Laser Unit - Sharp AL-1000 Service Manual

(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.
1) Basic structure
The LSU unit is the writing section of the digital optical system.
The semiconductor laser is used as the light source, and im-
ages 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 direc-
tion. The laser emitting PWB is provided with the APC (auto
power control) in order to eliminate fluctuations in the laser
power. The BF PWB works for measurement of the laser writ-
ing start point.
(3)
(2)
(5)
No. Component
(1) Semiconductor laser
(2) Collimator lens
Polygon mirror,
(3)
polygon motor
BD (Mirror, lens,
(4)
PWB)
(5) fθ lens
Makes the laser scanning speeds at both ends of the drum
same as each other.
a ≠ b ≠ c
a b c
(1)
(4)
: Laser beam
path for BF PWB
Function
Generates laser beams.
Converges laser beams in
parallel.
Reflects laser beams at a
constant rpm.
Detects start timing of laser
scanning.
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.)
d = e = f
d e f
θ LENS
f
2) Laser beam path
3) Composition
Effective scanning width: 216mm (max.)
Resolution:
Beam diameter:
Image surface power:
Polygon motor section:
7-3
AL-1000/1010
600dpi
75um in the main scanning
direction, 80um in the sub
scanning direction
0.20 ±0.03mW (Laser
wavelength 780 – 795nm)
Brushless motor 20.787rpm
No. of mirror surfaces: 6 surfaces