Patent ID: 8248672

Claim:
An image writing unit, comprising: a plurality of light emitting device array units each having a light emitting device array in which a plurality of light emitting devices are arranged in one direction, wherein a length of each light emitting device array unit is shorter than a length of the photosensitive body in a main scan direction; and a control part configured to use a transformation pattern to transform, in a density transformation mode, image data for each matrix of n by n pixels, wherein, a rate of writing an image in a sub-scan direction is multiplied by m, and a pixel density of image data written on the photosensitive body is multiplied by (2B+1)/2 in the main scan direction, and multiplied by m(2B+1)/2 in the sub-scan direction, where n denotes a positive integer, m denotes a positive integer and B denotes a positive integer, wherein: in the density transformation mode, a transformation pattern which is selected according to a position along the main scan direction at which an image is written with respect to a position of each of the plurality of light emitting device array units, is used to transform image data.