Patent ID: 7379221

Claim:
A laser scanner comprising: laser beam emission means for alternately emitting a first laser beam and a second laser beam, each beam being emitted in correspondence with an input image signal of an alternate main-scanning line; a first torsion mirror to reflect said first laser beam emitted from said laser beam emission means to scan the first laser beam on a photosensitive member; and a second torsion mirror to reflect said second laser beam emitted from said laser beam emission means to scan the second laser beam on the photosensitive member, wherein said first and second torsion mirrors perform a reciprocal torsion movement in mutual opposite phases in synchronization with each other, so that the first laser beam reflected by said first torsion mirror and the second laser beam reflected by said second torsion mirror scan on the photosensitive member in opposite main-scanning directions at a time, wherein the first and second laser beams reflected from said respective first and second torsion mirrors are emitted alternately by one main-scanning line by alternately performing scanning of the first laser beam reflected by said first torsion mirror on the photosensitive member in a main-scanning direction while said first torsion mirror performs a forward movement but said second torsion mirror performs a backward movement, and scanning of the second laser beam reflected by said second torsion mirror on the photosensitive member in the same main-scanning direction while said first torsion mirror performs a backward movement but said second torsion mirror performs a forward movement, and wherein said the first and second torsion mirrors reciprocate in synchronism in opposite directions about a same rotational axis.