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3. Laser unit
The image data sent from the MCU (image process circuit) is sent to
the LSU (laser unit), where it is converted into laser beams.
A. Basic structure
The LSU unit is the writing section of the digital optical system.
The semiconductor laser is used as the light source, and images are
formed on the OPC drum by the polygon mirror and fθ lens, etc.
The laser beams are passed through the collimator lens, the cylindrical
lens, the polygon mirror, the fθ lens, and the mirror to form images on
the OPC drum in the main scanning direction. The laser emitting PWB
is provided with the APC (auto power control) in order to eliminate fluc-
tuations in the laser power. The BD PWB works for measurement of
the laser writing start point.
4
No
Component
1
Semiconductor laser
Generates laser beams.
2
Collimator lens
Converges laser beams in parallel.
3
CY lens
Converges laser beams onto the
polygon mirror surface.
4
Polygon mirror,
Reflects laser beams at a constant
polygon motor
rpm.
(A four-surfaces polygon mirror is
used.)
5
BD (Mirror, lens,
Detects start timing of laser scanning.
PWB)
6
fθ lens
Converges laser beams at a spot on
the drum.
Makes the laser scanning speeds at
both ends of the drum same as each
other. (Refer to the figure below.)
Makes the laser scanning speeds at both ends of the drum same as
each other.
a ≠ b ≠ c
a
b
3
2
1
6
5
Function
d = e = f
c
d
e
f
f θ LENS
AR-168N/168L OPERATIONAL DESCRIPTIONS 7 - 3
B. Laser beam path
C. Composition
Effective scanning width: 216mm (max.)
Resolution: 600dpi
Beam diameter: 75um in the main scanning direction, 80um in the sub
scanning direction
Image surface power: 0.15 ±0.01mW (Laser wavelength 770 - 795nm)
Polygon motor section: Brushless motor 31,180rpm
No. of mirror surfaces: 4 surfaces
4. Fuser section
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