Polygon mirror, a scanning apparatus and an image forming apparatus using the same

#1. Field of the Invention

#The present invention relates to an image forming apparatus in which light beams from a light source are radiated onto a photosensitive drum through a rotating polygon mirror to effect an optical scanning, and more particularly, so as to form an electrostatic latent image on the photosensitive drum.

#2. Description of the Prior Art

#This invention may be better understood and its numerous objects and advantages will become apparent to those skilled in the art by reference to the accompanying drawings as follows:

#FIG. 1 shows an overall structure of an image forming apparatus according to the present invention;

#FIG. 2 is a schematic view of an optical system and control of the image forming apparatus of FIG. 1 according to the preset invention;

#FIG. 1 schematically shows a laser beam printer according to the present invention, which comprises a body X having a laser optical system 8. Referring to FIG. 1, code signals sent from an outer system apparatus are input through an interface into a controller 20, where the signals are converted to dot patterns and then to time sequential signals. The converted signals are then introduced to a driver circuit of the laser optical system 8 so as to modulate laser beams generated by a semiconductor laser 30 (see FIG. 2) of the laser optical system 8.

#The modulated laser beams are reflected from a polygon mirror 32 (see FIG. 2) of the laser optical system 8 rotating at a high speed, so as to effect an optical scanning on a photosensitive drum 9 in the direction of the axis thereof. The circumferential surface of the photosensitive drum 9 has been uniformly charged with a certain polarity by means of a charging device 12. This allows an electrostatic latent image to be formed on the surface of the photosensitive drum 9. The electrostatic latent image on the photosensitive drum 9 is then developed by means of a developing device 10.

#The developed toner image on the photosensitive drum 9 is transferred onto a transfer sheet by means of a transfer device 11. The transfer sheet has been transported to the photosensitive drum 9 in a manner detailed below by means of a sheet feed device 14 which comprises a pickup roller 15, a PF roller 16, a PS roller 17 and a PF solenoid 18. The transfer sheet is picked up from a sheet cassette 19 by means of the pickup roller 15 and transported through the PF roller 16 to the position of the PS roller 17, where the transfer sheet is fed to the photosensitive drum 9 synchronously with the rotation of the photosensitive drum 9 so that the transfer sheet overlaps the developed image on the photosensitive drum 9. Toner left on the photosensitive drum 9 after the transfer operation is removed off by means of a cleaning device 13.