Laser Exposure System; Overview/Configuration; Overview - Canon LBP3250 Series Service Manual

2.3 LASER EXPOSURE SYSTEM

2.3.1 Overview/Configuration

2.3.1.1 Overview

The laser exposure system forms static latent images on the photosensitive drum according to the VIDEO signals sent from the main controller, and is comprised
of the laser driver and scanner motor, etc. There are controlled by the engine controller. The following is the outline.
BD sensor
Laser unit
The operational sequence of the laser scanner unit is described below.
1) When the Main controller sends print instruction command, the Engine controller rotates the Four-faced mirror, causing the Scanner motor to rotate.
2) When the Scanner motor starts to rotate, the Engine controller emits the laser forcibly using the Laser control signal, causing the Engine controller to start rotation
control for the Scanner motor.
3) The Engine controller controls to keep a constant speed of rotation of the Scanner motor using the Scanner motor speed control signal.
4) After the rotation speed of the Scanner motor reaches its target, the Main controller sends VIDEO signals to the Laser driver PCB.
5) The Laser driver emits laser diode according to these signals.
6) The laser beam passes through the collimator lens and the cylindrical lens and enters the Four-faced mirror rotating at a constant speed.
7) The laser beam reflected by the Four-faced mirror is focused on the Photosensitive drum via the image-forming lens at the front of the Four-faced mirror.
8) When the Four-faced mirror rotates at a constant speed, the laser beam on the Photosensitive drum is scanned on the Photosensitive drum at a constant speed.
9) When the Photosensitive drum rotates at a constant speed and the laser beam is scanned on the Photosensitive drum at a constant speed, latent images are formed
on the Photosensitive drum.
Cylindrical lens
Collimator
lens
Four-faced mirror
Engine Controller
Main controller
Photosensitive drum
Focus lens
Scanner motor unit
F-2-2
Chapter 2
0019-9509
2-3