User manual

95.08.23.11.29
Color LaserWriter 12/600 PS Basics & Theory 1–32
Laser System
Outline When the /PRNT signal is sent from the I/O controller, the DC
controller performs Automatic Photoemission Control (APC) to stabi-
lize the intensity of the laser beam. Upon completion of APC, the DC
controller generates 8-bit video data signals (
DV2-DV9) in accordance
with the video signals (
VDO0-VDO7) sent by the I/O controller and then
sends them to the PWM-IC in the laser/scanner assembly. According to
the laser drive signal (internal signal in the laser/scanner assembly)
output from the PWM-IC, the laser driver circuit turns the laser diode
on or off to produce the modulated laser beam.
The modulated laser beam is converted to a parallel beam with the
collimator lens and cylindrical lens, and the beam then strikes the scan-
ning mirror, which is rotating at a constant speed.
The laser beam reflected by the scanning mirror focuses on the photo-
sensitive drum after passing through the focusing lens and being
reflected by the reflecting mirror. Since the scanning mirror rotates at a
constant speed, the laser beam scans at a constant speed across the
photosensitive drum which also rotates at a constant speed. As a result,
a latent image is formed on the photosensitive drum.
Example: The laser beam comes on in frame 62 for the magenta layer.
The scanner mirror projects it right to left off the reflecting mirror,
which projects it downward and to the right onto the surface of the
photosensitive drum.
I/O Controller Board
DC Controller Board
/TOP/LSYNC
/BDI
/SCNON
/LSON
BD Mirror
Cylindrical
Lens
Scanning Mirror
Scanner Motor
IMCHR
M1-M8 Dv2-Dv9 /VDOENB
PWM-IC
Reflecting
Mirror
LLCNT
/PRNT
BD Board
PDIN
VDO 0-7
External Device
Laser Driver
Board
Focusing Lens
Photosensitive
Drum
Collimator
Lens
Animation