Service manual

5.2.4
F-theta Lenses and the BTL
The angles between pixels are equal. However, if the beam were to go
directly to the drum as shown in the upper illustration, the spacing between
pixels would differ with the angle of the beam. The pixels near the end of the
drum would be further apart than those near the middle of the drum. The
pixels would also be slightly thicker toward the ends of the drum than in the
middle.
The f-theta lenses [A] and BTL [B] correct for this by deflecting the beam
slightly inward to ensure uniform picture element spacing and diameter. The
f-theta lenses and BTL also correct for irregularities in the polygon mirror
face, focusing irregular beams onto the correct part of the drum.
[B]
Wide spaced
Narrow spaced
Evenly
spaced
pixels
[A]
LASER EXPOSURE
A166/A187/A189 2-68 SM
CÓPIA NÃO CONTROLADA
CÓPIA NÃO CONTROLADA