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.

Provided is a light source device including a plurality of light emitting points arranged in matrix within a first cross section parallel to a first direction and a second direction. When light emitting points are projected within a second cross section parallel to first direction and a third direction perpendicular to first cross section, light emitting points have equal intervals between projections adjacent to each other. When light emitting points are projected within a third cross section parallel to second and third directions, light emitting points have equal intervals between projections adjacent to each other. An interval between light emitting points adjacent to each other in a row of matrix, an interval between light emitting points adjacent to each other in a column of matrix, an angle between row and column, an angle between column and first direction, and an angle between row and second direction are appropriately set.

An optical head comprises a substrate on which optical elements are arranged in a main scanning direction, a lens unit that transmits light emitted from the optical elements or light entering the optical elements, and a holder that holds the lens unit. The holder has a sidewall extending in the main scanning direction. The sidewall has a hole at a position facing the lens unit. A fixing member is provided in the hole. The fixing member fixes the lens unit to the sidewall.

An optical member that refracts a light beam to diverge or focus the light beam, includes: at least three pairs of opposing surfaces. Each of the three pairs of opposing surfaces include a lens. Curvatures of the lenses at one side surfaces of the respective three pairs of surfaces are all the same, or curvatures of the lenses at one side surfaces of respective pairs of at least two pairs of the three pairs of surfaces are different from each other, and respective shortest distances between optical axes of the lenses at the one side surfaces of respective pairs of the at least two pairs of surfaces, and reference sides which are each any one of respective sides surrounding surfaces including the lenses are different from each other.

An optical writing device includes: an image carrier; an exposer that exposes a curved surface of the image carrier; and a control circuit that controls the exposer, wherein the exposer includes a plurality of light-emitting element groups having different positional relationships from one another with the image carrier, and has a configuration that is adjusted in accordance with at least one of an angle at which light reaching the curved surface of the image carrier from each light-emitting element group enters the image carrier, and a distance of each light-emitting element group from the image carrier.

A polygon mirror comprises a resin member including a first surface, a second surface opposite to the first surface, a through-hole extending from the first surface to the second surface, an inner side surface, which intersects with the first and second surfaces, surrounding the through-hole, outer side surfaces, each of which intersects with the first and second surfaces on an opposite side of the inner side surface, and a die piece division line surrounding the through-hole and disposed on the second surface. The second surface intersects with the individual outer side surfaces at intersection lines. The intersection lines include a first intersection line and a second intersection line that intersects with the first intersection line at an intersection, which is a first corner portion. The die piece division line is provided closer to the through-hole than a first midpoint between the inner side surface and the first corner portion.

An optical scanning device (15) includes a reference light guide part (50); a sub-light guide part (40); a reference holding structure (53) which includes a reference reception part (55) configured so as to be in contact with the reference lens (52) deflected in a sub-scanning direction; a sub-holding structure (45) which includes a sub-reception part (45) configured so as to be in contact with the sub-lens (42) deflected in the sub-scanning direction, wherein a deflection direction of the reference lens (52) coincides with a deflection direction of the sub-lens (42), and when it is assumed that the reference lens (52) and the sub-lens (42) are not deflected, an absolute value of a smallest distance between the sub-reception part (45) and the sub-lens (42) is set to be equal to or larger than an absolute value of a smallest distance between the reference reception part (55) and the reference lens (52).

Optical scanner and electrophotographic image forming device are provided. The optical scanner includes a light source; and a first optical unit, a deflection apparatus, and an f-θ lens, which are sequentially arranged along a primary optical axis direction of a light beam emitted from the light source. The light beam emitted from the light source is focused onto a scanning target surface after sequentially passing through the first optical unit, the deflection apparatus, and the f-θ lens. Optical scanning directions of the light beam emitted from the light source include a primary scanning direction and a secondary scanning direction which are perpendicular to each other, and along the primary scanning direction, the f-θ lens satisfies following expressions: SAG1>0, SAG2>0, and 0<(SAG1+SAG2)/d<0.8.

A detection apparatus includes an image sensing device having an image sensing plane including a first periodic structure; and an optical system configured to illuminate a detection target including a second periodic structure different from the first periodic structure, and form an image of light from the detection target on the image sensing plane. Light having entered the image sensing plane generates a plurality of diffracted light beams of different orders in accordance with the first periodic structure. A normal of the image sensing plane is tilted with respect to an optical axis of the optical system such that the optical axis is located between diffracted light beams of adjacent orders not less than a first order among the plurality of diffracted light beams.

An optical head comprises a substrate on which optical elements are arranged in a main scanning direction, a lens unit that transmits light emitted from the optical elements or light entering the optical elements, and a holder that holds the lens unit. The holder has a sidewall extending in the main scanning direction. The sidewall has a hole at a position facing the lens unit. A fixing member is provided in the hole. The fixing member fixes the lens unit to the sidewall.