Canon LBP-1260, Руководство по обслуживанию

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CHAPTER 2
2. Control of laser beam intensity (APC
control)
The CPU performs automatic power control
of the laser diode to make the laser
diode emit constant light. This control can
be
Into two types: initial APC and
between-page APC.
The CPU then changes the APCOS
signal
adjustment), compares the
input value of the signal with
the target value, and optimizes the
intensity of the laser beam.
a. Initial APC
APC is performed to increase the
intensity of the laser beam from zero to
the target value during initial rotation,
The CPU sets the FORCIBLE LASER
ON signal to and at the
same time the CPU changes the APCOR
signal (coarse adjustment) and lets the
APCOUT signal gradually
from
low value. As the laser current
increases, the laser diode
begins
emitting light.
The intensity of the laser diode
output is detected by the photodiode
After amplification, the output
voltage is fed back to the CPU as the
AUTOMATIC POWER CONTROL INPUT
signal
The C P U c o n t i n u e s coarse
adjustment the input value of the
APCIN signal reaches 70% of the target
value stored In the CPU. The CPU then
does fine adjustment with the APCOS
signal. and ends the initial APC when
the input value of the
has
become almost equal to the target
value.
b. Between-page APC
Between-page APC is performed after
Initial APC, and when printing is not
being performed while waiting for the
next page to proceed to the printing
area. to correct variations in the
intensity of the laser printing.
Between-page is also performed
during the unblinking period, described
later, to prevent the laser beam from
writing on the image area of the
photosensitive drum.
The CPU sets the
signal used by and not
output externally) to and sets the
FORCIBLE LASER ON signal to
“L”.
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