| 摘要 |
PROBLEM TO BE SOLVED: To irradiate a photoreceptor with plural image light beams without making a device larger, remarkable cost rising and the damage of a photoreceptor, etc. SOLUTION: In this image writing unit 16 arranged to be opposed to the surface of the photoreceptor drum 32, an fθlens 31 arranged in the optical path of a laser beam between a polygon mirror 30 and the drum 22 is moved back and forth between a position shown by a solid line and a position shown by an alternate long and short dash line in figure in directions shown by arrows Y and Y' orthogonal to the optical path direction of the laser beam between the mirror 30 and the drum 22 by a lens oscillating mechanism 33. The moving amount of the lens 31 in the direction shown by the arrow Y or Y' is set to the one that the irradiating position of the laser beam passing through the lens 31 on the surface of the drum 22 is displaced by one line in a subscanning direction. The frequency of the oscillation of the lens 31 is the frequency of several 10 MHz synchronizing with the dot frequency of image data inputted in a laser driving circuit 32.
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