Auto Image Density (Ads) - Gestetner B003 Service Manual

6.5.3 AUTO IMAGE DENSITY (ADS)

0 . 5 m m
This mode prevents the background of an original from appearing on copies.
The copier scans the auto image density detection area [A]. This corresponds to a
narrow strip at one end of the main scan line, as shown in the diagram. As the
scanner scans down the page, the IPU on the BICU detects the peak white level
for each scan line, within this narrow strip only. From this peak white level, the IPU
determines the reference value for A/D conversion for the scan line. Then, the IPU
sends the reference value to the A/D 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 down the page.
As with previous digital copiers, the user can select manual image density when
selecting auto image density mode and the machine will use both settings when
processing the original.
SM
Sub scan direction
6-17
IMAGE PROCESSING
[A]
1 5 m m
7 5 m m
B004D550.WMF
B003/B004/B006/B007