Optical scanning device and image forming apparatus using the device

An image forming apparatus comprising:

• an even number of photoconductors;
• and
• an optical scanning device configured to simultaneously scan surfaces of the even number of photoconductors to form latent images thereupon, respectively, wherein the optical scanning device includes:
• a housing;
• a rotating deflecting device arranged substantially at a center in the housing to deflect optical beams;
• and
• a plurality of scanning optical systems respectively corresponding to the even number of photoconductors, arranged to be substantially symmetrical with the rotating deflecting device as a symmetry center, the plurality of scanning optical systems each including a plurality of folding-back mirrors and at least one long lens having power in a sub-scanning direction and configured to correct a scanning line deviated in the sub-scanning direction, respectively, and the pluralities of folding-back mirrors and at the least one long lenses of the symmetrically arranged scanning optical systems being arranged to be symmetrical to each other with the rotating deflecting device as the symmetry center, respectively,
• wherein the surfaces of the even number of photoconductors are simultaneously scanned with optical beams output from the plurality of scanning optical systems and deflected by the rotating deflecting device, and
• wherein in each of the symmetrically arranged scanning optical systems, a same number of folding-back mirrors is arranged downstream of the at least one respective long lens in a direction in which an optical beam deflected by the rotating deflecting device travels, and
• wherein the at least one long lens included in one of the symmetrically arranged scanning optical systems is arranged upside down in a scanning plane relative to the at least one long lens included in another one of the symmetrically arranged scanning optical systems.

A process cartridge for use in an image forming apparatus, the process cartridge comprising:

• an even number of photoconductors;
• and
• an optical scanning device configured to simultaneously scan surfaces of the even number of photoconductors to form latent images thereupon, respectively,
• wherein the optical scanning device includes:
• a housing;
• a rotating deflecting device arranged substantially at a center in the housing to deflect optical beams;
• and
• a plurality of scanning optical systems respectively corresponding to the even number of photoconductors, arranged to be substantially symmetrical with the rotating deflecting device as a symmetry center, the plurality of scanning optical systems each including a plurality of folding-back mirrors and at least one long lens having power in a sub-scanning direction and configured to correct a scanning line deviated in the sub-scanning direction, respectively, and the pluralities of folding-back mirrors and the at least one long lenses of the symmetrically arranged scanning optical systems being arranged to be symmetrical to each other with the rotating deflecting device as the symmetry center, respectively,
• wherein the surfaces of the even number of photoconductors are simultaneously scanned with optical beams output from the plurality of scanning optical systems and deflected by the rotating deflecting device, and
• wherein in each of the symmetrically arranged scanning optical systems, a same number of folding-back mirrors is arranged downstream of the respective at least one long lens in a direction in which an optical beam deflected by the rotating deflecting device travels, and
• wherein the at least one long lens included in one of the symmetrically arranged scanning optical systems is arranged upside down in a respective scanning plane relative to the at least one long lens included in another one of the symmetrically arranged scanning optical systems.

A method of making an optical scanning device for scanning surfaces of an even number of photoconductors simultaneously, the method comprising:

• arranging a rotatable optical beam deflecting device substantially at a center in a housing;
• and
• arranging a plurality of scanning optical systems respectively corresponding to the even number of photoconductors to be substantially symmetrical with the optical beam deflecting device as a symmetry center, the plurality of scanning optical systems including a plurality of folding-back mirrors and at least one long lens having power in a sub-scanning direction and configured to correct a scanning line deviated in the sub-scanning direction, respectively, and the pluralities of folding-back mirrors and the at least one long lenses of the symmetrically arranged scanning optical systems being arranged to be symmetrical to each other with the optical beam deflecting device as the symmetry center, respectively,
• wherein in each of the symmetrically arranged scanning optical systems, a same number of folding-back mirrors is arranged downstream of the at least one respective long lens in a direction in which an optical beam deflected by the optical beam deflecting device travels, and
• wherein the at least one long lens included in one of the symmetrically arranged scanning optical systems is arranged upside down in a scanning plane relative to the at least one long lens included in another one of the symmetrically arranged scanning optical systems.