LASER BEAM DEFLECTION DEVICE

摘要

PURPOSE:To reduce the size of a rotary polygonal mirror and to lower the rotating speed by reflecting the exit light from the rotary polygonal mirror which equally divides a laser beam in a prescribed reflecting part so as to be made incident again to the rotary polygonal mirror and executing plural times of deflection scanning during respective one scanning cycle divided by the number of faces of the rotary polygonal mirror. CONSTITUTION:A sectorial optical path-parallel optical path converting means 21 is provided on the reflection deflecting optical path obtd. by incidence of a laser beam l1 to the rotary polygonal mirror 10. The reflection deflecting scanning beam l2 spreading in a sectorial shape is converted to collimated scanning beams l3 by this converting means 21. The beams l3 are divided to the deflecting ranges of two regions and the collimated scanning beams in the respective divided ranges are reflected and turned back respectively by 1st and 2nd reflecting parts 22a and 22b or 23a and 23b. The turned back beams are returned to the sectorial deflection scanning beams by the converting means 21 and are made incident again to the mirror 10. Plural times of the deflection scanning are executed during the respective one scanning cycle divided by the number of faces of the mirror 10. The size of the rotary polygonal mirror is reduced in this way and the rotating speed thereof is lowered.