Lens array unit, erecting equal-magnification lens array, optical scanning unit, image reading device, and image writing device

An erecting equal-magnification lens array comprising:

• a first lens array plate in which a plurality of first lenses are provided in the main scanning direction;
• a second lens array plate in which a plurality of second lenses are provided on one surface of the plate in the main scanning direction, and a plurality of third lenses are provided on the other surface in the main scanning direction;
• a third lens array plate in which a plurality of fourth lenses are provided in the main scanning direction;
• a first light shielding member provided with a plurality of first through holes corresponding to the first and second lenses and including a first light shielding member piece and a second light shielding member piece produced by splitting the first light shielding member by a plane through both open ends of the plurality of first through holes;
• and
• a second light shielding member provided with a plurality of second through holes corresponding to the third and fourth lenses and including a third light shielding member piece and a fourth light shielding member piece produced by splitting the second light shielding member by a plane through both open ends of the plurality of second through holes,
• wherein the first lens array plate and the first light shielding member are formed as one piece,
• wherein one end of the first lens array plate in the sub-scanning direction is joined to one end of the first light shielding member piece in the sub-scanning direction, and the other end of the first lens array plate in the sub-scanning direction is joined to one end of the second light shielding member piece in the sub-scanning direction,
• wherein the lens array is built by bending joints joining the first lens array plate and the first and second light shielding member pieces such that the first lens is located to directly face one opening of the first through hole,
• wherein the third lens array plate and the second light shielding member are formed as one piece,
• wherein one end of the third lens array plate in the sub-scanning direction is joined to one end of the third light shielding member piece in the sub-scanning direction, and the other end of the third lens array plate in the sub-scanning direction is joined to one end of the fourth light shielding member piece in the sub-scanning direction,
• wherein the lens array is built by bending joints joining the third lens array plate and the third and fourth light shielding member pieces such that the fourth lens is located to directly face one opening of the second through hole, and
• wherein the first, second, and third lens array plates are stacked such that the second lens is located to directly face the other opening of the first through hole and the third lens is located to directly face the other opening of the second through hole.

A lens array unit comprising:

• a first lens array plate in which a plurality of first lenses are provided in the main scanning direction;
• a second lens array plate in which a plurality of second lenses are provided in the main scanning direction;
• and
• a light shielding member provided with a plurality of through holes corresponding to the first and second lenses and including a first light shielding member piece and a second light shielding member piece produced by splitting the light shielding member by a plane intersecting central axes of the plurality of through holes,
• wherein one end of the first lens array plate in the sub-scanning direction is joined to one end of the first light shielding member piece in the sub-scanning direction, the other end of the first light shielding member piece in the sub-scanning direction is joined to one end of the second light shielding member piece in the sub-scanning direction, and the other end of the second light shielding member piece in the sub-scanning direction is joined to one end of the second lens array plate in the sub-scanning direction,
• wherein the first lens array plate, the second lens array plate, the first light shielding member piece, and the second light shielding member piece are formed as one piece, and
• wherein the lens array is built by bending joints joining the first lens array plate, the second lens array plate, the first light shielding member piece, and the second light shielding member piece such that the first lens is located to directly face one opening of the through hole, and the second lens is located to directly face the other opening of the through hole.

An erecting equal-magnification lens array comprising:

• a first lens array plate in which a plurality of first lenses are provided in the main scanning direction;
• a second lens array plate in which a plurality of second lenses are provided on one surface of the plate in the main scanning direction, and a plurality of third lenses are provided on the other surface in the main scanning direction;
• a third lens array plate in which a plurality of fourth lenses are provided in the main scanning direction;
• a first light shielding member provided with a plurality of first through holes corresponding to the first and second lenses and including a first light shielding member piece and a second light shielding member piece produced by splitting the first light shielding member by a plane intersecting central axes of the plurality of first through holes;
• and
• a second light shielding member provided with a plurality of second through holes corresponding to the third and fourth lenses and including a third light shielding member piece and a fourth light shielding member piece produced by splitting the second light shielding member by a plane intersecting central axes of the plurality of second through holes,
• wherein the first lens array plate, the second lens array plate, the third lens array plate, the first light shielding member piece, the second light shielding member piece, the third light shielding member piece, and the fourth light shielding member piece are formed as one piece, and
• wherein one end of the first lens array plate in the sub-scanning direction is joined to one end of the first light shielding member piece in the sub-scanning direction, the other end of the first light shielding member piece in the sub-scanning direction is joined to one end of the second light shielding member piece in the sub-scanning direction, the other end of the second light shielding member piece in the sub-scanning direction is joined to one end of the second lens array plate in the sub-scanning direction, the other end of the second lens array plate in the sub-scanning direction is joined to one end of the third light shielding member piece in the sub-scanning direction, the other end of the third light shielding member piece in the sub-scanning direction is joined to one end of the fourth light shielding member piece in the sub-scanning direction, and the other end of the fourth light shielding member piece in the sub-scanning direction is joined to one end of the third lens array plate in the sub-scanning direction,
• wherein the lens array is built by bending joints joining the first lens array plate, the first light shielding member piece, the second light shielding member piece, the second lens array plate, the third light shielding member piece, the fourth light shielding member piece, and the third lens array plate such that the first lens is located to directly face one opening of the first through hole, the second lens is located to directly face the other opening of the first through hole, the third lens is located to directly face one opening of the second through hole, and the fourth lens is located to directly face the other opening of the second through hole.