Abstract: An imaging optical system includes, sequentially from an object side toward an image side, a first lens group; an aperture stop; and a second lens group. The first lens group includes a negative lens; and a positive lens formed of a plastic lens. The second lens group includes a plastic lens and satisfies Conditional Expressions (1) and (2) as follows: c31a>c32a, and??(1) c31b<c32b,??(2) where c31a is an on-axis curvature of an object-side surface of the plastic lens of the second lens group, c32a is an on-axis curvature of an image-side surface of the plastic lens of the second lens group, c31b is an off-axis curvature of the object-side surface of the plastic lens of the second lens group, and c32b is an off-axis curvature of the image-side surface of the plastic lens of the second lens group.

Abstract: An image-capturing optical system includes an aperture stop; a first lens group closer to an object than the aperture stop and composed of multiple glass lenses including a meniscus lens having a negative power closest to the object within the first lens group, and a second lens group closer to an image than the aperture stop. The second lens group includes a first plastic lens, a second plastic lens adjacent to the first plastic lens and closer to the image than the first plastic lens. The second plastic lens has a surface facing the image, in which curvature is positive in vicinity of the optical axis and an absolute value of the curvature increases within a range from the vicinity of the optical axis to an off-axis area of the surface, and a glass lens having positive power closest to the image within the second lens group.

Abstract: An imaging optical system consists of: an aperture stop; a first lens group closer to an object than the aperture stop; and a second lens group closer to an image than the aperture stop. The first lens group consists of: a first lens having a meniscus shape with negative power; and a second lens having a meniscus shape with positive power. The second lens group includes a third lens made of plastic and adjacent to the aperture stop. The third lens has a surface that satisfies a formula below: |c3a?c3b|/|c3a>1 where c3a denotes a local curvature near an optical axis, c3b denotes a local curvature at a height of an outermost end of an effective diameter of the third lens.

Abstract: An imaging optical system includes, sequentially from an object side toward an image side, a first lens group; an aperture stop; and a second lens group. The first lens group includes a negative lens; and a positive lens formed of a plastic lens. The second lens group includes a plastic lens and satisfies Conditional Expressions (1) and (2) as follows: c31a>c32a, and ??(1) c31b<c32b, ??(2) where c31a is an on-axis curvature of an object-side surface of the plastic lens of the second lens group, c32a is an on-axis curvature of an image-side surface of the plastic lens of the second lens group, c31b is an off-axis curvature of the object-side surface of the plastic lens of the second lens group, and c32b is an off-axis curvature of the image-side surface of the plastic lens of the second lens group.

Abstract: An optical scanning device includes plural light sources, a light deflector including a deflecting-reflecting surface, and a scanning optical system including plural folding mirrors and plural scanning lenses, wherein the plural scanning lenses have the same shape, at least one of an optical surface at the incidence side and an optical surface at the emission side has an asymmetric shape with respect to a sub-scanning direction, and has an asymmetric shape in the sub-scanning direction with respect to the main scanning direction, and a difference in a number of folding mirrors disposed between the corresponding scanning lens and the light deflector between light incident on the light deflector from a direction inclined to one side relative to a virtual surface including a normal line of the deflecting-reflecting surface and light incident on the light deflector from a direction inclined to the other side is an odd number.

Abstract: An optical scanning unit includes a rotatable multi-faceted mirror having a plurality of faces reflecting light flux emitted from a light source to scan a scanning area in a main scanning direction. A width of the light flux striking the rotatable multi-faceted mirror is smaller than a length of a face of the rotatable multi-faceted mirror. The entire of light flux striking the rotatable multi-faceted mirror is reflected at a first face when the light flux reflected by the rotatable multi-faceted mirror is directed to the center portion of the scanning area. A part of the light flux striking the rotatable multi-faceted mirror is reflected at the first face while the remaining of the light flux is reflected at a second face when the light flux reflected by the rotatable multi-faceted mirror is directed to a least one of the two end portions of the scanning area.

