Optical scanning device and image forming apparatus using the device

Abstract

An optical scanning device for scanning surfaces of an even number of photoconductors simultaneously includes a rotating deflecting device arranged substantially at a center in a housing to deflect optical beams, and a plurality of scanning optical systems 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 include a plurality of folding-back mirrors and at least one long lens having power in a 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 are arranged to be symmetrical to each other with the rotating deflecting device as the symmetry center, respectively.

1 - 3 . (canceled) 
   
   
       4 . An optical scanning device for scanning surfaces of an even number of photoconductors simultaneously, the optical scanning device comprising:
 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, 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 the scanning optical systems, arranged in a position nearer the rotating deflecting device and in a position farther from the rotating deflecting device, respectively, at either side of the rotating deflecting device, respective of the at least one long lenses are arranged in respective scanning planes reversed relative to each other, and a difference between the scanning optical systems in numbers of the folding-back mirrors arranged downstream of the respective at least one long lenses in directions in which optical beams deflected by the rotating deflecting device travel is 2N−1, wherein N is a natural number.   
   
   
       5 . The optical scanning device according to  claim 4 , wherein the at least one long lens included in each of the plurality of scanning optical systems is a molded article of resin. 
   
   
       6 . The optical scanning device according to  claim 4 , wherein a number of the plurality of folding-back mirrors in each of the plurality of scanning optical systems is equal. 
   
   
       7 . An optical scanning device for scanning surfaces of an even number of photoconductors simultaneously, the optical scanning device comprising:
 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, 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 the symmetrically arranged scanning optical systems distances between respective pluralities of the folding-back mirrors, arranged to be symmetrical to each other, respectively, and distances between reflecting parts of the rotating deflecting device and adjacent folding-back mirrors of the respective pluralities of folding-back mirrors are equal, respectively.   
   
   
       8 . The optical scanning device according to  claim 7 , wherein in the symmetrically arranged scanning optical systems, at least one pair of folding-back mirrors of the respective pluralities of folding-back mirrors, arranged to be symmetrical to each other, are arranged such that angles formed by incident light rays and reflecting light rays at respective surfaces of the at least one pair of folding-back mirrors are equal. 
   
   
       9 . The optical scanning device according to  claim 7 , wherein in the plurality of scanning optical systems, distances from last folding-back mirrors of the respective pluralities of folding-back mirrors, which lastly guide the optical beams deflected by the rotating deflecting device to the surfaces of the even number of photoconductors, respectively, to the surfaces of the even number of photoconductors are equal. 
   
   
       10 . The optical scanning device according to  claim 7 , wherein a number of the plurality of folding-back mirrors in each of the plurality of scanning optical systems is equal. 
   
   
       11 . An optical scanning device for scanning surfaces of an even number of photoconductors simultaneously, the optical scanning device comprising:
 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, 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 scanning optical systems arranged to be symmetrical to each other with the rotating deflecting device as the symmetry center at positions farther from the rotating deflecting device at both sides of the rotating deflecting device, all of the plurality of folding-back mirrors are 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.   
   
   
       12 . The optical scanning device according to  claim 11 , wherein in each of the scanning optical systems arranged to be symmetrical to each other with the rotating deflecting device as the symmetry center at positions nearer the rotating deflecting device at both sides of the rotating deflecting device, one of the plurality of folding-back mirrors is arranged upstream of the at least one respective long lens in a direction in which an optical beam deflected by the rotating deflecting device travels. 
   
   
       13 . The optical scanning device according to  claim 12 , wherein the one of the plurality of folding-back mirrors arranged upstream of the at least one long lens is wider in a short side thereof than others of the plurality of folding-back mirrors. 
   
   
       14 . The optical scanning device according to  claim 11 , wherein a number of the plurality of folding-back mirrors in each of the plurality of scanning optical systems is equal. 
   
   
       15 - 17 . (canceled) 
   
   
       18 . 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, 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 the scanning optical systems, arranged in a position nearer the rotating deflecting device and in a position farther from the rotating deflecting device, respectively, at either side of the rotating deflecting device, respective of the at least one long lenses are arranged in respective scanning planes reversed relative to each other, and a difference between the scanning optical systems in numbers of the folding-back mirrors arranged downstream of the respective at least one long lenses in directions in which optical beams deflected by the rotating deflecting device travel is 2N−1, wherein N is a natural number.   
   
   
       19 . The image forming apparatus according to  claim 18 , wherein the at least one long lens included in each of the plurality of scanning optical systems of the optical scanning device is a molded article of resin. 
   
