KX-MC6020RU, KX-FAP317A, KX-FAB318A - Panasonic Fax Service Manual (repair manual). Page 123

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A laser diode generates the laser beam, and lenses and mirror in the laser scanner direct the beam to the OPC drum. The beam is
made parallel by the collimator lens and is directed at the rotating polygonal mirror, attached with the polygon motor. The polygon
mirror rotates at a constant revolutions approximately 22,000 per minute. This transforms the beam into a horizontally scanning
beam, which is directed through the primary lens, altering the beam’s angular rotation motion into a constant horizontal motion. The
toric correction lens corrects the beam for any vertical misregistration. Next, the beam reflects off of a mirror and passes through a
window where it scans across the rotating OPC drum. At the beginning of each horizontal sweep, the horizontal sync mirror deflects
the laser beam to the horizontal sync sensor. This informs the main board that the laser beam is beginning its horizontal sweep and
that it can begin to modulate the signal with the data to be printed on that line of the image. 

As the OPC drum continues to rotate, it passes by the developer roller. The developer roller is charged to a potential approximately
-200 volts (350 VAC p-p). Toner is attracted to the exposed portions of the OPC drum in reverse proportion to the negative charge.
The greatest amount of toner is transferred to the most positive potential. The developer roller rotates at 1.33 times the speed of the
OPC drum to ensure a constant supply of toner.

Inside each developer is a toner supply roller that rotates in the opposite direction from the developer roller. This supplies a layer of
toner onto the developer roller. The doctor blade smooth and evenly distributes the toner on the developer roller. Gear-driven pad-
dle churn the toner and keep it fluidized and moving towards the developer roller.