Toshiba e-STUDIO 200L Service Manual page 199

3) f T lenses-1 and -2
These two lenses perform the following adjustment on the laser beam reflected by the polygonal
mirror.
a. Uniform-velocity scanning
Since the polygonal mirror is rotating at a uni-
form velocity, the laser beam reflected from
the mirror is scanned over the drum surface at
a uniform angle; namely, the pitch between the
dots on the drum is wider at both ends than at
the center of the scanning range. The f T
lenses help to correct this difference, making
all the dot-to-dot pitches equal on the drum
surface.
b. Face tilt correction
The reflecting plane of the polygonal mirror is
slightly tilted to one side against the perfect
vertical. Horizontal deviation of the laser beam
which is caused by the tilt is corrected.
c. Sectional shape of laser beam
The shape of the laser beam spotted on the
drum is adjusted.
4) H-sync signal detection PC board
The laser beam which has started being scanned from one of the reflecting plane of the polygonal
mirror is reflected by the H-sync detection mirror and it enters the PIN diode on the H-sync signal
detection PC board. The primary scanning synchronization signal is generated based on this reflec-
tion.
5) Laser driving PC board (LDR board)
This control board has the following functions:
- APC function (adjusts disparity of the laser intensity caused by temperature)
- Laser emission function
6) Slit glass
The slit glass is located where the laser beam is output from the laser optical unit, and it protects the
unit from dust.
June 2004 © TOSHIBA TEC
fθ Lens-1
Fig.8-5
Mirror plane is tilted.
Fig.8-6
e-STUDIO200L/202L/230/232/280/282 LASER OPTICAL UNIT
8 - 5
Wider
Narrow
Drum
fθ Lens-2
Same intervals
Deviation
8