Exposure device, image forming apparatus and computer readable medium storing program for exposure control

1. An exposure device comprising:

a plurality of light emitting elements that light in turn for exposure;

a plurality of driving elements that drive each of the light emitting elements; and

a time changing member that changes one time period of a switching signal to switch light emitting elements driven by the driving elements among the plurality of light emitting elements in turn from a reference time, depending on an image forming speed, such that an idle period between lighting/transmission periods of the plurality of light emitting elements is substantially the same at respective image forming speeds,

wherein the time changing member changes the one time period from the reference time for some of the light emitting elements during one main scan, and maintains the one time period as the reference time for the remaining light emitting elements.

2. The exposure device according to claim 1 ,

wherein, if there are a plurality of light emitting elements to change the one time period from the reference time during one main scan, the time changing member places the light emitting elements to maintain the one time period as the reference time between the plurality of light emitting elements.

3. The exposure device according to claim 1 ,

wherein the time changing member changes the light emitting elements to change the one time period from the reference time during one main scan every main scan line.

4. The exposure device according to claim 1 ,

wherein the time changing member maintains the one time period from the reference time when the image forming speed is at a given speed, and

wherein if the image forming speed is slower than the given speed, then the time changing member lengthens the one time period from the reference time for some of the light emitting elements during one main scan and maintains the one time period as the reference time for remaining light emitting elements, in order to keep the idle period at a target value.

5. An image forming apparatus comprising:

a photoconductor;

an exposure device that forms a latent image on the photoconductor; and

a developing unit that develops the latent image,

wherein the exposure device includes:

a plurality of light emitting elements that light in turn for exposure;

a plurality of driving elements that drive each of the light emitting elements; and

a time changing member that changes one time period of a switching signal to switch light emitting elements driven by the driving elements among the plurality of light emitting elements in turn from a reference time, depending on an image forming speed, such that an idle period between lighting/transmission periods of the plurality of light emitting elements is substantially the same at respective image forming speeds, and

wherein the time changing member changes the one time period from the reference time for some of the light emitting elements during one main scan, and maintains the one time period as the reference time for the remaining light emitting elements.

6. A computer readable medium storing a program causing a computer to execute a process for exposure control of an exposure device, the process comprising:

controlling the exposure device including:

a plurality of light emitting elements that light in turn for exposure;

a plurality of driving elements that drive each of the light emitting elements; and

a time changing member that changes one time period of a switching signal to switch light emitting elements driven by the driving elements among the plurality of light emitting elements in turn from a reference time, depending on an image forming speed, such that an idle period between lighting/transmission periods of the plurality of light emitting elements is substantially the same at respective image forming speeds, and

changing the one time period from the reference time for some of the light emitting elements during one main scan by the time changing member with maintaining the one time period as the reference time for the remaining light emitting elements.