Toshiba e-STUDIO 550, Service Manual

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JUNE 2002 © TOSHIBA TEC 8 - 5 e-STUDIO550/650/810 LASER OPTICAL UNIT
(3) f Ø lenses 1 and 2
These two lenses perform the following adjustment on the laser beams 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 scans over the drum surface at a uniform
angular velocity; namely, the pitch between the
dots on the drum is wider at both ends than at
the center of the scanning range. The f Ø lenses
help to correct this difference, making all the
dot-to-dot pitches equal on the drum surface.
b. Face tilt connection
The reflecting face of the polygonal mirror is tilted
slightly to one side against the perfect vertical.
Horizontal deviation of the laser light 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.
Wider
Narrower
Drum
Lens 1
Lens 2
Same intervals
Mirror plane is tilted.
(4) H-Sync detection PC board
The laser light which is started to be scanned from one of the reflected face of the polygonal mirror is
reflected by the H-Sync detection mirror and goes into the PIN diode on the H-Sync detection PC
board. The primary scanning synchronizing signal is generated based on this reflected laser light.
The rudder sensor is attached to the H-Sync sensor to evenly space (42.3µm), by its detection value,
the intervals of the secondary scanning of the first and second beams.
Fig. 8.2-2
Fig. 8.2-3
Deviation