan Timing
The shading circuit also generates the synchronization signal for scan line
correction (see the next page for details on this process).
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24 February, 1999
A259X005.WMF
X 1023
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