Characteristics - Canon 1000 Service Manual

n. UCR (under color removal) Processing
Theoretically, mixing Y, M, and C toners in
equal parts should produce black. However, since
neither one of the toners has pure color absorption
characteristics*, mixing the three toners
representing three colors will not produce pure
black.
In this block, the Bk signal is generated based
on the Y, M, and C signals and text signal so that
the reproduction of black can be improved by the
addition of the Bk signal to the Y, M, and C signals.
* See discussions on YMC conversion.
The Bk signal is generated as follows:
The gray components of the YMC signals are
as indicated in Figure 3-333.
These gray components are removed and
replaced with the Bk signal. The replacing
component used here is called an UCR amount,
and in the case of Figure 3-334, the UCR amount is
100%. In such a case, Bk toner will be added to all
density areas, possibly causing fogging in light
areas.
As a remedy, the UCR amount is increased or
decreased with reference to the text signal,
thereby limiting the UCR amount to less than
100%. This processing is executed for each pixel.
COPYRIGHT © 2001 CANON INC. CANON CLC1000/1000S/3100 REV.2 MAY 2001 PRINTED IN JAPAN (IMPRIME AU JAPON)
3. OPERATION AND TIMING
255
Y
Gray component
Figure 3-333
255
Y
UCR
Figure 3-334
255
Y
UCR
Figure 3-335
M
C
M
C
M
C
3-55