Toshiba e-STUDIO 4500c, Service Manual

Page: 762 / 1120

LASER UNIT August, 2006
6-46
Optical Path
All four latent images (C, M, Y, K) are written at approximately the same time. The
laser diode turn-on times for each color are timed with drum rotation and paper
feed. Refer to the illustration on the previous page. The optical path for each color
is as follows:
Cylindrical lens (laser beam correction in each LD unit) (Not shown)
↓
Polygon mirror (main scanning line) 4
↓
F
θ
lens (dot position correction)
3
↓
1st Mirror
↓
WTL lens (surface distortion correction) 2
↓
2nd Mirror
↓
3rd Mirror
↓
Dust-shield Glass 10
↓
Drum
Each f
θ
lens has two layers. Because of this, it can correct both beams from the LD
units. Each WTL lens corrects for image distortion.
The polygon mirror turns at high speed. The laser beams are reflected from the
polygon mirror to a pair of mirrors (upper and lower), then to one more mirror and
out to the drum through the dust-shield glass. The polygon mirror has six faces.
The polygon motor rotates at 33,307 rpm for full-color and for black-and-white
copying.
Important: Because of its high rotation speed, the mirror continues to turn for
about 3 minutes after the machine is turned off. Allow enough time for the mirror to
stop before you start to remove the polygon motor.