Scanning optical system

A scanning optical system that emits at least two beams to a plurality of surfaces to be scanned, comprising:

• a polygonal mirror that is rotated about a rotation axis thereof to deflect the at least two beams simultaneously to scan in a main scanning direction, the at least two beams incident on said polygonal mirror along a plurality of optical paths arranged symmetrically with respect to a plane perpendicular to said rotation axis;
• and
• an imaging optical system that converges the at least two beams deflected by said polygonal mirror on the plurality of surfaces to be scanned,
• said imaging optical system including a plurality of lenses, each of said plurality of lenses converging an incident beam, in an auxiliary scanning direction which is perpendicular to the main scanning direction, on a corresponding surface to be scanned, the at least two beams deflected by said polygonal mirror passing through said plurality of lenses, said plurality of lenses having the same shapes and being arranged symmetrically with respect to the plane, an orientation of lenses of said plurality of lenses receiving beams proceeding along optical paths arranged on one side of said plane being oriented oppositely by 180° rotation, in the auxiliary scanning direction, to the other lenses receiving beams proceeding along optical paths arranged on the other side of said plane.

A scanning optical system that emits an even number of beams to a plurality of surfaces to be scanned, comprising:

• a polygonal mirror that is rotated about a rotation axis thereof to deflect the even number of beams simultaneously to scan in a main scanning direction, the even number of beams incident on said polygonal mirror along a plurality of optical paths arranged symmetrically with respect to a plane perpendicular to said rotation axis;
• and
• an imaging optical system that converges the even number of beams deflected by said polygonal mirror on the plurality of surfaces to be scanned,
• said imaging optical system including an even number of lenses, each of said even number of lenses converging an incident beam, in an auxiliary scanning direction which is perpendicular to the main scanning direction, on a corresponding surface to be scanned, the even number of beams deflected by said polygonal mirror passing through said even number of lenses, said even number of lenses having the same shapes and being arranged symmetrically with respect to the plane, an orientation of lenses of said even number of lenses receiving beams proceeding along optical paths arranged on one side of said plane being oriented oppositely by 180° rotation, in the auxiliary scanning direction, to the other lenses receiving beams proceeding along optical paths arranged on the other side of said plane.

A scanning optical system that emits an even number of beams to a plurality of surfaces to be scanned, comprising:

• a polygonal mirror that is rotated about a rotation axis thereof to deflect the even number of beams simultaneously to scan in a main scanning direction, the even number of beams incident on said polygonal mirror along a plurality of optical paths arranged symmetrically with respect to a plane perpendicular to said rotation axis;
• and
• an imaging optical system that converges the even number of beams deflected by said polygonal mirror on the plurality of surfaces to be scanned,
• said imaging optical system including a plurality of lenses, each of said plurality of lenses converging an incident beam, in an auxiliary scanning direction which is perpendicular to the main scanning direction, on a corresponding surface to be scanned, the even number of beams deflected by said polygonal mirror passing through said plurality of lenses, said plurality of lenses having the same shapes and being arranged symmetrically with respect to the plane, an orientation of lenses of said plurality of lenses receiving beams proceeding along optical paths arranged on one side of said plane being oriented oppositely by 180° rotation, in the auxiliary scanning direction, to the other lenses receiving beams proceeding along optical paths arranged on the other side of said plane.