   
       20 . The image forming apparatus according to  claim 18 , wherein the optical scanning device is configured such that a number of the plurality of folding-back mirrors in each of the plurality of scanning optical systems is equal. 
   
   
       21 . 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, 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 the symmetrically arranged scanning optical systems, distances between respective pluralities of the folding-back mirrors, arranged to be symmetrical to each other, respectively, and distances between reflecting parts of the rotating deflecting device and adjacent folding-back mirrors of the respective pluralities of folding-back mirrors are equal, respectively.   
   
   
       22 . The image forming apparatus according to  claim 21 , wherein in the symmetrically arranged scanning optical systems of the optical scanning device, at least one pair of folding-back mirrors of the respective pluralities of folding-back mirrors, arranged to be symmetrical to each other, are arranged such that angles formed by incident light rays and reflecting light rays at respective surfaces of the at least one pair of folding-back mirrors are equal. 
   
   
       23 . The image forming apparatus according to  claim 21 , wherein the optical scanning device is configured such that in the plurality of scanning optical systems, distances from last folding-back mirrors of the respective pluralities of folding-back mirrors, which lastly guide the optical beams deflected by the rotating deflecting device to the surfaces of the even number of photoconductors, respectively, to the surfaces of the even number of photoconductors are equal. 
   
   
       24 . The image forming apparatus according to  claim 21 , wherein the optical scanning device is configured such that a number of the plurality of folding-back mirrors in each of the plurality of scanning optical systems is equal. 
   
   
       25 . 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, 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 scanning optical systems, arranged to be symmetrical to each other with the rotating deflecting device as the symmetry center at positions farther from the rotating deflecting device at both sides of the rotating deflecting device, all of the plurality of folding-back mirrors are 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.   
   
   
       26 . The image forming apparatus according to  claim 25 , wherein the optical scanning device is configured such that in each of the scanning optical systems arranged to be symmetrical to each other with the rotating deflecting device as the symmetry center at positions nearer the rotating deflecting device at both sides of the rotating deflecting device, one of the plurality of folding-back mirrors is arranged upstream of the respective at least one long lens in a direction in which an optical beam deflected by the rotating deflecting device travels. 
   
   
       27 . The image forming apparatus according to  claim 26 , wherein the one of the plurality of folding-back mirrors arranged upstream of the at least one long lens is wider in a short side thereof than others of the plurality of folding-back mirrors. 
   
   
       28 . The image forming apparatus according to  claim 25 , wherein the optical scanning device is configured such that a number of the plurality of folding-back mirrors in each of the plurality of scanning optical systems is equal. 
   
   
       29 - 31 . (canceled) 
   
   
       32 . 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, 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 the scanning optical systems, arranged in a position nearer the rotating deflecting device and in a position farther from the rotating deflecting device, respectively, at either side of the rotating deflecting device, respective of the at least one long lenses are arranged in respective scanning planes reversed relative to each other, and a difference between the scanning optical systems in numbers of the folding-back mirrors arranged downstream of the respective at least one long lenses in directions in which optical beams deflected by the rotating deflecting device travel is 2N−1, wherein N is a natural number.   
   
   
       33 . The process cartridge according to  claim 32 , wherein the at least one long lens included in each of the plurality of scanning optical systems of the optical scanning device is a molded article of resin. 
   
   
       34 . The process cartridge according to  claim 32 , wherein the optical scanning device is configured such that a number of respective pluralities of folding-back mirrors in each of the plurality of scanning optical systems is equal. 
   
   
       35 . 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 including a plurality of folding-back mirrors and at least one long lens having power in a 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 the symmetrically arranged scanning optical systems, distances between respective pluralities of the folding-back mirrors, arranged to be symmetrical to each other, respectively, and distances between reflecting parts of the rotating deflecting device and adjacent folding-back mirrors of the respective pluralities of folding-back mirrors are equal, respectively.   
   
   
       36 . The process cartridge according to  claim 35 , wherein in the symmetrically arranged scanning optical systems of the optical scanning device, at least one pair of folding-back mirrors of the respective pluralities of folding-back mirrors, arranged to be symmetrical to each other, are arranged such that angles formed by incident light rays and reflecting light rays at respective surfaces of the at least one pair of folding-back mirrors are equal. 
   
   
       37 . The process cartridge according to  claim 35 , wherein the optical scanning device is configured such that in the plurality of scanning optical systems, distances from last folding-back mirrors of the respective pluralities of folding-back mirrors, which guide the optical beams deflected by the rotating deflecting device to the surfaces of the even number of photoconductors, respectively, to the surfaces of the even number of photoconductors are equal. 
   
