Patent ID: 7068295

Claim:
An optical writing unit, comprising: a light emitting device array comprising a plurality of light emitting device array chips, each of the light emitting device array chips comprising a plurality of light emitting devices that are arranged at a predetermined interval P; and an image forming device array comprising a plurality of image forming devices, wherein light volume of the light emitting devices is set such that a calculated gradient of an approximated linear regression for exposure areas corresponding to a plurality of the light emitting devices that are selected at a predefined cycle falls within a predetermined range, the predetermined range being defined for an effective image area in its entirety, and the light volume of the light emitting devices that are located closest and next closest to an edge of the light emitting device array chips are set up such that said gradient corresponds to an interval Pa between the light emitting device closest to the edge of one of the light emitting device array chips and the light emitting device closest to the edge of an adjacent one of the light emitting device array chips.