PURPOSE: To attain an optical scanning mechanism improving the printing quality and simplifying/quickening the processing for magnification and reduction, by providing a lens system for magnification and reduction of printed pattern to a one-dimensional optical array for changing the magnification (m) and adopting the system changing the dot diameter proportional to the printed pattern.

CONSTITUTION: An optional magnification signal (m) is set to a magnification control circuit 12, the output drives a magnification control motor 4 via a magnification motor driving circuit 8 and a zoom lens 3 is adjusted so as to obtain the desired magnification (m). The magnification output is inputted to a video modulation circuit 10 to control the modulating frequency (f) of a video signal, and inputted to a dimmer circuit 11 to control an irradiating output P0 giving a brightness of the optical array 2. Further, the output is inputted to a drum motor driving circuit 9 to control a speed (v) in the sub-scanning direction. The controlled modulation frequency (f) and the irradiated output P0 are given to the optical array 2 via an LED array driving circuit 7 to attain the lighting corresponding to the magnification (m). Further, the controlled speed (v) is given similarly to the drum motor 6 to drive a photoreceptor drum 1.