   
       38 . The process cartridge according to  claim 35 , wherein the optical scanning device is configured such that a number of respective pluralities of folding-back mirrors in each of the plurality of scanning optical systems is equal. 
   
   
       39 . 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 including a plurality of folding-back mirrors and at least one long lens having power in a 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 scanning optical systems, arranged to be symmetrical to each other with the rotating deflecting device as the symmetry center at positions farther from the rotating deflecting device at both sides of the rotating deflecting device, all of the plurality of folding-back mirrors are 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. 
   
   
   
       40 . The process cartridge according to  claim 39 , wherein the optical scanning device is configured such that in each of the scanning optical systems arranged to be symmetrical to each other with the rotating deflecting device as the symmetry center at positions nearer the rotating deflecting device at both sides of the rotating deflecting device, one of the plurality of folding-back mirrors is arranged upstream of the at least one respective long lens in a direction in which an optical beam deflected by the rotating deflecting device travels. 
   
   
       41 . The process cartridge according to  claim 40 , wherein the one of the plurality of folding-back mirrors arranged upstream of the at least one long lens is wider in a short side thereof than others of the plurality of folding-back mirrors. 
   
   
       42 . The process cartridge according to  claim 39 , wherein the optical scanning device is configured such that a number of respective pluralities of folding-back mirrors in each of the plurality of scanning optical systems is equal. 
   
   
       43 - 45 . (canceled) 
   
   
       46 . A method of making an optical scanning device for scanning surfaces of an even number of photoconductors simultaneously, the method comprising:
 arranging a rotatable 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, 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 the scanning optical systems, arranged in a position nearer the rotating deflecting device and in a position farther from the optical beam deflecting device, respectively, at either side of the optical beam deflecting device, respective of the at least one long lenses are arranged in respective scanning planes reversed relative to each other, and a difference between the scanning optical systems in numbers of the folding-back mirrors arranged downstream of the respective at least one long lenses in directions in which optical beams deflected by the optical beam deflecting device travel is 2N−1 wherein N is a natural number.   
   
   
       47 . The method according to  claim 46 , wherein the at least one long lens included in each of the plurality of scanning optical systems is a molded article of resin. 
   
   
       48 . The method according to  claim 46 , wherein a number of respective pluralities of folding-back mirrors in each of the plurality of scanning optical systems is equal. 
   
   
       49 . 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, 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 the symmetrically arranged scanning optical systems, distances between respective pluralities of the folding-back mirrors, arranged to be symmetrical to each other, respectively, and distances between reflecting parts of the optical beam deflecting device and adjacent folding-back mirrors of the respective pluralities of folding-back mirrors are equal, respectively.   
   
   
       50 . The method according to  claim 49 , wherein in the symmetrically arranged scanning optical systems of the optical scanning device, at least one pair of folding-back mirrors of the respective pluralities of folding-back mirrors, arranged to be symmetrical to each other, are arranged such that angles formed by incident light rays and reflecting light rays at respective surfaces of the at least one pair of folding-back mirrors are equal. 
   
   
       51 . The method according to  claim 49 , wherein last folding-back mirrors of the respective pluralities of folding-back mirrors, which lastly guide the optical beams deflected by the optical beam deflector to the surfaces of the even number of photoconductors, respectively, are arranged such that distances from the last folding-back mirrors of the respective pluralities of folding-back mirrors to the surfaces of the even number of photoconductors are equal. 
   
   
       52 . The method according to  claim 49 , wherein a number of respective pluralities of folding-back mirrors in each of the plurality of scanning optical systems is equal. 
   
   
       53 . 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 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, 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 scanning optical systems, arranged to be symmetrical to each other with the optical beam deflecting device as the symmetry center at positions farther from the optical beam deflecting device at both sides of the optical beam deflecting device, all of the plurality of folding-back mirrors are 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.   
   
   
       54 . The method according to  claim 53 , wherein in each of the scanning optical systems arranged to be symmetrical to each other with the optical beam deflecting device as the symmetry center at positions nearer the optical beam deflecting device at both sides of the optical beam deflecting device, one of the plurality of folding-back mirrors is arranged upstream of the at least one respective long lens in a direction in which an optical beam deflected by the optical beam deflecting device travels. 
   
   
       55 . The method according to  claim 54 , wherein the one of the plurality of folding-back mirrors arranged upstream of the at least one long lens is wider in a short side thereof than others of the plurality of folding-back mirrors. 
   
   
       56 . The method according to  claim 53 , wherein a number of respective pluralities of folding-back mirrors in each of the plurality of scanning optical systems is equal.