The laser/scanner system forms a latent image on the photosensitive drum according to the VIDEO signals sent from the SCNT Board. This system consists of the

laser driver circuit, scanner motor, etc. They are integrated into the laser/scanner unit and controlled by the DCNT Board.

The laser scanner unit is illustrated in the figure below and the sequence is described in the following.

Reflective

The laser/scanner unit adopted a "twin beam method" (Note) which scans two lines simultaneously with two laser diodes for high-speed laser scanning with the

motor revs restrained. The operation sequence of the laser/scanner unit is discussed in the following:

1) The DCNT Board rotates the four-sided mirror when a print command is sent from the SCNT Board, and then rotates the scanner motor.

2) When the scanner motor starts to rotate, the DCNT Board emits light from the laser forcefully with the LASER CONTROL signal and then starts to control the

rotation of the scanner motor.

3) The DCNT Board rotates the motor at a specified speed with the SCANNER MOTOR SPEED CONTROL signal.

4) The DCNT Board sends the VIDEO signals to the laser driver circuit after the rotational speed of the motor reaches its target value.

5) The laser driver PCB emits light from the two laser diodes according to these signals.

6) The two laser beams strike the four-sided mirror rotating at a specified speed through the collimator lens and cylindrical lens.

7) The laser beams reflected off the four-sided mirror focus on the photosensitive drum through the focus lens and reflective mirror located in front of the four-sided

mirror.

2-4

shading position

read start position

SCANNER MOTOR

CONTROL signal

Four-sided mirror

Scanner

Focus lenses

mirror

Cylindrical lens

read end position