INTERMEDIATE TONE PRINTER

PURPOSE:To enable an image of high quality without irregularity of density to be formed, by a method wherein variation of a sub scan speed of a recording medium is detected, and image information is corrected based thereon to drive a light source. CONSTITUTION:A light source 1 such as a laser diode or the like irradiating beam light of a laser or the like and a drive circuit 2 driving a light source 1 based on image information are provided, and an image having gradation property is formed on the recording medium 12 by applying modulated beam light from the light source 1 in a main scan direction A crossing a sub scan direction 14 to the recording medium 12 moving at a sub scan speed. In such an intermediate tone printer a rotary encoder 10 detecting the sub scan speed is established to a rotary axis of a sub scan drum 7. Sub scan information via a line l1 and image information are respectively given to an image correcting means 11 via a line l2. Then, the image information is corrected based on the sub scan speed information, which is given to the laser diode drive circuit 2. The image information is thus corrected according to variation of the sub scan speed.