Exposure apparatus and image forming apparatus

An exposure apparatus comprising:

• a line head in which a plurality of EL (electroluminescent) elements are aligned;
• and
• a rotatable photosensitive drum, which is exposed by light from the line head,
• wherein the line head includes N (where, “N” is 2 or greater) EL element columns in which the alignment direction of the EL elements is parallel to the rotational axis of the photosensitive drum,
• in each of the EL element columns, the area of a light-emitting pixel of the EL element which emits light is constant within a corresponding column,
• when the column number of the EL element columns is from 1 to N, the area S of the light-emitting pixel of the EL element in each of the columns is Si=S1×2i−1 (where, “i” is the column number of each of the EL element columns and a natural number from 1 to N, and “S1” is the area of the light-emitting pixel of the EL element of a first column), and
• one or a plurality of EL elements selected from N EL elements within the N EL element columns perform exposure on the same unit drawing region on the photosensitive drum,
• wherein the area S of the light-emitting pixel of the EL element, which is necessary to obtain the light amount with a value which is obtained by dividing the light amount necessary to obtain the highest gray-scale level in gray-scale levels indicating the degree of exposure for the unit drawing region of the photosensitive drum by (2N−1) (where, “N” is the number of EL element columns), is set to S1,
• wherein the each EL element column form a group A, and other EL element columns form a group B, which includes the same number of EL element columns as the group A, and in which each of the EL element columns has the same number of EL elements as each of the EL element columns of the group A and a relative location relation between the EL elements is the same as the group A, and
• wherein each EL element column of the group A is spaced from adjacent EL element columns of the group A by a pitch, the EL element columns of the group B being disposed from the EL element columns of group A at positions deviated by half of the pitch.