Image writing device, image forming apparatus, and image writing method

An image writing method of writing an image on a surface of an image bearer that moves in a sub-scanning direction at a predetermined speed by repeatedly exposing the surface of the image bearer along a main-scanning direction perpendicular to the sub-scanning direction during an image forming period with an exposure head having a plurality of light-emitting elements arranged in the main-scanning direction in a plane extending along the surface of the image bearer, the image writing method comprising:

• detecting a change in a moving speed in the sub-scanning direction of the surface of the image bearer;
• generating a first signal having a constant period shorter than a period corresponding to a writing resolution in the sub-scanning direction;
• generating, in synchronization with the first signal, an image forming period signal specifying the image forming period;
• generating, with a signal generation circuit;
• a second signal having a period based on the period corresponding to the writing resolution in the sub-scanning direction and adjusted to reduce the effect of the detected change in the moving speed, the second signal initially appearing in the image forming period being in synchronization with the first signal;
• and
• generating, in synchronization with the second signal, a line synchronization signal specifying timing of the exposure during the image forming period.

An image writing device comprising:

• at least one exposure device including an exposure head having a plurality of light-emitting elements arranged in a main-scanning direction perpendicular to a sub-scanning direction in a plane extending along a surface of at least one image bearer that moves in the sub-scanning direction at a predetermined speed, the at least one exposure device using the exposure head to repeatedly expose the surface of the at least one image bearer along the main-scanning direction during an image forming period to write an image on the surface of the at least one image bearer;
• means for detecting a change in a moving speed in the sub-scanning direction of the surface of the at least one image bearer;
• means for generating a first signal having a constant period shorter than a period corresponding to a writing resolution in the sub-scanning direction;
• means for generating, in synchronization with the first signal, an image forming period signal specifying the image forming period;
• means for generating a second signal having a period based on the period corresponding to the writing resolution in the sub-scanning direction and adjusted to reduce the effect of the detected change in the moving speed, the second signal initially appearing in the image forming period being in synchronization with the first signal;
• and
• means for generating, in synchronization with the second signal, a line synchronization signal specifying timing of the exposure during the image forming period.