Fresa G024, Руководство по обслуживанию

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31 March, 1999 OPTICAL UNIT
2-27
Detailed
Descriptions
2.3.4 APC (AUTO POWER CONTROL)
Circuit
The LD has a built-in photodiode to monitor the laser beam. The output signals
from the photodiode are input to the LD control board, which contains a feedback
circuit to keep the laser beam at a constant intensity.
LD error
The LD control panel detects abnormal laser power output by monitoring the
current flowing in the LD. When the current exceeds 133 mA DC, the LD control
panel issues an error detection signal to the MCU. (SC 42 code is displayed.)
2.3.5 LASER EXPOSURE CONTROL
Laser exposure control enables an equivalent of 256 shades for each of Y, C, M,
and K. This is achieved by a combination of two modulation methods: pulse width
modulation (PWM) and power modulation (PM).
At 600 dpi (if 1-bit mode was selected with the driver), the printer smoothes the
output in the main scan direction by determining whether to place the colored part
of the pixel on the left or on the right.
U 1
E M A
Control signal
+ 5 V
L D E R R
L D O F F
P D
L D
G024D528.WMF