1. An image forming apparatus, comprising: an exposure head that includes a plurality of imaging optical systems which are arranged in a first direction and a plurality of light emitting elements which emit lights to be imaged by the imaging optical systems; a latent image carrier that moves in a second direction orthogonal to or substantially orthogonal to the first direction and carries a latent image formed by the exposure head; a developer that develops the latent image; and a detector that detects an image developed by the developer, wherein the image detected by the detector has a width in the first direction wider than that of an image formed by one imaging optical system.