The Laser Scanner; Figure 5-6 The Laser Scanner - Tektronix Phaser 550 Service Manual

The laser scanner

Lenses and mirrors in the laser scanner direct the beam at the photoconductive
belt. The beam originates at a laser diode. The beam is made parallel by the
collimator lens and is directed at the rotating polygonal mirror. The mirror
rotates at a constant 23,000 revolutions per minute. This transforms the beam
into a horizontally scanning beam, which is directed through a f- Θ primary lens,
which alters the beam's angular rotation motion into a constant horizontal
motion. The beam then passes through a toric correction lens, which corrects the
beam for any vertical misregistration. The beam then reflects off of a mirror and
passes through a window where it scans across the rotating photoconductive
belt. At the beginning of each of its horizontal sweeps, the horizontal sync
mirror deflects the laser beam to the horizontal sync sensor. This alerts the
engine control board that the laser beam is beginning its horizontal sweep and
that it can begin to modulate the signal for the data to be printed on that line of
the image.
Horizontal
sync mirror
Photo-conductive
belt

Figure 5-6 The laser scanner

Laser diode
Collimator lens
Theory of Operation
Rotating
mirror
f-0 primary
lens
Toric
correction
lens
Horizontal
sync sensor
Mirror
Window
9013-16
Service Manual 5-9
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