Patent ID: 7952601

Claim:
An exposure head comprising: a lens array in which lenses are disposed in a first direction; a light-emitting element substrate on which light-emitting elements that emit light to be focused by the lenses are disposed in the first direction: and diaphragms disposed between the light-emitting elements and the lenses, wherein the diaphragms are disposed in one-to-one correspondence with the lenses and block a part of light traveling from the light-emitting elements, the lenses focus light through the diaphragms on an image plane disposed in an opposite direction to the light-emitting element substrate, and length L 1 of the lenses in the first direction and length L 2 of the lenses in a second direction orthogonal to the first direction have a relation represented by an expression 1<L 2 /L 1 <1.2.