Kyocera Mita KM-1505 Service Manual page 144

1
2
1 Laser diode: Generates the laser beam which forms a latent image on the drum.
2 Collimator lens: Collimates the diffused laser beam emitted from the laser diode to convert it into a cylindrical beam.
3 Cylindrical lens: Shapes the collimated laser beam to suit the printing resolution.
4 Polygon mirror: Six-facet mirror that rotates at approximately 25984 rpm with each face reflecting the laser beam
toward the drum for one main-direction scan.
5 Fθ lens: Corrects for non-linearity of the laser beam scanning speed on the drum surface, keeps the beam diameter
constant and corrects for the vertical alignment of the polygon mirror to ensure that the focal plane of the laser beam
is on the drum surface.
6 BD sensor mirror: Reflects the laser beam to the BD sensor to generate the main-direction (horizontal) sync signal.
7 BD sensor: Detects the beam reflected by the BD sensor mirror, outputting a signal to the main PCB (MPCB) to
provide timing for the main-direction sync signal.
The dimensions of the laser beam are as shown in Figure 2-1-9.
Scanning in the main direction is provided by the rotating polygon mirror, while scanning in the auxiliary direction is
provided by the rotating drum, forming a static latent image on the drum.
The static latent image of the letter "A", for example, is formed on the drum surface as shown in Figure 2-1-10. Electrical
charge is dissipated on the area of the drum surface irradiated by the laser.
The focal point of the laser beam is moved line by line, and adjacent lines slightly overlap each other.
µ m
+20
75
-10
Figure 2-1-9
6
7
3
4
Figure 2-1-8 Laser scanner unit (2)
µ m
+25
80
–15
Drum
5
Main scanning direction
Auxilary scanning direction
:laser beam is on
Figure 2-1-10
2BT
2-1-9