Laser Exposure Section - Toshiba e-STUDIO170F Service Manual

5.3.3

Laser Exposure Section

Laser exposure is the process of creating an invisible static charge image on the drum by the laser
beam emitted from the laser exposure section (LSU).
Start sensor Laser diode
fθ lens-1
Polygonal motor
( Polygonal mirror )
LSU
fθ lens-2
Drum
Fig.5-7
The laser scanner area consists of the laser diode part, polygonal motor and mirror.
The laser diode part generates a laser beam according to the laser diode drive signal sent from the
main PBA. The laser beam is made into parallel rays through the collimator lens and then passes
through the cylinder lens. A laser beam of parallel rays is sent to the polygonal mirror face. The laser
diode part checks the current value flowed to the laser diode by each line to keep the laser beam vol-
ume stable. The polygonal part consists of the polygonal motor and polygonal mirror. The polygonal
motor turn the polygonal mirror at a uniform rate for laser beam scanning. The laser beam generated in
the laser diode part is sent to the reflecting part of the polygonal mirror. The Fθ lens 1, 2 and reflecting
mirror bend the optical path of the laser beam and then the beam is focused on the drum.
As the polygonal mirror turns at a uniform rate, the laser beam scans on the drum at a uniform rate.
This operation forms the image on the drum surface like a television.
The laser beam is also sent to the start sensor by the polygonal motor and polygonal mirror. Each time
the start sensor receives the laser beam, it sends a signal to the main PBA. The main PBA uses this
signal to determine the print start position of each line.
e-STUDIO170F Mechanical Description January 2005 © TOSHIBA TEC
5 - 10