Four Beam Laser Writing - Gestetner A294 Service Manual

LASER EXPOSURE

2.4.4 FOUR BEAM LASER WRITING

A294D102.WMF
This laser unit has four LD diodes for writing the image. This means that each
surface of the polygonal mirror motor writes four main scan lines, and 24 main scan
lines are produced when the polygonal mirror rotates once. Due to this multi beam
writing, the polygonal mirror motor speed can be reduced, thus the noise
generated by the polygonal mirror motor can be reduced.
The four laser beams are transferred to the polygonal mirror through a collimating
lens. When the four laser beams arrive on the drum surface, the diameter of the
beam spot is 50 x 60 (main scan direction x sub scan direction) µm, and the
distance between each pixel is approximately 42 µm. So the beam spots overlap
each other as shown above.
The laser diode array is assembled and adjusted in the factory, and no adjustment
can be done in the field.
A294/A295
CÓPIA NÃO CONTROLADA
2-36
CÓPIA NÃO CONTROLADA
ch1
ch2
Main Scan
ch3
ch4
Sub Scan
A294D500.WMF
SM