Gestetner A294, Service Manual

Page: 86 / 600

LASER EXPOSURE
A294/A295 2-36 SM
2.4.4 FOUR BEAM LASER WRITING
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)
µ
m, and the
distance between each pixel is approximately 42
µ
m. 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.
A294D102.WMF
c h 1
c h 2
c h 3
c h 4
Main Scan
S u b S c a n
A294D500.WMF
CÓPIA NÃO CONTROLADA
CÓPIA NÃO CONTROLADA