FS-6020
2-1-9
2-1-3 Laser scanner unit section
(1) Laser scanner unit
Print data is processed as the image data by the main PWB and sent to the laser scanner unit (LSU). The laser scanner
unit forms the electrostatic latent image on the drum surface by turning on/off the laser light according to the image data.
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Figure 2-1-13 Laser scanner unit
1. Laser diode .................................................. Emits the diffused invisible light laser.
2. Collimator lens ............................................. Changes the diffused laser light to the parallel light.
3. Cylindrical lens............................................. Corrects the vertical angle when the laser light hits the one surface of
polygon mirror.
4. Polygon motor.............................................. Polygon motor has a 6 face mirror. Individual mirror corresponds to the
width of scan lines on the drum that is scanned by the laser light.
5. f-θ main lens ................................................ See f-θ sub lens as follows.
6. f-θ sub lens .................................................. The main and sub f-θ lenses equalize the focus distortion caused
around the edge of drum. The effective length drawn (Fig.2-1-14 A and
B on the next page) on the drum by the laser light is longer as the laser
reaches further to the end of the drum and then the distance shown by
A and B are not identical (A>B). These distances can be equal by
positioning the f-θ lens between the polygon mirror and the drum. (A=
B)
7. Direction change mirror ............................... Changes the direction so that the laser light beams to the drum
vertically. Diffused laser light now accurately can beam to the drum.
8. Protective glass ........................................... Prevents dust and dirt from entering the laser scanner unit.
9. SOS lens...................................................... Bents the first shot of laser scanning to the pin photo sensor direction.
10. Pin photo sensor .......................................... Receives the laser light through the SOS lens as mentioned above and
then outputs as the horizontal synchronous signal.
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