Xerox PHASER 3124 Service Manual page 102

General Procedures and Information
LSU (Laser Scanning Unit)
The LSU unit is controlled by a video controller. It scans video data received from the video con-
troller with a laser beam by using the rotation principle of the polygon mirror to create the latent
image on the OPC drum. This is a core part of a laser beam printer.
The OPC drum rotates at the same speed as the paper being fed. The Phto Diode creates a
HSYNC signal and sends it to the engine when the laser beam of the LSU reaches the end of each
horizontal scan line. The engine detects the HSYNC signal and arranges the vertical line of the
image on to paper. After detecting the HSYNC signal, the image data is sent to the LSU to set the
margin on the paper. Each side of the polygon mirror represents one line of scanned data.
Figure 2 LSU
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