Patent ID: 7683922

Claim:
An exposure head, comprising: a first imaging optical system and a second imaging optical system which are arranged in a first direction; a first light emitting element group including plural light emitting elements which emit light to be imaged by the first imaging optical system; and a second light emitting element group including plural light emitting elements which emit light to be imaged by the second imaging optical system, wherein an inter-optical-system distance P 1 in the first direction between the first imaging optical system and the second imaging optical system satisfies the following expression: m 1· L 1+ m 2 ·L 2>2 P 1−( m 1· dp 1+ m 2· dp 2) where m 1 represents an absolute value of the optical magnification of the first imaging optical system, L 1 represents a width in the first direction of the first light emitting element group to be imaged by the first imaging optical system, dp 1 represents a pitch between the light emitting elements in the first direction in the first light emitting element group to be imaged by the first imaging optical system, m 2 represents an absolute value of the optical magnification of the second imaging optical system, L 2 represents a width in the first direction of the second light emitting element group to be imaged by the second imaging optical system, and dp 2 represents a pitch between the light emitting elements in the first direction in the second light emitting element group to be imaged by the second imaging optical system, and the first and the second imaging optical systems are structured such that m 1 <1 and m 2 <1 are satisfied, where m 1 and m 2 are absolute values of the optical magnification of the first and the second imaging optical systems, respectively.