Xerox 3210 - workcentre b/w laser, Service Manual

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2-16 WorkCentre 3210/3220 Multifunction Printer Service Manual
Theory of Operation
Laser Unit
The Laser Unit is the core part of the WorkCentre 3210/3220 and is controlled
by a video controller. The Laser Unit converts video data received from the
computer into an electrostatic latent image on the surface of the OPC drum.
This is achieved by controlling the laser beam and exposing the surface of the
OPC drum to the laser light. A rotating polygon mirror reflects the laser light
onto the OPC drum. Each face of the mirror produces one scan line. The OPC
drum rotates at the same speed as the paper feeding speed. As the OPC
drum turns, the laser scans, which creates the full page image.
The Horizontal Sync (HSYNC) signal is created when the laser beam from the
Laser Unit reaches the end of the polygon mirror and this signal is sent to the
controller. The controller detects the HSYNC signal to adjust the vertical line
of the image on paper. After the HYSNC signal is detected, the image data is
sent to the Laser Unit to adjust the left margin on the paper.
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