31 March, 1999
OPTICAL UNIT
2-25
Detailed
Descriptions
F-theta mirror
The distance to the reflective face of the polygon mirror [A] is different at the center
and at the edges of the OPC belt. The gaps between pixels are longer at the edges
(the beam is sweeping across the belt more quickly).
The F-theta mirror [B] compensates for the differences in the distance to ensure an
equal gap between pixels.
BTL (Barrel Torroidal Lens)
Irregularities in the perpendicular inclination of the mirror faces causes the laser
beam spacing in the sub-scan direction to fluctuate. The BTL compensates for this.
G024D504.WMF
Main scan
L a s e r b e a m
dot
After compensation
Before compensation
G024D505.WMF
Evenly spaced
pixels
[B]
[A]
