Printhead - Lexmark MS81x Service Manual

Printhead

The printhead scans the photoconductor drum surface with a laser beam. It consists of four components: laser diode
(LD) card assembly, printhead motor, polygon mirror, and the start of scan card assembly.
1
LD card assembly—The LD card assembly generates the laser beam. The beam is turned on or off according to a
print data signal coming from the controller board.
2
Printhead motor/polygon mirror—The polygon mirror is mounted to the shaft of the printhead motor, and is
rotated at a high speed by the printhead motor. The mirror rotation shifts the incidence and reflection angles of a
laser beam to scan the photoconductor (drum) in a single direction. The laser beam reaches the polygon mirror as
it passes through multiple lenses, mirrors, and windows. The laser beam then arrives at the photo conductor (drum)
surface.
3
SOS card assembly—When a laser beam hits the SOS sensor on the SOS card assembly, the beam is converted to
an electrical signal (SOS signal), and detects the initial position where a scan starts on each line.
Appendix C: Theory of operation
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