Laser Scanning - Mita DP-2800 Service Manual

5A2

Laser scanning

The laser beam hits one of ten polygonal mirrors. As the mirror revolves (at the nominal
revolution of 17,700 rpm), the laser beam reflects off of it and reaches the charged drum
surface in a lengthwise manner.
A pair of (plastic) lenses provides focusing the horizontally sweeping laser beam onto the
drum. As the drum rotates, the laser beam sweeps the entire length of the drum so that the
drum's entire circumference is exposed to the laser beam. The revolution of the polygon
mirror motor and the drum itself is timing-controlled so that each successive sweeping of
1
the laser beam produces a / inch offset. The printer's controller system continuously
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1
turns the laser beam on and off to put a dot at every / inch distance horizontally.
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Synchronizing the output data with one scanning line is achieved by the photo sensor
provided next to the first mirror. At the beginning of each laser sweeping, the beam hits the
photo sensor which in turn sends a command to the logic controller for synchronization.
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