CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2020-159616 filed Sep. 24, 2020.

BACKGROUND

(i) Technical Field

The present disclosure relates to a light-emitting-device head and an image forming apparatus.

(ii) Related Art

An electrophotographic image forming apparatus, such as a printer; a multifunction machine; or a facsimile, forms an image by applying light representing image information from an optical recording unit to a charged photoconductor to form an electrostatic latent image, visualizing the electrostatic latent image with toner, transferring the visualized image to a recording medium, and fixing the image. Examples of the optical recording unit include a unit employing an optical scanning scheme in which the unit performs exposure by moving laser light of a laser in a first scanning direction. A recent optical recording unit employs a light-emitting-device head in which a number of light emitting devices such as light emitting diodes (LEDs) are arranged in the first scanning direction.

An image forming apparatus disclosed by Japanese Unexamined Patent Application Publication No. 2009-226712 includes LED print heads (LPHs) as light-emitting-device arrangements that are staggered such that exposure areas of adjacent ones of the LPHs overlap in part, whereby dot cores in a dot halftone image obtained through dot halftoning performed by an image processing unit are formed by light emitting devices that are adjacent to each other at the boundary between different light-emitting-device arrangements.

SUMMARY

It is difficult to manufacture a light-emitting-device head in which light emitting devices that are arranged in the first scanning direction are all provided on a single substrate. Therefore, in some cases, a plurality of substrates are arranged in a staggered manner in the first scanning direction while overlapping one another in part in a second scanning direction, and the substrate to be used for light emission is switched at each of the overlapping portions. In such a case, however, the image formed on the recording medium may have a black line or a white line at each of switching positions where the above switching occurs.

Aspects of non-limiting embodiments of the present disclosure relate to a light-emitting-device head and so forth in which an image formed on a recording medium is less likely to have a black line or a white line at each switching position than in a case where the switching position is not varied with the positions of dots.

Aspects of certain non-limiting embodiments of the present disclosure address the above advantages and/or other advantages not described above. However, aspects of the non-limiting embodiments are not required to address the advantages described above, and aspects of the non-limiting embodiments of the present disclosure may not address advantages described above.

According to an aspect of the present disclosure, there is provided a light-emitting-device head including a first light-emitting-device arrangement including light emitting devices arranged in lines extending in a first scanning direction; a second light-emitting-device arrangement including light emitting devices arranged in lines extending in a first scanning direction, the second light-emitting-device arrangement overlapping the first light-emitting-device arrangement in a second scanning direction at least in part; an optical device that forms an electrostatic latent image by focusing light emitted from the light emitting devices on a photoconductor and exposing the photoconductor to the light; and a switching unit that switches the light-emitting-device arrangement to be lit up between the first light-emitting-device arrangement and the second light-emitting-device arrangement at a switching position defined at any position in an overlapping portion where the first light-emitting-device arrangement and the second light-emitting-device arrangement overlap each other. The electrostatic latent image is composed of dots formed by a screening process performed with a screen having a predetermined screen angle. The switching unit defines the switching position such that when points in the electrostatic latent image that coincide with the switching position are connected to one another by a line, the line forms a zigzag shape while overlapping some of the dots, the zigzag shape including a line segment extending at the screen angle.

