LASER UNIT August, 2006
6-44
6.7.2 LD UNIT
There is an LD unit for each color, and each LD unit uses a two-beam system. A
photo diode (PD) in each LD unit detects the light emitted from the LD unit. The
output of the PD is fed back to the LD control board. The LD control board uses
this information to control the amount of light to make sure that it remains at the
correct level.

Dual Beam Writing

In each LD unit, two beams move across the drum in the main scan direction.
The use of two beams does the following:
• Lets the machine print quickly
• Reduces the number of turns of the polygon mirror for a page, which gives the
motor a longer life.
• Reduces the amount of noise from the motor.
The beam pitch is fixed at 600 dpi and is not adjustable.

LD Safety Switches

To ensure the safety of customers and service engineers, two switches inside the
cover prevent the laser beams from switching on accidentally. When the front door
is open, the 5V line connecting each LD driver on the LD control board is
disconnected.
PSU: Power Supply Unit
BICU: Base-engine Image-processing Control Unit
LDB: LD Drive Board (included in the LD Unit)
Front Door Switch Unit
(Upper Left)
+5 V
BICU
PSU
LD Driver IC (Y)
LDB (Y)
SW 2SW 3
LD Driver IC (C)
LDB (C)
LD Driver IC (M)
LDB (M)
LD Driver IC (K)
LDB (K)
B132D900.WMF