Service manual

Section I: Imagesetter

Functional Analysis 2-17

2.11.1 Laser Diode Mount

The laser diode mount provides the mechanical interface to mount the laser diode

driver module PCB, as well as the laser diodes. Refer to Figure 2-7. This submod-

ule also provides precision x and y translations for module-level bow corrections,

an angle reference in the z direction of the laser diode for beam ellipticity, and

adjustment in the y direction for beam pointing.

This component is factory adjusted and is not ﬁeld replaceable or adjustable. If the

laser diode should fail, the entire SGM must be replaced.

NOTE:

The Laser Diode Driver PCB is not ﬁeld replaceable.

2.11.2 Polarizer

The polarizer consists of a polarized lens. A stepper motor rotates the laser beam

path to provide static control of output beam power. Refer to Figure 2-7. The

polarizer corrects for addressabilty changes and provides additional static exposure

control.

A thin plate of special glass, which internally absorbs light polarized in one direc-

tion, makes up the polarizer. Since the light leaving the laser itself is polarized,

rotation of the plate changes the amount of light absorbed in the glass. A home

position hole passes through an optical sensor to signal that the polarizer is at the

home position. The polarizer motor and sensor are ﬁeld replaceable.

2.11.3 Spot Size Changer

The spot size changer consists of an aperture wheel that is rotated in the laser

beams path by a stepper motor. The changer alters the size of the focused spot at

each addressability. Refer to Figure 2-7. The aperture truncates the beam to pro-

duce the correct size spot for each addressability. The aperture also controls the

shape of the focused, eliptical spot.

The aperture wheel has four (4) different size apertures, one for each addressabil-

ity. The largest aperture is used for 3600 DPI and the smallest for 1200 DPI. Four

cutouts on the edge of the aperture wheel pass through a sensor to position the

aperture to the correct spot size. One cutout, which is different from the other

three, signals that the aperture is at home position (3600 DPI). The aperture motor

and sensor are ﬁeld replaceable.

2.11.4 Spot Forming Lens

The spot forming lens refocuses the beam to a small imaging spot on the drum sur-

face. Refer to Figure 2-7. The lens is the ﬁnal focusing element in the optical system

and consists of a focus lens and mount that directly attach to the SGM base. This com-

ponent is factory adjusted and is not ﬁeld replaceable or adjustable.