A polygonal mirror includes reflecting surfaces, a molded member including a first surface and a second surface, a contact portion, and gate marks. Each of said first surface and said second surface has a polygonal shape. The contact portion and the gate marks are formed at non-overlapping positions with a line segment connecting a vertex of the polygonal shape with a rotation center. The gate marks and the reflecting surfaces are the same in number. A perpendicular bisector of a line segment connecting centers of the gate marks adjacent to each other with respect to a rotational direction of the polygonal mirror is formed at a position passing through an associated vertex of the polygonal shape and the rotation center.

An optical device includes a lens mirror array, in which transparent optical elements are connected to each other along a first direction, and a case, in which the lens mirror array is contained and fixed. The case includes at least three holes through which a manufacturing jig can pass. The jig can be used to press the lens mirror array in a direction intersecting the first direction at three or more positions on the lens mirror array to deform the lens mirror array to correct for possible distortions in the optical device prior to the fixing of the lens mirror array to the case.

A rod lens array 10a includes a plurality of gradient-index rod lenses 1b arrayed to have optical axes parallel to each other, and forms an erecting equal-magnification image. The gradient-index rod lenses 1b each have a refractive-index distribution in a radial direction thereof. The refractive-index distribution n(r) is approximated by n(r)=n.sub.0⋅{1-(A/2)⋅r.sup.2}, where a refractive index at a center of the gradient-index rod lens 1b is represented by n.sub.0, a refractive-index distribution constant of the gradient-index rod lens 1b is represented by \A, and a distance from the center of the gradient-index rod lens 1b is represented by r. The gradient-index rod lens 1b has an aperture angle θ of 3 to 6°, the aperture angle θ represented by θ=sin.sup.−1(n.sub.0\A⋅r.sub.0), where a radius of the gradient-index rod lens is represented by r.sub.0. The rod lens array 10a has an imaging distance of 45 to 75 mm and a depth of field of 1.5 to 3.0 mm with value of modulation transfer function (MTF) of 30% or more at a spatial frequency of 6 Ip/mm.

A light deflector includes a rotary polygon mirror and a motor to rotate the rotary polygon mirror. The rotary polygon mirror includes reflecting surfaces to reflect light emitted from a light source and a hole portion provided in a rotational axis direction. The motor includes a shaft portion in the hole portion and a support member supporting the rotary polygon mirror. The support member is fixed to, and coaxial with, the shaft portion, and includes an insertion portion in the hole portion. The rotary polygon mirror includes a protruded portion near the hole portion and protruding from at least one reflecting surface orthogonal to the rotational axis direction. The protruded portion includes a fitting portion fitted to the shaft portion or the support member and in which a portion continued from a hole portion surface is protruded toward the rotation center more than the surface forming the hole portion.

An optical scanning device includes an optical source portion to emit an optical beam; an optical deflector to deflect the optical beam in a main scanning direction; and an imaging lens to image the deflected optical beam onto a light-exposed object. A scanning line curvature caused by a refractive index deviation of the imaging lens is determined, and a curvature of the imaging lens in a sub-scanning direction is determined based on the determined scanning line curvature.

An exposure head configured to expose a photosensitive drum includes: a substrate; a plurality of strip-shaped semiconductor chips each including a plurality of light emitting elements that emit light and a drive circuit that drives the light emitting element, the plurality of semiconductor chips being arranged on the substrate; and a lens array configured to collect light from the light emitting elements on the photosensitive drum. The drive circuit operates between a first potential and a second potential, the light emitting element operates between a third potential and a fourth potential, and a potential difference between the third potential and the fourth potential is equal to or larger than a potential difference between the first potential and the second potential.

A movable member includes a frame, a mounting portion, a rotatable image bearing member, a charging member, and a cleaning member. The cleaning member includes a base portion including a first surface positioned on one side of the frame, a second surface positioned on the other side of the frame, and a third surface, and includes a projected portion. The projected portion includes a first side surface positioned on the aforementioned the other side and a second side surface positioned on the aforementioned one side. The first side surface is positioned between the first surface and the second surface. The first side surface constitutes an end surface of the projected portion on the aforementioned the other side with respect to the axial direction, and the second side surface constitutes an end surface of the projected portion on the aforementioned one side with respect to the axial direction.

An image forming apparatus includes: a photoconductor that rotates about a first axis; an exposure portion that includes a substrate that includes a plurality of light emitting portions for exposing a surface of the photoconductor, and a support portion for supporting the substrate, and that moves between an exposure position where the photoconductor is exposed and a retracted position where the photoconductor is retracted from the exposure position; and a rotational member that has a second axis along the first axis, and that moves the exposure portion between the retracted position and the exposure position by rotation about the second axis.

A scanline curvature correction mechanism includes a holding mechanism to extend in a main scanning direction and hold an optical element in the main scanning direction, a pressing member provided near a center of the optical element in the main scanning direction and press the optical element of the optical scanning device in the sub-scanning direction, and a curvature adjustment mechanism provided on an opposite side of the pressing member with the optical element interposed therebetween and to adjust a curvature of the optical element in the sub-scanning direction. The curvature adjustment mechanism includes an eccentric cam to rotate around a rotation axis parallel to an optical axis of the optical element and include a cam portion of which an outer peripheral surface is eccentric with respect to the rotation axis, and a fixing mechanism to stepwisely fix an angular position of rotation of the eccentric cam.

Alight scanning apparatus according to the present invention includes a deflecting unit configured to deflect a light flux to scan a scanned surface in a main scanning direction, and an imaging optical system configured to guide the light flux deflected by the deflecting unit to the scanned surface and to have different partial magnifications in the main scanning direction between an on-axis image height and an outermost off-axis image height. A ratio of a reflectivity at a first outermost off-axis deflection point on one side with respect to an on-axis deflection point on a deflecting surface of the deflecting unit to that at the on-axis deflection point, and a ratio of the reflectivity at a second outermost off-axis deflection point on the other side with respect to the on-axis deflection point on the deflecting surface to that at the on-axis deflection point are each appropriately set.