Optical image forming device having a plurality of drawing beams and a monitoring beam

摘要

An optical image forming device includes a scanning lens for scanning, in a main scanning direction, eight drawing beams on an image plane. A monitoring beam is scanned repeatedly and simultaneously with the drawing beams in a predetermined scanning range. The eight drawing beams are scanned such that drawing beams adjacent each other in a sub-scanning direction pass a same position in the scanning range on the image plane at a different time. The monitoring beam is scanned prior to scanning of the drawing beam. A scale clock generator is provided for generating scale clock signals identifying positions of the monitoring beam in the scanning range. A modulator modulates the eight drawing beams such that modulations for each of the drawing beams at a same position in the scanning range are synchronized with a timing of a same scale clock signal obtained by the scale clock generator.