Line Head, An Exposure Method Using The Line Head, An Image Forming Apparatus, An Image Forming Method And A Line Head Adjustment Method

A line head adjustment method, comprising:

• arranging an element substrate that includes a plurality of luminous elements grouped into luminous element groups, in each of which group two or more luminous elements are arranged in point symmetry,
• obtaining a position of a symmetry center of each luminous element group of the element substrate,
• arranging a lens array, which includes lenses which have an optical property of inverting or non-unity-magnification, focus light from the luminous element groups, and are provided corresponding to the respective luminous element groups, to face the element substrate,
• performing an optical axis adjustment process to the luminous element group to adjust the positional relationship of the element substrate and the lens array arranged to face the element substrate, wherein
• a virtual plane perpendicular to the optical axes of the lenses is a virtual perpendicular plane, and
• the optical axis adjustment process is a process for adjusting the positional relationship of the element substrate and the lens array such that an in-plane distance between a projected position of the obtained symmetry center on the virtual perpendicular plane and a projected position of a midpoint of two images on the virtual perpendicular plane satisfies a specified condition, the two images being formed by focusing lights emitted from two luminous elements point-symmetric with respect to the symmetry center by means of the lens.

An exposure method using a line head, comprising:

• exposing an image plane using a line head that includes an element substrate having luminous element groups as groups of a plurality of luminous elements, and a lens array having lenses which have an optical property of inverting or non-unity-magnification, focus light from the luminous element groups to form spot groups on the image plane, and are provided corresponding to the respective luminous element groups, wherein
• the plurality of luminous elements are two-dimensionally arranged in point symmetry in each luminous element group,
• a plurality of spots are formed as the spot group when the respective luminous elements of the luminous element group emit light, and
• an inter-point distance between an intersection of a line extending from a symmetry center of the luminous element group in an optical axis direction of the lens with the image plane and a center of gravity position of the spot group is shorter than a specified distance.

An image forming apparatus, comprising:

• a latent image carrier;
• and
• a line head including an element substrate that has luminous element groups as groups of a plurality of luminous elements, and a lens array that has lenses which have an optical property of inverting or non-unity-magnification, focus light from the luminous element groups to form spot groups on a surface of the latent image carrier, and are provided corresponding to the respective luminous element groups, wherein
• the plurality of luminous elements are arranged in point symmetry in each luminous element group,
• a plurality of spots are formed as the spot group when the respective luminous elements of the luminous element group emit light, and
• an inter-point distance between an intersection of a line extending from a symmetry center of the luminous element group in an optical axis direction of the lens with the surface of the latent image carrier and a center of gravity position of the spot group is shorter than a specified distance.

An image forming method, comprising:

• forming a latent image on a surface of a latent image carrier using a line head that includes an element substrate having luminous element groups as groups of a plurality of luminous elements, and a lens array having lenses which have an optical property of inverting or non-unity-magnification, focus light from the luminous element groups to form spot groups on the surface of the latent image carrier, and are provided corresponding to the respective luminous element groups, wherein
• the plurality of luminous elements are arranged in point symmetry in each luminous element group,
• a plurality of spots are formed as the spot group when the respective luminous elements of the luminous element group emit light, and
• an inter-point distance between an intersection of a line extending from a symmetry center of the luminous element group in an optical axis direction of the lens with the surface of the latent image carrier and a center of gravity position of the spot group is shorter than a specified distance.