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Speed control
The speed control maintains the scanner motor rotation at a specified speed.
The following is the sequence of steps performed by the speed control.
1. The DC controller sends the /ACC1 signal to the scanner driver IC at the scanner motor
startup to rotate the motor.
2. The DC controller forces the laser on and monitors the revolutions of the scanner motor
by comparing the intervals between the BD INPUT signal (/BD2I) and the reference clock.
3. When the revolution reaches a specified number of revolutions, the DC controller sends
the /DEC1 signal and decelerates the scanner motor. The DC controller controls the
speed of the scanner motor by sending the /ACC1 or /DEC1 signal afterwards.
Phase control
This control prevents vertical color misregistration. It maintains the scanner motor’s rotation
at a constant speed to eliminate the rotational variations between the lines. This is achieved
by maintaining the phase difference between the two scanner mirrors.
The phase control performs the following steps:
1. When the scanner motor rotates at a constant speed and a specified number of
revolutions under the speed control, the DC controller generates a phase reference
clock based on the reference clock.
2. The DC controller compares the intervals between the phase reference clock and the
BD INPUT signal (/BD2I) with the frequency comparator to detect rotational variations
between the lines.
3. The DC controller controls the rotational variations by sending the /ACC1 signal when
the interval of the /BD2I is slower than the phase reference clock, and sending the /
DEC1 when it is faster than the clock.
Failure detection
The CPU monitors the frequency comparator in the ASIC to check that the scanner motor
rotates at the specified number of revolutions.
Under the following conditions, the CPU judges the optical unit faulty. It stops the printer
engine and notifies the formatter of the failure.
● Abnormal startup: The scanner motor does not enter SCANNER READY period within
five seconds from the start.
● Abnormal rotation: The interval of the /BDI signals goes out of the tolerance while the
scanner motor rotates steadily and it continues until the accumulative length of time
equals approximately 10 mm (0.4 inch) of print distance.
It is a BD error when an abnormal rotation occurs when the image masking control is
released. (The BD error will result when the interval of the /BDI signals goes out of tolerance
even once while the scanner motor rotates steadily and the image masking control is off.)
ENWW Laser/scanner system 145