Scanning Laser; Development - Kyocera Mita FS-6750 Service Manual

Operation theory
Electrophotographics system
Figure 4.4 Function of F-theta lenses
Drum

Scanning laser

The laser beam hits one of 5 sides of the polygonal mirror. As the mirror revolves
(at the revolution of 26645.7 rpm), the laser beam reflects off of it and reaches the
charged drum surface in a lengthwise manner.
A pair of (plastic) lenses provides focusing the horizontally sweeping laser beam
onto the drum. As the drum rotates, the laser beam sweeps the entire length of the
drum so that the drumís entire circumference is exposed to the laser beam. The
revolution of the polygon mirror motor and the drum itself is timing-controlled so
that each suc-cessive sweeping of the laser beam produces a 1/600 inch offset. The
printer's controller system continuously turns the laser beam on and off to put a
dot at every 1/600 inch distance horizontally. The diameter of a dot is typically 70 to
80 µm. When KIR is on, the intensity of the beam is switched in four degrees com-
pensating for the smoothed image.
Synchronizing the output data with one scanning line is achieved by the photo sen-
sor provided next to the first mirror. At the beginning of each laser sweeping, the
beam hits the photo sensor which in turn sends a command to the logic controller
for syn-chronization.

Development

The latent image constituted on the drum is developed into a visible image. The de-
veloping roller contains a 3-pole (S-N-S) magnet core and an aluminum cylinder ro-
tating around the magnet core. Toner attracts to the developing roller since it is
pow-dery ink made of black resin bound to iron particles. A magnetized blade posi-
tioned approximately 0.3 to 0.4 mm above the developing roller constitutes a
smooth layer of toner in accordance with the roller revolution.
FS-6750
Secondary f-theta lens
A
B
Primary f-theta lens
Polygon mirror
θ
θ
Laser diode
4-7