Abstract: An optical scanning unit includes a rotatable multi-faceted mirror having a plurality of faces reflecting light flux emitted from a light source to scan a scanning area in a main scanning direction. A width of the light flux striking the rotatable multi-faceted mirror is smaller than a length of a face of the rotatable multi-faceted mirror. The entire of light flux striking the rotatable multi-faceted mirror is reflected at a first face when the light flux reflected by the rotatable multi-faceted mirror is directed to the center portion of the scanning area. A part of the light flux striking the rotatable multi-faceted mirror is reflected at the first face while the remaining of the light flux is reflected at a second face when the light flux reflected by the rotatable multi-faceted mirror is directed to a least one of the two end portions of the scanning area.

Abstract: An optical scanning device including a light source and a rotating polygon mirror having a plurality of reflective surfaces scans a scan area of a surface in a main scanning direction with the light flux emitted from the light source and reflected by the rotating polygon mirror. All the light flux is reflected by a first reflective surface when light flux deflected by the rotating polygon mirror is directed onto a center position of the scan area, and a part of the light flux incident to the rotating polygon mirror is reflected by a second reflective surface adjacent to the first reflective surface when light flux reflected by the rotating polygon mirror is directed onto at least one end of both ends of the scan area and the light flux obliquely enters a plane perpendicular to a rotation axis of the rotating polygon mirror.

Abstract: An optical scanning unit includes a rotatable multi-faceted mirror having a plurality of faces reflecting light flux emitted from a light source to scan a scanning area in a main scanning direction. A width of the light flux striking the rotatable multi-faceted mirror is smaller than a length of a face of the rotatable multi-faceted mirror. The entire of light flux striking the rotatable multi-faceted mirror is reflected at a first face when the light flux reflected by the rotatable multi-faceted mirror is directed to the center portion of the scanning area. A part of the light flux striking the rotatable multi-faceted mirror is reflected at the first face while the remaining of the light flux is reflected at a second face when the light flux reflected by the rotatable multi-faceted mirror is directed to a least one of the two end portions of the scanning area.

Abstract: An optical scanning device includes: a common optical deflector that deflects light beams from light source devices; and a scanning optical system that focuses the deflected light beams on different scanning surfaces. All the light beams from the light source devices are incident on the optical deflector in directions oblique to a normal line of the scanning surfaces in a main-scanning cross section and to a normal line of a deflecting reflection plane of the optical deflector in a sub-scanning cross section. The scanning optical system includes individual lenses which are individually arranged for the respective light beams and have a plane shape symmetric in the main-scanning direction and satisfies a predetermined condition, and an optical axis of the individual lens is arranged obliquely to the normal line of the scanning surface in the main-scanning cross section so as to satisfy a predetermined condition.

Abstract: An optical scanning device includes plural light sources, a light deflector including a deflecting-reflecting surface, and a scanning optical system including plural folding mirrors and plural scanning lenses, wherein the plural scanning lenses have the same shape, at least one of an optical surface at the incidence side and an optical surface at the emission side has an asymmetric shape with respect to a sub-scanning direction, and has an asymmetric shape in the sub-scanning direction with respect to the main scanning direction, and a difference in a number of folding mirrors disposed between the corresponding scanning lens and the light deflector between light incident on the light deflector from a direction inclined to one side relative to a virtual surface including a normal line of the deflecting-reflecting surface and light incident on the light deflector from a direction inclined to the other side is an odd number.

Abstract: An optical scanning device includes: a common optical deflector that deflects light beams from light source devices; and a scanning optical system that focuses the deflected light beams on different scanning surfaces. All the light beams from the light source devices are incident on the optical deflector in directions oblique to a normal line of the scanning surfaces in a main-scanning cross section and to a normal line of a deflecting reflection plane of the optical deflector in a sub-scanning cross section. The scanning optical system includes individual lenses which are individually arranged for the respective light beams and have a plane shape symmetric in the main-scanning direction and satisfies a predetermined condition, and an optical axis of the individual lens is arranged obliquely to the normal line of the scanning surface in the main-scanning cross section so as to satisfy a predetermined condition.

