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PROCESS
[8] Cylindrical Lenses
Two lenses, cylindrical lens 1 (Cy1) and cylindrical lens 2
(
Cy2
), are used to eliminate the tilt error of the polygon mirror.
Cylindrical lenses 1 and 2 are installed before and after the
polygon mirror, as shown in Fig.21. The laser beam is focused
on the polygon mirror by means of cylindrical lens 1, and the
light reflected off the polygon mirror is once again focused on
the drum by means of cylindrical lens 2.
The optical relationship between the polygon mirror and the
drum face with respect to cylindrical lens 2 is that of image and
object. Consequently, even if the polygon mirror is tilted, the
light path is corrected by cylindrical lens 2, ensuring that the
beam is scanned along the same line.
[9] Index Sensor
This sensor is intended to determine the leading edge write
position for each scan in the axial direction of the drum, and
also to determine the positions of the two beams.
Fig.21
Cylindrical lens
1 (Cy1)
Collimator lens Cylindrical lens
2 (Cy2)
Polygon
mirror
f
θ
lens
Mirror
Drum
Semiconductor
laser
PROCESS-1
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