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IMAGE PROCESSING
2.3 AUTO IMAGE DENSITY (ADS)
[A]
Sub scan direction
A193D004.wmf
The auto image density (ADS) mode prevents the background of an original
from appearing on copies.
The copier scans the auto image density detection area [A] as shown in the
diagram. This corresponds to a few mm at one end of the main scan line. As
the scanner scans down the page, the IPU on the BICU detects the peak
white level for each scan line. The IPU determines the reference value for the
A/D conversion for a particular scan line using the peak white level for that
scan line. Then, the IPU sends the reference value data to the reference
controller on the SBU.
When an original with a gray background is scanned, the density of the gray
area is the peak white level density. Therefore, the original background will
not appear on copies. Because peak level data is taken for each scan line,
ADS corrects for any changes in background density while scanning down
the page.
As with previous digital copiers, the user can manually select the image
density when selecting auto image density mode, and the machine will use
both settings when processing the original.
SM
2-7
(A193)
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