Abstract: An optical scanning unit includes a rotatable multi-faceted mirror having a plurality of faces reflecting light flux emitted from a light source to scan a scanning area in a main scanning direction. A width of the light flux striking the rotatable multi-faceted mirror is smaller than a length of a face of the rotatable multi-faceted mirror. The entire of light flux striking the rotatable multi-faceted mirror is reflected at a first face when the light flux reflected by the rotatable multi-faceted mirror is directed to the center portion of the scanning area. A part of the light flux striking the rotatable multi-faceted mirror is reflected at the first face while the remaining of the light flux is reflected at a second face when the light flux reflected by the rotatable multi-faceted mirror is directed to a least one of the two end portions of the scanning area.

Abstract: An optical scanning unit includes a rotatable multi-faceted mirror having a plurality of faces reflecting light flux emitted from a light source to scan a scanning area in a main scanning direction. A width of the light flux striking the rotatable multi-faceted mirror is smaller than a length of a face of the rotatable multi-faceted mirror. The entire of light flux striking the rotatable multi-faceted mirror is reflected at a first face when the light flux reflected by the rotatable multi-faceted mirror is directed to the center portion of the scanning area. A part of the light flux striking the rotatable multi-faceted mirror is reflected at the first face while the remaining of the light flux is reflected at a second face when the light flux reflected by the rotatable multi-faceted mirror is directed to a least one of the two end portions of the scanning area.

Abstract: An optical scanning apparatus includes a light source; and a rotational polygon mirror having N reflecting surfaces, the rotational polygon mirror being configured to reflect a light flux emitted from the light source so that a scanning surface is scanned along a main-scanning direction with reflected from the rotational polygon mirror. A width of the light flux incident on the rotational polygon mirror in a direction corresponding to the main-scanning direction is smaller than a width of each reflecting surface of the rotational polygon mirror in the direction corresponding to the main-scanning direction.

Abstract: An optical scanning device including a light source and a rotating polygon mirror having a plurality of reflective surfaces scans a scan area of a surface in a main scanning direction with the light flux emitted from the light source and reflected by the rotating polygon mirror. All the light flux is reflected by a first reflective surface when light flux deflected by the rotating polygon mirror is directed onto a center position of the scan area, and a part of the light flux incident to the rotating polygon mirror is reflected by a second reflective surface adjacent to the first reflective surface when light flux reflected by the rotating polygon mirror is directed onto at least one end of both ends of the scan area and the light flux obliquely enters a plane perpendicular to a rotation axis of the rotating polygon mirror.

Abstract: An optical scanning apparatus includes a light source; and a rotational polygon mirror having N reflecting surfaces, the rotational polygon mirror being configured to reflect a light flux emitted from the light source so that a scanning surface is scanned along a main-scanning direction with reflected from the rotational polygon mirror. A width of the light flux incident on the rotational polygon mirror in a direction corresponding to the main-scanning direction is smaller than a width of each reflecting surface of the rotational polygon mirror in the direction corresponding to the main-scanning direction.

Abstract: An optical scanning unit includes a rotatable multi-faceted mirror having a plurality of faces reflecting light flux emitted from a light source to scan a scanning area in a main scanning direction. A width of the light flux striking the rotatable multi-faceted mirror is smaller than a length of a face of the rotatable multi-faceted mirror. The entire of light flux striking the rotatable multi-faceted mirror is reflected at a first face when the light flux reflected by the rotatable multi-faceted mirror is directed to the center portion of the scanning area. A part of the light flux striking the rotatable multi-faceted mirror is reflected at the first face while the remaining of the light flux is reflected at a second face when the light flux reflected by the rotatable multi-faceted mirror is directed to a least one of the two end portions of the scanning area.