4-9
FS-1900
Figure 4-1-7 F-theta lens
Primary f-theta lens
Laser diode
Polygon mirror
Secondary f-theta lens
Drum
Laser beam
Name Description
5 Primary f-theta lens See figure 4-1-7 below.
6 Secondary f-theta lens The primary (above) and secondary f-theta lenses equalize
focusing distortion on the area on the drum closer to the edge. The
effective length of line (A, B in the figure below) the laser beam draws
on the drum becomes longer as the laser beam hits closer to the drum
edge. In the figure 4-1-7 below, distances represented by A and B
are not the same (A > B) until the f-theta lenses are provided
between the polygon mirror and the drum (A = B).
7 Diversion mirror Diverts the laser beam vertically onto the drum. Note the diffused
laser beam finally pinpoints on the drum.
8 Protective glass Prevent dust, debris, etc., from entering the scanner assembly.
9 Sensor mirror Bends the very first shot of a laser scan towards the pin photo
sensor (See figure 4-1-6).
0 Pin photo sensor When shone by the sensor mirror above, this pin photo sensor
generates a trigger signal.
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